Jonathan Boivin, Presenter: Nothing to Disclose

Sam Beddar PhD, Abstract Co-Author: Nothing to Disclose

Maxime Guillemette, Abstract Co-Author: Nothing to Disclose

Luc Beaulieu PhD, Abstract Co-Author: License agreement, Standard Imaging, Inc Researcher, Standard Imaging, Inc

The proposed real-time dosimeter is sensitive enough to measure in and out of field exposure in a clinical environment. It does not induce artefacts and cannot be taken for a catheter. This instrument has the potential to replace the fluoroscope estimate with accurate dose values, providing a much needed real-time dosimetry tool.

Long-lasting or repetitive fluoroscopically-guided interventional (FGI) procedures may build up radiation dose to harmful levels, leading to tissue injuries. Fluoroscopy systems provide a dose rate estimate at a single point in space. However, this value does not consider fundamental parameters, such as patient size and location. NCRP report 168 recommends that peak tissue dose shall be used to evaluate the potential for deterministic effects in specific tissue. A new plastic scintillation detector (PSD) is proposed, allowing real-time skin dose measurements during FGI procedures.

The PSD is composed of a 10 mm long plastic scintillation fiber having a 1 mm diameter. It is enclosed in a sealed plastic sheath and coupled to a 10 m long clear optic fiber. A photomultiplier tube is connected to its end and collects the light emitted by the scintillator when exposed to radiation. Calibration is performed at the fluoroscope estimation point by setting the PSD on the table along with an ion chamber, while increasing the dose rate. A Rando humanoid phantom is then set over the detectors. Field size, table height and gantry two axis are explored to assess the PSD performance. Every measure is performed in fluoroscopy and fluorography operation mode and compared to the fluoroscope dose rate estimate.

The PSD’s coefficient of variation remains under 1 % when dose rate is more than 12 mGy/min, and does not exceed 5 % at the lowest dose rate achievable of 1.4 mGy/min. Phantom measurements show a dose rate difference between the ion chamber and the PSD of less than 2 % when moving the table’s height, while the fluoroscope can underestimate the dose rate up to 120 % at lowest table position. Angular motions can bring the PSD out of the imaging field, but scattering dose is still measured accurately. In addition, the PSD is nearly invisible on the images.

Boivin, J, Beddar, S, Guillemette, M, Beaulieu, L, A New and Accurate Tool for Live Skin Dose Monitoring in Interventional Radiology: Measuring Dose without Compromise.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14015053.html