High-resolution cine MRI with TGRAPPA for fast assessment of left ventricular function at 3 Tesla.

PURPOSE: To implement and evaluate the accuracy of multislice dual-breath hold cine MR for analysis of global systolic and diastolic left ventricular function at 3T. MATERIALS AND METHODS: 25 patients referred to cardiac MR underwent cine imaging at 3T (MAGNETOM Verio) using prospective triggered SSFP (TR 3.1 ms; TE 1.4 ms; FA 60°). Analysis of LV function was performed using a standard non-accelerated single-slice approach (STD) with multiple breath-holds and an accelerated multi-slice technique (TGRAPPA; R=4) encompassing the ventricles with 5 slices/breath-hold. Parameters of spatial and temporal resolution were kept identical (pixel: 1.9 × 2.5 mm(2); temporal resolution: 47 ms). Data of both acquisition techniques were analyzed by two readers using semiautomatic algorithms (syngoARGUS) with respect to EDV, ESV, EF, myocardial mass (MM), peak filling rate (PFR) and peak ejection rate (PER) including assessment of interobserver agreement. RESULTS: Volumetric results of the TGRAPPA approach did not show significant differences to the STD approach for left ventricular ejection fraction (62.3 ± 10.6 vs. 61.0 ± 8.4, P=0.2), end-diastolic volume (135.8 ± 47.5 vs. 130.8 ± 46.4, P=0.07), endsystolic volume (53.0 ± 29.7 vs. 53.1 ± 32.7, P=0.99) and myocardial mass (114.2 ± 32.5 vs. 114.6±30.6, P=0.9). Moreover, a comparison of peak ejection rate (601.3 ± 190.2 vs. 590.8 ± 218.2, P=0.8) and peak filling rate (535.1±191.2 vs. 535.4 ± 210.7, P=0.99) did not reveal significant differences between the two groups. Limits in interobserver agreement were low for all systolic and diastolic parameters in both groups (P ≥ 0.05). Total acquisition time for STD was 273 ± 124 s and 34 ± 5 s for TGRAPPA (P ≤ 0.001). Evaluation time for standard and multislice approach was equal (10.8 ± 1.4 vs. 9.8 ± 2.1 min; P=0.08).

Dynamic 3D-MR-angiography for assessing rheumatoid disease of the hand--a feasibility study.

PURPOSE: To investigate highly temporally resolved MR-angiography (MRA) with time-resolved imaging with stochastic trajectories (TWIST) of the hand as supplementary tool for dynamic assessment of synovitis and vascular pathologies in rheumatoid diseases. MATERIAL AND METHODS: A coronal dynamic TWIST-MRA-sequence (0.7 mm × 0.7 mm × 1.4 mm, temporal resolution 2.5s, time of acquisition 4 min) of the predominantly affected hand of 17 patients with suspected rheumatoid disease was acquired after contrast administration (Multihance, Bracco Imaging SpA) at 3T (Magnetom VERIO, 8-channel-knee-coil, Siemens Healthcare). As standard of reference, contrast enhanced non fat-saturated coronal and fat-saturated axial T1-w sequences were acquired. These static sequences and the dynamic TWIST-MRA-maximum-intensity-projections (MIP) were separately assessed by two readers in consensus, recording the number of synovial lesions (wrist, intercarpal, metacarpophaleangal/proximal/distal interphalangeal joints), signs of tenosynovitis and vasculitis. Diagnostic confidence was rated (4-point-scale: 4=excellent; 1=non-diagnostic). Statistical significance was tested using the Wilcoxon-rank-sum-test. RESULTS: An insignificantly lower number of synovial lesions (n=72 vs. 89; p=0.1) and only 3/9 cases with tenosynovitis were identified by the TWIST-MRA. For detected lesions, diagnostic confidence was comparable (MRA: 3.64; static T1-w post contrast: 3.47). In patients with high clinical activity dynamic MRA showed very early synovial enhancement. Only dynamic MRA detected 3 cases of vasculitis (subsequently confirmed with digital-subtraction-angiography). CONCLUSION: TWIST-MRA facilitates fast detection of synovitis. Although dynamic MRA of the hand is inferior to static contrast enhanced sequences in assessing the number of synovitic and tenosynovitic lesions, its high temporal resolution allows for fast visual grading of disease activity and assessment of vasculitis without additional contrast material application.

MR-lymphangiography at 3.0 T--a feasibility study.

The purpose of this study was to establish and evaluate contrast-enhanced MR-lymphangiography (MRL) at 3.0 T for detection and visualization of abnormalities of the peripheral lymphatic system. Sixteen patients were examined with a highly resolved isotropic T1w-3D-GRE-(FLASH) sequence (TR 3.76 ms/TE 1.45 ms/FA 30 degrees /voxel-size 0.8 x 0.8 x 0.8 mm(3)) at 3T after intracutaneous injection of gadolinium-diethylene-triamine-pentaacetic-acid. Two radiologists evaluated overall image quality, contrast between lymph vessels and background tissue, venous contamination, visualized levels, and fat-saturation-homogeneity on 3D maximum-intensity projections. Overall image quality was good to excellent, and all examinations were diagnostic except one, where contrast medium was injected subcutaneously instead of intracutaneously. Overall image quality was good to excellent in 12/16 cases, depiction of lymph vessels was good to excellent in 15/16 cases. Venous contamination was always present, but diagnostically problematical in only one case. Instant lymphatic drainage was observed in unaffected extremities, reaching the pelvic level after approximately 10 min. Lymphatic drainage was considerably delayed in lymphedematous extremities. Ectatic lymph vessels, entrapment, and diffuse drainage of contrast medium correlated with impaired lymphatic drainage. In conclusion, MRL at 3.0 T provides very high spatial resolution and anatomical detail of normal and abnormal peripheral lymph vessels. MRL may thus become a valuable tool for microsurgical treatment planning and monitoring.

Assessment of Myocardial Viability with 3D MRI at 3 T.

OBJECTIVE: The aim of our study was to show that spatial resolution can be improved without loss of diagnostic accuracy if a 3D inversion recovery gradient-recalled echo (GRE) sequence is used instead of a segmented inversion recovery GRE at 3 T for the assessment of myocardial infarction. SUBJECTS AND METHODS: Fifteen patients with myocardial infarction were examined on a 3-T MR system. A segmented breath-hold 3D inversion recovery GRE technique with a voxel size of 6.3 mm(3) was compared with a breath-hold standard 2D inversion recovery GRE technique with a voxel size of 21.3 mm(3) for the detection of delayed enhancement. Contrast-to-noise ratios (CNRs) were calculated and infarct volumes were measured. Detection and transmural extent of infarctions were evaluated using kappa statistics. Total acquisition times were measured for both sequences. RESULTS: The CNR in the 3D technique did not show any significant difference compared with the 2D technique. The correlation coefficients of the infarct volumes determined with the 3D and 2D inversion recovery GRE studies at 3 T were r = 0.99 (p < 0.001). The assessment of the presence of hyperenhanced myocardium in all segments and the evaluation of transmurality resulted in very good agreement (kappa = 0.98 and kappa = 0.90). Total acquisition time was significantly shorter with the 3D technique (2.4 +/- 0.9 minutes) than with the 2D technique (4.9 +/- 1.5 minutes) (p < 0.001). CONCLUSION: The use of a 3D inversion recovery GRE sequence at 3 T allows accurate assessment of myocardial infarction without loss of CNR compared with the standard 2D technique. Furthermore, data acquisition time can be significantly reduced.

Low dose gadobenate dimeglumine for imaging of chronic myocardial infarction in comparison with standard dose gadopentetate dimeglumine.

OBJECTIVES: Gadobenate dimeglumine has a 2-fold higher T1 relaxivity compared with gadopentetate dimeglumine and can be used for imaging delayed enhancement in the assessment of myocardial infarction. The purpose of this study was to compare 0.1 mmoL/kg gadobenate dimeglumine (Gd-BOPTA, MultiHance, Bracco Imaging SpA, Milan, Italy) with 0.2 mmoL/kg gadopentetate dimeglumine (Gd-DTPA, Magnevist, Bayer-Schering Pharma AG, Berlin, Germany) in cardiac magnetic resonance imaging. MATERIALS AND METHODS: The study was performed in accordance with the institutional review board. Two groups of 20 patients underwent magnetic resonance examinations for evaluation of chronic myocardial infarction. Although group 1 received gadobenate dimeglumine at a dose of 0.1 mmoL/kg, group 2 received gadopentetate dimeglumine at a dose of 0.2 mmoL/kg. Single shot inversion recovery (IR) steady-state free precession (SSFP), and IR gradient echo sequence (GRE) sequences were used for imaging delayed enhancement. The sizes of myocardial infarctions were measured for both contrast agents in both imaging techniques by 2 readers. Bland-Altman analyses were performed for each sequence and gadolinium chelate. Furthermore, the transmural extent of myocardial infarction was assessed by 2 readers according to the 17-segment model for both contrast media and both sequences and kappa values were calculated. Signal-to-noise ratios for infarcted myocardium, normal myocardium, and the left ventricular cavity were measured, and the contrast-to-noise ratios of infarcted compared with normal myocardium (CNRinf-myo) and infarcted myocardium in relation to the left ventricular cavities (CNRinf-LVC) were calculated. RESULTS: The Bland-Altman plots in the assessment of infarction size did not reveal a systematic bias between the 2 readers. The mean difference between reader 1 and 2 was less than 0.9 cm3 of mean infarction volume. Assessment of interobserver agreement regarding the transmural extent of myocardial infarction resulted in kappa values of kappa = 0.845 (IR SSFP) and kappa = 0.874 (IR GRE) in gadobenate-enhanced images and kappa = 0.841 (IR SSFP) and kappa = 0.833 (IR GRE) after administration of gadopentetate. CNRinf-normal was significantly higher on the images of group 1 (gadobenate) compared with group 2 (gadopentetate) in both sequences (single shot IR SSFP: 18.1 +/- 10.1 vs. 12.1 +/- 6.7; P = 0.032 and IR GRE: 27.2 +/- 5.8 vs. 19.7 +/- 5.9; P = 0.005). The mean value of CNRinf-LVC for the group examined with Gd-BOPTA was lower, though not significantly, compared with the group examined with Gd-DTPA in IR GRE technique, whereas CNRinf-LVC for IR SSFP resulted in equal values (single shot IR SSFP: 1.2 +/- 5.2 vs. 1.1 +/- 6.8; P = n.s. and IR GRE 2.4 +/- 5.8 vs. 5.8 +/- 7.9; P = n.s.). CONCLUSIONS: Low dose Gd-BOPTA resulted in significantly higher CNRinf-myo compared with standard dose Gd-DTPA in imaging of myocardial infarction with IR SSFP and IR GRE sequences. Demarcation of infarcted myocardium from the left ventricular cavity assessed by CNR showed no significant difference after application of either contrast media in both imaging techniques.

Inversion recovery single-shot TurboFLASH for assessment of myocardial infarction at 3 Tesla.

PURPOSE: The aim of the study was to assess the diagnostic accuracy of imaging myocardial infarction with a single-shot inversion recovery turbofast low-angle shot (SS IR turboFLASH) sequence at 3.0 Tesla in comparison with an established segmented inversion recovery turboFLASH sequence at 1.5 Tesla. MATERIALS AND METHODS: Fifteen patients with myocardial infarction were examined at a 1.5 Tesla magnetic resonance (MR) System (Avanto, Siemens, Medical Solutions) and at a 3.0 Tesla MR system (TIM Trio, Siemens, Medical Solutions). Imaging delayed enhancement was started 15 minutes after application of contrast material. A SS IR turboFLASH was performed at 3.0 Tesla and compared with a segmented IR turboFLASH sequence at 1.5 and at 3.0 Tesla. The IR turboFLASH sequence at 1.5 Tesla served as reference method. Infarct volumes, contrast/noise ratio (CNR) of infarcted and normal myocardium were compared with the reference method. RESULTS: The Single-Shot IR turboFLASH technique allows imaging 9 slices during a single breath-hold. The CNR between infarction and normal myocardium of the reference method was 6.4 at 1.5 Tesla. The mean value of CNR of the IR turboFLASH sequence was 7.3 at 3.0 Tesla for the single-shot technique and 14.1 at 3.0 Tesla for the segmented technique. No significant difference was found for the CNR values of the reference technique at 1.5 Tesla and the single-shot technique at 3.0 Tesla, however for the comparison of the segmented technique at 1.5 and at 3 Tesla (P = 0.0001). The correlation coefficients of the infarct volumes, determined with the Single-Shot IR turboFLASH and the segmented IR turboFLASH technique at 3.0 compared with the reference method, were r = 0.95 (P < 0.0001) and r = 0.95 (P < 0.0001). CONCLUSION: The loss of CNR, which is caused by replacement of the segmented technique by the single-shot technique, is completely compensated by the approximately 2-fold CNR increase at the higher field strength. The IR turboFLASH technique at 3.0 Tesla IR can be used as a single-shot technique with acquisition of 9 slices during a single breath-hold without loss of diagnostic accuracy compared with the segmented technique at 1.5 Tesla.