3D T1 Gradient Echo Research Articles

Three-dimensional heavily T2-weighted FLAIR in the detection of blood-labyrinthine barrier leakage in patients with sudden sensorineural hearing loss: comparison with T1 sequences and application of deep learning-based reconstruction.

Blood-labyrinthine barrier leakage has been reported in sudden sensorineural hearing loss (SSNHL). We compared immediate post-contrast 3D heavily T2-weighted fluid-attenuated inversion recovery (FLAIR), T1 spin echo (SE), and 3D T1 gradient echo (GRE) sequences, and heavily T2-weighted FLAIR (hvT2F) with and without deep learning-based reconstruction (DLR) in detecting perilymphatic enhancement. Fifty-four patients with unilateral SSNHL who underwent ear MRI with three sequences were included. We compared asymmetry scores, confidence scores, and detection rates of perilymphatic enhancement among the three sequences and obtained 3D hvT2F with DLR from 35 patients. The above parameters and subjective image quality between 3D hvT2F with and without DLR were compared. Asymmetry scores and detection rate of 3D hvT2F were significantly higher than 3D GRE T1 and SE T1 (respectively, 1.37, 0.11, 0.19; p < 0.001). Asymmetry scores significantly increased with DLR compared to 3D hvT2F for experienced and inexperienced readers (respectively, 1.77 vs. 1.40, p = 0.036; 1.49 vs. 1.03, p = 0.012). The detection rate significantly increased only for the latter (57.1% vs. 31.4%, p = 0.022). Patients with perilymphatic enhancement had significantly higher air conduction thresholds on initial (77.96 vs. 57.79, p = 0.002) and 5days after presentation (63.38 vs. 41.85, p = 0.019). 3D hvT2F significantly increased the detectability of perilymphatic enhancement compared to 3D GRE T1 and SE T1. DLR further improved the conspicuity of perilymphatic enhancement in 3D hvT2F. 3D hvT2F and DLR are useful for evaluating blood-labyrinthine barrier leakage; furthermore, they might provide prognostic value in the early post-treatment period. Ten-minute post-contrast 3D heavily T2-weighed FLAIR imaging is a potentially efficacious sequence in demonstrating perilymphatic enhancement in patients with sudden sensorineural hearing loss and may be further improved by deep learning-based reconstruction. • 3D heavily T2-weighted FLAIR (3D hvT2F) is a sequence sensitive in detecting low concentrations of contrast in the perilymphatic space. • 3D hvT2F sequences properly demonstrated perilymphatic enhancement in sudden sensorineural hearing loss compared to T1 sequences and were further improved by deep learning-based reconstruction (DLR). • 3D hvT2F and DLR are efficacious sequences in detecting blood-labyrinthine barrier leakage and with potential prognostic information.

Shortening the acquisition time of whole-body MRI: 3D T1 gradient echo Dixon vs fast spin echo for metastatic screening in prostate cancer.

To compare 3D T1-weighted fast spin echo (FSE) and 3D T1-weighted gradient echo (GE) mDixon as morphologic sequences to complement diffusion-weighted imaging (DWI) for the metastatic screening in prostate cancer (PCa) patients. Thirty PCa patients at high risk of metastases prospectively underwent both a 3D T1 FSE (14 min) and a rapid 3D T1 GEmDixon (1 min 20 s) sequences within a WB-MRI protocol. Two readers assessed the diagnostic performance of the FSE/Fat/in-phase (IP)/IP+Fat sequences in detecting bone and node metastases. The reference standard was established by a panel of four physicians on the basis of all baseline and follow-up imaging, biological and clinical information. The reproducibility of readings, predictive accuracy (Acc) from ROC curves analysis, and contrast-to-reference ratio (CRR) in lesions were assessed for each sequence. In bone and lymph nodes (per-region analysis), reproducibility was at least good for all sequences/readers, except for nodes in the common iliac/inguinal regions. In bone (per-organ analysis), Acc of FSE was superior to that of mDixon (difference + 4%, p < 0.0083). In nodes (per-organ analysis), Acc of Fat was superior to that of other sequences (difference + 4% to + 6% depending on reader, p < 0.0083). In the per-patient analysis, Acc of FSE was superior to that of mDixon (difference + 4% to + 6% depending on sequence, p < 0.0083). Fat images had higher CRR compared with FSE in the thoracic spine, the bony pelvis and lymph node metastases (p < 0.025). 3D T1 GEmDixon may replace 3D T1 FSE to complement DWI in WB-MRI for metastatic screening in PCa. It demonstrates an Acc ranging from + 4% to + 6% (nodes) to - 4% to - 6% (bone and patient staging) compared with FSE and considerably reduces the examination time, offering the perspective of acquiring WB-MRI examinations in less than 20 min. • The replacement of 3D T1 FSE by the 3D T1 GE mDixon as morphologic sequence to complement DWI drastically reduces the acquisition time of WB-MRI studies. • The 3D T1 GE mDixon sequence offers similar reproducibility of image readings compared with that of the 3D T1 FSE. • Differences in diagnostic accuracy are limited (+ 4%/+ 6% in favor of mDixon to detect node metastases; + 4%/+ 6% in favor of FSE to detect bone metastases/metastatic disease in a patient).

Presence of the posterior pituitary bright spot sign on MRI in the general population: a comparison between 1.5 and 3TMRI and between 2D-T1 spin-echo- and 3D-T1 gradient-echo sequences.

To describe the prevalence of the posterior pituitary bright spot (PPBS) in the general population on 1.5 and 3T MRI examinations and on 2D-T1 spin-echo (SE) and 3D-T1 gradient-echo (GE) sequences. 1017 subjects who received an MRI of the brain for aspecific neurological complaints were included. MRI was performed on 1.5T in 64.5% and on 3T in 35.5% of subjects. Presence of the PPBS was evaluated on sagittal 2D T1-SE echo images with slice thickness 3mm in 67.5% and on sagittal 3D T1-GE with slice thickness 0.9mm in 32.5% of subjects. The PPBS was detectable in 95.9% of subjects. After correction for sex and age, no statistically significant difference could be seen concerning PPBS detection between 1.5 and 3T MRI examinations (p = 0.533), nor between 2D T1-SE and 3D T1-GE sequences (p = 0.217). There was a statistically significant association between increasing age and the absence of the PPBS (p < 0.001). The PPBS could not be identified in 6.2% of male subjects, compared to 2.2% of female subjects (p = 0.01). Absence of the PPBS can be seen in 4.1% of patients undergoing MRI of the brain for non-endocrinological reasons. Neither field-strength nor the use of a thick-sliced 2D T1-SE versus a thin-sliced 3D T1-GE sequence influenced the detectability of the PPBS. There is a statistically significant association between increasing age and male sex and the absence of the PPBS.

MS lesions are better detected with 3D T1 gradient-echo than with 2D T1 spin-echo gadolinium-enhanced imaging at 3T.

In multiple sclerosis, gadolinium enhancement is used to classify lesions as active. Regarding the need for a standardized and accurate method for detection of multiple sclerosis activity, we compared 2D-spin-echo with 3D-gradient-echo T1WI for the detection of gadolinium-enhancing MS lesions. Fifty-eight patients with MS were prospectively imaged at 3T by using both 2D-spin-echo and 3D-gradient recalled-echo T1WI in random order after the injection of gadolinium. Blinded and independent evaluation was performed by a junior and a senior reader to count gadolinium-enhancing lesions and to characterize their location, size, pattern of enhancement, and the relative contrast between enhancing lesions and the adjacent white matter. Finally, the SNR and relative contrast of gadolinium-enhancing lesions were computed for both sequences by using simulations. Significantly more gadolinium-enhancing lesions were reported on 3D-gradient recalled-echo than on 2D-spin-echo (n = 59 versus n = 30 for the junior reader, P = .021; n = 77 versus n = 61 for the senior reader, P = .017). The difference between the 2 readers was significant on 2D-spin-echo (P = .044), for which images were less reproducible (κ = 0.51) than for 3D-gradient recalled-echo (κ = 0.65). Further comparisons showed that there were statistically more small lesions (<5 mm) on 3D-gradient recalled-echo than on 2D-spin-echo (P = .04), while other features were similar. Theoretic results from simulations predicted SNR and lesion contrast for 3D-gradient recalled-echo to be better than for 2D-spin-echo for visualization of small enhancing lesions and were, therefore, consistent with clinical observations. At 3T, 3D-gradient recalled-echo provides a higher detection rate of gadolinium-enhancing lesions, especially those with smaller size, with a better reproducibility; this finding suggests using 3D-gradient recalled-echo to detect MS activity, with potential impact in initiation, monitoring, and optimization of therapy.

The added value of double dose gadolinium enhanced 3D T2 fluid-attenuated inversion recovery for evaluating small brain metastases.

PurposeSingle dose gadolinium (Gd) enhanced fluid-attenuated inversion recovery (FLAIR) is helpful for visualizing superficial parenchymal metastases. However, the usefulness of FLAIR with a higher dose of Gd is uncertain. The aim of our study was two-folds: first, to prove that the signal to noise ratio (SNR) of small brain metastases is higher than large brain metastases on double-dose (DD) enhanced FLAIR and, second, to explore the added value of DD Gd enhanced FLAIR in relation to T1 GRE for evaluating small brain metastases.Materials and MethodsFor the first purpose, 50 pairs of small (2 mm<diameter≤5 mm) and large brain metastases (diameter >5 mm) were included. The difference in the SNR and contrast ratio (CR) between small and large metastases on DD Gd-enhanced 3D T2 FLAIR was compared by Wilcoxon signed-rank tests. For the second purpose, a total of 404 small metastases were included. The diagnostic sensitivities between 3D T1 gradient echo (GRE) alone and combined results of 3D T1 GRE and 3D T2 FLAIR were compared with McNemar test.ResultsThe SNR and CR of small brain metastases were significantly higher than those of large brain metastases (p<0.001). In qualitative analysis, the diagnostic sensitivities for small brain metastases were significantly higher for 3D T1 GRE plus 3D T2 FLAIR than 3D T1 GRE alone regardless of scan time (p<0.001).ConclusionSmall brain metastases showed higher signal intensity than large brain metastases on the DD Gd enhanced 3D T2 FLAIR images. DD Gd enhanced 3D T2 FLAIR imaging may have a complementary role to 3D T1 GRE for evaluating small brain metastases.

SU-E-J-175: Comparison of Prone and Supine MRI Sequences for the Purpose of Radiotherapy Treatment Planning for Breast Cancer

Purpose: The delineation of treatment volumes for breast cancer radiotherapy utilising standard CT images is associated with significant inter-observer variability. It has been proposed that MRI with improved quality soft tissue definition may reduce this inter-observer variability. The purpose of this study was to determine the optimum set-up and sequence for MRI-defined radiotherapy volume delineation. Methods: Six observers (2 radiologists, 4 radiation oncologists) were asked to score MRI quality for the purposes of radiotherapy delineation using the following scoring criteria where 0 — margin not recognisable (inability to discriminate) through to a score of 3, when margins were distinct (excellent discrimination). Supine breast MRI was achieved using a foam bridge to support a surface coil without touching the patient surface. T1 and T2 sequences were compared for both 1.5Tesla (1.5T) and 3T MRIs for a volunteer. Prone breast images were obtained using a 4 channel breast coil. Supine and prone breast MRIs were compared for T1 and T2 sequences for 3T for 2 volunteers. Results: Supine breast images were shown to be acceptable for the purpose of radiotherapy delineation with the 3T 2D T2 turbo spin echo sequences scoring 2s (fair discrimination) and 3s (excellent discrimination), most optimal. The prone 3D T1 gradient echo was the optimum of the supine and prone 3T images, however results were inconsistent with this sequence receiving a score of zero from one observer. Conclusion: Supine breast MRI scans can be achieved for the purpose of radiotherapy delineation. Scoring between observers was inconsistent when comparing scan sequences. This work has been supported by project grant 1033237 from Cancer Australia and The National Breast Cancer Foundation

MRCT: Synthetic CT Imaging for Radiation Oncology Using Magnetic Resonance Images

Purpose/Objective(s): MRI is an essential element of Radiation Oncology treatment planning. The ability of MRI data to yield synthetic CT images, specifically to define attenuation of skeletal features for dose calculation and image guidance support, was evaluated. Materials/Methods: Under a review board approved investigation, CT and various contrastMRI imageswere acquired of a dog. Imagevolumes acquired included 3D T1 gradient echo, T2 weighted, calculated water and fat (from a Dixon technique), and ultra short TE (UTE1, 70 microsecond echo time, followed by UTE2 at 3.7 ms). UTE1 images have signal intensities that are more strongly influenced by short T2 species, and show promise for separation of bone and air. Following intensity masking for separation of bone from air (using T1, UTE and water images), a classification algorithm (fuzzy c-means)was applied to themulti-spectralMRI volumes, yielding probability distributions for 5 classes (water, fat, brain, muscle, bone). Attenuationvalues were applied to each of the 5 classes and the resulting values were summed, yielding a synthetic CT (MRCT) volume. The actual CT volume was rigidly aligned with the MRI volumes (with specific focus on the skull). Regions of interest were defined based on increasing intensity thresholds on the CT scan (from400-1300HU in 300HUsteps), representing regions of increasing bone density. Intensities within these regions were evaluated on the MRCT. Intensities of MRI volumes of each contrast, as well as probabilities of class membership, were similarly evaluated within the same regions of interest. Results: Each of the input imaging sequences showed a trend of decreasing average signal intensity for regions generated via increasing CT thresholds, as expected due to the loss of signal in tissues with bone. All tissue classes except for bone decreased in membership probability in regions of increasing CT intensity, with the exception of the bone class, which increased with increasing CT value. Intensities within regions of varying bone density in the MRCT volume correlated strongly with those of the actual CT (R of 0.994). Digitally reconstructed radiographs from the actual CT volume were successfully aligned to matching projections through MRCT volumes without bias. Conclusions: The information present in MRI is sufficient to support identification and spatial mapping of skeletal features and classification can properly assign attenuation values to the heterogeneous skeletal tissues in the head. Further work will focus on assessing the accuracy of mapped attenuation of other tissues in the body and on treatment plan and IGRT comparisons using actual and synthetic CT data. Author Disclosure: Y. Cao: E. Research Grant; NIH. S. Hsu: None. A. Flammang: A. Employee; Siemens Corporate Research. J. Balter: E. Research Grant; NIH.

THE EFFECT OF SEQUENCE SELECTION AND FIELD STRENGTH ON DETECTION OF OSTEOCHONDRAL DEFECTS IN THE METACARPOPHALANGEAL JOINT

Six cadaver forelimbs were imaged in two high-field magnetic resonance (MR) systems and one low-field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2* gradient echo (GRE), T2-weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low-field system. PD fat saturated and 3D T1-weighted spoiled GRE images with and without fat suppression were acquired with the high-field systems. Lesions were measured and assigned a confidence score. The images obtained using high-field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low-field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low-field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low-field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high-field systems when compared with the low-field system.

Combined dynamic contrast-enhancement and serial 3D-subtraction analysis in magnetic resonance imaging of osteoid osteomas

The purpose of this study was to retrospectively correlate the results of dynamic contrast-enhanced magnetic resonance imaging (MRI) with histological and clinical diagnoses in patients with osteoid osteomas. Fifty-four patients with the MR diagnosis of osteoid osteoma were studied. MRI (1.5 Tesla) consisted of thin-section STIR sequences, dynamic 3D T1 gradient echo sequences during application of contrast material, and high-resolution postcontrast T1 spin echo sequences with fat saturation (maximum voxel size 0.6 x 0.6 x 3.0 mm). Evaluation was focused on serial image subtraction during the early phase after contrast injection and on time-intensity curves. The surrounding edema was helpful in finding the nidus in each lesion. In 49 of 54 patients (90.7%), the diagnosis of osteoid osteoma was certain or highly probable (sensitivity 1.0, positive predictive value 0.91). A total of 38 of 54 osteoid osteomas were histologically proven. Five MRI diagnoses were regarded as false positives. A similar proportion has been reported for computed tomography. Tailored high-resolution MR examinations with dynamic contrast enhancement can reliably diagnose osteoid osteomas and exactly localize the nidus without radiation exposure. We propose a stepwise approach with STIR sequences, dynamic contrast-enhanced scanning, and high-resolution postcontrast T1 spin echo sequences with fat saturation.

Feasibility of MRI in Experimentally Induced Inflammatory Small Bowel Disease: A Pilot Study in a Porcine Model

The purpose of this study was to compare the macroscopic and microscopic findings of experimentally induced inflammatory lesions in jejunum and ileum with magnetic resonance imaging (MRI) findings. Inflammatory small bowel lesions were experimentally induced in six pigs. Bowel segments in jejunum and ileum were isolated, and a solution with trinitrobenzenesulfonic acid and ethanol (TNBS-EtOH) was installed. MRI of the small bowel was performed 7 days after surgery. Before the MRI examination, a 6% mannitol solution was installed through a nasogastric tube. The MRI protocol consisted of single-shot turbo spin echo T2 sequences, steady state free precession (BFFE) sequences, and a 3D T1 gradient echo sequence with fat saturation and intravenous contrast. The following image findings were evaluated: increased bowel wall thickness (BWT), increased bowel wall enhancement (BWE), and bowel stenosis. After the MRI examination, the animals were sacrificed. The small bowel was removed and examined macroscopically and microscopically. Inflammatory lesions developed in jejunum and ileum in all animals. The lesions were visible macroscopically and microscopically. The microscopic findings consisted of variable degrees of inflammation, ulcer formation, and fibrosis. In jejunum the inflammatory lesions were not diagnosed with MRI, except in one pig with a bowel necrosis probably caused by an intramural injection or leakage of the TNBS-EtOH solution. In ileum the bowel wall thickness was increased and the inflammatory lesions were diagnosed with MRI. In conclusion, the inflammatory lesions were visible macroscopically and microscopically. Lesions in ileum had increased BWT and were possible to image with MRI. Lesions in jejunum had normal BWT and were not diagnosed with MRI, except in one pig with increased BWT probably caused by complications to the installation of TNBS-EtOH.

Percutaneous MR-guided discography in a low-field system using optical instrument tracking: a feasibility study.

To evaluate the feasibility of MRI-guided discography with optical tracking. 12 consecutive patients who had a clinical suspicion of lumbar discogenic pain and/or suggestive finding of disc degeneration in imaging studies (MRI, CT, plain radiography) underwent MRI-guided discography in order to determine possible pain provocation during puncture and contrast injection. An 0.23 T open configuration MRI device with interventional tools (Outlook Proview, Philips Medical Systems, MR Technologies, Finland) was used in procedural imaging and instrument guidance. An optical guidance tool was attached to the MRI compatible needle (Chiba-type MReye, Cook, Bloomington, IN). After initial disc puncture, 1-2 mL of gadolinium contrast (Magnevist, 469 mg/mL, Schering AG, Germany) saline mixture (1:8) was injected into the disc. Immediately after injection, sagittal FE T1 weighted images were obtained to verify the final position of the needle and formation of the MRI discogram. On nine patients, additional noncontrast sagittal fast spin echo (FSE) T1, FSE T2, and axial 3D T1 gradient echo imaging was performed before and after contrast media injection to obtain MRI discograms. Overall, 35 disc punctures were initialized and 34 MRI discograms were obtained. In all punctures, a positive or negative pain response was obtained. The average time for performing a procedure for three discs was 1 hour 25 minutes (minimum 45 minutes, maximum 2 hours, 15 minutes), and the average number of imaging sequences used for a puncturing one disc was 12. On one disc, the puncture failed and a discogram was not acquired. There was one complication (disc collapse) reported during follow-up. Our results show that MRI guidance in performing discography is accurate and relatively safe. It is a technically comparable method to CT-guidance or fluoroscopy.