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4. External Beam Radiation Therapy. [8 marks total] A radiation therapy beam is delivered from the front of the patient, using an SAD of 100 cm and an SSD of 94 cm, such that the treatment depth is exactly 6.00 cm. The dose to be delivered to the tumour is 100. rads. The field size at isocentre is 6.0 cm x 10.0 cm. The treatment is with a 10 MV x-ray beam, K = 1.00 rads/ MU, Sc = 0.986, and Sp = 0.986. The machine is calibrated at 100 cm. (You should use the TMR table provided on the Moodle page for this problem - interpolate between table entries if necessary.) a. How many monitor units are required for this treatment? [4 marks] b. What, approximately, would be the maximum dose delivered to normal tissue by this treatment beam? Briefly explain your reasoning. [2 marks] c. The machine is then rotated 180° to provide a second beam delivery from the back of the patient. The SAD is still 100 cm, but now the SSD is 90 cm. The dose to be delivered to the tumour is 100. rads, and all other parameters remain the same. How many monitor units are required for this treatment? [2 marks]

          4. External Beam Radiation Therapy. [8 marks total] A radiation therapy beam is delivered from the front of the patient, using an SAD of 100 cm and an SSD of 94 cm, such that the treatment depth is exactly 6.00 cm. The dose to be delivered to the tumour is 100. rads. The field size at isocentre is 6.0 cm x 10.0 cm. The treatment is with a 10 MV x-ray beam, K = 1.00 rads/ MU, Sc = 0.986, and Sp = 0.986. The machine is calibrated at 100 cm. (You should use the TMR table provided on the Moodle page for this problem - interpolate between table entries if necessary.)
a. How many monitor units are required for this treatment? [4 marks]
b. What, approximately, would be the maximum dose delivered to normal tissue by this treatment beam? Briefly explain your reasoning. [2 marks]
c. The machine is then rotated 180° to provide a second beam delivery from the back of the patient. The SAD is still 100 cm, but now the SSD is 90 cm. The dose to be delivered to the tumour is 100. rads, and all other parameters remain the same. How many monitor units are required for this treatment? [2 marks]

4. External Beam Radiation Therapy. [8 marks total] A radiation therapy beam is delivered from the front of the patient, using an SAD of 100 cm and an SSD of 94 cm, such that the treatment depth is exactly 6.00 cm. The dose to be delivered to the tumour is 100. rads. The field size at isocentre is 6.0 cm x 10.0 cm. The treatment is with a 10 MV x-ray beam, K = 1.00 rads/ MU, Sc = 0.986, and Sp = 0.986. The machine is calibrated at 100 cm. (You should use the TMR table provided on the Moodle page for this problem - interpolate between table entries if necessary.)
a. How many monitor units are required for this treatment? [4 marks]
b. What, approximately, would be the maximum dose delivered to normal tissue by this treatment beam? Briefly explain your reasoning. [2 marks]
c. The machine is then rotated 180° to provide a second beam delivery from the back of the patient. The SAD is still 100 cm, but now the SSD is 90 cm. The dose to be delivered to the tumour is 100. rads, and all other parameters remain the same. How many monitor units are required for this treatment? [2 marks]

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