Development of a PMMA phantom as a practical alternative for quality control o gamma knife® dosimetry

被引：14

作者：

Chung, Jae Pil ^{[1
]}

Seong, Young Min ^{[1
]}

Kim, Tae Yeon ^{[2
]}

Choi, Yona ^{[2
]}

Kim, Tae Hoon ^{[3
]}

Choi, Hyun Joon ^{[4
]}

Min, Chul Hee ^{[4
]}

Benmakhlouf, Hamza ^{[5
]}

Chun, Kook Jin ^{[2
]}

Chung, Hyun-Tai ^{[6
]}

机构：

[1] Korea Res Inst Stand & Sci, Div Metrol Qual Life, Ctr Ionizing Radiat, 267 Gajeong Ro, Daejon 34311, South Korea

[2] Korea Univ, Dept Accelerator Sci, Sejong Campus,2511 Sejong Ro, Sejong 30019, South Korea

[3] Hanyang Univ, Coll Engn, Dept Nucl Engn, Seoul 04763, South Korea

[4] Yonsei Univ, Dept Radiat Convergence Engn, 1 Yeonsedae Gil, Wonju 26493, South Korea

[5] Karolinska Univ Hosp, Dept Med Radiat Phys & Nucl Med, SE-17176 Stockholm, Sweden

[6] Seoul Natl Univ, Coll Med, Dept Neurosurg, 101 Daehak Ro, Seoul 03080, South Korea

来源：

RADIATION ONCOLOGY | 2018年 / 13卷

关键词：

Gamma knife; PMMA phantom; Quality control; Absorbed dose rate to water; Dose distribution; Penumbra; Scattered photon contribution; RADIOSURGERY; PHOTON; FIELDS; BEAMS;

D O I：

10.1186/s13014-018-1117-8

中图分类号：

R73 [肿瘤学];

学科分类号：

100214 ;

摘要：

Background: To measure the absorbed dose rate to water and penumbra of a Gamma Knifes (R) (GK) using a polyrnethyl metacrylate (PMMA) phantom. Methods: A multi-purpose PMMA phantom was developed to measure the absorbed dose rate to water and the dose distribution of a GK The phantom consists of a hemispherical outer phantom, one exchangeable cylindrical chamber-hosting inner phantom, and two film-hosting inner phantoms. The radius of the phantom was determined considering the electron density of the PMMA such that it corresponds to 8 g/cm(2) water depth, which is the reference depth of the absorbed dose measurement of GK The absorbed dose rate to water was measured with a VFW TN31010 chamber, and the dose distributions were measured with radiochromic films at the calibration center of a patient positioning system of a GK Perfexion. A spherical water-filled phantom with the same water equivalent depth was constructed as a reference phantom. The dose rate to water and dose distributions at the center of a circular field delimited by a 16-mm collimator were measured with the PMMA phantom at six GK Perfexion sites. Results: The radius of the PMMA phantom was determined to be 6.93 cm, corresponding to equivalent water depth of 8 g/cm(2). The absorbed dose rate to water was measured with the PMMA phantom, the spherical water-filled phantom and a commercial solid water phantom. The measured dose rate with the PMMA phantom was 1. 2% and 1.8% higher than those measured with the spherical water-filled phantom and the solid water phantom, respectively. These differences can be explained by the scattered photon contribution of PMMA off incoming Co-60 gamma-rays to the dose rate. The average full width half maximum and penumbra values measured with the PMMA phantom showed reasonable agreement with two calculated values, one at the center of the PMMA phantom (LGP6.93) and other at the center of a water sphere with a radius of 8 cm (LGP8.0) given by Leksell Gamma Plan using the TMR10 algorithm. Conclusions: A PMMA phantom constructed in this study to measure the absorbed dose rates to water and dose distributions of a GK represents an acceptable and practical alternative for GK dosimetry considering its cost-effectiveness and ease of handling.

引用

页数：9

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