The real-time dose measurement scintillating fiber array for intravascular brachytherapy procedures

Intravascular brachytherapy using catheter based high dose rate β sources has taken nowadays an important role in interventional cardiology to combat in-stent restenosis following percutaneous transluminal coronary angioplasty. At the present time, there is no detector system which can record accurate quantitative doses and spatial information in real time for intravascular brachy therapy. This is partially because of the short-range of the low energy beta emission of ³²P (average energy of 690 keV) and ⁹⁰Sr/⁹⁰Y (average energy of 930 keV) and the resolution limitation of existing extrapolation chambers and radiochromatic-dye films (currently the preferred method used). However, relatively high non-uniformity, which occurs at the stepping region due to excessive gapping or overlapping between steps, might result in in-stent restenosis or detrimental to the coronary vascular structure due to significant discrepancies between prescribed and delivered doses. We have developed a scintillating fiber based beta detector prototype which will permit: (i) extracting in real time of accurate dose measurements of the radioactive emitter in 2D or 3D; (ii) address the junction/stepping problem in a reliable fashion; (iii) allow extraction of information on the (in)homogeneity of the radioactive source (if any); and (iv) provide a quick feedback to radio-therapists for a fast re-adjustment of the radiation exposure for patient treatments. It is composed of an array of 3 × 3 mm² scintillating fibers optically coupled to photo-multiplier tubes for photon-to-current conversion. A CAMAC LabView based data acquisition system is used for data collection, histogramming and data analysis. A Geant4 Monte Carlo simulation was also specially developed for this detector to provide the necessary tool to investigate the various capabilities of such devices.