Three-Fold Acceleration of TG-142 Monthly Dosimetry Quality Assurance Using a Commonly Available Ion Chamber Array
Abstract
Purpose
Monthly TG-142 dosimetry quality assurance (QA) remains labor-intensive, creating workflow burden in high-throughput clinical environments. Although ion chamber arrays are widely available, their use for comprehensive TG-142 monthly dosimetry QA has not been fully optimized. This study developed and validated a streamlined, TG-142–compliant monthly dosimetry QA workflow that substantially reduces execution time without compromising dosimetric accuracy or reproducibility.
Methods
A consolidated monthly QA workflow was developed using a commercially available ion chamber array (SNC IC Profiler, Melbourne, FL) with a calibrated central-axis ion chamber (6x,100cm SSD,buildup dmax 1.5cm,10cmx10cm field for 1cGy/MU) and quad wedge to simultaneously evaluate photon (6X,6FFF,10X,10FFF,15X) and electron (6E,9E,12E,16E,18E) beams output, flatness, symmetry, and energy constancy. Respiratory gating output constancy and 60° enhanced dynamic wedge (EDW) factors were additionally assessed within the same setup. The workflow was benchmarked against conventional TG-142 monthly QA procedures using a Farmer ion chamber and solid water phantom. Agreement between methods, measurement reproducibility, and total QA execution time were evaluated across multiple linacs over repeated monthly measurements.
Results
The proposed workflow achieved a three-fold reduction in monthly dosimetry QA time, decreasing execution from approximately 3hr.30min. to 1hr.10min. without loss of dosimetric fidelity. Agreement with conventional TG-142 QA methods was excellent across all paired output measurements (n=40, cGy/MU), with Bland–Altman analysis demonstrating a mean bias of −0.009 (SD=0.0027) and narrow 95% limits of agreement (−0.0061 to 0.0043), indicating strong equivalence and absence of systematic bias. All evaluated constancy metrics remained within TG-142 tolerances, and measurement reproducibility was comparable to standard ion chamber techniques.
Conclusion
A TG-142–compliant monthly dosimetry QA workflow using a commonly available ion chamber array enables a three-fold reduction in QA time while maintaining dosimetric accuracy. This readily adoptable approach enables efficient, standards-compliant monthly QA and may inform future guidance on array-based monthly QA implementation without compromising patient safety.