J Yeungnam Med Sci.  2022 Apr;39(2):108-115. 10.12701/yujm.2021.01123.

Clinical performance of FractionLab in patient-specific quality assurance for intensity-modulated radiotherapy: a retrospective study

• Oh SA
• Kim SY
• Park J
• Park JW
• Yea JW

• KMID: 2529268
• DOI: http://doi.org/10.12701/yujm.2021.01123

Abstract

Background
This study was aimed at comparing and analyzing the results of FractionLab (Varian/Mobius Medical System) with those of portal dosimetry that uses an electronic portal imaging device. Portal dosimetry is extensively used for patient-specific quality assurance (QA) in intensity-modulated radiotherapy (IMRT).
Methods
The study includes 29 patients who underwent IMRT on a Novalis-Tx linear accelerator (Varian Medical System and BrainLAB) between June 2019 and March 2021. We analyzed the multileaf collimator (MLC) DynaLog files generated after portal dosimetry to evaluate the same condition using FractionLab. The results of the recently launched FractionLab at various gamma indices (0.1%/0.1 mm–1%/1 mm) are analyzed and compared with those of portal dosimetry (3%/3 mm).
Results
The average gamma passing rates of portal dosimetry (3%/3 mm) and FractionLab are 98.1 (95.5%–100%) and 97.5% (92.3%–99.7%) at 0.6%/0.6 mm, respectively. The results of portal dosimetry (3%/3 mm) are statistically comparable with the QA results of FractionLab (0.6%/0.6 mm–0.9%/0.9 mm).
Conclusion
This paper presents the clinical performance of FractionLab by the comparison of the QA results of FractionLab using portal dosimetry with various gamma indexes when performing patient-specific QA in IMRT treatment. Further, the appropriate gamma index when performing patient-specific QA with FractionLab is provided.

Keyword

Electronic portal imaging device; FractionLab; Gamma passing rate; Intensity-modulated radiotherapy; Patient-specific quality assurance

Figure

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  Fig. 1. Patient-specific quality assurance with amorphous silicon (aS1000) electronic portal imaging device (EPID)-based portal dosimetry.

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  Fig. 2. Example of patient-specific quality assurance with portal dosimetry. (A) Portal dose image predicted by the portal dose image prediction (PDIP) algorithm, a dedicated two-dimensional algorithm for dose prediction. (B) Portal dose image measured by the electronic portal imaging device. (C) Gamma (3%/3 mm) evaluation between the predicted and measured portal dose images. (D) Three-dimensional gamma (3%/3 mm) image on the portal dose image.

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  Fig. 3. Image of the gamma scatter plot by field using multileaf collimator (MLC) log files (.dlg) and FractionLab (Varian/Mobius Medical System, Houston, TX, USA), generated after the radiotherapy treatment of one of the patients included in the study; one field creates two dlg files (‘A’ and ‘B’ banks).

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  Fig. 4. Example of patient-specific quality assurance with FractionLab (Varian/Mobius Medical System, Houston, TX, USA). (A) Planned fluence image, (B) Fluence image delivered by the log files, and (C) gamma (0.6%/0.6 mm) evaluation between the planned and delivered fluence images.

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  Fig. 5. Gamma passing rates of portal dosimetry (3%/3 mm) and FractionLab (Varian/Mobius Medical System, Houston, TX, USA) at various gamma indices (0.1%/0.1 mm–1%/1 mm).

Reference

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