CMD Treatment Simulation & Immobilization 2

Question 1

Which type of CT acquisition is used to capture and characterize respiratory tumor motion during thoracic simulation?

Accepted Answer

4D-CT (four-dimensional CT)

Answer

Standard helical CT

Answer

Cone-beam CT

Answer

Fluoroscopic simulation

Question 2

What does the Internal Target Volume (ITV) account for in radiation therapy planning?

Accepted Answer

Internal organ motion due to physiological processes such as respiration

Answer

Setup uncertainty between treatment fractions

Answer

Microscopic tumor extension beyond the visible gross tumor

Answer

Patient weight changes occurring during a treatment course

Question 3

A Digitally Reconstructed Radiograph (DRR) is generated from:

Accepted Answer

CT simulation data using ray-tracing algorithms through the 3D volume

Answer

Portal imaging acquired during treatment delivery

Answer

MRI simulation data only

Answer

Fluoroscopic images acquired at time of simulation

Question 4

What is the primary advantage of vacuum-lock (vac-lock) bags compared to other immobilization devices?

Accepted Answer

They conform to any body contour and harden into custom-fitted, reproducible positioning aids

Answer

They provide rigid immobilization equivalent to stereotactic frames

Answer

They have significantly lower fabrication cost than all alternatives

Answer

They have no effect on CT imaging quality or HU values

Question 5

When using respiratory gating for lung SBRT, the treatment beam is delivered during:

Accepted Answer

A defined phase or amplitude range of the respiratory cycle

Answer

The entire respiratory cycle to ensure full tumor coverage

Answer

Only when the patient voluntarily holds their breath indefinitely

Answer

The CT scan acquisition period only

Question 6

What is the primary purpose of multi-modality image registration during radiation therapy simulation?

Accepted Answer

To combine anatomical and functional information from multiple imaging modalities for improved target and OAR delineation

Answer

To reduce total imaging dose delivered to the patient

Answer

To improve native CT scan spatial resolution

Answer

To eliminate the need for physical patient simulation

Question 7

How does the Planning Target Volume (PTV) relate to the Clinical Target Volume (CTV)?

Accepted Answer

PTV adds a margin around the CTV to account for setup uncertainty and residual organ motion

Answer

PTV and CTV are geometrically identical volumes

Answer

PTV is a subset contained entirely within the CTV

Answer

PTV is defined independently without reference to the CTV