Double-oblique submillimeter free-breathing coronary MRA allows depiction of extensive parts of the native coronary arteries. The results obtained in patients suggest that the method has the potential to be applied in broader prospective multicenter studies where coronary MRA is compared with X-ray angiography.

No abstract

No abstract

Purpose:To optimize and assess the feasibility of a singleshot black-blood T2-weighted spin-echo echo-planar imaging (SSBB-EPI) sequence for MRI of the liver using sensitivity encoding (SENSE), and compare the results with those obtained with a T2-weighted turbo spin-echo (TSE) sequence. Materials and Methods:Six volunteers and 16 patients were scanned at 1.5T (Philips Intera). In the volunteer study, we optimized the SSBB-EPI sequence by interactively changing the parameters (i.e., the resolution, echo time (TE), diffusion weighting with low b-values, and polarity of the phaseencoding gradient) with regard to distortion, suppression of the blood signal, and sensitivity to motion. The influence of each change was assessed. The optimized SSBB-EPI sequence was applied in patients (N ϭ 16). A number of items, including the overall image quality (on a scale of 1-5), were used for graded evaluation. In addition, the signal-to-noise ratio (SNR) of the liver was calculated. Statistical analysis was carried out with the use of Wilcoxon's signed rank test for comparison of the SSBB-EPI and TSE sequences, with P ϭ 0.05 considered the limit for significance. Results:The SSBB-EPI sequence was improved by the following steps: 1) less frequency points than phase-encoding steps, 2) a b-factor of 20, and 3) a reversed polarity of the phase-encoding gradient. In patients, the mean overall image quality score for the optimized SSBB-EPI (3.5 (range: 1-4)) and TSE (3.6 (range: 3-4)), and the SNR of the liver on SSBB-EPI (mean Ϯ SD ϭ 7.6 Ϯ 4.0) and TSE (8.9 Ϯ 4.6) were not significantly different (P Ͼ .05). Conclusion:Optimized SSBB-EPI with SENSE proved to be feasible in patients, and the overall image quality and SNR of the liver were comparable to those achieved with the standard respiratory-triggered T2-weighted TSE sequence.

With the development of dedicated receiver coils and increased gradient performance, 3.0-T magnetic resonance (MR) systems are gaining wider acceptance in clinical practice. The expected twofold increase in signal-to-noise ratio (SNR) compared with that of 1.5-T MR systems may help improve spatial resolution or increase temporal resolution when used with parallel acquisition techniques. Several issues must be considered when applying 3.0-T MR in the abdomen, including the alteration of the radiofrequency field and relaxation time, increase in energy deposition and susceptibility effects, and problems associated with motion artifacts. For the evaluation of liver lesions, higher SNR and greater resolution achieved with the 3.0-T system could translate into better detection of malignant lesions on T2-weighted images obtained with adjusted imaging parameters. For the evaluation of pancreatic and biliary diseases, high-resolution T2-weighted imaging using single-shot turbo spin-echo sequences is useful; improvement in SNR was noticeable on two-dimensional MR cholangiopancreatographic images. For the preoperative imaging of rectal cancer, a single-shot sequence is useful for dramatically decreasing imaging time while maintaining image quality. Substantial modification of examination protocols, with optimized imaging parameters and sequence designs along with ongoing development of hardware, could contribute to an increased role of the 3.0-T system for abdominal MR examinations.

No abstract

Purpose:To evaluate the feasibility of single breath-hold, multiarterial MRI of the liver using the THRIVE-CENTRAkeyhole technique. Materials and Methods:Twenty-eight patients with 63 focal hepatic lesions underwent liver MR examinations that included the three-dimensional THRIVE-CENTRA-keyhole sequence. Three or six phases were obtained for arterial phase scanning during a single breath-hold. Central kspace data were collected for each phase but the remaining peripheral k-space data were collected only once. The enhancement pattern of each hepatic lesion was analyzed according to the specific diagnosis.Results: Hepatocellular carcinomas (n ϭ 24) enhancement patterns included: rim enhancing (n ϭ 9), homogeneous (n ϭ 7), nodule-in-nodule (n ϭ 5), or heterogeneous (n ϭ 3). A late peritumoral rim was observed in four (17%) of the hepatocellular carcinomas. Most metastases (17 of 18; 94%) demonstrated peripheral rim enhancement. The progressive centripetal enhancement of hemangiomas (n ϭ 6) was clearly depicted. Focal nodular hyperplasia (n ϭ 4) showed early homogeneous enhancement and one lesion demonstrated a central scar. Conclusion:The THRIVE-CENTRA-keyhole technique can be used to acquire single breath-hold, multiarterial images depicting improved enhancement characteristics of focal hepatic lesions. This technique will allow accurate timing of arterial scanning with 3D acquisition and high temporal resolution.

Purpose:To investigate a new image acquisition method that enables an accurate hepatic arterial phase definition and the visualization of contrast agent uptake processes in abdominal organs like liver, spleen, and pancreas. Materials and Methods:A 3D turbo gradient echo method where a fat suppression prepulse is followed by the acquisition of several profiles was combined with an elliptical centric k-space ordering technique and 3D dynamic elliptical centric keyhole. The new k-space ordering method (CENTRAϩ) was validated experimentally. In an initial clinical evaluation phase the method was employed in five patients to assess the accuracy of the hepatic arterial phase definition and the visualization of the contrast uptake processes in dynamic scanning in abdominal organs like liver, spleen, and pancreas. Results:In total, five patients were evaluated using the new k-space order. Our initial results indicate that the new k-space order allows consistent capture of the hepatic arterial phase. In dynamic scanning the extreme short temporal resolution obtained with 3D elliptical centric keyhole enables contrast enhancement to be followed in organs with fast contrast uptake characteristics. Conclusion:The elliptical centric nature of the new image acquisition method effectively allows capture of the contrast enhancement processes with good fat suppression.