Texture analysis of vertebral bone marrow using chemical shift encoding-based water-fat MRI: a feasibility study.

This feasibility study investigated the spatial heterogeneity of the lumbar vertebral bone marrow using chemical shift encoding-based water-fat MRI. Acquired texture features like contrast and dissimilarity allowed for differentiation of pre- and postmenopausal women and may serve as imaging biomarkers in the future. INTRODUCTION: While the vertebral bone marrow fat using chemical shift encoding water-fat magnetic resonance imaging (MRI) has been extensively studied, its spatial heterogeneity has not been analyzed yet. Therefore, this feasibility study investigated the spatial heterogeneity of the lumbar vertebral bone marrow by using texture analysis in proton density fat fraction (PDFF) maps. METHODS: Forty-one healthy pre- and postmenopausal women were recruited for this study (premenopausal (n = 15) 30 ± 7 years, postmenopausal (n = 26) 65 ± 7 years). An eight-echo 3D spoiled gradient echo sequence was used for chemical shift encoding-based water-fat separation at the lumbar spine. Vertebral bodies L1 to L5 were manually segmented. Mean PDFF values and texture features were extracted at each vertebral level, namely variance, skewness, and kurtosis, using statistical moments and second-order features (energy, contrast, correlation, homogeneity, dissimilarity, entropy, variance, and sum average). Parameters were compared between pre- and postmenopausal women and vertebral levels. RESULTS: PDFF was significantly higher in post- than in premenopausal women (49.37 ± 8.14% versus 27.76 ± 7.30%, p < 0.05). Furthermore, PDFF increased from L1 to L5 (L1 37.93 ± 12.85%, L2 38.81 ± 12.77%, L3 40.23 ± 12.72%, L4 42.80 ± 13.27%, L5 45.21 ± 14.55%, p < 0.05). Bone marrow heterogeneity based on texture analysis was significantly (p < 0.05) increased in postmenopausal women. Contrast and dissimilarity performed best in differentiating pre- and postmenopausal women (AUC = 0.97 and 0.96, respectively), not significantly different compared with PDFF (AUC = 0.97). CONCLUSION: Conclusively, an increased bone marrow heterogeneity could be observed in postmenopausal women. In the future, texture parameters might provide additional information to detect and monitor vertebral bone marrow alterations due to aging or hormonal changes beyond conventional anatomic imaging.

Feasibility of opportunistic osteoporosis screening in routine contrast-enhanced multi detector computed tomography (MDCT) using texture analysis.

This study investigated the feasibility of opportunistic osteoporosis screening in routine contrast-enhanced MDCT exams using texture analysis. The results showed an acceptable reproducibility of texture features, and these features could discriminate healthy/osteoporotic fracture cohort with an accuracy of 83%. INTRODUCTION: This aim of this study is to investigate the feasibility of opportunistic osteoporosis screening in routine contrast-enhanced MDCT exams using texture analysis. METHODS: We performed texture analysis at the spine in routine MDCT exams and investigated the effect of intravenous contrast medium (IVCM) (n = 7), slice thickness (n = 7), the long-term reproducibility (n = 9), and the ability to differentiate healthy/osteoporotic fracture cohort (n = 9 age and gender matched pairs). Eight texture features were extracted using gray level co-occurrence matrix (GLCM). The independent sample t test was used to rank the features of healthy/fracture cohort and classification was performed using support vector machine (SVM). RESULTS: The results revealed significant correlations between texture parameters derived from MDCT scans with and without IVCM (r up to 0.91) slice thickness of 1 mm versus 2 and 3 mm (r up to 0.96) and scan-rescan (r up to 0.59). The performance of the SVM classifier was evaluated using 10-fold cross-validation and revealed an average classification accuracy of 83%. CONCLUSIONS: Opportunistic osteoporosis screening at the spine using specific texture parameters (energy, entropy, and homogeneity) and SVM can be performed in routine contrast-enhanced MDCT exams.

Cartilage MRI relaxation times after arthroscopic partial medial meniscectomy reveal localized degeneration.

PURPOSE: Little is known about the early changes in cartilage composition and tibiofemoral kinematics following partial meniscectomy. The purpose of this study was to determine the effects of partial meniscectomy on cartilage compositional properties using T1ρ and T2 relaxation time mapping and to assess changes in tibiofemoral kinematics. It is hypothesize that abnormal tibiofemoral kinematics and relaxation time elevation (a reflection of changes in cartilage biochemical composition) in the weight-bearing regions of the knees following meniscectomy will be observed. METHODS: Nine patients (7 males and 2 females; mean age, 48.6 ± 10.8 years; BMI = 27.3 ± 3.8 kg/m(2)) with tears of the posterior horn of the medial meniscus underwent arthroscopic partial meniscectomy. Pre-surgical and 6 months post-surgical MRIs were obtained in all subjects to evaluate cartilage relaxation times and tibiofemoral kinematics. Paired t tests were performed to determine significant changes in cartilage relaxation times from baseline. RESULTS: T1ρ relaxation time in the region of the medial femoral condyle directly adjacent to the resection showed an increase of 7.4% at 6 months (p = 0.02). T2 relaxation times in both the medial and lateral tibial plateaus showed significant elevation at 6 months. Consistent kinematic trends were not found in post-meniscectomized knees. CONCLUSIONS: These results suggest that arthroscopic partial meniscectomy affects the biochemical composition of articular cartilage in the knee in as early as 6 months. The largest responses were observed in the weight-bearing regions and the cartilage immediately adjacent to the resection. This suggests that the loading environment has been altered enough to result in cartilage compositional changes in a very brief period of time following meniscectomy. LEVEL OF EVIDENCE: IV.

Response of knee cartilage T1rho and T2 relaxation times to in vivo mechanical loading in individuals with and without knee osteoarthritis.

OBJECTIVE: The objective of this study was to evaluate the effects of mechanical loading on knee articular cartilage T1ρ and T2 relaxation times in patients with and without osteoarthritis (OA). DESIGN: Magnetic resonance (MR) images were acquired from 137 subjects with and without knee OA under two conditions: unloaded and loaded at 50% body weight. Three sequences were acquired: a high-resolution 3D-CUBE, a T1ρ relaxation time, and a T2 relaxation time sequences. Cartilage regions of interest included: medial and lateral femur (MF, LF); medial and lateral tibia (MT, LT), laminar analysis (superficial and deep layers), and subcompartments. Changes in relaxation times in response to loading were evaluated. RESULTS: In response to loading, we observed significant reductions in T1ρ relaxation times in the MT and LT. In both the MF and LF, loading resulted in significant decreases in the superficial layer and significant increases in the deep layer of the cartilage for T1ρ and T2. All subcompartments of the MT and LT showed significant reduction in T1ρ relaxation times. Reductions were larger for subjects with OA (range: 13-19% change) when compared to healthy controls (range: 3-13% change). CONCLUSIONS: Loading of the cartilage resulted in significant changes in relaxation times in the femur and tibia, with novel findings regarding laminar and subcompartmental variations. In general, changes in relaxation times with loading were larger in the OA group suggesting that the collagen-proteoglycan matrix of subjects with OA is less capable of retaining water, and may reflect a reduced ability to dissipate loads.

Differences between X-ray and MRI-determined knee cartilage thickness in weight-bearing and non-weight-bearing conditions.

OBJECTIVE: Determine the effect of loading upon MRI-based mean medial femorotibial cartilage thickness (mMFT_th) and radiograph-based minimum joint space width (mJSW), and determine loading's effect on the relationship between these measures. METHODS: MRI and radiographs were analyzed of 25 knees in weight-bearing and non-weight-bearing conditions. Eight subjects had a Kellgren-Lawrence (KL) grade of 0, indicating no evidence of radiographic OA. The rest were KL = 2 or KL = 3, indicating mild to moderate OA. The change from unloaded to loaded conditions was calculated. RESULTS: Joint space measures decreased from unloaded to loaded conditions for both radiographs (mJSW = 3.29 mm unloaded to 3.16 mm loaded, P < 0.05) and MRI (mMFT_th = 2.70 mm unloaded to 2.55 mm loaded P < 0.001). The mean absolute difference measured from radiographs was larger for the OA group than the control group, at -0.20 mm for OA vs +0.01 mm for control. Loaded X-ray and loaded MRI joint space values from our study were no better correlated to one another than loaded X-ray and unloaded MRI. CONCLUSION: Knee loading does not add a very significant value to the study of joint space on healthy knees, but loading may play a role in the study of OA knees. Unloaded MRI assessments of cartilage thickness are as correlated to loaded JSW as to loaded MRI measurements. More study is necessary to determine whether loaded MRI adds significant value to the study of OA progression.

ScolioMedIS: web-oriented information system for idiopathic scoliosis visualization and monitoring.

Adolescent idiopathic scoliosis is the most common type of abnormal curvature observed in spine and it progresses rapidly during the puberty period. The most followed clinical way of assessing the spinal deformity is subjective by measuring the characteristic angles of spinal curve from a set of radiographic images. This paper presents a web-based information system (called ScolioMedIS) based on parameterized 3D anatomical models of the spine to quantitatively assess the deformity and to minimize the amount of radiation exposure by reducing the number of radiographs required. The main components of the system are 3D parametric solid model of spine, back surfaces, relevant clinical information and scoliosis ontology. The patient-specific spine model is regenerated from the parametric model and surface data using anatomical information extracted from radiographic images. The system is designed to take inherent advantage of Web for facilitating multi-center data collection and collaborative clinical decisions. The preliminary analysis of patient data showed promising results, which involve improved documentation standard, clinical decision knowledge base record, facilitated exchange and retrieval of medical data between institutions in multi-center clinical studies, 3D visualization of spinal deformity, and permanent monitoring of treatments.

Association of MR relaxation and cartilage deformation in knee osteoarthritis.

We assessed the relationship between cartilage MR relaxation times and biomechanical response of tibiofemoral articular cartilage to physiological loading in healthy subjects and patients with osteoarthritis (OA). Female subjects above 40 years of age with (N(1) = 20) and without (N(2) = 10) OA were imaged on a 3T MR scanner using a custom made loading device. MR images were acquired with the knee flexed at 20° with and without a compressive load of 50% of the subject's bodyweight. The subjects were categorized based on the clinical MRI scoring of medial and lateral cartilage surfaces. Data were stratified twice into two equal groups (low and high) at the median value of T(1ρ) and T(2) relaxation time. The change in contact area and cartilage deformation was measured within these groups. Paired Student's t-test (α = 0.05) was used to analyze the effect of loading on contact area and deformation. The average area of the contact region in the medial compartment was significantly higher in OA subjects compared with normal subjects in both unloaded (314 ± 112 mm(2) vs. 227 ± 106 mm(2), p = 0.023) and loaded (425 ± 128 mm(2) vs. 316 ± 107 mm(2), p = 0.01) conditions. The overall relative change of cartilage thickness in the medial compartment was significantly higher than the lateral compartment (-5.3 ± 9.9% vs. -1.9 ± 9.2%, p = 0.042). When cartilage was divided into deep and superficial layers, superficial layers showed higher changes in relaxation time (T(1ρ) and T(2)) than the changes in relaxation time of whole cartilage (Normal: 12.5% vs. 6.9%; OA: 10.9% vs. 4.6%). The average T(1ρ) and T(2) times, change in area of contact region, and change in cartilage thickness in subjects with OA were higher when compared to normal subjects. This study provides support for a relationship between the mechanical response of cartilage to physiological loading (cartilage-on-cartilage contact area and cartilage deformation) and MR relaxation times (T(1ρ) and T(2)) in both OA patients and normal subjects.

Computer-aided methods for assessing lower limb deformities in orthopaedic surgery planning.

Accurate, simple, and quick measurement of anatomical deformities at preoperative stage is clinically important for decision making in surgery planning. The deformities include excessive torsional, angular, and curvature deformation. This paper presents computer-aided methods for automatically measuring anatomical deformities of long bones of the lower limb. A three-dimensional bone model reconstructed from CT scan data of the patient is used as input. Anatomical landmarks on femur and tibia bone models are automatically identified using geometric algorithms. Medial axes of femur and tibia bones, and anatomical landmarks are used to generate functional and reference axes. These methods have been implemented in a software program and tested on a set of CT scan data. Overall, the performance of the computerized methodology was better or similar to the manual method and its results were reproducible.

Automated identification of anatomical landmarks on 3D bone models reconstructed from CT scan images.

Identification of anatomical landmarks on skeletal tissue reconstructed from CT/MR images is indispensable in patient-specific preoperative planning (tumour referencing, deformity evaluation, resection planning, and implant alignment and anchoring) as well as intra-operative navigation (bone registration and instruments referencing). Interactive localisation of landmarks on patient-specific anatomical models is time-consuming and may lack in repeatability and accuracy. We present a computer graphics-based method for automatic localisation and identification (labelling) of anatomical landmarks on a 3D model of bone reconstructed from CT images of a patient. The model surface is segmented into different landmark regions (peak, ridge, pit and ravine) based on surface curvature. These regions are labelled automatically by an iterative process using a spatial adjacency relationship matrix between the landmarks. The methodology has been implemented in a software program and its results (automatically identified landmarks) are compared with those manually palpated by three experienced orthopaedic surgeons, on three 3D reconstructed bone models. The variability in location of landmarks was found to be in the range of 2.15-5.98 mm by manual method (inter surgeon) and 1.92-4.88 mm by our program. Both methods performed well in identifying sharp features. Overall, the performance of the automated methodology was better or similar to the manual method and its results were reproducible. It is expected to have a variety of applications in surgery planning and intra-operative navigation.

Rapid development of auricular prosthesis using CAD and rapid prototyping technologies.

External ear defects can be corrected by surgery, but this may not be feasible for personal or medical reasons. Reconstructive solutions are a good alternative, but rely on the artistry and availability of the anaplastologist. A semi-automated methodology using computer-aided design (CAD) and rapid prototyping (RP) technologies was developed for auricular prosthesis development, and demonstrated in a real-life case. The correct geometry and position of the prosthesis were ensured by stacking the computed tomography scan images of the contralateral normal ear in reverse order, and joining them using a medical modelling software program. The CAD model of the remnant portion of the defective ear was subtracted from the model of the mirrored contralateral ear, using a haptic CAD system, to obtain the final geometry of the prosthesis. Polymer models were fabricated in RP systems, and used for making a corresponding mould. Medical grade silicone rubber of the appropriate colour was packed into the mould to fabricate the final ear prosthesis and fitted to the deficient side of the patient using medical grade adhesive. The computer-aided methodology gave a high level of accuracy in terms of shape, size and position of the prosthesis, and a significantly shorter lead time compared to the conventional (manual) technique.

Allylindation of cyclopropenes in organic and aqueous media: switching the regio- and stereoselectivity based on the chelation with a hydroxyl group and the crystal structure of the cyclopropylindium product.

Hydroxy-bearing cyclopropenes react with allylindium reagents to undergo clean allylindation both in organic and aqueous media, in which the chelation of the hydroxyl group to indium plays the central role. The regio- and stereoselectivity have been regulated both by the location of the hydroxyl group in the molecules and the reaction solvents. In particular, the allylindation in water shows marked differences from that in organic solvents; the regio- and stereoselectivity have totally been reversed compared with those in organic solvents. Unusually stable cyclopropyl-indium compounds have been isolated from the reaction of 1-(omega-hydroxyalkyl)cyclopropenes and the structure has fully been established by X-ray crystallography.