Atlas on X-ray and Angiographic Anatomy
Atlas on X-ray and Angiographic Anatomy
Hariqbal Singh MD DMRD
Professor and Head Department of Radiology Shrimati Kashibai Navale Medical College Pune, Maharashtra, India
Parvez Sheik MBBS DMRE
Consultant Radiology Shrimati Kashibai Navale Medical College Pune, Maharashtra, India
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[email protected] This book has been published in good faith that the contents provided by the authors contained herein are original, and is intended for educational purposes only. While every effort is made to ensure accuracy of information, the publisher and the authors specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the contents of this work. If not specifically stated, all figures and tables are courtesy of the authors. Where appropriate, the readers should consult with a specialist or contact the manufacturer of the drug or device. Atlas on X-ray and Angiographic Anatomy First Edition: 2013 ISBN 978-93-5090-432-9 Printed at
Dedicated to Our dear consorts Arvind Hariqbal and Naasiya Musthafa
Saying Anatomy is a nursery offers framework to enter the infirmary, clasp it firmly it will help analyze the pathology rightly with foundation in place all is well the value of radiology cannot be measured it can only be treasured.
–Hariqbal Singh
Preface Human anatomy has not transformed over the years but the advance in imaging has changed the perception of structural details. Thorough understanding of the normal anatomy is an essential prerequisite to precise diagnosis of pathology. Atlas on X-ray and Angiographic Anatomy is loaded with meticulously labeled illustrations. This book is steal a look into the anatomy in an easy and understandable manner. This atlas is meant for undergraduates, residents in orthopedics and radiology, orthopedic surgeons, radiologists, general practitioners and other specialists. It is meant for medical colleges, institutional and departmental libraries and for stand-alone X-ray and orthopedic establishments. They will find the book useful.
Hariqbal Singh Parvez Sheik
Acknowledgments We thank Professor MN Navale, Founder President, Sinhgad Technical Educational Society and Dr Arvind V Bhore, Dean, Shrimati Kashibai Navale Medical College, Pune, Maharashtra, India, for their kind acquiescence in this endeavor. Our special thanks to the consultants Dr Sasane Amol, Roshan Lodha, Santosh Konde, Shishir Zargad, Yasmeen Khan, Shivrudra Shette, Anand Kamat, Varsha Rangankar, Prashant Naik, Abhijit Pawar, Aditi Dongre, Rajlaxmi Sharma, Manisha Hadgaonkar, Subodh Laul, Sumeet Patrikar, Ronaklaxmi, Shrikant Nagare and Vikash Ojha, who have helped in congregation of this imagery and for their indisputable help in assembly of this educational entity. Our special appreciation to the technicians Mritunjoy Srivastava, Premswarup, Sudhir Mane, Sonawane Adinath, Deepak Shinde, Vinod Shinde, Yogesh Kulkarni, Pravin Adlinge, Parameshwar and Amit Nalawade, for their untiring help in retrieving the data. Our gratitude to Sachin Babar, Anna Bansode, Sunanda Jangalagi and Shankar Gopale, for their clerical help. We are grateful to God and mankind who have allowed us to have this wonderful experience. Last but not least, we would like to thank M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, who took keen interest in publishing the book.
Contents 1. Skull
1
2. Spine
13
3. X- ray Chest
28
4. Abdominal Radiograph
34
5. Upper Limb
37
6. Lower Limb
49
7. Angiograms
67
8. Radiological Procedures
103
9. Ossification Centers
127
10. Production of X-rays
133
11. Digital Subtraction Angiography
135
12. Computed and Digital Radiography
137
13. Picture Archiving and Communications System
140
14. Computed Tomography Contrast Media
142
Index
145
1 CHAPTER
INTRODUCTION The term ‘Skull’ includes the mandible, likewise the term ‘Cranium’ is the ‘Skull’ without the mandible (Figs 1.1 and 1.2). The cranial cavity has a roof (cranial vault) and floor (base of the skull). The frontal bone occupies the upper third of the anterior view of the skull; the rest is formed by the maxillae and mandible. The frontal bone extends downwards to form the upper margins of the orbits. Medially the frontal bone articulates with the frontal process of each maxilla. Laterally the frontal bone projects as the zygomatic process to make the frontozygomatic suture with the zygomatic bone at the lateral margin of orbit (Figs 1.3 to 1.6). The frontal bone articulates with the parietal bones at the coronal sutures (which run transversely). The temporal bone consists of five parts– Squamous, mastoid, petrous, tympanic and styloid process. The squamous portion forms part of wall of temporal fossa and gives rise to zygomatic process. The mastoid portion contains the mastoid antrum, in adults it elongates into mastoid process. The mastoid antrum communicates with the remainder of mastoid air cells and with the epitympanum via the aditus ad antrum. The petrous portion is wedge-shaped and lies between the sphenoid bone anteriorly and occipital bone posteriorly. The tympanic portion lies below the squamous part and in front of the
Skull
mastoid process. The styloid portion forms the styloid process. The temporal fossa is the area bounded by the superior temporal line, zygomatic arch and the frontal process of the zygomatic bone. The zygomatic arch is formed by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The zygomatic process of the maxilla articulates with the zygomatic bone. The zygomatic bone forms the bony prominence of the cheek (Figs 1.7 to 1.10). The styloid process is a part of the temporal bone, from its tip the stylohyoid ligament passes to the lesser horn of hyoid bone. At the base of the skull medial to the styloid process the petrous bone is deeply hollowed out to form the jugular fossa with an opening called as jugular foramen through which the internal jugular vein passes. Anterior to the jugular foramen the petrous part of the temporal bone is perforated by the carotid canal, allows the internal carotid artery to pass through it (Fig. 1.11). Between the basiocciput and the body of sphenoid bone lies the foramen lacerum, it allows the small emissary vein and meningeal branch of ascending pharyngeal artery to pass through it. The roof of the infratemporal fossa is pierced medially by the foramen ovale, through which passes the mandibular nerve, lesser petrosal nerve, accessory meningeal artery and emissary veins. The base of the spine of sphenoid is perforated by the foramen spinosum
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A
B
C
D
Figs 1.1A to D: CT scan multiplanar reconstruction images of skull: (A) Frontal view; (B) View from back; (C) Lateral view; (D) View from below
which allows the middle meningeal vessels to pass through it. The stylomastoid foramen lies behind the base of styloid process. Medial to the third molar tooth on either side is the greater palatine, foramen between the horizontal plate
of palatine bone and the palatine process of the maxilla, the greater palatine vessels and nerves pass through it. Behind the greater palatine, there are numerous small openings called the lesser palatine foramina in the pyramidal process of
Skull
A
B Figs 1.2A and B: X-ray skull—AP view
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Atlas on X-ray and Angiographic Anatomy
4
A
B Figs 1.3A and B: X-ray skull—Lateral view
Skull
5
Fig. 1.4: X-ray skull—Mastoid view (Schuller’s view)
Fig. 1.5: X-ray skull—Lateral view (close-up view to show the pituitary fossa)
palatine bone through which the lesser palatine vessels and nerves pass. There are two parietal bones on either side of skull. They are seen better on lateral views of skull and they articulate with the frontal bone anteriorly at the coronal sutures. Posteriorly, the parietal bones articulate with occipital bone and temporal
bone mastoid process at lambdoid suture. The bregma is the area in midline where the coronal sutures and the two parietal bones meet. Behind the bregma, the parietal bones articulate in the midline sagittal suture. This midline sagittal suture ends at the lambda in posteriorly. The lambda is the area posterior where the sagittal suture ends
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Fig. 1.6: X-ray skull—PA view (Caldwell view for paranasal sinuses)
Fig. 1.7: X-ray skull—Water’s view (for paranasal sinuses)
Skull
Fig. 1.8: X-ray skull—Reverse Water’s view
Fig. 1.9: X-ray skull—Towne’s view (30o fronto-occipital view)
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Fig. 1.10: X-ray skull—Submentovertical view
Fig. 1.11: X-ray skull showing base of skull
Skull in midline and the apex of occipital bone reaches out to join it in midline. The mastoid region of the temporal bone articulates with the parietal and occipital bones posteriorly, the mastoid process projects down at the sides. Inferiorly the parietal bones articulate with the squamous portion of temporal bone on either side. The occipital bone on its lower surface has a ridge which is pointing towards the base of the mastoid process; this is called the external occipital protuberance. The basiocciput extends forward from the foramen magnum and fuses with the basis phenoid. The foramen magnum is located in the basilar part of the occipital bone (basiocciput). The pharyngeal tubercle is a slight bony prominence in front of the foramen magnum. One-third of the foramen magnum lies in front and two-thirds behind an imaginary line joining the tips of the mastoid processes. This is contrary to the occipital condyles, where twothirds of the condyles lie in front of this imaginary line. The internal surface of the base of skull is divided into the anterior, middle and posterior cranial fossa. The orbital part of the frontal bone forms a large part of anterior cranial fossa. The anterior cranial fossa extends up to the posterior edge of the lesser wing of sphenoid. The anterior cranial fossa articulates with the cribriform plate medially. The crista galli is a sharp projection of the cribriform plate. The sphenoid bone contributes to the middle cranial fossa. The small midline body of sphenoid bone contains the sella turcica (means ‘Turkish saddle’), a small elevation in front of sella turcica is called tuberculum sellae (Fig. 1.5). The tuberculum sellae has three small spikes, the middle spike is called the middle clinoid process, the two lateral spikes are called anterior clinoid process. At the posterior edge of the sella turcica is an elevation called the dorsum sellae, which has two lateral spikes called the posterior clinoid process. A fibrous portion of the dura forms the roof of the sella turcica extending from
9 the tuberculum sellae to the dorsum sellae and is called the diaphragm sellae. The diaphragm sellae has a central opening to allow the pituitary stalk and vessels to pass through it. The posterior cranial fossa extends from the petrous temporal bone anteriorly to the internal occipital protuberance in the midline. The floor is formed by the foramen magnum, basiocciput and posterior part of sphenoid bone. The dorsum sellae slopes downwards in front of foramen magnum, this slope is called the clivus. The mandible or the jaw bone is a U–shaped, a horizontal central part with two lateral ramus on each side. The posterior border of each ramus has a condyle with a neck which articulates with the temporal bone forming the temporomandibular joint, while the anterior border of each ramus is sharp and is called the coronoid process (Figs 1.1 to 1.4). The temporormandibular joint is a synovial joint between the head (condyle) of the mandible and mandibular fossa on the undersurface of the squamous part of the temporal bone. The joint is separated into the upper and lower cavities by a fibrocartilaginous disc within it. There is no hyaline cartilage within the joint which makes it an atypical synovial joint. The synovial membrane lines the inside of the capsule and the intracapsular posterior aspect of the neck of the mandible. The articular disc is attached around its periphery to the inside of the capsule and to the medial and lateral poles of the head of the mandible. The joint is more stable with the teeth in occlusion than when the jaw is open. The movements at the temporomandibular joint are depression and elevation (opening and closing of the jaws), side to side grinding movements, retraction and protaction movements (retrusion and protrusion). THE NASAL CAVITY AND NASAL SEPTUM The nasal cavity is pear-shaped, broader below and narrower at the top. From its lateral walls the
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conchae project into the nasal cavity. There are three conchae—Superior, middle and inferior conchae. The superior concha is small and is found high in nasal cavity, its lower edge overlies the superior meatus. The sphenoethmoidal recess lies above and behind the superior concha and receives the ostia of sphenoidal sinus. The middle concha lies between the superior and inferior concha. The area in front of the middle meatus is the atrium of nose. Posteriorly, the middle meatus is related to the splenopalatine foramen. The inferior concha lies below the middle concha articulates anteriorly with the maxilla and posteriorly with the palatine bone. The nasal septum (Fig. 1.12) is normally in the midline, it consists of bone (vomer) and cartilage. It has a lower free margin, superiorly it articulates with the medial ends of frontal bone and also the frontal process of maxilla. The two maxillae on either side meet in the midline and project forwards as the anterior nasal spine at the lower margin of the nasal aperture. The vomer articulates with the sphenoid body and forms the posterior border of the septum. The septal cartilage forms the anterosuperior part of the septum. The floor of the nose is formed by the upper surface of the hard palate. The central part of the roof of nose is the cribriform plate of the ethmoid. THE PARANASAL SINUSES The paranasal sinuses all arise as evaginations from the nasal fossa. It comprises of frontal sinuses, maxillary sinuses, sphenoid sinuses and ethmoidal sinuses. The nasal cavity contains the superior meatus, middle meatus and the inferior meatus. The superior meatus drains the posterior ethmoidal air cells and sphenoidal sinuses. The middle meatus drains the frontal sinuses, maxillary sinuses and anterior ethmoidal air cells. The osteomeatal complex comprises of the uncinate process, ethmoid infundibulum, maxillary sinus ostium, middle turbinate, frontal recess and ethmoid bulla. The inferior meatus has opening for the nasolacrimal duct (Figs 1.8 to 1.12).
The maxillary sinus lies in the body of maxilla, the sinus is triangular in shape, the apex in the zygomatic process of maxilla and the base towards the lateral wall of the nose. The roof of the sinus is the floor of the orbit. The floor of the sinus is formed by the alveolar part of maxilla. The infratemporal fossa and pterygopalatine fossa lies behind the posterior wall of maxillary sinus. The ostium of maxillary sinus is on the superomedial aspect of the sinus and opens into the middle meatus on the same side into the nasal cavity (Figs 1.2B and 1.3B). The ethmoidal sinus lies between the nasal cavity and orbit. The sinus is divided by multiple thin bony septa into the anterior and posterior group of ethmoidal air cells. The lateral wall of the ethmoidal sinus forms a part of the medial wall of orbit; it is paper thin and is called the lamina papyracea. The ostia of anterior ethmoidal air cells drain into the middle meatus. The ostia of posterior ethmoidal air cells drain into the superior meatus. The sphenoidal sinus occupies the body of sphenoid bone. A vertical septum divides the cavity into two unequal halves. The roof of sphenoid sinus is formed by pituitary fossa and middle cranial fossa. Laterally the sphenoid sinus is related to the cavernous sinus and internal carotid artery. Posteriorly, the sphenoid sinus is related to the posterior cranial fossa and pons. The ostium of sphenoidal sinus is in the anterior wall of the sinus and opens into the superior meatus or into the sphenoethmoidal recess. The frontal sinuses are formed within the frontal bone on either side near midline. Its floor forms the roof of orbit medially. Posteriorly the frontal sinus is related to anterior cranial fossa. The ostium of frontal sinus is at its lower medial edge and drains into the middle meatus in nasal cavity or in some cases into the anterior ethmoidal air cells. THE ORBIT The bony orbit is a cavity, shaped like a pyramid with its apex posteriorly and the base forming
Skull
11
Fig. 1.12: X-ray skull—Lateral view (for nasal bones)
Fig. 1.13: X-ray skull—AP view in a 2-year-old child
the orbital margins anteriorly. The orbital roof is formed by the frontal bone, which separates the orbit from the anterior cranial fossa. The orbital floor is formed by the orbital plate of the maxilla,
portions of the palatine bone and the zygoma (Figs 1.10, 1.13 and 1.14). The maxillary portion of orbital floor is usually involved in blow out fractures. The medial orbital wall is the thinnest
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Atlas on X-ray and Angiographic Anatomy
Fig. 1.14: X-ray skull—Lateral view in a 2-year-old child
of all the orbital walls and comprises of frontal process of the maxilla, lacrimal bone, lamina papyracea and bony sphenoid. The lateral wall of orbit is formed by the zygoma and greater wing of sphenoid. The superior orbital fissure is a space between the greater and lesser wings of sphenoid. The inferior orbital fissure is formed by the maxilla, the palatine bone and the greater wing of sphenoid. The optic canal lies within the lesser wing of sphenoid, the optic nerve and ophthalmic artery encased in the dural sheath pass through it.
Structures passing through the superior orbital fissure: Superior ophthalmic vein, the rectus muscles (superior, inferior, medial and lateral), lacrimal nerve, frontal nerve, trochlear nerve, oculomotor nerve, abducent nerve, nasociliary nerve. Structures passing through the inferior orbital fissure: Infraorbital artery, inferior ophthalmic vein, zygomatic nerve, infraorbital nerve. Structures passing through the optic canal: Optic nerve, ophthalmic artery.
2 CHAPTER
Two common radiographic views taken for the spine are the AP view and the lateral view. Most disease process involving the vertebral body or the posterior elements can be noted on these views, however, special views like posterior oblique view may be necessary in some cases. The spine is made up of five groups of vertebrae. The portion of spine around the neck region is cervical spine. It is formed by first seven vertebrae which are referred as C1 to C7, followed by 12 thoracic vertebrae referred as T1 to T12 and subsequently five lumbar vertebrae L1 to L5 in the low back area. The sacrum is a big triangular bone at the base, its broad upper part joins the L5 vertebra and its narrow lower part joins the coccyx or tail bone. CERVICAL SPINE It starts with first cervical vertebra (C1) attached to the bottom of the skull, the basiocciput. Atlas is the name given to C1 vertebra as it supports and balances the weight of the skull. It has practically no body or spinous process, it appears as two thickened bony arches which join anteriorly as anterior tubercle and posteriorly as posterior tubercle. These two thickened bony arches join to form a large hole with two transverse processes. On its upper surface, the atlas has two facets
Spine
that unite with the occipital condyles of the skull. Structure of atlas is unique and has a large opening which accommodates spinal cord (Figs 2.1 and 2.2). The second vertebra is the “axis”, it lies directly beneath the atlas vertebra. It bears large bony tooth-like protrusion on its summit, the odontoid process or the dens. This process projects upward and lies in the ring of the atlas. The joints of the axis give the neck its ability to turn from side to side, i.e. left and right, as the head is turned, the atlas pivots around the odontoid process. The odontoid process arises from anterior part of C2 vertebrae and articulates with the C1 vertebrae above to form the atlanto-occipital joint (Figs 2.2, 2.3 and 2.10). Special views may be taken on plain radiographs to demonstrate the atlantoaxial joint and atlanto-occipital joint. The transverse processes of the cervical vertebrae have large transverse foramina to allow the vertebral arteries into the cranium. The spinous processes of the second to fifth cervical vertebrae are forked providing attachments for various muscles. C3-C6 vertebrae have a typical structure. C7 vertebra is called vertebra prominens because of a long prominent thick nearly horizontal not bifurcated spinous process which is palpable from the skin (Figs 2.4 to 2.9).
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14
A
B
C
D
Figs 2.1A to D: (A) Cervical spine MRI sagittal section T2WI; (B) Multiplanar reconstructed CT scan images of cervical spine posterior view; (C) View from above; (D) Lateral view
There are eight cervical spinal nerves and the neural foramina of cervical spine allow the cervical spinal nerves to exit out of the spinal canal. DORSOLUMBAR SPINE It consists of twelve vertebrae in the chest area, the first thoracic vertebra articulates with the C7 vertebra above and the last thoracic vertebra articulates with the first lumbar vertebra below. The thoracic vertebrae are larger in size than those in the cervical region. They have long, pointed spinous processes that slope downward, and have facets on the sides of their bodies that join with ribs. From the third thoracic vertebra onwards to the last thoracic vertebra, the bodies of these bones increases in size gradually (Figs 2.11 to 2.13). This reflects the stress placed on them by the increasing amounts of body weight they bear. There are five “lumbar vertebrae” in the
lower back. They have larger and stronger bodies to provide support. The transverse processes of these vertebrae project backward at sharp angles, while their short, thick spinous processes are directed nearly horizontally. LUMBOSACRAL SPINE The 5 lumbar vertebrae in the lower back are prone to injuries. On AP views the pedicles and transverse process need to be examined to rule out any fracture. On lateral views, the curvature of lumbar spine needs to be examined, note any slipping of one lumbar vertebra over the other. The intervertebral disc spaces should be equal in size (Figs 2.14 to 2.16). Additional views like posterior oblique view may be necessary in some cases. The sacrum is a large triangular bone on AP view at the base of the lower spine. Its broad upper part joins the lowest lumbar vertebrae and its narrow lower part joins the coccyx or “tail
Spine
A
B Figs 2.2A and B: X-ray cervical spine—Lateral view
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Atlas on X-ray and Angiographic Anatomy
Fig. 2.3: X-ray cervical spine—Lateral view for C1-C2 vertebrae
bone” (Fig. 2.17). The sides are connected to the iliac bones (the largest bones forming the pelvis). The sacrum is a strong bone and rarely fractures. The five vertebrae that make up the sacrum are separate in early life, but gradually become fused between the eighteenth and thirtieth years. The spinous processes of these fused bones are represented by a ridge of tubercles. The weight of the body is transmitted to the legs through the pelvic girdle at these joints. COCCYX It is the lowest part of the vertebral column and is attached by ligaments to the margins of the sacral hiatus. It is better viewed on lateral views of sacrum with coccyx (Fig. 2.17). Sometimes bowel gases may obscure a clear picture of coccyx. When a person is sitting, pressure is exerted on the coccyx, and it moves forward, acting like a shock absorber. Sitting down with force may cause the coccyx to be fractured or dislocated. GENERAL FEATURES OF SPINE The vertebral body is shaped like an hourglass, thinner in the center with thicker ends. Outer cortical bone extends above and below the
superior and inferior ends of the vertebrae to form rims. The superior and inferior endplates are contained within these rims of bone. The bodies of adjacent vertebrae are joined on the front surfaces by “anterior ligaments” and on the back by “posterior ligaments”. A longitudinal row of the bodies supports the weight of the head and trunk. Intervertebral discs are found between each vertebra. They are better viewed on lateral radio graphs. Intervertebral discs make up about onethird of the length of the spine and constitute the largest organ in the body without its own blood supply. The discs receive their blood supply through movement. The discs are flat, round structures about a quarter to three quarters of an inch thick with tough outer rings of tissue called the annulus fibrosis that contain a soft, white, jelly-like center called the nucleus pulposus. Flat, circular plates of cartilage connect to the vertebrae above and below each disc. Intervertebral discs separate the vertebrae, and act as shock absorbers for the spine. Projecting from the back of each body of the vertebra are two short rounded stalks called “pedicles”. They form the sides of the “vertebral foramen”. They can be viewed on both AP and
Spine
A
B Figs 2.4A and B: X-ray cervical spine—AP view
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Fig. 2.5: X-ray cervicothoracic junction—AP view
Fig. 2.6: X-ray cervical spine swimmer’s view for cervicothoracic junction
lateral radiographs. Pedicles extend posteriorly from the lateral margin of the dorsal surface of the vertebral body. The laminae are two flattened plates of bone extending medially from the pedicles to form
the posterior wall of the vertebral foramen. These laminae are better seen on lateral views on radiographs. They fuse posteriorly in the midline to become spinous process. The pars interarticularis is a special region of the lamina
Spine
Fig. 2.7: X-ray cervical spine right posterior oblique for intervertebral foramina
Fig. 2.8: X-ray cervical spine—Lateral view in flexion
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Fig. 2.9: X-ray cervical spine—Lateral view in extension
Fig. 2.10: X-ray cervical spine open mouth view for atlantoaxial junction
between the superior and inferior articular processes. A fracture or congenital anomaly of the pars may result in a spondylolisthesis. The pedicles, laminae, and spinous process together complete a bony vertebral arch around the vertebral opening, through which the spinal cord passes. Between the pedicles and laminae
of a typical vertebra is a “transverse process” that projects laterally and toward the back. Various ligaments and muscles are attached to the transverse process. Projecting upward and downward from each vertebral arch are “superior” and “inferior” articulating processes. These processes bear cartilage-covered facets by
Spine
A
B
21
C
Figs 2.11A to C: Multiplanar reconstructed CT scan images of dorsolumbar spine: (A) Posterior view; (B) Anterior view; (C) Lateral view
which each vertebra is joined to the one above and the one below it. These facet joints facilitate smooth gliding movement of one vertebra on another to produce twisting motions and rotation of the spine. Facet joints are also called as zygapophyseal joints. On the surfaces of the vertebral pedicles are notches that align to create openings, called “intervertebral foramina”. These openings provide passageways for spinal nerves that exit out of the spinal cord. SPINAL CANAL AND SPINAL CORD The spinal canal is bounded anteriorly by the vertebral bodies, the intervertebral discs,
posterior longitudinal ligament. Posteriorly it is related to the lamina and ligamentum flavum. Laterally on either side, it is related to the pedicles. The intervertebral foramina contain the spinal nerves, posterior root ganglia, spinal arteries and veins. The vertebral canal contains the spinal cord. The spinal canal encases the spinal cord. The bones and ligaments of the spinal column are aligned in such a manner to create a column that provides protection and support for the spinal cord. The outermost layer that surrounds the spinal cord is the dura mater, which is a tough membrane that encloses the spinal cord and prevents cerebrospinal fluid from leaking out. The space between the dura and the spinal canal is called the epidural space. This
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A
B Figs 2.12A and B: X-ray dorsolumbar spine—Lateral view
Spine
23
A
B Figs 2.13A and B: X-ray dorsolumbar spine—AP view
space is filled with tissue, vessels and large veins. Up to the third month of fetal life, the spinal cord is about the same length as the canal. The growth of the canal outpaces that of the cord from the 3rd month onwards. In an adult the lower end of the spinal cord usually ends at approximately the first lumbar vertebra, where it divides into many
individual nerve roots that travel to the lower body and legs. This collection of group of nerve roots is called the “cauda equina”. MRI spine is the modality of choice to examine the spinal canal and spinal cord. CT spine is preferred in cases of acute trauma and those who cannot undergo MRI studies.
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C
A
B
D
Figs 2.14A to D: Multiplanar reconstruction CT scan images of lumbosacral spine: (A) Posterior view; (B) Lateral view; (C) Lateral view showing the intervertebral neural foramina; (D) Oblique view
SOME DIFFERENTIATING FEATURES BETWEEN CERVICAL, THORACIC AND LUMBAR VERTEBRAE C3-C6 vertebrae have atypical features. The body of these four vertebrae is small and broader from side-to-side than from front-to-back. The pedicles are directed laterally and backward. The laminae are narrow, and thinner above than below. The vertebral foramen is large and has triangular shape. The spinous process is short and bifid. Superior articular facets face backward, upward, and slightly medially and inferior face forward, downward, and slightly laterally. The foramen transversarium is an opening in the transverse processes of the seven cervical vertebrae. It gives passage to the vertebral artery, vein and plexus of sympathetic nerves in each of the vertebrae except the seventh, which lacks the artery. C7 has enlarged spinous process called the vertebral prominence.
The thoracic vertebrae have costal facets for ribs on either sides of the vertebral body. They increase in size gradually from T3 vertebra downwards. The lumbar vertebrae have neither a foramen in transverse process nor costal facets; they are larger than the dorsal and cervical vertebrae in size. RADIOLOGICAL IMPORTANCE OF VERTEBRAL COLUMN IN SPINAL INJURIES The vertebral column can be sub divided as anterior column, middle column and the posterior column. Injuries involving the middle and posterior columns result in unstable injuries. • Anterior column is formed by anterior longi tudinal ligament, anterior annulus fibrosus and anterior part of vertebral body. • Middle column is formed by posterior longi tudinal ligament, posterior annulus fibrosus and posterior part of vertebral body.
Spine
A
B Figs 2.15A and B: Lumbosacral spine X-ray—AP view
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A
B Figs 2.16A and B: Lumbosacral spine X-ray—Lateral view
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Fig. 2.17: Sacrum and coccyx X-ray—Lateral view
• Posterior column includes posterior elements and ligaments. RADIOLOGICAL IMPORTANCE OF CRANIOVERTEBRAL JUNCTION Chamberlain line is the line between posterior part of hard palate and posterior margin of
foramen magnum. Normally the tip of odontoid process lies at or below this line. Basilar line is the line along the clivus and it usually falls tangent to the posterior aspect of the tip of odontoid. Craniovertebral angle (Clivus-canal angle) is angle between basilar line and a line along posterior aspect of odontoid process. If this angle is < 150º, cord compression can occur on the ventral aspect.
3 CHAPTER
X-ray—Chest
When viewing the chest X-ray, check first for the technical factors: • Projection AP or PA view, etc. • Orientation (right or left) • Rotation • Penetration • Degree of inspiration. On posteroanterior (PA) view, the X-ray beam first enters the patient from the back and then passes through the patient to the film that is placed anterior to the patient’s chest. It uses 80-120 kV and focus film distance of 6 feet. On a PA film, lung is divided radiologically into three zones: 1. Upper zone extends from apices to lower border of 2nd rib anteriorly. 2. Middle zone extends from the lower border of 2nd rib anteriorly to lower border of 4th rib anteriorly. 3. Lower zone extends from the lower border of 4th rib anteriorly to lung bases. Please note that radiological division of lung in upper, middle and lower zone does not depict anatomical lobes of the lung. ANATOMICAL SEGMENTAL DIVISION OF LUNGS Right lung has three lobes: 1. Upper lobe which has an apical, anterior and a posterior segment.
2. Middle lobe has a lateral and a medial segment. 3. Lower lobe has superior segment, medial basal segment, anterior basal segment, lateral basal segment and a posterior basal segment. Left lung has two lobes: 1. Upper lobe which has an apicoposterior, anterior, superior lingular and an inferior lingular segment. 2. Lower lobe has superior segment, anterior basal segment, lateral basal segment and a posterior basal segment. Left lung has no middle lobe. When viewing the chest X-ray PA view look for (Figs 3.1 to 3.4): • Check patient’s name and date • Lung fields • Hilum – Normally left hilum is higher than right hilum • Cardiac shape and borders • Mediastinum • Diaphragm—right diaphragm is higher than left diaphragm • Costophrenic angles should be well-defined and acute • Trachea should be slightly deviated to the right around the aortic knuckle • Look at bones for any lesions and fractures • Look for soft tissue abnormalities • Look at the area under the diaphragm. When viewing the chest X-ray lateral view (Figs 3.5 and 3.6):
X-ray—Chest
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E Figs 3.1A to E: CT scan multiplanar reconstructed (MPR) images of thorax: (A) View from front; (B) Lateral view; (C) View from back; (D) CT scan coronal section of thorax; (E) CT scan axial section of thorax
Fig. 3.2: X-ray chest—PA view
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Fig. 3.3: X-ray chest—PA view mediastinal borders
Fig. 3.4: X-ray chest PA view—Cardiothoracic ratio (Cardiothoracic ratio = a+b c ; Cardiothoracic ratio is estimated from the PA view of chest to calculate the size of heart. It is the ratio between the maximum transverse diameter of heart and the maximum width of thorax above the costophrenic angles. a = Right heart border to midline; b = Left heart border to midline and c = Maximum thoracic diameter above costophrenic angles from inner borders of ribs
X-ray—Chest • Check patient name and date • Identify the diaphragms (gastric air bubble lies under the left hemidiaphragm • Compare the lung fields in retrosternal space, retrocardiac space and supracardiac space, they should all have the same density on the X-ray film • Look carefully at the retrosternal space, a mass in this space will obliterate this space turning it white on the X-ray film • Check the position of horizontal fissure and oblique fissures • Check the density of the hila • Do not forget to carefully examine the vertebral bodies on the chest X-ray lateral view. Lung Fissures They are thickening of the septae in the lung parenchyma. For a fissure to be seen on a radiograph, the X-ray beam has to be tangential to it. The right lung has horizontal and oblique
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fissures while the left lung has only the oblique fissure. The location of these fissures are: • On chest X-ray, PA view the horizontal fissure appears as a faint white line that runs from the midpoint of the right hilum to the anterior chest wall. • On chest X-ray, lateral view the oblique fissure runs obliquely downwards from the D4/D5 vertebral level, crossing the hilum in front and continuing downward direction to end near the anterior 1/3rd of diaphragm. Locating Lesions of the Lungs We need to have both PA and lateral views to locate a lesion on chest X-ray. On PA view locate the lung zone where the lesion lies, also look at the borders of the lesion well-defined/ill-defined/silhouette sign. On lateral view identify the horizontal fissure and oblique fissure. After this is done try to localize the lesion carefully:
Fig. 3.5: X-ray chest—Lateral view
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Fig. 3.6: X-ray chest—Apicogram
Fig. 3.7: X-ray chest—PA view (negative) to visualize bony thorax
X-ray—Chest • Lesion in right lung field – If the lesion lies posterior to the oblique fissure it must lie within the lower lobe, does not matter how high it appears on the PA view. – If the lesion lies anterior to the oblique fissure it may be in the upper or middle lobe. – If the lesion is below the horizontal fissure it is in the middle lobe – If the lesion lies above the horizontal fissure it is in the upper lobe. • Lesion in left lung field – If the lesion is behind the oblique fissure it must be in the lower lobe. – If the lesion is anterior to the oblique fissure then it must be in upper lobe (there is no middle lobe in left lung). IMPORTANT POINTS TO OBSERVE ON CHEST X-RAYS • In a well-centered chest X-ray, medial ends of clavicles are equidistant from vertebral spinous process. Both lung fields are of equal radiolucency. • Both hila are concave outwards. The pulmonary arteries, upper lobe veins and bronchi contribute to the making of hilar shadows (Fig. 3.7). • The normal length of trachea is 10 cm, it is central in position and bifurcates at T4T5 vertebral level. Left atrial enlargement increases the tracheal bifurcation angle (normal is 60° to 75°). An inhaled foreign body is likely to lodge in the right lung due to the fact that the right main bronchus is shorter, straighter and wider than left. • Mediastinum is the space between the lungs. It is divided into a superior and an inferior com partment. Superior compartment consists of the thoracic inlet. Inferior compartment
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has anterior, middle and posterior subcompartments. Retrosternal region is included in the anterior compartment, heart lies in the middle compartment and descending aorta with esophagus and paraspinal region is located in the posterior mediastinal compartment. Thymus is located in the anterior part of superior as well as inferior compartment of mediastinum. • Normal heart shadow is uniformly white with maximum transverse diameter less than half of the maximum transthoracic diameter. Cardiothoracic ratio is estimated from the PA view of chest (Fig. 3.4). It is the ratio between the maximum transverse diameter of the heart and the maximum width of thorax above the costophrenic angles: a = right heart border to midline, b = left heart border to midline, c = maximum thoracic diameter above costophrenic angles from inner borders of ribs. Cardiothoracic ratio = a + b/ c. Thus on chest X-ray PA view the cardiothoracic ratio is less than 1/2 the maximum thoracic diameter, in children this cardiothoracic ratio may be increased. In adults the normal cardiothoracic ratio is 2:1. • Borders of the mediastinum are sharp and distinct (Fig. 3.3). The right heart border is formed by superior vena cava superiorly and right atrium inferiorly, the left heart border is formed by the aortic knuckle superiorly, left atrial appendage and left ventricle inferiorly. • The right ventricle lies anteriorly, posterior to the sternum and the right atrium lies on the right lateral side. The left ventricle lies on the entire left side, the outlet of the left ventricle and the ascending aorta lie in the center of the heart. The left atrium is the most posterior chamber of the heart. The inferior vena cava is seen further caudally just at the section the diaphragm appears together with the upper part of liver.
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Abdominal Radiograph
The standard projections requested for abdominal radiographs are (Figs 4.1 and 4.2): • Supine • Erect • Lateral decubitus The radiation exposure of an abdominal radiograph is equivalent to 28 chest radiographs. Key to densities in abdominal radiographs: • Black—Gas • White—Calcified structures • Grey—Soft tissues • Darker gray—Fat • Intense white—Metallic objects. Always view the radiograph using a view box. The contrast of outlines of structures depends on the differences between their densities. These differences are less apparent on the abdominal radiograph as most structures are of similar density—Mainly soft tissue. On a routine supine, abdominal radiograph look for the following: • Dark margins outlining the spleen, liver, kidneys, bladder and psoas muscles—This indicates intra-abdominal fat. • Gas in—Body of stomach, descending colon, small intestines. • Fecal matter in cecum gives it a mottled appearance, seen as a mixture of gray densities representing a gas-liquid-solid mixture. • Pelvic phleboliths are small round/oval calcific densities in pelvic cavity
• A dark skinfold across the upper abdomen is normal finding • Check the bony pelvis, spine and visualized ribs • The heart shadow should be on the left side above the diaphragm • Check whether the right ‘R’ marker is placed on the right side of the abdominal radiograph • Make sure that the abdominal radiograph covers both the hemidiaphragms to the inguinal canal regions • Check the lung bases. On an erect abdominal radiograph the following changes occurs: • The air rises • Fluid goes down due to gravity • The transverse colon, small bowel loops and kidneys drop down a bit lower due to gravity • A slight increase in radiographic density in lower abdomen • The lung bases appear clearer as the diaphragms move down a little • The liver and spleen become more visible. The abdominal radiograph is most helpful in cases of acute abdomen. A normal initial abdominal radiograph does not exclude intraabdominal trauma, follow up radiographs, ultrasound, CT scan and MRI (Figs 4.1A to E) may be necessary. Abnormal air-fluid levels become easier to visualize on erect abdominal radiographs. Gas under diaphragm is seen in
Abdominal Radiograph cases of perforated viscus. Also remember not to waste any time if the patient’s condition is critical, stabilize the patient and shift the patient to operating theater if needed. Radiation exposure in early pregnancy can be disastrous. It is always safer in female patients of reproductive age group to check the date of their last menstrual period. Written consent form is needed confirming that the patient is not pregnant/ unlikely to be pregnant at the time of examination. Additional points to note while examining abdominal radiographs: • Maximum diameter of small bowel should not exceed 3 cm and that of large bowel by more than 5 cm in diameter.
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• Cecum is said to be dilated if it measures more than 8 cm. • The haustra of the large bowel extends only a third of the way across the bowel from each side, whereas the valvulae conniventes of the small bowel traverse from wall to wall. • Presence of small amounts of intraluminal gas throughout the gut is normal, but if found in excess may be abnormal. Also absence of bowel gas in one area may indicate bowel pathology. • Presence of extraluminal gas is abnormal (look for it under the diaphragm, in the bowel wall, in biliary system). • Metallic objects may appear as bright densities, so ask for appropriate history of
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Figs 4.1A to E: CT scan (A to C) multiplanar reconstructed images of abdomen: (A) Coronal view; (B) Sagittal view; (C) Axial view; (D) MRI-T2WI coronal section of abdomen; (E) MRI-T2WI axial section of abdomen
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Fig. 4.2: X-ray abdomen—Supine view
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operations, trauma, ingestion of foreign body, therapeutic/diagnostic procedures. Look for nasogastric tube placements, catheters, etc. to mention them in the report. Look for normal calcified structures which can cause diagnostic difficulty—excessive costal cartilage calcification, calcified aortic/ splenic arteries, pelvic phleboliths, calcified mesenteric lymph nodes, etc. Normal liver has a fairly pointed tip, if this tip appears more rounded with displacement of adjacent intra-abdominal structures it is suggestive of hepatomegaly. The spleen is not normally seen on abdominal radiographs, when spleen is enlarged more than 15 cm, it displaces the adjacent intraabdominal organs and becomes more obvious on abdominal radiographs. Normal kidneys extend from the lower margin of 12th dorsal vertebra to the upper margin of
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3rd lumbar vertebra, the left kidney is usually slightly larger in size and slightly higher placed as compared to the right kidney. The outline of kidney visible on abdominal radiograph is due to perinephric fat. An abdominal mass can arise anywhere in abdomen and would produce a dense area with displacement of bowel loops around it, calcification may also occur within it, CT scan maybe required to investigate such masses. A full bladder appears in the pelvic cavity as a smooth rounded mass of uniform density, the outline is due to perivesical fat tissue. Retroperitoneal masses usually obscure or displace the psoas muscle outline on abdominal radiographs. An erect chest radiograph and not abdominal radiograph is the best projection to diagnose a small pneumoperitoneum (gas in the peritoneal cavity).
5 CHAPTER
Upper Limb
SHOULDER JOINT It is a ball and socket joint and can produce a range of movement such as adduction, abduction, extension and flexion. The head of humerus articulates with the shallow glenoid cavity of scapula thus connecting the upper limb to the chest (Figs 5.1A and B). The joint is made more stable by the articular capsule, ligaments, glenoid labrum and the rotator cuff. The labrum is a fibrocartilaginous rim attached
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around the margin of the glenoid cavity. It deepens the articular cavity, cushions and stabilizes the humeral head. The articular capsule completely encircles the joint; it is attached to the circumference of the glenoid cavity beyond the labrum. The ligaments of the glenohumeral joint are coracohumeral ligament and glenohumeral ligament. The rotator cuff surrounds the shoulder joint; it is formed by tendons of four muscles— Supraspinatus, infraspinatus, teres minor, subscapularis and inserts into anatomical neck
B Figs 5.1A and B: (A) Multiplanar reconstructed CT scan image of shoulder joint; (B) MRI-T1WI coronal section of shoulder joint
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and tuberosities of humerus. The rotator interval is the portion of the joint capsule which lies between the supraspinatus and subscapularis tendons. On AP view of shoulder joint (Figs 5.2 and 5.3) the normal acromioclavicular distance is 200 KVP.
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Fig. 10.1: Line diagram shows production of X-rays
Two different interactions give rise to X-rays. An interaction with electron shell produce characteristic X-rays photons, while interaction with atomic nucleus produces Bremsstrahlung X-ray photons. In diagnostic radiology about 85 percent of X-rays arise from Bremsstrahlung radiation and 15 percent from characteristic radiation. X-ray filter made of aluminum absorbs low energy radiation and decreases unnecessary patient exposure and thus improves film contrast.
Grid is made of parallel lead lines with intervening radiolucent material. It absorbs scattered radiation. Cones and collimators restrict field size and decrease scatter. Distance from X-ray tube (focus) to the X-ray film is called focus film distance (FFD). It is 100 cm for usual radiographs of extremities, abdomen and skull. However, for standing radiograph of chest, it is 180 cm (6 ft) so as to reduce the magnification.
11 C H A PT E R
Digital Subtraction Angiography
Digital subtraction angiography (DSA) is a type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a precontrast image or the mask from later images, hence the term ‘digital subtraction angiography’. Digital subtraction angiography (DSA) is primarily used to image blood vessels. It is useful in the diagnosis and treatment of: Arterial and venous occlusions, carotid artery stenosis, pulmonary embolisms, acute limb ischemia, and arterial stenosis, which is particularly useful for potential renal donors in detecting renal artery stenosis, cerebral aneurysms and arteriovenous malformations. In addition to above applications others include carotid and peripheral arteriography, thoracic and abdominal aortography, pulmonary arteriography, and ventriculography. Future applications may include intracerebral and coronary arteriography. DSA provide low-risk out patient screening arteriography. In DSA, a computer is used to subtract an initial image without contrast medium taken directly from the image intensifier from the angiographic images with contrast medium in the blood vessels. The intravenous administration of contrast material permits safe outpatient screening for arterial disease. The bone, softtissue and gas are removed leaving only the
contrast-medium- filled blood vessels in the final subtracted arterial images. DSA requires cooperative patient who can keep still and hold breath, because any type of movement can cause image degradation. Abdominal examinations are performed after an intravenous injection of 20 mg hyoscine butyl bromide to prevent peristalsis in the gastrointestinal tract and thoracic examinations can be done with ECG-triggered gating to prevent cardiac pulsations. Advantages of DSA are both volume and iodine concentration of the nonionic contrast medium used for each run, because of the high contrast resolution of the imaging system in DSA, reduction in the length of the procedure, reduction in the size of the catheters used from 6-8 Fr down to 3-5 Fr, reduction in the number of radiographic film used, reduction in the radiation dose to the patient and angiographic staff. Disadvantage of DSA is the fact that the images it produces are inferior in the quality of their spatial resolution to those produced by conventional film angiography. The magnitude of this difference in image quality has been reduced with technical improvements in DSA systems. In intravenous DSA, the high contrast resolution of the imaging system allows nonionic contrast medium to be injected intravenously in order to produce arterial images in patients with no femoral pulse, large volume of contrast medium is injected rapidly by a pump injector
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through a catheter positioned in the SVC or right atrium. The contrast medium is diluted as it passes through the lungs and into the left side of the heart and systemic circulation, but the images are of good quality. Complication of intravenous DSA are hemorrhage from puncture site, vascular thrombosis, peripheral embolization, aneurysm, local sepsis, injury to local structures, guidewire fracture, and vasovagal reaction, and vascular disorders. For peripheral angiography carbon dioxide digital subtraction angiography can be used as an alternative or adjunct to iodinated contrast in
vascular imaging and interventional procedures. Its unique qualities make it useful in diagnostic as well as therapeutic procedures in arteries and veins. Because of its endogenous gaseous attributes, it is nonallergic, does not affect the kidneys, and can be used in unlimited quantities. Compared with iodinated contrast, the low viscosity of CO2 permits greater sensitivity for arterial hemorrhage and arteriovenous fistulas as well as it is more facile using microcatheters. Certain simple principles must be used with CO2 as a contrast agent. When used appropriately, CO2 is safe and can be useful when iodinated contrast is either not sufficient or is contraindicated.
12 C H A PT E R
Computed and Digital Radiography
Computed Radiography Computed radiography (CR) uses similar equipment as conventional radiography except that in place of a film to create the image, an imaging plate (IP) made of photostimulable phosphor is used. The imaging plate housed in a special cassette is placed under the body part or object to be examined and the X-ray exposure is made. Thereafter, instead of taking an exposed film into a darkroom for developing in chemical tanks or an automatic film processor, the imaging plate is run through a special laser scanner, or CR reader, that reads and digitizes the image. The digital image can then be viewed and enhanced using software that has functions very similar to other con ventional digital image-processing software, such as contrast, brightness, filtration and zoom. The CR imaging plate (IP) contains photo stimulable storage phosphors, which store the radiation level received at each point in local electron energies. When the plate is put through the scanner, the scanning laser beam causes the electrons to relax to lower energy levels, emitting light that is detected by a photomultiplier tube (Fig. 12.1), which is then converted to an electronic signal. The electronic signal is then converted to discrete (digital) values and placed into the image processor pixel map. The signals generated by the photodetector as the plate is being scanned are amplified and digitized by an
analog-to-digital converter (ADC). The spatial resolution of computed radiography is influenced by factors such as the phosphor plate thickness, the readout time and the diameter of the laser beam, which is typically about 100 μm. Imaging plates can theoretically be reused thousands of times if they are handled carefully. An image can be erased by simply exposing the plate to a room-level fluorescent light. Most laser scanners automatically erase the image plate after laser scanning is complete. The imaging plate can then be reused. Reusable phosphor plates are environmentally safe. A fundamental limitation of CR is the time required to read the latent image. Since, the decay time of the phosphor luminescence is ~0.7 μs, typically the readout of a 3,000×3,000 pixel image can takeover half a minute to complete. An improvement can be obtained by line scanning, where a full line of pixels is stimulated and read out simultaneously instead of single pixels. This line-scanning approach requires a linear array of laser light sources, e.g. laser diodes, as well as a linear array of photodetectors as wide as the imaging plate, and gives rise to readout times of less than 10 seconds. Advantages Over Conventional Radiography • No silver-based film or chemicals are required to process film.
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Fig. 12.1: Schematic mechanism of CR system: Imaging plate-coated with photostimulable phosphor (PSP) exposed to X-rays and contains image data. In CR reader, imaging plate is read using red laser beam, which is swept across the plate by a rotating polygonal mirror. The light emitted by imaging plate is converted into electrical signal and used to form image
• Reduced film storage costs because images can be stored digitally. • Computed radiography often requires fewer retakes due to under or over exposure which results in lower overall radiation dose to the patient. • Image acquisition is much faster image previews can be available in less than 15 seconds. • By adjusting image brightness and/or contrast, a wide range of thicknesses may be examined in one exposure, unlike conventional film based radio graphy, which may require a different exposure or multiple film speeds in one exposure to cover wide thickness range in a component. • Images can be enhanced digitally to aid in interpretation. • Images can be stored on disk or transmitted for off-site review. • Ever growing technology makes the CR more affordable than ever today. With chemicals, dark-room storage and staff to organize them, you could own a CR for the same monthly cost while being environmentally conscious, depending upon the size of the radiographic operation.
Digital radiography (DR) is a form of X-ray imaging, where digital X-ray sensors are used instead of tra ditional photographic film (Fig. 12.2). Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also less radiation can be used to produce an image of similar contrast to conventional radiography. Digital radiography is essentially filmless X-ray image capture. In place of X-ray film, a digital image capture device is used to record the X-ray image and make it available as a digital file that can be presented for interpretation. The advantages of DR over film include immediate image preview and availability, a wider dynamic range which makes it more forgiving for over and under exposure as well as the ability to apply special image processing techniques that enhance overall display of the image. DR has the potential to reduce costs associated with processing, managing and storing films. The digital image capture devices include flat panel detectors (FPDs). FPDs are classified in two main categories: 1. Indirect FPDs: Amorphous silicon (a-Si) is the most frequent used FPD in the medical imaging industry today. Combining a-Si detectors with a scintillator in the detector’s outer layer, which is made from Cesium Iodide (CsI) or Gadolinium Oxysulfide (Gd2O2S), converts X-ray to light. Because the X-ray energy is converted to light, the a-Si detector is considered an indirect image capture technology. The light is then channeled through the a-Si photodiode layer where it is converted to a digital output signal. The digital signal is then read out by Thin Film Transistors (TFTs) or by fiber coupled Charged Couple Devices (CCDs). The image data file is sent to a computer for display. 2. Direct FPDs: Amorphous Selenium Flat Panel Detectors (a-Se) are known as “direct” detectors because X-ray photons are converted directly to charge. The outer layer of the flat
Computed and Digital Radiography
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Fig. 12.2: Schematic diagram showing types of DR flat panel detectors (FPD): (i) Direct conversion flat panel detectors: X-rays are converted to electronic signal by amorphous selenium photoconductor; (ii) Indirect conversion flat panel detector: X-rays are converted to visible light by scintillator, which is further converted to electronic signal by silicon photodiode. Electronic signal is converted to digital image by TFT arrays
panel in this design is typically a high voltage bias electrode. The bias electrode accelerates the captured energy from an X-ray exposure through the amorphous selenium layer. X-ray photons flowing through the selenium layer create electron hole pairs. These electron holes transit through the selenium based on the potential of the bias voltage charge. As the electron holes are replaced with electrons, the resultant charge pattern in the selenium layer is read out by a TFT array. The image data file is sent to a computer for display. Computed radiography (CR) and DR use a medium to capture X-ray energy and produce a digital image. Both also present an image within
seconds of exposure. CR involves the use of a cassette that houses the imaging plate, similar to traditional film-screen systems to record the image whereas DR captures the image directly onto a flat panel detector without the use of a cassette. Image processing or enhancement can be applied on both DR and CR images due to the digital format. DR may offer improved workflow for routine procedures due to the elimination of cassette manipulation and processing, as well as a greater capacity to limit radiation exposure. CR continues to offer flexible position of the image receptor for procedures such as those done for portable film, trauma, surgical cases and crosstable lateral projections.
13 C H A PT E R
Picture Archiving and Communication System
Picture archiving and communication system (PACS), is based on universal DICOM (Digital imag ing and communications in medicine) format. DICOM solutions are capable of storing and retrieving multi modality images in a proficient and secure manner in assisting and improving hospital workflow and patient diagnosis (Flow chart 13.1). The aim of PACS is to replace conventional radiographs and reports with a completely electronic network. These digital images can be viewed on monitors in the radiology department, emergency rooms, inpatient and outpatient departments, thus saving time, improving efficiency of hospital and avoid incurring the cost of hard copy images in a busy hospital. The three basic means of rendering plain radiographs images to digital are computed radiography (CR) using photostimulable phosphor plate technology; direct digital radiography (DDR) and digitizing conventional analog films. Non image data, such as scanned documents like PDF (portable document format) is also incorporated in DICOM format. Dictation of reports can be integrated into the system. The recording is automatically sent to a transcript writer’s workstation for typing, and can also be made available for access by physicians, avoiding typing delays for urgent results. Radiology has led the way in developing PACS to its present high standards. Picture archiving and communication system (PACS) consists of
four major components: The hospital information system (HIS) with imaging modalities such as radiography, computed radiography, endoscopy, mammography, ultrasound, CT, PET-CT and MRI, a secured network for the transmission of patient information, workstations for interpreting and reviewing images and archives for the storage and retrieval of images and reports. Backup copies of patient images are made provisioned in case the image is lost from the PACS. There are several methods for backup storage of images, but they typically involve automatically sending copies of the images to a separate computer for storage, preferably off-site. In PACS, no patient is irradiated simply because a previous radiograph or CT scan has been lost; the image once acquired onto the PACS is always available when needed. Simultaneous multilocation viewing of the same image is possible on any workstation connected to the PACS. Numerous post-processing soft copy manipulations are possible on the viewing monitor. Film packets are no longer an issue as PACS provides a filmless solution for all images. The PACS can be integrated into the local area network and images from remote villages can be sent to the tertiary hospital for reporting. Picture archiving and communication system (PACS) is an expensive investment initially but the costs can be recovered over 5 years period. It requires a dedicated maintenance. It is important
Picture Archiving and Communication System
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Flow chart 13.1: Picture archiving and communication system (PACS)
to train the doctors, technicians, nurses and other staff to use PACS effectively. Once PACS is fully operational no films are issued to patients. Picture archiving and communication system (PACS) breaks the physical and time barriers associated with traditional film-based image retrieval, distribution and display. PACS can be linked to the internet, leading to
teleradiology, the advantages of which are that images can be reviewed from home when on call, can provide linkage between two or more hospitals, outsourcing of imaging examinations in understaffed hospitals. The PACS is offered by all the major medical imaging equipment manufacturers, medical IT companies and many independent software companies.
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Computed Tomography Contrast Media
IODINATED INTRAVASCULAR AGENTS Intravascular radiological contrast media are iodine containing chemicals which add to the details in any given CT scan study and thereby aid in the diagnosis. Contrast overall enhances the body tissues. It helps to show the lesion which could not be appreciated on plain scan or shows the lesion better than what was seen in the plain scan. Contrast was first introduced by Moses Swick. Iodine (atomic weight 127) is an ideal choice element for X-ray absorption because the korn (K) shell binding energy of iodine (33.7) is nearest to the mean energy used in diagnostic radiography and thus maximum photoelectric interactions can be obtained which are a must for best image quality. These compounds after intravascular injection are rapidly distributed by capillary per meability into extravascularextracellular space and almost 90 percent is excreted via glomerular filtration by kidneys within 12 hours. Following iodinated contrast media are available: 1. Ionic monomers, e.g. Diatrizoate, Iothalamate, Metrizoate. 2. Nonionic monomers, e.g. Iohexol, Iopamidol, Iomeron. 3. Ionic dimer, e.g. Ioxaglate. 4. Nonionic dimer, e.g. Iodixanol, Iotrolan.
The amount of contrast required is usually 1-2 ml/kg body weight. Normal osmolality of human serum is 290 mOsm/kg. Ionic contrast media have much higher osmolality than normal human serum and are known as high osmolar contrast media (HOCM), while nonionic contrast media have lower osmolality than HOCM and are known as low osmolar contrast media (LOCM). Side effects or adverse reactions to contrast media are divided as: 1. Idiosyncratic anaphylactoid reactions. 2. Nonidiosyncratic reactions like nephrotoxicity and cardiotoxicity. Adverse reactions are more with HOCM than LOCM, hence LOCM are preferred. Delayed adverse reactions although very rare are, however, more common with LOCM and include iodide mumps, systemic lupus erythematosus (SLE) and Stevens-Johnson syndrome. Principles of treat ment of adverse reaction involves mainly five basic steps: ABCDE A: Maintain proper airway B: Breathing support for adequate breathing C: Maintain adequate circulation. Obtain an IV access D: Use of appropriate drugs like antihistaminics for urticaria, atropine for vasovagal hypotension and bradycardia, beta agonists for bronchospasm, hydrocortisone, etc.
Computed Tomography Contrast Media
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E: Always have emergency back-up ready including ICU care. Following intravascular iodinated agent arterial opacification takes place at approximately 20 seconds with venous peak at approximately 70 seconds. The level then declines and the contrast is finally excreted by the kidneys. These different phases of enhancement are used to image various organs depending on the indication. Spiral CT, being faster is able to acquire images during each phase, thus provide much more information.
of barium (37) is near to the mean energy used in diagnostic radiography and thus maximum photoelectric interactions can be obtained which are a must for best image quality. Moreover, barium sulfate is nonabsorbable, nontoxic and can be prepared into a stable suspension. For CT scan of abdomen, 1000-1500 ml of 1-5 percent w/ vol barium sulfate suspension can be used. Severe adverse reactions are rare. Rarely mediastinal leakage can lead to fibrosing mediastinitis while peritoneal leakage can cause adhesive peritonitis.
ORAL CONTRAST
Iodinated Agents
The bowel is usually opacified in CT examinations of the abdomen and pelvis as the attenuation value of the bowel is similar to the surrounding structures and as a result pathological lesions can be obscured. Materials used are barium or iodine based preparations, which are given to the patient to drink preceding the examination to opacify the gastrointestinal tract.
Iodine containing oral contrast agents like gastro graffin and trazograf are given for evaluating gastrointestinal tract on CT scan.
Barium Sulfate Barium sulfate preparations are used for evaluating gastrointestinal tract. Barium (atomic weight 137) is an ideal choice element for X-ray absorption because the K shell binding energy
AIR Air is used as a negative per rectal contrast medium in large bowel during CT abdomen and during CT colonography. CARBON DIOXIDE Rarely, carbon dioxide is used for infradiaphragmatic CT angiography in patients who are sensitive to iodinated contrast.
Index Page numbers followed by f refer to figure and t refer to table
A Abdominal angiography 81 aorta 81, 95f branches 82 radiograph 34 Acromion process 130 Advantages over conventional radiography 137 Amorphous selenium flat panel detectors 138 Analog-to-digital converter 137 Anatomical segmental division of lungs 28 Angiogram of abdominal aorta 82f celiac arterial trunk 83f posterior cerebral circulation arterial phase 74f, 75f capillary phase 75f, 76f venous phase 77f renal arteries in pyeloureterogram phase 87f right anterior cerebral circulation arterial phase 70f, 71f capillary phase 71f, 72f venous phase 72f, 73f right renal artery early arterial phase 85f late arterial phase 86f nephrogram phase 86f superior mesenteric artery 84f Angiography of lower limb 95f, 97f-101f Angle of Louis 79 Ankle joint 60 Anterior cerebral artery 69 communicating artery 69 interosseous artery 90f spinal arteries 73
Arch of aorta 80f Artery of foregut 83 midgut 85 Ascending thoracic aorta curves 80f Atlantoaxial junction 20f Axillary artery 89f, 93f
B Barium enema 111 study 111f sulfate 143 swallow 103 study 104f, 105f Base of distal phalanges 131 middle phalanges 131 proximal phalanges 131 Basilar artery 73 Body of clavicle 130 scapula 130 Brachial artery 89f, 93f Branches of aortic arch 67 external carotid artery 67 Bucky table 121
Cervical spine 13 Cervicothoracic junction 18f Circle of Willis 68 Clivus canal angle 27 Coccyx 16 Computed radiography 137, 139, 140 contrast media 142 Coupled charged couple devices 138 Craniovertebral angle 27
D Dacrocystogram 125, 125f, 126f Deep cerebral veins 74 palmar arch 92f vein 92 Digital radiography 138 subtraction angiography 135 veins 91 Direct digital radiography 140 Distal femur 132 phalanges 131 Dorsolumbar spine 14 Dural sinuses 76, 79
C
E
Calcaneus 132 Capitellum 130 Carbon dioxide 143 Cavernous portion of internal carotid artery 67 Celiac arterial trunk 83 trunk 81 Cephalic veins 91 Cerebral circulation 67, 68 cortical veins 74
Elbow joint 41, 128f, 130t Epiphysis 132 External iliac and common iliac artery 97f, 98f Extracranial carotid arteries 67
F Fallopian tubes 123, 123f, 124 Femoral head 131 Fibular shaft 132 Forearm 44
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Atlas on X-ray and Angiographic Anatomy
G Greater trochanter 131 tuberosity 130
H Head of humerus 130 radius 130 Hilgenreiner’s line 49 Hip joint 49, 129f, 131t Hysterosalpingogram 121, 122f-124f
I Inferior angle of scapula 130 mesenteric artery 84 Internal carotid artery 67-69
J Jugular bulb 78
K Knee joint 55, 129f, 132
L Lateral cuneiform 132 decubitus 34 epicondyle 130 Leech-Wilkinson cannula 124 Lesser trochanter 131 tuberosity 130 Locating lesions of lungs 31 Location of arches of foot 64f Low osmolar contrast media 142 Lower end of radius 131 ulna 131 limb 49
angiography 95 arterial system 96 venous system 102 Lumbosacral spine 14, 24f X-ray 25f, 26f Lung fissures 31
M Medial border of scapula 130 cuneiform 132 end of clavicle 130 epicondyle 130 Metacarpal heads 131 veins 91 Metatarsal shafts 132 Micturating cystourethrogram 117, 118f, 119f Middle cerebral artery 69 cuneiform 132 of coracoid process 130 phalangeal base 132 phalanges 131 Multiplanar reconstructed CT scan image of elbow joint 42f forearm 44f hand and wrist joint 46f shoulder joint 37f upper arm 40f reconstructed images of abdomen 35f joint 61f foot with ankle 63f knee joint 56f lower leg with ankle 59f thorax 29f
N Nasal cavity 9 septum 9
Normal intracranial arterial system 67 venous system 74 venous anatomy of brain 78
O Olecranon process 130 Orbit 10 Ossification centers 127
P Paranasal sinuses 6f, 10 Patella 132 Pelvic phleboliths 34 Perkin’s line 49 Petrous portion of internal carotid artery 67 Phalangeal shafts 132 Pituitary fossa 5f Popliteal artery 97, 100, 100f Posterior cerebral arteries 69, 73 communicating arteries 67, 69 fossa veins 74, 78 inferior cerebellar artery 69 Production of X-rays 133 Profunda femoris artery 96 Proximal femoral shaft 131 phalanges 131 tibia 132
R Radial arteries 90f, 94 Radiological anatomy of female reproductive organs 121 importance of craniovertebral junction 27 vertebral column in spinal injuries 24 Renal artery 88 angiogram 87
Index Retrograde urethrogram 120 Root of coracoid process 130
S Sacrum and coccyx X-ray 27f Shaft of humerus 130 Shoulder joint 37, 127f, 130t Sim’s speculum 124 Spinal canal 21 cord 21 Subclavian artery 89f Superficial femoral artery 96, 99f palmar arch 91f veins 91 Superior internal carotid artery 69 mesenteric arteriogram 85 artery 83 Systemic lupus erythematosus 142
T Teres minor 37 Thoracic aorta 79, 80f
Tibial shaft 132 tubercle 132 Trochlea 130 Turkish saddle 9
U Ulnar artery 90f, 94 shaft 130 Upper arm 38 gastrointestinal tract 104f, 105f limb 37 angiography 88 venous system 94
V Vein of Galen 74 Trolard and Labbe 74 Venous system 91 Vertebral arteries 69 Vertebrobasilar circulation 69
W Wrist joint and hand 44
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X X-ray 28 abdomen 36f ankle and foot 63f joint 62f cervical spine 15f-20f open mouth 20 right posterior oblique for intervertebral foramina 19f cervicothoracic junction 18f chest 29f-32f dorsolumbar spine 22f, 23f elbow joint 42f, 43f foot 64f, 65f forearm 45f hand and wrist joint 47f hip joint with pelvis 52f knee joint 57f skyline 58f KUB region 114f leg 60f, 61f pelvis with both hip joints 51f right hip joint 51f, 52f shoulder joint 38f, 39f skull 3f, 4f, 5, 5f, 6, 6f-8f, 11f, 12f thigh 54f, 55f upper arm 40f, 41f
