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Abstract

BACKGROUND:

This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used.

MATERIALS AND METHODS:

Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm.

RESULTS:

The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools.

CONCLUSIONS:

QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA. 

Author information

Son J1, Baek T2, Lee B3, Shin D4, Park SY5, Park J4, Lim YK4, Lee SB4, Kim J4, Yoon M6.​

1Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Proton Therapy Center, National Cancer Center, Goyang, Korea.

2Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Department of Radiation Oncology, Ilsan Hospital, Goyang, Korea.

3Department of Bio-Convergence Engineering, Korea University, Seoul, Korea ; Department of Radiation Oncology, Sun Hospital, Daejeon, Korea.

4Proton Therapy Center, National Cancer Center, Goyang, Korea.

5McLaren Proton Therapy Center, Karmanos Cancer Institute, Flint, MI, USA.

6Department of Bio-Convergence Engineering, Korea University, Seoul, Korea.