CMD Treatment Planning & Dosimetry 2

Question 1

Which dose calculation algorithm accounts for electron transport and is most accurate in heterogeneous tissues such as lung?

Accepted Answer

Monte Carlo simulation

Answer

Monte Carlo simulation explicitly models individual particle interactions including electron transport, making it the most accurate algorithm in heterogeneous media like lung.

Question 2

In IMRT planning, what is the primary purpose of using a dose-volume histogram (DVH)?

Accepted Answer

To summarize dose distribution statistics for structures

Answer

A DVH compresses 3D dose distribution data into a 2D graph showing the volume of a structure receiving at least a given dose, enabling quantitative plan evaluation.

Question 3

A patient's treatment plan shows a dose gradient of 10 Gy/cm across the spinal cord. What is the primary concern with this scenario?

Accepted Answer

Uncertainty in cord dose due to setup errors

Answer

Steep dose gradients near critical structures mean small setup errors can translate into large dose differences, making cord dose uncertain and potentially unsafe.

Question 4

When using the equivalent square field method, what is the equivalent square for a 6 cm × 12 cm rectangular field?

Accepted Answer

8.0 cm

Answer

The equivalent square is calculated as 2(a×b)/(a+b) = 2(6×12)/(6+12) = 144/18 = 8.0 cm.

Question 5

In proton therapy, the sharp distal dose fall-off beyond the Bragg peak creates a clinical challenge known as:

Accepted Answer

Range uncertainty

Answer

Range uncertainty in proton therapy means the actual Bragg peak location may differ from planned, potentially delivering high dose beyond the tumor or underdosing the target.

(CMD) Certified Medical Dosimetrist Practice Test

(CMD) Certified Medical Dosimetrist Practice Test

CMD Treatment Planning & Dosimetry 2