CMD Treatment Simulation & Immobilization

Question 1

What is the primary purpose of CT simulation in radiation therapy treatment planning?

Accepted Answer

To define the patient's 3D anatomy and establish treatment geometry

Answer

CT simulation provides volumetric anatomical data necessary for target volume delineation, beam arrangement, and dose calculation in treatment planning.

Question 2

Which immobilization device is most commonly used for head and neck cancer treatments?

Accepted Answer

Thermoplastic mask

Answer

Thermoplastic masks are custom-molded to the patient's facial contour and harden at room temperature, providing reproducible immobilization for head and neck treatments.

Question 3

What is the recommended CT slice thickness for treatment planning of head and neck tumors?

Accepted Answer

3 mm or less

Answer

Slice thicknesses of 3 mm or less provide superior anatomical detail for delineating complex structures in the head and neck region and improve dose-volume histogram accuracy.

Question 4

What is the purpose of using a flat couch insert during CT simulation?

Accepted Answer

To match the flat treatment couch geometry for consistent patient positioning between simulation and treatment

Answer

A flat couch insert replicates the flat linac treatment couch surface so the patient geometry at simulation matches treatment delivery conditions.

Question 5

Which patient preparation protocol is typically followed during prostate cancer CT simulation to reduce normal tissue dose?

Accepted Answer

Supine position with full bladder and empty rectum

Answer

A full bladder displaces the small bowel superiorly out of the treatment field while an empty rectum minimizes rectal volume receiving high dose.

(CMD) Certified Medical Dosimetrist Practice Test

(CMD) Certified Medical Dosimetrist Practice Test

CMD Treatment Simulation & Immobilization