Fast Low Dose C-arm CT와 DSA의 선량 비교

김찬우(Chan-woo Kim),김재석(Jae-Seok Kim) 한국방사선학회 2020 한국방사선학회 논문지 Vol.14 No.5

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. The average dose of Fast Low Dose C-arm CT used during hepatic arterial chemoembolization was compared with the average dose of DSA, and the exposure dose was analyzed by analyzing the average dose for each test technique in the total accumulated dose. 50 patients were randomly selected at our clinic and compared with Fast Low Dose C-arm CT, DAP and Air Kerma of DSA, and the accumulation of four test techniques (DSA, Fast Low Dose C-arm CT, Roadmap, Fluoroscopy) The proportion of dose (DAP, Air Kerma) was analyzed. For statistical comparative analysis, the corresponding sample T test and ANOVA test (post hoc test: Tukey) were performed using the statistical program SPSS 20.0. Fast Low Dose C-arm CT showed statistically significantly lower average dose (DAP, Air Kerma) than DSA. Reducing the number of tests for DSA can reduce the patient s exposure to medical radiation.

Urography CT에서 Low dose protocol 사용시 선량 감소 효과에 관한 연구

김기범(Ki Bum Kim),이상우(Sang woo Lee) 대한CT영상기술학회 2013 대한CT영상기술학회지 Vol.15 No.1

목적 : CT 검사 중 다소 긴 시간과, 여러 phase를 가진 Urography CT 검사에서의 과거 조건과, low dose를 사용한 현재의 조건에서의 환자의 주요장기의 직접적인 선량을 비교하고, 이에 따른 noise를 측정, 임상의 유용성을 평가해보고자 한다. 대상 및 방법 : 본원에서 Urography CT검사로 follow-up 시행하는 총 20명의 환자를 대상으로 진행하였고, 사용된 장비는 64-MDCT Light Speed VCT Xte(USA), Rando phantom(Model ART-200-5 Fluke Biomedical) 그리고 Glass Dosimetry System(Dose Ace FGD-1000, GD-352M, Asahi Techno Glass Corporation Shizuoka, Japan)을 사용하여 실험하였다. Noise 분석은Image J- software(version 1.46r, National Institutes of Health, USA)를 통하여 SD값을 도출하였다. 이전의 기존 protocol과 low dose 조건을 사용한 현재의 protocol 로 각각 CTDIvol, DLP값을 비교 및 통계분석하고, 유리선량계를 Rando phantom의 비뇨기계 중요장기 부위에 직접 삽입하여 선량을 산출하였다. 결과 : 본 연구에서의 방사선 피폭선량에 대한 비교는 환자를 대상으로 한 통계치에서 CTDIvol은 평균 41%, DLP값은 49% 감소하였고, phantom을 사용하여 시행한 실험에서는 CTDIvol은 12%, 그리고 DLP값은 24%의 감소를 확인할 수 있었다. 중요장기부위의 선량계를 직접 삽입하여 산출해낸 부분 흡수선량은 오른 신장은 41%, 왼 신장은 42% 크게 감소하였고, 요관과 방광에서는 각각 0.5%, 4%의 증가를 보였다. 다른 비교대상인 software를 이용한 noise 측정에서는unenhanced phase에서는 33%의 큰 증가를 보였지만, low dose를 적용한 enhanced abdomen pelvis와 excretory phase에서는 증가를 보였다. 결론 : 환자의 피폭선량에는 큰 변화를 주었지만, mAs 감소로 인한 noise가 증가하였다. 하지만 low-dose가 적용된 phase에서는 큰 차이가 없었고, standard algorithm, ASIR가 작용하여 영상의 질에는 크게 작용하지 않았다. 하지만 흡수선량 측정에 있어, 주요장기만을 측정하였기에, 전체 선량은 훨씬 초과 할 것이며, 이에 있어 다른 검사조건을 조절 및 적용하면 선량의 최적화 및 환자의 선량 감소에 더욱 유용할 수 있을 것으로 사료된다. Purpose : The Urography CT has multiphase and scan is long time than others. This former and current low dose adaptive protocol were compared with radiation dose of patient to sensitive organ and noise of image. And than, tried to evaluate the clinical usefulness. Materials and Methods : The Target is total 20 patients performed follow-up Urography CT scan, scanner was performed with a 64-slice MDCT VCT Light Speed Xte (GE Healthcare, USA), Rando phantom(Model ART-200-5 Fluke Biomedical) and Glass Dosimetry System (Dose Ace FGD-1000, GD-352M, Asahi Techno Glass Corporation Shizuoka, Japan). The noise was analyzed in SD by using image J software (version 1.46r, National Institutes of Health, USA). The former protocol and low dose pointed protocol, measured CTDIvol and DLP value. Also the glass dosimeter was inserted in phantom sensitive organ, exposure dose was calculated. Results : When patient statistics were Compared with the before-after study, radiation dose was reduced to average 41% in CTDIvol and 49% in DLP value. Using the phantom, radiation dose was reduced to average 12% in CTDIvol and 24% in DLP value. The absorbed dose of phantom sensitive organ was decreased to average 41% in RT(right kidney) and 42% in LT(left kidney). The ureter and bladder was a little increase to 0.5% and 4%, but there is not much difference. In other comparable noise value was great increase 33% in unenhanced phase, however applying the low dose the enhanced abdomen pelvis and excretory phase was not that different. Conclusion : The patient radiation dose was great variance. If the mAs decreased, noise increased. But it was not much slight contrast in the low dose phase adaptation, owing to standard algorithm, practiced ASIR. Then, direct absorbed dose measured only sensitive organ, all body absorbed dose was predicted to exceed data. Consequentially, If applied the other conditions, can provide reducing absorbed dose to patients and balance radiation dose.

Clinical Comparison of Low-dose and High-dose Steroid in Pediatric Cardiac Surgery with Cardiopulmonary Bypass

Choi Seok-Cheol,Kim Song-Myung,Kim Yang-Weon 대한의생명과학회 2006 Biomedical Science Letters Vol.12 No.3

Cardiopulmonary bypass (CPB) for cardiac surgery triggers the production and release of numerous chemotactic substances and cytokines, ensuing systemic inflammatory response that leads to postoperative major organ dysfunction. Traditionally, corticosteroids (steroid) have been administered to patients undergoing cardiac surgery to ward off these detrimental physiologic alterations. However, the majority of the studies have been performed on adult patients with high-dose steroid. We carried out a randomized, prospective, double-blind study to compare the efficacy of low-dose steroid with that of high-dose steroid and to determine the adequate dose of pretreated-steroid for prophylactic effects in pediatric cardiac surgery. Thirty pediatric patients scheduled for elective cardiac surgery were randomly assigned to two groups; fifteen patients received low-dose methylprednisolone (10mg/kg intravenously, n=15, low-dose group) and the others received high-dose methylprednisolone (30mg/kg intravenously, n=15, high-dose group) 1 hour prior to CPB. Arterial blood samples were taken before CPB (Pre-CPB), 10 minutes after start of CPB (CPB-10), and immediately after CPB-end (CPB-OFF) for measuring total leukocyte counts (T-WBC) and diff-counts, platelet counts, interleukin-6 (IL-6), myeloperoxidase (MPO), total antioxidant (TAO), neuron-specific enolase (NSE), troponin I (TNI), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and blood urea nitrogen (BUN) levels. Other parameters such as volumes of urine output, pulmonary index $(PI,\;PaO_2/FiO_2)$, mechanical ventilating period, intensive care unit (ICU)-staying period, postoperative complications (fever, wound problem), postoperative 24 hrs and total volumes in blood loss, and hospitalized days were also assessed. All parameters were compared between two groups. There were no significant differences in T-WBC counts, monocyte fraction, platelet counts, TA levels, NSE levels, creatinine levels, BUN levels, the volumes of total urine output, PI, the incidences of fever and wound problem, postoperative 24hrs- and total-blood loss volumes and ICU-staying period between two groups (P>0.05). At CPB-OFF, neutrophil fraction, MPO level, TNI level, and AST level were higher in the high-dose group than in the low-dose group (P<0.05). IL-6 level at CPB-10 was higher in the high dose-group than in the low-dose group (P<0.05). Furthermore, mechanical ventilating periods and hospitalized days of the high-dose group were significantly longer than those of low-dose group (P<0.05). The high-dose group had significantly low lymphocyte fi-action at CPB-OFF compared with the low-dose group (P<0.001). These findings suggest that pretreatment of high-dose steroid is not superior to that of low-dose steroid regrading its potential benefits in pediatric cardiac surgery. Therefore, the conventional strategy of steroid treatment, high-dose pretreatment, should be modified in the cardiac surgery with CPB. However, further studies must be performed on the larger number of patients in as much as small number of patients in this study.

Low-Dose Three-Dimensional Rotational Angiography for Evaluating Intracranial Aneurysms: Analysis of Image Quality and Radiation Dose

Ki Hee Jong,Kim Bum-soo,Kim Jun-Ki,Choi Jai Ho,Shin Yong Sam,Choi Yangsean,Shin Na-Young,Jang Jinhee,Ahn Kook-jin 대한영상의학회 2022 Korean Journal of Radiology Vol.23 No.2

Objective: This study aimed to evaluate the image quality and dose reduction of low-dose three-dimensional (3D) rotational angiography (RA) for evaluating intracranial aneurysms. Materials and Methods: We retrospectively evaluated the clinical data and 3D RA datasets obtained from 146 prospectively registered patients (male:female, 46:100; median age, 58 years; range, 19–81 years). The subjective image quality of 79 examinations obtained from a conventional method and 67 examinations obtained from a low-dose (5-seconds and 0.10- μGy/frame) method was assessed by two neurointerventionists using a 3-point scale for four evaluation criteria. The total image quality score was then obtained as the average of the four scores. The image quality scores were compared between the two methods using a noninferiority statistical testing, with a margin of -0.2 (i.e., score of low-dose group – score of conventional group). For the evaluation of dose reduction, dose-area product (DAP) and air kerma (AK) were analyzed and compared between the two groups. Results: The mean total image quality score ± standard deviation of the 3D RA was 2.97 ± 0.17 by reader 1 and 2.95 ± 0.20 by reader 2 for conventional group and 2.92 ± 0.30 and 2.95 ± 0.22, respectively, for low-dose group. The image quality of the 3D RA in the low-dose group was not inferior to that of the conventional group according to the total image quality score as well as individual scores for the four criteria in both readers. The mean DAP and AK per rotation were 5.87 Gy-cm2 and 0.56 Gy, respectively, in the conventional group, and 1.32 Gy-cm2 (p < 0.001) and 0.17 Gy (p < 0.001), respectively, in the low-dose group. Conclusion: Low-dose 3D RA was not inferior in image quality and reduced the radiation dose by 70%–77% compared to the conventional 3D RA in evaluating intracranial aneurysms.

Chronic low-dose radiation inhibits the cells death by cytotoxic high-dose radiation increasing the level of AKT and acinus proteins via NF-κB activation

Park, Hyung Sun,Seong, Ki Moon,Kim, Ji Young,Kim, Cha Soon,Yang, Kwang Hee,Jin, Young-Woo,Nam, Seon Young Informa Healthcare 2013 International journal of radiation biology Vol.89 No.5

<P><I>Purpose</I>: This study explored the effects of low-dose and low-dose-rate irradiation in human lung fibroblast CCD-18Lu cells and examined the role of AKT (protein kinase B, PKB) in cellular responses.</P><P><I>Materials and methods</I>: We examined cell survival after chronic low-dose irradiation (0.01 Gy or 0.05 Gy) with challenging high-dose (2 or 10 Gy) irradiation. We examined the effect of AKT activation on cell survival after chronic low-dose radiation using transduced cells with retroviral vector expressing constitutively active AKT (CA-AKT).</P><P><I>Results</I>: Chronic low-dose priming irradiation increased cells viability against the challenging high-dose irradiation. Irradiation at 0.05 Gy increased cellular levels of AKT and acinus long form (L) and short form (S). The chronic low-dose radiation promoted cells proliferation in the exogenously expressed CA-AKT cells. It also increased nuclear factor-kappa B (NF-κB) activity in a biphasic induction pattern. Suppression of NF-κB activation by mutant form of inhibitor of kappa B alpha (IκBαM) antagonized the radiation-induced expression of AKT and acinus L and S.</P><P><I>Conclusions</I>: Chronic low-dose radiation increases the levels of AKT and acinus proteins via NF-κB activation, and the NF-κB/AKT pathway responding to chronic low-dose irradiation plays an important role in the radiation adaptive response.</P>

PET/CT 저선량 적용 시 CT 감쇠보정법에 따른 피폭선량 저감효과

정승우,김홍균,권재범,박성욱,김명준,신영만,김영헌,Jung, Seung Woo,Kim, Hong Kyun,Kwon, Jae Beom,Park, Sung Wook,Kim, Myeong Jun,Sin, Yeong Man,Kim, Yeong Heon 대한핵의학기술학회 2014 핵의학 기술 Vol.18 No.1

PET/CT에서 환자피폭 문제로 인해 저 선량의 중요성이 강조되고 있다. 본 연구에서는 기존에 사용되던 CT 데이터를 이용한 감쇠보정법인 CTAC와 새롭게 적용된 Q.AC를 환자실험과 팬텀 실험을 통해 저 선량으로 촬영 시 PET 영상에 미치는 영향에 대해 알아보고자 한다. 실험장비는 GE사의 PET/CT Discovery 710 (GE Healthcare, USA)를 사용하였으며 팬텀실험으로 감쇠보정의 정량적 평가를 위한 NEMA IEC body phantom과 균일성 평가를 위한 Uniform NU2-94 phantom을 사용하였다. 각각의 팬텀 내부에 동위원소 18-F FDG를 70.78 MBq, 22.2 MBq 주입하고 CT조건은 저 선량조건으로 80 kVp, 10 mA로부터 일반선량 조건으로 140 kVp, 120 mA 조건까지 스캔 후 CTAC와 Q.AC 두 감쇠보정법을 적용하여 재구성하였다. PET 영상에서 일반선량 조건을 기준값으로 정하고 horizomtal profile과 vertical profile을 통해 정량평가를 시행하고 기준값과의 상대적 오차를 평가하였다. 또한 환자실험으로 정상체중 환자와 과체중 환자를 구분하여 저 선량과 일반선량으로 비교 촬영한 뒤 CTAC와 Q.AC로 재구성된 PET영상에서 주요장기별 SUV에 대한 상대적 오차와 신호 대 잡음비를 비교분석하였다. 팬텀실험 결과 저선량 조건에서 CTAC와 Q.AC로 각각 재구성한 PET 영상의 profile과 상대적 오차에서 CTAC보다 Q.AC가 기준값과의 오차가 적은 그래프를 얻었다. 환자실험의 경우 일반선량 조건에서는 정상체중 환자와 과체중 환자 모두 감쇠보정법에 따른 상대적 오차값의 변화가 적었으나 저 선량 조건에서는 정상체중 환자보다 과체중 환자에서 감쇠보정법의 변경에 의한 상대적 오차의 감소폭이 커짐으로 기준값과 차이가 감소하였다. 기존의 감쇠보정법인 CTAC는 80 kVp, 10 mA의 저선량 CT를 사용하는데 있어 PET 영상의 선속경화현상이 발생한다. 이로 인해 CTAC를 이용하여 재구성된 PET 데이터는 정량화하는데 문제가 될 수 있음을 확인했다. 반면에 새로운 알고리즘이 적용된 Q.AC는 과체중 환자의 경우 80 kVp, 10 mA 정도까지는 140 kVp, 120 mA 조건으로 촬영하여 재구성한 PET 데이터 결과와 차이가 적음을 확인할 수 있었다. Q.AC를 이용한 경우 기존보다 저 선량의 CT를 이용해 PET의 재구성에 이용할 수 있으므로 환자의 피폭을 줄이는 데 큰 역할을 할 것으로 기대한다. Purpose: Low dose of PET/CT is important because of Patient's X-ray exposure. The aim of this study was to evaluate the effectiveness of low-dose PET/ CT image through the CTAC and QAC of patient study and phantom study. Materials and Methods: We used the discovery 710 PET/CT (GE). We used the NEMA IEC body phantom for evaluating the PET data corrected by ultra-low dose CT attenuation correction method and NU2-94 phantom for uniformity. After injection of 70.78 MBq and 22.2 MBq of 18 F-FDG were done to each of phantom, PET/CT scans were obtained. PET data were reconstructed by using of CTAC of which dose was for the diagnosis CT and Q. AC of which was only for attenuation correction. Quantitative analysis was performed by use of horizontal profile and vertical profile. Reference data which were corrected by CTAC were compared to PET data which was corrected by the ultra-low dose. The relative error was assessed. Patients with over weighted and normal weight also underwent a PET/CT scans according to low dose protocol and standard dose protocol. Relative error and signal to noise ratio of SUV were analyzed. Results: In the results of phantom test, phantom PET data were corrected by CTAC and Q.AC and they were compared each other. The relative error of Q.AC profile was been calculated, and it was shown in graph. In patient studies, PET data for overweight patient and normal weight patient were reconstructed by CTAC and Q.AC under routine dose and ultra-low dose. When routine dose was used, the relative error was small. When high dose was used, the result of overweight patient was effectively corrected by Q.AC. Conclusion: In phantom study, CTAC method with 80 kVp and 10 mA was resulted in bead hardening artifact. PET data corrected by ultra- low dose CTAC was not quantified, but those by the same dose were quantified properly. In patients' cases, PET data of over weighted patient could be quantified by Q.AC method. Its relative difference was not significant. Q.AC method was proper attenuation correction method when ultra-low dose was used. As a result, it is expected that Q.AC is a good method in order to reduce patient's exposure dose.

관상동맥 석회화 평가에서 저선량 흉부 CT와 관상동맥 석회화검사의 일치도

김연민 한국방사선학회 2023 한국방사선학회 논문지 Vol.17 No.7

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. Low-dose chest CT, which is used as a lung screening test, also includes information on coronary artery calcification within the scan range. The purpose of this study was to investigate the usefulness of determining coronary artery calcification using Low-dose chest CT. Those who underwent low-dose chest CT and coronary artery calcification score CT on the same day were eligible. Coronary artery calcium score CT results were divided into 4 groups (Low: 1<CACS<10, Mild: 10<CACS<100, Moderate: 100<CACS<400, High: 400<CACS) by referring to the Coronary artery calcium score categories and risks. After selecting 30 people each group, five radiotechnologists with more than 15 years of experience in coronary artery calcium measurement retrospectively analyzed the presence or absence of coronary artery calcification in low-dose chest CT images. The results of the five observers' uniform interpretation of the low-dose chest CT image were consistent with the coronary artery calcium score CT results in Low group: 56%, Mild group: 96.6%, Moderate group: 100%, and High group: 100%. appeared. In the Low group, all 5 observers observed calcification in 17 out of 30 cases, and in 7 cases all 5 observers decided that calcification could not be identified. Coronary artery calcification could be observed in 100% of asymptomatic adults with a calcium score of 15 or higher in low-dose chest CT scans. The minimum calcium score that can be identified is 1, and it was found that even very small calcifications can be identified when the subject's body size is small or the scan is performed at a time when heart movement is minimal.

Low-dose Radiation Induces Antitumor Effects and Erythrocyte System Hormesis

Yu, Hong-Sheng,Liu, Zi-Min,Yu, Xiao-Yun,Song, Ai-Qin,Liu, Ning,Wang, Hao Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.7

Objective: Low dose radiation may stimulate the growth and development of animals, increase life span, enhance fertility, and downgrade the incidence of tumor occurrence.The aim of this study was to investigate the antitumor effect and hormesis in an erythrocyte system induced by low-dose radiation. Methods: Kunming strain male mice were subcutaneously implanted with S180 sarcoma cells in the right inguen as an experimental in situ animal model. Six hours before implantation, the mice were given 75mGy whole body X-ray radiation. Tumor growth was observed 5 days later, and the tumor volume was calculated every other day. Fifteen days later, all mice were killed to measure the tumor weight, and to observe necrotic areas and tumor-infiltration-lymphoreticular cells (TILs). At the same time, erythrocyte immune function and the level of 2,3-diphosphoglyceric acid (2,3-DPG) were determined. Immunohistochemical staining was used to detect the expression of EPO and VEGFR of tumor tissues. Results: The mice pre-exposed to low dose radiation had a lower tumor formation rate than those without low dose radiation (P < 0.05). The tumor growth slowed down significantly in mice pre-exposed to low dose radiation; the average tumor weight in mice pre-exposed to low dose radiation was lighter too (P < 0.05). The tumor necrosis areas were larger and TILs were more in the radiation group than those of the group without radiation. The erythrocyte immune function, the level of 2,3-DPG in the low dose radiation group were higher than those of the group without radiation (P < 0.05). After irradiation the expression of EPO of tumor tissues in LDR group decreased with time. LDR-24h, LDR-48h and LDR-72h groups were all statistically significantly different from sham-irradiation group. The expression of VEGFR also decreased, and LDR-24h group was the lowest (P < 0.05). Conclusion: Low dose radiation could markedly increase the anti-tumor ability of the organism and improve the erythrocyte immune function and the ability of carrying $O_2$. Low-dose total body irradiation, within a certain period of time, can decrease the expression of hypoxia factor EPO and VEGFR, which may improve the situation of tumor hypoxia and radiosensitivity of tumor itself.

Significantly Low Effective Dose from ¹⁸FDG PET/CT Scans Using Dose Reducing Strategies: "Lesser is Better"

uz Zaman, Maseeh,Fatima, Nosheen,Zaman, Areeba,Zaman, Unaiza,Tahseen, Rabia Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.7

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.

Stellar Detector를 적용한 저선량 흉부 CT의 최적 프로토콜에 관한 연구

박혜수(Hye Su Park),이기백(Ki Baek Lee),구현정(Hyun Jung Ko) 대한전산화단층기술학회 2015 대한CT영상기술학회지 Vol.17 No.2

목적 : 조기 발견이 중요한 폐암의 경우 일반 흉부 X선 검사의 한계로 인해 Low dose chest CT가 권장되고 있다. 고화질 영상 획득으로 신뢰성이 높으나 여전히 다른 영상 촬영법에 비해 환자 피폭에 대한 risk를 가지고 있다. 이에 적은 선량으로 고화질의 영상을 획득하기 위해 최근에는 검출기 성능을 향상시키고자 개발된 Stellar detector가 있다. 본 논문은 Stellar detector를 기존 검출기와 비교하여 성능을 평가하고 저선량 흉부 CT의 최적 프로토콜을 찾고자 한다. 대상 및 방법 : Stellar detector 기술을 반영한 128채널의 Somatom Definition Edge (Siemens, Erlangen, Germany)와 이전 모델인 128채널의 Somatom Definition AS+ (Siemens, Erlangen, Ge rmany)를 비교평가 하였다. 검사 조건으로는 관전압은 100kVp, 120kVp, 140kVp를 사용하고 관전류는 10mAs에서 50mA까지 5mAs씩 증가시켜 적용하였다. 그 외에 인자들은 Low-dose Chest CT 프로토콜과 동일하게 진행하였다. 정량적 평가를 위해 영상의 Noise와 CNR을 분석하였다. 정성적 평가는 두 가지 기준을 채택하였다. 인체 흉부 팬텀 (Lung Chest Phantom; FLUKE BIOMECAL, RS-330, CLEVELAND)을 이용한 저선량 흉부 CT 판독 소견과 AAPM performance phantom(model 76-4104130, US)의 High spatial contrast resolution 블록에 발견되는 양자잡음 (Quantom noise, 양자반점) 발생 정도를 평가하였다. 결과 : 정량적 분석에서 Edge가 AS+에 비해 모든 조건 하의 CNR 값이 높았다. 통계적으로 p〈0.05가 성립되어 데이터의 차이를 확인하였다. 정성적 평가에서는 Edge의 경우 100kVp/45mAs, 120kVp/20mAs, 140kVp/20mAs가, AS+의 경우 100kVp/50mAs, 120kVp/25mAs, 140kVp/20mAs가 선량측면까지 고려하여 높은 점수를 받았다. 두 번째 정성적 평가에서 Edge는 100kVp/20mAs, 120kVp/15mAs까지 다수의 양자잡음이 발생하였고 AS+는 100kVp/25mAs, 120kVp/20mAs, 140kVp/10mAs에서 발생하였다. 결론 : 종합적인 분석에 따르면 최적의 Low-dose Chest CT 프로토콜은 Edge장비에서는 120/20mAs, AS는 120/25mAs가 적합하다고 할 수 있다. 기존 검출기에 비해 약 12%의 CNR 증가율과 약 51%의 DLP 감소율을 보여주었다. 이를 통해 Stellar detector가 적은 선량에서도 상대적으로 고화질의 영상을 구현하고 우수한 성능을 가짐을 확인 할 수 있었다. Purpose : The state-of-the-art “Stellar detector” has been developed to improve detector performance for acquisition of high quality images with reduced radiation dose. The purpose of this study was to compare the performance between Stellar and the conventional detectors, and to find out the optimal low-dose chest CT protocol. Materials and Methods : 128-MDCT with newly built-in stellar detector, SOMATOM Definition Edge (Siemens, Erlangen, Germany) and 128-MDCT with conventional detector, SOMATOM Definition AS+ (Siemens, Erlangen, Germany) were used in this study. Scan settings were as follows: tube voltage of 100, 120, and 140 kVp, and tube current from 1 Oto 50 mAs in 5-mAs increment. Other parameters were the same as the standard low-dose chest CT protocol. Noise, CNR were analyzed for quantitative evaluation. For qualitative evaluation, two methods were used; radiologist’s interpretation of low-dose chest CT images of Lung Chest Phantom (FLUKE BIOMECAL, RS-330, CLEVELAND), and quantom noise appeared on the high spatial contrast resolution module of AAPM phantom. Result : In quantitative evaluation, CNR value of SOMATOM Definition Edge was higher than SOMATOM Definition AS+ under all scan settings. P-value was below 0.05 in Paired t-test. So It showed a stastically significant difference. First qualitative evaluation was assessed the image using the following 5-point score. The results of high quality image are as follows: 100kVp/45mAs, 120kVp/20mAs, 140kVp/20mA in SOMATOM Definition Edge and 100kVp/50mAs, 120kVp/25mAs, 140kVp/20mAs in SOMATOM Definition AS+. The results of second evaluation are as follows: we can find many quantum noise at 100kVp/20mAs, 120kVp/15mAs in SOMATOM Definition Edge and 100kVp/25mAs, 120kVp/20mAs, 140kVp/10mAs in SOMATOM Definition AS+. Conclusion : The optimal protocol for low-dose chest CT was found to be 120 kV/20 mAs and 120 kV/25 mAs for SOMATOM Definition Edge and AS+ scanners, respectively. It can provide 12% increase of CNR and 51% decrease of radiation dose. Stellar detector can provide high quality images with relatively lower radiation dose compared to the conventional detectors.