2022 AAPM 64th Annual Meeting
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Session Title: Imaging for Radiation Therapy: Challenges and Solutions
Question 1: A change to which of the following parameters will alter CT number and have the most impact on a dosimetry plan?
Reference:From Chapter 9, “Beam Energy, CT Number, and Dual Energy CT,” of The CT Handbook: Optimizing Protocols for Today’s Feature-Rich Scanners. Medical Physics Publishing 2020.
Choice A:Reconstruction kernel
Choice B:Beam energy
Choice C:Bowtie filter size and composition
Choice D:Patient positioning within the gantry
Question 2: Which automatic exposure control feature is most likely to be turned off by a radiation oncology physicist who needs consistent CT numbers?
Reference:From Chapter 7, “Automatic Exposure Control,” of The CT Handbook: Optimizing Protocols for Today’s Feature-Rich Scanners. Medical Physics Publishing 2020.
Choice A:Tube current modulation
Choice B:Rotation time selection
Choice C:Helical/spiral pitch selection
Choice D:Beam energy selection
Question 3: Challenges in CBCT imaging for radiotherapy localization include which of the following?
Reference:1. Mail, N., et al. "The influence of bowtie filtration on cone‐beam CT image quality." Medical Physics 36(1):22-32 (2009). 2. Bissonnette, Jean‐Pierre, Douglas J. Moseley, and David A. Jaffray. "A quality assurance program for image quality of cone‐beam CT guidance in radiation therapy." Medical physics 35(5):1807-1815 (2008). 3. Veiga, Catarina, et al. "Toward adaptive radiotherapy for head and neck patients: feasibility study on using CT‐to‐CBCT deformable registration for “dose of the day” calculations." Medical Physics 41(3):031703 (2014).
Choice A:Scatter radiation due to cone-beam geometry
Choice B:Non-uniform x-ray fluence at the detector plane
Choice C:Motion of the patient
Choice D:Limited field-of-view
Choice E:All of the above
Question 4: The use of an iterative cone-beam CT (iCBCT) algorithm has the potential to improve image quality for what percentage (approximately) of H&N and prostate cancer patients?
Reference:Gardner, Stephen J., et al. "Improvements in CBCT image quality using a novel iterative reconstruction algorithm: a clinical evaluation." Advances in Radiation Oncology 4(2):390-400 (2019).
Choice A:30%
Choice B:50%
Choice C:70%
Choice D:90%
Question 5: Beside magnetic field inhomogeneity, which of the following can cause geometric distortion in MRI images?
Reference:Price RG, Kadbi M, Kim J, Balter J, Chetty IJ, Glide-Hurst CK. Characterization and correction of gradient nonlinearity induced distortion on a 1.0 T open bore MR-SIM. Medical Physics. 2015 Oct;42(10):5955-60.
Choice A:Patient motion
Choice B:Insufficient gradient strength
Choice C:Gradient nonlinearity
Choice D:Long echo times
Question 6: Use of immobilization devices can increase the distance between the patient and receiving RF coils. Which of the following is impacted as a result?
Reference:Paulson ES, Erickson B et al. Comprehensive MRI simulation methodology using a dedicated MRI scanner in radiation oncology for external beam radiation treatment planning. Med Phys 2015 Jan;42(1):28-39
Choice A:It decreases image signal to noise ratio
Choice B:It increases image signal to noise ratio
Choice C:It reduces geometric distortion
Choice D:It increases geometric distortion
Question 7: Which FDG PET/CT imaging window for assessing cancer response during conventionally fractionated radiation therapy mitigates the risk of confounding tissue inflammation?
Reference:Bissonnette JP, Yap ML, Clarke K, Shessel A, Higgins J, Vines D, Atenafu EG, Becker N, Leavens C, Bezjak A, Jaffray DA, Sun A. Serial 4DCT/4DPET imaging to predict and monitor response for locally-advanced non-small cell lung cancer chemo-radiotherapy. Radiother Oncol. 2018 Feb;126(2):347-354. doi: 10.1016/j.radonc.2017.11.023. Epub 2017 Dec 12.
Choice A:Baseline
Choice B:1-3 weeks
Choice C:4-6 weeks
Choice D:6-8 weeks
Question 8: Which radiation treatment strategy presents the greatest challenge to quantitative FDG PET/CT imaging?
Reference:Bentzen SM. Theragnostic imaging for radiation oncology: dose-painting by numbers. Lancet Oncol. 2005 Feb;6(2):112-7.
Choice A:Uniform radiation dose to anatomic target volumes
Choice B:Simultaneous integrated radiation dose boosting
Choice C:Spatially non-uniform radiation dose scaled by target voxel biological disease burden
Choice D:Uniform radiation dose to metabolic target volumes
Question 9: Signal to noise ratio (SNR) of PET is a function of sensitivity (S), injected activity (A) and scan time (T) through the following relationship:
Reference:Simon R. Cherry, Terry Jones, Joel S. Karp, Jinyi Qi, William W. Moses, and Ramsey D. Badawi. “Total-Body PET: Maximizing Sensitivity to Create New Opportunities for Clinical Research and Patient Care” J Nuc Med 59(1):3-12, 2018.
Choice A:SNR ~ √(S x A x T)
Choice B:SNR ~ S x A x T
Choice C:SNR ~ A x √( S x T)
Choice D:SNR ~ S x √( A x T)
Question 10: When a repeat scan is suggested for fixing mis-registration between CT and PET images in PET/CT, which one is correct?
Reference:Pan T, Lu Y, Thomas MA, Liao Z, Luo D. New data-driven gated PET/CT free of misregistration artifacts. Int. J Radiat Oncol Biol Phys. 109(5): 1638-1646. 2021. PMCID: PMC7965243.
Choice A:Both CT and PET should be repeated
Choice B:Only CT should be repeated
Choice C:Only PET should be repeated
Choice D:Either CT or PET should be repeated
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