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. 2017;21(3):232-239.
doi: 10.5114/wo.2017.70114. Epub 2017 Sep 29.

Assessment of the accuracy of dose calculation in the build-up region of the tangential field of the breast for a radiotherapy treatment planning system

Bagher Farhood  1 , Mohammad Taghi Bahreyni Toossi  2 , Shokouhozaman Soleymanifard  2 , Tohid Mortezazadeh  1
Affiliations

Assessment of the accuracy of dose calculation in the build-up region of the tangential field of the breast for a radiotherapy treatment planning system

Bagher Farhood et al. Contemp Oncol (Pozn). 2017.

Abstract

Aim of the study: Our objective was to quantify the accuracy of dose calculation in the build-up region of the tangential field of the breast for a TiGRT treatment planning system (TPS).

Material and methods: Thermoluminescent dosimeter (TLD) chips were arranged in a RANDO phantom for the dose measurement. TiGRT TPS was also used for the dose calculation. Finally, confidence limit values were obtained to quantify the accuracy of the dose calculation of the TPS at the build-up region.

Results: In the open field, for gantry angles of 15°, 30°, and 60°, the confidence limit values were 17.68, 19.97, and 34.62 at a depth of 5 mm, and 24.01, 19.07, and 15.74 at a depth of 15 mm, respectively. In the wedge field, for gantry angles of 15°, 30°, and 60°, the confidence limit values were 21.64, 26.80, and 34.87 at a depth of 5 mm, and 27.92, 22.04, and 20.03 at a depth of 15 mm, respectively. Additionally, the findings showed that at a depth of 5 mm, the confidence limit values increased with increasing gantry angle while at a depth of 15 mm, the confidence limit values decreased with increasing gantry angle.

Conclusions: Overall, TiGRT TPS overestimated doses compared to TLD measurements, and the confidence limit values were greater for the wedge field than for the open fields. Our findings suggest that the assessment of dose distributions in large-dose gradient regions (i.e. build-up region) should not entirely rely on TPS calculations.

Keywords: TPS; TiGRT; build up region; dose calculation accuracy; radiotherapy; surface dose.

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Conflict of interest statement

The authors declare no conflicts of interest. This work was financially supported by the office of vice president for research of Mashhad University of Medical Sciences.

Figures

Fig. 1
Fig. 1
Therapeutic range for the breast region on the RANDO phantom
Fig. 2
Fig. 2
Slice no. 18 of the RANDO phantom and arrangement of the thermoluminescent dosimeter chips at depths of 5 mm and 15 mm
Fig. 3
Fig. 3
Dose differences (%) between the calculated doses by TiGRT TPS and the measured doses by TLD-100 thermoluminescent dosimeter for the open field with gantry angles of 15°, 30°, and 60° at depths of 5 mm (A) and 15 mm (B), respectively
Fig. 4
Fig. 4
Dose differences (%) between the calculated doses by TiGRT TPS and the measured doses by TLD-100 thermoluminescent dosimeter for the wedge field with gantry angles of 15°, 30°, and 60° at depths of 5 mm (A) and 15 mm (B), respectively
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