Improved fat-suppression homogeneity with mDIXON turbo spin echo (TSE) in pediatric spine imaging at 3.0 T

Cardiothoracic Magnetic Resonance Angiography

Catheter-based angiography is regarded as the clinical reference imaging technique for vessel imaging; however, it is invasive and is currently used for intervention or physiologic measurements. Contrast enhanced magnetic resonance angiography (MRA) with gadolinium-based contrast agents can be performed as a three-dimensional (3D) MRA or as a time resolved 3D (4D) MRA without physiologic synchronization, in which case cardiac and respiratory motion may blur the edges of the vessels and cardiac chambers. Ferumoxytol has recently been a popular contrast agent for MRA in patients with chronic renal failure. Noncontrast 3D MRA with ECG gating and respiratory navigation are safe and accurate noninvasive cross-sectional imaging techniques for the visualization of great vessels of the heart and coronary arteries in a variety of cardiovascular disorders including complex congenital heart diseases. Noncontrast flow dependent MRA techniques such as time of flight, phase contrast, and black-blood MRA techniques can be used as complementary or primary techniques. Here we review both conventional and relatively new contrast enhanced and non-contrast enhanced MRA techniques including ferumoxytol enhanced MRA, and bright-blood and water-fat separation based noncontrast 3D MRA techniques.

State-of-the-art magnetic resonance imaging sequences for pediatric body imaging

Longer examination time, need for anesthesia in smaller children and the inability of most children to hold their breath are major limitations of MRI in pediatric body imaging. Fortunately, with technical advances, many new and upcoming MRI sequences are overcoming these limitations. Advances in data acquisition and k-space sampling methods have enabled sequences with improved temporal and spatial resolution, and minimal artifacts. Sequences to minimize movement artifacts mainly utilize radial k-space filling, and examples include the stack-of-stars method for T1-weighted imaging and the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)/BLADE method for T2-weighted imaging. Similarly, the sequences with improved temporal resolution and the ability to obtain multiple phases in a single breath-hold in dynamic imaging mainly use some form of partial k-space filling method. New sequences use a variable combination of data sampling methods like compressed sensing, golden-angle radial k-space filling, parallel imaging and partial k-space filling to achieve free-breathing, faster sequences that could be useful for pediatric abdominal and thoracic imaging. Simultaneous multi-slice method has improved diffusion-weighted imaging (DWI) with reduction in scan time and artifacts. In this review, we provide an overview of data sampling methods like parallel imaging, compressed sensing, radial k-space sampling, partial k-space sampling and simultaneous multi-slice. This is followed by newer available and upcoming sequences for T1-, T2- and DWI based on these other advances. We also discuss the Dixon method and newer approaches to reducing metal artifacts.

Evaluating Compressed SENSE (CS) MRI Metal Artifact Reduction Using Pig L-Spine Phantom and Transplant Patients: Focused on the CS-SEMAC (SPIR), mDixon(O-MAR) and STIR Techniques

This study evaluates the clinical usefulness of the images obtained after applying mDixon (O-MAR), CS-SEMAC (SPIR), and STIR techniques to Pig L-Spine Phantom and transplant patients according to the difference in the reduction in metal artifacts and provides the optimal MAR image technique. This study was conducted with Phantom and 30 transplant patients who had an implant on the L-Spine (22 men, 8 women, mean age: 64.2 ± 12.98). All data analyzed were evaluated, using Philips Ingenia 3.0T CX. As pulse sequences, applied to the analysis, mDixon (O-MAR), CS-SEMAC (SPIR), and STIR were used. As the coil used to obtain data, the dStream Head Spine Coil was used. When tested directly applying to the transplant patients in the conditions the same as for the Phantom, as for the MAR effect of T1 and T2 images, the SNR value showed the highest effect on the increase in the signal in T1, T2 CS-SEMAC (SPIR), followed by mDixon (O-MAR) and STIR, which was the same result as the Phantom (p < 0.05). In addition, in the results of the histogram measurement in both of the subjects, Phantom and transplant patients, the count of T1, the T2 Sagittal image was the highest in T1, T2 STIR, followed by T1, T2 mDixon (O-MAR) and T1, and T2 CS-SEMAC (SPIR). As a result of the qualitative analysis, the quality was the best in T2 CS-SEMAC(SPIR) (c), followed by mDixon (O-MAR) (b) and T2 STIR (a). In conclusion, when the MAR effect on the Pig L-spine Phantom and Transplant patients was compared, it was noted that the CS-SEMAC (SPIR) technique was the most excellent in the following order: STIR < mDixon (O-MAR) < CS-SEMAC (SPIR).

Practical Aspects of novel MRI Techniques in Neuroradiology: Part 2 - Acceleration Methods and Implications for Individual Regions

BACKGROUND

 Recently introduced MRI techniques facilitate accelerated examinations or increased resolution with the same duration. Further techniques offer homogeneous image quality in regions with anatomical transitions. The question arises whether and how these techniques can be adopted for routine diagnostic imaging.

METHODS

 Narrative review with an educational focus based on current literature research and practical experiences of different professions involved (physicians, MRI technologists/radiographers, physics/biomedical engineering). Different hardware manufacturers are considered.

RESULTS AND CONCLUSIONS

 Compressed sensing and simultaneous multi-slice imaging are novel acceleration techniques with different yet complimentary applications. They do not suffer from classical signal-to-noise-ratio penalties. Combining 3 D and acceleration techniques facilitates new broader examination protocols, particularly for clinical brain imaging. In further regions of the nervous systems mainly specific applications appear to benefit from recent technological improvements.

KEY POINTS

  · New acceleration techniques allow for faster or higher resolution examinations.. · New brain imaging approaches have evolved, including more universal examination protocols.. · Other regions of the nervous system are dominated by targeted applications of recently introduced MRI techniques..

CITATION FORMAT

· Sundermann B, Billebaut B, Bauer J et al. Practical Aspects of novel MRI Techniques in Neuroradiology: Part 2 - Acceleration Methods and Implications for Individual Regions. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1800-8789.

Comparison of in-phase and opposed-phase T1W gradient echo and T2W fast spin echo dixon chemical shift imaging for the assessment of non-neoplastic, benign neoplastic and malignant marrow lesions

OBJECTIVE

The objective of this study is to compare T1-weighted gradient echo (T1W GrE: control technique) chemical shift imaging (CSI) with T2-weighted fast spin echo (T2W FSE: experimental technique) CSI for differentiating non-neoplastic and neoplastic marrow lesions.

MATERIALS AND METHODS

Patients undergoing MRI for various marrow lesions were investigated with T1W GrE and T2W FSE Dixon CSI. Signal intensity (SI) change between in-phase (IP) and opposed-phase (OP) sequences was calculated, and SI drop > 20% considered to represent non-neoplastic lesions while SI drop < 20% considered to represent neoplastic lesions. Final diagnosis was based on imaging features (n = 42) or histology (n = 43) and classified as non-neoplastic, benign neoplastic, and malignant neoplastic. Inter-observer and inter-technique agreement between 2 readers was calculated.

RESULTS

The study included 85 patients (44 males and 41 females; mean age 41.1 years, range 2-83 years). Final diagnosis included 19 (22.4%) non-neoplastic lesions, 27 (31.8%) benign neoplasms, and 39 (45.9%) malignant neoplasms. On T1W GrE CSI, 19-21 lesions were classed as non-neoplastic and 64-66 as neoplastic, while on T2W FSE Dixon CSI, 22-24 lesions were classed as non-neoplastic and 61-64 as neoplastic. Lesion classification matched between the 2 techniques in 91.8-96.5% of cases. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of T1W GrE CSI for differentiating non-neoplastic and neoplastic marrow lesions were 66.7-72.2%, 88.1-89.6%, 61.9-63.2%, 90.9-92.2%, and 84.7%, and of T2W FSE Dixon CSI were 72.2-77.8%, 85.1-86.6%, 58.3-59.1%, 92.1-93.4%, and 83.5%.

CONCLUSIONS

T1W GrE CSI and T2W FSE Dixon CSI produce similar results in the assessment of non-neoplastic and neoplastic marrow lesions.

Comparison of lumbar degenerative disc disease using conventional fast spin echo T2W MRI and T2 fast spin echo dixon sequences

OBJECTIVES

To compare the grading of lumbar degenerative disc disease (DDD), Modic end-plate changes (MEPC) and identification of high intensity zones (HIZ) on a combination of sagittal T₁weighted turbo spin echo (T₁W TSE), T₂weighted fast spin echo (T₂W FSE) and short tau inversion recovery (STIR) sequences (routine protocol) with a single sagittal T₂W FSE Dixon MRI sequence which provides in-phase, opposed-phase, water only and fat only images in a single acquisition (Dixon protocol).

METHODS

50 patients underwent lumbar spine MRI using the routine protocol with the addition of a T₂W FSE Dixon sequence. DDD grade, MEPC and HIZ for each disc level were assessed on the routine and Dixon protocols. Each protocol was reviewed independently by three readers (consultant musculoskeletal radiologists with 26-, 8- and 4 years' experience), allowing assessment of inter-reader agreement and inter protocol agreement for each assessed variable.

RESULTS

The study included 17 males and 33 females (mean age 51 years; range 8-82 years). Inter-reader agreement for DDD grade on the routine protocol was 0.57 and for the Dixon protocol was 0.63 (p = 0.08). Inter-reader agreement for MEPC on the routine protocol was 0.45 and for the Dixon protocol was 0.53 (p = 0.02), and inter-reader agreement for identification of the HIZ on the routine protocol was 0.52 and for the Dixon protocol was 0.46 (p = 0.27). Intersequence agreement for DDD grade ranged from 0.61 to 0.97, for MEPC 0.46-0.62 and for HIZ 0.39-0.5.

CONCLUSION

A single sagittal T₂W FSE Dixon MRI sequence could potentially replace the routine three sagittal sequence protocol for assessment of lumbar DDD, MEPC and HIZ resulting in ~60% time saving.

ADVANCES IN KNOWLEDGE

Grading of lumbar DDD, presence of Modic changes and high intensity zones were compared on sagittal T₁W TSE, T₂W FSE and STIR sequences with a T₂W FSE Dixon sequence, with fair-to-good correlation suggesting that three conventional sequences could be replaced by a single Dixon sequence.

Robustness of a Combined Modified Dixon and PROPELLER Sequence with Two Interleaved Echoes in Clinical Head and Neck MRI

Purpose:

The combination of modified Dixon (mDixon) and periodically rotated overlapping parallel lines with enhanced reconstruction sequence with two interleaved echoes, which promotes uniform fat-suppression and motion insensitivity, has recently become available for commercial magnetic resonance imaging (MRI) scanners. To compare the robustness of this combination sequence with that of standard Cartesian mDixon sequence for fat-suppressed T₂-weighted imaging in clinical head and neck MRI.

Methods:

Fifty patients with head and neck tumors were involved this study. All patients underwent MRI using both the combination and standard sequences. Two radiologists independently scored motion artifacts and water–fat separation error using a 4-point scale (1, unacceptable; 4, excellent). Furthermore, comprehensive comparative evaluation was performed using a 5-point scale (1, substantially inferior; 5, substantially superior). Data were statistically analyzed using the Wilcoxon signed-rank test.

Results:

In the motion artifact assessment, ratings of 3 or 4 points were assigned to 45% (observer-1, 58.0%; observer-2, 32.0%) and 97% (100%; 94.0%) of images for the standard and combination sequences, respectively (P < 0.001). For the water–fat separation error assessment, ratings of 3 or 4 points were assigned to 100% (100%; 100%) and 85% (84.0%; 86.0%) of images, respectively (P < 0.001). In the comprehensive evaluation, of the 100 cases (observer-1, 50; observer-2, 50), 96 were rated at four or five points. In cases with slight or no motion artifacts and water–fat separation errors, the combination sequence was superior to the standard sequence in term of noise and sharpness, and equal in terms of contrast.

Conclusion:

Although water–fat separation errors increased significantly in the combination sequence, most of these were acceptable. The significantly decreased motion artifacts in the combination sequence significantly improved image quality overall.

The Utility of Modified Dixon Turbo Spin Echo Shoulder Magnetic Resonance Arthrography in Assessing Rotator Cuff Disorder and Evaluating the Rotator Cuff Muscles

RATIONALE AND OBJECTIVES

To compare the diagnostic ability of modified Dixon (mDixon) turbo spin echo (TSE) T1-weighted (T1W) shoulder magnetic resonance arthrography (MRA) with that of conventional shoulder MRA, and evaluate the feasibility of mDixon TSE in-phase (IP) images in measuring the fat fraction and size of rotator cuff muscles.

MATERIALS AND METHODS

This retrospective study included 57 patients who underwent 3T shoulder MRA examinations with conventional and mDixon TSE T1W images (mean age: 56.7 years; range: 20-78 years). Two musculoskeletal radiologists independently evaluated the rotator cuff tendons with fat saturated T1W images and mDixon TSE T1W water images. Occupation ratios measured on T1W and mDixon TSE T1W IP images were compared. The fat fraction of the supraspinatus from the mDixon TSE T1W images was calculated and correlated with fatty infiltration of the supraspinatus on T1W images.

RESULTS

For tendon pathology, the kappa value for inter-sequence and inter-reader agreement was 0.957 (95% confidence interval [CI]: 0.923-0.990) and 0.839 (95% CI: 0.778-0.899), respectively. For retear, the kappa value for inter-sequence and inter-reader agreement was 0.913 (95% CI: 0.796-1.000) and 0.779 (95% CI: 0.594-0.963), respectively. The intraclass correlation coefficient for both occupation ratios was 0.986 (95% CI: 0.973-0.993). Comparison of mDixon TSE T1W fat fraction with Goutallier grade showed a strong positive linear correlation (r = 0.929).

CONCLUSIONS

The mDixon TSE T1W sequence is a good alternative to conventional sequences in shoulder MRA for evaluating rotator cuff pathology. Furthermore, this sequence provides information on the size and fat infiltration of rotator cuff muscles.

REACT - A novel flow-independent non-gated non-contrast MR angiography technique using magnetization-prepared 3D non-balanced dual-echo dixon method: Preliminary clinical experience

Flow-independent relaxation-based non-contrast MR angiography techniques yield good signal-to-noise ratio and high blood-tissue contrast, complementing non-contrast flow-dependent and contrast-enhanced MR angiography techniques in the assessment of vascular disorders. However, these techniques often suffer from imaging artifacts at high magnetic field strengths or across large fields-of-view. Relaxation-Enhanced Angiography without Contrast and Triggering (REACT) is a recently introduced flow-independent non-gated non-contrast three-dimensional MR angiography technique that has been developed to mitigate some of these issues. We present our initial experience with the clinical applications of REACT in imaging disorders of the central and peripheral vascular systems.

Neuroimaging for the Neurologist: Clinical MRI and Future Trends

MRI is a commonly used diagnostic tool in neurology, and all neurologists should possess a working knowledge of imaging fundamentals. An overview of current and impending MRI techniques is presented to help the referring clinician communicate better with the imaging department, understand the utility and limitations of current and emerging technology, improve specificity and appropriateness when ordering MRI studies, and recognize key findings.

Detection of vertebral metastases: a comparison between the modified Dixon turbo spin echo T2 weighted MRI and conventional T1 weighted MRI: a preliminary study in a tertiary centre

OBJECTIVE

To compare the diagnostic performance of modified Dixon (mDixon) turbo spin echo (TSE) T₂ weighted MRI and conventional T₁ weighted MRI in vertebral metastasis detection.

METHODS

Between September 2014 and October 2016, 33 patients with 68 metastases who had undergone whole-spine MRI were enrolled. The following sagittal image sets were evaluated: T₁WI, and mDixon TSE T₂ weighted water and fat images. Two radiologists independently evaluated each image-set for metastasis. The MR findings were compared with positron emission tomography-CT (PET-CT) scans. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each sequence. The diagnostic performance of each sequence was evaluated using receiver operating characteristic (ROC) curves.

RESULTS

Sensitivity, specificity, PPV and NPV for reviewer 1 were 83.8, 99.1, 89.1 and 98.6%, respectively, with T₁WI; 79.4, 98.8, 85.7 and 98.2%, respectively, with mDixon TSE T₂ weighted water imaging; and 86.8, 99.1, 89.4 and 98.8%, respectively, with mDixon TSE T₂ weighted fat imaging. For reviewer 2, the respective scores were 91.2, 99.2, 91.2 and 99.2%; 85.3, 99.5, 93.4 and 98.7%; and 89.7, 99.3, 92.4 and 99.1%. With PET-CT as the gold standard, the ROC curves of the three sequences showed no significant difference (all p > 0.05).

CONCLUSION

The diagnostic performance of mDixon TSE T₂ weighted water and fat imaging was comparable to that of conventional T₁WI in the detection of vertebral metastases. Advances in knowledge: mDixon TSE T₂WI can be a good alternative to conventional T₁WI for detecting vertebral metastases.