Meniscal tear configurations: categorization with 3D isotropic turbo spin-echo MRI compared with conventional MRI at 3 T. AJR Am J Roentgenol. 2012;198:W173-W180. [PMID: 22268208 DOI: 10.2214/ajr.11.6979]

Meniscal Root Tears: An Update Focused on Preoperative and Postoperative MRI Findings

Meniscal root tears represent radial tears or avulsions of the meniscal cartilage at the tibial attachment site that profoundly affect meniscal biomechanics and kinematics. Meniscal root tears have the functional effect of a total meniscectomy and can lead to rapid degenerative change with development of early knee osteoarthritis (OA). A growing range of arthroscopic surgical techniques have been developed to repair meniscal root tears with the aim of restoring joint kinematics and contact pressures and delaying the development of OA. With increased understanding of the anatomy and biomechanics of the meniscal root, meniscal root injury repair has become the treatment of choice in knees with nonadvanced OA. This article reviews the anatomy and biomechanics of the meniscal roots, clinical and imaging diagnostic criteria of meniscal root tears, correlation between arthroscopy and MRI in the diagnosis and classification of meniscal root tears, and expected and abnormal MRI findings after meniscal root repair. Familiarity with MRI signs and classifications of meniscal root tears, as well as with root repair surgical techniques, can aid radiologists in correctly reporting preoperative and postoperative MRI findings.

Magnetic resonance imaging in the evaluation of cervical foraminal stenosis: comparison of 3D T2 SPACE with sagittal oblique 2D T2 TSE

OBJECTIVE

The oblique orientation of the cervical neural foramina challenges the implementation of a short MRI protocol with concurrent excellent visualization of the spine. While sagittal oblique T2-weighted sequences permit good evaluation of the cervical neuroforamina, all segments may not be equally well depicted on a single sequence and conspicuity of foraminal stenosis may be limited. 3D T2-weighted sequences can be reformatted in arbitrary planes, including the sagittal oblique. We set out to compare 3D T2w SPACE sequences with sagittal oblique reformations and sagittal oblique 2D T2w TSE sequences for the evaluation of cervical foraminal visibility and stenosis.

MATERIALS AND METHODS

Sixty consecutive patients who underwent MRI of the cervical spine with sagittal oblique 2D T2w TSE and 3D T2w SPACE sequences were included. Image homogeneity of the sequences was evaluated. Imaging sets were assessed for structure visibility and foraminal stenosis by two independent readers. Results of the sequences were compared by Wilcoxon matched-pairs tests. Interreader agreement was evaluated by weighted κ.

RESULTS

Visibility of most structures was rated good to excellent on both sequences (mean visibility scores ≥ 4.5 of 5), though neuroforaminal contents were better seen on sagittal oblique T2w TSE (mean scores 4.1-4.6 vs. 3.1-4.1 on 3D T2w SPACE, p < 0.01). Stenosis grades were comparable between sequences (mean 1.1-2.6 of 4), with slightly higher values for 3D T2w SPACE at some levels (difference ≤ 0.3 points).

CONCLUSION

3D T2w SPACE is comparable with sagittal oblique 2D T2w TSE in the evaluation of cervical neural foramina.

Visualization of meniscus with 3D axial reconstructions

PURPOSE

To visualize the meniscus of the knee joint in the axial plane and identify injuries that cannot be visualized using conventional sequences.

METHODS

Two hundred and two subjects underwent an improvised 3-Dimensional Proton Density Fat Saturation (3D-PD FS) Magnetic Resonance (MR) sequence on their meniscus. The transverse images were reconstructed and examined. Fifty-three of the subjects had a healthy meniscus and their images were used as part of a qualitative evaluation to verify that all parts of the meniscus were properly visualized. The evaluation was based on a four-level scale indicating the visualization of meniscal parts. The same evaluation was also performed on the 149 subjects with meniscal pathologies. Another qualitative evaluation was performed on all subjects concerning five image characteristics based on a five-level scale. Finally, images from 20 patients with meniscal pathologies were compared with arthroscopic images visualizing meniscal tears.

RESULTS

In all subjects, all parts of the meniscus were clearly visualized. The axial reformats provided ideal imaging of the meniscus, yielding high total image quality, satisfactory smoothing and sharpening, fewer artifacts, and successful fat saturation. The findings of the MR images from the 20 subjects with meniscal pathologies, concerning the topography of meniscal tears coincided at 100% with their arthroscopic findings.

CONCLUSION

The use of the improvised 3D-PD FS sequence provides the possibility of axial reconstruction with a better depiction of the meniscus. These images can accurately illustrate the range of the meniscus and any meniscal tears along with their exact location with high image quality.

Assessment of the Usefulness of Image Reconstruction in the Oblique and Double-oblique Sagittal Planes for Magnetic Resonance Imaging of the Canine Cranial Cruciate Ligament

Introduction

The aim of the study was to determine the quality and significance of the magnetic resonance image of the canine knee after reconstruction in the oblique and double-oblique sagittal plane. This reconstruction and 3D images are rarely used in common protocols due to the longer study time they require. The study aimed to demonstrate significance for such diagnostic images in specific sequences in order to stimulate consideration of their more frequent use in diagnosis of diseases of the cruciate ligament in dogs.

Material and Methods

All tests were carried out using an open magnetic resonance tomography scanner with magnetic field induction. The images obtained from the 30 canine patients examined were reconstructed and evaluated by independent appraisers. Statistical analysis was performed.

Results

The study showed that MRI of the stifle joint using 3D sequences provides higher quality images of the cranial cruciate ligament in dogs. The results of the statistical analysis showed that multi-faceted reconstruction allows the secondary determination of the oblique imaging planes and obtains images of adequate quality.

Conclusion

It can be concluded that multi-faceted reconstruction facilitates the secondary determination of oblique imaging planes. This reconstruction additionally makes images available of better quality compared to the 2D sequence.

Evaluation of optimised 3D turbo spin echo and gradient echo MR pulse sequences of the knee at 3T and 1.5T

INTRODUCTION

To investigate the impact of parameter optimisation for novel three-dimensional 3D sequences at 1.5T and 3T on resultant image quality.

METHODS

Following institutional review board approval and acquisition of informed consent, MR phantom and knee joint imaging on healthy volunteers (n = 16) was performed with 1.5 and 3T MRI scanners, respectively incorporating 8- and 15-channel phased array knee radiofrequency coils. The MR phantom and healthy volunteers were prospectively scanned over a six-week period. Acquired sequences included standard two-dimensional (2D) turbo spin echo (TSE) and novel three-dimensional (3D) TSE PDW (SPACE) both with and without fat-suppression, and T2∗W gradient echo (TrueFISP) sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured for knee anatomical structures. Two musculoskeletal radiologists evaluated anatomical structure visualisation and image quality. Quantitative and qualitative findings were investigated for differences using Friedman tests. Inter- and intra-observer agreements were determined with κ statistics.

RESULTS

Phantom and healthy volunteer images revealed higher SNR for sequences acquired at 3T (p-value <0.05). Generally, the qualitative findings ranked images acquired at 3T higher than corresponding images acquired at 1.5T (p < 0.05). 3D image data sets demonstrated less sensitivity to partial volume averaging artefact (PVA) compared to 2D sequences. Inter- and intra-observer agreements for evaluation across all sequences ranged from 0.61 to 0.79 and 0.71 to 0.92, respectively.

CONCLUSION

Both 2D and 3D images demonstrated higher image quality at 3T than at 1.5T. Optimised 3D sequences performed better than the standard 2D PDW TSE sequence for contrast resolution between cartilage and joint fluid, with reduced PVA artefact.

IMPLICATIONS FOR PRACTICE

With rapid advances in MRI scanner technology, including hardware and software, the optimisation of 3D MR pulse sequences to reduce scan time while maintaining image quality, will improve diagnostic accuracy and patient management in musculoskeletal MRI.

3D-MRI combined with signal-to-noise ratio measurement can improve the diagnostic accuracy and sensitivity in evaluating meniscal healing status after meniscal repair

PURPOSE

This study compared the diagnostic accuracy of second-look arthroscopy, clinical assessment, and magnetic resonance imaging (MRI) in evaluating meniscal healing following repair. To explore the application of 3D-MRI sequences with signal-to-noise ratio (SNR) measurements and the analysis of sensitivity and accuracy in evaluating meniscal healing status after meniscal repair.

METHODS

This study included 75 patients (75 menisci; mean age, 25.4 ± 6.6 years) who underwent arthroscopic meniscal repair (medial menisci, 45; and lateral menisci, 29). Follow-up evaluation included clinical assessment, magnetic resonance imaging (MRI), and second-look arthroscopy (mean follow-up, 10.2 ± 3.4 months). The criteria defined for unhealed menisci were: on arthroscopy, presence of cleft; on clinical assessment, presence of joint-line tenderness, swelling, locking, or positive McMurray test; on MRI, grade III signal intensity at the site of repair. Finally, the SNR on 3D-MRI of the healed and the unhealed groups were compared.

RESULTS

On second-look arthroscopy, 68 (90.7%) menisci were found to be completely healed. With the arthroscopic healing rate as the standard, the clinical healing rate was 69.3% (63 menisci) [sensitivity, 85.7%; specificity, 75.0%; accuracy, 76.0%; positive predictive value (PPV), 26.1%; negative predictive value (NPV), 98.1%]. Similarly, the sensitivity, specificity, accuracy, PPV and NPV, respectively, for MRI in four sequences were as follows: 2D-T2W-Sag: 71.4, 79.4, 78.7, 26.3, and 96.4%; 2D-T2W-Cor: 71.4, 82.4, 81.3, 29.4, and 96.6%; 3D-PDW-Sag: 100.0, 50.0, 54.7, 17.1, and 100.0%; 3D-PDW-Cor: 100.0, 58.8, 62.7, 20.0, and 100.0%. The mean SNRs of the healed group (3D-PDW-Sag, 66.7 ± 11.9; 3D-PDW-Cor, 63.9 ± 12.4) were significantly lesser than that of the unhealed group (3D-PDW-Sag, 89.2 ± 9.6; 3D-PDW-Cor, 82.2 ± 18.5) (P < 0.05). Identifying grade 3 meniscal damage on 3D-PDW images prior to applying the different SNR cut-off points revealed SNR values 80 in the sagittal plane and 70 in the coronal plane as having better diagnostic accuracy and sensitivity. The clinical relevance of the study was that 3D-MRI combined with SNR measurement may be a noninvasive and accurate method of assessment clinically, and a reliable alternative to second-look arthroscopy.

LEVEL OF EVIDENCE

III.

Diagnostic performance of shoulder magnetic resonance arthrography for labral tears having surgery as reference: comparison of high-resolution isotropic 3D sequence (THRIVE) with standard protocol

PURPOSE

To compare the diagnostic performance of T1 high-resolution isotropic volume excitation (THRIVE) sequence with that of a standard protocol for direct shoulder magnetic resonance arthrography (MRA) for the diagnosis of superior labral anterior-to-posterior (SLAP) and Bankart lesions, using arthroscopy findings as a reference standard.

MATERIALS AND METHODS

We retrospectively studied 84 patients who underwent direct shoulder 3T MRA using THRIVE and two-dimensional three-plane proton-density fat-suppressed (2D-PD-FS) sequences. One reviewer evaluated the contrast-to-noise ratio (CNR) as a quantitative image quality. Other two reviewers independently evaluated the subjective image noise, image sharpness, and radiologic diagnosis as qualitative image quality. Arthroscopic surgical findings were considered the reference standard. Wilcoxon rank sum, Chi-square/Fisher's exact, and DeLong's tests, as well as intraclass correlation coefficients (ICCs) were used to evaluate differences between THRIVE and 2D-PD-FS images.

RESULTS

THRIVE images had significantly higher CNR (p < 0.001), and subjective ratings of image noise (p = 0.009) and sharpness (p = 0.039) than 2D-PD-FS images (p < 0.001). THRIVE images had similar (p ≥ 0.18) diagnostic performance (sensitivity, 93.0-97.2%; specificity, 95.8-100%; accuracy, 95.2-97.6%) for the diagnosis of SLAP and Bankart lesions with excellent agreement (ICC = 0.898-0.942) when compared to 2D-PD-FS images (sensitivity, 86.1-91.7%; specificity, 93.8-95.8%; accuracy, 90.5-92.9%; agreement, ICC = 0.782-0.858). The scan time was reduced by 69% for THRIVE sequence compared to 2D-PD-FS sequence (2 min 40 s vs. 8 min 40 s).

CONCLUSION

The THRIVE sequence may be helpful in the diagnosis of SLAP and Bankart lesions, and may be routinely used during direct shoulder 3T MRA.

The role of biomaterials in the treatment of meniscal tears

Extensive investigations over the recent decades have established the anatomical, biomechanical and functional importance of the meniscus in the knee joint. As a functioning part of the joint, it serves to prevent the deterioration of articular cartilage and subsequent osteoarthritis. To this end, meniscus repair and regeneration is of particular interest from the biomaterial, bioengineering and orthopaedic research community. Even though meniscal research is previously of a considerable volume, the research community with evolving material science, biology and medical advances are all pushing toward emerging novel solutions and approaches to the successful treatment of meniscal difficulties. This review presents a tactical evaluation of the latest biomaterials, experiments to simulate meniscal tears and the state-of-the-art materials and strategies currently used to treat tears.

Three-Dimensional Fast Spin-Echo Imaging without Fat Suppression of the Knee: Diagnostic Accuracy Comparison to Fat-Suppressed Imaging on 1.5T MRI

PURPOSE

To evaluate the diagnostic performance of three-dimensional fast spin-echo (3D FSE-Cube) without fat suppression (NFS) for detecting knee lesions, using comparison to 3D FSE-Cube with fat suppression (FS).

MATERIALS AND METHODS

One hundred twenty-four patients who underwent 1.5T knee magnetic resonance imaging (MRI) scans and 25 subsequent arthroscopic surgeries were retrospectively reviewed. Using arthroscopic results and two-dimensional images as reference standards, diagnostic performances of 3D FSE-Cube-NFS and FS imaging about lesions of ligament, meniscus, subchondral bone marrow edema (BME), and cartilage were compared. Scan parameters of 3D FSE-Cube imaging were previously optimized by a porcine knee phantom.

RESULTS

No significant differences were observed between detection rates of NFS and FS imaging for detecting lesions of meniscus and cartilage (p>0.05). However, NFS imaging had lower sensitivity for detection of medial collateral ligament (MCL) tears, and lower sensitivity and specificity for detection of BME lesions, compared to FS imaging (p<0.05).

CONCLUSION

3D FSE-Cube-NFS imaging showed similar diagnostic performance for detecting lesions of meniscus or cartilage compared to FS imaging, unlike MCL or BME lesions.

Articular cartilage grading of the knee: diagnostic performance of fat-suppressed 3D volume isotropic turbo spin-echo acquisition (VISTA) compared with 3D T1 high-resolution isovolumetric examination (THRIVE)

Background Conventionally, two-dimensional (2D) fast spin-echo (FSE) sequences have been widely used for clinical cartilage imaging as well as gradient (GRE) sequences. Recently, three-dimensional (3D) volumetric magnetic resonance imaging (MRI) has been introduced with one 3D volumetric scan, and this is replacing slice-by-slice 2D MR scans. Purpose To evaluate the image quality and diagnostic performance of two 3D sequences for abnormalities of knee cartilage: fat-suppressed (FS) FSE-based 3D volume isotropic turbo spin-echo acquisition (VISTA) and GRE-based 3D T1 high-resolution isovolumetric examination (THRIVE). Material and Methods The institutional review board approved the protocol of this retrospective review. This study enrolled 40 patients (41 knees) with arthroscopically confirmed abnormalities of cartilage. All patients underwent isovoxel 3D-VISTA and 3D-THRIVE MR sequences on 3T MRI. We assessed the cartilage grade on the two 3D sequences using arthroscopy as a gold standard. Inter-observer agreement for each technique was evaluated with the intraclass correlation coefficient (ICC). Differences in the area under the curve (AUC) were compared between the 3D-THRIVE and 3D-VISTA. Results Although inter-observer agreement for both sequences was excellent, the inter-observer agreement for 3D-VISTA was higher than for 3D-THRIVE for cartilage grading in all regions of the knee. There was no significant difference in the diagnostic performance ( P > 0.05) between the two sequences for detecting cartilage grade. Conclusion FSE-based 3D-VISTA images had good diagnostic performance that was comparable to GRE-based 3D-THRIVE images in the evaluation of knee cartilage, and can be used in routine knee MR protocols for the evaluation of cartilage.

Three-dimensional reconstructed magnetic resonance scans: Accuracy in identifying and defining knee meniscal tears

AIM

To determine whether three-dimensional (3D) reconstruction from conventional magnetic resonance imaging (MRI) is able to accurately detect a meniscal tear, and define the configuration.

METHODS

Thirty-three patients’ 3T MRI scan data were collected and sagittal uni-planar 3D reconstructions performed from the preoperative MRI. There were 24 meniscal tears in 24 patients, and nine controls. All patients had arthroscopic corroboration of MRI findings. Two independent observers prospectively reported on all 33 reconstructions. Meniscal tear presence or absence was noted, and tear configuration subsequently categorised as either radial, bucket-handle, parrot beak, horizontal or complex.

RESULTS

Identification of control menisci or meniscal tear presence was excellent (Accuracy: observer 1 = 90.9%; observer 2 = 81.8%). Of the tear configurations, bucket handle tears were accurately identified (Accuracy observer 1 and 2 = 80%). The remaining tear configurations were not accurately discernable.

CONCLUSION

Uni-planar 3D reconstruction from 3T MRI knee scan sequences are useful in identifying normal menisci and menisci with bucket-handle tears. Advances in MRI sequencing and reconstruction software are awaited for accurate identification of the remaining meniscal tear configurations.

Diagnostic Efficacy of 3-T MRI for Knee Injuries Using Arthroscopy as a Reference Standard: A Meta-Analysis

OBJECTIVE

The objectives of our study were to assess the evidence for the diagnostic efficacy of 3-T MRI for meniscal and anterior cruciate ligament (ACL) injuries in the knee using arthroscopy as the reference standard and to compare these results with the results of a previous meta-analysis assessing 1.5-T MRI.

MATERIALS AND METHODS

The online Cochrane Library, MEDLINE, and PubMed databases were searched using the following terms: MRI AND ((3 OR three) AND (Tesla OR T)) AND knee AND arthroscopy AND (menisc* OR ligament). Patient demographics, patient characteristics, MRI scanning details, and diagnostic results were investigated. The methodologic quality of the included studies was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. A meta-analysis of studies using 3-T MRI was performed, and the results were compared with a previous meta-analysis of studies using 1.5-T MRI.

RESULTS

One hundred one studies were identified by the search strategy, and 13 studies were included in our review. Twelve studies were considered to have level 1b evidence, and one study was considered to have level 2b evidence. All 13 studies had high methodologic integrity and low risk of bias using the QUADAS-2 tool. The studies included 1197 patients with a mean age of 41.9 years. Ten of the 13 studies were eligible for meta-analysis. The mean sensitivity and mean specificity of 3-T MRI for knee injuries by location were as follows: medial meniscus, 0.94 (95% CI, 0.91-0.96) and 0.79 (95% CI, 0.75-0.83), respectively; lateral meniscus, 0.81 (95% CI, 0.75-0.85) and 0.87 (95% CI, 0.84-0.89); and ACL, 0.92 (95% CI, 0.83-0.96) and 0.99 (95% CI, 0.96-1.00). The specificity of 3-T MRI for injuries of the lateral meniscus was significantly lower than that of 1.5-T MRI (p = 0.0013).

CONCLUSION

This study does not provide evidence that 3-T scanners have superior diagnostic efficacy for meniscal damage and ACL integrity when compared with previous studies of 1.5-T machines.

Magnetic Resonance Imaging in Patients With Mechanical Low Back Pain Using a Novel Rapid-Acquisition Three-Dimensional SPACE Sequence at 1.5-T: A Pilot Study Comparing Lumbar Stenosis Assessment With Routine Two-Dimensional Magnetic Resonance Sequences

PURPOSE

To minimize the burden of overutilisation of lumbar spine magnetic resonance imaging (MRI) on a resource-constrained public healthcare system, it may be helpful to image some patients with mechanical low-back pain (LBP) using a simplified rapid MRI screening protocol at 1.5-T. A rapid-acquisition 3-dimensional (3D) SPACE (Sampling Perfection with Application-optimized Contrasts using different flip angle Evolution) sequence can demonstrate common etiologies of LBP. We compared lumbar spinal canal stenosis (LSCS) and neural foraminal stenosis (LNFS) assessment on 3D SPACE against conventional 2-dimensional (2D) MRI.

METHODS

We prospectively performed 3D SPACE and 2D spin-echo MRI sequences (axial or sagittal T1-weighted or T2-weighted) at 1.5-T in 20 patients. Two blinded readers assessed levels L3-4, L4-5 and L5-S1 using: 1) morphologic grading systems, 2) global impression on the presence or absence of clinically significant stenosis (n = 60 disc levels for LSCS, n = 120 foramina for LNFS). Reliability statistics were calculated.

RESULTS

Acquisition time was ∼5 minutes for SPACE and ∼20 minutes for 2D MRI sequences. Interobserver agreement of LSCS was substantial to near perfect on both sequences (morphologic grading: kappa [k] = 0.71 SPACE, k = 0.69 T2-weighted; global impression: k = 0.85 SPACE, k = 0.78 T2-weighted). LNFS assessment had superior interobserver reliability using SPACE than T1-weighted (k = 0.54 vs 0.37). Intersequence agreement of findings between SPACE and 2D MRI was substantial to near perfect by global impression (LSCS: k = 0.78 Reader 1, k = 0.85 Reader 2; LNFS: k = 0.63 Reader 1, k = 0.66 Reader 2).

CONCLUSIONS

3D SPACE was acquired in one-quarter the time as the conventional 2D MRI protocol, had excellent agreement with 2D MRI for stenosis assessment, and had interobserver reliability superior to 2D MRI. These results justify future work to explore the role of 3D SPACE in a rapid MRI screening protocol at 1.5-T for mechanical LBP.

Diagnostic performance of 3D TSE MRI versus 2D TSE MRI of the knee at 1.5 T, with prompt arthroscopic correlation, in the detection of meniscal and cruciate ligament tears

Objective

To compare the diagnostic performance of the three-dimensional turbo spin-echo (3D TSE) magnetic resonance imaging (MRI) technique with the performance of the standard two-dimensional turbo spin-echo (2D TSE) protocol at 1.5 T, in the detection of meniscal and ligament tears.

Materials and Methods

Thirty-eight patients were imaged twice, first with a standard multiplanar 2D TSE MR technique, and then with a 3D TSE technique, both in the same 1.5 T MRI scanner. The patients underwent knee arthroscopy within the first three days after the MRI. Using arthroscopy as the reference standard, we determined the diagnostic performance and agreement.

Results

For detecting anterior cruciate ligament tears, the 3D TSE and routine 2D TSE techniques showed similar values for sensitivity (93% and 93%, respectively) and specificity (80% and 85%, respectively). For detecting medial meniscal tears, the two techniques also had similar sensitivity (85% and 83%, respectively) and specificity (68% and 71%, respectively). In addition, for detecting lateral meniscal tears, the two techniques had similar sensitivity (58% and 54%, respectively) and specificity (82% and 92%, respectively). There was a substantial to almost perfect intraobserver and interobserver agreement when comparing the readings for both techniques.

Conclusion

The 3D TSE technique has a diagnostic performance similar to that of the routine 2D TSE protocol for detecting meniscal and anterior cruciate ligament tears at 1.5 T, with the advantage of faster acquisition.

Reporting knee meniscal tears: technical aspects, typical pitfalls and how to avoid them

Magnetic resonance imaging (MRI) is the most accurate imaging technique in the diagnosis of meniscal lesions and represents a standard tool in knee evaluation. MRI plays a critical role in influencing the treatment decision and enables information that would obviate unnecessary surgery including diagnostic arthroscopy. An accurate interpretation of the knee depends on several factors, starting with technical aspects including radiofrequency coils, imaging protocol and magnetic field strength. The use of dedicated high-resolution orthopaedic coils with a different number of integrated elements is mandatory in order to ensure high homogeneity of the signal and high-resolution images. The clinical imaging protocol of the knee includes different MRI sequences with high-spatial resolution in all orientations: sagittal, coronal, and axial. Usually, the slice thickness is 3 mm or less, even with standard two-dimensional fast spin echo sequences. A common potential reason for pitfalls and errors of interpretation is the unawareness of the normal tibial attachments and capsular attachment of the menisci. Complete description of meniscal tears implies that the radiologist should be aware of the patterns and the complex classification of the lesions.

TEACHING POINTS

• Technical factors may influence MRI interpretation. • Unawareness of the normal meniscal anatomy may lead to errors of interpretation. • Description of meniscal tears implies the knowledge of meniscal tear classification.

Clinical value of fat-suppressed 3D volume isotropic spin-echo (VISTA) sequence compared to 2D sequence in evaluating internal structures of the knee

BACKGROUND

Although many three-dimensional (3D) magnetic resonance imaging (MRI) sequences have been used in the clinical field, there are no studies on fat-suppressed (FS) 3D sequences for the diagnosis of knee abnormalities.

PURPOSE

To evaluate the usefulness of FS 3D volume isotropic turbo spin echo acquisition (VISTA) imaging for diagnosis of internal structures of knee.

MATERIAL AND METHODS

In 137 patients with 138 knee MRI examinations who had undergone both FS 3D VISTA MRI and two-dimensional (2D) MRI of the knee at 3.0 T, arthroscopic surgery was subsequently performed. Multiplanar reformations (MPR) of FS 3D VISTA images and their MPR sequences were compared with 2D MR images of axial T1-weighted (T1W) images, axial FS T2-weighted (T2W) images, coronal FS T2W images, and sagittal T2W images. Two musculoskeletal radiologists reviewed the images independently.

RESULTS

Arthroscopy revealed 33 anterior cruciate ligament tears, three posterior cruciate ligament tears, 42 lateral meniscus tears, and 68 medial meniscus tears. Five medial collateral ligament tears were clinically confirmed. Image acquisition time was shorter for FS 3D VISTA imaging than 2D imaging. There were no significant differences in diagnostic values between FS 3D VISTA and 2D imaging (P > 0.05). There were excellent inter-observer agreements for both FS 3D VISTA and 2D imaging (κ > 0.84).

CONCLUSION

FS 3D VISTA imaging could replace 2D imaging because of equal diagnostic ability and shorter scan time.

MR imaging-based diagnosis and classification of meniscal tears

Magnetic resonance (MR) imaging is currently the modality of choice for detecting meniscal injuries and planning subsequent treatment. A thorough understanding of the imaging protocols, normal meniscal anatomy, surrounding anatomic structures, and anatomic variants and pitfalls is critical to ensure diagnostic accuracy and prevent unnecessary surgery. High-spatial-resolution imaging of the meniscus can be performed using fast spin-echo and three-dimensional MR imaging sequences. Normal anatomic structures that can mimic a tear include the meniscal ligament, meniscofemoral ligaments, popliteomeniscal fascicles, and meniscomeniscal ligament. Anatomic variants and pitfalls that can mimic a tear include discoid meniscus, meniscal flounce, a meniscal ossicle, and chondrocalcinosis. When a meniscal tear is identified, accurate description and classification of the tear pattern can guide the referring clinician in patient education and surgical planning. For example, longitudinal tears are often amenable to repair, whereas horizontal and radial tears may require partial meniscectomy. Tear patterns include horizontal, longitudinal, radial, root, complex, displaced, and bucket-handle tears. Occasionally, meniscal tears can be difficult to detect at imaging; however, secondary indirect signs, such as a parameniscal cyst, meniscal extrusion, or linear subchondral bone marrow edema, should increase the radiologist's suspicion for an underlying tear. Awareness of common diagnostic errors can ensure accurate diagnosis of meniscal tears. Online supplemental material is available for this article.

The usefulness of the three-dimensional enhanced T1 high-resolution isotropic volume excitation MR in the evaluation of shoulder pathology: comparison with two-dimensional enhanced T1 fat saturation MR

OBJECTIVE

To evaluate the diagnostic accuracy of three-dimensional (3D) enhanced T1 high-resolution isotropic volume excitation (eTHRIVE) shoulder MR for variable shoulder pathology such as rotator cuff tear, labral injury and synovial pathology in comparison with two-dimensional enhanced fast spin echo T1 fat saturation (2D T1 FS) sequences MR.

METHODS

This retrospective study included 86 patients who underwent MRI of the shoulder using eTHRIVE technique. Two radiologists evaluated anatomic identification of the supraspinatus, glenoid labrum and acromioclavicular joint (AC joint) on routine MRI sequences (2D T1 FS) and compared them with the reformatted eTHRIVE images. Subjective scoring of the images was performed with a four-point scale that rated the degree of discrimination of the shape of the supraspinatus, glenoid labrum and AC joint. The diagnostic accuracy of eTHRIVE compared with routine MR images was evaluated in terms of rotator cuff pathology, labral pathology and synovial pathology.

RESULTS

Anatomic identification scores of the supraspinatus tendon and labrum were significantly lower for eTHRIVE than for 2D T1 FS. There were no significant differences between eTHRIVE and 2D T1 FS in anatomic identification of the AC joint. There were no significant differences between eTHRIVE and 2D T1 FS in diagnosing the three disease categories.

CONCLUSION

eTHRIVE had comparable diagnostic accuracy to 2D T1 FS imaging in the evaluation of rotator cuff tears, labral injury and synovial pathology, but anatomic identification was inferior to that of 2D T1 FS.

ADVANCES IN KNOWLEDGE

The accuracy of 3D eTHRIVE imaging is comparable to that of 2D T1 FS for the diagnosis of rotator cuff tears, labral injury and synovial pathology.

Accuracy of high-resolution ultrasound in the detection of meniscal tears and determination of the visible area of menisci

BACKGROUND

Imaging is of great importance in diagnosing meniscal tears. The aim of this study was to assess the accuracy of high-resolution ultrasound in the diagnosis of meniscal tears, with arthroscopic examination as the standard reference, after resolution was confirmed with a target-mounted reference phantom. An additional goal was to elucidate the area of the meniscus that could be visualized with the same ultrasound machine after placement of markers into the menisci of cadaveric knees.

METHODS

Seventy patients were included for the assessment of the accuracy of a high-resolution ultrasound machine with a 14.0 to 6.0-MHz linear transducer. The preoperative ultrasound diagnosis, in terms of the presence and type of tear, was compared with that in the surgical reports. In the cadaveric studies, nine needles were placed in the peripheral zone of the menisci at regular intervals and the number of needles that could be observed with the system was recorded.

RESULTS

The overall sensitivity, specificity, positive predictive value, and negative predictive value of ultrasound examination for meniscal tears were 88%, 85%, 85%, and 88%, respectively. These statistical parameters did not differ significantly between the medial and lateral menisci. The sensitivity for diagnosing horizontal, vertical, radial, flap, bucket-handle, and complex tears and for detecting discoid lateral menisci was 83%, 64%, 0%, 64%, 54%, 90%, and 80%, respectively. Ten percent of the lateral menisci could not be evaluated because of poor images. The cadaveric studies revealed that the ultrasound visualized the entire meniscus except for the anterior horn.

CONCLUSIONS

The findings of this study suggest that ultrasound examination may be suitable for screening for meniscal tears. The fact that almost 10% of the lateral menisci could not be evaluated because of poor images appears to be a weakness of ultrasound.

Reliability of 3D localisation of ACL attachments on MRI: comparison using multi-planar 2D versus high-resolution 3D base sequences

PURPOSE

Anatomic placement of anterior cruciate ligament (ACL) grafts at arthroscopic reconstruction can be challenging. Localising ACL attachments on magnetic resonance imaging (MRI) sequences pre-operatively could aid with planning for anatomic graft placement. Though ACL attachments can be identified on two-dimensional (2D) MRI, slice thickness theoretically limits out-of-plane accuracy and a 3D MRI base sequence with smaller isotropic voxels may improve observer reliability in localising ACL attachment locations. The purpose of this study was to test whether a high-resolution 3D sequence improved inter- and intra-observer reliability of ACL attachment localisation compared with conventional 2D MRI for this application.

METHODS

Twenty paediatric knees were retrospectively scanned at 1.5 Tesla with multi-planar 2D proton density (slice thickness 3-4 mm) and T2-weighted 3D multiple-echo data image combination gradient echo (isotropic 0.8 mm voxels) sequences. Two observers blinded to each others' findings identified ACL attachments on MRI slices, and 3D reconstructions showing ACL attachments were produced. ACL attachment centre locations and areas were calculated, and reliability assessed.

RESULTS

Inter-observer variation of centre locations of ACL attachments identified on 3D versus 2D sequences was not significantly different (mean ± SD): 1.8 ± 0.6 versus 1.5 ± 0.7 mm at femoral attachments, 1.7 ± 0.7 versus 1.5 ± 0.8 mm at tibial attachments (p > 0.05). The 95 % confidence interval for centre locations was <4.0 mm in all cases. Inter-observer reliability of attachment areas was not higher for 3D sequences.

CONCLUSIONS

ACL attachment centres were localised with high and similar inter- and intra-observer reliability on a high-resolution 3D and multi-planar conventional 2D sequences. Using this technique, MRI could potentially be used for planning and intra-operative guidance of anatomic ACL reconstruction, whether from 2D or 3D base sequences. Surgeons in clinical practice need not order a lengthy dedicated 3D MRI to localise ligament attachments, but can confidently use a standard 2D MRI for this application.

LEVEL OF EVIDENCE

III.

MRI of the lumbar spine: comparison of 3D isotropic turbo spin-echo SPACE sequence versus conventional 2D sequences at 3.0 T

BACKGROUND

Three-dimensional (3D) fast spin-echo sequence with variable flip-angle refocusing pulse allows retrospective alignments of magnetic resonance imaging (MRI) in any desired plane.

PURPOSE

To compare isotropic 3D T2-weighted (T2W) turbo spin-echo sequence (TSE-SPACE) with standard two-dimensional (2D) T2W TSE imaging for evaluating lumbar spine pathology at 3.0 T MRI.

MATERIAL AND METHODS

Forty-two patients who had spine surgery for disk herniation and had 3.0 T spine MRI were included in this study. In addition to standard 2D T2W TSE imaging, sagittal 3D T2W TSE-SPACE was obtained to produce multiplanar (MPR) images. Each set of MR images from 3D T2W TSE and 2D TSE-SPACE were independently scored for the degree of lumbar neural foraminal stenosis, central spinal stenosis, and nerve compression by two reviewers. These scores were compared with operative findings and the sensitivities were evaluated by McNemar test. Inter-observer agreements and the correlation with symptoms laterality were assessed with kappa statistics.

RESULTS

The 3D T2W TSE and 2D TSE-SPACE had similar sensitivity in detecting foraminal stenosis (78.9% versus 78.9% in 32 foramen levels), spinal stenosis (100% versus 100% in 42 spinal levels), and nerve compression (92.9% versus 81.8% in 59 spinal nerves). The inter-observer agreements (κ = 0.849 vs. 0.451 for foraminal stenosis, κ = 0.809 vs. 0.503 for spinal stenosis, and κ = 0.681 vs. 0.429 for nerve compression) and symptoms correlation (κ = 0.449 vs. κ = 0.242) were better in 3D TSE-SPACE compared to 2D TSE. 3D TSE-SPACE with oblique coronal MPR images demonstrated better inter-observer agreements compared to 3D TSE-SPACE without oblique coronal MPR images (κ = 0.930 vs. κ = 0.681).

CONCLUSION

Isotropic 3D T2W TSE-SPACE at 3.0 T was comparable to 2D T2W TSE for detecting foraminal stenosis, central spinal stenosis, and nerve compression with better inter-observer agreements and symptom correlation.

Evaluation of shoulder pathology: three-dimensional enhanced T1 high-resolution isotropic volume excitation MR vs two-dimensional fast spin echo T2 fat saturation MR

OBJECTIVE

To evaluate the diagnostic accuracy of three-dimensional (3D) enhanced T1 high-resolution isotropic volume excitation (eTHRIVE) shoulder MR for the detection of rotator cuff tears, labral lesions and calcific tendonitis of the rotator cuff in comparison with two-dimensional (2D) fast spin echo T2 fat saturation (FS) MR.

METHODS

This retrospective study included 73 patients who underwent shoulder MRI using the eTHRIVE technique. Shoulder MR images were interpreted separately by two radiologists. They evaluated anatomic identification and image quality of the shoulder joint on routine MRI sequences (axial and oblique coronal T2 FS images) and compared them with the reformatted eTHRIVE images. The images were scored on a four-point scale (0, poor; 1, questionable; 2, adequate; 3, excellent) according to the degree of homogeneous and sufficient fat saturation to penetrate bone and soft tissue, visualization of the glenoid labrum and distinction of the supraspinatus tendon (SST). The diagnostic accuracy of eTHRIVE images compared with routine MRI sequences was evaluated in the setting of rotator cuff tears, glenoid labral injuries and calcific tendonitis of the SST.

RESULTS

Fat saturation scores for eTHRIVE were significantly higher than those of the T2 FS for both radiologists. The sensitivity and accuracy of the T2 FS in diagnosing rotor cuff tears were >90%, whereas sensitivity and accuracy of the eTHRIVE method were significantly lower. The sensitivity, specificity and accuracy of both images in diagnosing labral injuries and calcific tendonitis were similar and showed no significant differences. The specificity of both images for the diagnosis of labral injuries and calcific tendonitis was higher than the sensitivities.

CONCLUSION

The accuracy of 3D eTHRIVE imaging was comparable to that of 2D FSE T2 FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST. The 3D eTHRIVE technique was superior to 2D FSE T2 FS in terms of fat saturation. Overall, 3D eTHRIVE was inferior to T2 FS in the evaluation of rotator cuff tears because of poor contrast between joint fluid and tendons.

ADVANCES IN KNOWLEDGE

The accuracy of 3D eTHRIVE imaging is comparable to that of 2D FSE T2 FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST.

Reliability of estimates of ACL attachment locations in 3-dimensional knee reconstruction based on routine clinical MRI in pediatric patients

BACKGROUND

Current techniques of anterior cruciate ligament (ACL) reconstruction focus on the placement of femoral and tibial tunnels at anatomic ACL attachments, which can be difficult to identify intraoperatively.

PURPOSE

To determine whether the 3-dimensional (3D) center of ACL attachments can be reliably detected from routine magnetic resonance imaging (MRI) in patients with intact ACLs and whether the reliability of this technique changes if the ACL is torn.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

A computer technique was developed in which users identify points along ACL attachments on routine clinical MRI of preoperative knees. These attachments are then displayed on a 3D MRI reconstruction, which can be used as a visual guide for the surgeon during arthroscopic surgery. Thirty-seven pediatric patients (age range, 10-17 years) with ACL tears and 37 controls with intact ACLs were examined. Two blinded observers identified cruciate ligament attachments on routine clinical 1.5-T MRI of knees. From the resulting 3D model, the location of the center of each ligament attachment site and its area were calculated and reliability assessed.

RESULTS

Mean interobserver variation of the centers of ACL attachments for the intact versus torn ACL was 1.7 ± 0.9 mm versus 1.8 ± 1.1 mm (femoral) and 1.4 ± 0.9 mm versus 1.7 ± 1.0 mm (tibial), respectively (P > .05). The 95% confidence interval for the center location was at most 4 mm. The identified ACL attachment areas were more variable, with interobserver reliability ranging from fair to excellent by the intraclass correlation coefficient. Overlap of ligament areas between observers for the intact versus torn ACL was 70% ± 15% versus 73% ± 12% (femoral) and 79% ± 9% versus 78% ± 10% (tibial), respectively (P > .05). In all cases, intraobserver reliability was superior to interobserver reliability.

CONCLUSION

The 3D locations of ACL tibial and femoral attachment centers were identified from routine clinical MRI with variability averaging less than 2 mm between 2 observers. The margin of error was at most 4 mm, representing the thickness of a single axial MRI slice, whether the ACL was intact or torn. Remnant tissue at attachments allows a reliable assessment even of torn ligaments. Identification of the ligament attachment areas was more user dependent than was identification of the attachment centers.

A historical overview of magnetic resonance imaging, focusing on technological innovations

Magnetic resonance imaging (MRI) has now been used clinically for more than 30 years. Today, MRI serves as the primary diagnostic modality for many clinical problems. In this article, historical developments in the field of MRI will be discussed with a focus on technological innovations. Topics include the initial discoveries in nuclear magnetic resonance that allowed for the advent of MRI as well as the development of whole-body, high field strength, and open MRI systems. Dedicated imaging coils, basic pulse sequences, contrast-enhanced, and functional imaging techniques will also be discussed in a historical context. This article describes important technological innovations in the field of MRI, together with their clinical applicability today, providing critical insights into future developments.

Partial tears of the anterior cruciate ligament: diagnostic performance of isotropic three-dimensional fast spin echo (3D-FSE-Cube) MRI

PURPOSE

To compare the performance of 3D-FSE-Cube MRI to arthroscopy, the reference test for the diagnosis of partial anterior cruciate ligament (ACL) tears.

METHODS

A retrospective study was performed including all patients who underwent surgery for an ACL tear in our Sports Surgery Unit from January 2008 to December 2009. All patients underwent a preoperative MRI, conventional 2D or 3D-Cube. The diagnosis of a partial tear was based on the appearance of the ligament bundles and signal quality on MRI, and on the continuity of the fibers on arthroscopy and the quality of the remaining ligament. Sixty-four of the 312 included patients underwent MRI 3D-Cube and 248 conventional 2D-MRI. The series included 82 women and 223 men, mean age 33.3 ± 19.6 years. Arthroscopy did not reveal any normal ACL, 247/312 (79.2 %) complete tears, and 65/312 (20.8 %) partial tears, with 50/65 (76.9 %) involving the anteromedial bundle and 15/65 (23.1 %) the posterolateral.

RESULTS

The results of MRI 3D-Cube were as follows: sensitivity 95 % CI = 62.5 ± 23.7 %, specificity 95 % CI = 93.7 ± 6.9 %, likelihood ratio LR(+) = 9.9, LR(-) = 0.4 and accuracy 85.9 %. Results of conventional 2D-MRI were as follows: sensitivity 95 % CI = 10.2 ± 8.5 %, specificity 95 % CI = 96.5 ± 2.5 %, LR(+) = 2.9, LR(-) = 0.9 and accuracy 79.4 %. The diagnostic performance of MRI 3D-Cube was better than conventional 2D-MRI.

CONCLUSION

The diagnostic performance of MRI 3D-Cube in partial ACL tears was good and significantly better than conventional 2D-MRI. The likelihood of having a positive test was 9.9 times higher in a patient with a partial tear. A negative result did not exclude this diagnosis.