A prototype real-time dose distribution monitoring system using plastic scintillators connected to optical fiber for interventional radiology

Interventional radiology (IVR) is a medical subspecialty of radiology to realize image-guided surgical procedures using imaging modalities, such as X-ray fluoroscopy. Recently, monitoring of skin dose is desired at clinical sites to reduce skin injuries by excessive X-ray exposure during the IVR procedures. We proposed a real-time dose distribution monitoring system for IVR. Some scintillation detectors which consist of low stopping power materials, such as plastic scintillators, are placed on a stretchable cap which can be worn by the patient. Scintillation light is fed to photo detectors outside the FOV through plastic optical fibers. This arrangement means that there are only radiolucent materials in the FOV and the proposed dose monitor does not interfere with the IVR procedure. As a result, the proposed monitor realizes real-time monitoring of the dose distribution on the patient's skin. We are developing a prototype of the proposed system which consists of three X-ray detectors. Each X-ray detector consists of a square-shaped plastic scintillator (BC400), optical fiber and photodiode. Dimensions of the plastic scintillator are 10.0 mm x 10.0 mm x 1.0 mm. A corner of the plastic scintillator is cut and connected to the plastic optical fiber (Eska GH4001) which has a 1.0 mm diameter and 1.5 m length. The scintillation photons are transported to a silicon photodiode (S1337-66BQ, Hamamatsu Photonics K. K.) through the optical fiber Each photodiode output is independently fed to a current-to-voltage conversion amplifier and measured with a 16ch multi function DAQ (NI USB-6351, National instruments) and displayed in real-time by LabView-based software. We conducted evaluation experiments of detector performance with the micro CT apparatus operating in the projection mode. The experimental results indicated that the proposed dose monitoring system could measure real-time dose distribution with at least a 1 s interval.