A Study on Image Quality and Dose Comparison of Abdominal CT with Deep Learning Iterative Reconstruction Method and Model-Based Iterative Reconstruction Method

심현보(Hyeon-Bo Shim)이광현(Kwang-Hyun Lee),김령희(Ryeon-Hee Kim),박순규(Soon-Kyoo Park),심지나(Ji-Na Shim) 대한CT영상기술학회 2021 대한CT영상기술학회지 Vol.23 No.1

기존 반복적 재구성법의 단점을 보안하고 보다 낮은 선량으로 좋은 질의 영상을 얻기 위해 인공 신경망(Artificial Neural Network)으로 학습시킨 딥러닝 반복적 재구성법(Deep Learning Iterative Reconstruction, DLIR)이 개발되었으며 복부 CT에서 GE사의 딥러닝 반복적 재구성법(True Fidelity, TF)과 Siemens사의 모델기반 반복적 재구성법(Advanced Modeled Iterative Reconstruction, ADMIRE)을 적용한 영상의 화질평가와 선량감소 효과를 비교해 보고자 하였다. Phantom study는 CTDIvol(mGy)을 9.5로 동일하게 설정한 TF(TF-L, TF-M, TH-H)와 ADMIRE(1,2,3,4,5)이 적용된 단면영상으로 복부(A), 뼈(B) ROI를 설정하였고, Patient study는 본원에서 검사를 시행한 환자 30명의 복부조영 CT 검사에서 TF(TF-M, TF-H), ADMIRE 2 적용된 단면영상으로 복부대동맥(A), 간실질(B), 근육(C), 백그라운드(D) ROI를 설정하여 HU 및 SD값을 측정하고 SNR, CNR을 비교 평가하였다. Phantom study에서 T F-M은 ADMIRE 1, 3, 5 보다 Noise는 ROI A에서 221%, 139%, 40%, B는 104%, 66%, 19% 낮았고,(p<0.05) SNR은 ROI A에서 70%, 59%, 33%, B는 53%, 42%, 19% 높았다.(p<0.05) Patient study에서 TF-M은 ADMIRE 2 보다 Noise는 ROI A에서 7% 낮았지만 통계적으로 유의하지 않았고,(p=0.28) B는 21%, C는 45% 낮았다.(p<0.05) SNR은 ROI A에서 동일하였지만 통계적으로 유의하지않았고,(p=0.70) B는 20%, C는 28% 높았다.(p<0.05) CNR은 ROI A에서 22%, B는 25%, C는 22% 높았다.(p<0.05) 선량평가에서 TF가 적용된 환자의 평균 CTDIvol(mGy)은 4.73 ± 1.28, DLP(mGy⋅cm)는 281.43 ± 79.22, ADMIRE가 적용된 환자의 평균 CTDIvol(mGy)은 6.06 ± 1.22, DLP(mGy⋅cm)는 343.3 ± 81.34 이였고,(p<0.05) TF가 ADMIRE가 적용된 환자보다 CTDIvol(mGy)은 28%, DLP(mGy⋅cm)는 21% 낮았음을 알 수 있다.(p<0.05) 복부 CT 검사에서 딥러닝 반복적 재구성법이 적용된 TF 영상이모델기반 반복적 재구성법이 적용된 ADMIRE 영상보다 HU값의 변화는 없지만, Noise가 감소하며 SNR과 CNR은 증가하는 것으로 나타났다. 또한 선량이 같다면 딥러닝 반복적 재구성법이 적용된 TF 영상이 모델기반 반복적 재구성법이 적용된 ADMIRE영상보다 화질이 향상되고 이는 다시 말해 환자의 피폭 선량을 저감하는데 큰 기여를 한다고 할 수 있다 Deep Learning Iterative Reconstruction (DLIR), which was trained with an artificial neural network, was developed to secure the shortcomings of the traditional iterative reconstruction method and obtain a good quality image at a lower dose. The purpose of this study was to compare the effects of dose reduction and image quality evaluation using deep learning iterative reconstruction (True Fidelity; TF) and Siemens Advanced Modeled Iterative Reconstruction (ADMIRE). Phantom study is a axial image with TF (TF-L, TF-M, TH-H) a nd ADMIRE (1,2,3,4,5) with CTDIvol (mGy) set e qual to 9.5. Abdomen (A), Bone (B) ROI w as set, and the patient study was a axial image applied with TF (TF-M, TF-H) and ADMIRE 2 in the abdominal contrast CT scan of 30 patients who performed the examination in our hospital. Abdomen aorta (A), Hepatic parenchyma (B), muscle (C), background (D) ROI w as s et to measure HU, SD values, a nd SNR , CNR were compared. In t he P hantom study, TF-M w as c ompared with ADMIRE 1, 3, 5. Noise was 221%, 139%, 40% lower in ROI A, 104%, 66%, 19% lower in B.(p<0.05) SNR was 70%, 59%, 33% higher in ROI A, 53, 42%, 19% higher in B.(p<0.05) In patient study, TF-M was compared with ADMIRE 2. Noise was 7% lower in ROI A but it was not statistically significant.(p=0.28) B was 21%, C was 45% lower.(p<0.05) SNR was the same in ROI A but not statistically significant.(p=0.70) B was 20%, C was 28% higher.(p<0.05) CNR was ROI A 22%, B 25%, C 22% higher.(p<0.05) In dose assessment, the average CTDIvol (mGy) of patients with TF applied was 4.73 ± 1.28, DLP (mGy cm) was 281.43 ± 79.22, and the average CTDIvol (mGy) of patients with ADMIRE was 6.06 ± 1.22, DLP (mGy cm) was 343.3 ± 81.34.(p<0.05) It can be seen that TF was lower in CTDIvol (mGy) by 28% and DLP (mGy cm) by 21% than in patients with ADMIRE.(p<0.05) In conclusion, TF images on abdominal CT showed no change in HU values than ADMIRE images, but Noise decreased and SNR and CNR increased. If the dose is the same, the TF image is applied has better image quality than the ADMIRE image. It can be said that it contributes significantly to reducing the patient s exposure dose.

소아 Facial bone 30 CT 검사에서 기존의 spiral mode와 wide coverage volume axial mode의 비교

황의선(Eui sun Hwang),윤수정(Soo jung Yoon),박순규(Soon kyoo Park),임재식(Jea sik Lim) 대한CT영상기술학회 2016 대한CT영상기술학회지 Vol.18 No.2

목적 : 소아 사두증 환자의 facial bone 30 CT 검사에 있어서 넓은 detector를 이용한 wide coverage volume axial mode의 검사 방법을 기존의 spiral mode 검사 방법과 비교하여 그 유용성을 평가 하고자 한다. 대상 및 방법 : 본원에 내원 하여 사두증의 진단을 받기 위해 하게 되는 소아 facial bone 30 CT검사에서 기존의 검사 방법인 spiral mode와 새로운 기법인 wide coverage를 이용한 volume axial mode의 비교를 위해 CT 장비는 기존의 소아 facial bone 30 CT검사를 주로 하는 definition flash(Siemens) 장비와 volume axial mode가 되는 revolution CT(GE) 장비를 사용하였다. 기존의 소아 facial bone 30 검사 시 사용하는 mA와 kvp는 그대로 유지 하면서 소아 facial 팬텀을 이용하여 각 mode의 scan time, CTDIVOL, DLP를 각 장비에서 제공하는 값을 통해 비교하고 30 프로그램을 이용하여 VRT image를 비교 평가하였다. 또한 bone image quality, brain image quality 평가를 위해 SD값과 CT#, bone profile을 측정하여 분석하였다. 화질 평가를 위해서는 ACR 팬텀을 이용하여 linearity, uniformity, low and high contrast resolution을 측정하여 각 mode에서의 화질을 비교하여 volume axial mode의 유용성을 평가하였다. 결과 : 소아 사두증 환자의 평균 scan range인 16cm을 검사할 경우 기존의 spiral mode는 5.8sec가 소요되었다. Volume axial mode의 경우 0.28sec로 기존의 검사 방법에 비해 scan time이 95.2% 감소하였다 CTDIVOL은 2.6% 감소하였다. DLP는 기존의 검사 방법에 비해 15% 감소하였다. VRT image는 기존의 image와 차이가 없었으며, bone과 brain image으| 평가에서도 차이가 없는 것으로 분석되었다. ACR 팬텀을 이용한 화질 평가에서는 high contrast resolution항목에서 volume axial mode에서 높게 평가 되었으며 나머지 linearity, uniformity, low contrast resolution에서는 차이가 없는 것으로 측정되었다. 결론 : volume axial mode을 사용할 경우 기존의 검사 방법인 spiral mode와 비교하여 image quality의 저하 없이 적은 선량과 빠른 scan time으로 검사가 가능함을 알 수 있었다. 0.28sec라는 빠른 검사 시간은 움직임이 있는 소아의 검사에 있어서 매우 유용하게 사용될 것으로 사료된다. 특히 sedation이 불가능한 소아 환자의 경우 wide coverage를 이용한 vol axial mode는 sedation 없이 검사를 가능하게 할 수 있는 매우 유용한 검사 방법이 될 것으로 사료된다. Purpose : To compare wide coverage volume axial mode test methods utilizing wide detector in the pediatric plagiocephaly patient s facial bone 3D CT scan with the existing spiral mode test methods and to evaluate its usefulness Materials and Methods : In order to compare the existing spiral mode test methods with the new technique of volume axial mode test methods utilizing wide coverage in the pediatric plagiocephaly patient s facial bone 3D CT scan in this clinic, definition flash (Siemens) equipment which was mainly used for existing pediatric facial bone 3D CT scan, and revolution CT (GE) equipment which can utilize volume axial mode were used in the study. Using pediatric facial Phantom, scan time, CTDIVOL and DLP were compared by the value provided by each equipment, and VRT image was compared ande valuated by a 3D program. In addition, to evaluate image quality of bone and brain, SD values, CT#, and bone profile were measured and analyzed. In order to evaluate the image quality, linearity, uniformity, low and high contrast resolution were measured by using ACR phantom and the image quality in each mode were compared to evaluated the usefulness of volume axial mode. Result : When examining the average scan range of 16cm of pediatric plagiocephaly patients, the conventional spiral mode took 5.8sec. In case of Volume axial mode the scan time was 0.28sec which was 95.2% shorter than the conventional inspection method. CTDIVOL was decreased by 2.6%. DLP was decreased by 15% compared to the conventional test method. VRT image showed no difference with the existing image, and it was analyzed that there was no difference in the assessment of bone and brain image. In the quality analysis using the ACR phantom, volume axial mode showed high performance in high contrast resolution, but no differences were found in linearity, uniformity, and low contrast resolution. Conclusion : It was proved that when utilizing volume axial mode, the test can be performed with lower dose and shorter scan time without the degradation of image quality compared to the existing methods of spiral mode. The shorter scan time of 0.28sec is thought to be very useful in the examination of the children constantly moving. In particular, in case of the children who sedation cannot be applied, volume axial mode utilizing wide coverage is considered to be a very useful test method to enable the test without sedation.