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Fricke xylenol gelatin with glycine (FXGGly) as gel dosimeter was investigated for in vivo dosimetry at extended source-to-surface distance (eSSD) and validated with optically stimulated luminescence dosimeters (OSLD). FXGGly dosimeter was calibrated with a low dose rate of 10â¯cGy/min at eSSD and evaluated using anthropomorphic phantom simulating the actual treatment scenario. The FXGGly dosimeter was demonstrated as a suitable in vivo dosimeter for total body irradiation at eSSD with desirable dosimetric accuracy (±â¯2%) in comparison with OSLD or ionization chamber.
RESUMO
BACKGROUND AND AIM: The practicability of computing dose calculation on cone beam CT (CBCT) has been widely investigated. In most clinical scenarios, the craniocaudal scanning length of CBCT is found to be inadequate for localization. This study aims to explore extended tomographic localization and adaptive dose calculation strategies using Hounsfield unit (HU) corrected CBCT image sets. MATERIALS AND METHODS: Planning CT (pCT) images of the Rando phantom (T12-to-midthigh) were acquired with pelvic-protocol using Biograph CT-scanner. Similarly, half-fan CBCT were acquired with fixed parameters using Clinac2100C/D linear accelerator integrated with an on-board imager with 2-longitudinal positions of the table. For extended localization and dose calculation, two stitching strategies viz., one with "penumbral-overlap" (S1) and the other with "no-overlap" (S2) and a local HU-correction technique were performed using custom-developed MATLAB scripts. Fluence modulated treatment plans computed on pCT were mapped with stitched CBCT and the dosimetric analyses such as dose-profile comparison, 3D-gamma (γ) evaluation and dose-volume histogram (DVH) comparison were performed. RESULTS: Localizing scanning length of CBCT was extended by up to 15 cm and 16 cm in S1 and S2 strategies, respectively. Treatment plan mapping resulted in minor variations in the volumes of delineated structures and the beam centre co-ordinates. While the former showed maximum variations of -1.4% and -1.6%, the latter showed maximum of 1.4 mm and 2.7 mm differences in anteroposterior direction in S1 and S2 protocols, respectively. Dosimetric evaluations viz., dose profile and DVH comparisons were found to be in agreement with one another. In addition, γ-evaluation results showed superior pass-rates (≥98.5%) for both 3%/3 mm dose-difference (DD) and distance-to-agreement (DTA) and 2%/2 mm DD/DTA criteria with desirable dosimetric accuracy. CONCLUSION: Cone beam tomographic stitching and local HU-correction strategies developed to facilitate extended localization and dose calculation enables routine adaptive re-planning while circumventing the need for repeated pCT.
RESUMO
The percutaneous transluminal coronary angioplasty (PTCA) is one of the interventional procedures which impart high radiation doses to patients compared to the other cardiologic procedures. This study intends to audit and optimize radiation dose imparted to patients undergoing PTCA. Forty-four patients who underwent PTCA involving single or multiple stent placement guided under cardiovascular X-ray machine were included in the study. Radiation doses were measured using dose area product (DAP) meter for patients undergoing single and multiple stent placements during PTCA. A dose reduction of 27-47% was achieved using copper filters and optimal exposure parameters. The mean DAP values before optimization were 66.16 and 122.68 Gy cm(2) for single and multiple stent placement respectively. These values were 48.67 and 65.44 Gy cm(2) respectively after optimization. In the present scenario, due to the increase in the number of PTCAs performed and the associated risk from radiation, periodical audit of radiation doses for interventional procedures are recommended.