In vivo estimation of radiation dose in renal pelvis and parenchyma during renography.

A method is presented for the determination of the spatio-temporal distribution of the radionuclide in the kidney and estimation of the dose in the renal pelvis wall and parenchyma, during renograms, on the basis of real data. A protocol was formulated by means of which the processing of the frames acquired in the various stages of the renogram enables the determination of the mass of the renal pelvis and the parenchyma as well as the time distribution of radioactivity in these compartments. The proposed methodology was applied to 30 normal subjects and 35 patients with obstructive nephropathy, acute and chronic obstructive uropathy and hydronephrosis. Our results, when compared with the MIRD dose estimations for the entire kidney showed slight deviations in normals, whereas very significant deviations were observed in the cases with pathology. This is due to the fact that the mass of the 'source' and 'target' organs as well as the biodistribution of the radiopharmaceuticals are essential in dose determination and were completely different in our calculations from those used in the MIRD estimations. Comparing the absorbed dose in renal parenchyma and pelvis wall with that estimated in vivo for the kidney considered as a system of one compartment, we found large differences only in abnormal cases. Differences were also noted between the absorbed dose in the aforementioned renal compartments depending on the considered abnormal renal states.