X-ray detector made of plastic scintillators and WLS fiber for real-time dose distribution monitoring in 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, IVR is increasingly used in treatment of vascular lesions due to its low invasiveness. On the other hand, skin injuries due to prolonged x-ray exposure during the procedure have been reported. Therefore, monitoring of skin dose is desired in clinical sites for reduction of excessive x-ray exposure. We propose a real time dose distribution monitor 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. As the first step, we are developing a prototype x-ray detector element which consists of plastic scintillators and a wavelength shifting (WLS) fiber connected to the optical fiber. The square shaped WLS fiber is sandwiched by two plastic scintillators with a plate shape and dimensions of 10.0 mm x 4.5 mm x 1.0 mm. Scintillation light generated in the plastic scintillators is captured and converted to different wavelength light in the WLS fiber. The converted photons are transported to a multi-pixel photon counter (MPPC) through the 1 m length optical fiber which has the same diametrical size as the WLS fiber. We conducted evaluation experiments of detector performance with synchrotron-generated X-rays in the beamline BL-14A at the Photon Factor and micro CT (R_mCT2, RIGAKU) operating in the projection mode. The experimental results indicated that the proposed detector can measure X-ray doses in real-time with at least a 10 s interval.