CTP II Exam 1 Questions with Complete Solutions (Latest 2025) PTV - Correct Answers ✅GTV, CTV, and plus a margin FIXED volume what does the PTV account for - Correct Answers ✅internal motion set-up uncertainty purpose of immobilization - Correct Answers ✅immobilize patient precision/accuracy reproducibility minimize uncertainty Key factors to address for immobilization - Correct Answers ✅comfortable reproducible minimum beam attenuation affordable definition of a pixel - Correct Answers ✅pixel element is a 2D square how do pixels affect imaging - Correct Answers ✅the more pixels, the higher the resolution 1 / 3
CTP II Exam 1 Questions with Complete Solutions (Latest 2025) Side of pixel dose grid for IMRT - Correct Answers ✅2.5x2.5mm How does the pixel dose grid affect scan time - Correct Answers ✅the larger the dose grid, the quicker the scan time 2D magnification - Correct Answers ✅(projected x/initial x)* initial field size 2D inverse square - Correct Answers ✅(initial x/ projected x)^2 = new fluence Definition of a voxel - Correct Answers ✅3D pixel
- pixels connected by the slice thickness
3D box basically volume equation - Correct Answers ✅4/3 (pi)r^3 3D inverse sqaure - Correct Answers ✅evaluate in 2D and then add them all together How to determine calc time - Correct Answers ✅calculate the voxel area 2 / 3
CTP II Exam 1 Questions with Complete Solutions (Latest 2025) l*w*slice thickness compare the voxels sizes to determine how much longer or shorter the scan time would be homogenous vs heterogenous isodose distributions - Correct Answers ✅homogenous plan does not consider different tissue densities that may be present throughout the treatment area. A heterogeneous plan accounts for the different densities that may be present in the treatment area.For example, the lung will have increased beam attenuation because air is low density, as opposed to bone which is very dense.top 3 RT process uncertainties - Correct Answers ✅imaging contouring plan review Contouring Issues - Correct Answers ✅identifying appropriate lymphatics dose limiting structures Conformity index definition and ideal range - Correct Answers ✅treated volume/ PTV volume
- / 3