Dual Echo Steady State Sequences Research Articles

3T MRI of wrist ligaments and TFCC using true plane oblique 3D T2 Dual Echo Steady State (DESS) - a study of diagnostic accuracy.

This study was designed to assess the accuracy of unenhanced 3T MRI supplemented with dedicated true plane reformats of 3D T2 Dual Echo Steady State (DESS), in assessing tears of scapholunate, lunotriquetral ligaments and triangular fibrocartilage complex, using arthroscopy as gold-standard. In a retrospective cohort review, patients who underwent wrist arthroscopy and MRI over 2 years (n=46) were identified. Dedicated axial and coronal reformats were obtained from 3D T2 DESS sequence for assessing intrinsic ligaments and triangular fibrocartilage (TFCC). At arthroscopy, tears were classified using Geissler's classification and compared to MRI findings. The sensitivity of unenhanced 3T MRI in detecting scapholunate ligament tears was 87%, specificity was 90% and negative predictive value of 93%. The lunate triquetral ligament was assessed with a high specificity (97%) and negative predictive value (93%), sensitivity was 63%. TFCC tears were assessed with a sensitivity of 100%. The overall diagnostic accuracy of unenhanced 3T MRI of wrist in detecting ligament tears was 91%. 3T wrist MRI with dedicated reformats from 3D T2 DESS has a high diagnostic accuracy in assessing acute intrinsic ligament and TFCC injuries. High strength 3T MRI with good technical quality isotropic 3D T2 DESS is critical for accurate wrist ligament assessment. Negative predictive values of 3T MRI of 95% can lead to reduced need for diagnostic arthroscopy of the wrist. This study assesses the diagnostic performance of unenhanced 3T MRI with 3D T2 DESS in assessing traumatic wrist ligament tears. The accuracy of T2 DESS in wrist imaging has not been previously reported.

Assessing the scapholunate and lunotriquetral interosseous ligament in MR arthrography: Diagnostic advantages of paraxial reformatting

PurposeThe scapholunate (SLIL) and lunotriquetral interosseous ligament (LTIL) function as the main stabilizers of the proximal carpal row. Even with MR arthrography, component assessability is often limited in orthogonal standard planes due to their horseshoe-like shape and resulting partial volume effects. This study aims to investigate the diagnostic value of reformatting isotropic 3D sequences with respect to the anatomical orientation of the intrinsic carpal ligaments. MethodIn 110 MR arthrograms of the wrist, we investigated the diagnostic accuracy of two radiologists (R1/R2) for SLIL and LTIL injuries in orthogonal standard planes vs. ancillary angulated reformatting of isotropic 3D dual echo steady state sequence. Component assessability and diagnostic confidence were compared between datasets. ResultsThe addition of paraxial reformations improved diagnostic accuracy for lesions of the palmar (R1: 0.87 vs. 0.93; R2: 0.86 vs. 0.93; all p < 0.05) and dorsal LTIL (R1: 0.85 vs. 0.93; R2: 0.82 vs. 0.90; all p < 0.05). No significant increase in accuracy could be ascertained for palmar (R1: 0.92 vs. 0.94, p = 0.50; R2: 0.86 vs. 0.92, p = 0.07) and dorsal (R1: 0.95 vs. 0.95, p = 1.00; R2: 0.90 vs. 0.94, p = 0.29) lesions of the SLIL. Interrater reliability was almost perfect with and without angulated planes for SLIL (κ = 0.88 vs. 0.82) and LTIL assessment (κ = 0.88 vs. 0.86). For the LTIL, observer confidence and component assessability were superior with anatomical reformations available (all p < 0.05). ConclusionsIn contrast to SLIL injuries, diagnosis of LTIL lesions benefits from ancillary paraxial reformations of 3D sequences in MR wrist arthrography.

In-vivo three-dimensional MR imaging of the intact anterior cruciate ligament shows a variable insertion pattern of the femoral and tibial footprints.

Failure to reconstruct the natural footprints of the ruptured anterior cruciate ligament (ACL) may lead to premature graft-failure. Therefore, precise analyses of insertion site anatomy and inter-individual variations of the morphology of the ACL are highly important to facilitate optimal individualized graft placement. Therefore, the purpose of this study was to analyze the inter-individual variation of the morphology of the femoral and tibial ACL footprints. Thirty subjects with an intact ACL were included in this study for MR imaging of their knee joint. A three-dimensional (3D) dual-echo steady-state sequence with near 0.8mm isotropic resolution was acquired on a 3T system with a 15-channel knee-coil. The ACL was subsequently manually segmented using dedicated medical imaging software (VitreaAdvanced®, Vital Images). The lengths and widths of the footprints were measured after reconstructing an axial oblique (tibial footprint) or coronal oblique (femoral footprint) section at the bone-ligament junction and descriptive analysis was conducted to describe morphology orientation of the footprint. The femoral footprint measured on average 14mm ± 2mm (range 8-19mm) in length and 5mm ± 1mm (range 3-8mm) in width. The mean value of the tibial footprint measured 10mm ± 2mm (range 5-14mm) in length and 7mm ± 2mm (range 5-13mm) in width. Descriptive analysis showed a stretched, ribbon-like appearance of the femoral footprint, while the tibial footprint revealed larger variability, stretching from anterolateral to posteromedial around the anterior horn of the lateral meniscus. 3D imaging of the ACL footprints reveals a distinct difference in insertion site morphology and fiber bundle orientation between the femoral and tibial footprint. This questions the concept of strict anatomical separation of the ACL into an anteromedial and posterolateral bundle.

Comparison of 3D MR imaging sequences in knee articular cartilage at 1.5 T

Purpose: To compare 3D high-resolution MRI sequences in term of contrast, Signal to Noise Ratio (SNR), artefacts and cartilage thickness in knee articular cartilage at 1.5 T. Materials and Methods: Fourteen healthy volunteers and seven patients underwent articular knee cartilage exam. The 3D sequences were VOLUME Imaging with Body Enhancement (VIBE), True Fast Imaging with Steady-state Precession (TRUEFISP), Dual Echo Steady State (DESS), Multi Echo Data Image Combination (MEDIC) and Sampling Perfection with Application optimized Contrasts using different flip angle Evolutions (SPACE). For all 3D sequences, we measured contrast ratio between cartilage-bone and cartilage-meniscus, SNR and cartilage thickness. In addition, we quantified magnetic susceptibility and flow artifacts. Statistical analyses were performed using the t-test and P<0.005 was considered statistically significant. Results: Statistical results were significantly different (p>0.05). MEDIC and VIBE sequences showed the best contrast ratio between cartilage-meniscus (0.40 ± 0.14, p=0.000) and cartilage-bone (0.75 ± 0.4, p=0.022), respectively. TRUEFISP sequence showed the highest SNR (28.04 ± 14.05, p=0.000) whereas DESS sequence showed the lowest SNR (11.62 ± 3.99, p=0.000). VIBE sequence provided the highest cartilage thickness measurement compared to the remaining 3D sequences (2.0 ± 0.4 cm, IRR=75.33%, ICC=0.96). The quantification of magnetic susceptibility and flow artifacts revealed that TRUEFISP (IRR=59%, ICC=0.92) and SPACE (IRR=59%, ICC=0.96) sequences presented the highest artifacts compared to the others sequences. Conclusion: 3D high-resolution sequences provide knee articular cartilage imaging with high image quality in relatively short acquisition time. MEDIC and VIBE sequences showed the best contrast and the lowest magnetic susceptibility and flow artifacts, TRUEFISP and SPACE sequence showed the highest SNR but they are more sensitive to artifacts, DESS sequence showed medium contrast and VIBE sequence provided the highest cartilage thickness.

Standardized quantitative measurements of wrist cartilage in healthy humans using 3T magnetic resonance imaging.

To quantify the wrist cartilage cross-sectional area in humans from a 3D magnetic resonance imaging (MRI) dataset and to assess the corresponding reproducibility. The study was conducted in 14 healthy volunteers (6 females and 8 males) between 30 and 58 years old and devoid of articular pain. Subjects were asked to lie down in the supine position with the right hand positioned above the pelvic region on top of a home-built rigid platform attached to the scanner bed. The wrist was wrapped with a flexible surface coil. MRI investigations were performed at 3T (Verio-Siemens) using volume interpolated breath hold examination (VIBE) and dual echo steady state (DESS) MRI sequences. Cartilage cross sectional area (CSA) was measured on a slice of interest selected from a 3D dataset of the entire carpus and metacarpal-phalangeal areas on the basis of anatomical criteria using conventional image processing radiology software. Cartilage cross-sectional areas between opposite bones in the carpal region were manually selected and quantified using a thresholding method. Cartilage CSA measurements performed on a selected predefined slice were 292.4 ± 39 mm(2) using the VIBE sequence and slightly lower, 270.4 ± 50.6 mm(2), with the DESS sequence. The inter (14.1%) and intra (2.4%) subject variability was similar for both MRI methods. The coefficients of variation computed for the repeated measurements were also comparable for the VIBE (2.4%) and the DESS (4.8%) sequences. The carpus length averaged over the group was 37.5 ± 2.8 mm with a 7.45% between-subjects coefficient of variation. Of note, wrist cartilage CSA measured with either the VIBE or the DESS sequences was linearly related to the carpal bone length. The variability between subjects was significantly reduced to 8.4% when the CSA was normalized with respect to the carpal bone length. The ratio between wrist cartilage CSA and carpal bone length is a highly reproducible standardized measurement which normalizes the natural diversity between individuals.

Pre-operative evaluation of patients undergoing knee articular cartilage repair: MRI 3D thickness maps derived from a validated, automated segmentation platform - initial results

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S202 disease using backscattered electron imaging of embedded tissue blocks. These structures are formed by the extrusion of mineralisable matrix through microcracks in the articular calcified cartilage. Recently using micro-computed tomography, we identified similar structures in a human femoral head obtained from a patient with osteoarthropathy of alkaptonuria who underwent arthroplasty to alleviate severe joint pain. These protrusions are more densely mineralised than bone and mineralised cartilage. They protrude so far within articular cartilage that they are at risk of breaking off to generate small, hard, sharp edged fragments which might act as abrasive cutting and grinding particles that could contribute to the mechanical destruction of cartilage. The aim of this study was to determine if these protrusions could be identified by MRI. Methods: Femoral head and neck samples were fixed in formalin solution and then transferred to 70% ethanol. They were scanned in a Trio 3 Tesla MRI scanner using a wrist coil. Isotropic voxel data were acquired using a range of different modalities including dual echo steady state (DESS) sequences. Results: We found that the hypermineralised protrusions were visible, silhouetted against the signal-rich articular cartilage on the DESS sequences at resolutions of 0.5mm (TR1⁄416.3ms; TE1⁄44.7ms; NEX1⁄41; 320x320x160 voxels) and 0.23mm (TR1⁄418.2; TE1⁄45.64ms; NEX1⁄45; 512x512x240 voxels). Using MRI at both these resolutions, wewere able to detect protrusions similar to those previously identified by microtomography in the femoral head of the patient with alkaptonuria. Furthermore we were able to detect the protrusions in a femoral head from a patient with osteoarthritis unrelated to alkaptonuria. Conclusions: The results of this study demonstrate that hypermineralised subchondral protrusions are present in human femoral heads in the rare disease alkaptonuria but also in osteoarthritis. Although the MR images showing protrusions were recorded postoperatively from femoral heads, the resolution at which they could be detected raises the prospect of finding them and monitoring their progression in situ with MRI. 382 PRE-OPERATIVE EVALUATION OF PATIENTS UNDERGOING KNEE ARTICULAR CARTILAGE REPAIR: MRI 3D THICKNESS MAPS DERIVED FROM A VALIDATED, AUTOMATED SEGMENTATION PLATFORM INITIAL RESULTS J.M. Farber y, J. Tamez-Pena y, S. Totterman y, J. Larkin z, B. Holladay z, F. Heis z. yQmetrics, Rochester, NY, USA; zCommonwealth Orthopaedic Ctr.s, Edgewood, KY, USA Purpose: To present a robust, automatedMR imagingmethodology that generates 3D articular cartilage (AC) thickness maps of the knee, and which delineates the size and location of AC defects, as well as the thickness and integrity of the defect walls, to serve as an accurate preoperative guide for AC defect repair. Methods: A sagittal 3D FSE FS sequence (TR-2300; TE-20) is obtained on all patients undergoing routine 1.5TMRI (Optima 450W, GE,Milwaukee) of the knee at our facility. These 3D FSE data sets are sent to a dedicated work station (Qmetrics Technologies, Rochester, NY), which automatically segments the knee AC. The segmented images are then reviewed bya radiologist for accurate fit with the source images. If necessary, edits can be made on the dedicated work station to ensure proper segmentation. Themethodology of this process has been validated (1). From the segmented data sets, 3DAC thicknessmaps are generated automatically. These thickness maps are then reviewed by the radiologist for accuracy, compared to the source images. In patients who underwent subsequent AC defect repair, intra operative measurements were obtained of the AC defect size and location. The intra operative, gold standard data were then compared to the prospectively obtained thickness maps to assess accuracy of lesion size and location. Results: Initial results (N1⁄412) validate the accuracy of the thickness maps in delineating AC defect size and location (Fig. 1). In addition, the thickness maps accurately delineated the integrity of the AC defect walls, allowing for accurate surgical debridement and pre-operative planning for graft material allocation. In no case did the thickness map miss an AC defect of the segmented region. Conclusions: In our initial experience, 3D thickness maps of knee AC defects accurately detect and delineate AC defects, and are a clinically useful pre-operative tool. In addition, these automatically generated maps, which can be displayed along any axis, are useful in patientphysician discussions when discussing treatment options. Further work, specifically testing a larger N, is required to obtain statistical validation. Further work also will include also the use of T2 maps, with the thickness maps as a template (Image Available), to further assess the health of the AC surrounding a defect (2), to optimize further intra operative wall debridement and graft material allocation. Ă

Part 1

Development of a dual-tuned proton/sodium radiofrequency (RF) coil for magnetic resonance imaging (MRI) of the rabbit spine and quantification of sodium concentration in intervertebral discs. To develop the dual-tuned proton/sodium MRI of rabbit lumbar spine to investigate proteoglycan matrix content and intervertebral disc degeneration (IDD). IDD is a common chronic condition that may lead to back pain, limited activity, and disability. Early-stage IDD involves the loss of proteoglycan matrix and water content in the disc. Sodium MRI is a promising noninvasive technique for quantitative measurement of proteoglycan changes associated with IDD. The combined structural (proton) and biochemical (sodium) MRI facilitates the investigation of morphological and molecular changes associated with degeneration of discs. Multichannel dual-tuned proton/sodium transceiver RF coil of the rabbit spine was developed and optimized at 3T human scanner-8 channels allocated for the sodium coil and 4 channels for the proton coil. High-resolution anatomy proton images of the discs were acquired using turbo spin echo and dual echo steady state sequence. Sodium concentration of the discs was quantified from sodium magnetic resonance (MR) images that were calibrated for signal attenuation because of RF field inhomogeneity, sodium MR relaxation times, and disc thickness. Twelve rabbits (~1-yr old, female, 5.2 ± 0.4 kg) were used for measuring disc sodium concentration. High-resolution in vivo proton and sodium MR images of rabbit discs (≤2-mm thickness) were successfully obtained using an in-house dual-tuned proton/sodium RF coil at 3T. The total acquisition time for each set of images was approximately 40 minutes. Sodium concentration of normal rabbit lumbar discs was measured at 269.7 ± 6.3 mM, and this measurement was highly reproducible, with 5.3% of coefficient of variation. Sodium concentrations of rabbit lumbar discs were reliably measured using our newly developed dual-tuned multichannel proton/sodium RF coil at 3T.

Semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts of the knee at 3T MRI: A comparison between intermediate-weighted fat-suppressed spin echo and Dual Echo Steady State sequences

BackgroundChoice of appropriate MR pulse sequence is important for any research studies using imaging-derived data. The aim of this study was to compare semiquantitative assessment of subchondral bone marrow edema-like lesions and subchondral cysts using intermediate-weighted (IW) fat-suppressed (fs) spin echo and Dual Echo Steady State (DESS) sequences on 3 T MRI.MethodsIncluded were 201 subjects aged 35-65 with frequent knee pain. 3T MRI was performed with the same sequence protocol as in the Osteoarthritis Initiative (OAI). In a primary reading subchondral bone marrow edema-like lesions were assessed according to the WORMS system. Two hundred subregions with such lesions were randomly chosen. The extent of subchondral bone marrow edema-like lesions was re-evaluated separately using sagittal IW fs and DESS sequences according to WORMS. Lesion size and confidence of the differentiation between subchondral bone marrow edema-like lesions and subchondral cysts located within or adjacent to them was rated from 0 to 3. Wilcoxon signed-rank tests and chi-square statistics were used to examine differences between the two sequences.ResultsOf 200 subchondral bone marrow edema-like lesions detected by IW fs sequence, 93 lesions (46.5%) were not depicted by the DESS sequence. The IW fs sequence depicted subchondral bone marrow edema-like lesions to a larger extent than DESS (p < 0.0001), and the opposite was true for subchondral cysts. Confidence scores for differentiation of the two types of lesions were not significantly different between the two sequences.ConclusionsIn direct comparison the IW fs sequence depicts more subchondral bone marrow edema-like lesions and better demonstrate the extent of their maximum size. The DESS sequence helps in the differentiation of subchondral bone marrow edema-like lesions and subchondral cysts. The IW fs sequence should be used for determination of lesion extent whenever the size of subchondral bone marrow edema-like lesions is the focus of attention.

Cartilage imaging: motivation, techniques, current and future significance

Cartilage repair techniques and pharmacological therapies are currently areas of major clinical interest and research, in particular to prevent and treat osteoarthritis. MR imaging-based techniques to visualize cartilage are prerequisites to guide and monitor these therapies. In this review article, standard MR imaging sequences are described, including proton density-weighted fast spin echo, spoiled gradient echo and dual echo steady state sequences. In addition, new sequences that have been developed and are currently being investigated are presented, including driven equilibrium Fourier transform and steady-state free precession-based imaging. Using high-field MR imaging at 3.0-T, visualization of cartilage and the related pathology has been improved. Volumetric quantitative cartilage MR imaging was developed as a tool to monitor the progression of osteoarthritis and to evaluate new pharmacological cartilage protective therapies. The most exciting developments, however, are in the field of cartilage matrix assessment with quantitative dGEMRIC, T2 and T1rho mapping techniques. These techniques aim at detecting cartilage damage at a stage when changes are potentially still reversible, before cartilage tissue is lost. There is currently substantial interest in these techniques from rheumatologists and orthopedists; radiologists therefore need to keep up with these developments.