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Evaluation of the 3D bone morphology of the glenohumeral joint is necessary for pre-surgical planning. Zero echo time (ZTE) magnetic resonance imaging (MRI) provides excellent bone contrast and can potentially be used in the place of computed tomography. Segmentation of the shoulder anatomy, particularly the humeral head and the acetabulum, is needed for the detailed assessment of each anatomy and for pre-surgical preparation. In this study, we compared the performance of two popular deep learning models based on Google’s DeepLab and U-Net to perform automated segmentation on ZTE MRI of human shoulders. Axial ZTE images of normal shoulders (n = 31) acquired at 3-Tesla were annotated for training with DeepLab and 2D U-Net, and the trained model was validated with testing data (n = 13). While both models showed visually satisfactory results for segmenting the humeral bone, U-Net slightly over-estimated while DeepLab under-estimated the segmented area compared to the ground truth. Testing accuracy quantified by Dice score was significantly higher (p < 0.05) for U-Net (88%) than DeepLab (81%) for the humeral segmentation. We have also implemented the U-Net model onto an MRI console for push-button DL segmentation processing. Although this is an early work with limitations, our approach has the potential to improve shoulder MR evaluation hindered by manual post-processing and may provide clinical benefit for quickly visualizing bones of the glenohumeral joint.

Introduction: The disco-vertebral junction (DVJ) of the lumbar spine contains thin structures with short T2 values, including the cartilaginous endplate (CEP) sandwiched between the bony vertebral endplate (VEP) and the nucleus pulposus (NP). We previously demonstrated that ultrashort-echo-time (UTE) MRI, compared to conventional MRI, is able to depict the tissues at the DVJ with improved contrast. In this study, we sought to further optimize UTE MRI by characterizing the contrast-to-noise ratio (CNR) of these tissues when either single echo or echo subtraction images are used and with varying echo times (TEs). Methods: In four cadaveric lumbar spines, we acquired 3D Cones (a UTE sequence) images at varying TEs from 0.032 ms to 16 ms. Additionally, spin echo T1- and T2-weighted images were acquired. The CNRs of CEP-NP and CEP-VEP were measured in all source images and 3D Cones echo subtraction images. Results: In the spin echo images, it was challenging to distinguish the CEP from the VEP, as both had low signal intensity. However, the 3D Cones source images at the shortest TE of 0.032 ms provided an excellent contrast between the CEP and the VEP. As the TE increased, the contrast decreased in the source images. In contrast, the 3D Cones echo subtraction images showed increasing CNR values as the second TE increased, reaching statistical significance when the second TE was above 10 ms (p < 0.05). Conclusions: Our study highlights the feasibility of incorporating UTE MRI for the evaluation of the DVJ and its advantages over conventional spin echo sequences for improving the contrast between the CEP and adjacent tissues. Additionally, modulation of the contrast for the target tissues can be achieved using either source images or subtraction images, as well as by varying the echo times.

Background: Computed tomography (CT) is the preferred imaging modality for bone evaluation of the knee, while MRI of the bone is actively being developed. We present three techniques using short-interval delta ultrashort echo time (δUTE), field echo (FE), and FE with high resolution–deep learning reconstruction (HR–DLR) for direct bone MRI. Methods: Knees of healthy volunteers (n = 5, 3 females, 38 ± 17.2 years old) were imaged. CT-like images were generated by averaging images from multiple echoes and inverting. The bone signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined. Results: The δUTE depicted a cortical bone with high signal intensity but could not resolve trabeculae. In contrast, both the FE and FE HR–DLR images depicted cortical and trabecular bone with high signal. Quantitatively, while δUTE had a good bone SNR of ~100 and CNR of ~40 for the cortical bone, the SNR for the FE HR–DLR was significantly higher (p < 0.05), at over 400, and CNR at over 200. Conclusions: For 3D rendering of the bone surfaces, the δUTE provided better image contrast and separation of bone from ligaments and tendons than the FE sequences. While there still is no MRI technique that provides a perfect CT-like contrast, continued advancement of MRI techniques may provide benefits for specific use cases.

Isthmic spondylolysis is characterized by a stress injury to the pars interarticularis bones of the lumbar spines and is often missed by conventional magnetic resonance imaging (MRI), necessitating a computed tomography (CT) for accurate diagnosis. We compare MRI techniques suitable for producing CT-like images. Lumbar spines of asymptomatic and low back pain (LBP) subjects were imaged at 3-Tesla with multi-echo ultrashort echo time (UTE) and field echo (FE) sequences followed by simple post-processing of averaging and inverting to depict spinal bones with a CT-like appearance. The contrast-to-noise ratio (CNR) for bone was determined to compare UTE vs. FE and single-echo vs. multi-echo data. Visually, both sequences depicted cortical bone with good contrast; UTE-processed sequences provided a flatter contrast for soft tissues that made them easy to distinguish from bone, while FE-processed images had better resolution and bone–muscle contrast, which are important for fracture detection. Additionally, multi-echo images provided significantly (p = 0.03) greater CNR compared with single-echo images. Using these techniques, progressive spondylolysis was detected in an LBP subject. This study demonstrates the feasibility of using spine bone MRI to yield CT-like contrast. Through the employment of multi-echo UTE and FE sequences combined with simple processing, we observe sufficient enhancements in image quality and contrast to detect pars fractures.

Intrinsic cerebrospinal fluid (CSF) dynamics in the brain have been extensively studied, particularly the egress sites of tagged intrinsic CSF in the meninges. Although spinal CSF recirculates within the central nervous system (CNS), we hypothesized that CSF outflows from the lumbar spinal canal. We aimed to visualize and semi-quantify the outflow using non-contrast MRI techniques. We utilized a 3 Tesla clinical MRI with a 16-channel spine coil, employing time–spatial labeling inversion (Time-SLIP) with tag-on and tag-off acquisitions, T2-weighted coronal 2D fluid-attenuated inversion recovery (FLAIR) and T2-weighted coronal 3D centric ky-kz single-shot FSE (cSSFSE). Images were acquired using time–spatial labeling inversion pulse (Time-SLIP) with tag-on and tag-off acquisitions with varying TI periods. Ten healthy volunteers with no known spinal diseases participated. Variations in tagged CSF outflow were observed across different thoracolumbar nerve root segments in all participants. We quantified CSF outflow at all lumbar levels and the psoas region. There was no significant difference among the ROIs for signal intensity. The tagged CSF outflow from the spinal canal is small but demonstrates egress to surrounding tissues. This finding may pave the way for exploring intrathecal drug delivery, understanding of CSF-related pathologies and its potential as a biomarker for peripheral neuropathy and radiculopathy.

Isthmic spondylolysis results in fracture of pars interarticularis of the lumbar spine, found in as many as half of adolescent athletes with persistent low back pain. While computed tomography (CT) is the gold standard for the diagnosis of spondylolysis, the use of ionizing radiation near reproductive organs in young subjects is undesirable. While magnetic resonance imaging (MRI) is preferable, it has lowered sensitivity for detecting the condition. Recently, it has been shown that ultrashort echo time (UTE) MRI can provide markedly improved bone contrast compared to conventional MRI. To take UTE MRI further, we developed supervised deep learning tools to generate (1) CT-like images and (2) saliency maps of fracture probability from UTE MRI, using ex vivo preparation of cadaveric spines. We further compared quantitative metrics of the contrast-to-noise ratio (CNR), mean squared error (MSE), peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM) between UTE MRI (inverted to make the appearance similar to CT) and CT and between CT-like images and CT. Qualitative results demonstrated the feasibility of successfully generating CT-like images from UTE MRI to provide easier interpretability for bone fractures thanks to improved image contrast and CNR. Quantitatively, the mean CNR of bone against defect-filled tissue was 35, 97, and 146 for UTE MRI, CT-like, and CT images, respectively, being significantly higher for CT-like than UTE MRI images. For the image similarity metrics using the CT image as the reference, CT-like images provided a significantly lower mean MSE (0.038 vs. 0.0528), higher mean PSNR (28.6 vs. 16.5), and higher SSIM (0.73 vs. 0.68) compared to UTE MRI images. Additionally, the saliency maps enabled quick detection of the location with probable pars fracture by providing visual cues to the reader. This proof-of-concept study is limited to the data from ex vivo samples, and additional work in human subjects with spondylolysis would be necessary to refine the models for clinical use. Nonetheless, this study shows that the utilization of UTE MRI and deep learning tools could be highly useful for the evaluation of isthmic spondylolysis.

Abstract Background The degeneration of the intervertebral disc (IVD) is characterized by proteolytic degradation of the extracellular matrix, and its repair requires the production of an extracellular matrix with a high proteoglycan-to-collagen ratio characteristic of a nucleus pulposus (NP)-like phenotype in vivo. At the moment, there is no medical treatment to reverse or even retard disc degeneration. The purpose of the present study was to determine if a low dose of short link N (sLN), a recently discovered fragment of the link N peptide, could behave in a manner similar to that of link N in restoring the proteoglycan content and proteoglycan-to-collagen ratio of the disc in a rabbit model of IVD degeneration, as an indication of its potential therapeutic benefit in reversing disc degeneration. Methods Adolescent New Zealand white rabbits received an annular puncture with an 18-gauge needle into two noncontiguous discs to induce disc degeneration. Two weeks later, either saline (10 μL) or sLN (25 μg in 10 μL saline) was injected into the center of the NP. The sLN concentration was empirically chosen at a lower molar concentration equivalent to half that of link N (100 μg in 10 μL). The effect on radiographic, biochemical and histologic changes were evaluated. Results Following needle puncture, disc height decreased by about 25–30% within 2 weeks and maintained this loss for the duration of the 12-week study; a single 25-μg sLN injection at 2 weeks partially restored this loss in disc height. sLN injection led to an increase in glycosaminoglycans (GAG) content 12 weeks post-injection in both the NP and annulus fibrosus (AF). There was a trend towards maintaining control disc collagen-content with sLN supplementation and the GAG-to-collagen ratio in the NP was increased when compared to the saline group. Conclusions When administered to the degenerative disc in vivo, sLN injection leads to an increase in proteoglycan content and a trend towards maintaining control disc collagen content in both the NP and AF. This is similar to link N when it is administered to the degenerative disc. Thus, pharmacologically, sLN supplementation could be a novel therapeutic approach for treating disc degeneration.

Study DesignPreliminary clinical trial.PurposeTo determine the safety and initial efficacy of intradiscal injection of autologous platelet-rich plasma (PRP) releasate in patients with discogenic low back pain.Overview of LiteraturePRP, which is comprised of autologous growth factors and cytokines, has been widely used in the clinical setting for tissue regeneration and repair. PRP has been shown in vitro and in vivo to potentially stimulate intervertebral disc matrix metabolism.MethodsInclusion criteria for this study included chronic low back pain without leg pain for more than 3 months; one or more lumbar discs (L3/L4 to L5/S1) with evidence of degeneration, as indicated via magnetic resonance imaging (MRI); and at least one symptomatic disc, confirmed using standardized provocative discography. PRP releasate, isolated from clotted PRP, was injected into the center of the nucleus pulposus. Outcome measures included the use of a visual analog scale (VAS) and the Roland-Morris Disability Questionnaire (RDQ), as well as X-ray and MRI (T2-quantification).ResultsData were analyzed from 14 patients (8 men and 6 women; mean age, 33.8 years). The average follow-up period was 10 months. Following treatment, no patient experienced adverse events or significant narrowing of disc height. The mean pain scores before treatment (VAS, 7.5±1.3; RDQ, 12.6±4.1) were significantly decreased at one month, and this was generally sustained throughout the observation period (6 months after treatment: VAS, 3.2±2.4, RDQ; 3.6±4.5 and 12 months: VAS, 2.9±2.8; RDQ, 2.8±3.9; p

We propose a semi-automatic algorithm for the segmentation of vertebral bodies in magnetic resonance (MR) images of the human lumbar spine. Quantitative analysis of spine MR images often necessitate segmentation of the image into specific regions representing anatomic structures of interest. Existing algorithms for vertebral body segmentation require heavy inputs from the user, which is a disadvantage. For example, the user needs to define individual regions of interest (ROIs) for each vertebral body, and specify parameters for the segmentation algorithm. To overcome these drawbacks, we developed a semi-automatic algorithm that considerably reduces the need for user inputs. First, we simplified the ROI placement procedure by reducing the requirement to only one ROI, which includes a vertebral body; subsequently, a correlation algorithm is used to identify the remaining vertebral bodies and to automatically detect the ROIs. Second, the detected ROIs are adjusted to facilitate the subsequent segmentation process. Third, the segmentation is performed via graph-based and line-based segmentation algorithms. We tested our algorithm on sagittal MR images of the lumbar spine and achieved a 90% dice similarity coefficient, when compared with manual segmentation. Our new semi-automatic method significantly reduces the user’s role while achieving good segmentation accuracy.

We propose a new deep learning network capable of successfully segmenting intervertebral discs and their complex boundaries from magnetic resonance (MR) spine images. The existing U-network (U-net) is known to perform well in various segmentation tasks in medical images; however, its performance with respect to details of segmentation such as boundaries is limited by the structural limitations of a max-pooling layer that plays a key role in feature extraction process in the U-net. We designed a modified convolutional and pooling layer scheme and applied a cascaded learning method to overcome these structural limitations of the max-pooling layer of a conventional U-net. The proposed network achieved 3% higher Dice similarity coefficient (DSC) than conventional U-net for intervertebral disc segmentation (89.44% vs. 86.44%, respectively; p < 0.001). For intervertebral disc boundary segmentation, the proposed network achieved 10.46% higher DSC than conventional U-net (54.62% vs. 44.16%, respectively; p < 0.001).

Step-off edges and tissue interfaces are prevalent in cartilage injury such as after intra-articular fracture and reduction, and in focal defects and surgical repair procedures such as osteochondral graft implantation. It would be useful to assess the function of injured or donor tissues near such step-off edges and the extent of integration at material interfaces. The objective of this study was to determine if indentation testing is sensitive to the presence of step-off edges and the integrity of material interfaces, in both in vitro simulated repair samples of bovine cartilage defect filled with fibrin matrix, and in vivo biological repair samples from a goat animal model. Indentation stiffness decreased at locations approaching a step-off edge, a lacerated interface, or an integrated interface in which the distal tissue was relatively soft. The indentation stiffness increased or remained constant when the site of indentation approached an integrated interface in which the distal tissue was relatively stiff or similar in stiffness to the tissue being tested. These results indicate that indentation testing is sensitive to step-off edges and interface integrity, and may be useful for assessing cartilage injury and for following the progression of tissue integration after surgical treatments. [ABSTRACT FROM AUTHOR]

To determine, for clinical indentation testing of human articular cartilage, the effects of aging and degeneration on indentation stiffness and traditional indices of cartilage degeneration; the relationship between indentation stiffness and indices of degeneration; and the sensitivity and specificity of indentation stiffness to cartilage degeneration. Osteochondral cores from femoral condyles of cadaveric human donors were harvested. Samples were distributed into experimental groups based on donor age (young [20–39 years], middle [40–59 years], and old [≥60 years]), and a macroscopic articular surface appearance that was either normal or mildly degenerate, without deep erosion. Samples were analyzed for indentation stiffness, cartilage thickness, India ink staining (quantitated as the reflected light score), and Mankin-Shapiro histopathology score. Indentation stiffness, India ink staining, and the histopathology score each varied markedly between normal-sample and degenerate-sample groups but varied relatively little between normal samples obtained from different age groups. A decrease in indentation stiffness (softening) correlated with a decrease in the reflectance score and an increase in the overall histopathology score, especially the surface irregularity component of the histopathology score. Receiver operating characteristic analysis suggested that the indentation testing could accurately detect cartilage degeneration as indicated by macroscopic appearance, India ink staining, and histopathology score. The indentation stiffness of the normal to mildly degenerate samples tested in this study was sensitive to mild degeneration at the articular surface and was insensitive to changes associated with normal aging or to slight variations in cartilage thickness. This suggests that indentation testing may be a useful clinical tool for the evaluation of early-stage degenerative changes in articular cartilage. [ABSTRACT FROM AUTHOR]

Background: The goat is one of the most commonly used preclinical models for focal defect repair and regeneration. While the biomechanics of the human knee has been studied extensively, less is known about the biomechanics of the caprine knee. Differences between human and caprine knees have not been quantified and their significance is largely unknown. Methods: We conducted a biomechanical analysis of the differences in goat and human knees to assess the validity of these preclinical in vivo models. Results: CT and MRI scans revealed several differences in articular geometry: the caprine tibial plateaux were more convex and the menisci were significantly thicker and covered a larger proportion of the tibial articular surface. Caprine cartilage thickness was consistently thinner, while elastic modulus on indentation testing was consistently stiffer than human cartilage measured at eight different articular locations. Contact area and pressure were measured with electronic pressure sensors under loads normalized by multiples of body weight and at knee flexion angles reported for walking. The highest peaks in contact pressure were measured in the patellofemoral joint in goat and human knees. Peak contact pressure measured at 2 times body weight at the goat tibiofemoral joint at 70° flexion was significantly higher than for any other condition at the human tibiofemoral joint. Conclusion: These differences in contact conditions might explain the lower quality of local repair reported for caprine femoral condylar defects relative to trochlear defects. Further comparative analysis, including biologic response, is necessary to determine the extent to which the goat knee reproduces clinical conditions. [ABSTRACT FROM AUTHOR]