• Imaging Science in Dentistry
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• v.53 no.2
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• pp.127-135
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• 2023

Purpose: This study assessed the intensity of artifacts produced by 2 metal posts, 2 cements, and different exposure parameters using 2 cone-beam computed tomography (CBCT) units. Materials and Methods: The sample was composed of 20 single-rooted premolars, divided into 4 groups: Ni-Cr/zinc phosphate, Ni-Cr/resin cement, Ag-Pd/zinc phosphate, and Ag-Pd/resin cement. Samples were scanned before and after post insertion and cementation using a CS9000 3D scanner with 4 exposure parameters (85/90 kV and 6.3/10 mA) and an i-CAT scanner with 120 kV and 5 mA. The presence of artifacts was assessed subjectively by 2 observers and objectively by a trained observer using ImageJ software. The Mann-Whitney, Wilcoxon, weighted kappa, and chi-square tests were used to assess data at a 95% confidence level(α<0.05). Results: In the subjective analyses, AgPd presented more hypodense and hyperdense lines than NiCr (P<0.05), and more hypodense halos were found using i-CAT (P<0.05) than using CS9000 3D. More hypodense halos, hypodense lines, and hyperdense lines were observed at 10 mA than at 6.3 mA (P<0.05). More hypodense halos were observed at 85 kV than at 90 kV (P<0.05). CS9000 3D presented more hypodense and hyperdense lines than i-CAT (P<0.05). In the objective analyses, AgPd presented higher percentages of hyperdense and hypodense artifacts than NiCr (P<0.05). Zinc phosphate cement presented higher hyperdense artifact percentages on CS9000 3D scans(P<0.05). CS9000 3D presented higher artifact percentages than i-CAT(P<0.05). Conclusion: High-atomic-number alloys, higher tube current, and lower tube voltage may increase the artifacts present in CBCT images.

• Radiation Oncology Journal
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• v.24 no.4
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• pp.294-299
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• 2006

$\underline{Purpose}$: Using cone beam CT, we can compare the position of the patients at the simulation and the treatment. In on-line image guided radiation therapy, one can utilize this compared data and correct the patient position before treatments. Using cone beam CT, we investigated the errors induced by setting up the patients when use only the markings on the patients' skin. $\underline{Materials\;and\;Methods}$: We obtained the data of three patients that received radiation therapy at the Department of Radiation Oncology in Chung-Ang University during August 2006 and October 2006. Just as normal radiation therapy, patients were aligned on the treatment couch after the simulation and treatment planning. Patients were aligned with lasers according to the marking on the skin that were marked at the simulation time and then cone beam CTs were obtained. Cone beam CTs were fused and compared with simulation CTs and the displacement vectors were calculated. Treatment couches were adjusted according to the displacement vector before treatments. After the treatment, positions were verified with kV X-ray (OBI system). $\underline{Results}$: In the case of head and neck patients, the average sizes of the setup error vectors, given by the cone beam CT, were 0.19 cm for the patient A and 0.18 cm for the patient B. The standard deviations were 0.15 cm and 0.21 cm, each. On the other hand, in the case of the pelvis patient, the average and the standard deviation were 0.37 cm and 0.1 cm. $\underline{Conclusion}$: Through the on-line IGRT using cone beam CT, we could correct the setup errors that could occur in the conventional radiotherapy. The importance of the on-line IGRT should be emphasized in the case of 3D conformal therapy and intensity-modulated radiotherapy, which have complex target shapes and steep dose gradients.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.21-21
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• 2018

다양한 소재(금속, 세라믹, 고분자 소재 등)들이 3차원 형상기반 적층제조법에 적용되고 있는데, 금속 소재를 이용하여 3D 프린팅 법으로 치과용 수복물을 제조하는 연구가 많이 보고되고 있다. 하지만, 티타늄 또는 티타늄 합금 분말을 이용하여 3D 프린팅 법으로 제작한 치과용 보철물에 관한연구 보고는 많지 않다. Kanazawa 등 (2014)은 Ti-6Al-4V 합금분말을 이용하여 SLM법으로 총의치 용 framework를 제작하여 주조법으로 제작한 것과 비교 평가하였고, Mangano 등(2013)은 Ti-6Al-4V 합금분말로 지름이 작은 일체형 (1-piece narrow-diameter) 임플란트를 SLS법으로 제작하여 16명의 환자에게 식립한 다음, 2년간 관찰하였고, Mangano 등 (2014)은 cone-beam computed tomography (CBCT) data를 3D이미지로 변환시켜 DLMS법으로 치근 형상의 임플란트를 제작하여 15명의 환자에게 식립한 다음, 1년간 관찰하였다. 또한 서울대학교 및 연세대학교 치과생체재료과학교실 (2016)에서는 3D 프린팅 법으로 제작한 티타늄 시편과 기계 가공한 티타늄 시편의 물성을 비교하였다. 그러나 티타늄 합금 분말을 이용하여 3D 프린팅 법으로 제작한 치과용 보철물을 실제 임상에 적용하는 단계에서 기존 기계가공 방식으로 제작한 티타늄 보철물과 3D 프린팅 법으로 제작한 티타늄 보철물의 물성과 표면특성을 다양하게 비교 평가하는 것이 필요하여 본 연구에서는 3D 프린팅 법으로 제작한 티타늄 시편과 기계 가공한 티타늄 시편의 물성특성과 표면특성을 비교하여 조사하였다.

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.255-262
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• 2014

During image-guided radiation therapy, the patient is exposed to unwanted radiation from imaging devices built into the medical LINAC. In the present study, the effective dose delivered to a patient from a cone beam computed tomography (CBCT) machine was measured. Absorbed doses in specific organs listed in ICRP Publication 103 were measured with glass dosimeters calibrated with kilovolt (kV) X-rays using a whole body physical phantom for typical radiotherapy sites, including the head and neck, chest, and pelvis. The effective dose per scan for the head and neck, chest, and pelvis were $3.37{\pm}0.29$, $7.36{\pm}0.33$, and $4.09{\pm}0.29$ mSv, respectively. The results highlight the importance of the compensation of treatment dose by managing imaging dose.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.20
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• pp.9033-9038
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• 2014

Background: The purpose of this study was to assess the feasibility of deep inspiration breath-hold (DIBH) based volumetric modulated arc therapy (VMAT) for locally advanced left sided breast cancer patients undergoing radical mastectomy. DIBH immobilizes the tumor bed providing dosimetric benefits over free breathing (FB). Materials and Methods: Ten left sided post mastectomy patients were immobilized in a supine position with both the arms lifted above the head on a hemi-body vaclock. Two thermoplastic masks were prepared for each patient, one for normal free breathing and a second made with breath-hold to maintain reproducibility. DIBH CT scans were performed in the prospective mode of the Varian real time position management (RPM) system. The planning target volume (PTV) included the left chest wall and supraclavicular nodes and PTV prescription dose was 5000cGy in 25 fractions. DIBH-3DCRT planning was performed with the single iso-centre technique using a 6MV photon beam and the field-in-field technique. VMAT plans for FB and DIBH contained two partial arcs ($179^{\circ}-300^{\circ}CCW/CW$). Dose volume histograms of PTV and OAR's were analyzed for DIBH-VMAT, FB-VMAT and DIBH-3DCRT. In DIBH mode daily orthogonal ($0^{\circ}$ and $90^{\circ}$) KV images were taken to determine the setup variability and weekly twice CBCT to verify gating threshold level reproducibility. Results: DIBH-VMAT reduced the lung and heart dose compared to FB-VMAT, while maintaining similar PTV coverage. The mean heart $V_{30Gy}$ was $2.3%{\pm}2.7$, $5.1%{\pm}3.2$ and $3.3%{\pm}7.2$ and for left lung $V_{20Gy}$ was $18.57%{\pm}2.9$, $21.7%{\pm}3.9$ and $23.5%{\pm}5.1$ for DIBH-VMAT, FB-VMAT and DIBH-3DCRT respectively. Conclusions: DIBH-VMAT significantly reduced the heart and lung dose for left side chest wall patients compared to FB-VMAT. PTV conformity index, homogeneity index, ipsilateral lung dose and heart dose were better for DIBH-VMAT compared to DIBH-3DCRT. However, contralateral lung and breast volumes exposed to low doses were increased with DIBH-VMAT.