Calibration of 32P “hot-wall” angioplasty-balloon-catheter sources by liquid-scintillation-spectrometry-based destructive radionuclidic assays

A very quantitative, destructive-analysis procedure was devised for assaying the 32P activity content of “hot-wall” angioplasty-balloon catheters. These sources, developed and under investigation by Radiance Medical Systems, Inc. (Irvine, CA), are intended for use in the prophylactic inhibition of restenosis following balloon angioplasty in heart-disease patients. The assay was based on performing a physicochemical digestion of the balloon catheter to extract the 32P activity followed by liquid-scintillation (LS) spectrometry of the resultant solutions. Measurement-based corrections were applied for the residual activity remaining in the digested balloon debris and in all of the digestion apparatus. The LS spectrometry, with 3H-standard efficiency tracing, utilized a previously-developed method for resolving the always-present 33P impurity. Initial ionization current measurements on the sources prior to the destructive assays led to the establishment of calibration factors that can be used for subsequent non-destructive radionuclidic measurements on similar balloon-catheter sources.