Assignment for Friday 9 April 2003:

1. [ This is a variation on problem 1 of chapter 11 in the book. I don't understand the wording of Alpen's problem, so I made up my own version]
Suppose that the Ellis power law equation (11.2) is valid in a particular tissue. A typical tumor dosing regimen consists of twenty treatments over four weeks using weekdays only, i.e. 25 days from the first Monday through the last Friday. Thus if the total dose delivered is 60 Gy, we deliver 3 Gy in each of the 20 treatments.

(a) Assuming NSD=17Gy, calculate the tolerance dose associated with this regimen. Will we be able to deliver this treatment regimen without damage to the normal tissue?

(b) If we wish to shorten the treatment time to three weeks (18 days from the first Monday to the last Friday) we will have to deliver larger doses per day, e.g. 60/18 = 3.33 Gy/day if we include weekends. If we allow more than one dose delivery per day we can reduce the dose delivered in each treatment back to lower levels, though. Calculate the number of doses we will have to deliver over the 18-day period if we wish to ensure that the full 60 Gy will be tolerated. Determine the dose per treatment.