CMD Treatment Simulation & Immobilization 3

Question 1

What immobilization system is most appropriate for stereotactic radiosurgery (SRS) of an intracranial lesion?

Accepted Answer

Relocatable or rigid stereotactic frame providing sub-millimeter reproducibility

Answer

Standard thermoplastic mask alone

Answer

Vacuum-lock bag

Answer

Standard foam head rest

Question 2

What does 'indexed immobilization' mean in the context of radiation therapy simulation?

Accepted Answer

Using a numbered couch rail system to reproducibly position immobilization devices at the identical couch location each session

Answer

Documenting the patient's weight at each simulation appointment

Answer

Assigning patient ID numbers to each immobilization device

Answer

Indexing the patient's respiratory phase during CT acquisition

Question 3

What Hounsfield Unit (HU) value corresponds to water in CT imaging?

Accepted Answer

0 HU

Answer

-1000 HU

Answer

+1000 HU

Answer

+500 HU

Question 4

Why are a patient's arms positioned above the head during CT simulation for breast cancer treatment?

Accepted Answer

To move the arms and shoulders out of the planned tangential beam paths

Answer

To reduce respiratory motion artifact during scanning

Answer

To improve patient comfort during the procedure

Answer

To allow better CT image reconstruction algorithms to function

Question 5

What is the function of the orthogonal room lasers (sagittal, coronal, and transverse) in the CT simulation suite?

Accepted Answer

To define a fixed 3D coordinate reference system aligned with the CT isocenter for precise skin mark and tattoo placement

Answer

To provide ambient lighting for patient safety during gantry rotation

Answer

To monitor patient respiratory motion continuously during the scan

Answer

To align the CT detector array prior to acquisition

Question 6

Which of the following best describes the purpose of acquiring a scout (topogram) image at the start of CT simulation?

Accepted Answer

To survey anatomy and define the superior and inferior extent of the diagnostic CT acquisition volume

Answer

To deliver a test dose of radiation for patient sensitivity testing

Answer

To replace the need for a full volumetric CT scan

Answer

To assess whether IV contrast has distributed appropriately

Question 7

When performing image-guided radiation therapy (IGRT) setup verification, the daily CBCT is registered to which reference image set?

Accepted Answer

The planning CT acquired at simulation, using the same coordinate system as the treatment plan

Answer

The diagnostic CT acquired at time of cancer diagnosis

Answer

The previous day's CBCT image

Answer

A population-averaged anatomical atlas