• 한국방사선학회논문지
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• 제14권5호
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• pp.613-618
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• 2020

간동맥화학색전술 중 사용되고 있는 Fast Low Dose C-arm CT의 평균선량을 DSA의 평균선량과 비교해 보고, 전체 누적선량에서 검사기법별 평균선량 분석을 통해 피폭선량을 분석해 보았다. 본원에서 환자 50명을 임의로 선정하여 Fast Low Dose C-arm CT와 DSA의 DAP 및 Air Kerma를 조사하여 비교하였으며, 4가지 검사기법(DSA, Fast Low Dose C-arm CT, Roadmap, Fluoroscopy)의 누적선량(DAP, Air Kerma)이 차지하는 비율을 분석하였다. 통계적인 비교 분석을 위해 통계프로그램 SPSS 20.0을 이용하여 대응표본 T검정, ANOVA 검증(post hoc test : Tukey)하였다. Fast Low Dose C-arm CT가 DSA에 비해 평균선량(DAP, Air Kerma)이 통계적으로 유의하게 낮았다.(p<.001) 간동맥화학색전술에서 항암제 주입 전후로 Fast Low Dose C-arm CT를 적극 활용하여 DSA의 검사 횟수를 줄인다면 환자의 의료방사선 피폭을 감소시킬 수 있다.

• Imaging Science in Dentistry
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• 제40권1호
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• pp.15-23
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• 2010

Purpose : This study was designed to compare the effective doses from low-dose and standard-dose multi-detector CT (MDCT) scanning protocols and evaluate the image quality and the spatial resolution of the low-dose MDCT protocols for clinical use. Materials and Methods : 6-channel MDCT scanner (Siemens Medical System, Forschheim, Germany), was used for this study. Protocol of the standard-dose MDCT for the orthodontic analysis was 130 kV, 35 mAs, 1.25 mm slice width, 0.8 pitch. Those of the low-dose MDCT for orthodontic analysis and orthodontic surgery were 110 kV, 30 mAs, 1.25 mm slice width, 0.85 pitch and 110 kV, 45 mAs, 2.5 mm slice width, 0.85 pitch. Thermoluminescent dosimeters (TLDs) were placed at 31 sites throughout the levels of adult female ART head and neck phantom. Effective doses were calculated according to ICRP 1990 and 2007 recommendations. A formalin-fixed cadaver and AAPM CT performance phantom were scanned for the evaluation of subjective image quality and spatial resolution. Results : Effective doses in ${\mu}Sv$ ($E_{2007}$) were 699.1, 429.4 and 603.1 for standard-dose CT of orthodontic treatment, low-dose CT of orthodontic analysis, and low-dose CT of orthodontic surgery, respectively. The image quality from the low-dose protocol were not worse than those from the standard-dose protocol. The spatial resolutions of both standard-dose and low-dose CT images were acceptable. Conclusion : From the above results, it can be concluded that the low-dose MDCT protocol is preferable in obtaining CT images for orthodontic analysis and orthodontic surgery.

• 한국방사선학회논문지
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• 제17권7호
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• pp.1033-1039
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• 2023

폐 스크리닝 검사로 이용되고 있는 저선량 흉부 CT는 Scan 범위 내에 관상동맥 석회화에 대한 정보도 함께 포함하고 있어 이를 이용한 관상동맥 석회화 판별의 유용성을 알아보고자 한다. 저선량 흉부 CT 검사와 관상동맥 석회화 점수(CACS) 검사를 같은 날 시행 받은 자들을 대상으로 하였다. 관상동맥 석회화 점수 검사 결과를 Coronary artery calcium score categories and risks 분류법을 참고하여 4개 그룹(Low: 1〈CACS〈10, Mild: 10〈CACS〈100, Moderate: 100〈CACS〈400, High: 400〈CACS)으로 각각 30명을 선정한 후 관상동맥 석회화 수치 측정 업무에 종사하고 있는 경력 15년차 이상 5명의 방사선사가 저선량 흉부 CT 영상에서 관상동맥 석회화 유무를 후향적으로 분석하였다. 저선량 흉부 CT 영상에서 5명의 관찰자가 통일되게 판독한 결과가 관상동맥 석회화점수 CT 검사 결과와 일치한 경우는 Low 그룹: 56%, Mild 그룹: 96.6%, Moderate 그룹: 100%, High 그룹: 100%로 나타났다. Low 그룹에서 5명의 관찰자 모두가 석회화를 관찰한 것은 30건 중 17건이었으며, 5명이 모두 판별 불가로 결정한 경우 7건이었다. 무증상 성인을 대상으로 저선량 흉부 CT 검사에서 석회화 점수가 15 이상인 경우에는 관상동맥 석회화를 100% 관찰할 수 있었다. 판별이 가능한 최소 석회화 수치는 1로, 피검자의 체형이 작거나 심장의 움직임이 최소가 되는 시점에서 스캔이 이루어지는 경우 매우 작은 석회화까지도 판별할 수 있다는 것을 알 수 있었다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권7호
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• pp.3465-3468
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• 2016

Background: Fluorodeoxyglucose ($^{18}FDG$) PET/CT imaging has become an important component of the management paradigm in oncology. However, the significant imparted radiation exposure is a matter of growing concern especially in younger populations who have better odds of survival. The aim of this study was to estimate the effective dose received by patients having whole body $^{18}F$-FDG PET/CT scanning as per recent dose reducing guidelines at a tertiary care hospital. Materials and Methods: This prospective study covered 63 patients with different cancers who were referred for PET/CT study for various indications. Patients were prepared as per departmental protocol and 18FDG was injected at 3 MBq/Kg and a low dose, non-enhanced CT protocol (LD-NECT) was used. Diagnostic CT studies of specific regions were subsequently performed if required. Effective dose imparted by 18FDG (internal exposure) was calculated by using multiplying injected dose in MBq with coefficient $1.9{\times}10^{-2}mSv/MBq$ according to ICRP publication 106. Effective dose imparted by CT was calculated by multiplying DLP (mGy.cm) with ICRP conversion coefficient "k" 0.015 [mSv / (mG. cm)]. Results: Mean age of patients was $49{\pm}18$ years with a male to female ratio of 35:28 (56%:44%). Median dose of 18FDG given was 194 MBq (range: 139-293). Median CTDIvol was 3.25 (2.4-6.2) and median DLP was 334.95 (246.70 - 576.70). Estimated median effective dose imparted by $^{18}FDG$ was 3.69 mSv (range: 2.85-5.57). Similarly the estimated median effective dose by low dose (non-diagnostic) CT examination was 4.93 mSv (range: 2.14 -10.49). Median total effective dose by whole body 18FDG PET plus low dose non-diagnostic CT study was 8.85 mSv (range: 5.56-13.00). Conclusions: We conclude that the median effective dose from a whole body 18FDG PET/CT in our patients was significantly low. We suggest adhering to recently published dose reducing strategies, use of ToF scanner with CT dose reducing option to achieve the lower if not the lowest effective dose. This would certainly reduce the risk of second primary malignancy in younger patients with higher odds of cure from first primary cancer.

• 방사선산업학회지
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• 제11권3호
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• pp.131-137
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• 2017

To compare the radiation dose and image noise of low dose computed tomography (CT) and high resolution CT using the fixed tube current technique and automatic tube current modulation (CARE Dose 4D). Chest CT and human anthropomorphic phantom were used the RPL (radiophotoluminescence) dosimeters. For image evaluation, standard deviation of mean CT attenuation coefficient and CT attenuation coefficient was measured using ROI analysis function. The effective dose was calculated using CTDIvol and DLP. CARE Dose 4D was reduced by 74.7% and HRCT by 64.4% compared to the fixed tube current technique in low dose CT of chest phantom. In CTDIvol and DLP, the dose of CARE Dose 4D was reduced by fixed tube current technique. For effective dose, CARE Dose 4D was reduced by 47% and HRCT by 46.9% compared to the fixed tube current method, and the dose of CARE Dose 4D was significantly different (p<.05). Noise in the image was higher than that in the fixed tube current technique. Noise difference in the image of CARE Dose 4D in low dose CT was significant (p<.05). The low radiation dose and the noise difference of the CARE Dose 4D were compared with the fixed tube current technique in low dose CT and HRCT using chest phantom. The radiation doses using CARE Dose 4D were in accordance with the national and international dose standards. CARE Dose 4D should be applied to low dose CT and HRCT for clinical examination.

• 한국방사선학회논문지
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• 제13권7호
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• pp.933-939
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• 2019

MDCT에서 인체등가형 흉부팬텀과 유리선량계를 이용하여 고해상력 및 저선량 CT로 검사하여 영상의 평가 및 흡수선량 및 유효선량을 측정하여 임상 기초자료를 제공하는데 목표를 두고자한다. 인체등가형 흉부팬텀내부에 유리선량계를 삽입하여 조직선량을 측정하였다. 64-slice CT system (SOMATOM Sensation 64, Siemens AG, Forchheim, Germany)과 CARE Dose 4D를 이용하였고, 고해상력 CT에서의 파라메터는 관전압 120 kVp, Eff. mAs 104, scan time 7.93 sec, slice 1.0 mm (Acq. 64×0.6 mm), convolution kernel (B60f sharp)의 스캔 파라메터가 사용되었고, 저선량 CT는 120 kVp, Eff. mAs 15, scan time 7.41 sec, slice 3.0 mm (Acq. 64×0.6 mm), convolution kernel B50f medium sharp의 스캔하였다. 인체등가형 흉부팬텀을 이용하여 스캔에 따른 CTDIvol은 고해상력 CT에서 8.01 mGy, 저선량 CT는 1.18 mGy로 측정되었다. 저선량 CT 검사는 고해상력 CT 검사에 비해 흡수선량이 85.49%가 감소하였고 영상의 차이는 없어 임상에서 유용하게 적용할 수 있다.

• 한국방사선학회논문지
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• 제15권2호
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• pp.117-123
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• 2021

본 논문에서는 흉부 저선량 CT와 복부 비조영 CT에서 선량기록을 바탕으로 환자선량에 영향을 줄 수 있는 요인과 상관관계를 확인하여 실질적인 선량 감소 방안의 근거를 마련하고자 하였다. 흉부 저선량 CT와 복부 비조영 CT 검사 시 불필요하게 피폭이 발생하는 원인을 찾기 위해 7가지 요인(나이, 성별, 키, 몸무게, BMI, 환자 상태 (입원, 외래), dose modulation 활성화 유무)과 CT 선량과의 상관관계를 확인하였다. 상관관계 확인을 위해 사용된 통계기법으로는 로지스틱 회귀분석을 사용하였다. 흉부 저선량 CT 검사에서는 키가 클수록, BMI 가 높을수록, dose modulation을 비활성화한 경우에 진단참고수준 (diagnostic reference levels, DRL) 기준치의 초과 위험률이 낮아졌다 (odds ration<1; p<0.05). 또한 여성의 경우와 몸무게가 클수록 DRL 기준치의 초과 위험률이 높아졌다 (odds ration>1; p<0.05). 복부 비조영 CT 검사에서는 몸무게가 클수록, dose modulation을 비활성화한 경우에 DRL 기준치의 초과 위험률이 낮아졌다 (odds ration<1; p<0.05). 이처럼 방사선 피폭에 영향을 주는 다양한 요인에 대한 연구를 수행하여 환자 선량과의 연관성을 찾고 이에 따른 선량을 낮추는 노력이 필요할 것으로 사료된다.

• 한국의학물리학회지:의학물리
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• 제28권1호
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• pp.27-32
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• 2017

We investigated the effect of a commercial iterative reconstruction technique (iDose, Philips) on the image quality and the dose calculation for the treatment plan. Using the electron density phantom, the 3D CT images with five different protocols (50, 100, 200, 350 and 400 mAs) were obtained. Additionally, the acquired data was reconstructed using the iDose with level 5. A lung phantom was used to acquire the 4D CT with the default protocol as a reference and the low dose (one third of the default protocol) 4D CT using the iDose for the spine and lung plans. When applying the iDose at the same mAs, the mean HU value was changed up to 85 HU. Although the 1 SD was increased with reducing the CT dose, it was decreased up to 4 HU due to the use of iDose. When using the low dose 4D CT with iDose, the dose change relative to the reference was less than 0.5% for the target and OARs in the spine plan. It was also less than 1.1% in the lung plan. Therefore, our results suggests that this dose reduction technique is applicable to the 4D CT image acquisition for the radiation treatment planning.

• Imaging Science in Dentistry
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• 제53권1호
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• pp.69-75
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• 2023

Purpose: Maxillofacial trauma predominantly affects young adults between 20 and 40 years of age. Although radioprotection is a legal requirement, the significant potential of dose reduction in computed tomography (CT) is still underused in the clinical routine. The objective of this study was to evaluate whether maxillofacial fractures can be reliably detected and classified using ultra-low-dose CT. Materials and Methods: CT images of 123 clinical cases with maxillofacial fractures were classified by two readers using the AOCOIAC software and compared with the corresponding results from post-treatment images. In group 1, consisting of 97 patients with isolated facial trauma, pre-treatment CT images at different dose levels (volumetric computed tomography dose index: ultra-low dose, 2.6 mGy; low dose, <10 mGy; and regular dose, <20 mGy) were compared with post-treatment cone-beam computed tomography (CBCT). In group 2, consisting of 31 patients with complex midface fractures, pre-treatment shock room CT images were compared with post-treatment CT at different dose levels or CBCT. All images were presented in random order and classified by 2 readers blinded to the clinical results. All cases with an unequal classification were re-evaluated. Results: In both groups, ultra-low-dose CT had no clinically relevant effect on fracture classification. Fourteen cases in group 2 showed minor differences in the classification code, which were no longer obvious after comparing the images directly to each other. Conclusion: Ultra-low-dose CT images allowed the correct diagnosis and classification of maxillofacial fractures. These results might lead to a substantial reconsideration of current reference dose levels.

• 한국콘텐츠학회논문지
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• 제14권1호
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• pp.356-363
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• 2014

소아 CT 촬영시 피폭선량을 저감시킬 수 있는 조건을 찾기 위하여 pediatric phantom을 이용하여 소아 방사선량을 비교 분석하였다. 관전류변동제어(tube current modulation:TCM) 방식과 low dose CT protocol(LDCTP)에 따라 소아 검사를 시행하였으며, 검사는 brain, chest, abdomen-pelvis 부위를 전산화 단층촬영 장치를 이용한 3개의 검사 프로토콜을 사용하였다. 거의 모든 MDCT 장치는 volume CT dose index(CTDIvol), dose length product(DLP)와 유효선량 평가 결과를 기록, 보관하고 있으며, 이러한 정보들은 환자들의 방사선 노출 및 위험도를 평가하는 데 필수적이다. 방사선 노출 위험도를 감소시키기 위해서 적정화 및 정당화 원칙을 반드시 준수해야 한다. 관전압(kV)에 따른 TCM 방식을 사용하였을 경우 kV가 낮아질수록 유효선량이 낮아지는 경향을 나타내었으며, low dose CT protocol을 사용한 경우가 유효선량이 상대적으로 더 적은 것을 알 수 있었다. 또한 평균 유효선량은 brain, chest, abdomen-pelvis CT의 결과가 독일의 reference dose 보다 각각 47%, 13.8%, 25.7%로 더 낮게 나타났고. 영국의 reference dose와 비교해도 55.7%, 10.2%, 43.6%에 불과했다. 결론적으로 선량 감소를 위해 주의할 것은 body-weight based tube current adaption을 포함한 TCM, 그리고 LDCTP 등 모든 선량 감소 방안을 이용하여야 한다.