북부 Scan시 Scan Projection Radiography의 Exposure condition의 변화에 따른 선량의 영향

정용환(Yong Hwan Chung),남태현(Tae Hyun Nam),구본승(Bone Seung Goo),대창민(Chang Min Dae),민관홍(Kwan Hong Min) 대한CT영상기술학회 2012 대한CT영상기술학회지 Vol.14 No.2

목적 이전에는 Scan 범위와 계획을 세우는 것이 목적이었던 Scan Projection Radiography(이하 SPR)가 Auto Exposure Control(이하 AEC)의 발달로 환자의 크기와 감약정보 등을 얻어 관전류(mA)를 결정하는 중요한 역할을 하게 되었다. 하지만 아직 환자에 따라 SPR획득 시 관전압(kVp)과 관전류(mA)의 설정을 변경할 경우 실제 scan에서 선량에 어떤 영향이 생길지 여부는 객관적으로 증명되지 않았다. 따라서 본 연구가 SPR 획득 시 적정한 관전압과 관전류를 설정하여 선량의 최적화(optimization)를 달성하는 Guide line이 되길 바란다. 대상 및 방법 사용된 CT는 4사장비로 Brilliance iCT(Philips healthcare, 이하 P사), Light Speed VCT(General Electric Medical System, 이하 G사), Somatom Definition Flash(Siemens Healthcare, 이하 S사), Aquilion64(Toshiba Medical System, Auklet Japan, 이하 T사)를 사용하였다. 첫번째 실험은 Phantom을 대상으로 복부 scan시 병원에서 사용하는 Protocol 그대로 적용하였고 SPR촬영은 length를 500mm로 고정하고 관전압을 80~120kVp, 관전류를 10~50mA로 변경하면서 적용하였고 장비에서 제공하는 CTDIvol와 DLP의 평균값을 계산하여 각 노출조건 간의 증감률을 알아보았다, 두번째 실험은 복부 scan을 위해 본원에 내원한 환자 602명을 대상으로 P사의 장비로 각 노출조건을 신체질량지수(Body Mass Index, 이하 BMI)로 분류하고 선량에 영향이 있는지 알아보았다. 세번째 실험은 두번째 실험 대상자 중 Planned mAs가 250 이상인 환자 123명을 대상으로 Auto current selection(Patient size AEC, 이하 ACS)의 적용을 중지하고 longitudinal AEC만 적용한 채로 선량의 증감률을 알아보았다. 결과 첫번째, Phantom을 대상으로 복부 scan후 선량의 증감률이 P사와 G사의 경우에는 SPR의 노출조건이 120kVp, 30mA일 때 CTDI가 최대 7.04%, DLP는 6.28%까지 감소했고 S사와 T사의 경우에는 120kVp, 50mA일 때 CTDI가 최대8.24%. DLP는 1.38% 감소했다. 두번째, 실제 환자를 복부 scan시 BMI에 따라 분류한 결과 SPR의 노출조건이 120 kVp, 30mA일 때 CTDI가 저체중군 15.36%, 정상군 5.09%, 과체중군 7.25%, 비만군 10.48%까지 감소했다. 세번째, longitudinal AEC만을 적용한 환자를 분류한 결과 역시 SPR 노출조건에 따라 CTDI 최대 2.85%까지 차이가 나는 것을 알 수 있었다. 결론 본 실험을 통해서 환자의 체형이나 나이에 따라 SPR의 노출 조건을 검사자가 임의로 조절해서 시행할 경우 오히려 전체적인 선량을 증가시킬 수 있는 오류를 범하게 될 수도 있다. AEC의 발달로 환자에게 적용되는 선량이 감소하는 것은 사실이지만 그에 따라 AEC에 영향을 주는 SPR의 역할이 커진 만큼 환자에 따라 노출 조건의 가이드라인을 확립하여 환자에게 최소의 선량으로 최적의 영상을 만들 수 있는 연구가 필요하다고 사료된다. I. Purpose Due to the development of AEC, Scan Projection Radiography which used to plan scan area only, now performs its important role of control tube current. However, there is no studies and guide line of effective dose depending on SPR scan parameters such as tube voltage and current so far. Therefore, on this study we set a valid tube voltage and tube current when getting SPR and analyze the result We want to set a guide line of suitable SPR parameter in order to achieve the dose optimization. II. Meterial and Methods Used CT scanners are 4 machines, Brilliance iCT(Philips healthcare), Light Speed VCT 64 MDCT(General Electric Medical System), Somatom Definition Flash(Siemens Healthcare), and Aquilion64 (Toshiba Medical System, Auklet Japan). In first study, the routine abdomen CT parameters which is using to patient are applied to this study. SPR scan length was fixed to 500mm. Tube voltage and current are changed from 80 to 120 kVp and 10 to 50 mA. We investigate changing rate between each exposure conditions to calculate the average value. CTDIvol and DLP which come from the machine are used. Second study, I assorted each exposure conditions with Philips machine into Body Mass Index, and studied the effect on liner value targeting 602 patients. Third study, we stop applying Auto current selection(Patient size AEC) and using longitudinal AEC to 123 patients who have over 250 planned mAs. Then we analyze changing rate. III. Result In first study, using P and G with 120 kVp and 30 mA exposure condition, dose was reduced 7.04% in CTDI and 6.28% in DLP. In the case of S and T with 120kVp, 50mA, was 8.24% in CTDI, 1.38% in DLP. In second study, depending on BMI, it was dropped that CTDI’s underweight to 15.35%, normal to 5.09%, overweight to 7.25%, obesity to 10.48% in the case that exposure conditions were 120kVp, and 30mA. In third study, maximum difference was 2.85% in CTDI when only longitudinal AEC is adapted. IV. Conclusions In this study, Depending on the patient’s body type or age of the SPR adjust the exposure conditions controlled by a random Rather, that can increase the overall dose may be commit errors. AEC is applied to the patient to the development of dose reduction is true that the AEC accordingly, affecting as many tients with enlarged role of the SPR, depending on exposure conditions, by establishing guidelines for patients with a dose of at least create the best image research that will be need.

Auto Exposure Control을 사용하는 흉ㆍ복부 검사 시 Scan Projection Radiography의 획득방법에 따른 복부 CT의 DoseLength-Product 비교

김진희(Jin Hee Kim),이종민(Jong Min Lee),정용환(Young Hwan Chung),대창민(Chang Min Dae),민관홍(Kwan Hong Min) 대한CT영상기술학회 2015 대한CT영상기술학회지 Vol.17 No.1

목적 : Multi-scan 하는 흉부와 복부 CT 검사 시 SPR을 흉ㆍ복부 한 번에 획득한 경우와 각각 나누어서 획득한 경우 복부 CT의 DLP값을 분석하여 환자 선량을 비교하고자 했다. 대상 및 방법 : Phantom 연구에서 사용된 phantom은 whole body phantom(KUPBU -50 Kyoto kakaku Co,LTd)을 사용하였고 CT 장비는 Brilliance iCT(Philips healthcare, Cleveland, OH, USA, 이하 P사), Light Speed VCT(General Electric Medical System, Milwaukee, USA, 이하 G사), Somatom Definition Flash(Siemens Healthcare, Forchheim Germany, 이하 S사), Aquilion 64 (Toshiba medical system, Auklet Japan, 이하 T사)를 사용하였다. 각 장비 마다 흉ㆍ복부 한 번에 획득한 SPR(이하 W-SPR)과 흉부와 복부 각각 획득한 SPR(이하 S-SPR)을 이용하여 각 병원에서 사용하는 복부 protocol로 복부 scan을 하였고 장비에서 제공하는 DLP를 비교하였다. 임상연구는 2014년 5월부터 6월까지 내원한 환자 100명을 Group1로 분류하여 W-SPR로 복부 scan을 하였다. 2014년 7월부터 8월까지 내원한 환자 100명은 S-SPR로 복부 scan을 하였고 이를 Group 2라고 분류하였다. 각 Gruop간의 DLP의 차이는 Box-Whisker plot Chart를 이용하여 중앙값을 구했으며 DLP 증감률을 알아보았다. 결과 : Phantom을 이용한 실험에서 P사의 W-SPR로 검사한 복부 CT의 DLP가 367.1 mGyㆍcm, S-SPR의 복부 CT의 DLP는 398.1 mGyㆍcm로 측정되었다. 반면 S사, G사, T사는 흉 복부 포함하여 촬영한 SPR과 흉ㆍ복부 각각 촬영한 SPR에서의 복부 DLP는 거의 차이가 없는 것으로 나타났다. 임상 연구에서는 Group 1의 DLP의 중앙값이 442.7 mGyㆍcm, Group 2의 DLP의 중앙값이 494.2 mGyㆍcm 로 나타났다. 각 Group 간 DLP 증감률은 10.42%정도의 수치를 보였다. 결론 : 본 연구를 통해 각 제조사별로 ACE의 특징이 다르다는 것을 확인 할 수 있었으며, 특히 P사는 SPR의 Scan length에 영향을 받는 것으로 확인되므로, P사를 사용하는 검사자는 흉ㆍ복부 검사 시 SPR을 한 번에 획득하여 검사 하는 것이 환자 선량을 줄일 수 있다. Purpose : This study compare dose of patient by analyzing the DLP value of abdominal CT when the case of acquired SPR separately each of the chest and abdomen and when acquired SPR in chest-abdomen once in Multi-scan of Chest and Abdominal CT Scan. Materials and method : In phantom study, Whole body phantom (KUPBU -50 Kyoto kakaku Co,LTd) was used and CT scanners Brilliance iCT(Philips healthcare, Cleveland, OH, USA), Light Speed VCT(General Electric Medical System, Milwaukee, USA), Somatom Definition Flash(Siemens Healthcare, Forchheim Germany) and Aquilion 64 (Toshiba medical system, Auklet Japan) were used. Each of manufacture, we compared the DLP and compared the value of SPR when scanning chest and abdomen once(W-SPR) with scanning Chest and Abdomen separately (S-SPR). In Clinical study, 100 patients who visited the hospital May-June 2014 were classified into Group 1. And Scanned Abdomen using with W-SPR. 100 patients who visited July-August 2014 were classified as Group 2. And Scanned using the S-SPR. Using a Box-and- Whisker plot Chart, obtained the median value of differences between Gruop 1, 2 and DLP changes. Result : In phantom study, Philips result is 367.1 mGyㆍcm in DLP using a W-SPR and 398.1 mGyㆍcm in DLP of abdomen CT using a S-SPR. Otherwise, Siemens, GE, and Toshiba results are no difference between the DLP of abdomen CT using a W-SPR and S-SPR. In clinical study, the median DLP value percentage change was 10.42% decreased in Group 1. Median DLP values were 442.7mGyㆍcm in group 1 and 494.2mGyㆍcm in Group 2. Conclusion : According to the results, we once more confirm, each vendor’s AEC system applies different mechanism and characteristic. Especially, P vendor’s AEC system is influenced by SPR length, sensitively. Therefore, we recommend scanning chest and abdomen at once regarding the dose reduction for P machine users.

A Comparison between Dual-Exposure Dual-Energy Radiography and Standard Chest Radiography for the Diagnosis of Small Pulmonary Nodules

황혜선,정명진,김성목,이지원,한헌 대한영상의학회 2008 대한영상의학회지 Vol.59 No.6

Purpose: To evaluate the utility of dual-exposure dual-energy radiography against the standard chest radiography in the discrimination of lung nodules and the presence of nodule calcification. Materials and Methods: Twenty-nine patients with a total of 43 peripheral lung nodules were examined by dual-exposure dual-energy radiography (DER) and confirmed by a chest CT were included in the study. Of the identified peripheral lung nodules, 24 showed calcification and 19 did not. Further, 28 lesion-free regions from the same patient population were selected as negative controls. Two radiologists evaluated 71 marked locations using both standard chest radiographs (SR) and DER to determine whether the marked locations represented a true nodule, and whether nodule calcification was present. A continuous rating scale of 0-10 was used to represent each observer’'s confidence level. We calculated the areas under ROC curves (AUC) for SR alone and for DER, and performed a statistical analysis to compare the results. Results: The ability to discriminate nodules was higher for DER than for SR. However, the was not statistically significant (p = 0.202). Inter-observer agreement was moderate regardless of if DER was used. The predictability of nodule calcification was significantly higher for DER compared to SR (p < .001). Moreover, inter-observer agreement was slight with SR alone but moderate with DER. Conclusion: DER, in conjunction with SR, has no additional benefit in small lung nodule discrimination but does provide a significant benefit in the characterization of nodule calcification.

Comparison of Radiation Dose and Image Quality between the 2nd Generation and 3rd Generation Dual- Source Single-Energy and Dual-Source Dual-Energy CT of the Abdomen

Chang Gun Kim,김시형,Seung Hyun Cho,염헌규,Won Hwa Kim,김혜정 대한영상의학회 2022 대한영상의학회지 Vol.83 No.6

Purpose We compared the radiation dose and image quality between the 2nd generation and the 3rd generation dual-source single-energy (DSSE) and dual-source dual-energy (DSDE) CT of the abdomen. Materials and Methods We included patients undergoing follow-up abdominal CT after partial or radical nephrectomy in the first 10 months of 2019 (2nd generation DS CT) and the first 10 months of 2020 (3rd generation DS CT). We divided the 320 patients into 4 groups (A, 2nd generation DSSE CT; B, 2nd generation DSDE CT; C, 3rd generation DSSE CT; and D, 3rd generation DSDE CT) (n = 80 each) matched by sex and body mass index. Radiation dose and image quality (objective and subjective qualities) were compared between the groups. Results The mean size-specific dose estimation of 3rd generation DSDE CT group was significantly lower than that of the 2nd generation DSSE CT (42.5%, p = 0.013) and 2nd generation DSDE CT (46.9%, p = 0.015) groups. Interobserver agreement was excellent for the overall image quality (intraclass correlation coefficient [ICC]: 0.8867) and image artifacts (ICC: 0.9423). Conclusion Our results showed a considerable reduction in the radiation dose while maintaining high image quality with 3rd generation DSDE CT as compared to the 2nd generation DSDE CT and 2nd generation DSSE CT.

간의 단일선원 Twin Beam과 이중선원 이중에너지 전산화단층촬영의 비조영증강 영상과 가상 비조영증강 영상의 비교 연구

Jeong Sub Lee,Guk Myung Choi,Bong Soo Kim,Su Yeon Ko,Kyung Ryeol Lee,Jeong Jae Kim,Doo Ri Kim 대한영상의학회 2023 대한영상의학회지 Vol.84 No.1

Purpose To assess the magnitude of differences between attenuation values of the true non-contrast image (TNC) and virtual non-contrast image (VNC) derived from twin-beam dual-energy CT (tbDECT) and dual-source DECT (dsDECT). Materials and Methods This retrospective study included 62 patients who underwent liver dynamic DECT with tbDECT (n = 32) or dsDECT (n = 30). Arterial VNC (AVNC), portal VNC (PVNC), and delayed VNC (DVNC) were reconstructed using multiphasic DECT. Attenuation values of multiple intra-abdominal organs (n = 11) on TNCs were subsequently compared to those on multiphasic VNCs. Further, we investigated the percentage of cases with an absolute difference between TNC and VNC of ≤ 10 Hounsfield units (HU). Results For the mean attenuation values of TNC and VNC, 33 items for each DECT were compared according to the multiphasic VNCs and organs. More than half of the comparison items for each DECT showed significant differences (tbDECT 17/33; dsDECT 19/33; Bonferroni correction p < 0.0167). The percentage of cases with an absolute difference ≤ 10 HU was 56.7%, 69.2%, and 78.6% in AVNC, PVNC, and DVNC in tbDECT, respectively, and 70.5%, 78%, and 78% in dsDECT, respectively. Conclusion VNCs derived from the two DECTs were insufficient to replace TNCs because of the considerable difference in attenuation values.

급성 충수염이 의심되는 환자에서 이중 에너지 전산화단층촬영을 통하여 얻은 가상 비조영증강 영상의 유용성

허태영,이영환,윤권하 대한영상의학회 2016 대한영상의학회지 Vol.75 No.4

Purpose: To determine whether virtual non-enhanced (VNE) images derived from dual-energy computed tomography (DECT) can replace true non-enhanced (TNE) images in patients with suspected acute appendicitis. Materials and Methods: A total of 195 patients were scanned using DECT. Two radiologists reviewed the VNE set (VNE and portal-phase images) and the TNE set (TNE and portal-phase images), 4 weeks later. Sensitivities and specificities for the diagnosis of acute appendicitis and radiation doses for each set were calculated. Image quality and artifacts in the VNE set were rated on a four point scale (1 = poor–4 = excellent). Size and attenuation of intraperitoneal calcifications were compared in each image. Results: A total of 114 patients were diagnosed with acute appendicitis by operation. In the VNE set, sensitivity and specificity were 99.1% and 89.9% for reader 1, and 96.6% and 94.8% for reader 2, respectively. In the TNE set, the corresponding values were 96.6% and 94.9% for reader 1, and 94.8% and 92.4% for reader 2, respectively. Among the 87 calcifications detected in the TNE set, 74 calcifications were noted in the VNE set. Mean image quality and artifact were 3.61 and 3.83, respectively. Radiation dose reduction was 48% after excluding the TNE set. Conclusion: Image quality and diagnostic performance of the VNE set were not inferior to those of the TNE set. Replacing TNE images by VNE images can reduce the radiation dose in evaluation of patients with acute appendicitis.

Virtual Monochromatic Image Quality from Dual-Layer Dual-Energy Computed Tomography for Detecting Brain Tumors

Tanoue Shota,Nakaura Takeshi,Nagayama Yasunori,Uetani Hiroyuki,Ikeda Osamu,Yamashita Yasuyuki 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.6

Objective: To evaluate the usefulness of virtual monochromatic images (VMIs) obtained using dual-layer dual-energy CT (DL-DECT) for evaluating brain tumors. Materials and Methods: This retrospective study included 32 patients with brain tumors who had undergone non-contrast head CT using DL-DECT. Among them, 15 had glioblastoma (GBM), 7 had malignant lymphoma, 5 had high-grade glioma other than GBM, 3 had low-grade glioma, and 2 had metastatic tumors. Conventional polychromatic images and VMIs (40–200 keV at 10 keV intervals) were generated. We compared CT attenuation, image noise, contrast, and contrast-to-noise ratio (CNR) between tumor and white matter (WM) or grey matter (GM) between VMIs showing the highest CNR (optimized VMI) and conventional CT images using the paired t test. Two radiologists subjectively assessed the contrast, margin, noise, artifact, and diagnostic confidence of optimized VMIs and conventional images on a 4-point scale. Results: The image noise of VMIs at all energy levels tested was significantly lower than that of conventional CT images (p < 0.05). The 40-keV VMIs yielded the best CNR. Furthermore, both contrast and CNR between the tumor and WM were significantly higher in the 40 keV images than in the conventional CT images (p < 0.001); however, the contrast and CNR between tumor and GM were not significantly different (p = 0.47 and p = 0.31, respectively). The subjective scores assigned to contrast, margin, and diagnostic confidence were significantly higher for 40 keV images than for conventional CT images (p < 0.01). Conclusion: In head CT for patients with brain tumors, compared with conventional CT images, 40 keV VMIs from DL-DECT yielded superior tumor contrast and diagnostic confidence, especially for brain tumors located in the WM.

Comparison of Metal Artifact Reduction Algorithms in Patients with Hip Prostheses: Virtual Monoenergetic Images vs. Orthopedic Metal Artifact Reduction

유혜진,Sung Hwan Hong,Ja Young Choi,Hee Dong Chae 대한영상의학회 2022 대한영상의학회지 Vol.83 No.6

Purpose To assess the usefulness of various metal artifact reduction (MAR) methods in patients with hip prostheses. Materials and Methods This retrospective study included 47 consecutive patients who underwent hip arthroplasty and dual-energy CT. Conventional polyenergetic image (CI), orthopedic-MAR (OMAR), and virtual monoenergetic image (VMI, 50–200 keV) were tested for MAR. Quantitative analysis was performed in seven regions around the prostheses. Qualitative assessments included evaluation of the degree of artifacts and the presence of secondary artifacts. Results The lowest amount of image noise was observed in the O-MAR, followed by the VMI. O-MAR also showed the lowest artifact index, followed by high-keV VMI in the range of 120–200 keV (soft tissue) or 200 keV (bone). O-MAR had the highest contrast-to-noise ratio (CNR) in regions with severe hypodense artifacts, while VMI had the highest CNR in other regions, including the periprosthetic bone. On assessment of the CI of pelvic soft tissues, VMI showed a higher structural similarity than O-MAR. Upon qualitative analysis, metal artifacts were significantly reduced in O-MAR, followed by that in VMI, while secondary artifacts were the most frequently found in the O-MAR (p < 0.001). Conclusion O-MAR is the best technique for severe MAR, but it can generate secondary artifacts. VMI at high keV can be advantageous for evaluating periprosthetic bone.