| Question 1: When an x-ray photon is detected by a photon-counting detector: |
| Reference: | Taguchi, K. and Iwanczyk, J. S. (2013), Vision 20/20: Single photon counting x-ray detectors in medical imaging. Med. Phys., 40: pp. 100901. doi:10.1118/1.4820371 |
| Choice A: | The photon energy is directly converted to light by a scintillator. |
| Choice B: | The photon energy is directly converted to electrical charge by a semiconductor. |
| Choice C: | The photon energy is converted to light and then electrical charge. |
| Choice D: | The photon energy is converted to electrical charge and then light. |
| Question 2: Which of the following is not a potential advantage of photon-counting detection compared to dual-kV spectral approaches? |
| Reference: | Taguchi, K. and Iwanczyk, J. S. (2013), Vision 20/20: Single photon counting x-ray detectors in medical imaging. Med. Phys., 40: pp. 100901. doi:10.1118/1.4820371
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| Choice A: | Rejection of electronic noise. |
| Choice B: | Improved weighting of photon information. |
| Choice C: | Acquisition of more than two spectral measurements. |
| Choice D: | Improved performance under high-flux conditions. |
| Question 3: Which of the following describes the pulse-pileup effect that is a potential limitation of photon-counting detectors? |
| Reference: | Taguchi, K. and Iwanczyk, J. S. (2013), Vision 20/20: Single photon counting x-ray detectors in medical imaging. Med. Phys., 40: pp. 100901. doi:10.1118/1.4820371
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| Choice A: | Multiple photons detected within a very short time period cannot be distinguished causing errors in the number and energy of the detected photons. |
| Choice B: | The charge cloud produced by one photon can be detected across neighboring pixels, causing errors in the number and energy of the detected photons . |
| Choice C: | When a photon is detected, the detector material may emit a characteristic x-ray, causing errors in the number and energy of the detected photons. |
| Choice D: | Impurities or defects in the detector material can trap charge causing errors in the detected energy of photons . |
| Question 4: A head scan is performed on a photon counting detector CT with 140 kV using 4 energy thresholds, which of the following 4 images has the least amount of beam hardening artifact at the posterior fossa?
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| Reference: | Yu, Z., Leng, S., Jorgensen, S.M., Li, Z., Gutjahr, R., Chen, B., Halaweish, A.F., Kappler, S., Yu, L., Ritman, E.L. and McCollough, C.H., 2016. Evaluation of conventional imaging performance in a research whole-body CT system with a photon-counting detector array. Physics in medicine and biology, 61(4), p.1572.
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| Choice A: | [20, 140] keV image. |
| Choice B: | [50, 140] keV image. |
| Choice C: | [63, 140] keV image. |
| Choice D: | [83, 140] keV image. |
| Question 5: As detector cell size decreases to achieve high spatial resolution, photon counting detector CT has an advantage over conventional CT in terms of dose efficiency mainly due to:
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| Reference: | Leng, S., Yu, Z., Halaweish, A., Kappler, S., Hahn, K., Henning, A., Li, Z., Lane, J., Levin, D.L., Jorgensen, S. and Ritman, E., 2016. Dose-efficient ultrahigh-resolution scan mode using a photon counting detector computed tomography system. Journal of Medical Imaging, 3(4), pp.043504-043504.
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| Choice A: | It uses a direct conversion technique therefore doesn’t suffer fill factor loss. |
| Choice B: | It counts individual photons. |
| Choice C: | It records photon energy. |
| Choice D: | It provides higher weighting to high energy photons. |
| Question 6: What is the maximum number of materials that can be decomposed using spectral mammography?
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| Reference: | Ding, H. and Molloi, S. (2012), Quantification of breast density with spectral mammography based on a scanned multi-slit photon-counting detector: a feasibility study. Phys Med Biol., 57(15):4719-38. doi: 10.1088/0031-9155/57/15/4719.
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| Choice A: | Five materials. |
| Choice B: | Four materials. |
| Choice C: | Two materials. |
| Choice D: | Three materials. |
| Question 7: Dual energy images are acquired using spectral mammography with:
|
| Reference: | Ding, H. and Molloi, S. (2012), Quantification of breast density with spectral mammography based on a scanned multi-slit photon-counting detector: a feasibility study. Phys Med Biol., 57(15):4719-38. doi: 10.1088/0031-9155/57/15/4719.
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| Choice A: | Two different kVps. |
| Choice B: | Two different kVps and two different filters. |
| Choice C: | Three different kVps. |
| Choice D: | Single kVp. |
| Question 8: In principle, how many basis functions are sufficient to represent the x-ray phase contrast image signal?
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| Reference: | “Elements of Modern X-ray Physics, 2nd Edition.” J. Als-Nielsen and D. McMorrow (Wiley, 2011)
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| Choice A: | 1. |
| Choice B: | 2. |
| Choice C: | 3. |
| Choice D: | None of the above. |
| Question 9: Which of the following depends on x-ray energy in grating-based multi-contrast imaging system?
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| Reference: | The fractional Talbot effect in differential x-ray phase-contrast imaging for extended and polychromatic x-ray sources.” M. Engelhardt et al., Journal of Microscopy, Vol. 232, Issue 1, pp. 145-157 |
| Choice A: | Fringe visibility of the grating interferometer. |
| Choice B: | X-ray phase contrast image signal. |
| Choice C: | X-ray phase contrast image noise. |
| Choice D: | All of the above. |
| Question 10: Photon counting detector is able to reduce radiation dose of x-ray phase contrast imaging for which of the following reason(s):
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| Reference: | Improving radiation dose efficiency of X-ray differential phase contrast imaging using an energy-resolving grating interferometer and a novel rank constraint.” Y. Ge et al., Optics Express, Vol. 24, Issue 12, pp 12955- 12968, 2016 |
| Choice A: | Improved optical performance of the grating interferometer enabled by the energy resolving capability. |
| Choice B: | Intrinsic low rank nature of the spatial-energy phase contrast image matrix. |
| Choice C: | Rejection of electronic noise accumulated from the phase stepping procedure. |
| Choice D: | All of the above. |
