Raphex 2009.pdf

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preface The RAPHEX Therapy exam 2009 was prepared by members of the Radiological and Medical Physics Society of New York (RAMPS, Inc.), the New York chapter of the American Association of Physicists in Medicine (AAPM). The exam format has been changed this year to match the syllabi for teaching Diagnostic Radiology and Radiation Oncology residents published by the AAPM's Subcommittee for Review of Radiation Physics Syllabi for Residents (RRPSR). The numbers of questions for each subject are approximately related to the number of teaching hours allocated to each subject. There are now two exams, Diagnostic and Therapy, each with about 140 questions, including general physics questions appropriate to the specialty. Exam committee: Susan Brownie, M.Sc., Editor Howard Amols, Ph.D. Richard Riley, Ph.D. Eugene Lief, Ph.D. Doracy Fontenla, Ph.D. Additional questions contributed by: Mark Belanich, M.S. Gabor Jozsef, Ph.D. If you are taking RAP HEX under exam conditions, your proctor will give you instructions on how to fill out your examinee and site IDs on the answer sheet. • You have 2 HOURS to complete the exam. • Non-programmable calculators may be used. • Choose the most complete and appropriate answer to each question. We urge residents to review the exam with their physics instructors. Any comments or corrections are appreciated and should be sent to: Susan Brownie, M.Sc. Maimonides Cancer Center Radiation Oncology Department 6300 8th Avenue Brooklyn, NY 11220 E-mail: [email protected] Copyright © 2009 by RAMPS, Inc., the New York chapter of the AAPM. All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without written permission from the publisher or the copyright holder. Published in cooperation with RAMPS by:

Medical Physics Publishing 4513 Vernon Boulevard Madison, WI 53705-4964 1-800-442-5778 E-mail: [email protected] Web: www.medicalphysics.org

therapy questions Tl.

A particle with a rest mass equivalent of938 MeV and a charge of +1 is a(an): A. Electron. B. Positron. C. Neutrino. D. Photon. E. Proton.

T2.

Different isotopes of the same element will have equal numbers of _ __ A. Electrons B. Protons and electrons C. Neutrons D. Electrons and neutrons E. Protons and neutrons

TJ.

The atom : C contains A. 6 6 8

1

B. 6 C. 14

8 6

8 8

D. 14

8

E.

6

20 14

8

electrons,

protons, and

neutrons.

T4.

The radioisotope used in brachytherapy that decays by electron capture, emitting 35.5 keV gammas, and 27 to 35 keV characteristic x-rays from internal conversion, is: A. 137Cs B. 192Ir c. 1o3Pd D. 12s1 E. 1311

TS.

After 10 half-lives, the fraction of activity remaining in a source is: A. (1/10)2. B. 1110. C. Dependent on the initial activity. D. (l/2)'o. E. 9/ 10.

T6.

An HDR treatment has a total treatment time of282 seconds on May 1. Assuming the 192Ir source has not been changed, the treatment will take _ _ seconds on May 15. (T 112 is 74 days.) A. 322 B. 302 C. 296

D. 264 E. 247

Raphex 2009

therapy questions T7.

Tungsten has the following binding energies: K = 69 keY, L = 12 keY, M = 2 keV. 100 keV electrons striking a tungsten target can cause emission of characteristic x-rays, including which three of the following energies (keV)? A. 100, 69, 31 B. 98, 88, 31 c. 95, 63, 15 D. 57, 67, 10

T8.

To produce a bremsstrahlung x-ray: A. An orbital electron is removed. B. An electron is slowed down by the field of the nucleus. C. An electron is absorbed by the nucleus. D. An electron will change shells, emitting the excess binding energy as an x-ray.

T9.

Regarding x-ray tubes, all of the following are true except: A. The cathode emits electrons by thermionic emission. B. Electrons travel from the anode to the cathode. C. The kVp is the peak voltage applied between the anode and the cathode. D. When electrons strike the target, characteristic x-rays and bremsstrahlung can be emitted. E. The target is angled and rotated to increase its heat capacity.

T I 0.

If the filtration of a diagnostic x-ray beam is increased, the resulting beam will have: A. A lower dose rate and greater HVL. B. A higher dose rate and higher effective energy. C. A lower dose rate, but the same HVL. D. The same dose rate, but a lower HVL. E. The same dose rate, but a greater HVL.

T I I.

Regarding the radiation emitted by the Gamma Knife, all of the following are true, except: A. The spectrum consists of gammas of discrete energies 1.17 and 1.33 MeV. B. The treatment time will double every 5.26 years. C. The HVL is about 5 em in lead. D. The beta minus emission contributes to the dose rate at the isocenter.

T 12.

With regard to the production of electron beams by linear accelerators, which of the following is true? A. The beam current is much higher in the "electron mode" than in the "photon mode." B. Electron beam flatness depends on the design of the cone or applicator. C. The bending magnet is rotated out of the beam when "electrons" are selected. D. Thick scattering foils can be used to reduce bremsstrahlung. E. All of the above.

2

Raphex 2009

therapy questions T 13.

On a linac with a nominal dose rate of 300 MU/min, a treatment requires a monitor unit setting of 150 MU. This means that: A. The timer will terminate the beam after exactly 30 seconds. B. The timer constantly monitors the true dose rate and terminates the beam after the time calculated to deliver 150 MU. C. The monitor chamber collects charge as the beam passes through it and terminates the beam after a charge equivalent to 150 MU has been collected. D. The beam is terminated after 150 R have been collected in the chamber.

T 14.

According to the AAPM's TG-40 report on QA, the light field on a linac corresponds to _ _ _ % of the dose on the axis at