Thank you Francisco for the answer. However, I still have one doubt. Whether the cumulative dose is prescribed by the doctor? Or it is calculated based on some parameter.

~ I am working towards the development of a complete treatment planning system for telecobalt therapy.

i follow about this

Question misdirected to "radiology." Not a radiology question; seems to be a radiation oncology or cancer radiotherapy question.

I guess you are right.. this is rather a question for radiation oncologists.. Thanks Samson

Francisco is correct in his comments. I will add a few as well.

Calculating MU/time and calculating dose are the inverse of one another. You need to be given MU to calculate dose, or you need prescribed dose to calculate MU. Typically one is tasked with calculating MU or time after the dose is prescribed by the Radiation Oncologist. In simple calculations the dose would be prescribed to a point in the body and the field apertures shaped to conform to the local anatomy, followed by normalizing to an isodose line that covers the desired area. All of this goes into the calculation of MU or time needed to get the prescribed dose. Modern techiniques involve the use of inverse planning utilizing arcs, dynamic MLC's, etc. It is always important to optimize the dose distribution, whether in linac based therapy or cobalt teletherapy. The ability to optimize the dose distribution is tied to the imaging available (2D, 3D, 4D, PET, MRI, etc.) the technology contained in the treatment planning system, and the skill of the planner.