소아 CT검사의 선량감소 프로토콜

조한별(Han Byeol Jo),남윤철(Yoon Cheul Nam),김문찬(Moon Chan Kim) 대한CT영상기술학회 2012 대한CT영상기술학회지 Vol.14 No.1

여러 회에 걸쳐 follow-up 검사를 받는 소아환자를 위하여 기존 대비 30% 선량감소 프로토콜을 설정하고 적용하였으며 선량감소 효과 및 영상 평가를 시행하고자 하였다. 대상 및 방법 CT장비는 Light Speed VCT XTe(GE healthcare, Milwaukee, USA)를 사용하였고, 팬텀은 16em acryl head phantom을 사용하였다. Follow-up 검사의 선량감소 프로토콜을 만들기 위해 AEC가 적용되는 chest와 abdomen 검사는 noise index를 증가시키고, fixed mA를 사용하는 brain 검사는 mA를 30% 감소시켜 CTDIvol 값을 30% 감소시켰다. 새로운 프로토콜을 적용하여 follow-up 기간이 6개월 이내인 소아환자를 검사 부위별 20명씩 선정하였다. 이를 대상으로 dose report에 제공되는 CTDIvol, DLP, 유효선량을 통해 선량평가를 시행하였다. 또한 화질 평가를 위해 noise를 측정하고 CNR을 분석하였으며, 각 영상에 4단계의 점수를 부여하여 visual grade 평가를 시행하였다. 결과 선량의 평균 감소율은 chest 검사에서 CTDIvol 20%, DLP 26%, 유효선량 28%, abdomen 검사에서 CTDIvol 30%, DLP 32%, 유효선량 32%, brain 검사에서 CTDIvol 31%, DLP 33%, 유효선량 33%로 나나났다. 화질 평가에서 CNR의 평균 감소율은 chest 검사에서 15.65%, abdomen 검사에서 9.24%, brain 검사에서 33.97%였다. visual grade 평가결과 chest lung setting에서 10.07% 증가하였고, chest mediastinal setting에서 8.41% 감소하였으며 abdomen 검사와 brain 검사에서는 각각 11.82%, 4.27% 감소하였다. 그러나 영상의 진단적 가치가 인정되는 범위에 포함되었다. 결론 Follow-up 검사의 선량감소 프로토콜의 적용한 결과 선량감소 효과가 명확했으며, 화질이 약간 감소했으나 판독을 위한 진단적 가치는 유효하였다. 이 프로토콜을 통해 소아환자의 선량감소에 크게 기여하리라 생각된다. I. Purpose To set up the 30% dose reduction protocol for pediatric patients scanned follow-up CT several times and to evaluate dose reduction and image quality. II. Meterials and Methods Light Speed VCT XTe(GE healthcare, Milwaukee, USA) and 16cm acryl head phantom used far this study. To set up the dose reduction protocol, chest and abdomen protocol using AEC mode was modified by increasing noise index and brain protocol using fixed mA was modified by decreasing mA. The dose reduction protocol was applied and 20 people were selected who underwent follow-up CT within 6 months for each scan region. CTDIvol, DIP, and effective dose were compared to evaluate the dose reduction. And CNR was analyzed for evaluation of image quality by measurement of image noise and visual grade evaluation was performed. III. Results The average decreasing rate(%) of CTDIvol, DLP, and effective dose were as follows : 20/26/28 for chest CT, 30/32/32 for abdomen CT, 31/33/33 for brain CT, respectively. The average decreasing rate(%) of CNR was 15.65 for chest CT, 9.24 for abdomen CT, 33.97 for brain CT, respectively. The average visual grade was increased 10.07% for chest lung setting image, was decreased 8.41% for chest mediatinal setting image, 11.82% for abdomen image, and 4.27 for brain image, respectively. But follow-up images were also diagnostic upon visual grade analysis. IV. Conclusion Significant dose reduction can be achieved for pediatric follow-up CT by our dose reduction protocols while image quality is preserved within the diagnostic range.

Multi-detector CT장치의 저대조도분해능 평가

김지혜(Ji Hye Kim),김문찬(Moon Chan Kim),남윤철(Yoon Cheul Nam) 대한CT영상기술학회 2009 대한CT영상기술학회지 Vol.11 No.1

Purpose As the quality control is getting more important, it is required to maintain the improved image quality consistently. Especially, low contrast resolution is ability to detect low contrast lesion which shows in detail CT number difference like abdominal organs in MDCT. Therefore, the purpose of the study was comparison of CNR and visual evaluation, between the estimation of low contrast resolution of MDCT from each manufacturers and the estimation of low contrast resolution by each different phantoms by using phantoms in CT that have become commercial. Materials and methods We used LightSpeed VCT(GE medical system, USA), Aquilion 64(Toshiba medical system, Japan), Brilliance 40(Philips medical system, Netherlands) in Samsung medical center. We also used CATPHAN, ACR phantom and AAPM phantom for low contrast resolution phantom. Each of CATPHAN and ACR phantom has surrounding substances and holes those difference of attenuation coefficient are 5HU and 6HU, We measured AAPM phantom by filling holes to make 6HU difference with solution mixed saline solution and contrast media. In phantom study, We performed axial scan mode and 5mm slice thickness for 15mGy of CTDIvol that is applied to abdominal study(GE MDCT’s condition was 120kVp, 170mAs, Philips was 120kVp, 210mAs, Toshiba was 120kVp, 160mAs). For the estimation, We calculated contrast noise ratio(CNR) of materials’ CT number and CT number and noise on background by using ROI in three different phantoms. We observed scan images by using PACS system from GE medical center which was in limiting ranges window width 100-230HU and level 80-180HU, then we estimated low contrast resolution by using diameter which shows minimum dimension that could be seen visually. There were 5 CT special radiologic technologists to raise objectivity and the diameters that are distinguished by over 4 of them were choosen and reflected to result it. Results When low contrast resolution of MDCT from each manufacturer is estimated by CNR, the values of them from each manufacturer which are GE’s, Philips’s and Toshiba’s were 1.00, 0.93, 0.79 in CATPHAN phantom, 1.05, 0.97, 0.88 in ACR phantom and 0.92, 0.85, 0.81 in AAPM phantom. for visual evaluation, It was able to distinguish diameter of 3mm in GE’s and Philips’s, 4mm in Toshiba’s by CATPHAN phantom; 3mm in GE’s, 4mm in Philips’s Toshiba’s by AAPM phantom. When low contrast resolution by each different phantom is estimated by CNR, the values of them from each phantom which are CATPHAN, ACR and AAPM phantom were 1.00, 1.05, 0.92 in GE’s, 0.93, 0.97, 0.85 in Philips’s, 0.70, 0.88, 0.81 in Toshiba’s. It was able to distinguish diameter of 3mm in CATPHAN and ACR phantom, and 3.2 mm in AAPM phantom by GE’s; 3mm in CATPHAN, 4mm in ACR phantom and 6.4mm in AAPM phantom by Philips’s; 4mm in CATPHAN and ACR phantom, and 6.4mm in AAPM phantom by Toshiba’s. Conclusion When low contrast resolution of MDCT from each manufacturer is estimated, CNR of GE’s was the highest and it was able to distinguish the smallest whole in all phantoms. As the values show, GE’s was the best and then Philips’s. However, compare to those, Toshiba’s had the lowest CNR in all phantoms also it was restrictive to distinguish the smallest whole by sight. When low contrast resolution of three phantoms was estimated, CNR of CATPHAN and ACR phantom was the highest. CATPHAN phantom is the idealist phantoms to estimate low contrast resolution because of various diameters and attenuation coefficient. ACR phantom has variety of gap between diameters of wholes, but it was restrictive on distinguishing microscopic dimensions on scan images. AAPM phantom was not suited to measure low contrast resolution because the gap of holes is not closed each other and the lowest CNR values in MDCT.

X-CARE 사용시 안구와 유방의 선량 감소 효과와 영상 평가에 관한 연구

오현식(Hyun Sik Oh),유형태(Hyung Tae Yoo),남윤철(Yoon Cheul Nam),김문찬(Moon Chan Kim),한동균(Dong Kyoon Han) 대한CT영상기술학회 2011 대한CT영상기술학회지 Vol.13 No.2

목적 감수성이 높은 표재성 장기인 안구와 유방의 선량감소 효과가 있는 X-CARE를 대상으로 두부와 흉부 검사 시 선량감소효과와 영상의 화질을 평가하여 보고하고자 한다. 대상 및 방법 CT 장비는 Siemens사의 Dual Source Somatom Definition Flash를 사용하였으며, organ dose 측정을 위해 Female Alderson Radiation Therapy Phantom과 유리선량계를 사용하였다. 두부 검사시 안구의 표면, 두부 전면부, 후면부에서 측정하였으며, X-CARE를 사용하지 않을 때와 사용했을 때의 선량을 각각 2번씩 측정하여 비교하였다. 흉부 검사시에는 유방과 흉부의 전면부, 중간부, 후면부의 선량을 AEC 모드의 사용여부에 따라서 X-CARE를 사용하지 않을때와 사용했을 때의 선량을 각각 2번 측정하여 비교하였다. 영상의 화질 평가는 ACR 팬텀을 사용하여 얻어진 영상을 ImageJ 분석 프로그램을 이용하여 직선성과 균일도를 평가하였다. 통계분석은 Minicab을 통해 2 Sample t-test로 분석하여 선량의 유의성을 확인하였다. 결과 두부 검사시 안구의 표면선량과 전면부 선량은 X-CARE의 사용전에 비해 사용후에는 35.2%, 14.6% 감소하였으며, 후면부에서는 9.1% 증가하였다. 흉부 검사에서 AEC를 적용하지 않으면서 X-CARE를 사용하면 사용 전에 비해 유방, 흉부 전면부, 중간부의 선량은 각각 30.0%, 11.3%, 3.8% 감소하여 유의한 선량감소를 타나냈다(p<0.05). 그러나 후면부에서는 13.6%로 증가하였다. AEC를 적용하면서 X-CARE를 사용하면 사용전에 비해 유방, 흉부 전면부의 선량이 27.8%, 11.0% 감소하여 유의한 감소 효과를 나타냈다(p < 0.05). 그러나 흉부중간부와 후면부에서는 각각 1.4%, 4.5% 증가하였다. 영상의 화질 평가는 직선성과 균일도 모두 ACR에서 정한 기준 범위에 포함되었다. 결론 X-CARE는 영상의 화질 변화 없이 감수성이 높은 표재성 장기인 안구와 유방에 선량 감소 효과를 나타낼 수 있는 방법으로 여성과 소아 검사에 있어서 적극적인 사용을 권고한다. I. Purpose To measure absorbing dose reduction and evaluate image quality by glass dosimeter to eyeball and breast which are high sensitive superficial organs when examining head and chest using X-CARE. II. Meterial and Methods Dual Source Somatom Definition Flash of Siemens Company was usedfor the CT scan and Female Alderson Radiation Therapy Phantom and glass dosimeter were used for organ dose evaluation. ACR phantom was used for image quality evaluation and program Minicab was used for statistics analysis. For organ dose evaluation, we compared eyeball skin dose during head exam and the dose examined two times whether using X-CARE or not to the frontal and occipital partial of the head. For chest exam, we compared the dose examined two times whether using X-CARE or not to breast dose and the frontal, middle, rear side of chest following to use AEC mode or not. Using image j analysis program, we evaluated the linearity and uniformity the image gotten by ACR phantom. Through out Minitab, we confirmed dose significance by analyzing 2 Sample r-test. III. Result For dose evaluation of head exam, eyeball skin dose and the frontal dose show 35.2%, 14.6% reduction comparing before use and after use, the rear side shows 9.1% growth. To not apply AEC of chest exam, after use of X-CARE show the breast front, middle, rear dose were decreased 30.0%, 11.3%, 3.8% and the rear side increased 13.56% comparing before use. To apply AEC,however, after use of X-CARE show the breast dose and the frontal dose shows 27.8%, 11.0% reduction and the middle and rear side shows 1.4%, 4.5% growth. For image quality evaluation, it contains the standard range of ACR phantom The dose evaluated at the head shows all small differences(p < 0.05) and the breast dose and the front and rear side show small differences(p < 0.05), the middle partial shows no small differences(p > 0. 05) without the use of chest AEC. When the breast does and the frontal dose show small differences(p < 0.05) with the use of AEC, the middle and rear side show no small differences(p > 0. 05). IV. Conclusions X-CARE is the good way to show to eyeball and breast which are high sensitive superficial organswithout the image changing I think.

CT Guided Interventional Sturdy에서 Conventional Scan Mode 적용에 따른 선량 감소에 관한 연구

김지혜(Ji Hye Kim),김문찬(Moon Chan Kim),남윤철(Yoon Cheul Nam) 대한CT영상기술학회 2010 대한CT영상기술학회지 Vol.12 No.1

Purpose Recently CT guided interventional sturdy applied the helical scan mode which occurred overscanning dose. If you apply conventional scan mode, overscanning dose can be reduced. This sturdy intend to evaluate dose reduction and image quality from applying the protocol in conventional scan mode that decrease overscanning dose. Materials and methods All exams were proceeded on Aquilion 64 of Toshiba and used for ACR and CATPHAN phantom. the average number of pre. San was 1.0±0, scan range was an average of 9.2±2.6 cm in CT guided bone biopsy. the average number of pre. scan was 3.0±1.1, scan range lesion average of 11.1±3.3 cm in CT guided kidney RFA. we scanned repeatedly lesion area inserting the needle into the organ except for pre. scan. 7.2+3.2 times in CT guided bone biopsy, 14.0±5.1 times in CT guided kidney RFA. The conditions of helical scan mode protocol were as followed: 120 kVp, 70 mA, 0.6 sec, 2 mm slice thickness, 8 mm beam collimation, 0.938 pitch, and effective mAs was 45 mAs. to apply same CTDIvol with helical scan mode, the conditions of conventional scan mode were set on 120 kVp, 80 mA, 0.6 sec, 2 mm slice thickness, 8 mm beam collimation. We estimated the effect of dose reduction from effective dose derived from total DLP of conventional scan mode and thar of helical scan mode. ACR and CATVHAN phantom were used for evaluation of image quality. Results The estimate of dose showed total DPL 174.2±51.8 mGyㆍcm, effective dose 3.3±0.9 mSv in conventional scan mode, compared with total DPL 256.6±82.3 mGyㆍcm, effective dose 4.9±1.6 mSv in helical scan mode, which is reduced in 32.1±3.9% in CT guided bone biopsy. In CT guided kidney RFA, total DPL 465.3±139.7 mGyㆍcm, effective dose 7.0±2.0 mSv in conventional scan mode, compared with total DPL 647.5±200.6 mGyㆍcm, effective dose 9.7±3.0 mSv in helical scan mod, which is reduced in 29.1±6.8%. The result of noise is 15.4 HU in helical scan mode and 21.9 HU in conventional scan mode which is 6.5 HU higher d1an helical scan mode but almost did nor affect the image quality. Conclusion Accordingly, in conventional scan mode the ration of dose reduction was approximately 29.1~32.1% clue to decreased overscanning dose and the risk of stochastic effects and deterministic effects was not found in CT guided interventional sturdy. Therefore, we should sturdy more minimize dose for the patient while maintaining image quality through using optimal protocol.