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PHYSICS 2003

Physics 2003

by N8BEME9, Aug 2010

Subjects: 2003 physics

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	2. In the 70-120 kvp range, damage to biologic tissue is most likely the result of: A. Scattered x-rays B. Characteristic x-rays C. Compton recoil electrons and the photoelectric effect D. Pair Production	2. In the 70-120 kvp range, damage to biologic tissue is most likely the result of: A. Scattered x-rays B. Characteristic x-rays C. Compton recoil electrons and the photoelectric effect D. Pair Production Answer: C – on multiple old tests.
	3. A CT scan is performed on a 90kg adult with 120 kvp, 240 mas, 1.5 Pitch, and a 512x512 matrix. If all parameters remain the same, and the field-of-view is reduced, which one of the following is true? A. The table speed will change B. The pixel size is smaller C. The child will receive essentially the same radiation dose to the abdomen	. A CT scan is performed on a 90kg adult with 120 kvp, 240 mas, 1.5 Pitch, and a 512x512 matrix. If all parameters remain the same, and the field-of-view is reduced, which one of the following is true? A. The table speed will change B. The pixel size is smaller C. The child will receive essentially the same radiation dose to the abdomen Answer: B – If you keep the matrix size the same and decrease the FOV, then the pixel size, which is 1/(2 x matrix in one direction), must become smaller.
	. Which does not affect Doppler frequency shift? 26. Speed of the moving object 27. Incident beam frequency 28. Beam velocity 29. Size of the moving object 30. Angle between beam and the moving objec	4. Which does not affect Doppler frequency shift? 26. Speed of the moving object 27. Incident beam frequency 28. Beam velocity 29. Size of the moving object 30. Angle between beam and the moving objec Answer: D – on multiple old tests.
	5. What is the total dose to a secretary from a source with a dose rate of 6mGy/hour at the secretary's desk and a half life of 10 minutes? The secretary and the source remain at the same distance for 2 hours. A. 0.7 B. 1.4 C. 2.8 D. 6 E. 12	5. What is the total dose to a secretary from a source with a dose rate of 6mGy/hour at the secretary's desk and a half life of 10 minutes? The secretary and the source remain at the same distance for 2 hours. A. 0.7 B. 1.4 C. 2.8 D. 6 E. 12 Answer: B – Basically we need to find the accumulative dose (Ã) via the MIRD equation. The only tricky thing is to convert the half life to hours (10 min = 0.167hrs) b/c the dose rate is given in hours. Here is the MIRD equation: Ã = 1.44 * f * Ao * Te Ã is the accumulative dose f is the fraction of activity per organ, which is 1 if you are calculating whole body dose (all organs added together equals 1) Ao is the original dose rate Te is the effective half life (1.44 * Te is the average half life) Ã = 1.44 * 1 * 6mGy/hr * 0.1667 hr Ã = 1.44 mGy
	6. Which of the following scintillation collimator yields the smallest image with the greatest resolution? A. multihole parallel B. slant hole C. converging D. diverging E. pinhole	. Which of the following scintillation collimator yields the smallest image with the greatest resolution? A. multihole parallel B. slant hole C. converging D. diverging E. pinhole Bad question – best resolution is pinhole; smallest image is diverging.
	7. Which of the following is true concerning the photoelectric effect in tissues. Most of the energy of the incident photon is: A. transferred to the nucleus B. transferred to the scattered photon C. given off as Brehmsstrulung radiation D. retained with the incident photon E. absorbed locally	7. Which of the following is true concerning the photoelectric effect in tissues. Most of the energy of the incident photon is: A. transferred to the nucleus B. transferred to the scattered photon C. given off as Brehmsstrulung radiation D. retained with the incident photon E. absorbed locally Answer: E – The characteristic xray and the displaced electron are locally absorbed.
	8. An echo is received from an interface 0.1 ms after pulse transmission. How deep (in cm) is the interface? A. 1.54 B. 7.7 C. 14.4 D. 15.4	. An echo is received from an interface 0.1 ms after pulse transmission. How deep (in cm) is the interface? A. 1.54 B. 7.7 C. 14.4 D. 15.4 Answer: B – Change the time to microseconds (1ms = 103 microseconds) and plug into the equation depth (cm) = 0.077 x time (us) depth (cm) = 0.077 x 100microseconds = 7.7 cm
	9. Which of the following is associated with an absorbed radiation threshold of 3 Gy? A. main erythema B. temporary epilation C. dry desquamation D. radiation dermatitis E. ulceration	9. Which of the following is associated with an absorbed radiation threshold of 3 Gy? A. main erythema B. temporary epilation C. dry desquamation D. radiation dermatitis E. ulceration Answer: B
	10. Which of the following is least likely to affect image quality in teleradiology? A. data cable transmission rates B. monitor grayscale luminescence C. bit depth D. matrix size E. compression	10. Which of the following is least likely to affect image quality in teleradiology? A. data cable transmission rates B. monitor grayscale luminescence C. bit depth D. matrix size E. compression Answer: A – The data cable transmission rates determine how long it takes to transfer an image. The transmission rate has nothing to do with the image quality (higher quality images will take longer to transmit, however).
	11. Studies of heritable effects of radiation have shown that mutations in germ cells secondary to diagnostic x-rays are: A. Most likely to be seen in the first generation of offspring B. Most likely to be seen in the second generation of offspring C. Occur by the second generation or will not occur D. Negligible	11. Studies of heritable effects of radiation have shown that mutations in germ cells secondary to diagnostic x-rays are: A. Most likely to be seen in the first generation of offspring B. Most likely to be seen in the second generation of offspring C. Occur by the second generation or will not occur D. Negligible Answer: D – on multiple old tests. Heritable effects have been shown in mice and flies, but not in humans.
	12. Regarding the X-ray interaction with biological soft tissues, which of the following is true: A. Pair production is the predominate interaction just above the k edge. B. Coherent scatter is common and results from the interaction with the nucleus C. The photoelectric effect predominates at a kVp > 50 D. Compton scatter results from the interaction with outer shell electrons	12. Regarding the X-ray interaction with biological soft tissues, which of the following is true: A. Pair production is the predominate interaction just above the k edge. B. Coherent scatter is common and results from the interaction with the nucleus C. The photoelectric effect predominates at a kVp > 50 D. Compton scatter results from the interaction with outer shell electrons Answer: D
	13. What is the maximum monthly allowable exposure to a fetus in a radiation worker? A. 1 mSv B. 0.5mSv C. 100mSv D. 1Sv E. 5Sv	13. What is the maximum monthly allowable exposure to a fetus in a radiation worker? A. 1 mSv B. 0.5mSv C. 100mSv D. 1Sv E. 5Sv Answer: B – the rates as I memorized it are 50mrem/mo and 500mrem/10mo.
	14.What type of ultrasound artifact is depicted in the picture?	14.What type of ultrasound artifact is depicted in the picture? A. Reverberation B. Refraction C. Reflection D. Side lobes E. Aliasing Answer: A – ringdown artifact is due to reverberation.
	15. If the 95% confidence interval for a count is between 120 and 168, then the 68% confidence interval is: A. 102 to 180 B. 100 to 150 C. 132 to 156 D. 120 to 150	15. If the 95% confidence interval for a count is between 120 and 168, then the 68% confidence interval is: A. 102 to 180 B. 100 to 150 C. 132 to 156 D. 120 to 150 Answer: C – 2 SD (i.e. 95 % CI) is 168-120 = 48, so 1 SD = 24. The count must be the median of the confidence interval, so (168+120)/2 = 144. Therefore, 1 SD is 144 +/- 12. (132 to 156)
	16) Milliampere-second (mAs) relates to what aspect of electrons? a) Velocity b) Number c) Flow rate d) Kinetic energy	16) Milliampere-second (mAs) relates to what aspect of electrons? a) Velocity b) Number c) Flow rate d) Kinetic energy Answer: B – on multiple old tests.
	17) This diagram represents what two forms of parent radionuclide decay? a) electron capture, positron emission b) gamma emission, positron emission c) electron capture, negatron emission d) gamma emission, negatron emission e) electron capture, alpha decay	17) This diagram represents what two forms of parent radionuclide decay? a) electron capture, positron emission b) gamma emission, positron emission c) electron capture, negatron emission d) gamma emission, negatron emission e) electron capture, alpha decay Answer: A – if the downward arrows go to the left, it mean Z is less in the daughter than the parent. The opposite is true if it goes right. By the way, a negatron is another word for an electron.
	18) Reducing workstation flicker can be accomplished by: a) Data compression b) Lower bandwidth c) Higher refresh rate d) Contrast suppression e) Synchronization	18) Reducing workstation flicker can be accomplished by: a) Data compression b) Lower bandwidth c) Higher refresh rate d) Contrast suppression e) Synchronization Answer: C – on multiple old tests.
	19) Which imaging modality is the highest contributor to medical radiation in the U.S.? a) CT b) Flouroscopy c) Plain film radiographs d) Nuclear imaging	19) Which imaging modality is the highest contributor to medical radiation in the U.S.? a) CT b) Flouroscopy c) Plain film radiographs d) Nuclear imaging Answer: A
	20) A 25 year old worker receives 2nd and 3rd degree burns over 50% of their body after an explosion at a radiopharmaceutical plant. Effects and treatment should include a) isolation and treatment in the ER b) determine radioactivity before approaching c) the radiation exposure will cause immediate damage d) shower to wash off possible exposure	20) A 25 year old worker receives 2nd and 3rd degree burns over 50% of their body after an explosion at a radiopharmaceutical plant. Effects and treatment should include a) isolation and treatment in the ER b) determine radioactivity before approaching c) the radiation exposure will cause immediate damage d) shower to wash off possible exposure Answer: A – on multiple old tests.
	21) What is the reason to use 360-degree rotation of the gamma camera in SPECT rather than a 180-degree rotation? a. improve the calculation of the linear attenuation coefficients b. increase the number of counts c. blurring of the central pixel d. reduce Compton scatter e. related to intrinsic properties of crystal	21) What is the reason to use 360-degree rotation of the gamma camera in SPECT rather than a 180-degree rotation? a. improve the calculation of the linear attenuation coefficients b. increase the number of counts c. blurring of the central pixel d. reduce Compton scatter e. related to intrinsic properties of crystal Answer: A – The number of counts can be the same with 180 degree rotation if the camera moves half as fast. The 360 allows calculation of the LAC via a transmission source. This is a different question than why use 2 cameras instead of one (on multiple tests including 2006). The advantage of 2 cameras is just a faster scan.
	22) A population is receives 10mGy of absorbed dose each generation. What is the genetic effect after many generations? A. <0.1% B. 1% C. 10% D. 20% E. 30%	22) A population is receives 10mGy of absorbed dose each generation. What is the genetic effect after many generations? A. <0.1% B. 1% C. 10% D. 20% E. 30% Answer: B – I am not sure about this one. I think the reasoning here is that BIER says the mutation doubling dose is 1 Gy. The doubling dose will increase genetic mutations by 100%. Maybe if you give 10 mGy (1/100 Gy) then you get 100%/100 or 1%. Lots of assumptions here!
	23) A patient swallows during digital subtraction angiography after the acquisition of the mask. What be done to improve the image? A. logarithmic transformation B. increase frame integration C. obtain a new mask D. frame integration E. Electric shock therapy	23) A patient swallows during digital subtraction angiography after the acquisition of the mask. What be done to improve the image? A. logarithmic transformation B. increase frame integration C. obtain a new mask D. frame integration E. Electric shock therapy Answer: C – on multiple old tests. I made up Option D.
	24) In standard chest radiography what film/screen combination is used? A. screen in front, single emulsion film B. screen in back, single emulsion film C. screen in front and back and double emulsion film D. screen in front and double emulsion film E. screen in back and double emulsion film	24) In standard chest radiography what film/screen combination is used? A. screen in front, single emulsion film B. screen in back, single emulsion film C. screen in front and back and double emulsion film D. screen in front and double emulsion film E. screen in back and double emulsion film Answer: C – makes a film sandwich. The mammo and extremity cassettes are an open faced film sandwich (film on top of screen). Yum...
	) What is the primary site of radiation-induced pathology in the heart? A. proximal aorta B. pericardium C. endocardium D. myocardium E. epicardium	25) What is the primary site of radiation-induced pathology in the heart? A. proximal aorta B. pericardium C. endocardium D. myocardium E. epicardium Answer: B – No idea why, but this is on several old tests.
	26. The addition of an intensifying screen in conventional film-screen radiography will: A. Increase the SNR B. Increase quantum mottle C. Increase spatial resolution D. Increase dose E. Decrease focal spot size	26. The addition of an intensifying screen in conventional film-screen radiography will: A. Increase the SNR B. Increase quantum mottle C. Increase spatial resolution D. Increase dose E. Decrease focal spot size Answer: B – anything that reduces the number of photons used to make the image will increase QM.
	27. A nursing mother should not breast feed for at lease two weeks before therapy with: A. I-123 Sodium Iodine B. 99m Tc C. 67 Gallium Citrate D. I-131	27. A nursing mother should not breast feed for at lease two weeks before therapy with: A. I-123 Sodium Iodine B. 99m Tc C. 67 Gallium Citrate D. I-131 Answer: D – on multiple old tests. Breast milk concentrates I-131. You want the woman to stop lactating before giving I-131 to decrease dose to breast. You cannot let a baby drink milk with I-131. See Mettler’s appendix as below. Note I rounded some here because these things vary with dose and I can’t memorize all the details. Check for yourself if you need more info: - most Tc products stop 24 hours after dose given then restart. - Ga 67 stop 4 wks - I 131 stop 2 weeks before and don’t restart - I 123 stop 3-5 d - Thalium stop 2 weeks
	28. In Digital Subtraction Angiography (DSA), decrease noise could be achieved by: A. Reducing the number of frames used in both mask and post contrast images.	Well we only have one answer choice and it is wrong. Examples of correct answers include frame integration and retaking the mask image if the patient moved.
	30. To decrease the patient dose in a single array CT, one could: A. Increase the pitch. B. Decrease the table movement. C. Increase the exposure time. D. Remove filter	30. To decrease the patient dose in a single array CT, one could: A. Increase the pitch. B. Decrease the table movement. C. Increase the exposure time. D. Remove filter Answer: A
	46. The patient couch movement index in acquiring a scan utilizing a helical CT scanner is a) proportional to pitch b) is defined in the term pitch as couch motion x collimation/rotation of gantry [sic definitely not the correct formula] c) not useful in dose measurement d) not relevant in helical scanners	46. The patient couch movement index in acquiring a scan utilizing a helical CT scanner is a) proportional to pitch b) is defined in the term pitch as couch motion x collimation/rotation of gantry [sic definitely not the correct formula] c) not useful in dose measurement d) not relevant in helical scanners Answer: A
	47. A woman involved in a traffic accident complained of lower back pain and underwent AP and lateral lumbosacral spine radiography. Two months later she was found to be 18 weeks pregnant. Which of the following is true? A. The radiographs should not have been obtained. B. A therapeutic abortion should be recommended. C. The cancer incidence to the fetus is < 0.5%. D. The fetus probably received an absorbed dose of 0.1 – 0.15 Gy. E. There is an increased risk of neonatal death.	47. A woman involved in a traffic accident complained of lower back pain and underwent AP and lateral lumbosacral spine radiography. Two months later she was found to be 18 weeks pregnant. Which of the following is true? A. The radiographs should not have been obtained. B. A therapeutic abortion should be recommended. C. The cancer incidence to the fetus is < 0.5%. D. The fetus probably received an absorbed dose of 0.1 – 0.15 Gy. E. There is an increased risk of neonatal death. Answer: C – there are questions like this on every old test, and the answer is always “it's going to be okay” or something like that.
	48. The energy measured of an incident gamma photon in the crystal of a scintillation camera is A. dependent on the central PMT B. 7 surrounding PMTs C. All the PMTs D. separate caliberation PMT	48. The energy measured of an incident gamma photon in the crystal of a scintillation camera is A. dependent on the central PMT B. 7 surrounding PMTs C. All the PMTs D. separate caliberation PMT Answer: C
	49. The best correlate for deterministic effects is A. Absorbed dose B. Effective dose C. mAs D. Exposure	49. The best correlate for deterministic effects is A. Absorbed dose B. Effective dose C. mAs D. Exposure Answer: A – not that effective dose (Sv) is a risk assessment for fatal cancers and severe genetic defects (stochastic effects). The deterministic effects have thresholds given in Gy (absorbed dose).
	50. If the probability of attenuation of a monochromatic photon is 75% after travelling 2mm Pb, what is the HVL? A. 0.5mm B. 1mm C. 2mm D. 4mm	50. If the probability of attenuation of a monochromatic photon is 75% after travelling 2mm Pb, what is the HVL? A. 0.5mm B. 1mm C. 2mm D. 4mm Answer: B – 75% is 2 HVLs.
	71. Regarding the S factor in internal dose calculations, which is FALSE? A. it can provide an accurate estimate of a patient's dose B. it is dependent on the organ's mass C. it is calculated for individual source to target organ pairs D. it is given in units of Gy/(MBq * Hr) E. it takes into account the entire emission spectrum	71. Regarding the S factor in internal dose calculations, which is FALSE? A. it can provide an accurate estimate of a patient's dose B. it is dependent on the organ's mass C. it is calculated for individual source to target organ pairs D. it is given in units of Gy/(MBq * Hr) E. it takes into account the entire emission spectrum Answer: E. It is separate for Beta emission vs Gamma emission.
	72. In mammography, the following will increase the patient's skin dose: A. increasing the distance between the patient and image receptor while keeping the source to image distance constant B. increasing the distance between the source and the image receptor while keeping the subject to image distance constant C. decreasing the mAs D. something about the focal spot	72. In mammography, the following will increase the patient's skin dose: A. increasing the distance between the patient and image receptor while keeping the source to image distance constant B. increasing the distance between the source and the image receptor while keeping the subject to image distance constant C. decreasing the mAs D. something about the focal spot Answer: A – decreasing the SOD will increase the dose by the inverse square law.
	73. In mammography, a molybdenum filter is used with a moly target because A. it increases Compton scatter (?) B. it has a low atomic number C. it transmits a large portion of the K-edge characteristic radiation D. it produces K-edge characteristic radiation	73. In mammography, a molybdenum filter is used with a moly target because A. it increases Compton scatter (?) B. it has a low atomic number C. it transmits a large portion of the K-edge characteristic radiation D. it produces K-edge characteristic radiation Answer: C – the anode material can be used to filter the x-ray beam b/c it allows the transmission of characteristic x-rays. The K-edge is always slightly higher than the characteristic x-ray energy because K characteristic x-rays is K-L.
	74. In CT, detection of a low density 4cm hepatoma will be improved on a non-contrast study with A. increased slice thickness B. decreased mAs C. something about the couch speed D. something about the ramp filter	74. In CT, detection of a low density 4cm hepatoma will be improved on a non-contrast study with A. increased slice thickness B. decreased mAs C. something about the couch speed D. something about the ramp filter Answer: A – improving the SNR will improve contrast. Increasing slice thickness will slightly decrease z-axis spatial resolution, but that should not be a factor in seeing a 4cm mass.
	75. In conventional linear tomography, a high density point (small round structure) located 2 cm below the imaging plane will appear on the image as: A. a star B. a line C. an ellipse D. a point E. a rectangle	75. In conventional linear tomography, a high density point (small round structure) located 2 cm below the imaging plane will appear on the image as: A. a star B. a line C. an ellipse D. a point E. a rectangle Answer: B – what is tomography?
	76. CT numbers (Hounsfield units) are related to: A. Atomic number B. Mass number C. Electrons/gram D. Linear attenuation coefficient E. Pixel size	76. CT numbers (Hounsfield units) are related to: A. Atomic number B. Mass number C. Electrons/gram D. Linear attenuation coefficient E. Pixel size Answer: D – remember that Compton effect is determined by electron density (Option C), but almost everything has the same electron density except hydrogen. Therefore electron density cannot be used to differentiate tissues, and C isn't correct. The best answer is D.
	77. Which of the following is true regarding Technetium 99m? A. It is produced in a cyclotron B. Its half life is too short for convenient labeling C. Its photon energy is too high for use in conventional scintillation cameras D. It is not available in carrier free state E. Auger electrons and internal conversion electrons do not contribute	Which of the following is true regarding Technetium 99m? A. It is produced in a cyclotron B. Its half life is too short for convenient labeling C. Its photon energy is too high for use in conventional scintillation cameras D. It is not available in carrier free state E. Auger electrons and internal conversion electrons do not contribute significantly to patient dose Answer: E – I guess the key word is significantly. Tc-99 is available in a carrier free state (http://jnm.snmjournals.org/cgi/reprint/16/7/639.pdf) which comes up on other questions.

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