Intravoxel Incoherent Motion Magnetic Resonance Imaging for Assessing Parotid Gland Tumors: Correlation and Comparison with Arterial Spin Labeling Imaging

Ma Gao,Xu Xiao-Quan,Zhu Liu-Ning,Jiang Jia-Suo,Su Guo-Yi,Hu Hao,Bu Shou-Shan,Wu Fei-Yun 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.2

Objective: To compare and correlate the findings of intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging and arterial spin labeling (ASL) imaging in characterizing parotid gland tumors. Materials and Methods: We retrospectively reviewed 56 patients with parotid gland tumors evaluated by MR imaging. The true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and fraction of perfusion (f) values of IVIM imaging and tumor-to-parotid gland signal intensity ratio (SIR) on ASL imaging were calculated. Spearman rank correlation coefficient, chi-squared, Mann-Whitney U, and Kruskal-Wallis tests with the post-hoc Dunn-Bonferroni method and receiver operating characteristic curve assessments were used for statistical analysis. Results: Malignant parotid gland tumors showed significantly lower D than benign tumors (p = 0.019). Within subgroup analyses, pleomorphic adenomas (PAs) showed significantly higher D than malignant tumors (MTs) and Warthin’s tumors (WTs) (p < 0.001). The D* of WTs was significantly higher than that of PAs (p = 0.031). The f and SIR on ASL imaging of WTs were significantly higher than those of MTs and PAs (p < 0.05). Significantly positive correlation was found between SIR on ASL imaging and f (r = 0.446, p = 0.001). In comparison with f, SIR on ASL imaging showed a higher area under curve (0.853 vs. 0.891) in discriminating MTs from WTs, although the difference was not significant (p = 0.720). Conclusion: IVIM and ASL imaging could help differentiate parotid gland tumors. SIR on ASL imaging showed a significantly positive correlation with f. ASL imaging might hold potential to improve the ability to discriminate MTs from WTs.

Reversal of a Large Ischemic Lesion with Low Apparent Diffusion Coefficient Value by Rapid Spontaneous Recanalization

Byeong Joo Choi,Taedong Ok,Yunjung Choi,이경열 대한신경초음파학회 2022 대한신경초음파학회지 (JNN) Vol.14 No.1

Cytotoxic edema at the site of a lesion following cerebral infarction is shown as a high signal on diffusion-weighted imaging, with a corresponding decreased apparent diffusion coefficient value on magnetic resonance imaging. These imaging findings have been used clinically as imaging markers of the infarction core, implying irreversible ischemic damage. However, reversal of diffusion lesions has been reported in patients with small lesions, relatively higher values of the apparent diffusion coefficient, or rapid endovascular reperfusion. Herein, we report a case of reversal of a large ischemic lesion on diffusion-weighted imaging with corresponding low apparent diffusion coefficient values in an acute middle cerebral artery infarction after immediate spontaneous recanalization. This case suggests that large ischemic lesions revealed by diffusion-weighted imaging may be reversed upon timely reperfusion, and could be considered as therapeutic targets.

Quantitative evaluation of the image quality using the fast nonlocal means denoising approach in diffusion-weighted magnetic resonance imaging with high b-value

Park Jaeyoung,Kang Chang-Ki,Lee Youngjin 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.3

Brain images acquired using the diffusion-weighted imaging (DWI) method indicate that the diagnostic efficiency of infarction improves and the noise increases as the b-value increases. In this study, we designed a fast nonlocal means (FNLM) noise reduction algorithm and evaluated its effectiveness for de-noising brain images with high b-values. The designed algorithm uses an approach that measures the similarity of local parts in an image, calculates weights based on the result, and uses the principle of reducing processing time using a simplification of the calculation. To demonstrate the effectiveness of the algorithm, we compared the qualities of the images obtained using FNLM with those obtained using previously developed algorithms with noise reduction performance and no-reference image-quality assessment parameters. The results of applying the FNLM noise reduction algorithm to DWI images obtained at high b-values indicated superior quantitative characteristics. In particular, the signal-to-noise ratio, coefficient of variation, and blind/referenceless image spatial quality evaluator (BRISQUE) results using the proposed FNLM algorithm were approximately 1.84, 1.44, and 1.21 times better than those of the noisy image, respectively. In conclusion, our results verified that the FNLM approach achieves higher noise reduction efficiency in diffusion-weighted magnetic resonance imaging.

Magnetic Resonance Imaging Evaluation of the Prostate in Normal Dogs

조유경,최호정,이기자,이영원 한국임상수의학회 2020 한국임상수의학회지 Vol.37 No.6

The aims of this study were to describe the appearance and size of the normal canine prostate using magnetic resonance (MR) imaging and to calculate the apparent diffusion coefficient (ADC) values. MR images were obtained from seven intact male beagle dogs using a 1.5 T MR unit. The sequences included pre- and post-contrast T1- and T2-weighted imaging with and without fat saturation. The signal intensity of the prostate was compared with the adjacent musculature, fat, and urine in the urinary bladder. We recorded the mean prostatic length, width, and height and the length of the sixth lumbar vertebral body (L6). In addition, the prostatic length (rL), width (rW), and height (rH) ratios to L6 were calculated. Diffusion-weighted images of the prostate were obtained and ADC values were calculated. The prostate was bilobed and oval-shaped, homogenous on T1-weighted images, and heterogeneous with radiating lines on T2-weighted images. Post-contrast T1-weighted sequences showed contrast enhancement of the central and radiating striations. The prostatic capsule was clearly identified on post-contrast T1-weighted images with fat saturation. The ADC values were 1.72-2.04 × 103mm2/sec (mean, 1.88 × 103mm2/sec). Knowledge of the normal appearance of the prostate on MR images is essential to assess prostatic diseases in dogs.

Effects of MR Parameter Changes on the Quantification of Diffusion Anisotropy and Apparent Diffusion Coefficient in Diffusion Tensor Imaging: Evaluation Using a Diffusional Anisotropic Phantom

김상준,최충곤,김정곤,윤성철,장건호,Ha-Kyu Jeong,Eun Ju Kim 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.2

To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom. Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman’s correlation analysis. The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value. A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.

Detection of Hepatic Lesion: Comparison of Free- Breathing and Respiratory-Triggered Diffusion- Weighted MR imaging on 1.5-T MR system

박혜영,조현제,김은미,허감,김용훈,이병훈 대한자기공명의과학회 2011 Investigative Magnetic Resonance Imaging Vol.15 No.1

Purpose : To compare free-breathing and respiratory-triggered diffusion-weighted imaging on 1.5-T MR system in the detection of hepatic lesions. Materials and Methods : This single-institution study was approved by our institutional review board. Forty-seven patients (mean 57.9 year; M:F = 25:22) underwent hepatic MR imaging on 1.5-T MR system using both free-breathing and respiratory-triggered diffusion-weighted imaging (DWI) at a single examination. Two radiologists retrospectively reviewed respiratory-triggered and free-breathing sets (B50, B400,B800 diffusion weighted images and ADC map) in random order with a time interval of 2 weeks. Liver SNR and lesion-to-liver CNR of DWI were calculated measuring ROI. Results : Total of 62 lesions (53 benign, 9 malignant) that included 32 cysts, 13hemangiomas, 7 hepatocellular carcinomas (HCCs), 5 eosinophilic infiltration, 2metastases, 1 eosinophilic abscess, focal nodular hyperplasia, and pseudolipoma of Glisson’s capsule were reviewed by two reviewers. Though not reaching statistical significance, the overall lesion sensitivities were increased in respiratory-triggered DWI [reviewer1: reviewer2, 47/62(75.81%):45/62(72.58%)] than free-breathing DWI [44/62(70.97%):41/62(66.13%)]. Especially for smaller than 1 cm hepatic lesions,sensitivity of respiratory-triggered DWI [24/30(80%):21/30(70%)] was superior to freebreathing DWI [17/30(56.7%):15/30(50%)]. The diagnostic accuracy measuring the area under the ROC curve (Az value) of free-breathing and respiratory-triggered DWI was not statistically different. Liver SNR and lesion-to-liver CNR of respiratorytriggered DWI (87.6±41.4, 41.2±62.5) were higher than free-breathing DWI (38.8±13.6, 24.8±36.8) (p value <0.001, respectively). Conclusion : Respiratory-triggered diffusion-weighted MR imaging seemed to be better than free-breathing diffusion-weighted MR imaging on 1.5-T MR system for the detection of smaller than 1 cm lesions by providing high SNR and CNR.

Comparison of Monoexponential, Biexponential, Stretched-Exponential, and Kurtosis Models of Diffusion-Weighted Imaging in Differentiation of Renal Solid Masses

Jianjian Zhang,Shiteng Suo,Guiqin Liu,Shan Zhang,Zizhou Zhao,Jianrong Xu,Guangyu Wu 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.5

Objective: To compare various models of diffusion-weighted imaging including monoexponential apparent diffusion coefficient (ADC), biexponential (fast diffusion coefficient [Df], slow diffusion coefficient [Ds], and fraction of fast diffusion), stretched-exponential (distributed diffusion coefficient and anomalous exponent term [α]), and kurtosis (mean diffusivity and mean kurtosis [MK]) models in the differentiation of renal solid masses. Materials and Methods: A total of 81 patients (56 men and 25 women; mean age, 57 years; age range, 30–69 years) with 18 benign and 63 malignant lesions were imaged using 3T diffusion-weighted MRI. Diffusion model selection was investigated in each lesion using the Akaike information criteria. Mann–Whitney U test and receiver operating characteristic (ROC) analysis were used for statistical evaluations. Results: Goodness-of-fit analysis showed that the stretched-exponential model had the highest voxel percentages in benign and malignant lesions (90.7% and 51.4%, respectively). ADC, Ds, and MK showed significant differences between benign and malignant lesions (p < 0.05) and between low- and high-grade clear cell renal cell carcinoma (ccRCC) (p < 0.05). α was significantly lower in the benign group than in the malignant group (p < 0.05). All diffusion measures showed significant differences between ccRCC and non-ccRCC (p < 0.05) except Df and α (p = 0.143 and 0.112, respectively). α showed the highest diagnostic accuracy in differentiating benign and malignant lesions with an area under the ROC curve of 0.923, but none of the parameters from these advanced models revealed significantly better performance over ADC in discriminating subtypes or grades of renal cell carcinoma (RCC) (p > 0.05). Conclusion: Compared with conventional diffusion parameters, α may provide additional information for differentiating benign and malignant renal masses, while ADC remains the most valuable parameter for differentiation of RCC subtypes and for ccRCC grading.

Diffusion-weighted imaging of biliopancreatic disorders: correlation with conventional magnetic resonance imaging.

Lee, Nam Kyung,Kim, Suk,Kim, Gwang Ha,Kim, Dong Uk,Seo, Hyung Il,Kim, Tae Un,Kang, Dae Hwan,Jang, Ho Jin WJG Press 2012 WORLD JOURNAL OF GASTROENTEROLOGY Vol.18 No.31

<P>Diffusion-weighted magnetic resonance imaging (DWI) is a well established method for the evaluation of intracranial diseases, such as acute stroke. DWI for extracranial application is more difficult due to physiological motion artifacts and the heterogeneous composition of the organs. However, thanks to the newer technical development of DWI, DWI has become increasingly used over the past few years in extracranial organs including the abdomen and pelvis. Most previous studies of DWI have been limited to the evaluation of diffuse parenchymal abnormalities and focal lesions in abdominal organs, whereas there are few studies about DWI for the evaluation of the biliopancreatic tract. Although further studies are needed to determine its performance in evaluating bile duct, gallbladder and pancreas diseases, DWI has potential in the assessment of the functional information on the biliopancreatic tract concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion, as indicated by a reduction in the apparent diffusion coefficient. The detection of malignant lesions and their differentiation from benign tumor-like lesions in the biliopancreatic tract could be improved using DWI in conjunction with findings obtained with conventional magnetic resonance cholagiopancreatography. Additionally, DWI can be useful for the assessment of the biliopancreatic tract in patients with renal impairment because contrast-enhanced computed tomography or magnetic resonance scans should be avoided in these patients.</P>

정상인 경수에 대한 확산텐서영상과 PC기법을 이용한 뇌척수액 속도 측정에 관한 연구

손봉경,곽소영,한용희,유장선,김옥화,고현윤,문치웅 대한자기공명의과학회 2013 Investigative Magnetic Resonance Imaging Vol.17 No.2

목적 : 정상인 경수에 대한 내부 부위별, 경수 레벨별 확산텐서영상과 뇌척수액 속도에 대한 정상인 기준을 마련하고자 하였다. 대상 및 방법 : 정상인을 대상으로 3T MRI를 이용하여 영상을 획득하였다. 확산텐서영상은 척수 레벨별로 각각 미리 정의해둔 백질의 후삭, 좌, 우 측삭과 회백질에 관심영역을 정하여 FA, MD에 대한 평균값을 구하였다. PC 기법을 이용한 뇌척수액속도 측정은 C2-3, C4-5, C5-6 척수레벨을 각각 스캔한 후, 척수 레벨별 최대 수축기 및 이완기 속도를 측정하였다. 결과 : FA 값과 MD 값에서 회백질과 백질의 내부 구조 사이에서는 통계적으로 유의한 차이 (p < 0.05)를 보였다. 경수 레벨별에서는 회백질의 FA 값에서 통계적으로 유의한 차이(p < 0.05)를 보였으며, 나머지 부분에서는 통계적으로 유의한 차이를 보이지 않았다 (p > 0.05). 뇌척수액 속도 측정 결과, 평균 최대 수축기 속도 5.18 ± 2.00 cm/sec, 평균 최대 이완기속도 -7.32 ± 3.18 cm/sec 이었으며, 경수 레벨별로는 통계적으로 유의한 차이를 보이지 않았다 (p > 0.05). 결론 : 정상인에 대한 경수 확산텐서영상의 정량적 수치 및 경수 레벨에 영향을 받지 않는 뇌척수액 속도에 대한 평균치를 알수가 있었다. Purpose : We report the results of the various parameters of diffusion tensor imaging (DTI) and CSF flow study ofthe cervical spinal cord using magnetic resonance (MR) imaging techniques. Materials and Methods: Intramedullary FA and MD were measured in the gray matter and posterior cord of thewhite matter and both lateral cords of the white matter at the C2-3, C4-5, C5-6 spinal levels. For the CSF flowstudy, velocity encoding was obtained at the C2-3, C4-5, C5-6 spinal levels. Results: There was a significant difference of the FA and MD between the white matter and gray matter (p <0.05). The FA of the gray matter was significantly different according to the cervical spinal cord levels (p < 0.05). Otherwise, the FA and MD parameters were not significantly different (p > 0.05). The mean peak systolic velocityand mean peak diastolic velocity were 5.18±2.00 cm/sec and -7.32±3.18 cm/sec, respectively from C2 to C6spinal cords. There was no significant difference in these velocities among the cervical spinal cord (p > 0.05). Conclusion: This basic information about DTI and CSF dynamics of the cervical spinal cord may be useful forassessing cervical spinal cord abnormalities using MR imaging.

Intravoxel incoherent motion diffusion-weighted MRI for predicting response to neoadjuvant chemotherapy in breast cancer

Kim, Yunju,Kim, Sung Hun,Lee, Hye Won,Song, Byung Joo,Kang, Bong Joo,Lee, Ahwon,Nam, Yoonho Elsevier 2018 Magnetic resonance imaging Vol.48 No.-

<P><B>Abstract</B></P> <P><B>Purpose</B></P> <P>To determine the diagnostic performance of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance imaging (MRI) parameters in predicting response to neoadjuvant chemotherapy (NAC) in breast cancer patients.</P> <P><B>Materials and methods</B></P> <P>Forty-six patients with stage II or III breast cancer underwent MRI including DW imaging with 10 <I>b</I> values before and after 2cycles of NAC. Apparent diffusion coefficient (ADC) and IVIM parameters (D, D*, and <I>f</I>) were obtained using histogram analysis derived from whole-tumor volumes. After surgery, imaging parameters were compared with histopathologic responses using the Miller-Payne grading system.</P> <P><B>Results</B></P> <P>Before NAC, D<SUB>mean</SUB>, D<SUB>50</SUB>, and D<SUB>75</SUB> were higher in good responders than in minor responders (<I>P</I> ≤0.043). After NAC, ADC<SUB>mean</SUB>, ADC<SUB>50</SUB>, ADC<SUB>75</SUB>, D<SUB>mean</SUB>, D<SUB>25</SUB>, D<SUB>50</SUB>, and D<SUB>75</SUB> were higher in good responders (<I>P</I> ≤0.037). Skewness of ADC and D were lower in good responders after NAC (<I>P</I> ≤0.005). Most histogram metrics of posttreatment ADC and D had similar AUC values with reasonable accuracy for prediction of good response (AUC≥0.7, <I>P</I> <0.05).</P> <P><B>Conclusion</B></P> <P>D and ADC are useful for the prediction of response to NAC in breast cancer patients. Additional information is obtained by application of the IVIM model in DW imaging analysis and histogram analysis using whole-tumor volume data.</P>