• Imaging Science in Dentistry
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• 제52권3호
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• pp.283-288
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• 2022

Purpose: This study was conducted to measure the radiation exposure and image quality of various cone-beam computed tomography (CBCT) machines under common clinical conditions and to analyze the correlation between them. Materials and Methods: Seven CBCT machines used frequently in clinical practice were selected. Because each machine has various sizes of fields of view (FOVs), 1 large FOV and 1 small FOV were selected for each machine. Radiation exposure was measured using a dose-area product (DAP) meter. The quality of the CBCT images was analyzed using 8 image quality parameters obtained using a dental volume tomography phantom. For statistical analysis, regression analysis using a generalized linear model was used. Results: Polymethyl-methacrylate (PMMA) noise and modulation transfer function (MTF) 10% showed statistically significant correlations with DAP values, presenting positive and negative correlations, respectively (P<0.05). Image quality parameters other than PMMA noise and MTF 10% did not demonstrate statistically significant correlations with DAP values. Conclusion: As radiation exposure and image quality are not proportionally related in clinically used equipment, it is necessary to evaluate and monitor radiation exposure and image quality separately.

• 한국방사선학회논문지
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• 제13권3호
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• pp.459-464
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• 2019

치과 콘빔 전산화단층 검사 시 갑상선 부위의 방사선 피폭선량을 최소화하기 위하여 보루스 (Bolus)를 이용한 차폐체를 제작하고, 방사선 차폐 효과와 영상의 적정성을 평가하였다. 치과용 콘빔 전산화단층검사장비를 사용하여 치과방사선 두부 팬텀을 대상으로 갑상선의 좌, 우측 부위에 유리선량계를 부착시켜 방사선량을 측정하였다. 차폐체의 두께를 각각 10 mm, 20 mm, 30 mm로 다르게 하여 각 차폐체별로 흡수선량을 측정하여 차폐체를 사용하지 않았을 경우와 비교하였다. 8명의 평가자가 진료영상의 적정성을 여부를 평가하였다. 왼쪽 갑상선 부위에 30 mm Bolus 차폐체를 사용한 경우에는 결과값이 평균 $342.67{\mu}Gy$로 Bolus 차폐체를 사용하지 않고 측정한 결과값의 평균 $431.22{\mu}Gy$보다 20.7% 감소하였고, 오른쪽 갑상선 부위에 30 mm Bolus 차폐체를 사용한 경우에는 평균 $424.56{\mu}Gy$로 21.9%의 선량감소효과를 보였다. 진료 영상의 적정성은 평가자 모두 사용 가능하다 판단하였다. 결론적으로, 치과 콘빔 전산화단층검사 시 갑상선 부위의 방사선 피폭선량을 최소화하기 위해 제작된 Bolus 차폐체는 장해음영 없이 적정한 진단 영상 처리가 가능하고, 방사선차폐 효과가 있어 유용한 차폐체로 적용 가능할 것으로 사료된다.

• Journal of Radiation Protection and Research
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• 제48권1호
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• pp.15-19
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• 2023

Background: Cone beam computed tomography (CBCT) is a specialized medical equipment and plays a significant role in the diagnosis of oral and maxillofacial diseases and abnormalities; however, it is attributed to risk of exposure of ionizing radiation. The aim of the study was to estimate and determine the amount of scattered radiation dose to the thyroid gland in dental CBCT during maxilla and mandible scan. Materials and Methods: The average scattered radiation dose for i-CAT 17-19 Platinum CBCT (Imaging Sciences International) was measured using a Multi-O-Meter (Unfors Instruments), placed at the patient's neck on the skin surface of the thyroid cartilage, with an exposure parameter of 120 kVp and 37.07 mAs. The surface entrance dose was noted using the Multi-O-Meter, which was placed at the time of the scan at the level of the thyroid gland on the anterior surface of the neck. Results and Discussion: The surface entrance dose to the thyroid from both jaws scans was 191.491±78.486 µGy for 0.25 mm voxel and 26.9 seconds, and 153.670±74.041 µGy from the mandible scan, whereas from the maxilla scan the surface entrance dose was 5.259±10.691 µGy. Conclusion: The surface entrance doses to the thyroid gland from imaging of both the jaws, and also from imaging of the maxilla and mandible alone were within the threshold limit. The surface entrance dose and effective dose in CBCT were dependent on the exposure parameters (kVp and mAs), scan length, and field of view. To further reduce the radiation dose, care should be taken in selecting an appropriate protocol as well as the provision of providing shielding to the thyroid gland.

• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.151-159
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• 2021

Background: Computed tomography (CT) is one of the crucial diagnostic tools in modern medicine. However, careful monitoring of radiation dose for CT patients is essential since the procedure involves ionizing radiation, a known carcinogen. Materials and Methods: The most desirable CT dose descriptor for risk analysis is the organ absorbed dose. A variety of CT organ dose calculators currently available were reviewed in this article. Results and Discussion: Key common elements included in CT dose calculators were discussed and compared, such as computational human phantoms, CT scanner models, organ dose database, effective dose calculation methods, tube current modulation modeling, and user interface platforms. Conclusion: It is envisioned that more research needs to be conducted to more accurately map CT coverage on computational human phantoms, to automatically segment organs and tissues for patient-specific dose calculations, and to accurately estimate radiation dose in the cone beam computed tomography process during image-guided radiation therapy.

• 한국방사선학회논문지
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• 제11권3호
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• pp.161-169
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• 2017

방사선 치료 시 자세 확인 촬영을 목적으로 3차원 영상 획득이 가능한 콘빔씨티 촬영이 많이 이용되고 있다. 본 연구에서는 몬테칼로 기법을 이용한 모의실험을 통해 콘빔씨티 촬영 시 피폭선량을 정략적으로 분석하고 표준화된 데이터를 제시하고자 한다. 실험은 MCNPX(ver. 2.5.0)를 이용하였으며, 먼저 콘빔씨티를 모사한 후 광자선 스펙트럼을 분석하였다. 그리고 물 팬텀을 모사하여 깊이별 심부선량 백분율과 흡수선량을 측정하였다. 광자선 스펙트럼을 분석한 결과, 관전압 80 ~ 120 kVp 에서 평균 에너지는 조건에 따라 25.7 ~ 52.6 keV로 나타났으며 특성X선 에너지는 9, 60, 68, 70 keV로 나타났다. 물 팬텀을 사용하여 심부선량 백분율을 측정한 결과 표면에서 최대선량이 나타났으며 깊이가 깊어질수록 감소하는 것으로 나타났다. 흡수선량 또한 깊이가 증가할수록 감소하였으며 팬텀 전체가 받는 흡수선량은 9.7 ~ 18.7 mGy로 나타났다. 이는 일반적으로 방사선 치료에 사용되는 주당 처방선량인 약 10Gy의 0.2%를 차지하는 선량이며 이는 치료효과에는 큰 영향을 미치지 않을 것으로 판단된다. 그러나 처방선량에 비해 미미한 수준일지라도 이를 간과해서는 안 될 것이다.

• 대한방사선치료학회지
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• 제26권2호
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• pp.247-256
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• 2014

목 적 : 췌장 환자 방사선 치료 중 기점(Fiducial) 대상 내부 및 외부 종양 움직임의 오차를 정량화 하고자 한다. 또한 cone beam computed tomography (CBCT) 를 기반으로 호흡 시 췌장의 움직임 분석하고자 한다. 대상 및 방법 : 용적 세기변조 회전조사 (V-MAT)를 적용, 정위적 방사선 치료를 국소 진행성 췌장암 환자 11명을 대상으로 하였다. CBCT 및 직교 투시이미지를 적용하여 기점(Fiducial Marker)의 Inter, intra-fraction 움직임 변화를 치료 전, 치료 진행 시 분석하였다. 결 과 : 치료 후 프로토콜을 오프라인 교정 프로토콜을 사용하여, CBCT 와 직교투시 간의 평균 오차(범위)는 0.0(-1.7~4.0), 0.3(-0.5~3.0) and 0.0(-4.1~6.6)mm 측방 (LR), 세로 (AP) 및 종 방향 (SI) 이였다. 무작위 Inter-fraction Setup 오차 결과는 -0.1, -2.3 and -1.1 mm: 95% Fiducial포함 마진은 각 9.9, 7.8, 12.5mm로 수식되었다. 결 론 : 위 분석으로 뼈 일치 정렬 후 잔류 불확실성이 있으며, SI 방향에 큰 임의의 움직임은 적합한 여백이 필요하다. 주변 내부 장기를 보호, 내부 장기 문제점을 최소화, 호흡편차를 고려, 치료 시 정기적으로 측정하여야 한다.

• Imaging Science in Dentistry
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• 제50권4호
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• pp.291-298
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• 2020

Purpose: The detection and exact localization of penetrating foreign bodies are crucial for the appropriate management of patients with dentoalveolar trauma. This study compared the efficacy of cone-beam computed tomography (CBCT) and spiral computed tomography (CT) scans for the detection of different foreign bodies composed of 5 frequently encountered materials in 2 sizes. The effect of the location of the foreign bodies on their visibility was also analyzed. Materials and Methods: In this in vitro study, metal, tooth, stone, glass, and plastic particles measuring 1×1×1 mm and 2×2×2 mm were prepared. They were implanted in a sheep's head in the tongue muscle, nasal cavity, and at the interface of the mandibular cortex and soft tissue. CBCT and spiral CT scans were taken and the visibility of foreign bodies was scored by 4 skilled maxillofacial radiologists who were blinded to the location and number of foreign bodies. Results: CT and CBCT were equally accurate in visualizing metal, stone, and tooth particles of both sizes. However, CBCT was better for detecting glass particles in the periosteum. Although both imaging modalities visualized plastic particles poorly, CT was slightly better for detecting plastic particles, especially the smaller ones. Conclusion: Considering the lower patient radiation dose and cost, CBCT can be used with almost equal accuracy as CT for detecting foreign bodies of different compositions and sizes in multiple maxillofacial regions. However, CT performed better for detecting plastic particles.

• 대한방사선치료학회지
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• 제28권2호
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• pp.123-130
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• 2016

목 적 : Computerized imaging reference systems 동적팬텀을이용한 cone-beamcomputed tomography(CBCT) 영상과 four-dimensionalcomputed tomography(4DCT) 영상의 체적을 비교분석 하고자 한다. 대상 및 방법 : 동적팬텀 내에 직경 1, 2, 3 cm 노드를 각각 삽입하고, CT simulator와 TruebeamSTx X-ray Imaging system을 이용하여 4DCT 영상과 CBCT 영상을 얻었다. 4DCT 영상은 maximum intensity projection(MIP), minimum intensity projection(MinIP), 그리고 average intensity projection(AVG)영상으로 재구성 하고 노드의 체적은 Eclipse system의 CT ranger tool로 CT number를 설정하여 측정하였다. 결 과 : CBCT를 기준으로 노드1, 2, 3 cm의 체적을 비교하였을 때 4DCT의 MIP는 0.54~2.33, 5.16~8.06, 9.03~20.11 ml, MinIP는 0.00~1.48, 0.00~8.47, 1.42~24.85 ml, AVG는 0.00~1.17, 0.00~2.19, 0.04~3.35 ml의 차이를 보였다. 결 론 : 노드의 체적을 비교한 결과 CBCT 영상은 4DCT의 AVG 영상과 유사한 것으로 확인되었다.

• 한국의학물리학회지:의학물리
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• 제32권1호
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• pp.1-17
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• 2021

The evolution of X-ray computed tomography (CT) has been based on the discovery of X-rays, the inception of the Radon transform, and the development of X-ray digital data acquisition systems and computer technology. Unlike conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation coefficients (approximate tissue density) for almost every region in the body. This article reviews the essential physical principles and technical aspects of the CT scanner, including several notable evolutions in CT technology that resulted in the emergence of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positron-emission-tomography-CT and single-photon-emission-computed-tomography-CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses.

• Imaging Science in Dentistry
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• 제48권2호
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• pp.103-109
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• 2018

Purpose: To analyze cone-beam computed tomography (CBCT) use, indications, and exposure parameters in San $Jos{\acute{e}}$, Costa Rica. Materials and Methods: A cross-sectional study was performed. All CBCT examinations over a period of 6 months at 2 radiological centers in San $Jos{\acute{e}}$, Costa Rica were evaluated. The examinations were performed with Veraview EPOC X550 and Veraviewepocs 3D R100 equipment. The patients' age and sex, clinical indication for CBCT, region of interest (ROI), repeat examinations, specialty of the referring dentist, field-of-view (FOV), tube voltage (kV), tube current (mA), and radiation dose (${\mu}Gy$) were evaluated. Patients were classified by age as children (${\leq}12years$), adolescents(13-18 years), and adults(${\geq}19years$). Results: The mean age of the 526 patients was 49.4 years. The main indications were implant dentistry and dental trauma. The most frequent ROIs were posterior, while anterior ROIs were much less common. The highest percentage of repeat examinations was in children. Fifty-six percent of the referring dentists were specialists. The most commonly used FOV was small. The mean tube voltage and current were 79.8 kV and 7.4 mA for Veraview EPOC X550 and 89.9 kV and 6 mA for Veraviewepocs 3D R100, respectively. The mean doses for children, adolescents, and adults were $6.9{\mu}Gy$, $8.4{\mu}Gy$, and $7.8{\mu}Gy$, respectively. Conclusion: Although CBCT was most commonly used in adults for implant dentistry, most repeat examinations were in children, and the highest mean dose was in adolescents. Additional dose optimization efforts should be made by introducing low-dose protocols for children and adolescents.