Prog Med Phys.  2014 Mar;25(1):23-30. 10.14316/pmp.2014.25.1.23.

Development of Dose Verification Method for In vivo Dosimetry in External Radiotherapy

• Hwang UJ
• Baek TS
• Yoon M

• KMID: 1910555
• DOI: http://doi.org/10.14316/pmp.2014.25.1.23

Abstract

The purpose of this study is to evaluate the developed dose verification program for in vivo dosimetry based on transit dose in radiotherapy. Five intensity modulated radiotherapy (IMRT) plans of lung cancer patients were used in the irradiation of a homogeneous solid water phantom and anthropomorphic phantom. Transit dose distribution was measured using electronic portal imaging device (EPID) and used for the calculation of in vivo dose in patient. The average passing rate compared with treatment planning system based on a gamma index with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit was 95% for the in vivo dose with the homogeneous phantom, but was reduced to 81.8% for the in vivo dose with the anthropomorphic phantom. This feasibility study suggested that transit dose-based in vivo dosimetry can provide information about the actual dose delivery to patients in the treatment room.

Keyword

Radiotherapy; Quality assurance; Electronic portal imaging device; Transit dose; In vivo dosimetry

MeSH Terms

Feasibility Studies
Humans
Lung Neoplasms
Radiotherapy*
Water
Water

Figure

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  Fig. 1. Brief flowchart of patient dose calculation program.

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  Fig. 2. Brief flowchart of dose distribution comparing program.

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  Fig. 3. EPID signal according to MU from the LINAC.

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  Fig. 4. Screen capture of developed software for calculating patient dose.

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  Fig. 5. Gamma distribution evaluated between dose distributions calculated from the EPID and given from the treatment planning system. (a) homogeneous solid phantom, (b) inhomogeneous humanoid phantom.

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  Fig. 6. Box plot of gamma passing rates represented in Table 2. Average passing rate was 95% for solid phantom and 81.8% for humanoid phantom.

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