• Title/Summary/Keyword: Cross Calibration

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Development of BMD Phantom using 3D Printing (3D 프린팅을 이용한 골밀도 팬텀 개발)

  • Lee, Junho;Choi, Kwan-Yong;Hong, Sung-Yong
    • Journal of the Korean Society of Radiology
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    • v.13 no.2
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    • pp.185-192
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    • 2019
  • DXA is the most commonly used BMD examination equipment with the best performance on reflecting the biological alteration with tiny change of bone density. In spite of the importance of the quality control to maintain the accuracy and precision of the examination, considerable number of hospitals are not conducting QC due to the difficulty and high cost of the phantom product. This study develops the cross revision phantom with 3D printer and the change of the degree of infilling filaments which can be readily secured, and provides the usefulness assessment of the developed phantom by comparing with existing products. The Hounsfield Units of ABS, TPU, PLA, 30% Cu-PLA, and 30% Al-PLA are assessed. The Hounsfield Units result at infilling rate 100% was $-149.74{\pm}2.36$, $-55.62{\pm}7.14$, $-7.68{\pm}3.82$, $87.53{\pm}1.07$, and $1795.20{\pm}16.15$. The L1, L2, L3 BMD of 3D printing phantom with linear regression model were $0.620{\pm}0.010g/cm^2$, $1.092{\pm}0.025g/cm^2$, $1.554{\pm}0.026g/cm^2$ which are statistically relevant to the existing phantom products. This result provides the base line data for various medical phantom produce and capability of proper quality control of DXA equipment.

Comparison of Air Kerma­based and Absorbed Dose to Water­based Protocols in the Dosimetry of High Energy Electron Beams (고 에너지 전자선에 대한 공기커마와 물 흡수선량에 기반한 프로토콜간의 비교)

  • 박창현;신동오;박성용
    • Progress in Medical Physics
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    • v.14 no.4
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    • pp.249-258
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    • 2003
  • A few years ago, a proposal was made to change the dosimetry from the air kerma-based reference dosimetry to the absorbed dose-based reference dosimetry for all radiotherapy beams of ionizing radiation to improve the accuracy of dosimetry. Here, we present a dosimetry study in which the two most widespread absorbed dose­based protocols (IAEA TRS­398 and AAPM TG­51) were compared with an air kerma­based protocol (IAEA TRS-277) by measuring the absorbed dose in the same reference depth. Measurements were performed in three clinical electron beam energies using a PTW 30002 cylindrical chamber, and Markus and Roos plane­parallel chambers. $^{60}$ Co calibration factors were obtained from the KFDA. The absorbed dose differences between the air kerma­based and absorbed dose­based protocols were within 2.0% for all chambers in all beams. The results thus show that the obtained absolute dose values will be not significantly altered by changing from the air kerma­based dosimetry to the absorbed dose­based dosimetry. It was also shown that absorbed dose values between the absorbed dose­based protocols agreed by deviations of less than 0.5% for a cylindrical chamber and less than 0.7% for plane­parallel chambers using cross­calibration factors. Although the use of a cylindrical chamber and plane­parallel chambers resulted in a difference of less than 2% for all situations investigated here, to reduce errors, the plane­parallel chambers are recommended for electron energies in which the use of cylindrical chamber is not permitted in each protocol.

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Patient-Specific Quality Assurance in a Multileaf Collimator-Based CyberKnife System Using the Planar Ion Chamber Array

  • Yoon, Jeongmin;Lee, Eungman;Park, Kwangwoo;Kim, Jin Sung;Kim, Yong Bae;Lee, Ho
    • Progress in Medical Physics
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    • v.29 no.2
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    • pp.59-65
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    • 2018
  • This paper describes the clinical use of the dose verification of multileaf collimator (MLC)-based CyberKnife plans by combining the Octavius 1000SRS detector and water-equivalent RW3 slab phantom. The slab phantom consists of 14 plates, each with a thickness of 10 mm. One plate was modified to support tracking by inserting 14 custom-made fiducials on surface holes positioned at the outer region of $10{\times}10cm^2$. The fiducial-inserted plate was placed on the 1000SRS detector and three plates were additionally stacked up to build the reference depth. Below the detector, 10 plates were placed to avoid longer delivery times caused by proximity detection program alerts. The cross-calibration factor prior to phantom delivery was obtained by performing with 200 monitor units (MU) on the field size of $95{\times}92.5mm^2$. After irradiation, the measured dose distribution of the coronal plane was compared with the dose distribution calculated by the MultiPlan treatment planning system. The results were assessed by comparing the absolute dose at the center point of 1000SRS and the 3-D Gamma (${\gamma}$) index using 220 patient-specific quality assurance (QA). The discrepancy between measured and calculated doses at the center point of 1000SRS detector ranged from -3.9% to 8.2%. In the dosimetric comparison using 3-D ${\gamma}$-function (3%/3 mm criteria), the mean passing rates with ${\gamma}$-parameter ${\leq}1$ were $97.4%{\pm}2.4%$. The combination of the 1000SRS detector and RW3 slab phantom can be utilized for dosimetry validation of patient-specific QA in the CyberKnife MLC system, which made it possible to measure absolute dose distributions regardless of tracking mode.

Comparison Measurement Error of T-score Between Lumbar and Femoral Neck According to Kind of DXA (DXA측정기 종류에 따른 요추부와 대퇴경부 골밀도 값의 측정오차 비교)

  • Han, Beom-Hee;Jung, Hong-Ryang;Lim, Cheong-Hwan;Lee, Hye-Nam;Jeong, Cheon-Soo;Lee, Sang-Ho
    • The Journal of the Korea Contents Association
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    • v.10 no.3
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    • pp.250-257
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    • 2010
  • In this study, three different devices, Norland, Osteocore and Lunar were used to compare and analyze the measurement error by each bone density measurement device by classifying the physical characteristics into age, height and weight, the subject of total 300 sampling 100 persons for each device. Categorizing Lumbar region and Femoral neck as normal (T-score$\geqq$-1.0), osteopenia (-1.0>T-score>-2.5) and osteoporosis (T-score$\leqq$-2.5), the findings were observed as follows. Norland device showed the least measurement error in age and height, while Lunar showed the least in weight among the devices. And, the result of comparing the bone density measurement error based on the lumbar region showed that all of Lunar, Norland and Osteocore have the least variation of measurement error in osteopenia and the result of comparing based on the femoral neck showed that all of Lunar, Norland and Osteocore have the least variation of measurement error in osteoporosis. For each variable, the measurement error was observed to be vary upon the device. To solve this, standardized common Phantom should be used to compare and converge the measured value of each company and cross-calibration would be necessary when replacing the software.

Study on the Applicability of Semiconductor Compounds for Dose Measurement in Electron Beam Treatment (전자선 치료 분야의 선량 측정을 위한 반도체 화합물의 적용가능성 연구)

  • Yang, Seungwoo;Han, Moojae;Shin, Yohan;Jung, Jaehoon;Choi, Yunseon;Cho, Heunglae;Park, Sungkwang
    • Journal of the Korean Society of Radiology
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    • v.14 no.1
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    • pp.1-6
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    • 2020
  • In this study, it was intended to replace the existing plane parallel ionization chamber, which requires cross-calibration in electron beam treatment. The semiconductor compounds HgI2 was fabricated as detector, and the characteristics of HgI2 detector for the 6, 9 and 12 MeV electron beam was analyzed in the linear accelerator. It was also intended to evaluate the possibility of substitution with existing detectors and their applicability as electron beam dosimetry and to use them as a basic study of the development of electronic beam dosimeter. As a result of reproducibility, RSD was 0.4246%, 0.5054%, and 0.8640% at 6, 9, and 12 MeV energy, respectively, indicating that the output signal was stable. As a result of the linearity, the R2 was 0.9999 at 6 MeV, 0.9996 at 9 MeV, and 0.9997 at 12 MeV showed that the output signal is proportional to HgI2 as the dose is increased. The HgI2 detector of this study is highly applicable to electron beam measurement, and it may be used as a basic research on electron beam detection.