Validation of a New Scintillating Fiber Dosimeter for Radiation Dose Quality Control in Computed Tomography

Abstract

(1) Background: The IVIscan is a commercially available scintillating fiber detector designed for quality assurance and in vivo dosimetry in computed tomography (CT). In this work, we investigated the performance of the IVIscan scintillator and associated method in a wide range of beam width from three CT manufacturers and compared it to a CT chamber designed for Computed Tomography Dose Index (CTDI) measurements. (2) Methods: We measured weighted CTDI (CTDIw) with each detector in accordance with the requirements of regulatory tests and international recommendations for the minimum, maximum and the most used beam width in clinic and investigated the accuracy of the IVIscan system based on the assessment of the CTDIw deviation from the CT chamber. We also investigated the IVIscan accuracy for the whole range of the CT scans kV. (3) Results: We found excellent agreement between the IVIscan scintillator and the CT chamber for the whole range of beam widths and kV, especially for wide beams used on recent technology of CT scans. (4) Conclusions: These findings highlight that the IVIscan scintillator is a relevant detector for CT radiation dose assessments, and the method associated with calculating the CTDIw saves a significant amount of time and effort when performing tests, especially with regard to new CT technologies.

Evaluation of a Scintillating Plastic Optical Fiber Device for Measuring kV-Cone Beam Computed Tomography Dose

“…Specifically, the relative differences were <5% when changing the IPS from 3 to 15 or the mA from 20 to 60 or 100. As expected, because of previous studies on scintillating fiber dosimeters [ 24 ], when dropping the tube voltage from 125 to 100 kV, the relative dose difference was −8.7%. Notably, when varying the field size, the maximum relative dose difference was −7.2%, which occurred at a field size of 2 cm.…”

“…During this study, we cross-calibrated the IVI-CBCT dosimeter with a pencil chamber that had itself been calibrated in a primary standards laboratory. To test the accuracy with which the device measured CTDI, we repeated this cross-calibration for three acquisition CBCT protocols (Pelvis, Pelvis Large, and Spotlight) that require different kV adjustments (125 or 140 kV) and fans (half fan or full fan); these protocols were chosen because our previous evaluations of the detector with CT scanners showed a non-negligible dependence of the response of the fiber on the energy of the beam; specifically, we found up to 31% of dose deviations between a scintillating fiber dosimeter and a pencil ionization chamber in a previous study [ 24 ]. Thus, we acquired 10 measurements for each detector and each protocol and found that IVI-CBCT demonstrated better constancy (coefficient of variation ranged from 0.1% to 0.5%) than the pencil chamber (0.5% to 1.7%).…”

“…Given that the actual spatial distribution of the imaging dose to the patient (and even the average) can differ substantially from the CTDI value, the possibility of using the detector to measure the composite image-guided radiotherapy (IGRT) dose should be assessed in further work using different dose quantities than the one used for QA applications. The device was derived from an original device developed for CT applications [ 23 , 24 , 25 ], named IVIscan ® . We recently adapted this device to radiotherapy kV-CBCT applications.…”