Recent developments in magnetic resonance (MR) imaging of the heart have refocused attention on the potential of MR and continue to attract intense interest within the radiology and cardiology ...communities. Improvements in speed, image quality, reliability, and range of applications have evolved to the point where cardiac MR imaging is increasingly seen as a practical clinical tool. As is often the case with MR imaging, not all of the most powerful techniques are necessarily easy to master or understand, and many-nonspecialists and specialists alike-are challenged to stay abreast. This review covers some of the major milestones that have led to the current state of cardiac MR and attempts to put into context some concepts that, although technical, have a real impact on the diagnostic power of cardiac MR imaging. Topics discussed include functional imaging, myocardial viability and perfusion imaging, flow quantification, and coronary artery imaging. A review such as this can only scratch the surface of what is a dynamic interdisciplinary field, but the hope is that sufficient information and insight are provided to stimulate the motivated reader to take his or her interest to the next level.
Background
Few studies directed at assessing the visualization of the walls of unruptured aneurysms have used higher‐resolution 3D MRI vessel wall imaging. Prospective longitudinal studies are also ...needed to screen vessel wall changes in unruptured aneurysms.
Purpose
To compare the aneurysm wall visualization on pre‐ and post‐3D isotropic T1‐weighted Sampling Perfection with Application‐optimized Contrasts by using different flip angle Evolutions (SPACE) images and to explore whether there is a change in wall enhancement at follow up.
Study Type
Prospective.
Population
Twenty‐nine patients with a total of 35 unruptured intracranial aneurysms.
Sequence
3D T1‐weighted pre‐ and postcontrast SPACE (0.5 mm isotropic) at 3.0T.
Assessment
The aneurysm wall visibility (0–5 scale) between pre‐ and postcontrast images as well as the wall enhancement (0–5 scale) between follow‐up and baseline studies (6–30 months, average 12.7 months) were compared. Differences in wall visibility and enhancement were also investigated as a function of aneurysm diameter and location.
Statistical Test
The Wilcoxon signed rank paired test was used to compare the wall visibility score between pre‐ and postcontrast SPACE images, as well as wall enhancement between follow‐up and baseline. The Mann–Whitney and Kruskal–Wallis tests were used to investigate the enhancement difference between different diameters and locations.
Results
Postcontrast images had significantly higher wall visibility (P = 0.01). A wall enhancement score ≥2 was found in 71% of the aneurysms. Changes in levels of wall enhancement were found in 17% of the aneurysms at follow‐up studies, but those changes were small. Wall visibility and enhancement scores of large aneurysms were significantly higher than small ones (P < 0.001).
Data Conclusion
3D T1‐weighted higher resolution SPACE can be used to assess changes in enhancement at follow‐up studies. Contrast SPACE image provides better aneurysm wall visibility and improves visualization of the aneurysm wall.
Level of Evidence: 2
Technical Efficacy: Stage 3
J. Magn. Reson. Imaging 2019;50:193–200.
Self-gated cardiac cine MRI Larson, Andrew C.; White, Richard D.; Laub, Gerhard ...
Magnetic resonance in medicine,
January 2004, Letnik:
51, Številka:
1
Journal Article
Abstract Introduction The aortic wall and intraluminal thrombus (ILT) have been increasingly studied as potential markers of progressive disease with abdominal aortic aneurysms (AAAs). Our goal was ...to develop a high resolution, 3D black blood MR technique for AAA wall and ILT imaging within a clinically acceptable scan time. Methods Twenty two patients with AAAs (maximal diameter 4.3 ± 1.0 cm), along with five healthy volunteers, were imaged at 3 T with a 3D T1 -weighted fast-spin-echo sequence using variable flip angle trains (SPACE) with a preparation pulse (DANTE) for suppressing blood signal. Volunteers and ten patients were also scanned with SPACE alone for comparison purposes. The signal to noise ratio (SNR) and the aortic wall/ILT to lumen contrast to noise ratio (CNR) were measured. Qualitative image scores (1–4 scale) assessing the inner lumen and outer wall boundaries of AAA were performed by two blinded reviewers. In patients with ILT, the ratio of ILT signal intensity (ILTSI ) over psoas muscle SI (MuscleSI ) was calculated, and the signal heterogeneity of ILT was quantified as standard deviation (SD) over the mean. Results All subjects were imaged successfully with an average scan time of 7.8 ± 0.7 minutes. The DANTE preparation pulse for blood suppression substantially reduced flow artifacts in SPACE with lower lumen SNR (8.8 vs. 21.4, p < 0.001) and improved the wall/ILT to lumen CNR (9.9 vs. 6.3, p < 0.001) in patients. Qualitative assessment showed improved visualization of lumen boundaries (73% higher scores on average, p = 0.01) and comparable visualization of outer wall boundary (p > 0.05). ILT was present in ten patients, with relatively high signal and a wide SD (average ILTSI /MuscleSI 1.42 ± 0.48 (range 0.75–2.11)) and with SD/mean of 27.7% ± 6.6% (range 19.6%–39.4%). Conclusion High resolution, 3D black blood MRI of AAAs can be achieved in a clinical accepted scan time with reduction of flow artifacts using the DANTE preparation pulse. Signal characteristics of ILT can be quantified and may be used for improved patient-specific risk stratification.
Abstract Three dimensional bilateral imaging is the standard for most clinical breast dynamic contrast-enhanced (DCE) MRI protocols. Because of high spatial resolution (sRes) requirement, the typical ...1–2 min temporal resolution (tRes) afforded by a conventional full-k-space-sampling gradient echo (GRE) sequence precludes meaningful and accurate pharmacokinetic analysis of DCE time-course data. The commercially available, GRE-based, k-space undersampling and data sharing TWIST (time-resolved angiography with stochastic trajectories) sequence was used in this study to perform DCE-MRI exams on thirty one patients (with 36 suspicious breast lesions) before their biopsies. The TWIST DCE-MRI was immediately followed by a single-frame conventional GRE acquisition. Blinded from each other, three radiologist readers assessed agreements in multiple lesion morphology categories between the last set of TWIST DCE images and the conventional GRE images. Fleiss’ κ test was used to evaluate inter-reader agreement. The TWIST DCE time-course data were subjected to quantitative pharmacokinetic analyses. With a four-channel phased-array breast coil, the TWIST sequence produced DCE images with 20 s or less tRes and ~ 1.0×1.0×1.4 mm3 sRes. There were no significant differences in signal-to-noise ( P =.45) and contrast-to-noise ( P =.51) ratios between the TWIST and conventional GRE images. The agreements in morphology evaluations between the two image sets were excellent with the intra-reader agreement ranging from 79% for mass margin to 100% for mammographic density and the inter-reader κ value ranging from 0.54 ( P <.0001) for lesion size to 1.00 ( P <.0001) for background parenchymal enhancement. Quantitative analyses of the DCE time-course data provided higher breast cancer diagnostic accuracy (91% specificity at 100% sensitivity) than the current clinical practice of morphology and qualitative kinetics assessments. The TWIST sequence may be used in clinical settings to acquire high spatiotemporal resolution breast DCE-MRI images for both precise lesion morphology characterization and accurate pharmacokinetic analysis.
The purpose of the study was to implement a three-dimensional (3D) magnetic resonance (MR) angiographic technique with acquisition times on the order of 800 msec with use of a spoiled gradient-echo ...pulse sequence (repetition time, 1.60 msec; echo time, 0.65 msec) and bolus intravenous injection of contrast material doses as small as 6 mL. High-spatial-resolution conventional MR angiography performed with 30 mL of gadopentetate dimeglumine was the reference standard. As implemented, subsecond 3D MR angiography allowed temporal sampling that was rapid enough to depict short-lived processes, as illustrated in patients with shunts and dissections. With small contrast material doses and subsecond frame rates, it is also possible to measure pulmonary arteriovenous circulation times with this 3D MR angiographic technique.
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