• Title, Summary, Keyword: Anthropomorphic phantom

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COMPUTATIONAL ANTHROPOMORPHIC PHANTOMS FOR RADIATION PROTECTION DOSIMETRY: EVOLUTION AND PROSPECTS

  • Lee, Choon-Sik;Lee, Jai-Ki
    • Nuclear Engineering and Technology
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    • v.38 no.3
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    • pp.239-250
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    • 2006
  • Computational anthropomorphic phantoms are computer models of human anatomy used in the calculation of radiation dose distribution in the human body upon exposure to a radiation source. Depending on the manner to represent human anatomy, they are categorized into two classes: stylized and tomographic phantoms. Stylized phantoms, which have mainly been developed at the Oak Ridge National Laboratory (ORNL), describe human anatomy by using simple mathematical equations of analytical geometry. Several improved stylized phantoms such as male and female adults, pediatric series, and enhanced organ models have been developed following the first hermaphrodite adult stylized phantom, Medical Internal Radiation Dose (MIRD)-5 phantom. Although stylized phantoms have significantly contributed to dosimetry calculation, they provide only approximations of the true anatomical features of the human body and the resulting organ dose distribution. An alternative class of computational phantom, the tomographic phantom, is based upon three-dimensional imaging techniques such as magnetic resonance (MR) imaging and computed tomography (CT). The tomographic phantoms represent the human anatomy with a large number of voxels that are assigned tissue type and organ identity. To date, a total of around 30 tomographic phantoms including male and female adults, pediatric phantoms, and even a pregnant female, have been developed and utilized for realistic radiation dosimetry calculation. They are based on MRI/CT images or sectional color photos from patients, volunteers or cadavers. Several investigators have compared tomographic phantoms with stylized phantoms, and demonstrated the superiority of tomographic phantoms in terms of realistic anatomy and dosimetry calculation. This paper summarizes the history and current status of both stylized and tomographic phantoms, including Korean computational phantoms. Advantages, limitations, and future prospects are also discussed.

Beam Spoiler-dependent Total Body Irradiation Dose Assessment (전신방사선조사 시 선속 스포일러에 따른 선량 분포 및 영향 평가)

  • Lee, Dong-Yeon;Kim, Jung-Hoon
    • Journal of radiological science and technology
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    • v.41 no.2
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    • pp.141-148
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    • 2018
  • This study examined the properties of photons and the dose distribution in a human body via a simulation where the total body irradiation(TBI) is performed on a pediatric anthropomorphic phantom and a child size water phantom. Based on this, we tried to find the optimal photon beam energy and material for beam spoiler. In this study, MCNPX (Ver. 2.5.0), a simulation program based on the Monte Carlo method, was used for the photon beam analysis and TBI simulation. Several different beam spoiler materials (plexiglass, copper, lead, aluminium) were used, and three different electron beam energies were used in the simulated accelerator to produce photon beams (6, 10, and 15 MeV). Moreover, both a water phantom for calculating the depth-dependent dosage and a pediatric anthropomorphic phantom for calculating the organ dosage were used. The homogeneity of photon beam was examined in different depths for the water phantom, which shows the 20%-40% difference for each material. Next, the org an doses on pediatric anthropomorphic phantom were examined, and the results showed that the average dose for each part of the body was skin 17.7 Gy, sexual gland 15.2 Gy, digestion 13.8 Gy, liver 11.8 Gy, kidney 9.2 Gy, lungs 6.2 Gy, and brain 4.6 Gy. Moreover, as for the organ doses according to materials, the highest dose was observed in lead while the lowest was observed in plexiglass. Plexiglass in current use is considered the most suitable material, and a 6 or 10 MV photon energy plan tailored to the patient condition is considered more suitable than a higher energy plan.

Linear accuracy of cone-beam computed tomography and a 3-dimensional facial scanning system: An anthropomorphic phantom study

  • Oh, Song Hee;Kang, Ju Hee;Seo, Yu-Kyeong;Lee, Sae Rom;Choi, Hwa-Young;Choi, Yong-Suk;Hwang, Eui-Hwan
    • Imaging Science in Dentistry
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    • v.48 no.2
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    • pp.111-119
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    • 2018
  • Purpose: This study was conducted to evaluate the accuracy of linear measurements of 3-dimensional (3D) images generated by cone-beam computed tomography (CBCT) and facial scanning systems, and to assess the effect of scanning parameters, such as CBCT exposure settings, on image quality. Materials and Methods: CBCT and facial scanning images of an anthropomorphic phantom showing 13 soft-tissue anatomical landmarks were used in the study. The distances between the anatomical landmarks on the phantom were measured to obtain a reference for evaluating the accuracy of the 3D facial soft-tissue images. The distances between the 3D image landmarks were measured using a 3D distance measurement tool. The effect of scanning parameters on CBCT image quality was evaluated by visually comparing images acquired under different exposure conditions, but at a constant threshold. Results: Comparison of the repeated direct phantom and image-based measurements revealed good reproducibility. There were no significant differences between the direct phantom and image-based measurements of the CBCT surface volume-rendered images. Five of the 15 measurements of the 3D facial scans were found to be significantly different from their corresponding direct phantom measurements(P<.05). The quality of the CBCT surface volume-rendered images acquired at a constant threshold varied across different exposure conditions. Conclusion: These results proved that existing 3D imaging techniques were satisfactorily accurate for clinical applications, and that optimizing the variables that affected image quality, such as the exposure parameters, was critical for image acquisition.

Measurement of Patient Dose from Computed Tomography Using Physical Anthropomorphic Phantom (물리적 팬텀을 이용한 CT 촬영 환자의 피폭 선량 측정 및 평가)

  • Jang, Ki-Won;Lee, Choon-Sik;Kwon, Jung-Wan;Lee, Jai-Ki
    • Journal of Radiation Protection and Research
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    • v.30 no.3
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    • pp.113-119
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    • 2005
  • The computed tomogrpahy(CT) provides a high quality in images of human body but contributes to the relatively high patient dose. The frequency of CT examination is increasing and, therefore, the concerns about the patient dose are also increasing. In this study the experimental determination of patient dose was performed by using a physical anthropomorphic phantom and thermoluminescent dosimeter(TLD). The measurements were done for the both axial and spiral scan mode. As a result the effective doses for each scan mode were 17.78mSv and 10.01 mSv respectively and the fact that the degree of the reduction in the patient dose depends on the pitch scan parameter was confirmed. The measurement methods suggested in this study can be applied for the reassessment of the patient dose when the technique in CT equipment is developed or the protocol for CT scanning is changed.

Dose estimation of cone-beam computed tomography in children using personal computer-based Monte Carlo software (PCXMC 소프트웨어를 이용한 소아에서의 CBCT 환자선량 평가)

  • Kim, Eun-Kyung
    • The journal of the Korean dental association
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    • v.58 no.7
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    • pp.388-397
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    • 2020
  • Objective: The purpose of the study was to calculate the effective and absorbed organ doses of cone-beam computed tomography (CBCT) in pediatric patient using personal computer-based Monte Carlo (PCXMC) software and to compare them with those measured using thermoluminescent dosimeters (TLDs) and anthropomorphic phantom. Materials and Methods: Alphard VEGA CBCT scanner was used for this study. A large field of view (FOV) (20.0 cm × 17.9 cm) was selected because it is a commonly used FOV for orthodontic analyses in pediatric patients. Ionization chamber of dose-area product (DAP) meter was located at the tube side of CBCT scanner. With the clinical exposure settings for a 10-year-old patient, DAP value was measured at the scout and main projection of CBCT. Effective and absorbed organ doses of CBCT at scout and main projection were calculated using PCXMC and PCXMCRotation software respectively. Effective dose and absorbed organ doses were compared with those obtained by TLDs and a 10-year-old child anthropomorphic phantom at the same exposure settings. Results: The effective dose of CBCT calculated by PCXMC software was 292.6 μSv, and that measured using TLD and anthropomorphic phantom was 292.5 μSv. The absorbed doses at the organs largely contributing to effective dose showed the small differences between two methods within the range from -18% to 20%. Conclusion: PCXMC software might be used as an alternative to the TLD measurement method for the effective and absorbed organ dose estimation in CBCT of large FOV in pediatric patients.

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Measurement of Radiation Dose of HR CT and Low Dose CT by using Anthropomorphic Chest Phantom and Glass Dosimetry (인체등가형 흉부팬텀과 유리선량계를 이용한 고해상력 및 저선량 CT의 선량측정)

  • Kweon, Dae Cheol
    • Journal of the Korean Society of Radiology
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    • v.13 no.7
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    • pp.933-939
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    • 2019
  • The purpose of this study is to provide basic clinical data by evaluating images, measuring absorbed dose and effective dose by using high resolution CT and low dose CT by using anthropomorphic chest phantom and glass dosimeter. Tissue dose was measured by inserting a glass dosimeter into the anthropomorphic chest phantom. A 64-slice CT system (SOMATOM Sensation 64, Siemens AG, Forchheim, Germany) and CARE Dose 4D were used, and the parameters of the high resolution CT were 120 kVp, Eff. Scan parameters of mAs 104, scan time 7.93 s, slice 1.0 mm (Acq. 64 × 0.6 mm), convolution kernel (B60f sharp) were used, and low dose CT was 120 kVp, Eff. mAs 15, scan time 7.41 s, slice 3.0 mm (Acq. 64 × 0.6 mm), scan of convolution kernel B50f medium sharp. CTDIvol was measured at 8.01 mGy for high resolution CT and 1.18 mGy for low dose CT. Low dose CT scans showed 85.49% less absorbed dose than high resolution CT scans.

Evaluation of Image Quality Using CT Attenuation Correction in SPECT/CT (SPECT/CT에서 CT감쇠보정에 따른 영상의 질 평가)

  • Cho, Sung Wook;Kim, Gye Hwan;Sung, Yong Joon;Lee, Hyung Jin;Kim, Jin Eui
    • The Korean Journal of Nuclear Medicine Technology
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    • v.17 no.2
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    • pp.78-83
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    • 2013
  • Purpose: SPECT/CT, a combination of SPECT and CT, is capable of expressing the results of attenuation correction on images biased by automatic program. As a result, this research evaluates the usefulness of images with CT attenuation correction, using various phantoms and images of patients. Materials and Methods: From July of 2012 to September of 2012, this research was conducted on the contrast, spatial resolution, and images of patients. We studied the contrast with IEC body phantom and Jaszczak phantom, while the spatial resolution was evaluated with NEMA triple line phantom. Further, a comparative study was carried out on the quality of the images, on the difference between the images before and after the CT attenuation correction. Results: Compared the differences between the contrast before and after the CT attenuation correction in IEC body phantom. The contrast was improved by 33.6% at minimum, 89.8% at maximum. In case of Jaszczak Phantom, the contrast was enhanced by 9.9% at minimum, 27.8% at maximum. In NEMA Triple line phantom, the resolution was raised by 4.5% in average: 4.4% in horizontal, 4.5% in vertical. In Anthropomorphic Torso Phantom, the perfusion score of the interior wall with the most severe attenuation was measured to be 29.4%. In the experiment carried out on myocardial perfusion SPECT/CT patients, 9% improvement was discovered in the interior wall, where the most dramatic attenuation occurred, after the CT attenuation correction. Conclusion: SPECT/CT proved its clinical usefulness by enabling the acquisition of images with enhanced contrast and spatial resolution compare to the ones resulted from SPECT.

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Calculation of Dose Conversion Coefficients in the Anthropomorphic MIRD Phantom in Broad Unidirectional Beams of Monoenergetic Photons (MIRD 인형팬텀의 넓고 평행한 감마선빔에 대한 선량 환산계수 계산)

  • Chang, Jai-Kwon;Lee, Jai-Ki
    • Journal of Radiation Protection and Research
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    • v.22 no.1
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    • pp.47-58
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    • 1997
  • The conversion coefficients of effective dose per unit air kerma and equivalent dose per unit fluence were calculated by MCNP4A code for antero-posterior(AP) and postero- anterior(PA) incidence of broad, unidirectional beams of photons into anthropomorphic MIRD phantom. Calculations have been performed for 20 monoenergetic photons of energy ranging from 0.03 to 10 MeV. The conversion coefficients showed a good agreement with the corresponding values given in the draft publication of joint task group of ICRP and ICRU within 10%. The deviations may arise from the differences of geometry in the MIRD phantom and the ADAM/EVE phantoms, and the differences in the codes and cross-section data used. Inclusion of a specific oesophagus model results in effective dose slightly different(5% at most) from the effective doses obtained by adopting the equivalent doses for the thymus or pancreas. Deletion of the ULI from the remainder organ appeared not to be significant for the cases of photon dosimetry covered in this study.

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Development of Dose Verification Method for In vivo Dosimetry in External Radiotherapy (방사선치료에서 투과선량을 이용한 체내선량 검증프로그램 개발)

  • Hwang, Ui-Jung;Baek, Tae Seong;Yoon, Myonggeun
    • Progress in Medical Physics
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    • v.25 no.1
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    • pp.23-30
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    • 2014
  • 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.