Exam 24: Photon Dosimetry Concepts and Calculations

What is the patient's depth from the AP if the SAD is 100 cm and SSD is 91 cm?

The equivalent square of rectangular field of 20 x 10

As the energy increases,the TAR:

A patient is treated using two superiorly/inferiorly adjacent fields.The collimator setting for the superior field is 10 cm wide by 13 cm long.The collimator setting for the inferior field is 20 cm wide by 35 cm long.Both fields are treated at 100 cm SSD.Calculate the gap at the skin surface if the fields abut at a depth of 5 cm.

Calculate the PDD of depth (d)if the dose at Dmax is 180 cGy and the dose at d is 127 cGy.

As the depth increases,the PDD:

A tray holding custom blocks is measured as 97 cGy and the dose without the tray is 100 cGy.What is the tray transmission factor?

What is the depth from the PA if the SAD is 100 cm and the SSD is 89 cm?

As the energy increases,the PDD:

The physician prescribes the AP/PA field to be weighted 3:1 for the posterior field.How much dose is coming from the AP and the PA if total dose prescribed is 200 cGy?

Absorbed dose at a given depth divided by the dose in air dose at a fixed reference is the definition of:

The intensity of a radioactive beam is measured at a distance of 100 cm and found to be 250 mR/min.What will the intensity of this beam be at 105 cm?

The intensity of a radiation beam is measured at 10.0 mR/hr at a distance of 20 cm.What will be the intensity of this beam at 30.0 cm?

As the SSD increases,the TAR:

Find the PDD at 19 cm of an 18-MV beam of radiation that has a 12 x 12 cm treatment field.

Mayneord F factor is used in:

Calculate the PDD of depth (d)if the dose at D_max is 250 cGy and the dose at d is 231 cGy.

A patient is treated on a 6-MV accelerator; field size is 10 x 12 cm and depth of tumor is 6 cm.What is the PDD?

Using the 6-MV PDD chart,what is the dose at 10 cm if the dose at Dmax is 300 cGy per day on a 6-MV beam for a field size of 15 x 18?