3D DESS Research Articles

Improved 3D DESS MR neurography of the lumbosacral plexus with deep learning and geometric image combination reconstruction.

To evaluate the impact of deep learning (DL) reconstruction in enhancing image quality and nerve conspicuity in LSP MRN using DESS sequences. Additionally, a geometric image combination (GIC) method to improve DESS signals' combination was proposed. Adult patients undergoing 3.0 Tesla LSP MRN with DESS were prospectively enrolled. The 3D DESS echoes were separately reconstructed with and without DL and DL-GIC combined reconstructions. In a subset of patients, 3D T2-weighted short tau inversion recovery (STIR-T2w) sequences were also acquired. Three radiologists rated 4 image stacks ('DESS S2', 'DESS S2 DL', 'DESS GIC DL' and 'STIR-T2w DL') for bulk motion, vascular suppression, nerve fascicular architecture, and overall nerve conspicuity. Relative SNR, nerve-to-muscle, -fat, and -vessel contrast ratios were measured. Statistical analysis included ANOVA and Wilcoxon signed-rank tests. p < 0.05 was considered statistically significant. Forty patients (22 females; mean age = 48.6 ± 18.5years) were enrolled. Quantitatively, 'DESS GIC DL' demonstrated superior relative SNR (p < 0.001), while 'DESS S2 DL' exhibited superior nerve-to-background contrast ratio (p value range: 0.002 to < 0.001). Qualitatively, DESS provided superior vascular suppression and depiction of sciatic nerve fascicular architecture but more bulk motion as compared to 'STIR-T2w DL'. 'DESS GIC DL' demonstrated better nerve visualization for several smaller, distal nerve segments than 'DESS S2 DL' and 'STIR-T2w DL'. Application of a DL reconstruction with geometric image combination in DESS MRN improves nerve conspicuity of the LSP, especially for its smaller branch nerves.

Patterns of variation among baseline femoral and tibial cartilage thickness and clinical features: Data from the osteoarthritis initiative

ObjectiveTo employ novel methodologies to identify phenotypes in knee OA based on variation among three baseline data blocks: 1) femoral cartilage thickness, 2) tibial cartilage thickness, and 3) participant characteristics and clinical features. MethodsBaseline data were from 3321 Osteoarthritis Initiative (OAI) participants with available cartilage thickness maps (6265 knees) and 77 clinical features. Cartilage maps were obtained from 3D DESS MR images using a deep-learning based segmentation approach and an atlas-based analysis developed by our group. Angle-based Joint and Individual Variation Explained (AJIVE) was used to capture and quantify variation, both shared among multiple data blocks and individual to each block, and to determine statistical significance. ResultsThree major modes of variation were shared across the three data blocks. Mode 1 reflected overall thicker cartilage among men, those with higher education, and greater knee forces; Mode 2 showed associations between worsening Kellgren-Lawrence Grade, medial cartilage thinning, and worsening symptoms; and Mode 3 contrasted lateral and medial-predominant cartilage loss associated with BMI and malalignment. Each data block also demonstrated individual, independent modes of variation consistent with the known discordance between symptoms and structure in knee OA and reflecting the importance of features such as physical function, symptoms, and comorbid conditions independent of structural damage. ConclusionsThis exploratory analysis, combining the rich OAI dataset with novel methods for determining and visualizing cartilage thickness, reinforces known associations in knee OA while providing insights into the potential for data integration in knee OA phenotyping.

PREVALENCE OF STRUCTURAL LESIONS AND OSTEOARTHRITIS IN FEMOROTIBIAL JOINTS OF ASYMPTOMATIC PARTICIPANTS FROM THE LAUSANNE KNEE STUDY

Structural lesions of the cartilage, menisci, and bone are prevalent on knee MRIs in the asymptomatic population. The presence of such lesions may lead to the diagnosis of osteoarthritis (OA) according to imaging criteria. The prevalence of OA at imaging may depend on the definition criteria used (radiographic vs. MRI criteria). 1) To determine the prevalence of structural lesions of the femorotibial joint in two groups of young and older asymptomatic participants with healthy knees from the Lausanne Knee Study (LKS). 2) To determine the prevalence of OA in that population using radiographic and MRI definitions of OA. Asymptomatic volunteers were prospectively enrolled in this IRB-approved HIPPA-compliant study. Inclusion criteria: age between18-35 or 45-70 years, no knee symptoms in the past 12 months, no history of severe lower limb injury requiring surgery or not, no impairment that might affect gait, BMI≤30. All participants (n=430, 47.8 years ±16.17 (SD), range 18-70 y, 192 (44.6%) male) underwent a clinical evaluation, including KOOS and WOMAC scores to evaluate pain and knee function, radiographic imaging (weight-bearing Schuss and lateral radiographs of both knees, full spine and lower extremity weight-bearing low dose 3D biplanar radiographs (EOS)), and 3T MRI of a randomly selected knee. MRI protocol included 2D fat-suppressed FSE IW images (sagittal, coronal, and transverse planes), isotropic 3D DESS, high-resolution 3D T1. One musculoskeletal radiologist with 6 years of experience graded radiographs (KL score) and knee MRIs for all structural lesions included in the MOAKS criteria. For this study, only femorotibial compartments will be presented. OA was defined as a KL score≥2 at radiography, or using the criteria proposed by Hunter et al (2011) at MRI. There were 137 participants in the young (Y) (26.2y±4.7; 65 male (47.4%)) and 293 in the older (O) group (57.9y±7.23; 127 male (43.3%)). Participants had no knee pain or functional impairment (average KOOS 97.6±2.51 vs 97.2±3.78 in Y vs O group (p=0.26); average WOMAC 97.8±5.48 vs 96.7±8.23 in Y vs O group (p=0.16)). Structural lesions were highly prevalent in the femorotibial joints (decreasing order of prevalence): 190 (44.2%) cartilage damage (7 vs 183 in Y vs. O, p<10−5), 132 (30.7%) BML (5 vs 127 in Y vs. O, p<10−5), 111 (25.8%) meniscal damage (2 vs 109/ in Y vs. O, p<10−5), 110 (25.6%) had peri-articular cysts (13 vs 97 in Y vs. O, p<10−5), 104 (24.2%) participants had osteophytes (3 vs 101/ in Y vs. O, p<10−5), 68 (15.8%) Hoffa synovitis (3 vs 65 in Y vs. O, p<10−5), 38 (8.8%) synovitis/effusion (3 vs 35 in Y vs. O, p<10−3), and 17 (4%) had loose bodies (1 vs 16 in Y vs. O, p=0.019). 76 (17.7%) participants (1 young) had radiographic OA (60 KL2; 16 KL3; 0 KL4), while 24 (5.6%) participants (all from the older group) had femorotibial OA based on MRI criteria, 198 (46%) had normal MRI, and 208 (48.4%) had structural lesions of variable severity that did not fulfill MRI criteria of OA. In a cohort of 430 asymptomatic volunteers with clinically healthy knees, structural lesions were present in up to 54% of femorotibial joints, with their prevalence increasing with age. The prevalence of OA at imaging in healthy knees may be high and depends on the criteria used (prevalence of 5.6% vs. 17.7% when using MRI vs. radiographic criteria).

MENISCAL EXTRUSION IN ASYMPTOMATIC KNEES: THE 3MM CUTOFF MUST BE REVISITED

Meniscal extrusion is frequently encountered in OA, and an arbitrary cutoff value of 3 mm is commonly accepted for a significant extrusion of the body of the medial meniscus (MM). Different methods of measurement have also been described. We aim to provide the normal range of MM extrusion in different zones in asymptomatic volunteers without radiographic and/or MRI OA and to compare different measurement methods on coronal and sagittal 2D images to those performed on 3D images in radial planes. This is a post-hoc analysis of knee MRIs of 93 participants (39.6±16.0 years; mean ± SD) with asymptomatic, healthy knees (KOOS score 97.42±3.22 and WOMAC score 97.41±7.54) from the Lausanne Knee Study. Inclusion criteria: age between 18-35 or 45-70 years, no knee symptoms in the past 12 months, no history of severe lower limb injury, no impairment that might affect gait, BMI≤30. Imaging protocol included weight-bearing Schuss and lateral radiographs of both knees and 3T MRI of a randomly selected knee. MRI protocol included 2D fat-suppressed FSE IW images (sagittal, coronal, and transverse planes), isotropic 3D DESS, and high-resolution 3D T1. One radiologist measured the maximal extrusion of the MM in the radial plane using 3D FSE T1 images in 4 anatomical subregions: zones II-a (anterior), II-b (anteromedial), III (medial), and IV (posterior). Measurements were also performed on coronal and sagittal 2D images using two different methods: on the image where the maximal extrusion was seen (methodMax) and on an image selected based on anatomical landmarks (methodLandmark). Another musculoskeletal radiologist graded knee MRIs for all structural lesions included in the MOAKS criteria. In addition, meniscal extrusion was measured in the sagittal and radial planes to assess interobserver agreement. Measurements on 2D images were compared to those on the radial plane, considered as the reference, using the Bland and Altman method. Sixty-one (65.5%) participants (41.4±16.6 years) who did not have either radiographic OA (KL<2) or MRI-OA (Hunter 2011 criteria) were used to provide the normal range of meniscal extrusion. Among the 61 participants without radiographic or MRI OA, the mean extrusion of MM was 2.39mm±1.41 (zone II-a), 3mm±0.85 (zone II-b), 2.4mm±0.81 (zone III), and 0.3mm±0.9 (zone IV). The 95th percentile of the reference interval for meniscal extrusion in the radial plane was 4.7mm for zone II-a, 4.4mm (zone II-b), 3.7mm (zone III), and 2mm (zone IV). By applying a cutoff value of >3mm for significant meniscal extrusion on measurements in the radial plane, 28/61 (46%) would have been categorized as having extrusion in zone II-b and 12/61 (20%) in zone III. In the coronal plane, 13/61 (21%) or 18/61 (30%) would have been categorized as having meniscal extrusion depending on whether measurements were performed using methodLandmark, or methodMax respectively. In both sagittal and coronal planes, methodMax overestimated meniscal extrusion (95%CI for systematic bias=0.5, 1 in the sagittal plan, 0.1, 0.3 in the coronal plane), while there was no systematic bias for methodLandmark. The width of limits of agreement was similar in both planes and for both methods. Interobserver agreement was moderate for measurements in the radial (ICC=0.67) and sagittal (0.68) plane. This study provided the normal range of meniscal extrusion in asymptomatic knees without radiographic/MRI OA. Applying a 3mm cutoff value for the diagnosis of significant meniscal extrusion would carry a risk to categorize normal menisci as being extruded. Methods of measurement based on anatomical landmarks correlated better with measurements in the radial plane. This work was supported by the Swiss National Science Foundation, Switzerland (SNSF Grant #CRSII5_177155). None to declare. CORRESPONDENCE ADDRESS: [email protected]

Naturally occurring osteochondrosis latens lesions identified by quantitative and morphological 10.5 T MRI in pigs.

Juvenile osteochondritis dissecans (JOCD) is a pediatric orthopedic disorder that involves the articular-epiphyseal cartilage complex and underlying bone. Clinical disease is often characterized by the presence of radiographically apparent osteochondral flaps and fragments. The existence of early JOCD lesions (osteochondrosis latens [OCL] and osteochondrosis manifesta [OCM]) that precede the development of osteochondral flaps and fragments is also well recognized. However, identification of naturally occurring OCL lesions (confined to cartilage) using noninvasive imaging techniques has not yet been accomplished. We hypothesized that 10.5 T magnetic resonance imaging(MRI) can identify naturally occurring OCL lesions at predilection sites in intact joints of juvenile pigs. Unilateral elbows and knees (stifles) were harvested from three pigs aged 4, 8, and 12 weeks, and scanned in a 10.5 T MRI to obtain morphological 3D DESS images, and quantitative T2 and T1ρ relaxation time maps. Areas with increased T2 and T1ρ relaxation times in the articular-epiphyseal cartilage complex were identified in 1/3 distal femora and 3/3 distal humeri and were considered suspicious for OCL or OCM lesions. Histological assessment confirmed the presence of OCL or OCM lesions at each of these sites and failed to identify additional lesions. Histological findings included necrotic vascular profiles associated with areas of chondronecrosis either confined to the epiphyseal cartilage (OCL, 4- and 8-week-old specimens) or resulting in a delay in endochondral ossification (OCM, 12-week-old specimen). Future studies with clinical MR systems (≤7 T) are needed to determine whether these MRI methods are suitable for the in vivo diagnosis of early JOCD lesions in humans.

Can Bone Erosion in Axial Spondyloarthropathy be Detected by Ultrashort Echo Time Imaging? A Comparison With Computed Tomography in the Sacroiliac Joint.

Structural lesion evaluation in axial spondyloarthropathy (SpA) can improve accuracy of diagnosis. However, structural lesions (bone erosions) are difficult to be assessed using conventional MRI compared to computed tomography (CT). To evaluate the diagnostic performance of ultrashort echo time (UTE) for detecting bone erosion in axial SpA compared to T1WI and three-dimensional double-echo steady-state (3D DESS) imaging using CT as the reference standard. Retrospective. Fourteen patients (eight females, 57.1%) and 14 healthy controls (seven females, 50.0%) who underwent sacroiliac (SI) joint MRI and CT. 3 T; TSE T1WI, 3D DESS, 2D UTE. The bilateral SI joints were assessed for bone erosion. Three observers scored bone erosion for all three sequences of MRI. CT was used as the gold standard. Diagnostic confidence in axial SpA was measured based on a four-point confidence score. Correlation of erosion scores between CT and MRI were evaluated using Spearman's correlation test. Sensitivity, specificity, and positive-negative predictive values were calculated. Confidence scores were compared using the Wilcoxon sum rank test. Statistical significance was set at P < 0.05. Compared with erosion scores of CT, the correlation coefficients for each MRI sequence showed significant low-to-high positive correlations (0.39-0.72). UTE imaging showed the highest correlation coefficients for all observers (0.70, 0.72, and 0.67, respectively). The specificity of UTE imaging was equal or higher than those of T1WI and 3D DESS for all observers (0.86 vs. 0.71 vs. 0.57; 0.93 vs. 0.71 vs. 0.57; 0.79 vs. 0.79 vs. 0.43). All observers had the highest confidence in interpreting UTE imaging for detecting bone erosion among the three sequences (3.5, 3.4, and 3.3 for UTE; 3.1, 3.0, and 2.6 for T1WI; and 3.2, 2.7, and 2.4 for DESS). UTE imaging can detect bone erosions in patients with axial SpA and show higher specificity than conventional T1WI and 3D DESS. 4 TECHNICAL EFFICACY: Stage 2.

PREDICTION OF OSTEOPHYTE PROGESSION FROM CLINICAL DATA AND MRI-BASED 3D KNEE MORPHOLOGY

Osteophytes (OSTs) are one of the most prominent radiographical features of knee OA progression. They are strongly associated with presence of pain and often with other symptoms. However, clinical picture of OSTs in OA and their pathophysiology are not well understood. Prior research on predicting OA progression, particularly from the imaging data, has considered TKR, change in KLG, or JSN as the surrogate outcomes. Thus, the feasibility of using individual radiographic features, such as OSTs, as a potential surrogate endpoint has not been investigated. 1) To investigate the predictive power of the commonly available demographic and radiographic variables in prediction of osteophyte progression over 4 years. 2) To develop an MRI-based (3D tissue morphology) end-to-end model for the same task and evaluate its performance and added value. We used the data from the baseline of the OAI. Progression criterion was based on radiographic OARSI grade for OSTs [0-3]. Knees with an increase in OARSI grade in any compartment at the 4-year follow-up were set as progressors – the rest – as non-progressors. We excluded the knees with OARSI grade 3 in all regions, the non-progressors that dropped out before the last visit, and the samples with missing data. Final sample had 4600 knees (2476 subjects), with 2218 progressed and 2382 non-progressed knees. The baseline models were based on Logistic Regression and the following variables: age, sex, BMI, KLG, and OARSI OST grades. The latter were available for FL, FM, TL, and TM. For MRI-based model, we used the validated automatic segmentations by Tack et al. 2021 (Zuse Institute, Berlin, Germany) derived from 3D DESS MRI. The data included the masks for femur, tibia, corresponding cartilage tissues, and menisci. The ROIs were cropped from the images and resampled to resolution of 95x192x140 (pixel spacing 1.1x0.73x0.73mm^3). The model was based on 3D ResNet-10 CNN and trained in two experiments – from bone masks only, and from all the listed tissues. Eventually, the MRI models were also fused with the baseline ones. Here, the predicted probabilities of the MRI model were used as an additional variable for the baseline model. To develop the predictive models, we used 5-fold cross-validation. For model evaluation, we used a hold-out set of 920 knees (443 progressors and 477 non-progressors). Performance of the models were assessed using area under the ROC curve (AUC), and average precision (AP). Over 4 years, OARSI OST grade changes of (1, 2, and 3) were observed, for (20.22, 2.85, 0.37) percent of knees in TM, (12.54, 2.13, 0.24) in TL, (12.82, 1.48, 0.30) in FL, and (17.28, 3.56, 0.76) in FM, respectively. The age, sex, BMI model yielded AUC=0.60[0.56-0.63], AP=0.56[0.51-0.61]. Adding KLG resulted in similar performance as with added OARSI OST grade. The baseline model with both grades was the best -AUC=0.68[0.65-0.71] and AP=0.67[0.62-0.71]. The MRI (CNN) models showed AUC=0.55[0.51-0.58], AP=0.53[0.48-0.57] (bones-only) and AUC=0.58[0.54-0.61], AP=0.55[0.50-0.60] (all tissues). Fusion of the best baseline and MRI models did not further improve the performance. The model based on the clinical data including KLG and OARSI OST grade showed the highest performance in predicting OST progression in 4 years. The imaging biomarkers, automatically extracted from 3D bone, cartilage, and menisci morphology, showed only limited predictive power and did not improve the final performance. Interestingly, the imaging model including cartilage- and menisci-based biomarkers showed higher metrics than bone-only, which may suggest contribution of soft tissue morphology to the progression of OSTs. Supported by the Academy of Finland (334771 & 334773), under the frame of ERA PerMed. Alexander Tack and ZIB for providing the data. CORRESPONDENCE ADDRESS: mitra.daneshmand@oulu.fi

Common patterns of variation between femoral and tibial cartilage maps and baseline features from the osteoarthritis initiative

Common patterns of variation between femoral and tibial cartilage maps and baseline features from the osteoarthritis initiative

Reliability of tibiofemoral contact area and centroid location in upright, open MRI

BackgroundImaging cannot be performed during natural weightbearing in biomechanical studies using conventional closed-bore MRI, which has necessitated simulating weightbearing load on the joint. Upright, open MRI (UO-MRI) allows for joint imaging during natural weightbearing and may have the potential to better characterize the biomechanical effect of tibiofemoral pathology involving soft tissues. However open MRI scanners have lower field strengths than closed-bore scanners, which limits the image quality that can be obtained. Thus, there is a need to establish the reliability of measurements in upright weightbearing postures obtained using UO-MRI.MethodsKnees of five participants with prior anterior cruciate ligament (ACL) rupture were scanned standing in a 0.5 T upright open MRI scanner using a 3D DESS sequence. Manual segmentation of cartilage regions in contact was performed and centroids of these contact areas were automatically determined for the medial and lateral tibiofemoral compartments. Inter-rater, test-retest, and intra-rater reliability were determined and quantified using intra-class correlation (ICC3,1), standard error of measurement (SEM), and smallest detectable change with 95% confidence (SDC95). Accuracy was assessed by using a high-resolution 7 T MRI as a reference.ResultsContact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the medial compartment had ICC3,1 values from 0.95–0.99 and 0.98–0.99 respectively. In the lateral compartment, contact area and centroid location reliability ICC3,1 values ranged from 0.83–0.91 and 0.95–1.00 respectively. The smallest detectable change in contact area was 1.28% in the medial compartment and 0.95% in the lateral compartment. Contact area and centroid location reliability for coronal scans in the medial compartment had ICC3,1 values from 0.90–0.98 and 0.98–1.00 respectively, and in the lateral compartment ICC3,1 ranged from 0.76–0.94 and 0.93–1.00 respectively. The smallest detectable change in contact area was 0.65% in the medial compartment and 1.41% in the lateral compartment. Contact area was accurate to within a mean absolute error of 11.0 mm2.ConclusionsKnee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.

High resolution MRI for quantitative assessment of inferior alveolar nerve impairment in course of mandible fractures: an imaging feasibility study

The purpose of this study was to evaluate a magnetic resonance imaging (MRI) protocol for direct visualization of the inferior alveolar nerve in the setting of mandibular fractures. Fifteen patients suffering from unilateral mandible fractures involving the inferior alveolar nerve (15 affected IAN and 15 unaffected IAN from contralateral side) were examined on a 3 T scanner (Elition, Philips Healthcare, Best, the Netherlands) and compared with 15 healthy volunteers (30 IAN in total). The sequence protocol consisted of a 3D STIR, 3D DESS and 3D T1 FFE sequence. Apparent nerve-muscle contrast-to-noise ratio (aNMCNR), apparent signal-to-noise ratio (aSNR), nerve diameter and fracture dislocation were evaluated by two radiologists and correlated with nerve impairment. Furthermore, dislocation as depicted by MRI was compared to computed tomography (CT) images. Patients with clinically evident nerve impairment showed a significant increase of aNMCNR, aSNR and nerve diameter compared to healthy controls and to the contralateral side (p < 0.05). Furthermore, the T1 FFE sequence allowed dislocation depiction comparable to CT. This prospective study provides a rapid imaging protocol using the 3D STIR and 3D T1 FFE sequence that can directly assess both mandible fractures and IAN damage. In patients with hypoesthesia following mandibular fractures, increased aNMCNR, aSNR and nerve diameter on MRI imaging may help identify patients with a risk of prolonged or permanent hypoesthesia at an early time.

MRI of the inferior alveolar nerve and lingual nerve-anatomical variation and morphometric benchmark values of nerve diameters in healthy subjects.

Since MRI using dedicated imaging sequences has recently shown promising results in direct visualization of the inferior alveolar nerve (IAN) and the lingual nerve (LN) with high spatial resolution, the aim of this study was to generate suitable standard specifications to reliably depict the IAN and LN in MRI and to delineate the anatomy and its variants of these nerves in healthy subjects. Thirty healthy volunteers were examined on a 3-T scanner (Elition, Philips Healthcare, Best, the Netherlands). The sequence protocol consisted of 3D STIR, 3D DESS, and 3D T1 FFE "black bone" sequences. The study reconfirmed a good feasibility of direct visualization of proximal and peripheral portions of the IAN and of the proximal course of the LN. The STIR sequence showed the highest apparent signal to noise ratio (aSNR) and best apparent nerve-muscle contrast to noise ratio (aNMCNR) for IAN and for the LN. The applied MRI sequences allowed to differentiate the tissue composition of the neurovascular bundle inside the mandibular canal. Dedicated MRI sequence protocols proved effectively to detect the IAN and LN and their course in healthy volunteers. The tissue composition of the mandibular neurovascular bundle was conclusively distinguishable as was the varying topography inside multiple bony channels. The presented data on the precise and valid visualization of the IAN and LN have clinical implications in respect to local anesthesia prior to dental treatments in the mandible but also regarding surgical procedures and implant insertion in the molar region.

Quantitative measurement of cartilage volume is possible using two-dimensional magnetic resonance imaging data sets

3D Magnetic resonance imaging (MRI) scans are generally used for quantitative cartilage measurements in knee osteoarthritis. However, a great deal of MRI data is from 2D scans, often thought to be unsuitable for quantitative cartilage assessment. The goal of our study was to demonstrate that mLACS, a modified version of the Local Area Cartilage Segmentation (LACS) method, could be used to measure cartilage volume on 2D MRI images. We studied 301 randomly selected subjects from the OA Biomarkers Consortium FNIH Study, a nested case-control study within the Osteoarthritis Initiative (OAI). The study comprised four subgroups based on radiographic and pain progression. We compared mLACS applied to 2D TSE scans to LACS on 3D DESS data. The Pearson's correlation coefficient was used to establish agreement between LACS and mLACS, standardized response means (SRMs) for responsiveness, and intra-class correlation coefficients (ICCs) to measure reader precision. Logistic regression in a case/control analysis was used to compare the clinical validity between the two methods. We found R2=0.76 for the correlation between LACS and mLACs. For LACS, the responsiveness was SRM=0.49 compared to 0.39 for mLACS. The odds ratios (OR) for the primary case/control analyses were 1.62 for LACS and 1.78 for mLACS. The intra and inter reader reproducibility values for mLACS were ICC=0.90 and 0.86, respectively. This study has demonstrated that a reproducible, responsive, and clinically valid quantitative measurement of cartilage volume can be made using 2D TSE scans with a modest loss of responsiveness compared to 3D scans.

Longitudinal survey for high density mineralised protrusions identified by 3D dess MRI in patients of the osteoarthritis initiative

Purpose: The structural and physiological integrity of the bone-cartilage interface is essential to maintaining joint health. Phenomena that disrupt this boundary can compromise whole joint function and are a major factor in the development of osteoarthritis (OA), particularly in the knee. Early diagnosis of such maladies may offer a predictive biomarker of joint destruction. Microcracks in the subchondral bone plate including the articular calcified cartilage (ACC) are in some cases repaired with a high density mineralised infill material. This material may also extend from the mineralising front into hyaline articular cartilage (HAC) as a high density mineralised protrusion (HDMP). Such features are likely to impair biomechanical performance of surrounding tissues. Their formation can occur in the absence of symptomatic OA and they are potentially a primary cause of OA. Recent reports have confirmed the presence of HDMPs in human ex- and in-vivo knee joints and their detectability with clinical MRI. Here we present the first longitudinal MRI study prospecting for HDMPs in the human knee. Methods: Twenty-one patients were selected from the osteoarthritis initiative (OAI) progression cohort for whom bilateral knee MRI data were available at five consecutive annual visits. Sagitally-acquired dual echo steady state MRI images were assessed for the presence of HDMP-like features at baseline. Incidences were recorded and categorised to one of six regions according to bone and laterality: medial femoral condyle (MFC), lateral femoral condyle (LFC), intercondylar fossa of femur (ICF), medial tibial condyle (MTC), lateral tibial condyle (LTC) and intercondylar ridge of tibia (ICT). Imaging data from follow-up visits were used to monitor the development of features over time. Results: Seventeen patients were found to possess MRI features identified as HDMPs in at least one knee with incidence being unilateral in 5 and bilateral in 12 cases. A total of 58 features were found, ranging from 1 to 5 in a single joint. Features were found in all six regions of the knee joint but distribution between regions was inequitable with 73% being located somewhere on the femur (ICF = 36%; LFC = 25%; MFC = 12%) and only 27% on the tibia (LTC = 23%; MTC = 2%; ICT = 2%). Of those HDMPs identified at baseline, the percentage still present at each subsequent annual visit was 96, 90, 85 and 81, respectively. Morphology of those still visible varied greatly; some remained similar in appearance while others altered substantially, for example, changing in size and shape. Some appeared to have fragmented, forming clusters within HAC. Figure 1 shows an example of a HDMP located on the articular surface of the medial femoral condyle. The material extends from the subchondral bone surface initially. It can be seen breaking away and moving gradually through HAC over time. Conclusions: Observation of features in regions of high mechanical stress and noting their disappearance over time is suggestive of a role in arthropathy. Fine particles of fragmented HDMP may abrade HAC and damage surrounding tissue. The potential for mineral features to fragment may account for apparent clustering of features over time, or they may be discrete incidences. Longevity of features throughout the study duration suggests fragmentation is slow and not guaranteed. Disappearance may indicate destruction or may be caused by average effects. The lower proportion of HDMPs in tibiae may indicate the bone is less susceptible to HDMP formation, or they may be shorter lived. The appearances of HDMPs in clinical scans were consistent with reported ex-vivo studies. Clinical DESS yields high contrast between signal intensities of mineral (low yield) and HAC (high yield) and the features described should be considered a potential imaging biomarker for the prediction of joint destruction in some forms of OA.

The difference between the medial and lateral posterior tibial slope is associated with greater internal tibial rotation

Aims and Objectives: The objective of this study was to investigate the effect of lateral and medial posterior tibial slope (PTS) and meniscal slope (PMS) on in-vivo anterior tibial translation (ATT) and internal tibial rotation (IR) during downhill running on the healthy contralateral knee twenty-four months after ACL reconstruction. Materials and Methods: Forty-two individuals (twenty-six males; mean age 21.2 ± 6.9 years) who underwent unilateral ACL reconstruction were included in this study. Morphologic parameters were measured on 3 T magnetic resonance images (MRI) using the 3D DESS sequence on the ACL reconstructed and healthy contralateral knee. Lateral and medial PTS and PMS were measured according to the method described by Hudek et al. Briefly, the tibial shaft axis was determined by connecting the centroids of two circles fitting the tibial shaft on the central sagittal MRI slice. The PTS and PMS were determined by the angle between the tibial shaft axis and the line connecting the two most proximal anterior and posterior subchondral bone and meniscal points in the center of each joint compartment. Three-dimensional in-vivo kinematics data were acquired using dynamic stereo x-ray during downhill running (3.0 m/s, 10° slope) at 150 Hz twenty-four months after unilateral ACL reconstruction. A multiple regression analysis was performed (p < .05). Results: The lateral and medial PTS and PMS as well as the differences between the medial and lateral compartment slopes were not significantly related to ATT in the healthy contralateral knees twenty-four months after ACL reconstruction (p > .05). The lateral and medial PTS and PMS were not significantly related to peak internal tibial rotation (p > .05). However, the difference between the medial and lateral PTS as well as PMS was associated with greater internal tibial rotation (PTS: b=1.55, p < .001; PMS: b = .71, p = .02). Conclusion: The most important finding of the present study is that the difference between the medial and lateral posterior tibial and meniscal slope are related to in-vivo internal tibial rotation during downhill running. ATT was not significantly influenced by the tibial bony and meniscal morphology. Taking into account the results of the present study, the difference between the medial and the lateral PTS and PMS may contribute to IR when an ACL injury occurs. However, the analyzed movement was a straight-ahead run without any cutting or pivoting maneuvers commonly related to ACL tears. In such motion patterns, the correlations may be even stronger compared to the results of this study.

An 8-channel transceiver 7-channel receive RF coil setup for high SNR ultrahigh-field MRI of the shoulder at 7T.

In this work, we present an 8-channel transceiver (Tx/Rx) 7-channel receive (Rx) radiofrequency (RF) coil setup for 7 T ultrahigh-field MR imaging of the shoulder. A C-shaped 8-channel Tx/Rx coil was combined with an anatomically close-fitting 7-channel Rx-only coil. The safety and performance parameters of this coil setup were evaluated on the bench and in phantom experiments. The 7 T MR imaging performance of the shoulder RF coil setup was evaluated in in vivo measurements using a 3D DESS, a 2D PD-weighted TSE sequence, and safety supervision based on virtual observation points. Distinct SNR gain and acceleration capabilities provided by the additional 7-channel Rx-only coil were demonstrated in phantom and in vivo measurements. The power efficiency indicated good performance of each channel and a maximum B1+ of 19 μT if the hardware RF power limits of the MR system were exploited. MR imaging of the shoulder was demonstrated with clinically excellent image quality and submillimeter spatial resolution. The presented 8-channel transceiver 7-channel receive RF coil setup was successfully applied for in vivo 7 T MRI of the shoulder providing a clear SNR gain vs the transceiver array without the additional receive array. Homogeneous images across the shoulder region were obtained using 8-channel subject-specific phase-only RF shimming.

Posterior Tibial Subchondral Bone and Meniscal Slope Correlate with In Vivo Internal Tibial Rotation

Objectives:Increased posterior tibial slope (PTS) results in an anteriorly directed force on the knee and is associated with a high-grade pivot shift. However, all published articles on this topic draw conclusions based on static measurements, while no study investigated the role of the PTS and posterior meniscal slope (PMS) on in vivo knee kinematics. Therefore, the objective of this study was to correlate the lateral and medial PTS and PMS with in vivo anterior tibial translation (ATT) and internal tibial rotation during level walking and downhill running on both the ACL reconstructed and healthy knees six months after index surgery. It was hypothesized that an increased lateral PTS and lateral PMS are associated with increased ATT and internal tibial rotation.Methods:Forty-two individuals (twenty-six males; mean age 21.2 ± 6.9 years) who underwent unilateral ACL reconstruction were included in this study. Morphologic parameters were measured on 3T magnetic resonance images (MRI) using the 3D DESS sequence on the ACL reconstructed and healthy contralateral knee. Lateral and medial PTS and PMS were measured according to the method described by Hudek et al. Briefly, the tibial shaft axis was determined by connecting the centroids of two circles fitting the tibial shaft on the central sagittal MRI slice. The PTS and PMS were determined by the angle between the tibial shaft axis and the line connecting the two most proximal anterior and posterior subchondral bone and meniscal points in the center of each joint compartment. Three-dimensional in vivo kinematics data were acquired using dynamic stereo X-ray during level walking (1.3 m/s) at 100 Hz and downhill running (3.0 m/s, 10° slope) at 150 Hz, six months after unilateral ACL reconstruction. Correlations between bone morphology and dynamic kinematics were evaluated using Spearman´s Rho. The significance level was set at p < .05.Results:In ACL intact knees, ATT did not correlate significantly with PTS and PMS (all p ≥ .264; Table 1). Internal tibial rotation was associated with higher posterior slopes in the lateral knee compartment. Larger differences between lateral and medial PTS and PMS were significantly correlated with increased internal tibial rotation (all ≤ .010), while medial PTS and PMS did not correlate with tibial rotation (all p ≥ .457). In ACL reconstructed knees ATT was positively correlated with an increased lateral PMS during level walking (p = .016). ACL reconstructed knees were found to have greater internal tibial rotation with larger lateral compartment slopes as well as with larger lateral-medial differences for PTS and PMS during level walking (all p ≤ .035).Conclusion:The most important finding of the present study is that both lateral PTS and PMS are related to dynamic, functional in vivo kinematics, especially internal tibial rotation. ATT was only associated with lateral PMS in ACL reconstructed knees. Taking into account the results of the present study, the lateral PTS and PMS and the slope differences between the lateral and medial joint compartment may contribute to internal rotation when an ACL injury occurs. However, the analyzed movement was a straight-ahead walk and run without any cutting or pivoting maneuvers commonly related to ACL tears. In such motion patterns, the correlations may be even stronger compared to the results of this study. However, this novel study is the first to assess the relationship between articulating surface morphology and in vivo functional movement.

Three-dimensional isotropic magnetic resonance imaging can provide a reliable estimate of the native anterior cruciate ligament insertion site anatomy.

This study quantified the error in anterior cruciate ligament (ACL) insertion site location and area estimated from three-dimensional (3D) isotropic magnetic resonance imaging (MRI) by comparing to native insertion sites determined via 3D laser scanning. Isotropic 3D DESS MRI was acquired from twelve fresh-frozen, ACL-intact cadaver knees. ACL insertion sites were manually outlined in each MRI slice, and the resulting contours combined to determine the 3D insertion site shape. Specimens were then disarticulated, and the boundaries of the ACL insertion sites were digitized using a high-accuracy laser scanner. MRI and laser scan insertion sites were co-registered to determine the percent overlapping area and difference in insertion centroid location. Femoral ACL insertion site area averaged 112.7±17.9mm2 from MRI and 109.7±10.9mm2 from laser scan (p=0.345). Tibial insertion area was 134.7±22.9mm2 from MRI and 135.2±15.1mm2 from laser scan (p=0.881). Percentages of overlapping area between modalities were 82.2±10.2% for femurs and 81.0±9.0% for tibias. The root-mean-square differences for ACL insertion site centroids were 1.87mm for femurs and 2.49mm for tibias. The MRI-estimated ACL insertion site centroids were biased on average 0.6±1.6mm proximally and 0.3±1.9mm posteriorly for femurs, and 0.3±1.1mm laterally and 0.5±1.5mm anteriorly for tibias. Errors in ACL insertion site location and area estimated from 3D-MRI were determined via comparison with a high-accuracy 3D laser scanning. Results indicate that MRI can provide estimates of ACL insertion site area and centroid location with clinically applicable accuracy. MRI-based assessment can provide a reliable estimate of the native ACL anatomy, which can be helpful for surgical planning as well as assessment of graft tunnel placement.

Accurate Fully Automated 4D Segmentation of Osteoarthritic Knee MRI

Purpose: A method for 4D (3D+time) segmentation of bone and cartilage surfaces of the knee joint imaged by magnetic resonance (MR) is reported. Accurate segmentation is necessary to understand osteoarthritis (OA) disease processes and quantify the efficacy of DMOAD (disease-modifying OA drug) drug trials. Manual segmentation is tedious, time-consuming (several hours per joint) and irreproducible. We have previously reported an automated 3D approach based on layered optimal graph segmentation of multiple objects and surfaces (LOGISMOS). This study extends 3D LOGISMOS to 3D+time (4D) LOGISMOS to simultaneously segment four cartilage and bone surfaces (femur, tibia) in longitudinal sequences of follow-up MRI's. The key benefit of using our automated 4D LOGISMOS method is that information from all time points of the temporal sequence contributes to the single optimal solution that utilizes temporal and spatial context between adjacent time points. Methods: Our 4D LOGISMOS approach consists of two major steps: a) Constraining topological relationships between identical pre-segmentation meshes between time-points using rigid registration, and b) enforcing physiologically permissible maximum changes between time-points by introducing inter-time point graph arcs that longitudinally link the temporally corresponding locations of the respective bones and cartilages of the femur and tibia. Robust hierarchical random-forest classifiers were used to derive cartilage cost functions trained using segmentation examples. Once segmented, automated sub-plate analysis was used to identify segmentation accuracy in medial/lateral regions of the femur (cMF/cLF) and tibia (cMT/cLT). To assess segmentation accuracy, 54 patients at baseline and 12-month follow-up visits from the OAI (Osteoarthritis Initiative) progressive cohort were analyzed (108 3D MR DESS datasets) and compared with the manually-traced independent standard (IS). To assess the temporal consistency of the segmentations, a large sub-cohort of 399 patients with five yearly follow-ups (baseline, 12, 24, 36, 48 month; 1,995 DESS MRI’s) were analyzed to show the benefits of 4D over 3D analysis. Since no independent standard was available for this cohort, consistency assessment was based on a hypothesis that cartilage thickness losses over the five-year period would be monotonically decreasing and that this hypothesis can be tested using longitudinal cartilage thickness correlation coefficient R. Higher occurrence of analyses satisfying this hypothesis indicates a larger success rate – histograms of R-values were analyzed to determine whether 4D LOGISMOS outperformed the 3D approach. Results: Tables show signed and unsigned cartilage border positioning errors using the 4D and 3D methods at baseline and 12 months with green boxes representing significant improvement while red boxes indicate a worsened performance. Analyzing histograms of R-values for different sub-plates showed a significantly (p<0.05) better performance of the 4D LOGISMOS when compared to that of 3D.Table 1Baseline signed and unsigned cartilage surface positioning errors between 4D and 3D LOGISMOS on the major femoral and tibial sub-plates.Table 212-month signed and unsigned cartilage surface positioning errors comparison between 4D and 3D LOGISMOS on the major femoral and tibial sub-plates.Table 212-month signed and unsigned cartilage surface positioning errors comparison between 4D and 3D LOGISMOS on the major femoral and tibial sub-plates. Conclusions: The proposed 4D LOGISMOS segmentation algorithm outperformed the 3D approach and demonstrated the benefits of using temporal contextual information in studies with multiple follow-up MRIs. Temporal-context aware image segmentation techniques offer a significant improvement of segmentation performance in hard-to-analyze longitudinal studies of OA progression.

Rapid High-resolution, Self-registered, Dual Lumen-contrast MRI Method for Vessel-wall Assessment in Peripheral Artery Disease:: A Preliminary Investigation

Contrast-enhanced angiographic evaluation by magnetic resonance imaging (MRI) and computed tomography (CT) is the reference standard for assessing peripheral artery disease (PAD). However, because PAD and diabetes often coexist, the prevalence of renal insufficiency is a major challenge to contrast-based angiography. The objective of this work is to describe and demonstrate a new application of three-dimensional double-echo steady-state (3D DESS) as a noncontrast vascular MRI method for evaluating peripheral atherosclerosis at 3 Tesla (3T). A water-selective 3D DESS pulse sequence was designed to simultaneously collect two steady-state free-precession signals (free induction decay and Echo) yielding "black blood" (BB) and "gray blood" (GB) images. For completeness Bloch equation, simulations were performed to characterize DESS signals of various tissues including blood at different velocities and to assess two healthy subjects for the purpose of pulse sequence optimization. Exploratory studies were performed as an add-on protocol to an existing study involving patients with PAD. To evaluate the method's specificity for detecting calcification, images from select patients were compared against CT angiography. Simulations agreed qualitatively with in vivo images supporting DESS' potential for generating distinct lumen contrast (GB vs BB). Lesions representing calcium were easily identifiable on the basis of signal void occurring on both image types and were confirmed by CT angiography. Further, BB allowed visualization of stent restenosis, and data suggest its ability to visualize acute thrombus by virtue of T2 weighting. Preliminary investigation and results suggest noncontrast 3D DESS to have the potential to improve diagnosis of PAD patients by providing detailed structural assessment of vessel-wall architecture.

Quantitative Biomedical Imaging: Techniques and Clinical Applications.

Quantitative Biomedical Imaging: Techniques and Clinical Applications.