Treatment time (for teleterapy unit) is similar with monitor unit (for LINAC).
Manual calculation for MU or time depends on dose delivery technique, there are SSD tech. and isocentric tech.
To calculate MU in LINAC,
If we calculate in SSD tech., we used data of PDD.
if we calculate in isocentric tech, we used data of TMR.
How does to calculate treatment time Cobalt-60 teletherapy unit for in SAD/isocentric techique?
we use TAR or TMR ?
if we have data of TAR and PSF Cobalt-60 from BJR Supplement 25, to calculate time in isocentric tech, we use TAR data? or must convert TAR to TMR ?
Thanks a lot for your discussion.
No you must not convert. It´s ok to use TAR for Co units. The limit for TAR techniques is Co-60 quality. If you are more interested please let my know. I´ve written a texbook about dosimetry and would send you the relating chapter.
To calculate treatment time Cobalt-60 teletherapy unit for in SAD/isocentric technique
we can use
1) TAR if dosimetry system is calibrated interms of dose to air (NDair) which is then be converted to NDwater (IAEA TRS 277)
2) TMR if dosimetry system is calibrated interms of dose water (NDwater) using IAEA TRS 398
It just dependent to your protocol in dosimetry for measuring the output factor. But the TMR is better, because the errors of measure of that is lower.
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