Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis

Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8×8×2 cm³ containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm³ were compared. The water content was increased in patients compared with controls (GM: 244±21 vs. 194±10 a.u.; WM: 245±32 vs. 190±11 a.u.), FA decreased (GM: 0.226±0.038 vs. 0.270±0.020; WM: 0.337±0.044 vs. 0.402±0.011) and ADC increased [GM: 1134±203 vs. 899±28 (×10⁻⁶ mm²/s); WM: 901±138 vs. 751±17 (×10⁻⁶ mm²/s)]. Correlations of water content with FA and ADC in WM were strong (r=−0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=−0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=−0.88; P<0.00001) than in GM (r=−0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue.     

Diagnostic interplay of proton magnetic resonance spectroscopy and diffusion weighted images with apparent diffusion coefficient values in suspicious breast lesions

Aim of the work

To study the diagnostic performance of combined single voxel 1H-MRS and DW-MRI with ADC values as a non-contrast diagnostic tool, compared to the DCE-MRI, in suspicious breast lesions.

Correlation of the apparent diffusion coefficient value and dynamic magnetic resonance imaging findings with prognostic factors in invasive ductal carcinoma

Purpose

To evaluate the correlation of the mean and minimal apparent diffusion coefficient values (ADC_mean, ADC_minimal) and dynamic magnetic resonance imaging (MRI) findings with prognostic factors in invasive ductal carcinoma.

Materials and Methods

A total of 107 women with invasive ductal cancer underwent breast MRI. The ADC_mean and ADC_minimal of the cancers were computed. MRI findings were retrospectively evaluated according to the Breast Imaging Reporting and Data System (BI‐RADS) lexicon: mass or nonmass type, mass shape, mass margin, nonmass distribution, and enhancement pattern. Histological records were reviewed for tumor size, lymph node metastasis, histologic grade, and expression of estrogen receptors (ER), progesterone receptors (PR), c‐erbB‐2(HER2), Ki‐67, and epidermal growth factor receptors (EGFR). Correlations of ADC values and MR findings with prognostic factors were determined using the Mann–Whitney U‐test and the Kruskal–Wallis test.

Results

The mean ADC_minimal was 0.78 ± 0.24 (×10^?3 mm²/s), and the mean ADC_mean was 1.01 ± 0.23 (×10^?3 mm²/s). There was a significant correlation of the ADC_mean value with ER expression (P = 0.027) and HER2 expression (P = 0.018). There was no significant relationship between ADC_minimal and prognostic factors or between ADC_mean and traditional prognostic factors, PR, Ki‐67 and EGFR. The majority of the mass type lesions were less than 5 cm in size and the majority of nonmass type lesions were more than 2 cm in size (P = 0.022). The margin of mass was significantly associated with lymph node metastasis (P = 0.031), ER expression (P = 0.013), PR expression (P = 0.036), HER2 expression (P = 0.019), and EGRF expression (P = 0.041). The rim internal enhancement was significantly correlated with Ki‐67 expression (P = 0.008).

Conclusion

The low ADC_mean value was related to positive expression of ER and negative expression of HER2. A spiculated margin was related to a good prognosis, but rim enhancement was associated with a poor prognosis. J. Magn. Reson. Imaging 2011;33:102–109. © 2010 Wiley‐Liss, Inc.

     

Diffusion‐weighted imaging of prostate cancer: Correlation between apparent diffusion coefficient values and tumor proliferation

Purpose

To investigate whether the apparent diffusion coefficient (ADC) values of prostate cancer (PCa) are able to reflect tumor proliferation.

Materials and Methods

The clinical and pathological information for 38 patients with PCa and 33 patients with benign prostate hyperplasia (BPH) were studied. Examination of the patients was performed using a 1.5 T superconducting magnetic scanner equipped with a pelvic phased‐array multicoil. Diffusion‐weighted images (DWIs) were acquired using an echo‐planar imaging sequence. The ADC values of PCa, BPH, and peripheral zone (PZ) were calculated. The cellularity of PCa was recorded based on hematoxylin and eosin staining. The proliferating cell nuclear antigen (PCNA) was detected using an immunohistochemical technique.

Results

The ADC values of PCa, BPH, and PZ were 49.32 ± 12.68 × 10^?5 mm²/s, 86.73 ± 26.75 × 10^?5 mm²/s, and 126.25 ± 27.21 × 10^?5 mm²/s, respectively. The ADC values of PCa were lower than those of BPH and PZ (P < 0.05). The cellularity and PCNA labeling index (LI) of PCa were higher than those of BPH (P < 0.05). The ADC values of PCa were negatively correlated with those of cellularity and PCNA LI (r = ?0.646 and ?0.446, respectively; P < 0.05).

Conclusion

The ADC values of PCa can reveal the differences in proliferative activity between PCa and BPH. These values are therefore able to predict the proliferative rate of variously differentiated prostate cancers. J. Magn. Reson. Imaging 2009;29:1360–1366. © 2009 Wiley‐Liss, Inc.

     

MR DWI对急性胰腺炎的诊断价值

目的 探讨MR扩散加权成像(DWI)对急性胰腺炎(AP)的诊断价值.方法 回顾性分析50例AP及75例正常胰腺的MR资料,计算DWI序列b=800 s/mm2图像上胰腺与肝脏的信号强度比(SIR),测量胰腺的表观扩散系数(ADC),分别比较2组的SIR及ADC,并根据受试者工作特征(ROC)曲线确定最佳诊断阈值,评价SIR、ADC与MRI常规序列的诊断效能.结果 与正常胰腺相比,AP组SIR显著升高(2.06±0.48 vs 1.24±0.27,t=12.2,P<0.0001),ADC显著降低[(991±133)μm2/s vs(1153±149)μm2/s,t=-6.2,P<0.0001].最佳诊断阈值分别为SIR>1.51、ADC≤1039μm2/s.SIR的敏感度(92.0%)高于ADC(72.0%)及MRI常规序列(74.0%),SIR(88.0%)及MRI常规序列(93.3%)的特异度高于ADC(77.3%).结论 AP时水分子扩散受限,SIR诊断效能优于ADC及MRI常规序列,有利于AP的检出.     

评价ADC值对橄榄桥小脑萎缩的诊断价值

目的 评价表现扩散系数(ADC)值对橄榄桥小脑萎缩(OPCA)的诊断价值.方法 (1)选取经临床诊断为OPCA的52例患者及25列年龄匹配的正常人作为对照组,行常规MRI检查(T1 WI、T2 WI、DWI).根据MRI表现将患者分为轻度组和重度组.轻度组:小脑脑沟增多、脑干稍变细,桥脑无明显改变;重度组:小脑脑沟增多,桥脑、延髓橄榄萎缩,第四脑室、脑干基底池扩大.(2)选取桥脑、小脑中脚和小脑半球为感兴趣区(ROI)并测量其ADC值.运用单因素方差对3组ROI的ADC值进行统计分析.结果 3组ROI的ADC值差异有统计学意义(P＜0.05).OPCA患者组(轻度组及重度组)ROI的ADC值较对照组明显升高,差异有统计学意义(P＜0.05).OPCA重度组ROI的ADC值较轻度组升高,且重度组病程长于轻度组,差异均有统计学意义(P＜0.05).结论 桥脑、小脑中脚、小脑半球的ADC值对OPCA有重要的诊断价值,尤其对于MRI表现不明显的OPCA轻度组患者具有重要的诊断意义.     

Time evolution of cerebral perfusion and apparent diffusion coefficient measured by magnetic resonance imaging in a porcine stroke model

PURPOSE: To demonstrate the feasibility of sequential diffusion-weighted (DW) and perfusion-weighted (PW) magnetic resonance imaging (MRI) of a recently developed porcine stroke model and to evaluate the evolution of cerebral perfusion and the apparent diffusion coefficient (ADC) over time. Materials and Methods In five pigs, DW imaging (DWI) and PW imaging (PWI) was carried out for 7 hours after stroke onset, starting 1 hour after middle cerebral artery occlusion (MCAO). RESULTS: The DWI lesion volume increased significantly with time, and final DWI lesion volume correlated well with lesion area on histological sections (r = 0.910). T2 changes could be recognized 3 hours after stroke onset. At 1 hour the ADC ratio (ischemic lesion/contralateral side) was reduced to 0.81 in the caudate-putamen and to 0.87 in the cortex, and the cerebral blood flow ratio was reduced to 0.40 in the caudate-putamen and 0.51 in the cortex. CONCLUSION: The level of flow reduction in the caudate-putamen and the cortex after 1 hour is in good correlation with human thresholds of irreversible and reversible ischemic damage, and accordingly, this model might be a model for mechanisms of infarct evolution and therapeutic intervention.     

磁共振扩散成像及磁敏感加权成像在脊髓损伤中的应用

目前,脊髓MR成像常规检查是诊断脊髓损伤的最佳手段,能清楚地显示受损伤脊髓形态及信号改变,以此明确疾病,但是当MRI常规检查出现信号改变时往往提示脊髓损伤严重,并非病变的早期,使得病人错过最佳治疗时期。而MR扩散加权成像(DWI)和磁敏感加权成像(SWI)对脊髓损伤的早期诊断、治疗和预后均具有重要价值。对DWI及SWI在急慢性脊髓损伤中的应用情况及研究进展进行综述。     

Selecting an appropriate anisotropy index for displaying diffusion tensor imaging data with improved contrast and sensitivity.

A review of the behavior of different diffusion anisotropy indices (DAIs) to changes in diffusion anisotropy was undertaken and the limitations of several previously proposed DAIs are discussed. A mathematical representation of anisotropy sensitivity was used to enable image contrast and sensitivity to noise to be predicted. This technique was utilized to devise a new DAI, the gamma-variate anisotropy, which has a low sensitivity to noise and an improved contrast range for human brain imaging. This index can be easily modified for other applications, in that the range of anisotropy values to which it is highly sensitive can be altered. Magn Reson Med 44:117-121, 2000.     

Gd-EOB-DTPA对多b值肝脏DWI中表观弥散系数值的影响

目的 通过行肝脏多b值弥散加权成像（DWI）,观察注射钆塞酸二钠（Gd-EOB-DTPA）前、后不同时相表观弥散系数（ADC）值的变化,探讨增强后行DWI的可行性。方法 收集行Gd-EOB-DTPA肝脏增强的受检者126例,其中,例行体检的健康志愿者30名,肝脏病变患者96例（原发性肝癌25例、转移性肝癌20例、肝血管瘤28例、肝囊肿23例）,均经临床或病理证实。在Philips Achieva 1.5T双梯度超导MR成像系统上,行同相与正反相T1加权像闭气轴位平扫及轴位呼吸门控DWI。通过肘静脉向受检者注射0.025 mmol/kg Gd-EOB-DTPA,行动脉期、静脉期、3 min期、10 min期、20 min期、30 min期闭气轴位T1加权高分辨率各向同性容积激发序列（THRIVE）扫描,在5 min期,行轴位T2加权像脂肪抑制呼吸门控扫描,在15 min期,行轴位呼吸门控DWI后,接着行冠状位T2加权闭气扫描,在25 min期,行轴位呼吸门控DWI。平扫期、15 min期、25 min期的DWI参数完全一致,为单次激发自旋回波-平面回波成像（SE-EPI）序列,b值依次取0、50、300、600 s/mm2,扫描时间196 s。在EWS工作站上,通过ADC分析函数生成平扫期、15 min期、25 min期在b=50、300、600 s/mm2时的ADC图,测出正常肝脏、原发性肝癌、转移性肝癌、肝血管瘤、肝囊肿的ADC值,对同一b值下同一疾病在平扫期、15 min期及25 min期的ADC值进行t检验,分析是否存在统计学差异。结果 同一b值下同一疾病的ADC值在平扫期时最大,随着Gd-EOB-DTPA的注入,ADC值开始下降,然后上升,到了25 min期,ADC值与平扫期时基本一致,15 min期的ADC值最低,平扫期、15 min期、25 min期的ADC值差异无统计学意义（t=0.25~1.29,P均>0.05）。同一疾病同一时相的DWI中,随着b值的增加,ADC值不断下降,b值越小,ADC值越大。结论 静脉注射Gd-EOB-DTPA后,肝脏ADC值下降十分有限,增强后行DWI是可行的。     

Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis

PURPOSE: To evaluate the use of apparent diffusion coefficient (ADC) measurements based on diffusion-weighted MRI (DWI) to assess stage of liver disease. MATERIALS AND METHODS: A total of 31 patients who underwent both a liver biopsy and DWI and 132 patients who only underwent DWI were enrolled. Biopsy specimens were scored for fibrosis and necroinflammation according to the Knodell histology activity index (HAI). The 31 patients consisted of 21 patients with chronic hepatitis and 10 with cirrhosis (Child-Pugh stage A in nine and stage B in one), and the 132 patients consisted of 56 patients with cirrhosis (Child-Pugh stage A in 41, stage B in 10, and stage C in five), 42 with chronic hepatitis, and 34 with normal liver function. The ADCs in the liver parenchyma were measured using DWI with relatively low b factors (b = 0.01 and 128.01 seconds/mm(2)) and were compared among the HAI scores and among patients with cirrhosis, chronic hepatitis, and normal liver function. RESULTS: The ADCs decreased as the fibrosis score in the HAI increased, and the correlation was statistically significant (P < 0.0001). No relationship between the ADCs and the necroinflammation scores in the HAI was found. The ADCs decreased as the stage of liver disease progressed or as the Child-Pugh stage progressed, and these relationships were statistically significant (P < 0.0001). CONCLUSION: ADC measurements are potentially useful for the evaluation of fibrosis staging in the liver.     

使用ADC值评估正常及退变腰椎间盘的初步研究

目的:使用平均表观弥散系数(apparent diffusion coefficient,ADC)值可反映成人腰椎间盘中的水分子运动,探讨椎间盘ADC值和MR表现是否有相关性。方法:对28例患者及22名志愿者进行腰椎的MR弥散加权成像,测量每个椎间盘的ADC值。根据矢状位T2WI的MR表现,将椎间盘分为正常组和退变组。对比正常和退变椎间盘的平均ADC值,并对部位进行相关研究。结果:总计50名参与者中除3例因伪影明显未行ADC值测量外,余47例均成功行DWI及ADC值测量。正常和退变椎间盘的平均ADC值分别为2.32±0.54(×10-3mm2/s)和1.87±0.42(×10-3mm2/s)。ADC值与部位有明显的统计学相关性。结论:对比正常腰椎间盘,退变椎间盘的ADC值有明显的减低。且邻近骶尾部的椎间盘较头侧椎间盘的ADC值低。     

The role of dynamic contrast-enhanced and diffusion weighted magnetic resonance imaging in the female pelvis

Functional imaging by means of dynamic multiphase contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted magnetic resonance imaging (DW-MRI) is now part of the standard imaging protocols for evaluation of the female pelvis. DCE-MRI and DW-MRI are important MR imaging techniques which enable the radiologist to move from morphological to functional assessment of diseases of the female pelvis. This is mainly due to the limitations of morphologic imaging, particularly in lesion characterization, accurate lymph node staging, assessment of tumour response and inability to differentiate post-treatment changes from tumour recurrence.DCE-MRI improves the accuracy of T2WI in staging of endometrial cancer. It also helps differentiate tumour recurrence from radiation fibrosis in patients with cervical cancer. DCE-MRI improves characterization of cystic adnexal lesions and detection of small peritoneal implants in patients with ovarian cancer.DW-MRI is valuable in preoperative staging of patients with endometrial and cervical cancer, especially in detection of extra-uterine disease. It does increase reader's confidence for detection of recurrent disease in gynaecological malignancies and improves detection of small peritoneal implants in patients with ovarian cancer.In this review article we give an overview of both DCE-MRI and DW-MRI techniques, concentrating on their main clinical application in the female pelvis, and present a practical approach of the added value of these techniques according to the main pathological conditions, highlighting the pearls and pitfalls of each technique.     

Utilizing the diffusion-to-noise ratio to optimize magnetic resonance diffusion tensor acquisition strategies for improving measurements of diffusion anisotropy.

It is well known that quantitative anisotropy measurements derived from the diffusion tensor are extremely sensitive to noise contamination. The level of noise in the diffusion tensor imaging (DTI) experiment is usually measured from some estimate of the signal-to-noise ratio (SNR) in the component diffusion-weighted (DW) images. This measure is, however, highly dependent on experimental parameters, such as the diffusion attenuation b-value and the diffusion coefficient of the subject. Conversely, the diffusion-to-noise ratio (DNR), defined as the SNR of the calculated diffusion tensor trace map, provides a reliable estimate of noise contamination, which is largely independent of such parameters. In this work it is demonstrated how reliable anisotropy measurements can be obtained using an image acquisition strategy that optimizes the DNR of the DTI experiment. This acquisition scheme is shown to provide noise-independent measurements of typical diffusion anisotropy values found in the human brain.     

Diffusion-weighted imaging of the parotid gland: Influence of the choice of b-values on the apparent diffusion coefficient value

PURPOSE: To determine how the ADC value of parotid glands is influenced by the choice of b-values. MATERIALS AND METHODS: In eight healthy volunteers, diffusion-weighted echo-planar imaging (DW-EPI) was performed on a 1.5 T system, with b-values (in seconds/mm2) of 0, 50, 100, 150, 200, 250, 300, 500, 750, and 1000. ADC values were calculated by two alternative methods (exponential vs. logarithmic fit) from five different sets of b-values: (A) all b-values; (B) b=0, 50, and 100; (C) b=0 and 750; (D) b=0, 500, and 1000; and (E) b=500, 750, and 1000. RESULTS: The mean ADC values for the different settings were (in 10(-3) mm2/second, exponential fit): (A) 0.732+/-0.019, (B) 2.074+/-0.084, (C) 0.947+/-0.020, (D) 0.890+/-0.023, and (E) 0.581+/-0.021. ADC values were significantly (P <0.001) different for all pairwise comparisons of settings (A-E) of b-values, except for A vs. D (P=0.172) and C vs. D (P=0.380). The ADC(B) was significantly higher than ADC(C) or ADC(D), which was significantly higher than ADC(E). ADC values from exponential vs. logarithmic fit (P=0.542), as well as left vs. right parotid gland (P=0.962), were indistinguishable. CONCLUSION: The ADC values calculated from low b-value settings were significantly higher than those calculated from high b-value settings. These results suggest that not only true diffusion but also perfusion and saliva flow may contribute to the ADC.