Question 1: The width of the dose spread function at the center of the cylindrical object is caused by: |
Reference: | John M. Boone, Dose Spread Functions in Computed Tomography: A Monte Carlo Study, Medical Physics 36(10): 4547 (2009). |
Choice A: | The spread of electrons, as radiation dose, laterally |
Choice B: | Off focus radiation produced in the CT scanner x-ray tube |
Choice C: | Scattered radiation |
Choice D: | The penumbra of the collimators |
Question 2: The dose spread function at the periphery of the phantom has a shorter range than at the center of the phantom because of: |
Reference: | John M. Boone, Dose Spread Functions in Computed Tomography: A Monte Carlo Study, Medical Physics 36(10): 4547 (2009). |
Choice A: | Solid angle effect at the periphery |
Choice B: | Internal reflection of x-rays at the air/phantom boundary |
Choice C: | Specular diffraction with small spatial irregularities at the phantom surface |
Choice D: | The physics of laminar flow. |
Question 3: The width of the dose spread function increases with: |
Reference: | John M. Boone, Dose Spread Functions in Computed Tomography: A Monte Carlo Study, Medical Physics 36(10): 4547 (2009). |
Choice A: | Decreasing effective energy of the x-ray beam |
Choice B: | Reduced diameter of the phantom |
Choice C: | Higher tube potential |
Choice D: | Increasing density of the phantom |
Question 4: On CT dose index, which of the following statements is true? |
Reference: | Robert L. Dixon. The Physics of CT Dosimetry: CTDI and Beyond. CRC Press, New York, Published April 2019, ISBN 9780367077594;
Robert L. Dixon, John M. Boone. Dose equations for tube current modulation in CT scanning and the interpretation of the associa |
Choice A: | The correct physical description of N×T in the CTDI100 equation is a beam width |
Choice B: | CTDIvol depends on N×T |
Choice C: | Scan length L is increased by increasing pitch. Then DLP = L×CTDIvol must also increase |
Choice D: | If the table failed to move during the complete helical scan protocol (L=0), then DLP = 0 |
Choice E: | None of the above is correct |
Question 5: Which of the following statements is true regarding three-dimensional automatic tube current modulation technique in CT? |
Reference: | Mannudeep Kalra, Michael Maher, Thomas Toth et. al, Technique and applications of tube current modulation in CT, Radiology 2004; 233:649-657. |
Choice A: | The scanner automatically adjusts tube current in the x-y plane (image slice) to achieve constant image quality (noise) |
Choice B: | The tube current is automatically decreased for each sensitive organ region |
Choice C: | The tube current is modulated attempting to make all images have a similar noise irrespective of patient size and anatomy |
Choice D: | The scanner adjusts mA and kVp for different body size determined from topogram and the exam type |
Question 6: Which of the following statements is NOT true regarding automatic tube current modulation in CT? |
Reference: | Mannudeep Kalra, Michael Maher, Thomas Toth et. al,Technique and applications of tube current modulation in CT, Radiology 2004; 233:649-657 |
Choice A: | All vendors utilize the localizer radiograph to estimate the attenuation, size, and shape information of the patient |
Choice B: | Z-axis tube current modulation can be applied without the angular tube current modulation |
Choice C: | In SmartmA, the scanner modulates the tube current in the real-time |
Choice D: | Real E.C. is an angular tube current modulation technique |
Question 7: Size specific dose estimator (SSDE) is able to normalize CTDIvol based on what patient size metrics? |
Reference: | AAPM Report No. 220: Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT, 2014 |
Choice A: | Patient effective diameter |
Choice B: | Water equivalent diameter |
Choice C: | Patient geometric measurement in the AP or LAT direction |
Choice D: | All of the above |
Question 8: Which of the following is not a mandatory/required data element in a CT DICOM image according to the current DICOM standard? |
Reference: | ftp://dicom.nema.org/MEDICAL/dicom/current/output/chtml/part03/sect_C.8.2.html |
Choice A: | kVp |
Choice B: | X-ray tube current in mA |
Choice C: | Data collection diameter |
Choice D: | Water equivalent diameter |
Question 9: In a single rotation axial scan at 80 kV, 140 mAs and 16×0.625-mm beam collimation, CTDIvol is 4.66 mGy (referenced to body CT phantom). Cross-sectional average dose in the midslice (at the scan range center) of an adult (with water equivalent diameter of 30 cm) is close to: |
Reference: | Xinhua Li, Kai Yang, Matthew C. DeLorenzo, Bob Liu. Assessment of radiation dose from abdominal quantitative CT with short scan length. Br J Radiol 2017; 90(1074):20160931 |
Choice A: | 2 × CTDIvol |
Choice B: | CTDIvol |
Choice C: | 0.5 × CTDIvol |
Choice D: | 0.1 × CTDIvol |
Choice E: | 0.01 × CTDIvol |
Question 10: Based on the measurement of the approach to equilibrium function on the central axis of 32-cm diameter acrylic phantom, scatter to primary ratio (SPR) is close to: |
Reference: | Xinhua Li, Da Zhang, Bob Liu. Monte Carlo assessment of CT dose equilibration in PMMA and water cylinders with diameters from 6 to 55 cm. Med. Phys. 2013;40 (3): 031903 (10pp). |
Choice A: | 10 |
Choice B: | 2 |
Choice C: | 1 |
Choice D: | 0.1 |
Choice E: | 0.01 |