CMD Clinical Oncology & Treatment Techniques

Question 1

Which imaging modality is most commonly used for radiation therapy simulation and treatment planning due to its electron density information?

Accepted Answer

CT (Computed Tomography)

Answer

CT simulation provides Hounsfield unit data that is directly converted to electron density for dose calculation algorithms, making it the standard for treatment planning.

Question 2

In ICRU Report 62, which volume encompasses the Clinical Target Volume (CTV) plus a margin for setup uncertainty and organ motion?

Accepted Answer

Planning Target Volume (PTV)

Answer

The PTV adds a geometric margin around the CTV to account for setup uncertainties and internal organ motion, ensuring the CTV receives the prescribed dose.

Question 3

Which technique uses multiple non-coplanar arcs or beams with modulated intensity to deliver highly conformal dose distributions?

Accepted Answer

Intensity-Modulated Radiation Therapy (IMRT)

Answer

IMRT uses computer-optimized, modulated beam intensities across multiple fields to create dose distributions that conform tightly to target volumes while sparing adjacent critical structures.

Question 4

For breast cancer radiation therapy, the tangential field technique is designed primarily to:

Accepted Answer

Treat the breast/chest wall while minimizing lung and heart dose

Answer

Tangential fields are angled to treat the breast/chest wall volume while minimizing the dose to underlying lung and, for left-sided cancers, the heart.

Question 5

Which dosimetric parameter is most critical to monitor when treating head and neck cancers with IMRT to prevent xerostomia?

Accepted Answer

Mean parotid gland dose

Answer

Mean parotid gland dose should ideally be kept below 26 Gy to at least one parotid to preserve salivary function and prevent permanent xerostomia.

(CMD) Certified Medical Dosimetrist Practice Test

(CMD) Certified Medical Dosimetrist Practice Test

CMD Clinical Oncology & Treatment Techniques