Treatment Simulation & Immobilization Flashcards
7 cards from real CMD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Treatment Simulation & Immobilization flashcards as text
Which type of CT acquisition is used to capture and characterize respiratory tumor motion during thoracic simulation?
Answer: 4D-CT (four-dimensional CT)
4D-CT acquires images sorted by respiratory phase, enabling visualization of tumor motion throughout the full breathing cycle for lung and liver treatments.
What does the Internal Target Volume (ITV) account for in radiation therapy planning?
Answer: Internal organ motion due to physiological processes such as respiration
The ITV encompasses the range of motion of the GTV/CTV caused by internal physiological movement, most commonly respiratory motion in thoracic and abdominal treatments.
A Digitally Reconstructed Radiograph (DRR) is generated from:
Answer: CT simulation data using ray-tracing algorithms through the 3D volume
DRRs are synthetic radiographs computed by tracing rays through CT simulation volumetric data, used as reference images for image-guided patient setup verification.
What is the primary advantage of vacuum-lock (vac-lock) bags compared to other immobilization devices?
Answer: They conform to any body contour and harden into custom-fitted, reproducible positioning aids
Vacuum bags conform to the patient's body surface and become rigid when air is evacuated, providing comfortable, custom-fitted immobilization adaptable to any treatment site.
When using respiratory gating for lung SBRT, the treatment beam is delivered during:
Answer: A defined phase or amplitude range of the respiratory cycle
The gating window is a specific respiratory phase or amplitude range during which the beam is active, reducing the required PTV margin by treating only when the tumor is in a reproducible position.
What is the primary purpose of multi-modality image registration during radiation therapy simulation?
Answer: To combine anatomical and functional information from multiple imaging modalities for improved target and OAR delineation
Image registration overlays MRI, PET, or other modality data onto the CT simulation dataset, leveraging complementary information to improve the accuracy of target volume and organ-at-risk delineation.
How does the Planning Target Volume (PTV) relate to the Clinical Target Volume (CTV)?
Answer: PTV adds a margin around the CTV to account for setup uncertainty and residual organ motion
The PTV margin expands around the CTV to ensure the CTV receives the prescribed dose despite geometric uncertainties including setup errors and residual internal motion during treatment.