Reconstruction of 3D dynamic contrast-enhanced magnetic resonance imaging using nonlocal means

Purpose

To develop and test a nonlocal means‐based reconstruction algorithm for undersampled 3D dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) of tumors.

Materials and Methods

We propose a reconstruction technique that is based on the recently proposed nonlocal means (NLM) filter which can relax trade‐offs in spatial and temporal resolutions in dynamic imaging. Unlike the original application of NLM for image denoising, the MR reconstruction framework here can offer high‐quality images from undersampled k‐space data. The method is based on enforcing similarity constraints in terms of neighborhoods of pixels rather than individual pixels. The method was applied on undersampled 3D DCE imaging of breast and brain tumor datasets and the results were compared to sliding window reconstructions and to a compressed sensing method using total variation constraints on the images.

Results

Undersampling factors of up to five were obtained with the proposed approach while preserving the spatial and temporal characteristics. The NLM reconstruction method offered improved performance over the sliding window and the total variation constrained reconstruction techniques.

Conclusion

The reconstruction framework here can give high‐quality images from undersampled DCE MRI data and has the potential to improve the quality of DCE tumor imaging. J. Magn. Reson. Imaging 2010;32:1217–1227. © 2010 Wiley‐Liss, Inc.     

Utility of Postmortem Autopsy via Whole-Body Imaging: Initial Observations Comparing MDCT and 3.0T MRI Findings with Autopsy Findings

Objective

We prospectively compared whole-body multidetector computed tomography (MDCT) and 3.0T magnetic resonance (MR) images with autopsy findings.

Materials and Methods

Five cadavers were subjected to whole-body, 16-channel MDCT and 3.0T MR imaging within two hours before an autopsy. A radiologist classified the MDCT and 3.0T MRI findings into major and minor findings, which were compared with autopsy findings.

Results

Most of the imaging findings, pertaining to head and neck, heart and vascular, chest, abdomen, spine, and musculoskeletal lesions, corresponded to autopsy findings. The causes of death that were determined on the bases of MDCT and 3.0T MRI findings were consistent with the autopsy findings in four of five cases. CT was useful in diagnosing fatal hemorrhage and pneumothorax, as well as determining the shapes and characteristics of the fractures and the direction of external force. MRI was effective in evaluating and tracing the route of a metallic object, soft tissue lesions, chronicity of hemorrhage, and bone bruises.

Conclusion

A postmortem MDCT combined with MRI is a potentially powerful tool, providing noninvasive and objective measurements for forensic investigations.     

Additional value of gadoxetic acid-DTPA-enhanced hepatobiliary phase MR imaging in the diagnosis of early-stage hepatocellular carcinoma: comparison with dynamic triple-phase multidetector CT imaging

Purpose:

To assess the value of hepatobiliary phase gadoxetic acid (EOB)‐enhanced magnetic resonance imaging (MRI) for the diagnosis of early stage hepatocellular carcinoma (HCC) (<3 cm) compared to triple‐phase dynamic multidetector computed tomography (MDCT).

Materials and Methods:

In all, 52 patients with 60 pathologically proven HCCs underwent both EOB‐enhanced MRI and triple‐phase dynamic MDCT. Two radiologists independently and blindly reviewed three image sets: 1) MDCT, 2) dynamic MRI (unenhanced and EOB‐enhanced dynamic MR images), and 3) combined MRI (dynamic MRI + hepatobiliary phase images) using a five‐point rating scale on a lesion‐by‐lesion basis. Receiver operating characteristics (ROC) analysis was performed, and sensitivity and specificity were calculated.

Results:

The area under the ROC curve (Az) of dynamic MRI was equivalent to that of MDCT for both readers. For both readers, Az and sensitivity of combined MRI for smaller lesions (<1.5 cm) were significantly higher than that of dynamic MRI and MDCT (P < 0.0166). The majority of false‐negative nodules on dynamic MRI or MDCT (75% and 62%, respectively) were due to a lack of identified washout findings.

Conclusion:

Hepatobiliary phase images can increase the value of EOB‐enhanced MRI in the diagnosis of early stage HCC. The sensitivity and accuracy were significantly superior to MDCT for the diagnosis of lesions less than 1.5 cm. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Effect of superparamagnetic iron oxide on tumor‐to‐liver contrast at T2*‐weighted gradient‐echo MRI: Comparison between 3.0T and 1.5T MR systems

Purpose

To compare 3.0T and 1.5T MR systems in terms of the effect of superparamagnetic iron oxide (SPIO) on tumor‐to‐liver contrast in T2*‐weighted gradient‐echo MRI.

Materials and Methods

SPIO‐enhanced gradient‐echo MR images of the liver with four different TEs (3, 5.3, 6.5, and 8.5 msec) were obtained by means of 1.5T and 3.0T systems. Quantitative analyses of relative signal intensities (SIs) and relative tumor contrast and qualitative analyses of image quality and lesion conspicuity of the liver were performed in 22 patients, 16 of whom had malignant liver tumors.

Results

With both 1.5T and 3.0T, at TE = 8.4 msec, the relative SI of liver and relative tumor contrast were significantly (P < 0.01) lower and higher, respectively, than that for any of the other TEs. There were no significant differences in the relative SI of the liver, relative tumor contrast, image quality, and tumor conspicuity for the same TE between the 1.5T and 3.0T systems.

Conclusion

Our results showed that the effect of SPIO on tumor‐to‐liver contrast at T2*‐weighted gradient‐echo imaging was similar for the 1.5T and 3.0T systems, and that the 8.4‐msec TE was optimal of the four TEs used in this study at 3.0T. J. Magn. Reson. Imaging 2009;29:595–600. © 2009 Wiley‐Liss, Inc.     

Pancreatic adenocarcinoma: MDCT versus MRI in the detection and assessment of locoregional extension

PURPOSE: To compare dynamic-contrast enhanced multirow detector computed tomography (MDCT) including multiplanar reformatted images (MPR) and magnetic resonance imaging (MRI) including magnetic resonance cholangiopancreatography images for the detection and assessment of locoregional extension of pancreatic adenocarcinoma. MATERIALS AND METHODS: Twenty-four patients with and 21 patients without pancreatic adenocarcinoma underwent triple-phase MDCT and MRI. Three radiologists independently attempted to detect pancreatic adenocarcinoma and assess locoregional extension in 3 sessions. First session involved MDCT images. In the second session, radiologists had access to coronal and sagittal MPR images together with the axial images (MDCT + MPR). Third session involved MR images. Results were compared with surgical findings using receiver operating characteristic analysis and kappa statistics. RESULTS: Regarding tumor detection, MDCT + MPR had a significantly higher value for areas under the curve (0.96 +/- 0.02) at receiver operating characteristic analysis compared with those of MRI (0.90 +/- 0.03) and MDCT (0.85 +/- 0.04). MDCT + MPR had the highest mean sensitivity (96%), and MRI had the highest mean specificity (98%). For locoregional extension, MDCT + MPR showed the highest kappa values of the study for all factors evaluated (range, 0.63-0.86). CONCLUSIONS: In conclusion, multiphasic MDCT imaging with MPR images was superior to multiphasic MDCT imaging without MPR images and to comprehensive MRI employing 2-D sequences and magnetic resonance cholangiopancreatography for both the detection and assessment of locoregional extension of pancreatic adenocarcinomas. MRI might be used for further lesion characterization regarding its high specificity.     

Preoperative assessment of longitudinal extent of bile duct cancers using MDCT with multiplanar reconstruction and minimum intensity projections: comparison with MR cholangiography

Objective

To compare the performance of MDCT, including multiplanar reformation (MPR) and minimum intensity projection (MinIP) images, with that of transaxial MDCT with MR cholangiography (MRC) in the preoperative evaluation of the longitudinal extent of bile duct cancer.

Methods

Twenty-seven patients with surgically proven bile duct cancer, who had undergone preoperative multiphasic MDCT and MRC, were included. Two radiologists evaluated the MDCT set with MPR and MinIP images and the image set of transaxial MDCT with MRC, regarding the longitudinal extent of bile duct cancer. The results were compared with the surgical and pathology findings.

Results

The area under the receiver operating characteristic curves of the MDCT set with MPR and MinIP images and the image set of transaxial MDCT with MRC for predicting the longitudinal extent of bile duct cancer, were 0.938, 0.923 and 0.839, 0.836 for both reviewers. The differences were not statistically significant for either image set or either reviewer. The sensitivity and specificity of the MDCT image set for detecting tumor involvement of the biliary second confluences or intrapancreatic segment were similar for both reviewers to those of transaxial MDCT with MRC.

Conclusions

MDCT with MPR and MinIP images showed comparable diagnostic performance to that of transaxial MDCT with MRC for predicting the longitudinal extent of bile duct cancer.     

Gadoxetic acid-enhanced MRI findings of early hepatocellular carcinoma as defined by new histologic criteria

Purpose:

To describe the imaging features of early hepatocellular carcinoma (HCC) on gadoxetic acid‐enhanced MRI (Gd‐EOB‐MRI) in comparison with multidetector computed tomography (MDCT) examinations.

Materials and Methods:

We analyzed imaging findings of 19 pathologically proven early HCC lesions in 15 patients who underwent both MDCT and Gd‐EOB‐MRI at 3.0 Tesla (T) units before surgery. MRI included in‐phase and out‐of‐phase T1‐weighted dual‐echo gradient‐recalled‐echo sequences, dynamic T1‐weighted images before and after bolus injection of gadoxetic acid disodium, fat‐saturated T2‐weighted fast spin‐echo sequences, and T1‐weighted hepatobiliary phase images 20 min after contrast injection. Two radiologists retrospectively evaluated the signal intensities and enhancement features on MRI and MDCT.

Results:

None of the lesions displayed arterial enhancement and washout on MDCT. On Gd‐EOB‐MRI, six (32%) lesions showed T2‐hyperintensity, five (26%) lesions showed signal drop on opposed‐phase. Three lesions (16%) showed arterial enhancement and washout. Twelve (63%), 13 (68%), and 15 (79%) lesions were hypointense on hepatic venous, equilibrium, and hepatobiliary phase, respectively.

Conclusion:

Most early HCCs did not show arterial enhancement and washout pattern on both MDCT and Gd‐EOB‐MRI. Gd‐EOB‐MRI may provide several ancillary findings for diagnosis of early HCC such as decreased hepatobiliary uptake, T2 hyperintensity and signal drop in opposed phase. J. Magn. Reson. Imaging 2012;393‐398. © 2011 Wiley Periodicals, Inc.     

Image quality of multiplanar reconstruction of pulmonary CT scans using adaptive statistical iterative reconstruction

Objective

We investigated the image quality of multiplanar reconstruction (MPR) using adaptive statistical iterative reconstruction (ASIR).

Methods

Inflated and fixed lungs were scanned with a garnet detector CT in high-resolution mode (HR mode) or non-high-resolution (HR) mode, and MPR images were then reconstructed. Observers compared 15 MPR images of ASIR (40%) and ASIR (80%) with those of ASIR (0%), and assessed image quality using a visual five-point scale (1, definitely inferior; 5, definitely superior), with particular emphasis on normal pulmonary structures, artefacts, noise and overall image quality.

Results

The mean overall image quality scores in HR mode were 3.67 with ASIR (40%) and 4.97 with ASIR (80%). Those in non-HR mode were 3.27 with ASIR (40%) and 3.90 with ASIR (80%). The mean artefact scores in HR mode were 3.13 with ASIR (40%) and 3.63 with ASIR (80%), but those in non-HR mode were 2.87 with ASIR (40%) and 2.53 with ASIR (80%). The mean scores of the other parameters were greater than 3, whereas those in HR mode were higher than those in non-HR mode. There were significant differences between ASIR (40%) and ASIR (80%) in overall image quality (p<0.01). Contrast medium in the injection syringe was scanned to analyse image quality; ASIR did not suppress the severe artefacts of contrast medium.

Conclusion

In general, MPR image quality with ASIR (80%) was superior to that with ASIR (40%). However, there was an increased incidence of artefacts by ASIR when CT images were obtained in non-HR mode.Multiplanar reconstruction (MPR) of CT images plays an important role in the interpretation of the three-dimensional anatomical location or extent of disease, and is an essential technique in daily clinical practice. Multidetector row CT (MDCT) is widely used, and advances in MDCT technology have facilitated better images with thinner slice thickness and extended coverage, which has allowed more MPR images to be evaluated in greater detail. Coronal MPR images produced by MDCT supply good image quality for lung assessment and show similar image quality to axial high-resolution (HR) CT images [1^,2].To further enhance CT image quality, improvements in temporal resolution and/or spatial resolution are needed. MDCT equipped with more rapid gantry rotation or more detector arrays has already evolved for the improvement of temporal resolution. GE Healthcare (Milwaukee, WI) recently produced an MDCT unit containing a new detector composed of garnet, which has a faster response than the previous detector material. This apparatus can provide improved spatial resolution by acquiring more data.Reconstruction algorithms are also important for improved image quality. Although the filtered back-projection algorithm has traditionally been used for image reconstruction, new reconstruction algorithms are being developed. The iterative reconstruction algorithm has already been used for image reconstruction of positron emission tomography (PET) or single photon emission CT (SPECT), resulting in improved image quality [3-6]. Iterative reconstruction was also used in early CT systems and is currently used by many manufacturers of clinical CT systems. Adaptive statistical iterative reconstruction (ASIR), recently developed for CT by GE Healthcare, is expected to improve low-contrast detectability by reducing noise when using the same radiation dose as would be used with filtered back-projection. It is also expected to reduce the radiation dose for a similar noise level compared with filtered back-projection. Until now, the quality of CT images from multiplanar reconstruction using ASIR had not been analysed. The purpose of this study was to evaluate the image quality of MPR using ASIR.     

Gadoxetic acid‐enhanced MRI versus multiphase multidetector row computed tomography for evaluating the viable tumor of hepatocellular carcinomas treated with image‐guided tumor therapy

Purpose:

To compare the diagnostic performance of gadoxetic acid‐enhanced MRI with that of multi‐phase 40‐ or 64‐multidetector row computed tomography (MDCT) to evaluate viable tumors of hepatocellular carcinomas (HCCs) treated with image‐guided tumor therapy.

Materials and Methods:

A total of 108 patients with 162 HCCs (56 lesions with viable tumor and 106 without viable tumor) treated by means of transcatheter arterial chemoembolization or radiofrequency ablation were retrospectively included in this study. All patients underwent multi‐phase CT at 40‐ or 64‐MDCT and gadoxetic acid‐enhanced MRI using 3.0 Tesla (T). Two observers independently and randomly reviewed the CT and MR images of the treated lesions. The diagnostic performance of two techniques for the evaluation of the viable tumors in the treated lesions was assessed with a receiver operating characteristic (ROC) analysis.

Results:

For each observer, the areas under the ROC curve were 0.953 and 0.969 for MRI, and 0.870 and 0.888 for MDCT (P < 0.05). The diagnostic accuracies (96.3% for each observer) and sensitivities (92.9% and 96.4%) of MRI in two observers were significantly higher than those (82.7% and 80.9%, 53.6% for each observer, respectively) of MDCT (P < 0.001). The negative predictive values (96.3% and 98.1%) of MRI in two observers were significantly higher than those (80.0% and 79.5%) of MDCT (P < 0.001). For each observer, specificities and positive predictive values did not differ significantly between the two techniques (P > 0.05).

Conclusion:

Gadoxetic acid‐enhanced MRI shows better diagnostic performance than that of MDCT for evaluating the viable tumors of HCCs treated with image‐guided tumor therapy. J. Magn. Reson. Imaging 2010;32:629–638. © 2010 Wiley‐Liss, Inc.     

Detection of hepatic metastases by superparamagnetic iron oxide-enhanced MR imaging: prospective comparison between 1.5-T and 3.0-T images in the same patients

Objective:

To prospectively compare the diagnostic performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging at 3.0 T and 1.5 T for detection of hepatic metastases.

Methods:

A total of 28 patients (18 men, 10 women; mean age, 61 years) with 80 hepatic metastases were prospectively examined by SPIO-enhanced MR imaging at 3.0 T and 1.5 T. T1-weighted gradient-recalled-echo (GRE) images, T2*-weighted GRE images and T2-weighted fast spin-echo (SE) images were acquired. The tumour-to-liver contrast-to-noise ratio (CNR) of the lesions was calculated. Three observers independently reviewed each image. Image artefacts and overall image quality were analysed, sensitivity and positive predictive value for the detection of hepatic metastases were calculated, and diagnostic accuracy using the receiver-operating characteristics (ROC) method was evaluated.

Results:

The tumour-to-liver CNRs were significantly higher at 3.0 T. Chemical shift and motion artefact were more severe, and overall image quality was worse on T2-weighted fast SE images at 3.0 T. Overall image quality of the two systems was similar on T1-weighted GRE images and T2*-weighted GRE images. Sensitivity and area under the ROC curve for the 3.0-T image sets were significantly higher.

Conclusion:

SPIO-enhanced MR imaging at 3.0 T provided better diagnostic performance for detection of hepatic metastases than 1.5 T.     

多层螺旋CT重建技术在胆道梗阻中的应用价 值

目的:探讨多层螺旋CT重建技术在胆道梗阻中的应用价值.材料和方法:收集47例临床证实的胆道梗阻患者的多层螺旋CT扫描数据并行胆道多平面重建(MPR)与曲面重建(CPR),将50例无胆系疾患又无胆道扩张的CT扫描数据作为对照,分别将两组间的MPR与CPR图像对胆道结构和胆管壁的显示效果以及对胆管系统的显示能力进行对比分析,再对47例胆道梗阻患者的CT胆道重建图像进行回顾性分析进一步评估其对梗阻部位和梗阻原因判断的准确性.结果:胆道梗阻组中MPR和CPR图像对胆道结构及胆管壁的显示效果优于非梗阻组,CPR图像对胆管系统的显示能力优于非梗阻组.多层螺旋CT胆道重建图像对梗阻原因判断的准确性为89.4%(42/47),对梗阻部位判断的准确性为100%.结论:多层螺旋CT胆道重建图像能够清楚地显示梗阻扩张的胆道结构、胆管壁情况和梗阻的部位,并能对大多数胆道梗阻的原因做出判断,在胆道梗阻性疾病的诊断中具有较好的应用和推广价值.     

CT-MR image data fusion for computer-assisted navigated surgery of orbital tumors

Purpose

To demonstrate the value of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative assessment of orbital tumors, and to present, particularly, CT and MR image data fusion for surgical planning and performance in computer-assisted navigated surgery of orbital tumors.

Materials and methods

In this retrospective case series, 10 patients with orbital tumors and associated complaints underwent MDCT and MRI of the orbit. MDCT was performed at high resolution, with a bone window level setting in the axial plane. MRI was performed with an axial 3D T1-weighted (w) gradient-echo (GE) contrast-enhanced sequence, in addition to a standard MRI protocol. First, MDCT and MR images were used to diagnose tumorous lesions compared to histology as a standard of reference. Then, the image data sets from CT and 3D T1-w GE sequences were merged on a workstation to create CT-MR fusion images that were used for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient. Furthermore, the clinical preoperative status was compared to the patients’ postoperative outcome.

Results

Radiological and histological diagnosis, which revealed 7 benign and 3 malignant tumors, were concordant in 7 of 10 cases (70%). The CT-MR fusion images supported the surgeon in the preoperative planning and improved the surgical performance. The mean intraoperative accuracy of the navigation unit was 1.35 mm. Postoperatively, orbital complaints showed complete regression in 6 cases, were ameliorated notably in 3 cases, and remained unchanged in 1 case.

Conclusion

CT and MRI are essential for the preoperative assessment of orbital tumors. CT-MR image data fusion is an accurate tool for planning the correct surgical procedure, and can improve surgical results in computer-assisted navigated surgery of orbital tumors.     

Advances of 3T MR imaging in visualizing trabecular bone structure of the calcaneus are partially SNR‐independent: Analysis using simulated noise in relation to micro‐CT, 1.5T MRI,and biomechanical strength

Purpose

To investigate differences in magnetic resonance imaging (MRI) of trabecular bone at 1.5T and 3.0T and to specifically study noise effects on the visualization and quantification of trabecular architecture using conventional histomorphometric and nonlinear measures of bone structure.

Materials and Methods

Sagittal MR images of 43 calcaneus specimens (donor age: 81 ± 10 years) were acquired at 1.5T and 3.0T using gradient echo sequences. Noise was added to obtain six sets of images with decreasing signal‐to‐noise ratios (SNRs). Micro‐CT images were obtained from biopsies taken from 37 calcaneus samples and bone strength was determined. Morphometric and nonlinear structure parameters were calculated in all datasets.

Results

Originally, SNR was 1.5 times higher at 3.0T. In the simulated image sets, SNR was similar at both fields. Trabecular dimensions measured by μCT were adequately estimated by MRI, with residual errors (e_r), ranging from 16% to 2.7% at 3.0T. Comparing e_r at similar SNR, 3.0T consistently displayed lower errors than 1.5T (eg, bone fraction at SNR ≈4: e_r[3.0T] = 15%; e_r[1.5T] = 21%, P < 0.05).

Conclusion

The advances of 3.0T compared to 1.5T in visualizing trabecular bone structure are partially SNR‐independent. The better performance at 3.0T may be explained by pronounced susceptibility, enhancing the visualization of thin trabecular structures. J. Magn. Reson. Imaging 2009;29:132–140. © 2008 Wiley‐Liss, Inc.     

Diagnostic value of multidetector row CT in rectal cancer staging: comparison of multiplanar and axial images with histopathology

AIM: Although magnetic resonance (MR) imaging is widely used for rectal cancer staging, many centres in the UK perform computed tomography (CT) for staging rectal cancer at present. Furthermore in a small proportion of cases contraindications to MR imaging may lead to staging using CT. The purpose of this study was to evaluate the accuracy of current generation multidetector row CT (MDCT) in local staging of rectal cancer. In particular the accuracy of multiplanar (MPR) versus axial images in the staging of rectal cancer was assessed. MATERIAL AND METHODS: Sixty-nine consecutive patients were identified who had undergone staging of rectal cancer on CT. The imaging data were reviewed as axial images and then as MPR images (coronal and sagittal) perpendicular and parallel to the tumour axis. CT staging on axial and MPR images was then compared to histopathological staging. RESULTS: MPR images detected more T4 and T3 stage tumours than axial images alone. The overall accuracy of T-staging on MPR images was 87.1% versus 73.0% for axial images alone. The overall accuracy of N staging on MPR versus axial images was 84.8% versus 70.7%. There was a statistically significant difference in the staging of T3 tumours between MPR and axial images (p<0.001). CONCLUSION: Multidetector row CT has high accuracy for local staging of rectal cancer. Addition of MPR images to standard axial images provides higher accuracy rates for T and N staging of rectal cancer than axial images alone.     

Iterative decomposition of water and fat with echo asymmetry and least‐squares estimation (IDEAL) of the wrist and finger at 3T: Comparison with chemical shift selective fat suppression images

Purpose:

To compare fat‐suppressed magnetic resonance imaging (MRI) quality using iterative decomposition of water and fat with echo asymmetry and least‐squares estimation (IDEAL) with that using chemical shift selective fat‐suppressed T1‐weighted spin‐echo (CHESS) images for evaluating rheumatoid arthritis (RA) lesions of the hand and finger at 3T.

Materials and Methods:

MRI was performed in eight healthy volunteers and eight RA patients with a 3.0T MR system (Signa HDxt GE healthcare) using an eight‐channel knee coil. FS‐CHESS‐T1‐SE and IDEAL imaging were acquired in the coronal planes covering the entire structure of the bilateral hands with a slice thickness of 2 mm. In the RA patients both images were obtained after intravenous gadolinium administration. Image quality was evaluated on a five‐point scale (1 = excellent to 5 = very poor). Synovitis and bone marrow contrast uptake on MR images were reviewed by two musculoskeletal radiologists using the Rheumatoid Arthritis MRI Scoring System (RAMRIS) of the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) group.

Results:

IDEAL showed uniform FS unaffected by magnetic field inhomogeneity and challenging geometry of hand and fingers, while CHESS‐T1‐SE often showed FS failure within the first metacarpal joint, tip of the finger, and ulnar aspect of the wrist joint. Overall image quality was significantly better with IDEAL than CHESS‐T1‐SE images (4.43 vs. 3.43, P < 0.01). Interobserver agreement (κ value) for synovitis and bone marrow contrast uptake was good to excellent with IDEAL (0.74–0.91, 0.62–0.89, respectively).

Conclusion:

IDEAL could compensate for the effects of field inhomogeneities, providing uniform FS of the hand and finger than did the CHESS‐T1‐SE sequence. J. Magn. Reson. Imaging 2013;37:733–738. © 2012 Wiley Periodicals, Inc.     

Quantitative and qualitative comparison of 3.0T and 1.5T MR imaging of the liver in patients with diffuse parenchymal liver disease

Purpose

The purpose of our study was to compare signal characteristics and image qualities of MR imaging at 3.0 T and 1.5 T in patients with diffuse parenchymal liver disease.

Materials and methods

25 consecutive patients with diffuse parenchymal liver disease underwent abdominal MR imaging at both 3.0 T and 1.5 T within a 6-month interval. A retrospective study was conducted to obtain quantitative and qualitative data from both 3.0 T and 1.5 T MRI. Quantitative image analysis was performed by measuring the signal-to-noise ratios (SNRs) and the contrast-to-noise ratios (CNRs) by the Students t-test. Qualitative image analysis was assessed by grading each sequence on a 3- and 4-point scale, regarding the presence of artifacts and image quality, respectively. Statistical analysis consisted of the Wilcoxon signed-rank test.

Results

the mean SNRs and CNRs of the liver parenchyma and the portal vein were significantly higher at 3.0 T than at 1.5 T on portal and equilibrium phases of volumetric interpolated breath-hold examination (VIBE) images (P < 0.05). The mean SNRs were significantly higher at 3.0 T than at 1.5 T on T1-weighted spoiled gradient echo (SGE) images (P < 0.05). However, there were no significantly differences on T2-weighted short-inversion-time inversion recovery (STIR) images. Overall image qualities of the 1.5 T non-contrast T1- and T2-weighted sequences were significantly better than 3.0 T (P < 0.01). In contrast, overall image quality of the 3.0 T post-gadolinium VIBE sequence was significantly better than 1.5 T (P < 0.01).

Conclusions

MR imaging of post-gadolinium VIBE sequence at 3.0 T has quantitative and qualitative advantages of evaluating for diffuse parenchymal liver disease.     

Potential contribution of multiplanar reconstruction (MPR) to computer-aided detection of lung nodules on MDCT

Purpose

To evaluate potential benefits of using multiplanar reconstruction (MPR) in computer-aided detection (CAD) of lung nodules on multidetector computed tomography (MDCT).

Materials and methods

MDCT datasets of 60 patients with suspected lung nodules were retrospectively collected. Using “second-read” CAD, two radiologists (Readers 1 and 2) independently interpreted these datasets for the detection of non-calcified nodules (≥4 mm) with concomitant confidence rating. They did this task twice, first without MPR (using only axial images), and then 4 weeks later with MPR (using also coronal and sagittal MPR images), where the total reading time per dataset, including the time taken to assess the detection results of CAD software (CAD assessment time), was recorded. The total reading time and CAD assessment time without MPR and those with MPR were statistically compared for each reader. The radiologists’ performance for detecting nodules without MPR and the performance with MPR were compared using jackknife free-response receiver operating characteristic (JAFROC) analysis.

Results

Compared to the CAD assessment time without MPR (mean, 69 s and 57 s for Readers 1 and 2), the CAD assessment time with MPR (mean, 46 s and 45 s for Readers 1 and 2) was significantly reduced (P < 0.001). For Reader 1, the total reading time was also significantly shorter in the case with MPR. There was no significant difference between the detection performances without MPR and with MPR.

Conclusion

The use of MPR has the potential to improve the workflow in CAD of lung nodules on MDCT.     

3.0 T MRI THRIVE技术在颈部疾病中增强效果的评判

目的探讨3.0 T MRI T1高分辨率各向同性容积采集(T1 high resolution isotropic volume excitation,THRIVE)技术在颈部疾病检查中增强效果的评判。资料与方法使用Philips Achieva 3.0 T MR成像仪16通道头颈联合线圈对36例临床怀疑有颈部疾病的患者进行常规横断位、冠状位及矢状位SE T1WI抑脂序列增强扫描,随后进行THRIVE抑脂序列增强扫描并对其进行多平面重组(MPR),并对两种方法增强效果进行分析和评价。结果所有患者均成功完成SE T1WI抑脂和THRIVE抑脂增强序列扫描检查。SE T1WI和THRIVE序列两组增强图像的抑脂效果有统计学意义(Z=18.722,P<0.001)。对运动伪影的控制情况THRIVE序列比传统SE T1WI序列好(Z=4.758,P=0.029)。结论 THRIVE抑脂增强序列成像时间短,抑脂效果好,能较好地显示颈部结构及病变,从而更能满足临床诊断需求。     

Fast dixon‐based multisequence and multiplanar MRI for whole‐body detection of cancer metastases

Purpose

To develop and demonstrate the feasibility of multisequence and multiplanar MRI for whole‐body cancer detection.

Materials and Methods

Two fast Dixon‐based sequences and a diffusion‐weighted sequence were used on a commercially available 1.5 T scanner for whole‐body cancer detection. The study enrolled 19 breast cancer patients with known metastases and in multistations acquired whole‐body axial diffusion‐weighted, coronal T2‐weighted, axial/sagittal pre‐ and postcontrast T1‐weighted, as well as triphasic abdomen images. Three radiologists subjectively scored Dixon images of each series for overall image quality and fat suppression uniformity on a 4‐point scale (1 = poor, 2 = fair, 3 = good, and 4 = excellent).

Results

Eighteen of the 19 patients completed the whole‐body MRI successfully. The mean acquisition time and overall patient table time were 46 ± 3 and 69 ± 5 minutes, respectively. The average radiologists' scores for overall image quality and fat suppression uniformity were both 3.4 ± 0.5. The image quality was consistent between patients and all completed whole‐body examinations were diagnostically adequate.

Conclusion

Whole‐body MRI offering essentially all the most optimal tumor‐imaging sequences in a typical 1‐hour time slot can potentially become an appealing “one‐stop‐shop” for whole‐body cancer imaging. J. Magn. Reson. Imaging 2009;29:1154–1162. © 2009 Wiley‐Liss, Inc.     

Preoperative evaluation of pancreatic cancer: Comparison of gadolinium‐enhanced dynamic MRI with MR cholangiopancreatography versus MDCT

Purpose

To determine the accuracy of magnetic resonance imaging (MRI) including dynamic imaging using three‐dimensional gradient‐echo (3D‐GRE) sequences and MR cholangiopancreatograpy (MRCP) compared with that of multidetector row CT (MDCT) with regard to resectability in pancreas cancer.

Materials and Methods

From February 2004 to July 2008, 54 patients (32 men, 22 women: age range, 28–83 years; mean age, 63.1 years old) with surgically proven pancreatic carcinoma, who had undergone preoperative gadolinium‐enhanced 3D‐GRE MRI with MRCP and triple‐phase MDCT, were included in this retrospective study. Two, clinically experienced attending radiologists independently reviewed the two image sets. These readers evaluated the tumor conspicuity, presence of vascular invasion, choledochal and duodenal invasion, lymph node metastases, distant metastasis, and tumor resectability. The results were compared with the surgical and histopathologic findings using receiver operating characteristic analysis (Az) and kappa statistics.

Results

Curative resections were performed on 42 patients. Regarding the tumor conspicuity, MRI had a significantly higher Az value compared with MDCT according to both reviewers (P < 0.05). The accuracy of resectability was Az = 0.753 and 0.768 on MRI and Az = 0.829 and 0.762 on MDCT for each reviewer, and the difference in the accuracy of resectability was not significant between MRI and MDCT for either reviewer (P > 0.05). Two imaging sets showed a similar diagnostic performance in the evaluation of vascular involvement, lymph node metastasis, and distant metastasis.

Conclusion

Dynamic 3D‐GRE MRI with MRCP shows superior tumor conspicuity and similar diagnostic performance compared with MDCT in evaluating the resectability of pancreatic cancer. J. Magn. Reson. Imaging 2009;30:586–595. © 2009 Wiley‐Liss, Inc.