Proton Density-weighted Turbo Spin Echo Research Articles

Evaluation of Refocus Flip Angle for Three-dimensional Proton Density-weighted Turbo Spin-echo Imaging in Cerebrovascular Black Blood MRA and Comparison with Three-dimensional Time-of-flight MRA

The three-dimensional time-of-flight (3D-TOF), which is currently the most common acquisition technique of intracranial magnetic resonance angiography (MRA), may result in poor branch visualization due to reduced blood flow velocity. Proton density-weighted volume isotropic turbo spin-echo acquisition (PDVISTA) is less susceptible to these factors and has been reported to be useful in assessing cerebral vasospasm after subarachnoid hemorrhage. In this study, we investigated the effect of refocus flip angle (RFA) for PDVISTA on the contrast between blood vessels and background brain tissue using flow velocity phantom and clinical images, assuming the usefulness of PDVISTA in daily clinical practice. The phantom experiments showed that the contrast ratio significantly improved with decreasing RFA; however, considering the signal-to-noise ratio, RFA 80° was determined as optimal for clinical use. Visual assessment was performed on PDVISTA (RFA 80°) and conventional 3D-TOF MRA clinical images, which suggested the superiority of PDVISTA over 3D-TOF in the delineation of peripheral branches of cerebral vessels. The results suggest that PDVISTA is useful not only for subarachnoid hemorrhage patients but also in daily clinical practice.

Clinical Magnetic Resonance Imaging of the Knee at 7 T: Optimization of Fat Suppression.

The aim of this study was to evaluate the efficiency and performance of different fat suppression techniques for clinical 7 T knee magnetic resonance imaging including the slice-selective gradient reversal (SSGR) technique. This article is an ethical board-approved prospective study with written informed consent from 8 volunteers (mean, 31 ± 4 years). It included fat phantom and knee magnetic resonance imaging at 3 T (Magnetom Skyra; Siemens Healthcare) and at 7 T (Achieva, Philips Healthcare). At 3 T, an axial proton density-weighted turbo spin echo sequence with spectral adiabatic inversion recovery (SPAIR) was acquired. At 7 T, a series of 5 proton density-weighted turbo spin echo sequences was acquired: (a) without fat suppression, (b) with spectral presaturation with inversion recovery (SPIR), (c) with SPAIR, (d) with SSGR, and (e) with the combination of SSGR + SPIR. Additional noise scans allowed pixelwise calculation of signal-to-noise ratio and contrast-to-noise ratio maps. Quantitative data at 7 T were compared with each other but not to 3 T. Two independent radiologists evaluated overall image quality, homogeneity and grade of fat suppression, and the delineation between 2 adjacent structures. Results were compared using Wilcoxon signed rank and paired sample t tests. Relative signal-to-noise ratios of fat demonstrated that the SPIR technique reduced the fat signal to 45% ± 5.4%; SPAIR, 18% ± 1.2%; SSGR, 14% ± 1.1%; and SSGR + SPIR, 11% ± 0.3%. Contrast-to-noise ratio showed superior contrast between muscle-fat (P < 0.001) and fluid-fat (P ≤ 0.001) for SSGR and SSGR + SPIR. The radiologists rated the overall image quality higher at 7 T than 3 T. The homogeneity and grade of fat suppression as well as the delineation between 2 different (adjacent) structures were rated best for SSGR + SPIR. At 7 T, fat saturation for clinical knee imaging using SSGR and the combination of SSGR + SPIR was superior compared with standard methods based on spectrally selective radiofrequency pulses.

An In Vitro Study of the Intervertebral Disc Structure Using 3 T Magnetic Resonance Imaging.

An in vitro magnetic resonance imaging (MRI) study. Investigate the potential of high-field MRI for producing higher quality images of the intervertebral disc (IVD) to better distinguish structural details. Higher spatial and contrast resolution are important advantages when imaging the complex tissue structures in the spine such as the IVDs. However, at present it is challenging to capture the substructural details in the IVD such as the lamellae. Three MRI sequences; two-dimensional proton-density-weighted Turbo-Spin-Echo (PD-TSE), 2D T2-weighted Turbo-Spin-Echo (T2W-TSE) with fat-saturation (FS), and 3D Spoiled-Gradient-Echo (3D-GE), were modified based on the image quality and scan duration. IVDs of three intact cadaveric lumbar-spines (T12-S1, Age 83-94 yr) were imaged using these optimized sequences. Thereafter each IVD was transversely sectioned and the exposed surfaces were photographed. Landmark observations from corresponding MRI slices and photographs were compared to confirm the MRI captured morphology. The image quality was evaluated using signal-to-noise ratio (SNR), and relative-contrast values. Finally, the underlying tissue structures, including specific pathological features, were qualitatively compared between the MR images and photographs. Observations from photographs and corresponding MRI slices matched well. The PD-TSE sequence had better overall SNR, but the relative contrast between the tissue types was relatively poor. The 3D-GE sequence had higher relative contrast between the IVD and bone, but not between annulus and nucleus regions. The T2W images provided the best relative contrast between the annulus and nucleus, however the standard deviations here were high. Structural details including fissures, vascular and granular tissue proliferation, and pathologies in the endplate region, were identifiable from the MR images obtained using the optimized sequences. The results demonstrate the potential of high-field MRI to capture the IVD structural details. Since the acquisition durations were within clinically acceptable levels, these methodological improvements have the potential to enhance clinical diagnostics. 4.

Evaluation of Focal Cervical Spinal Cord Lesions in Multiple Sclerosis: Comparison of White Matter-Suppressed T1 Inversion Recovery Sequence versus Conventional STIR and Proton Density-Weighted Turbo Spin-Echo Sequences.

Conventional MR imaging of the cervical spinal cord in MS is challenged by numerous artifacts and interreader variability in lesion counts. This study compares the relatively novel WM-suppressed T1 inversion recovery sequence with STIR and proton density-weighted TSE sequences in the evaluation of cervical cord lesions in patients with MS. Retrospective blinded analysis of cervical cord MR imaging examinations of 50 patients with MS was performed by 2 neuroradiologists. In each patient, the number of focal lesions and overall lesion conspicuity were measured in the STIR/proton density-weighted TSE and WM-suppressed T1 inversion recovery sequence groups. Independent side-by-side comparison was performed to categorize the discrepant lesions as either "definite" or "spurious." Lesion contrast ratio and edge sharpness were independently calculated in each sequence. Substantial interreader agreement was noted on the WM-suppressed T1 inversion recovery sequence (κ = 0.82) compared with STIR/proton density-weighted TSE (κ = 0.52). Average lesion conspicuity was better on the WM-suppressed T1 inversion recovery sequence (conspicuity of 3.1/5.0 versus 3.7/5.0, P < .01, in the WM-suppressed T1 inversion recovery sequence versus STIR/proton density-weighted TSE, respectively). Spurious lesions were more common on STIR/proton density-weighted TSE than on the WM-suppressed T1 inversion recovery sequence (23 and 30 versus 3 and 4 by readers 1 and 2, respectively; P < .01). More "definite" lesions were missed on STIR/proton density-weighted TSE compared with the WM-suppressed T1 inversion recovery sequence (37 and 38 versus 3 and 6 by readers 1 and 2, respectively). Lesion contrast ratio and edge sharpness were highest on the WM-suppressed T1 inversion recovery sequence. There is better interreader consistency in the lesion count on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density-weighted TSE sequences. The focal cord lesions are visualized with better conspicuity due to better contrast ratio and edge sharpness. There are fewer spurious lesions on the WM-suppressed T1 inversion recovery sequence compared with STIR/proton density-weighted TSE. The WM-suppressed T1 inversion recovery sequence could potentially be substituted for either STIR or proton density-weighted TSE sequences in routine clinical protocols.

Magnetic Resonance Imaging of the Temporomandibular Joint at 7.0 T Using High-Permittivity Dielectric Pads: A Feasibility Study.

The aims of this study were to show feasibility and to quantitatively and qualitatively evaluate the use of high-permittivity dielectric pads for imaging the temporomandibular joint (TMJ) at 7.0 T. This study is an institutional review board-approved study with written informed consent. Ten asymptomatic volunteers (20 TMJs) were magnetic resonance imaged using a 32-channel head coil at 7.0 T (Achieva; Philips Healthcare, the Netherlands) with and without high-permittivity dielectric pads consisting of barium titanate in deuterated suspension. Imaging protocol consisted of an oblique sagittal proton density-weighted turbo-spin echo sequence. For quantitative evaluation, B1 maps and voxelwise signal-to-noise ratio (SNR) maps were calculated. For qualitative evaluation, 2 readers assessed the visibility of anatomical structures of the TMJ and overall image quality on a 5-point Likert scale from 1 (excellent visibility) to 5 (not visible) in consensus. Quantitative and qualitative measurements were compared between images acquired with and without pads. Imaging the TMJ using dielectric pads was feasible in all volunteers. The quantitative analysis showed locally higher B1+ and higher SNR in the area covering the TMJ for the scans performed with dielectric pads compared with those without pads (SNR: mean [SD] pads, 12.38 [3.18]; mean [SD] no pads, 6.60 [0.72]). The qualitative analysis showed significantly better visibility and delineation of clinically relevant anatomical structures of the TMJ, including temporomandibular disc, bilaminar zone, mandibular fossa, mandibular condyle, and pterygoid muscle. In addition, observers judged overall image quality as better for images taken with pads compared with those taken without pads (mean [SD] pads, 1.40 [0.50]; mean [SD] no pads, 4.25 [0.78]). The application of high-permittivity dielectric pads improves the local B1+ field and thus the SNR, optimizing TMJ magnetic resonance imaging at 7.0 T.

Outcome Study of Real-time MR-guided Cervical Periradicular Injection Therapy in an Open 1.0 Tesla MRI System

To evaluate the accuracy, safety, and efficacy of cervical nerve root injection therapy using magnetic resonance guidance in an open 1.0 T MRI system. Between September 2009 and April 2012, a total of 21 patients (9 men, 12 women; mean age 47.1 ± 11.1 years) underwent MR-guided cervical periradicular injection for cervical radicular pain in an open 1.0 T system. An interactive proton density-weighted turbo spin echo (PDw TSE) sequence was used for real-time guidance of the MR-compatible 20-gauge injection needle. Clinical outcome was evaluated on a verbal numeric rating scale (VNRS) before injection therapy (baseline) and at 1 week and 1, 3, and 6 months during follow-up. All procedures were technically successful and there were no major complications. The mean preinterventional VNRS score was 7.42 and exhibited a statistically significant decrease (P < 0.001) at all follow-up time points: 3.86 ± 1.53 at 1 week, 3.21 ± 2.19 at 1 month, 2.58 ± 2.54 at 3 months, and 2.76 ± 2.63 at 6 months. At 6 months, 14.3 % of the patients reported complete resolution of radicular pain and 38.1 % each had either significant (4-8 VNRS score points) or mild (1-3 VNRS score points) relief of pain; 9.5 % experienced no pain relief. Magnetic resonance fluoroscopy-guided periradicular cervical spine injection is an accurate, safe, and efficacious treatment option for patients with cervical radicular pain. The technique may be a promising alternative to fluoroscopy- or CT-guided injections of the cervical spine, especially in young patients and in patients requiring repeat injections.

Traumatic injuries of thigh and calf muscles in athletes: role and clinical relevance of MR imaging and ultrasound

ObjectivesMagnetic resonance (MR) imaging and ultrasound have become valuable tools for evaluation of traumatic muscle injuries in athletes. Common athletic injuries include strain, contusion and avulsion, which are characterised by muscle fibre disruption, intramuscular haemorrhagic dissection, haematoma at the musculotendinous junction, and perifascial blood or haematoma.MethodsMR imaging may allow clinicians to predict the time required before athletes can return to competition and the risk of injury recurrence.ResultsFluid-sensitive MR sequences, e.g., fat-suppressed T2-weighted or proton density-weighted turbo spin echo (TSE), and short-tau inversion recovery (STIR) sequences are suitable for detecting oedematous changes in the musculotendinous unit, and for delineating intramuscular or perifascial fluid collections or haematoma. T1-weighted spin echo sequences are used to visualise atrophy and fatty infiltration and to differentiate between haemorrhage/haematoma and oedema. While ultrasound may play a role as an adjunctive imaging method, it is less accurate than MR images for assessing the extent of the injury and it cannot differentiate between new and old injuries.ConclusionsIn this pictorial review, imaging features of lower extremity muscle injuries including strain, contusion and avulsion are reviewed, focusing on MR and ultrasound imaging findings after initial injury and during follow-up, and their relevance in clinical practice is discussed.Teaching points• MR imaging may allow clinicians to predict time required before athletes can return to competition• Fluid-sensitive MR sequences are suitable for detecting oedematous changes in the muscles• T1-weighted sequences are used to differentiate between haemorrhage/haematoma and oedema.• Ultrasound can also be used but is less accurate than MR imaging for assessing the extent of the injury

MRI Versus Radiography of Acromioclavicular Joint Dislocation

Acromioclavicular joint injuries are usually diagnosed by clinical and radiographic assessment with the Rockwood classification, which is crucial for treatment planning. In view of the implementation of MRI for visualization of the acromioclavicular joint, the purpose of this study was to describe the MRI findings of acromioclavicular joint dislocation in comparison with the radiographic findings. Forty-four patients with suspected unilateral acromioclavicular joint dislocation after acute trauma were enrolled in this prospective study. All patients underwent digital radiography and 1-T MRI with a surface phased-array coil. MRI included coronal proton density-weighted turbo spin-echo and coronal 3D T1-weighted fast field-echo water-selective sequences. The Rockwood classification was used to assess acromioclavicular joint injuries at radiography and MRI. An adapted Rockwood classification was used for MRI evaluation of the acromioclavicular joint ligaments. The classifications of acromioclavicular joint dislocations diagnosed with radiography and MRI were compared. Among 44 patients with Rockwood type I-IV injuries on radiographs, classification on radiographs and MR images was concordant in 23 (52.2%) patients. At MRI, the injury was reclassified to a less severe type in 16 (36.4%) patients and to a more severe type in five (11.4%) patients. Compared with the findings according to the original Rockwood system, with the adapted system that included MRI findings, additional ligamentous lesions were found in 11 (25%) patients. In a considerable number of patients, the MRI findings change the Rockwood type determined with radiography. In addition to clinical assessment and radiography, MRI may yield important findings on ligaments that may influence management.

109 3T MRI of acute atherosclerotic plaque rupture and downstream embolic injury

<h3>Introduction</h3> Luminal stenosis is a poor predictor of the risk posed by any given atherosclerotic plaque, therefore current angiographic imaging techniques cannot reliably determine which patients are most likely to suffer future ischaemic events. However, MRI may be able to detect features of atherosclerotic plaque rupture that have been associated with an increased risk of recurrent atherothrombosis. <h3>Hypothesis</h3> 3T MRI of the carotid artery can identify atherosclerotic plaque rupture in patients presenting with TIA or minor stroke. <h3>Methods</h3> 81 patients with carotid artery disease were recruited; 41 presented acutely with TIA or minor stroke and 40 asymptomatic patients acted as the control group. Median time from symptom onset to MRI in the symptomatic group was 2.1 days (range 0.17–7.0). All patients underwent T1, T2 and proton density-weighted turbo spin echo MRI to 10 mm either side of the carotid. As part of a combined scan protocol, study participants then underwent diffusion-weighted imaging (DWI) and Fluid-Attenuated Inversion Recovery (FLAIR) imaging of the brain to assess acute and chronic injury, respectively. If physically able, patients underwent follow-up scanning a minimum of six weeks later. Plaques were graded according to the MRI modified American Heart Association (AHA) system by two independent reviewers blinded to the clinical status of the patient. Statistical analysis was performed using the Wilcoxon sign rank test and Fisher′s exact test to compare plaques, in addition to the Mann Whitney U test to compare cerebral injury. <h3>Results</h3> AHA type VI (ruptured) plaque was seen in 22/41(54%) in the symptomatic group vs 8/41(20%) in the asymptomatic group (p&lt;0.05), either due to intra-plaque haemorrhage (34% vs 18%, p=0.08; Abstract 109 figure 1A), surface rupture (24% vs 5%, p=0.03; Abstract 109 figure 1B), or luminal thrombus (7% vs 0%, p=0.24; Abstract 109 figure 1C). Of particular note, 17/30 (57%) cases of AHA VI (ruptured) plaque were seen to cause &lt;70% stenosis―the current cut-off for surgical treatment. At follow-up scanning a minimum of 6 weeks later, only two cases of AHA VI plaque showed evidence of full healing. Of the 41 patients in the acute group, evidence of cerebral injury on DWI imaging was seen in 32/41 patients; the median number of lesions per patient was 7 and the median total lesion volume was 10.62 ml (range 0–522 ml). No significant associations were noted between AHA plaque type and downstream cerebral injury, however the presence of plaque surface rupture independently predicted a higher number of DWI lesions, a higher total DWI burden at presentation, and higher total cerebral FLAIR signal at follow-up when compared to all other plaque types (p&lt;0.05). <h3>Conclusion</h3> Acute atherosclerotic plaque rupture can be visualised using 3T MRI. In particular, MRI can provide detailed information on plaque morphology that can predict downstream embolic injury, independent of the degree of luminal stenosis caused.

The regional distribution of T2-relaxation times in MR images of the substantia nigra and crus cerebri

When scanning the size of the substantia nigra (SN), for example in Parkinson's disease, it is important to precisely locate its true anatomic location. The hypointense areas on T2-weighted magnetic resonance images (T2w) at the level of the upper midbrain are usually labeled as the SN. Recent studies showed that the line of demarcation between the SN and the crus cerebri (CC) in T2w images seems not to be clear. The purpose of our study was to evaluate the depiction of the SN and the CC on calculated R2 maps by analyzing the regional distribution of T2 values in both regions. In 36 healthy subjects, triple echo turbo spin echo were obtained at 1.5 T and R2 maps calculated. Proton density-weighted turbo spin echo images (PDw) were used as reference. The CC and SN were manually traced on PDw sections (CCP and SNP) and also the hyperintense areas on the R2 maps, suggestive of the SN (DT2). The obtained volumes were evaluated in terms of total size, intersections size, and residual areas, as well as the corresponding T2 values. DT2 corresponded to anterolateral parts of the SNP and showed an extension to anteromedial part of the CC. The intersections between DT2 and CCP and DT2 and SNP presented both decreased but different T2 values (102 +/- 5 and 95 +/- 4 ms). An exact differentiation of the SN from the CC is not possible on the basis of T2w images but rather on the basis of the underlying calculated T2 values from the triple echo sequence.

The Evaluation of Articular Cartilage Lesions of the Knee With a 3-Tesla Magnet

This prospective study was performed to investigate whether 3-Tesla magnetic resonance imaging (MRI) provides an accurate assessment of the articular cartilage in clinical practice. Forty patients with persistent knee pain and suspected cartilage lesions underwent 3-T MRI shortly before arthroscopy with the following sequences: axial/coronal/sagittal proton density-weighted turbo spin echo with spectral fat suppression, axial/sagittal 3-dimensional T1-weighted gradient echo with selective water excitation, and axial T2-weighted gradient echo (Intera 3.0T; Philips Medical Systems, Best, The Netherlands). Knee cartilage surfaces were divided into 6 regions; lesions detected on MRI were classified into stages I to IV and compared with the arthroscopic grading. For the 240 cartilage surfaces evaluated, the sensitivities, specificities, positive predictive values, and negative predictive values of 3-T MRI were 74%, 95%, 74%, and 95%, respectively, for the detection of grade IV lesions; 63%, 90%, 60%, and 91%, respectively, for grade III lesions; 62%, 90%, 57%, and 92%, respectively, for grade II lesions; and 29%, 95%, 39%, and 92%, respectively, for grade I lesions. In these preliminary clinical studies 3-T MRI provided convincing visualization of the hyaline cartilage with comparatively good diagnostic values. Nonetheless, it must be pointed out that the positive predictive values were low for all grades of lesions. Thus, when 3-T MRI suggests a cartilage defect, the probability that the arthroscopic finding corresponds exactly to the MRI result is between 39% and 74%. Therefore, the value of arthroscopy for a detailed assessment and grading of a cartilage disorder with regard to definitive planning of a therapeutic procedure cannot be replaced by 3-T MRI. Level I, testing of previously developed diagnostic criteria in a series of consecutive patients with universally applied gold standard.

Value of fat-suppressed proton-density-weighted turbo spin-echo sequences in detecting meniscal lesions: comparison with arthroscopy

To evaluate fat-suppressed (FS) proton-density-weighted (PDw) turbo spin-echo (TSE) magnetic resonance imaging (MRI) compared to arthroscopy in the detection of meniscal lesions. In a prospective study, 31 knee joints were imaged on a 1.5T MR scanner before arthroscopy using the following sequences: (a) coronal and sagittal FS-PDw TSE (TR/TE: 4009/15 ms); (b) coronal T1w SE (TR/TE: 722/20 ms), and sagittal PDw TSE (TR/TE: 3800/15 ms). Other imaging parameters were: slice thickness 3 mm, FOV 160 mm, matrix 256 x 256. A total of 186 meniscal regions (62 menisci; anterior horn, body, posterior horn) were evaluated. Standard of reference was arthroscopy. Sensitivity, specificity, negative predictive value (npv), positive predictive value (ppv), and accuracy were calculated. Arthroscopically, meniscal lesions were detected in 55/186 segments (35 medial and 20 lateral meniscal lesions). Sensitivity, specificity, npv, ppv, and accuracy for combination of coronal and sagittal FS PDw TSE were 91.4%, 98.3%, 95%, 97%, and 93.5% for the medial meniscus, and 90%, 98.6%, 97.3%, 94.7%, and 96.8% for the lateral. The results were comparable to the combination of coronal T1w SE and sagittal PDw TSE for the medial (88.6%, 98.3%, 93.4%, 96.9%, 91.4%) and the lateral (90%, 95.9%, 97.2%, 85.7%, 92.5%) meniscus. FS PDw TSE-MR sequences are an excellent alternative for the detection of meniscal lesions in comparison with diagnostic arthroscopy.

Value of fat-suppressed PD-weighted TSE-sequences for detection of anterior and posterior cruciate ligament lesions—Comparison to arthroscopy

Objective To evaluate fat-suppressed (FS) proton-density-weighted (PDw) turbo spin-echo (TSE) magnetic resonance imaging for the detection of anterior and posterior cruciate ligament lesions in comparison to arthroscopy. Materials and methods In a prospective study 31 knee joints were imaged on a 1.5 T MR scanner (Vision ®, Siemens, Erlangen) prior to arthroscopy using following sequences: (a) sagittal FS-PDw/T2w TSE (TR/TE: 4009/15/105 ms); (b) sagittal PDw/T2w TSE (TR/TE:3800/15/105 ms). Further imaging parameters: slice thickness 3 mm, FOV 160 mm, matrix 256 × 256. A total of 62 anterior and posterior cruciate ligaments (ACL/PCL) were evaluated, standard of reference was arthroscopy. Sensitivity, specificity, positive (ppv) and negative predictive value (npv) and accuracy were calculated. Results Twenty-one cruciate ligament ruptures were detected in arthroscopy, 19 ACL- and 2 PCL-ruptures (on MRI 34/124, 25/62 ACL, 9/62 PCL lesions). For all four sequences in the 31 patients with arthroscopic correlation sensitivity, specificity, ppv, npv and accuracy were 86%, 98%, 95%, 93% and 94% for detection of tears, and 84%, 100%, 100%, 80% and 90% for ACL-ruptures respectively. The two PCL-ruptures were true positive in all sequences, one intact PCL was diagnosed as torn (false positive). Conclusions Fat-suppressed PDw/T2w TSE-MR sequences are comparable to PDw TSE sequences for the detection of ACL/PCL-lesions.