High-grade intramuscular tendon disruption in acute hamstring injury and return to play in Australian Football players.

BACKGROUND: Recent literature has reported intramuscular tendon (IT) disruption is associated with longer return to play (RTP) following acute hamstring injury. OBJECTIVES: Investigate whether an increase in hamstring injury severity involving high-grade IT disruption and proximal injury location is associated with longer RTP times in elite Australian Rules Football (AFL) players. METHODS: Hamstring injury records and RTP times from one professional AFL club were obtained over six seasons. MRI of injuries was retrospectively reviewed by a musculo-skeletal radiologist blinded to RTP information. A simplified four-grade classification of acute hamstring injuries was developed based on IT disruption severity and proximodistal injury location. MR0 had no observable MRI tissue damage; MR1 involved muscle-tendon junction, myofascial and low-grade IT injuries; MR2 involved distal and/or single muscle high-grade IT injuries, and MR3 involved high-grade IT injuries of the proximal biceps femoris (BF) IT with concomitant injury to BF+ semitendinosus muscles. RESULTS: Forty-one injuries were available for analysis. Median RTP times were as follows: MR0, 14 days; MR1, 21 days; MR2, 35 days; and MR3, 88 days. For MRI-positive injuries (MR1, MR2, MR3), there was a significant difference in the distributions of RTP, with increased injury severity associated with increased RTP times (P < .001). The distributions of RTP were significantly different between MR1 vs MR2 (P = .008), MR1 vs MR3 (P = .002), and MR2 vs MR3 (P = .012). CONCLUSION: In elite AFL players, acute hamstring injuries with high-grade IT disruption identified on MRI were associated with increased times to RTP compared to injuries with low-grade or no IT disruption.

An open 8-channel parallel transmission coil for static and dynamic 7T MRI of the knee and ankle joints at multiple postures.

PURPOSE: We present the initial in vivo imaging results of an open architecture eight-channel parallel transmission (pTx) transceive radiofrequency (RF) coil array that was designed and constructed for static and dynamic 7T MRI of the knee and ankle joints. METHODS: The pTx coil has a U-shaped dual-row configuration (200 mm overall length longitudinally) that allows static and dynamic imaging of the knee and ankle joints at various postures and during active movements. This coil structure, in combination with B1 shimming, allows flexible configuration of B1 transmit profiles, with good homogeneity over 120-mm regions of interest. This coil enabled high-resolution gradient echo (e.g., 3D dual-echo steady state [DESS] and 3D multiecho data image combination [MEDIC]) and turbo spin echo (TSE) imaging (e.g., with proton density weighting [PDw], PDw with fat saturation, and T1 and T2 weightings) with local RF energy absorption rates well below regulatory limits. RESULTS: High-resolution 2D and 3D image series (e.g., 0.3 mm in-plane resolution for TSE, 0.47 mm isotropic for DESS and MEDIC) were obtained from the knee and ankle joints with excellent tissue contrast. Dynamic imaging during continuous knee and ankle flexion-extension cycles were successfully acquired. CONCLUSION: The new open pTx coil array provides versatility for high-quality static and dynamic MRI of the knee and ankle joints at 7T. Magn Reson Med 79:1804-1816, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Automated analysis of hip joint cartilage combining MR T2 and three-dimensional fast-spin-echo images.

PURPOSE: To validate a fully automated scheme to extract biochemical information from the hip joint cartilages using MR T2 mapping images incorporating segmentation of co-registered three-dimensional Fast-Spin-Echo (3D-SPACE) images. METHODS: Manual analyses of unilateral hip (3 Tesla) MR images of 24 asymptomatic volunteers were used to validate a 3D deformable model method for automated cartilage segmentation of SPACE scans, partitioning of the individual femoral and acetabular cartilage plates into clinically defined sub-regions and propagating these results to T2 maps to calculate region-wise T2 value statistics. Analyses were completed on a desktop computer (∼ 10 min per case). RESULTS: The mean voxel overlap between automated A and manual M segmentations of the cartilage volumes in the (clinically based) SPACE images was 73% (100 × 2|A∩M|/[|A|+|M|]). The automated and manual analyses demonstrated a relative difference error <10% in the median "T2 average signal" for each cartilage plate. The automated and manual analyses showed consistent patterns between significant differences in T2 data across the hip cartilage sub-regions. CONCLUSION: The good agreement between the manual and automatic analyses of T2 values indicates the use of structural 3D-SPACE MR images with the proposed method provides a promising approach for automated quantitative T2 assessment of hip joint cartilages.

Automated anomaly-aware 3D segmentation of bones and cartilages in knee MR images from the Osteoarthritis Initiative.

In medical image analysis, automated segmentation of multi-component anatomical entities, with the possible presence of variable anomalies or pathologies, is a challenging task. In this work, we develop a multi-step approach using U-Net-based models to initially detect anomalies (bone marrow lesions, bone cysts) in the distal femur, proximal tibia and patella from 3D magnetic resonance (MR) images in individuals with varying grades of knee osteoarthritis. Subsequently, the extracted data are used for downstream tasks involving semantic segmentation of individual bone and cartilage volumes as well as bone anomalies. For anomaly detection, U-Net-based models were developed to reconstruct bone volume profiles of the femur and tibia in images via inpainting so anomalous bone regions could be replaced with close to normal appearances. The reconstruction error was used to detect bone anomalies. An anomaly-aware segmentation network, which was compared to anomaly-naïve segmentation networks, was used to provide a final automated segmentation of the individual femoral, tibial and patellar bone and cartilage volumes from the knee MR images which contain a spectrum of bone anomalies. The anomaly-aware segmentation approach provided up to 58% reduction in Hausdorff distances for bone segmentations compared to the results from anomaly-naïve segmentation networks. In addition, the anomaly-aware networks were able to detect bone anomalies in the MR images with greater sensitivity and specificity (area under the receiver operating characteristic curve [AUC] up to 0.896) compared to anomaly-naïve segmentation networks (AUC up to 0.874).

Analysis of cam location characteristics in FAI syndrome patients from 3D MR images demonstrates sex-specific differences.

Cam femoroacetabular impingement (FAI) syndrome is associated with hip osteoarthritis (OA) development. Hip shape features, derived from statistical shape modeling (SSM), are predictive for OA incidence, progression, and arthroplasty. Currently, no three-dimensional (3D) SSM studies have investigated whether there are cam shape differences between male and female patients, which may be of potential clinical relevance for FAI syndrome assessments. This study analyzed sex-specific cam location and shape in FAI syndrome patients from clinical magnetic resonance examinations (M:F 56:41, age: 16-63 years) using 3D focused shape modeling-based segmentation (CamMorph) and partial least squares regression to obtain shape features (latent variables [LVs]) of cam morphology. Two-way analysis of variance tests were used to assess cam LV data for sex and cam volume severity differences. There was no significant interaction between sex and cam volume severity for the LV data. A sex main effect was significant for LV 1 (cam size) and LV 2 (cam location) with medium to large effect sizes (p < 0.001, d > 0.75). Mean results revealed males presented with a superior-focused cam, whereas females presented with an anterior-focused cam. When stratified by cam volume, cam morphologies were located superiorly in male and anteriorly in female FAI syndrome patients with negligible, mild, or moderate cam volumes. Both male and female FAI syndrome patients with major cam volumes had a global cam distribution. In conclusion, sex-specific cam location differences are present in FAI syndrome patients with negligible, mild, and moderate cam volumes, whereas major cam volumes were globally distributed in both male and female patients.

An orthogonal-based decoupling method for MRI phased array coil design.

A new 2 T 3-element orthogonal knee coil array based on the three-dimensional orthogonality principle was designed, constructed and used in a series of pilot magnetic resonance imaging (MRI) studies on a standardized phantom, and human and pig knees. The coil elements within this new coil array are positioned orthogonal to one another allowing problematic mutual coupling effects to be minimized without the use of any passive mutual decoupling schemes. The proposed method is appropriate for the design of transmit, receive and/or transceive radiofrequency (RF) coil arrays for applications in animal/human MRI and spectroscopic studies. Experimental results demonstrated that the 3-element orthogonal knee coil array could be angled arbitrarily, including at 90°, relative to the main static magnetic field (B(0) ) whilst maintaining normal operation with minimal loss of efficiency and functionality. Initial trials with a pig knee specimen further showed that the greatest signal intensity in the patellar ligament (parallel collagen fibres) was observed when the orthogonal knee coil array and the pig knee specimen were angled at ~55° to B(0) , which may have potential uses in magic angle MR applications.

Integrated Multi-Modal Antenna With Coupled Radiating Structures (I-MARS) for 7T pTx Body MRI.

One of the main challenges in ultra-high field whole body MRI relates to the uniformity and efficiency of the radiofrequency field. Although recent advances in the design of RF coils have demonstrated that dipole antennas have a current distribution ideally suited to 7T MRI, they are limited by low isolation and poor robustness to loading changes. Multi-layered and self-decoupled loop coils have demonstrated improved RF performance in these areas at lower field MRI but have not been adapted to dipole designs. In this work, we introduce a novel type of RF antenna consisting of integrated multi-modal antenna with coupled radiating structures (I-MARS), which use layered conductors and dielectric substrates to allow dipole and transmission line modes to co-exist on the same compact dipole-shaped structure. The proposed antenna was optimally designed for 7T MRI and compared with existing dipole antennas using numerical simulations, which showed that I-MARS had similar B1 over specific absorption rate efficiency and superior isolation and stability. Subsequently, a prototype pTx coil array was built and tested in vivo on healthy volunteers at 7T. The articulated, modular construction of the I-MARS coil array allowed it to be readily conformed across multiple body regions (hip, knee, shoulder, lumbar spine and prostate), without requiring modification of the tuning and matching of the antennas. Using RF shimming, uniform and efficient excitation was successfully achieved in the acquisition of high-resolution MR images.

CAN3D: Fast 3D medical image segmentation via compact context aggregation.

Direct automatic segmentation of objects in 3D medical imaging, such as magnetic resonance (MR) imaging, is challenging as it often involves accurately identifying multiple individual structures with complex geometries within a large volume under investigation. Most deep learning approaches address these challenges by enhancing their learning capability through a substantial increase in trainable parameters within their models. An increased model complexity will incur high computational costs and large memory requirements unsuitable for real-time implementation on standard clinical workstations, as clinical imaging systems typically have low-end computer hardware with limited memory and CPU resources only. This paper presents a compact convolutional neural network (CAN3D) designed specifically for clinical workstations and allows the segmentation of large 3D Magnetic Resonance (MR) images in real-time. The proposed CAN3D has a shallow memory footprint to reduce the number of model parameters and computer memory required for state-of-the-art performance and maintain data integrity by directly processing large full-size 3D image input volumes with no patches required. The proposed architecture significantly reduces computational costs, especially for inference using the CPU. We also develop a novel loss function with extra shape constraints to improve segmentation accuracy for imbalanced classes in 3D MR images. Compared to state-of-the-art approaches (U-Net3D, improved U-Net3D and V-Net), CAN3D reduced the number of parameters up to two orders of magnitude and achieved much faster inference, up to 5 times when predicting with a standard commercial CPU (instead of GPU). For the open-access OAI-ZIB knee MR dataset, in comparison with manual segmentation, CAN3D achieved Dice coefficient values of (mean = 0.87 ± 0.02 and 0.85 ± 0.04) with mean surface distance errors (mean = 0.36 ± 0.32 mm and 0.29 ± 0.10 mm) for imbalanced classes such as (femoral and tibial) cartilage volumes respectively when training volume-wise under only 12G video memory. Similarly, CAN3D demonstrated high accuracy and efficiency on a pelvis 3D MR imaging dataset for prostate cancer consisting of 211 examinations with expert manual semantic labels (bladder, body, bone, rectum, prostate) now released publicly for scientific use as part of this work.

Automated 3D Analysis of Clinical Magnetic Resonance Images Demonstrates Significant Reductions in Cam Morphology Following Arthroscopic Intervention in Contrast to Physiotherapy.

Purpose: To obtain automated measurements of cam volume, surface area, and height from baseline (preintervention) and 12-month magnetic resonance (MR) images acquired from male and female patients allocated to physiotherapy (PT) or arthroscopic surgery (AS) management for femoroacetabular impingement (FAI) in the Australian FASHIoN trial. Methods: An automated segmentation pipeline (CamMorph) was used to obtain cam morphology data from three-dimensional (3D) MR hip examinations in FAI patients classified with mild, moderate, or major cam volumes. Pairwise comparisons between baseline and 12-month cam volume, surface area, and height data were performed within the PT and AS patient groups using paired t-tests or Wilcoxon signed-rank tests. Results: A total of 43 patients were included with 15 PT patients (9 males, 6 females) and 28 AS patients (18 males, 10 females) for premanagement and postmanagement cam morphology assessments. Within the PT male and female patient groups, there were no significant differences between baseline and 12-month mean cam volume (male: 1269 vs 1288 mm3, t[16] = -0.39; female: 545 vs 550 mm,3 t[10] = -0.78), surface area (male: 1525 vs 1491 mm2, t[16] = 0.92; female: 885 vs 925 mm,2 t[10] = -0.78), maximum height (male: 4.36 vs 4.32 mm, t[16] = 0.34; female: 3.05 vs 2.96 mm, t[10] = 1.05) and average height (male: 2.18 vs 2.18 mm, t[16] = 0.22; female: 1.4 vs 1.43 mm, t[10] = -0.38). In contrast, within the AS male and female patient groups, there were significant differences between baseline and 12-month cam volume (male: 1343 vs 718 mm3, W = 0.0; female: 499 vs 240 mm3, t[18] = 2.89), surface area (male: 1520 vs 1031 mm2, t(34) = 6.48; female: 782 vs 483 mm2, t(18) = 3.02), maximum-height (male: 4.3 vs 3.42 mm, W = 13.5; female: 2.85 vs 2.24 mm, t(18) = 3.04) and average height (male: 2.17 vs 1.52 mm, W = 3.0; female: 1.4 vs 0.94 mm, W = 3.0). In AS patients, 3D bone models provided good visualization of cam bone mass removal postostectomy. Conclusions: Automated measurement of cam morphology from baseline (preintervention) and 12-month MR images demonstrated that the cam volume, surface area, maximum-height, and average height were significantly smaller in AS patients following ostectomy, whereas there were no significant differences in these cam measures in PT patients from the Australian FASHIoN study. Level of Evidence: Level II, cohort study.

Automated volumetric and statistical shape assessment of cam-type morphology of the femoral head-neck region from clinical 3D magnetic resonance images.

Background: Femoroacetabular impingement (FAI) cam morphology is routinely assessed using manual measurements of two-dimensional (2D) alpha angles which are prone to high rater variability and do not provide direct three-dimensional (3D) data on these osseous formations. We present CamMorph, a fully automated 3D pipeline for segmentation, statistical shape assessment and measurement of cam volume, surface area and height from clinical magnetic resonance (MR) images of the hip in FAI patients. Methods: The novel CamMorph pipeline involves two components: (I) accurate proximal femur segmentation generated by combining the 3D U-net to identify both global (region) and local (edge) features in clinical MR images and focused shape modelling to generate a 3D anatomical model for creating patient-specific proximal femur models; (II) patient-specific anatomical information from 3D focused shape modelling to simulate 'healthy' femoral bone models with cam-affected region constraints applied to the anterosuperior femoral head-neck region to quantify cam morphology in FAI patients. The CamMorph pipeline, which generates patient-specific data within 5 min, was used to analyse multi-site clinical MR images of the hip to measure and assess cam morphology in male (n=56) and female (n=41) FAI patients. Results: There was excellent agreement between manual and CamMorph segmentations of the proximal femur as demonstrated by the mean Dice similarity index (DSI; 0.964±0.006), 95% Hausdorff distance (HD; 2.123±0.876 mm) and average surface distance (ASD; 0.539±0.189 mm) values. Compared to female FAI patients, male patients had a significantly larger median cam volume (969.22 vs. 272.97 mm3, U=240.0, P<0.001), mean surface area [657.36 vs. 306.93 mm2, t(95)=8.79, P<0.001], median maximum-height (3.66 vs. 2.15 mm, U=407.0, P<0.001) and median average-height (1.70 vs. 0.86 mm, U=380.0, P<0.001). Conclusions: The fully automated 3D CamMorph pipeline developed in the present study successfully segmented and measured cam morphology from clinical MR images of the hip in male and female patients with differing FAI severity and pathoanatomical characteristics.

Segmentation of the quadratus lumborum muscle using statistical shape modeling.

PURPOSE: To compare automated segmentation of the quadratus lumborum (QL) based on statistical shape modeling (SSM) with conventional manual processing of magnetic resonance (MR) images for segmentation of this paraspinal muscle. MATERIALS AND METHODS: The automated SSM scheme for QL segmentation was developed using an MR database of 7 mm axial images of the lumbar region from 20 subjects (cricket fast bowlers and athletic controls). Specifically, a hierarchical 3D-SSM scheme for segmentation of the QL, and surrounding psoas major (PS) and erector spinae+multifidus (ES+MT) musculature, was implemented after image preprocessing (bias field correction, partial volume interpolation) followed by image registration procedures to develop average and probabilistic MR atlases for initializing and constraining the SSM segmentation of the QL. The automated and manual QL segmentations were compared using spatial overlap and average surface distance metrics. RESULTS: The spatial overlap between the automated SSM and manual segmentations had a median Dice similarity metric of 0.87 (mean = 0.86, SD = 0.08) and mean average surface distance of 1.26 mm (SD = 0.61) and 1.32 mm (SD = 0.60) for the right and left QL muscles, respectively. CONCLUSION: The current SSM scheme represents a promising approach for future automated morphometric analyses of the QL and other paraspinal muscles from MR images.

Discrete element and finite element methods provide similar estimations for hip joint contact mechanics during walking gait.

Finite element analysis (FEA) provides a powerful approach for estimating the in-vivo loading characteristics of the hip joint during various locomotory and functional activities. However, time-consuming procedures, such as the generation of high-quality FE meshes and setup of FE simulation, typically make the method impractical for rapid applications which could be used in clinical routine. Alternatively, discrete element analysis (DEA) has been developed to quantify mechanical conditions of the hip joint in a fraction of time compared to FEA. Although DEA has proven effective in the estimation of contact stresses and areas in various complex applications, it has not yet been well characterised by its ability to evaluate contact mechanics for the hip joint during gait cycle loading using data from several individuals. The objective of this work was to compare DEA modelling against well-established FEA for analysing contact mechanics of the hip joint during walking gait. Subject-specific models were generated from magnetic resonance images of the hip joints in five asymptomatic subjects. The DEA and FEA models were then simulated for 13 loading time-points extracted from a full gait cycle. Computationally, DEA was substantially more efficient compared to FEA (simulation times of seconds vs. hours). The DEA and FEA methods had similar predictions for contact pressure distribution for the hip joint during normal walking. In all 13 simulated loading time-points across five subjects, the maximum difference in average contact pressures between DEA and FEA was within ±0.06 MPa. Furthermore, the difference in contact area ratio computed using DEA and FEA was less than ±6%.

Automated analysis of immediate reliability of T2 and T2* relaxation times of hip joint cartilage from 3 T MR examinations.

BACKGROUND: Magnetic resonance (MR) T2 and T2* mapping sequences allow in vivo quantification of biochemical characteristics within joint cartilage of relevance to clinical assessment of conditions such as hip osteoarthritis (OA). PURPOSE: To evaluate an automated immediate reliability analysis of T2 and T2* mapping from MR examinations of hip joint cartilage using a bone and cartilage segmentation pipeline based around focused shape modelling. STUDY TYPE: Technical validation. SUBJECTS: 17 asymptomatic volunteers (M: F 7:10, aged 22-47 years, mass 50-90 kg, height 163-189 cm) underwent unilateral hip joint MR examinations. Automated analysis of cartilage T2 and T2* data immediate reliability was evaluated in 9 subjects (M: F 4: 5) for each sequence. FIELD STRENGTH/SEQUENCE: A 3 T MR system with a body matrix flex-coil was used to acquire images with the following sequences: T2 weighted 3D-trueFast Imaging with Steady-State Precession (water excitation; 10.18 ms repetition time (TR); 4.3 ms echo time (TE); Voxel Size (VS): 0.625 × 0.625 × 0.65 mm; 160 mm field of view (FOV); Flip Angle (FA): 30 degrees; Pixel Bandwidth (PB): 140 Hz/pixel); a multi-echo spin echo (MESE) T2 mapping sequence (TR/TE: 2080/18-90 ms (5 echoes); VS: 4 × 0.78 × 0.78 mm; FOV: 200 mm; FA: 180 degrees; PB: 230 Hz/pixel) and a MESE T2* mapping sequence (TR/TE: 873/3.82-19.1 ms (5 echoes); VS: 3 × 0.625 × 0.625 mm; FOV: 160 mm; FA: 25 degrees; PB: 250 Hz/pixel). ASSESSMENT: Automated cartilage segmentation and quantitative analysis provided T2 and T2* data from test-retest MR examinations to assess immediate reliability. STATISTICAL TESTS: Coefficient of variation (CV) and intraclass correlations (ICC2, 1) to analyse automated T2 and T2* mapping reliability focusing on the clinically important superior cartilage regions of the hip joint. RESULTS: Comparisons between test-retest T2 and (T2*) data revealed mean CV's of 3.385% (1.25%), mean ICC2, 1's of 0.871 (0.984) and median mean differences of -1.139ms (+0.195ms). CONCLUSION: The T2 and T2* times from automated analyses of hip cartilage from test-retest MR examinations had high (T2) and excellent (T2*) immediate reliability.

Simultaneous super-resolution and contrast synthesis of routine clinical magnetic resonance images of the knee for improving automatic segmentation of joint cartilage: data from the Osteoarthritis Initiative.

PURPOSE: High resolution three-dimensional (3D) magnetic resonance (MR) images are well suited for automated cartilage segmentation in the human knee joint. However, volumetric scans such as 3D Double-Echo Steady-State (DESS) images are not routinely acquired in clinical practice which limits opportunities for reliable cartilage segmentation using (fully) automated algorithms. In this work, a method for generating synthetic 3D MR (syn3D-DESS) images with better contrast and higher spatial resolution from routine, low resolution, two-dimensional (2D) Turbo-Spin Echo (TSE) clinical knee scans is proposed. METHODS: A UNet convolutional neural network is employed for synthesizing enhanced artificial MR images suitable for automated knee cartilage segmentation. Training of the model was performed on a large, publically available dataset from the OAI, consisting of 578 MR examinations of knee joints from 102 healthy individuals and patients with knee osteoarthritis. RESULTS: The generated synthetic images have higher spatial resolution and better tissue contrast than the original 2D TSE, which allow high quality automated 3D segmentations of the cartilage. The proposed approach was evaluated on a separate set of MR images from 88 subjects with manual cartilage segmentations. It provided a significant improvement in automated segmentation of knee cartilages when using the syn3D-DESS images compared to the original 2D TSE images. CONCLUSION: The proposed method can successfully synthesize 3D DESS images from 2D TSE images to provide images suitable for automated cartilage segmentation.

Quantitative mapping of acute and chronic PCL pathology with 3 T MRI: a prospectively enrolled patient cohort.

BACKGROUND: The diagnosis of incomplete acute and chronic posterior cruciate ligament (PCL) tears can be challenging with conventional magnetic resonance (MR) imaging, particularly for injuries in which the ligament appears continuous as occurs with chronic PCL tears that have scarred in continuity. Quantitative mapping from MR imaging may provide additional useful diagnostic information in these cases. The purpose of this study was to assess the feasibility of quantifying transverse relaxation time (T2) mapping values at 3 Tesla (T) in a prospectively enrolled patient cohort with chronic PCL tears. METHODS: Twelve subjects with acute or chronic functionally torn PCL, confirmed on clinical exam and posterior knee stress radiographs (with 8 mm or more of increased posterior tibial translation), were enrolled prospectively over a span of 4 years (age: 28-52 years, injury occurred 2 weeks to 15 years prior). Unilateral knee MR images were acquired at 3 T, including a multi-echo spin-echo T2 mapping scan in the sagittal plane. For the six subjects with a continuous PCL on MR imaging the PCL was manually segmented and divided into proximal, mid and distal thirds. Summary statistics for T2 values in each third of the ligament were compiled. RESULTS: Across the six patient subjects with a continuous ligament, the mean T2 for the entire PCL was 36 ± 9 ms, with the highest T2 values found in the proximal third (proximal: 41 ms, mid 30 ms, distal 37 ms). The T2 values for the entire PCL and for the proximal third subregion were higher than those recently published for asymptomatic volunteers (entire posterior cruciate ligament: 31 ± 5 ms, proximal: 30 ms, mid: 29 ms, distal: 37 ms) with similar methodology. CONCLUSION: Mean T2 values were quantified for acute and chronic PCL tears in this prospectively enrolled patient cohort and were higher than those reported for asymptomatic volunteers. This novel approach of using quantitative mapping to highlight injured areas of the posterior cruciate ligament has potential to provide additional diagnostic information in the challenging case of a suspected posterior cruciate ligament tear which appears continuous, including chronic tears that have scarred in continuity and may appear intact on conventional magnetic resonance imaging.

A lightweight rapid application development framework for biomedical image analysis.

Biomedical imaging analysis typically comprises a variety of complex tasks requiring sophisticated algorithms and visualising high dimensional data. The successful integration and deployment of the enabling software to clinical (research) partners, for rigorous evaluation and testing, is a crucial step to facilitate adoption of research innovations within medical settings. In this paper, we introduce the Simple Medical Imaging Library Interface (SMILI), an object oriented open-source framework with a compact suite of objects geared for rapid biomedical imaging (cross-platform) application development and deployment. SMILI supports the development of both command-line (shell and Python scripting) and graphical applications utilising the same set of processing algorithms. It provides a substantial subset of features when compared to more complex packages, yet it is small enough to ship with clinical applications with limited overhead and has a license suitable for commercial use. After describing where SMILI fits within the existing biomedical imaging software ecosystem, by comparing it to other state-of-the-art offerings, we demonstrate its capabilities in creating a clinical application for manual measurement of cam-type lesions of the femoral head-neck region for the investigation of femoro-acetabular impingement (FAI) from three dimensional (3D) magnetic resonance (MR) images of the hip. This application for the investigation of FAI proved to be convenient for radiological analyses and resulted in high intra (ICC=0.97) and inter-observer (ICC=0.95) reliabilities for measurement of α-angles of the femoral head-neck region. We believe that SMILI is particularly well suited for prototyping biomedical imaging applications requiring user interaction and/or visualisation of 3D mesh, scalar, vector or tensor data.

Pars interarticularis stress lesions in the lumbar spine of cricket fast bowlers.

PURPOSE: This prospective magnetic resonance (MR) imaging study investigated the development of symptomatic pars lesions in the lumbar spine of adolescent cricket fast bowlers. METHODS: Annual MR examinations of the lumbar spine in male fast bowlers (N = 51) and swimmers (N = 20) without a prestudy history of symptomatic back injury were conducted to identify stress-induced pars injuries over 4 and 2 yr periods, respectively. RESULTS: Symptomatic L4 and L5 pars lesions developed in 11 of 51 and 1 of 51 of the bowlers, respectively. Preexisting L5 lesions were observed in both bowlers (10 of 51) and swimmers (4 of 20). No significant difference existed between the proportion of bowlers and swimmers with preexisting L5 lesions (P = 1.00, Fisher's exact test). In contrast, bowlers had a significantly greater proportion of L4 pars lesions compared with swimmers, with 22% of the bowlers developing L4 injuries during the study, whereas there were no L4 lesions in the swimmers (P = 0.027, Fisher's exact test). The symptomatic L4 lesions in the bowlers developed between 15 and 17 yr of age, and all were unilateral lesions lateralized to the nonbowling-arm side. The MR characteristics of the L4 pars lesions were consistent with a stress fracture through the cortical bone. Of the acquired L4 lesions in the bowlers, 4 of 11 and 7 of 11 developed in individuals with and without preexisting L5 defects, respectively. No significant association existed between the acquired L4 pars lesions and preexisting L5 defects in the bowlers (P = 0.216, Fisher's exact test). CONCLUSION: Fast bowling was directly associated with the development of symptomatic pars lesions of the lumbar spine, particularly unilateral L4 stress lesions, in a significant proportion of the adolescent bowlers examined in this prospective MR study.

Quadratus lumborum asymmetry and L4 pars injury in fast bowlers: a prospective MR study.

PURPOSE: This prospective study examined the association between quadratus lumborum (QL) asymmetry and the development of symptomatic pars interarticularis lesions in the lumbar spine of adolescent cricket fast bowlers. METHODS: Annual magnetic resonance imaging was used to measure QL volume asymmetry and for identifying pars lesions of the lumbar vertebrae in fast bowlers (N=51) and a control group of swimmers (N=18). Manual segmentation of axial images spanning the lumbar spine was performed to calculate percent QL asymmetry relative to the bowling- or throwing- (swimmers) arm side. Asymmetry above 100% indicated a larger QL volume on the bowling- (throwing) arm side. RESULTS: The mean QL asymmetry in bowlers of 110.5% (SD=12.1%) was significantly different from the 96.6% (SD=5.0%) asymmetry in swimmers (t=6.75, P