Proton Density-weighted MR Images Research Articles

Retraction Note: Hermite-based texture feature extraction for classification of humeral head in proton density-weighted MR images

Retraction Note: Hermite-based texture feature extraction for classification of humeral head in proton density-weighted MR images

Fully Automatic Knee Joint Segmentation and Quantitative Analysis for Osteoarthritis from Magnetic Resonance (MR) Images Using a Deep Learning Model.

BackgroundWe aimed to develop and evaluate a deep learning-based method for fully automatic segmentation of knee joint MR imaging and quantitative computation of knee osteoarthritis (OA)-related imaging biomarkers.Material/MethodsThis retrospective study included 843 volumes of proton density-weighted fat suppression MR imaging. A convolutional neural network segmentation method with multiclass gradient harmonized Dice loss was trained and evaluated on 500 and 137 volumes, respectively. To assess potential morphologic biomarkers for OA, the volumes and thickness of cartilage and meniscus, and minimal joint space width (mJSW) were automatically computed and compared between 128 OA and 162 control data.ResultsThe CNN segmentation model produced reasonably high Dice coefficients, ranging from 0.948 to 0.974 for knee bone compartments, 0.717 to 0.809 for cartilage, and 0.846 for both lateral and medial menisci. The OA-related biomarkers computed from automatic knee segmentation achieved strong correlation with those from manual segmentation: average intraclass correlations of 0.916, 0.899, and 0.876 for volume and thickness of cartilage, meniscus, and mJSW, respectively. Volume and thickness measurements of cartilage and mJSW were strongly correlated with knee OA progression.ConclusionsWe present a fully automatic CNN-based knee segmentation system for fast and accurate evaluation of knee joint images, and OA-related biomarkers such as cartilage thickness and mJSW were reliably computed and visualized in 3D. The results show that the CNN model can serve as an assistant tool for radiologists and orthopedic surgeons in clinical practice and basic research.

Bone-patellar tendon-bone autograft maturation is superior to double-bundle hamstring tendon autograft maturation following anatomical anterior cruciate ligament reconstruction.

The primary purpose of this study was to evaluate the second-look arthroscopic findings 1year postoperatively and magnetic resonance imaging (MRI) findings 2years after anterior cruciate ligament reconstruction (ACLR) using bone-patellar tendon-bone autograft (BTB) or hamstring tendon autograft (HT). Secondary purpose included clinical results from physical examination, including range of motion, Lachman test, pivot shift test, and knee anterior laxity evaluation, and the clinical score for subjective evaluations at 2years after surgery. Between 2015 and 2018, 75 patients with primary ACL injuries were divided into either the BTB group (n = 30) or HT group (n = 45). When using HT, an anatomical double-bundle ACLR was performed. BTB was indicated for athletes with sufficient motivation to return to sporting activity. Graft maturation on second-look arthroscopy was scored in terms of synovial coverage and revascularization. All participants underwent postoperative MRI evaluation 2years postoperatively. The signal intensity (SI) characteristics of the reconstructed graft were evaluated using oblique axial proton density-weighted MR imaging (PDWI) perpendicular to the grafts. The signal/noise quotient (SNQ) was calculated to quantitatively determine the normalized SI. For clinical evaluation, the Lachman test, pivot shift test, KT-2000 evaluation, Lysholm score, and Knee injury and Osteoarthritis Outcome Score (KOOS) were used. Arthroscopic findings showed that the graft maturation score in the BTB group (3.6 ± 0.7) was significantly greater than that in the anteromedial bundle (AMB; 2.9 ± 0.2, p = 0.02) and posterolateral bundle (PLB; 2.0 ± 0.9, p = 0.001) in the HT group. The mean MRI-SNQs were as follows: BTB, 2.3 ± 0.5; AMB, 2.9 ± 0.9; and PLB, 4.1 ± 1.1. There were significant differences between BTB, AMB, and PLB (BTB and AMB: p = 0.04, BTB and PLB: p = 0.003, AMB and PLB: p = 0.03). Second-look arthroscopic maturation score and MRI-SNQ value significantly correlated for BTB, AMB, and PLB. No significant differences were detected in clinical scores. There was a significant difference (p = 0.02) in the knee laxity evaluation (BTB: 0.9 ± 1.1mm; HT: 2.0 ± 1.9mm). BTB maturation is superior to that of double-bundle HT based on morphological and MRI evaluations following anatomical ACLR, although no significant differences were found in clinical scores. Regarding clinical relevance, the advantages of BTB may help clinicians decide on using the autograft option for athletes with higher motivation to return to sporting activity because significant differences were observed in morphological evaluation, MRI assessment, and knee anterior laxity evaluation between BTB and double-bundle HT. Level IV.

Fully Automated Diagnosis of Anterior Cruciate Ligament Tears on Knee MR Images by Using Deep Learning.

To investigate the feasibility of using a deep learning-based approach to detect an anterior cruciate ligament (ACL) tear within the knee joint at MRI by using arthroscopy as the reference standard. A fully automated deep learning-based diagnosis system was developed by using two deep convolutional neural networks (CNNs) to isolate the ACL on MR images followed by a classification CNN to detect structural abnormalities within the isolated ligament. With institutional review board approval, sagittal proton density-weighted and fat-suppressed T2-weighted fast spin-echo MR images of the knee in 175 subjects with a full-thickness ACL tear (98 male subjects and 77 female subjects; average age, 27.5 years) and 175 subjects with an intact ACL (100 male subjects and 75 female subjects; average age, 39.4 years) were retrospectively analyzed by using the deep learning approach. Sensitivity and specificity of the ACL tear detection system and five clinical radiologists for detecting an ACL tear were determined by using arthroscopic results as the reference standard. Receiver operating characteristic (ROC) analysis and two-sided exact binomial tests were used to further assess diagnostic performance. The sensitivity and specificity of the ACL tear detection system at the optimal threshold were 0.96 and 0.96, respectively. In comparison, the sensitivity of the clinical radiologists ranged between 0.96 and 0.98, while the specificity ranged between 0.90 and 0.98. There was no statistically significant difference in diagnostic performance between the ACL tear detection system and clinical radiologists at P < .05. The area under the ROC curve for the ACL tear detection system was 0.98, indicating high overall diagnostic accuracy. There was no significant difference between the diagnostic performance of the ACL tear detection system and clinical radiologists for determining the presence or absence of an ACL tear at MRI.© RSNA, 2019Supplemental material is available for this article.

Quantification of Artifacts in MR Images Caused by Commonly Used Dental Materials

Background: Although new approaches for application of magnetic resonance imaging (MRI) in dentistry have been promising, the presence of dental materials in the oral cavity represents a major obstacle to generating quality MRI data. The resulting artifacts can adversely affect diagnostic accuracy of oral and maxillofacial conditions. Objectives: This study aimed to detect and assess artifacts caused by metallic and non-metallic dental materials in MR images. Materials and Methods: Nineteen commonly used dental materials were used in an in vitro assay. An empty cube-shaped phantom with internal dimensions of 15 × 15 × 15 cm3 was fabricated of polyester and filled with paraffin or distilled water to create optimal contrast for T1-weighted (T1W; for anatomical structures), T2-weighted (T2W, for pathological conditions) and proton density-weighted (PDW) MR images. Dental material samples were manufactured and placed at the center of the mold using polyester tubes. All samples were then subjected to MRI using two-dimensional (2D) and three-dimensional (3D) T1W, T2W and PDW imaging sequences. The data were subjected to one-way analysis of variance (ANOVA) followed by mean comparison using the Tukey’s test. Results: Comparison of mean artifact size in 2D and 3D images showed that ceramic caused the smallest (189.48 mm3) and orthodontic metal brackets caused the largest (4307.5 mm3) artifact areas. Assessment of the amount of artifacts created in different imaging sequences revealed minimal artifact in inversion recovery sequence and maximum artifact in gradient echo sequence of the amount of artifacts at different weighing times in 2D and 3D images showed minimal artifacts in PDW and maximum artifacts in T2W. Conclusion: Bracket, titanium implants, and the nickel-chromium (Ni-Cr) materials are the three most susceptible materials to external B0 magnetic field; thus creating huge metal-induced artifacts. The Siemens default two dimensional turbo spin echo (2D-TSE), 2D-BLADE, three dimensional volumetric interpolated breath-hold examination (3D-VIBE) and three dimensional sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) are the most appropriate pulse sequences for the 2D-T1W, 2D-T2W, 3D-T1W, and 3D-T2W evaluations of the bracket/titanium /Ni-Cr materials, respectively. The rest of the materials’ magnetic susceptibility effects are negligible, and artifacts are small.

Differences in MR signal intensity of lateral collateral ligament of knee joint on fat-suppressed proton density-weighted imaging

To investigate the relationship between the increased signal intensity (SI) of proximal lateral collateral ligament (LCL) at femoral attachment site on fat-suppressed (FS) proton density-weighted (PDW) MR imaging and the corresponding histological features on cadaveric knees. MRI was obtained from 11 cadaveric knees. Two musculoskeletal radiologists evaluated SI of LCL at femoral attachment site and the remaining caudal portion on FS PDW imaging. The SI was classified into three types; I = low, II = intermediate to slightly high, III = high SI or intraligamentous discontinuity of fibre. In addition, 100 control subjects were reviewed for normal LCL SI. All proximal LCLs at femoral attachment site showed increased SI (nine cases of Type II and two cases of Type III). The remaining caudal portion presented Type I in all cases. Histological examination of proximal LCL at femoral attachment site revealed loose distribution of fine collagen fibres, intervened with fat and vessels, whereas the remaining caudal portion was composed of parallel distribution of compact collagen bundles. There were no signs of degeneration or tear of the LCL in all our cadaveric knee samples, even for the two cases that presented as Type III. Clinical study identified increased SI of proximal LCL at femoral attachment site in 94% (94/100) of control subjects. Increased SI of proximal LCL at femoral attachment site on FS PDW imaging is due to histological characteristics, not degeneration or tear. Increased SI of proximal LCL at femoral attachment site on FS PDW MR imaging is a common, normal finding that its clinical significance can be neglected.

Segmentation of Bone with Region Based Active Contour Model in PD Weighted MR Images of Shoulder.

Proton density (PD) weighted MR images present inhomogeneity problem, low signal to noise ratio (SNR) and cannot define bone borders clearly. Segmentation of PD weighted images is hampered with these properties of PD weighted images which even limit the visual inspection. The purpose of this study is to determine the effectiveness of segmentation of humeral head from axial PD MR images with active contour without edge (ACWE) model. We included 219 images from our original data set. We extended the use of speckle reducing anisotropic diffusion (SRAD) in PD MR images by estimation of standard deviation of noise (SDN) from ROI. To overcome the problem of initialization of the initial contour of these region based methods, the location of the initial contour was automatically determined with use of circular Hough transform. For comparison, signed pressure force (SPF), fuzzy C-means, and Gaussian mixture models were applied and segmentation results of all four methods were also compared with the manual segmentation results of an expert. Experimental results on our own database show promising results. This is the first study in the literature to segment normal and pathological humeral heads from PD weighted MR images.

Influence of permittivity and electrical conductivity on image pattern of MRI

In proton density-weighted (PDW) MR imaging, the patterns of signal intensity vary depending on the imaged material, and change with the flip angle (FA) applied to the imaged material. The correlation between the pre-determined FA and the actual FA applied to imaged objects was investigated using 4 types of phantoms having different dielectric properties. PDW images were acquired using the spin-echo (SE) method and different pre-determined FA. Dependency of the signal intensity distribution in the phantom on the pre-determined FA differed among phantoms: patterns for water and 0.402 w/w% saline solution phantoms changed with the pre-determined FA, whereas those for olive oil and 4.02 w/w% saline solution phantoms were barely affected by the pre-determined FA. Causes of these phenomena were considered to be the differences between the pre-determined FA and the actual FA among the phantoms; differences were also influenced by the positioning of the phantom. Our study showed that the actual FA in the phantom is greater than the pre-determined FA in high permittivity media, whereas it is reduced by an increased conductivity of the media.

Zoledronic acid reduces knee pain and bone marrow lesions over 1 year: a randomised controlled trial

ObjectivesTo compare the effect of a single infusion of zoledronic acid (ZA) with placebo on knee pain and bone marrow lesions (BMLs).MethodsAdults aged 50–80 years (n=59) with clinical knee osteoarthritis...

Contribution of thin slice (1 mm) oblique coronal proton density-weighted MR images for assessment of anteromedial and posterolateral bundle damage in anterior cruciate ligament injuries

PurposeTo evaluate the diagnostic efficacy of using additional oblique coronal 1mm proton density-weighted (PDW) MR imaging of the knee for detection and grading anterior cruciate ligament (ACL), anteromedial bundle (AMB) and posterolateral bundle (PLB) injuries. Materials and methodsWe prospectively assessed preoperative MR images of 50 patients (36 men, 14 women; age range, 18–62 years). First, we compared the diagnostic performance of routine sagittal (3mm) and additional oblique coronal images (1mm) for ACL tears. Then, we compared the tear types (AMB or PLB) and grade presumed from oblique coronal MR imaging with arthroscopy. ResultsArthroscopy revealed ACL tear in 24 (48%) patients. There was significant difference between sagittal images and arthroscopy results for ACL tear recognition (p<0.001). No significant difference was detected for oblique coronal images when compared with arthroscopy results (p=0.180). Sensitivity and specificity values for ACL tear diagnosis were 37.04% and 95.65% for sagittal images; 74.07% and 91.30% for oblique coronal images. There was no significant difference between arthroscopy and oblique coronal MR images in grading AMB and PLB injuries (p>0.05). ConclusionAddition of thin slice oblique coronal images to conventional sequences could better contribute to better verifying the presence of ACL tear and in determining its grade.

Classification brain MR images through a fuzzy multiwavelets based GMM and probabilistic neural networks

In this paper, a new approach for classification of brain tissues into White Matter, Gray Matter, Cerebral Spinal Fluid, Glial Matter, Connective and MS lesion in multiple sclerosis is introduced. This work considers fuzzy multiwavelets, Gaussian Mixture Model (GMM) and Weighted Probabilistic Neural Networks (WPNN) for the classification of the brain tissues. Multiwavelet packet transformation is employed on brain MR images. Since multiwavelet packet transformation yields larger number of subbands compared to multiwavelet and wavelet transformations, we have proposed a fuzzy-set based theory for selection of the subbands. In contrast to the standard method of subband selection, guided by the criteria of signal energy, our method is based on the discriminatory features from the multiwavelet packet transformation coefficients. Singular values are then computed from the selected subbands. The singular values of lower magnitudes are truncated for effective classification of brain tissues in the presence of noise. Probability density functions of the remaining singular values are modeled as GMM. Model parameters are estimated using stochastic EM (SEM). They are used as features for the classification. The classification is carried out using WPNN. Experiments have been carried out using the data sets composed of three modalities of brain MR images, namely T1 and T2 relaxation times and proton density weighted MR images. Experimental results prove that the proposed approach gives better classification rate at various noise levels compared to existing approaches.

3D magnetic resonance microscopy of a wounded beech branch

Abstract The pruned part of a beech (Fagus sylvatica) branch was imaged by a 3D spin-echo magnetic resonance imaging (MRI) technique to visualize change in structure and water content in the tissues. Proton density-weighted MR images of intact tissues confirmed high moisture content (MC) associated with high MRI signal in the pith, xylem rays and earlywood vessels, as well as in the cambial zone with current annual xylem and phloem increment. MRI images derived from the 3D datasets showed a previously unreported moisture-related structural response of the beech branch to wounding. An extensive wound tissue with a high MRI signal at the wound edge was a conspicuous new structure clearly visualized by 3D MRI. MRI revealed that the xylem at the wound was dehydrated in a cone-shaped pattern extending approximately 4.5 mm deep into the branch. Dehydration was delimited from the underlying sound wood by a layer, corresponding to the reaction zone, of tissue with a high MRI signal and hence high moisture content. Moisture content of these reaction zones in beech determined by MRI were greater than in healthy wood by factors of 1.3–1.8. Accordingly, in the margins of wounded beech wood not only cell wall alterations can be observed, but also an intensive water accumulation, which is probably an integral part of the protective mechanism for the underlying sound wood.

3D-visualization of the temporomandibular joint with focus on the articular disc based on clinical T1-, T2-, and proton density weighted MR images

Objective An approach of 3D-visualization of the temporomandibular joint (TMJ) with special focus on the articular disc based on magnetic resonance imaging (MRI) was developed for the purpose of diagnosis support.

Meniscal Flounce on Knee MRI: Correlation with Meniscal Locations After Positional Changes

The purpose of our study was to illustrate the MRI features of meniscal flounce and the meniscal locations on the tibial plateau after positional changes without external force and to evaluate the correlation of the presence of flounce with meniscal location. For 8 months, 441 knee MR images were prospectively studied for meniscal flounce. Routine MRI was performed on a 10 degrees flexed knee, and flounce was seen in 22 medial menisci (5%). In all 22 of the patients with flounce, additional sagittal proton density-weighted MR images were obtained while the knees were both maximally flexed and maximally extended in a knee surface coil. We evaluated and compared the changes of degree of flounce and meniscal location on the tibial plateau among the three positions. With the maximally extended knee, the flounce disappeared in all cases but one. With the maximally flexed knee, the flounce disappeared in nine cases (9/22, 41%), was slightly released in 11 (11/22, 50%), and was accentuated in two (2/22, 9%). As the knees were more extended, the anterior horns of the menisci migrated more anteriorly, the posterior horns revealed subtle movement without a regular pattern, and the flounce was slightly released or disappeared. Active knee positioning in the knee surface coil changed the degree of meniscal flounce and the meniscal location on the tibial plateau. The meniscal flounce is thought to be a transient physiologic distortion and may be related to meniscal locations on the tibial plateau. It may be changed by varying the knee position.

Utility of delayed gadolinium-enhanced MRI (dGEMRIC) for qualitative evaluation of articular cartilage of patellofemoral joint

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) was used for the measurement of relative proteoglycan depletion of articular cartilage in the patellofemoral (PF) joint following a proprietary protocol, which was compared with the X-ray images, proton density weighted MR images (PDWI) and arthroscopic findings. The study examined 30 knees. The ages ranged from 16 to 74 (average 40.3) years. The Gd-DTPA(2-)containing contrast medium was used in a single dose. The subjects were made to exercise the knee joint for 10 min; and MR images were taken 2 h after intravenous injection of contrast medium. T1-calculated images were produced and the region of interest (ROI) was set as follows. (1) ROI1: entire articular cartilage in a slice through the center of the patella. (2) ROI2: low signal region in T1-calculated images, which were set in a blind fashion by two observers. (3) ROI3: articular cartilage on one side that includes ROI2 where low signal region were detected (medial or lateral). ROI3 was set to examine the contrast of ROI2 with surrounding articular cartilage. The average T1 values of ROI1 was 393.5+/-33.6 ms for radiographic grade 0 and 361.3+/-11.1 ms for grade I, which showed a significant difference (P=0.036). The T1 value of ROI2 was 351.6+/-28.2 ms for grade I, 361.9+/-38.3 ms for grade II, 362.1+/-67.7 ms for grade III, and 297.8+/-54.1 ms for grade IV according to arthroscopic Outerbridge classification. All cases, that demonstrated decrease of T1 values on dGEMRIC (ROI2), showed abnormal arthroscopic or direct viewing findings. The ratio (ROI3/ROI2) in cases of only slight damage classified as Outerbridge grade I (6 cases) was an average of 1.04+/-0.02 and was 1.0 or greater in all cases, thereby indicating well-defined contrast with the surrounding cartilage. The diagnosis of damage in articular cartilage was possible in all 16 cases with radiographic K-L grade I on dGEMRIC, while the intensity changes were not found in 10 of 16 cases on PDWI. The dGEMRIC with a single-dose would be useful on a diagnosis of the area demonstrating early relative proteoglycan depletion in the articular cartilage of the PF joint prior to any discernible changes in the subchondral bone on X-ray images and exceeds to plain MR images for examining deterioration of articular cartilage.

Stem cell implantation in ischemic mouse heart: a high‐resolution magnetic resonance imaging investigation

Advances in the biology of stem cells have evoked great interest in cell replacement therapies for the regeneration of heart tissue after myocardial infarction. However, results from human trials are controversial, since the destination of the injected cells, their engraftment and their long-term fate have remained unclear. Here we investigate whether transplanted cells can be identified in the intact and lesioned murine myocardium employing high-resolution MRI. Cardiac progenitor cells, expressing the enhanced green fluorescent protein (EGFP), were labeled with ultra-small paramagnetic iron-oxide (USPIO) nanoparticles and transplanted into the intact or injured myocardium of mice. Their precise location was determined with high-resolution MRI and compared with histological tissue sections, stained with Prussian blue for iron content. These experiments showed that iron nanoparticle-loaded cells could be identified at high resolution in the mouse heart. However, ischemic myocardium (after cryoinjury or left coronary artery ligation) was characterized by a signal attenuation similar to that induced by USPIO-labeled cells in T2*-weighted MR images, making detection of labeled stem cells in this area by T2*-sensitive contrast rather difficult. In animals with myocardial injury only, the signal attenuated areas were of the same size in proton density- and T2*-weighted MR images. In injured animals also receiving labeled cells the lesioned area appeared larger in T2*--than in proton density-weighted MR images. This sequence-dependent lesion size change is due to the increased signal loss caused by the iron oxide nanoparticles, most sensitively detectable in the T2*-sensitive images. Thus, using the novel combination of these two parameter weightings, USPIO-labeled cells can be detected at high resolution in ischemic myocardium.

The value of water-excitation 3D FLASH and fat-saturated PDw TSE MR imaging for detecting and grading articular cartilage lesions of the knee.

To evaluate the diagnostic accuracy of water-excitation (WE) 3D FLASH and fat-saturated (FS) proton density-weighted (PDw) TSE MR imaging for detecting, grading, and sizing articular cartilage lesions of the knee. A total of 26 patients underwent MR imaging prior to arthroscopy with the following sequences: (1) WE 3D FLASH: 28/11 ms, scan time: 4 min 58 s, flip angle: 40 degrees; (2) FS PDw TSE: 3433/15 ms, scan time: 6 min 15 s, flip angle: 180 degrees. Grade and size of the detected lesions were quantified and compared with the results of arthroscopy for each compartment. The sensitivity, specificity, positive and negative predictive values, and accuracy for detecting cartilage lesions were 46%, 92%, 81%, 71% and 74% for WE 3D FLASH and 91%, 98%, 96%, 94% and 95% for FS PDw TSE MR imaging. WE 3D FLASH correlated significantly with arthroscopy for grading on the patella ( P<0.0001) and the femoral trochlea ( P=0.02) and for sizing on the femoral trochlea ( P=0.03). FS PDw correlated significantly ( P<0.0001) with arthroscopy for grading and sizing on all compartments. FS PDw TSE is an accurate method for detecting, grading and sizing articular cartilage lesions of the knee and yielded superior results relative to WE 3D FLASH MR imaging.

MR arthrography in chondromalacia patellae diagnosis on a low-field open magnet system

Objective: The purpose of this study was to compare the diagnostic efficacy conventional MRI and MR arthrography (MRA) in the diagnosis of chondromalacia patella (CP) on a low-field open magnet system (LFOMS), correlated with arthroscopy. Subjects and methods: Forty-two patients (50 knees) with pain in the anterior part of the knee were prospectively examined with LFOMS, including T1-weighted, proton density-weighted and T2-weighted sequences. All were also examined T1-weighted MRI after intraarticular injection of dilue gadopentetate dimeglumine. Two observers, who reached a consensus interpretation, evaluated each imaging technique independently. Thirty-six of the 50 facets examined had chondromalacia shown by arthroscopy, which was used as the standard of reference. The sensitivity, specificity and accuracy of each imaging technique in the diagnosis of each stage of CP were determined and compared by using the McNemar two-tailed analysis. Results: Arthroscopy showed that 16 facets were normal. Four (30%) of 13 grade 1 lesions were detected with T1. Four lesions (30%) with T2 and three lesions (23%) with proton-weighted images were detected. Seven (53%) of 13 grade 1 lesions were detected with MRA. Grade 2 abnormalities were diagnosed in two (33%) of six facets with proton density-weighted pulse sequences, two (33%) of six facets with T1-weighted pulse sequences, in three (50%) of six facets with T2-weighted pulse sequences, in five (83%) of six facets with MRA sequences. Grade 3 abnormalities were diagnosed in three (71%) of seven facets with proton density- and T1-weighted images, five (71%) of seven facets with T2-weighted pulse sequences, six (85%) of seven facets with MRA sequences. Grade 4 CP was detected with equal sensitivity with T1-, proton density- and T2-weighted pulse sequences, all showing seven (87%) of the eight lesions. MRA again showed these findings in all eight patients. All imaging techniques were insensitive to grade 1 lesions and highly sensitive to grade 4 lesion, so that no significant difference among the techniques could be shown. Conclusion: All imaging technique studied had high specificity and accuracy in the detection and grading of CP; however, MRA was more sensitive than T1-weighted and proton density-weighted MR imaging on a LFOMS. Although the arthrographic techniques were not significantly better than T2-weighted imaging, the number of false-positive diagnosis was greatest with T2-weighted MRI.

MR imaging features of osteochondritis dissecans of the femoral sulcus.

The objective of this study was to describe the MR imaging features of osteochondritis dissecans of the femoral sulcus, which have not been described previously. Osteochondritis dissecans of the femoral sulcus has been recognized as a unique clinical and radiographic entity, warranting early diagnosis and appropriate treatment. Although this type of osteochondritis dissecans may be inconspicuous on radiography, fast spin-echo proton density-weighted and T2-weighted MR imaging sequences allow evaluation for articular cartilage integrity and lesion stability. Because of the orientation of the femoral sulcus, osteochondritis dissecans involving the femoral sulcus is best evaluated on axial and sagittal images.

Grading articular cartilage of the knee using fast spin-echo proton density-weighted MR imaging without fat suppression.

The objective of this work was to determine the accuracy of fast spin-echo proton density-weighted MR imaging in the evaluation of the articular cartilage of the knee using arthroscopy as a gold standard. We retrospectively reviewed MR images of the knee in 54 patients for whom arthroscopic results were available. All MR imaging studies included fast spin-echo proton density-weighted coronal and axial sequences as part of our routine protocol. Evaluation of the articular surfaces was performed by three independent observers who were unaware of the arthroscopic results. The cartilage surfaces were graded using a 3-point system, and results were compared with arthroscopic findings. Of 324 cartilage surfaces evaluated, arthroscopy showed 241 surfaces as normal, 56 as containing partial-thickness defects, and 27 as containing full-thickness defects. Compared with arthroscopic data, sensitivity of MR imaging for the three reviewers was 59-73.5%; specificity, 86.7-90.5%; positive predictive value, 60.5-72.6%; negative predictive value, 86.0-90.8%; and accuracy, 79.6-86.1%. Interobserver variability for the presence of disease, which was measured using the kappa statistic, was 0.63. Fast spin-echo proton density-weighted MR imaging sequences can be used to evaluate the cartilage of the knee with accuracy comparable to that of previously reported cartilage-specific sequences.