Magnetic resonance imaging of the spine at 3 Tesla.

Magnetic resonance imaging (MRI) has developed dramatically in the 25 years since its clinical introduction. Advances in hardware design have included the development of high field magnets and more sophisticated and sensitive coils. Improvements in sequences, data sampling, and postprocessing software have benefited the attainable spatial and temporal resolution to the point at which the fine depiction of anatomical structure and pathological processes is now routine. As in other radiological areas, the most recent advances in MRI have proven highly valuable in the field of musculoskeletal radiology where the lack of radiation, high soft tissue contrast, and capacity for multiplanar or three-dimensional imaging have made MRI the imaging modality of choice. Particular benefits are seen in diagnostic imaging of the spine where MRI is clearly superior to both conventional radiography and computed tomography. In this article, we discuss the impact of the most recent technological advance in MRI, namely the advent of 3 Tesla (3-T) imaging, on diagnostic imaging of the spine. Comparisons are drawn with imaging at 1.5 T, and emphasis is placed on MR physics and on the benefits and principal difficulties associated with spine imaging at high field strength.

MR angiography of the renal arteries: intraindividual comparison of double-dose contrast enhancement at 1.5 T with standard dose at 3 T.

OBJECTIVE: The purpose of this study was to compare prospectively and within subjects use of 0.1 mmol/kg of gadodiamide at 3 T with use of 0.2 mmol/kg of gadodiamide at 1.5 T for MR angiography of the renal arteries. SUBJECTS AND METHODS: Twenty-two patients (14 men, eight women; mean age, 66.5 years) underwent two MR angiographic examinations of the renal arteries separated by at least 24 hours on whole-body 1.5- and 3-T MRI systems with a phase-encoded 3D spoiled breath-hold pulse sequence. Two radiologists blinded to the dose of contrast material assessed all image data in consensus for renal arterial disease and for image quality on a five-point Likert-type scale. Quantitative evaluation (vessel signal-to-noise ratio and vessel-muscle contrast-to-noise ratio) was performed by a third radiologist. RESULTS: Five renal arterial stenoses were detected with both techniques. The difference in mean image quality for the two doses and field strengths was not statistically significant. Overall vessel length and intraparenchymal branches, however, were better visualized with the double dose at 1.5 T. Signal-to-noise and contrast-to-noise ratios were significantly higher (both, p < 0.05) with the double dose at 1.5 T (125.7 and 64.2, respectively) compared with the standard dose at 3 T (112.3 and 59.7). CONCLUSION: MR angiography can be performed with high diagnostic image quality at 3 T with 0.1 mmol/kg of gadodiamide. Signal-to-noise and contrast-to-noise ratios are higher with a double dose at 1.5 T.

Contrast-enhanced magnetic resonance angiography: P792 blood pool agent versus Gd-DOTA in rabbits at 3.0 T versus 1.5 T.

PURPOSE: To assess the gadolinium-based macromolecular intravascular contrast agent P792 for magnetic resonance angiography (MRA) at magnetic field strengths of 3.0 T, in comparison to 1.5 T, in rabbits. MATERIALS AND METHODS: Eleven female New Zealand rabbits of the same age served as the animal model. Dose relationship testing was performed with 2 doses (13 and 25 micromol/kg; n = 4 per group) of P792 as compared with a single dose (100 micromol/kg; n = 3) of gadoterate meglumine (Gd-DOTA). All animals underwent contrast-enhanced MRA of the abdominal aorta and its branches on 2 occasions separated by 72 hours. The particular doses were administered in random order. Contrast-enhanced MRA was performed on 3.0 and 1.5 T whole-body MR systems, using a fast 3D spoiled gradient recalled echo sequence. Data acquisition was performed before and up to 10 minutes after administration of intravenous contrast material. Image quality was judged on a 4-point-Likert scale. Signal-to-noise and contrast-to-noise measurements were performed; statistical differences (P < 0.05) between the groups were determined. RESULTS: P792 and Gd-DOTA yielded high-quality MR angiograms in rabbits in all cases. Although image quality within the first 3 minutes after contrast material administration was equal for both agents, P792 at a dose of 25 micromol/kg was considered superior to Gd-DOTA at the later time points. Signal-to-noise and contrast-to-noise values of the higher dose of P792 were statistically significantly higher than those of Gd-DOTA in the post-bolus phase. CONCLUSIONS: P792 seems to be well suited for high-quality early phase and equilibrium phase MRA in rabbits at a field strength of 3.0 T, on the basis of this initial evaluation in an animal model.

Renal arteries: comparison of steady-state free precession MR angiography and contrast-enhanced MR angiography.

All participants provided informed consent to participate in this study, which was approved by the institutional review board. Breath-hold three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography was compared with 3D contrast material-enhanced MR angiography in patients suspected of having renal artery stenosis. Two radiologists assessed visualization of renal arteries and detection of vascular disease. With SSFP MR angiography, 39 of 41 renal arteries in 19 patients were correctly detected. Relevant stenoses were correctly identified with SSFP MR angiography in two patients. In two patients, SSFP MR angiographic data sets led to false-positive overgrading of vascular disease. Fast breath-hold 3D SSFP MR angiography appears to be feasible for MR angiography of renal arteries.