Pixelized Measurement of Tc-99m-HDP Micro Particles Formed in Gamma Correction Phantom Pinhole Scan: a Reference Study

Purpose Currently, traumatic bone diseases are diagnosed by assessing the micro Tc-99m-hydroxymethylene diphosphonate (HDP) uptake in injured trabeculae with ongoing osteoneogenesis demonstrated by gamma correction pinhole scan (GCPS). However, the mathematic size quantification of micro-uptake is not yet available. We designed and performed this phantom-based study to set up an in-vitro model of the mathematical calculation of micro-uptake by the pixelized measurement. Methods The micro Tc-99m-HDP deposits used in this study were spontaneously formed both in a large standard flood and small house-made dish phantoms. The processing was as follows: first, phantoms were flooded with distilled water and Tc-99m-HDP was therein injected to induce micro Tc-99m-HDP deposition; second, the deposits were scanned using parallel-hole and pinhole collimator to generally survey Tc-99m-HDP deposition pattern; and third, the scans underwent gamma correction (GC) to discern individual deposits for size measurement. Results In original naive scans, tracer distribution was simply nebulous in appearance and, hence, could not be measured. Impressively, however, GCPS could discern individual micro deposits so that they were calculated by pixelized measurement. Phantoms naturally formed micro Tc-99m-HDP deposits that are analogous to Tc-99m-HDP uptake on in-vivo bone scan. The smallest one we measured was 0.414 mm. Flooded phantoms and therein injected Tc-99m-HDP form nebulous micro Tc-99m-HDP deposits that are rendered discernible by GCPB and precisely calculable using pixelized measurement. Conclusions This method can be used for precise quantitative and qualitative diagnosis of bone and joint diseases at the trabecular level.