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Monday, March 10, 2008

Dose rate and extended SSD

In the previous post, we have a patient with a 6 MV photon beam at an extended SSD of 125 cm. The calibration dose rate is given at Dcal (1.5, 10x10, 100) by 0.993 cGy/MU.

Calculate the reference dose rate in cGy/MU for the new SSD:

ANSWER

Obviously we know the dose rate in cGy/MU will decrease with a change to the extended SSD distance. The extent is given by

Calib dose rate x (100+dmax)/(extended SSD+ dmax) = 0.993 (100+1.5)/(125+1.5)

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