Visualization of myocardial microstructure using high-resolution T*2 imaging at high magnetic field.

The analysis of myocardial microstructure in vivo is important for the determination of myocardial contractility and function. The purpose of the present study was to demonstrate that high-resolution T*2 imaging has the potential to visualize the microstructure of beating, isolated rat hearts. To perform T*2 imaging, a multiple gradient-echo sequence was implemented on an 11.75 Tesla microscopy system. An in-plane resolution of 78 microm and a slice thickness of 250 microm were achieved in 24 min. In comparison to histological sections, the T*2 maps showed an excellent spatial correspondence to the myocardial fiber structure. To demonstrate the utility of this technique, morphologic alterations in myocardial microstructure were investigated in hearts with chronic myocardial infarction. Scar tissue and the extent of the infarcted region were clearly visualized and quantified using high-resolution T*2 imaging.     

In vivo diffusion-weighted MRI of the breast: potential for lesion characterization

PURPOSE: To investigate the potential of apparent diffusion coefficients (ADCs) in characterizing breast lesions in vivo.MATERIALS AND METHODS: Two diffusion-weighted (DW) sequences were implemented on a 1.5 Tesla scanner, with low b-value orthogonal and high b-value tetrahedral sensitized sequences. The orthogonal sequence was evaluated on 16 normal volunteers and 23 patients with known lesion types (six benign and 17 malignant). The tetrahedral sequence was evaluated on a smaller number of subjects: two normal, two malignant, and two benign.RESULTS: The mean value of the ADC of the malignant tumors was reduced compared to that of the benign lesions and normal tissue. This finding was related to the increased cellularity of the malignant lesions. The ADC values were elevated for all tissue types with the low b-value sequence as compared to the high b-value sequence, indicating contributions from perfusion effects at the low b-values.CONCLUSION: The study clearly shows that DW-MRI can help characterize breast lesions in vivo.     

Evaluation of locally recurrent pelvic malignancy: performance of T2- and diffusion-weighted MRI with image fusion

PURPOSE: To evaluate the performance of T2- and diffusion-weighted magnetic resonance imaging (MRI) with image fusion for detection of locally recurrent pelvic malignancy. MATERIALS AND METHODS: The study group consisted of 28 patients (27 female, 1 male) who underwent pelvic MRI at 1.5 T after treatment of pelvic malignancy. MR images were reviewed independently by three blinded readers. The performance of the four sequences for detecting local recurrence was evaluated using receiver operating characteristic analysis: T2-weighted fast spin-echo (FSE), diffusion-weighted echo-planar imaging (DWI), dynamic contrast-enhanced (DCE) fat-suppressed T1-weighted spoiled gradient echo (SPGR), and T2-DWI with image fusion, the latter created using OsiriX Medical Imaging Software. RESULTS: Local recurrence was confirmed at biopsy in 16 patients. Twelve patients showed no evidence of recurrence on two consecutive MRI studies. The Az value for T2-DWI with image fusion (0.949) was statistically greater than that for T2-weighted FSE (0.849) (P<0.05). The sensitivity and specificity was 87.5% and 47.2%, respectively, for T2-weighted FSE, 100.0% and 50.0% for DWI, 95.8% and 58.3% for DCE fat-suppressed T1-weighted SPGR, and 93.8% and 72.2% for T2-DWI with image fusion. CONCLUSION: For depicting locally recurrent pelvic malignancy, T2-DWI with image fusion outperforms standard T2-weighted FSE and DWI and is comparable to DCE fat-suppressed T1-weighted SPGR.     

T2-weighted and diffusion-weighted MRI for discriminating benign from malignant focal liver lesions: diagnostic abilities of single versus combined interpretations

Purpose:

To compare the diagnostic accuracies of diffusion‐weighted imaging (DWI), T2‐weighted imaging (T2WI), and the combination of both sequences in discriminating benign from malignant focal liver lesions (FLLs).

Materials and Methods:

In all, 166 patients with 269 FLLs (153 benign and 116 malignant) were retrospectively evaluated. Two abdominal readers visually assessed the DWI, T2WI, and the combined (DWI+T2WI) image sets in an independent and blinded manner. The diagnostic abilities of each image set in discriminating the benign from the malignant FLLs set were compared using a binary logistic regression model. Pathologic results, consensus reading, and follow‐up imaging were used as the reference standard.

Results:

The overall characterization accuracy in all lesions of the combined set (80.3%) was significantly higher than those of the T2WI set (68.8%) and DWI set (73.2%) (combined vs. T2WI, P < 0.001; combined vs. DWI, P = 0.001), while there was no significant difference between the T2WI and DWI sets (P = 0.058). All image sets were more accurate in the characterization of malignant FLLs than of benign FLLs (P < 0.001).

Conclusion:

T2WI and DWI are complementary in discriminating benign from malignant FLLs; their combination improves diagnostic confidence. J. Magn. Reson. Imaging 2012;35:1388–1396. © 2012 Wiley Periodicals Inc.     

Multishot diffusion-weighted SPLICE PROPELLER MRI of the abdomen.

Multishot FSE (fast spin echo)-based diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI offers the potential to reduce susceptibility artifacts associated with single-shot DW-EPI (echo-planar imaging) approaches. However, DW-PROPELLER in the abdomen is challenging due to the large field-of-view and respiratory motion during DW preparation. Incoherent signal phase due to motion will violate the Carr-Purcell-Meiboom-Gill (CPMG) conditions, leading to destructive interference between spin echo and stimulated echo signals and consequent signal cancellation. The SPLICE (split-echo acquisition of FSE signals) technique can mitigate non-CPMG artifacts in FSE-based sequences. For SPLICE, spin echo and stimulated echo are separated by using imbalanced readout gradients and extended acquisition window. Two signal families each with coherent phase properties are acquired at different intervals within the readout window. Separate reconstruction of these two signal families can avoid destructive phase interference. Phantom studies were performed to validate signal phase properties with different initial magnetization phases. This study evaluated the feasibility of combining SPLICE and PROPELLER for DW imaging of the abdomen. It is demonstrated that DW-SPLICE-PROPELLER can effectively mitigate non-CPMG artifacts and improve DW image quality and apparent diffusion coefficient (ADC) map homogeneity.     

Two-component diffusion tensor MRI of isolated perfused hearts.

Nonmonoexponential MR diffusion decay behavior has been observed at high diffusion-weighting strengths for cell aggregates and tissues, including the myocardium; however, implications for myocardial MR diffusion tensor imaging are largely unknown. In this study, a slow-exchange-limit, two-component diffusion tensor model was fitted to diffusion-weighted images obtained in isolated, perfused rat hearts. Results indicate that there are at least two distinct components of anisotropic diffusion, characterized by a "fast" component whose principal diffusivity is comparable to that of the perfusate, and a highly anisotropic "slow" component. It is speculated that the two components correspond to tissue compartments and have a general agreement with the orientations of anisotropy, or fiber orientations, in the myocardium. Moreover, consideration of previous studies of myocardial diffusion suggests that the presently observed fast component may likely be dominated by diffusion in the vascular space, whereas the slow component may include the intracellular and interstitial compartments. The implications of the results for myocardial fiber orientation mapping and limitations of the current two-component model used are also discussed.     

Evaluation of lymph node metastases: comparison of gadofluorine M-enhanced MRI and diffusion-weighted MRI in a rabbit VX2 rectal cancer model

Purpose:

To compare the diagnostic performance of a diffusion‐weighted imaging (DWI) dataset and a gadofluorine M‐enhanced imaging dataset for identifying lymph node (LN) metastases in a rabbit rectal cancer model.

Materials and Methods:

VX2 carcinomas were injected into the rectum of 26 rabbits. Four weeks later, T2‐weighted imaging (T2WI), pre‐T1WI, DWI, and post‐T1WI were performed. Two radiologists independently reviewed the DWI set (T2WI, pre‐T1WI, DWI) and the gadofluorine M set (T2WI, pre‐ and post‐T1WI) and recorded their confidence scores for LN metastasis on a per‐LN basis. Receiver operating characteristic (ROC) analysis was performed to compare the area under the ROC curve (A_z) of the two imaging sets. Histopathologic results were used as the reference standard.

Results:

The A_z and sensitivity of the gadofluorine M set were comparable to those of the DWI set (A_z, for reader 1, 0.849, 0.829, P = 0.571; for reader 2, 0.923, 0.876, P = 0.212; sensitivity, for reader 1, 97%, 97%; for reader 2, 97%, 92%, P = 0.304). The specificity of the former was greater than that of the latter (for reader 1, 65%, 53%, P = 0.0003; for reader 2, 81%, 68%, P = 0.01).

Conclusion:

Gadofluorine M‐enhanced images provided greater specificity than DWI for identifying LN metastases, whereas the A_z and sensitivity of the former were comparable to those of the latter. J. Magn. Reson. Imaging 2012;35:1179‐1186. © 2012 Wiley Periodicals, Inc.     

Prostate cancer: utility of fusion of T2-weighted and high b-value diffusion-weighted images for peripheral zone tumor detection and localization

Purpose:

To retrospectively assess the utility of fusion of T2‐weighted images (T2WI) and high b‐value diffusion‐weighted images (DWI) for prostate cancer detection and localization.

Materials and Methods:

In this IRB‐approved HIPAA‐compliant study, 42 patients with prostate cancer underwent MRI including multiplanar T2WI and axial DWI before prostatectomy. Two independent radiologists first assessed multiplanar T2WI and axial DWI_b‐1000 images and recorded whether tumor was present in each sextant. Axial T2WI was then fused with axial DWI_b‐1000 images, and the radiologists re‐evaluated each sextant for tumor. Accuracy was compared using generalized estimating equations based on a binary logistic regression model.

Results:

The accuracy, sensitivity, specificity, PPV, and NPV for tumor detection on a sextant‐basis using separate and fused image sets was 65.1%, 50.8%, 78.0%, 67.8%, and 63.6% and 71.0%, 60.8%, 80.3%, 73.7%, and 69.3%, respectively, for reader 1, and 54.0%, 42.5%, 64.4%, 52.0%, and 55.2%, and 61.1%, 56.7%, 65.2%, 59.6%, and 62.3%, respectively, for reader 2. The improvements in accuracy, sensitivity, and NPV using fused images were statistically significant for both readers, as was the improvement in PPV for reader 2 (P ranging from <0.0001 to 0.041). With either separate or fused images, there was greater sensitivity for tumors of higher grade or larger size (P ranging from <0.001 to 0.099).

Conclusion:

Fusion of T2WI and high b‐value DWI resulted in significant improvements in sensitivity and accuracy for tumor detection on a sextant‐basis, with similar specificity. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

DWI、T2加权像及综合应用对前列腺癌诊断价值的研究

目的:通过对分别应用T2WI及DWI两种成像方法及其综合应用对前列腺癌进行定性诊断的比较,探讨两种方法各自及综合应用对前列腺癌的诊断价值。方法:应用1.5T MR成像仪对42例前列腺疾病患者进行前列腺磁共振高分辨成像,其中前列腺癌15例,良性病变包括良性前列腺增生及慢性前列腺炎症等27例。在MRI常规成像基础上行DWI扫描,扩散敏感系数(b)值分别为0、1000s/mm2。采用盲法阅片,按照前列腺6分区法将两种MR技术分别所得图像数据分区评估测量并采用5分制评分,根据两种技术的5分制评分进行T2加权像综合DWI方法评分,将所得结果与病理结果对照。利用SPSS 11.5分别做ROC曲线分析比较,计算各组方法诊断的敏感度、特异度及准确度等。结果:各组诊断方法的敏感度、特异度及ROC曲线下面积(Az)如下:T2WI:88.2%,67.2%和0.848±0.030,最佳诊断界值为3;ADC诊断:82.4%,81.6%和0.860±0.033,最佳界值为4;ADC结合T2WI诊断:78.4%,92.5%和0.922±0.021,最佳界值为4.结论:通过独立评估T2WI及DWI两种方法均可以有效诊断前列腺癌;两种成像方法综合应用诊断前列腺癌的准确度显著高于两种成像技术独立诊断,其诊断结果与病理分析一致性较好。     

Comparison of quantitative T2 mapping and diffusion-weighted imaging in the normal and pathologic prostate.

In this study, diffusion-weighted images of the human prostate were successfully obtained, enabling quantification of apparent diffusion coefficients (ADCs) in normal and pathologic regions. A dual acquisition fast spin-echo sequence was used for accurate T2 calculation. T2 values were significantly higher in the peripheral zone than the central gland (P = 0.015). No significant correlations were found in either normal or pathologic tissue between ADC values and relaxation rates for all three gradient directions and the orientationally averaged water diffusion coefficient. Evidence suggesting that diffusional anisotropy is present in normal prostatic tissue is also detailed, with significant differences noted between the z-component and both the x- and y-components of the ADC for peripheral zone (P < 0.040) and central gland (P < 0.001).     

Analysis and generalized correction of the effect of spatial gradient field distortions in diffusion-weighted imaging.

Nonuniformities of magnetic field gradients can cause serious artifacts in diffusion imaging. While it is well known that nonlinearities of the imaging gradients lead to image warping, those imperfections can also cause spatially dependent errors in the direction and magnitude of the diffusion encoding. This study shows that the potential errors in diffusion imaging are considerable. Further, we show that retrospective corrections can be applied to reduce these errors. A general mathematical framework was formulated to characterize the contribution of gradient nonuniformities to diffusion experiments. The gradient field was approximated using spherical harmonic expansion, and this approximation was employed (after geometric distortions were eliminated) to predict and correct the errors in diffusion encoding. Before the corrections were made, the experiments clearly revealed marked deviations of the calculated diffusivity for fields of view (FOVs) generally used in diffusion experiments. These deviations were most significant farther away from the magnet's isocenter. For an FOV of 25 cm, the resultant errors in absolute diffusivity ranged from approximately -10% to +20%. Within the same FOV, the diffusion-encoding direction and the orientation of the calculated eigenvectors can be significantly altered if the perturbations by the gradient nonuniformities are not considered. With the proposed correction scheme, most of the errors introduced by gradient nonuniformities can be removed.     

弥散加权成像与MRI增强诊断表皮样囊肿的比较研究

目的:比较弥散加权成像(DWI)与MRI增强(CE-MRI)对表皮样囊肿的检出敏感性,评价DWI的临床应用价值.方法:对59例初次检查及66例术后复查疑似表皮样囊肿的患者行回顾性研究,所有病例均行常规序列[T1 WI、Tz WI、液体衰减反转恢复序列(FLAIR)]、弥散加权成像(DWI)和钆对比剂增强扫描(CE-MRI)检查.将所有图像分为DWI结合常规序列(Ⅰ组)、CE-MR1结合常规序列(Ⅱ组)及DWI联合CE-MRI并结合常规序列(Ⅲ组)三组进行判断,诊断结果与手术病理进行比较,判定三组检查方法的敏感性,组间比较采用配对资料的x2检验.另外选择32例经病理及随访观察证实的蛛网膜囊肿做对照,分析信号特征并测量ADC值,与表皮样囊肿ADC值的比较采用配对t检验.结果:Ⅰ组、Ⅱ组诊断表皮样囊肿的敏感性分别为90.5％、57.8％,二者具有明显统计学差异(x2=25.714,P＜0.01).Ⅲ组诊断表皮样囊肿的敏感性为91.8％,与11组具有明显统计学差异(x2=30.250,P＜0.01),与Ⅰ组没有统计学差异(x2=0.250,P＞0.05).病理证实的88例表皮样囊肿DWI均呈明显高信号,32例蛛网膜囊肿DW1均呈明显低信号,表皮样囊肿的ADC值(1.06士0.21×103)mm2/s明显低于蛛网膜囊肿的的ADC值(3.24±0.39×101)mm2/s,两者比较差异有统计学意义(t =-3.647,P＜0.01).结论:DWI较MRI增强检查对表皮样囊肿具有较高的检出率,在与蛛网膜囊肿的鉴别及判断表皮样囊肿复发上能提供有价值的诊断信息.     

Cardiac motion in diffusion-weighted MRI of the liver: artifact and a method of correction

Purpose:

To characterize cardiac motion artifacts in the liver and assess the use of a postprocessing method to mitigate these artifacts in repeat measurements.

Materials and Methods:

Three subjects underwent breathhold diffusion‐weighted (DW) scans consisting of 25 repetitions for three b‐values (0, 500, 1000 sec/mm²). Statistical maps computed from these repetitions were used to assess the distribution and behavior of cardiac motion artifacts in the liver. An objective postprocessing method to reduce the artifacts was compared with radiologist‐defined gold standards.

Results:

Signal dropout is pronounced in areas proximal to the heart, such as the left lobe, but also present in the right lobe and in distal liver segments. The dropout worsens with b‐value and leads to overestimation of the diffusivity. By reference to a radiologist‐defined gold standard, a postprocessing correction method is shown to reduce cardiac motion artifact.

Conclusion:

Cardiac motion leads to significant artifacts in liver DW imaging; we propose a postprocessing method that may be used to mitigate the artifact and is advantageous to standard signal averaging in acquisitions with multiple repetitions. J. Magn. Reson. Imaging 2012;318‐327. © 2011 Wiley Periodicals, Inc.     

Using a 2D multibreath-hold susceptibility-weighted imaging to visualize intratumoral hemorrhage of hepatocellular carcinoma at 3T MRI: Correlation with pathology

Purpose:

To assess the value of 2D multibreath‐hold susceptibility‐weighted imaging (SWI) for visualizing intratumoral hemorrhage of hepatocellular carcinoma (HCC) and correlate with pathological results.

Materials and Methods:

Fifty‐eight patients with 65 HCCs underwent T1‐, T2‐, T2*‐weighted imaging and SWI. The ability to detect intratumoral hemorrhage for each imaging technique was evaluated. A radiologic‐pathological correlation was performed.

Results:

The area under the receiver operator characteristic (ROC) curve (Az value) for SWI (Az = 0.941) was significantly greater than that for T1WI (Az = 0.748) and T2WI (Az = 0.700) (P = 0.000). When compared with T2*, SWI had slightly higher sensitivity and equal specificity, but the Az value was not significantly different (P = 0.768). The total number of hemorrhages detected by SWI was greatest by factors of 13.3, 6.7, and 2.2 compared to T1WI, T2WI, and T2*, respectively. SWI detected more microbleeds (585 in 25 HCCs) than T1WI (13 in 5 HCCs), T2WI (66 in 11 HCCs), and T2* (238 in 21 HCCs).

Conclusion:

SWI can accurately visualize internal hemorrhages and provide valuable information regarding the internal architecture of HCC. J. Magn. Reson. Imaging 2012;36:900–906. © 2012 Wiley Periodicals, Inc.     

Subacute sclerosing panencephalitis: relationship between clinical stage and diffusion-weighted imaging findings

PURPOSE: To investigate the relationship between clinical stages and apparent diffusion coefficient (ADC) changes in the brain of patients with subacute sclerosing panencephalitis (SSPE). MATERIALS AND METHODS: A total of 18 patients with stage II (N = 11) and III (N = 7) SSPE and 11 age-matched controls underwent routine MRI and diffusion-weighted imaging (DWI). The ADC values were automatically calculated. Seven distinct neuroanatomic structures (frontal, parieto-occipital, and cerebellar white matter; deep white matter; thalamus; basal ganglia; and brainstem) were selected for analysis in the patient and control groups. RESULTS: Hyperintensities in the periventricular and subcortical white matters on T2-weighted images and ADC maps were detected in 63.6% of patients with stage II and in all patients with stage III. There were significant differences between stage II and III patients and also between patients and control group in ADC values that obtained from all locations. The highest mean ADC values were calculated in stage III patients. Although MRI and DWI findings were normal in four patients with stage II disease, ADC values were significantly increased when compared with controls. CONCLUSION: The stage of disorder may be independent of DWI appearance during the early stage (stages I and II), even though the brain is affected. Therefore, DWI and ADC values supplemental to routine MRI should also be utilized for lesion detection and definition to enhance diagnostic accuracy in patients with SSPE.     

High-resolution 7T MRI of the human hippocampus in vivo

Purpose

To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging.

Materials and Methods

Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16‐channel head coil. Sequences included a full field of view T1‐weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA) = 08:58), T2*‐weighted 2D fast field echo (T2*W 2D FFE: TA = 05:20), and susceptibility‐weighted imaging (SWI: TA = 04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.

Results

T1W 3D TFE images with 700 μm isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in‐plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in‐plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus.

Conclusion

In vivo 7T MR imaging can take advantage of higher signal‐to‐noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy. J. Magn. Reson. Imaging 2008;28:1266–1272. © 2008 Wiley‐Liss, Inc.     

A comparison of images generated from diffusion-weighted and diffusion-tensor imaging data in hyper-acute stroke

PURPOSE: To compare isotropic (combined diffusion-weighted image [CMB], apparent diffusion coefficient [ADC], TRACE, exponential ADC [eADC], and isotropically-weighted diffusion image [isoDWI]) and anisotropic (relative anisotropy [RA], fractional anisotropy [FA], and volume ratio [VR]) diffusion images collected with fast magnetic resonance (MR) diffusion-weighted (DWI) and diffusion-tensor (DTI) acquisition strategies (each less than one minute) in hyper-acute stroke. MATERIALS AND METHODS: Twenty-one patients suffering from ischemic stroke-imaged within six hours of symptom onset using both DWI and DTI-were analyzed. Regions of interest were placed in the ischemic lesion and in normal contralateral tissue and the percent difference in image intensity was calculated for all nine generated images. RESULTS: The average absolute percent changes for the isotropic strategies were all > 38%, with isoDWI found to have a difference of 50.7% +/- 7.9% (mean +/- standard error, P < 0.001). The ADC maps had the most significant difference (-42.4% +/- 2.0%, P < 0.001, coefficient of variation = 0.22). No anisotropic images had significant differences. CONCLUSION: Anisotropic maps do not consistently show changes in the first six hours of ischemic stroke; therefore, isotropic maps, such as those obtained using DWI, are more appropriate for detecting hyper-acute stroke. Anisotropic images, however, may be useful to differentiate hyper-acute stroke from acute and sub-acute stroke.     

Breast diffusion-weighted MRI: comparison of tetrahedral versus orthogonal diffusion sensitization for detection and localization of mass lesions

Purpose:

To evaluate the potential of tetrahedral diffusion‐weighted imaging (DWI) compared to orthogonal DWI for detection and localization of early enhanced breast mass lesions at 1.5T.

Materials and Methods:

Sixty‐seven consecutive patients (mean age 51.7 years, range 14–84 years) with 68 solitary early enhanced breast lesions suspicious for cancer on dynamic contrast‐enhanced magnetic resonance imaging (MRI) were enrolled in this retrospective study. Two radiologists independently observed maximum intensity projection images of orthogonal and tetrahedral DWI and the diagnostic accuracy and background tissue visibility between two DWI techniques were compared. Contrast‐enhanced MRI was used as the reference standard. Background tissue visibility was assessed based on whether the “breast quadrant” and “skin line” were determined. A phantom validation study for apparent diffusion coefficient (ADC) values was also conducted.

Results:

Sensitivity (93%) and specificity (96%) on tetrahedral DWI were equivalent to those on orthogonal DWI (sensitivity, 88%; specificity, 95%). Background tissue was more easily determined with tetrahedral DWI (breast quadrant, 90%; skin lines, 95%) than with orthogonal DWI (breast quadrant, 61%; skin lines, 16%). ADC values of tetrahedral DWI were highly correlated with those of orthogonal DWI.

Conclusion:

Tetrahedral DWI provided equivalent detectability of mass lesions with improved visibility of surrounding anatomical structure. J. Magn. Reson. Imaging 2011;33:1375–1381. © 2011 Wiley‐Liss, Inc.     

Time course study on the effects of iodinated contrast medium on intrarenal water transport function using diffusion-weighted MRI

Purpose:

To assess the effects of intravenous‐injected iodinated contrast medium (CM) on intrarenal water diffusion using noninvasive diffusion‐weighted MRI (DW‐MRI).

Materials and Methods:

Ten New Zealand White rabbits were randomized to receive a 6 mL/kg body weight intravenous injection of clinically used iopamidol‐370 (n = 7) or an equivalent amount of 0.9% physiological saline (n = 3). A sequential DW‐MRI was performed to estimate the intrarenal apparent diffusion coefficient (ADC) at 24 h before and 1 h, 24 h, 48 h, and 72 h after administration.

Results:

Iopamidol produced a progressive ADC reduction in inner stripes of the renal outer medulla (IS) by 13.92% (P = 0.05) at 1 h, 17.52% (P = 0.02) at 24 h, 20.23% (P = 0.01) at 48 h and 16.31% (P = 0.04) at 72 h after injection. Cortical ADC was decreased by 14.14% (P = 0.01) at 48 h and 14.12% (P = 0.01) at 72 h after injection. Iopamidol produced slight decrease of ADCs in outer stripes of the outer medulla (OS) and inner medulla (IM) of kidney but without statistical difference. In control group, no significant ADC changes was observed in each anatomic compartment due to saline injection (P > 0.05).

Conclusion:

As demonstrated by DW‐MRI, intravenous iopamidol injection resulted in a successive reduction of intrarenal water diffusion, particularly in IS of kidney. This MR technique may be used as a noninvasive tool to perform a time course study of the pathogenesis associated with contrast‐induced nephropathy (CIN). J. Magn. Reson. Imaging 2012;35:1139‐1144. © 2012 Wiley Periodicals, Inc.     

Myocardial and liver iron status using a fast T*2 quantitative MRI (T*2qMRI) technique.

This work demonstrates the use of a fast and precise methodology for evaluating myocardial and liver iron status in multitransfused thalassemic patients by means of a fast T(2) (*) quantitative MRI (T(2) (*)qMRI) technique. Myocardial and liver T(2) (*) values were calculated in 48 thalassemic patients and 21 normal subjects on a 1.5T MRI system using a breath-hold 2D single-slice multiecho gradient-echo (MEGRE) sequence (16 echoes, TR/TE1/TE16/FA = 160/2.7/37.65 ms/25 degrees ). No ECG gating was used. Myocardial T(2) (*), liver T(2) (*), and myocardial to muscle (CR/MS) and liver to muscle (LV/MS) T(2) (*) ratios were correlated with serum ferritin concentration (SFC) levels for all patients. Significant differences in myocardial and liver mean T(2) (*), CR/MS, and LV/MS T(2) (*) values between patients and normal subjects were found (P < 0.0005). Differences in paraspinous muscle mean T(2) (*) values between patients and normal subjects were not significant. Myocardial T(2) (*) and CR/MS T(2) (*) values were not correlated with SFC levels. Liver T(2) (*) and LV/MS T(2) (*) values were significantly correlated with SFC (r = 0.540, P < 0.0005). Myocardial T(2) (*) and CR/MS T(2) (*) values were not correlated with either liver T(2) (*) or LV/MS T(2) (*) values, respectively. We conclude that myocardial and liver iron deposition can be evaluated using the fast non-ECG-gated T(2) (*)qMRI technique.