| Question 1: For which of the following is dual-energy CT necessary: |
| Reference: | Reference: AAPM Report 291; for identical pixel values, separating measurements taken at two different energies into atomic number and mass density is the only way to differentiate the two materials |
| Choice A: | Measuring cerebral blood flow in terms of ml/min/100g brain tissue |
| Choice B: | Differentiating two materials having the same attenuation per voxel |
| Choice C: | Reducing the volume CT dose index values in pediatric patients |
| Choice D: | Decreasing the time that patients must hold their breath during chest CT exams |
| Question 2: What is the basic mechanism of material decomposition in dual-energy CT? |
| Reference: | Reference: AAPM Report 291; without a change in attenuation properties as photon energy changes, there would be no differential signal to measure with dual- or multi-energy CT |
| Choice A: | Exploiting the energy dependence of the x-ray attenuation caused by the photoelectric effect and Compton scattering |
| Choice B: | Evaluating the image noise at different x-ray energies |
| Choice C: | Evaluating the energy dependence of mass densities of the base materials |
| Question 3: What is a basic application of multi-energy CT? |
| Reference: | Reference: AAPM Report 291; virtual monoenergetic and material-specific images bring new clinical applications to CT imaging, such as improving the iodine contrast-to-noise ratio and differentiating materials that have similar CT numbers. |
| Choice A: | The computation of time-density curves |
| Choice B: | The computation of virtual monoenergetic images and material-specific images |
| Choice C: | The computation of dynamic perfusion maps |
| Choice D: | The reduction of image noise |
| Question 4: What is a primary challenge for material decomposition? |
| Reference: | Reference: AAPM Report 291; noise amplification can be very dramatic for the process of simultaneously solving multiple equations for multiple unknowns |
| Choice A: | Presence of iodine in contrast enhanced CT scans |
| Choice B: | Material decomposition can only be performed for axial CT scans |
| Choice C: | Amplification of image noise by the material decomposition |
| Choice D: | Material decomposition leads to geometric distortions of CT images |
| Question 5: Which type of multi-energy CT system is NOT be able to perform projection-space decomposition? |
| Reference: | Reference: AAPM Report 291; dual-source CT performs material decomposition using images |
| Choice A: | Dual-layer detector dual-energy CT |
| Choice B: | Photon-counting CT |
| Choice C: | Dual-source dual-energy CT |
| Choice D: | Fast-kV switching dual-energy CT |
| Question 6: Which type of multi-energy CT system does NOT currently provide tube current modulation in multi-energy CT imaging mode? |
| Reference: | Reference: AAPM Report 291; fast-kV switching modulates the pulse width of the tube current to equalize the photon fluence at the two different tube potentials. Currently there is no fluence modulation based on patient size or attenuation. |
| Choice A: | Dual-layer detector dual-energy CT |
| Choice B: | Split-Beam dual-energy CT |
| Choice C: | Dual-source dual-energy CT |
| Choice D: | Fast-kV switching dual-energy CT |
| Question 7: Which type of dual-energy CT system is most impacted by cross-talk between neighboring detectors? |
| Reference: | Reference: AAPM Report 291; photons interacting in a detector pixel of one detector layer can produce a scattered photon that interacts with a pixel in the other detector layer |
| Choice A: | Dual-layer detector dual-energy CT |
| Choice B: | Split-Beam dual-energy CT |
| Choice C: | Dual-source dual-energy CT |
| Choice D: | Fast-kV switching dual-energy CT |
| Question 8: Dual-energy CT’s ability to differentiate 2 materials having different effective atomic numbers: |
| Reference: | Reference: AAPM Report 291; a plot of the CT numbers in a low energy image to a high energy image will have data that fit to two distinct lines if the materials are sufficiently different. This will allow differentiation regardless if one knows the materials or whether mass is conserved. |
| Choice A: | Requires that the composition of the 2 materials is known in advance |
| Choice B: | Is not sufficient to separate iodine and calcium |
| Choice C: | Depends on the conservation of mass when solving the material decomposition equations |
| Choice D: | Can be used to visually indicate the two materials by visually overlaying a color code on top of a grey scale image |
| Question 9: True or False: The quantitative pixel values in a perfused blood volume image are in units of ml/min/100 g of tissue. |
| Reference: | Reference: AAPM Report 291; perfused blood volume images do not yield blood flow information |
| Choice A: | True |
| Choice B: | False |
| Question 10: In order for dual-energy CT to produce mass concentration values with clinically-acceptable accuracy, the dose to the patient must by increased by at least 50%: |
| Reference: | Reference: AAPM Report 291; clinically acceptable accuracies can be achieved at doses typical of single-energy CT. This is facilitated with different filtering techniques to help reduce the noise that is created during material decomposition. |
| Choice A: | True |
| Choice B: | False |
