Bladder wall dose from administered radiopharmaceuticals: the effects of variations in urine flow rate, voiding interval and initial bladder content

Equations are given for calculating the dose to the surface of the bladder wall for any values of the parameters, urine flow-rate, bladder voiding period and initial content, for any administered radiopharmaceutical with known biokinetics. The necessary relationships which describe the variation in dose to the bladder wall per unit of cumulated activity in contents with increasing volume of contents are given for 31 radionuclides. Two commonly used renal radiopharmaceuticals, 131I Hippuran and 99Tcsup(m) DTPA, are used to illustrate the effects of the above three physiological variables on the dose to the bladder wall and it may be concluded that, for radiopharmaceuticals which are rapidly transferred to the bladder, substantial dose reduction can be achieved by optimising these parameters. Thus, where possible, the patient should be well hydrated, the radiopharmaceutical should be administered when the bladder is partly filled and the voiding period should be about 1.5 h. (author)