Radiation dose to the bladder wall and the gonads from direct radionuclide cystography in children.

A dynamic spherical bladder model, previously developed in our laboratory, was implemented to evaluate the absorbed dose to the bladder wall from 99mTc-pertechnetate and direct radionuclide cystography (DRC). This model takes into account the flow rate of normal saline into the bladder and the bladder volume as a function of the filling time. The DRC examinations of 36 children were analysed and calculations were carried out in order to estimate (a) the absorbed dose to the bladder during and following the DRC examination and (b) the gonadal dose. It is shown that the estimated dose to the bladder wall is much greater than that estimated by static models. It is also shown that the absorbed dose to the bladder due to the activity in the residual urine following the examination is even greater than the dose received during the DRC procedure. Our results indicate that in order to reduce the radiation burden, besides the so far proposed precautions, concerning the shortening of the DRC procedure, the patient should also be well hydrated and encouraged to void frequently after the examination.