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The Influence of Volume Effect in 2D-array Ion Chamber on the Measurement of IMRT Dose Distribution (2차원 배열형 이온함의 부피효과가 세기조절방사선치료의 선량분포 측정에 미치는 영향)

  • Kim, Sung Joon;Lee, Seoung Jun;Park, In Kyu;Lee, Jeong Eun;Park, Shin Hyung;Seol, Ki Ho;Kim, Jae Chul
    • Progress in Medical Physics
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    • v.24 no.1
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    • pp.41-47
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    • 2013

  • We evaluated the influence of volume effect on the measurement of IMRT dose distribution by comparing a 2D-array ion chamber and other dosimeters. Matrix phantom which is a 2D-array ion chamber having volume effect was compared with beam image system and film for the measurement of dose distribution. Five intensity-modulated radiation therapy plans were created using five fields in thevirtual phantom. The measured dose distribution was compared with the calculated one by radiation treatment planning system and analysis program. We evaluated the conformity of dose distribution by calculating correlation coefficients and gamma values. The highest error rate of 1.3% was associated with matrix phantom in which volume effect in small field sizes was substantial.

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Assessment of Dose Distributions According to Low Magnetic Field Effect for Prostate SABR

  • Son, Jaeman;An, Hyun Joon;Choi, Chang Heon;Chie, Eui Kyu;Kim, Jin Ho;Park, Jong Min;Kim, Jung-in
    • Journal of Radiation Protection and Research
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    • v.44 no.1
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    • pp.26-31
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    • 2019

  • Background: Stereotactic ablative radiotherapy (SABR) plans in prostate cancer are compared and analyzed to investigate the low magnetic effect (0.35 T) on the dose distribution, with various dosimetric parameters according to low magnetic field. Materials and Methods: Twenty patients who received a 36.25 Gy in five fractions using the MR-IGRT system (ViewRay) were studied. For planning target volume (PTV), the point mean dose ($D_{mean}$), maximum dose ($D_{max}$), minimum dose ($D_{min}$) and volumes receiving 100% ($V_{100%}$), 95% ($V_{95%}$), and 90% ($V_{90%}$) of the total dose. For organs-at-risk (OARs), the differences compared using $D_{max}$, $V_{50%}$, $V_{80%}$, $V_{90%}$, and $V_{100%}$ of the rectum; $D_{max}$, $V_{50%}$, $V_{30Gy}$, $V_{100%}$ of the bladder; and $V_{30Gy}$ of both left and right femoral heads. For both the outer and inner shells near the skin, $D_{mean}$, $D_{min}$, and $D_{max}$ were compared. Results and Discussion: In PTV analysis, the maximum difference in volumes ($V_{100%}$, $V_{95%}$, and $V_{90%}$) according to low magnetic field was $0.54{\pm}0.63%$ in $V_{100%}$. For OAR, there was no significant difference of dose distribution on account of the low magnetic field. In results of the shells, although there were no noticeable differences in dose distribution, the average difference of dose distribution for the outer shell was $1.28{\pm}1.08Gy$ for $D_{max}$. Conclusion: In the PTV and OARs for prostate cancer, there are no statistically-significant differences between the plan calculated with and without a magnetic field. However, we confirm that the dose distribution significantly increases near the body shell when a magnetic field is applied.

  • https://doi.org/10.14407/jrpr.2019.44.1.26 인용 PDF KSCI