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

Abstract

Purpose: Currently, traumatic bone diseases are diagnosed by assessing the micro 99mTc-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 99mTc-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 99mTc-HDP was therein injected to induce micro 99mTc-HDP deposition; second, the deposits were scanned using parallel-hole and pinhole collimator to generally survey 99mTc-HDP deposition pattern; and third, the scans underwent gamma correction (GC) to discern individual deposits for size measurement. Results: In original naïve 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 99mTc-HDP deposits that are analogous to 99mTc-HDP uptake on in-vivo bone scan. The smallest one we measured was 0.414 mm. Flooded phantoms and therein injected 99mTc-HDP form nebulous micro 99mTc-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.