Scintigraphic peritoneography reveals a non-uniform 99mTc-Pertechnetat aerosol distribution pattern for Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC) in a swine model

Although recent data are contradictory, it is still claimed that Pressurized Intra-Peritoneal Aerosol Chemotherapy (PIPAC) would deliver an aerosol which distributes homogeneously throughout the entire abdominal cavity. Tc-99m-Pertechnetat was administered in four postmortem swine using either PIPAC or liquid intra-peritoneal chemotherapy (IPC). The animals were examined by planar scintigraphy and SPECT/CT. Planar distribution images were divided into four regions of interest (ROIs: right/left upper and lower abdominal quadrant). SPECT/CT slices were scanned for areas of intense nuclide accumulation ("hot spots"). The percentage of relative distribution for planar scintigraphy was calculated by dividing the summed individual counts of each ROI by total counts measured in the entire abdominal cavity. The relative distribution of the "hot spots" was analyzed by dividing the counts of the local volume of interest (VOI) by the summed volume counts measured in the entire abdominal cavity. In all four animals, planar scintigraphy showed inhomogeneous nuclide distribution. After PIPAC only 8-10% of the delivered nuclide was detected in one ROI with a mean deviation of 40% and 74% from a uniform nuclide distribution pattern. In all animals, SPECT/CT revealed "hot spots" beneath the PIPAC Micropump, catheter tip, and in the cul-de-sac region which comprise about 25% of the total amount of delivered nuclide in 2.5% of the volume of the entire abdominal cavity. Our present data indicate that the intra-abdominal aerosol distribution pattern of PIPAC therapy is non-homogeneous and that the currently applied technology has still not overcome the problem of inhomogeneous drug distribution of IPC.