Perfusion studies to quantify abdominal radionuclide concentrations using single-photon emission computed tomography (SPECT)

The pancreas and abdomen of an Alderson Remcal phantom were filled with various activities of Tc-99m pertechnetate. Subsequently, SPECT images were obtained using a rotating gamma camera and in-line computing system. The radionuclide concentrations of the pancreas were in the range between 36.8 mbq/l and 552.3 mbq/l, while those measured in the abdomen varied from 1.76 mbq/l to 109.7 mbq/l. Two different filters and three cutoff frequences were used in the relevant calculations for transaxial sections. The subsequent evaluations of pancreas and abdomen were carried out using the region-of-interest technique. In order to assess the effect of scattering on the quantitative results further investigations were carried out on the basis of a subtraction procedure developed by Jaszczak et al. Changes in terms of multiplication of the results for planar images had no bearing on the accuracy of measurement. SPECT sections not corrected for scattering permitted reliable quantitative determinations to be made of both high and low activity concentrations. In two patients diagnosed with inoperable colorectal tumours SPECT was found a suitable tool for the planning and monitoring of intraarterial chemotherapy in combination with radiation treatment. (orig./MG)