Quantitative imaging of musculoskeletal tissue

What does a department need to get involved in clinical trials?

Clinical trials are conducted to evaluate the usefulness of a drug, medical treatment, surgical intervention, radiological procedure, behavioral intervention, or preventive health care strategy. Clinical trials are challenging, time-consuming, and need careful planning and execution. There are certain requirements for an academic unit to be ready for conducting quality research, especially clinical trials. These include logistical concerns, infrastructure, appropriately trained human resources, conformity with ethical compliances and regulatory compliances as per the laws governing the respective geographical regions. Infrastructure requirements include research division space, robust data archival system, archival of imaging data, laboratory services, information technology division and facilities for the appropriate consenting process. Human resources such as principal investigators, data managers, clinical research assistants and biostatisticians are needed to execute the clinical trial as per the study design. Adherence to ethical and regulatory standards; during the conduct of the clinical trial are imperative. Strict compliance with prevailing governing laws in the country is a prerequisite for a department to get involved in clinical trials. The department also needs to put in place an institutional ethics committee; the composition of which is often governed by regulatory laws. The ethical aspects of the trial undergo a formal scrutiny by an Institute ethics committee that ensures quality care to the patient, and safeguards the patient's rights and privileges. The academic unit of any department forms the core for possible research and pursuit of clinical trials. A department with rich clinical experience and expertise in the filed aids in the execution of quality research. The academic department must consider grant writing and multiple center collaborative research projects in due course of time to further enhance the quality of clinical trials and research output.

Automatic segmentation of ultrasound images of gastrocnemius medialis with different echogenicity levels using convolutional neural networks

The purpose of this study was to develop an automatic method for the segmentation of muscle cross-sectional area on transverse B-mode ultrasound images of gastrocnemius medialis using a convolutional neural network(CNN). In the provided dataset images with both normal and increased echogenicity are present. The manually annotated dataset consisted of 591 images, from 200 subjects, 400 relative to subjects with normal echogenicity and 191 to subjects with augmented echogenicity. From the DICOM files, the image has been extracted and processed using the CNN, then the output has been post-processed to obtain a finer segmentation. Final results have been compared to the manual segmentations. Precision and Recall scores as mean ± standard deviation for training, validation, and test sets are 0.96 ± 0.05, 0.90 ± 0.18, 0.89 ± 0.15 and 0.97 ±0.03, 0.89± 0.17, 0.90 ± 0.14 respectively. The CNN approach has also been compared to another automatic algorithm, showing better performances. The proposed automatic method provides an accurate estimation of muscle cross-sectional area in muscles with different echogenicity levels.

Automatic Tracking of Muscle Cross-Sectional Area Using Convolutional Neural Networks with Ultrasound

OBJECTIVES

The purpose of this study was to develop an automatic tracking method for the muscle cross-sectional area (CSA) on ultrasound (US) images using a convolutional neural network (CNN). The performance of the proposed method was evaluated and compared with that of the state-of-the art muscle segmentation method.

METHODS

A real-time US image sequence was obtained from the rectus femoris muscle during voluntary contraction. A CNN was built to segment the rectus femoris muscle and calculate the CSA in each US frame. This network consisted of 2 stages: feature extraction and score map reconstruction. The training of the network was divided into 3 steps with output score map resolutions of one-fourth, one-half, and all of the original image. We evaluated the segmentation performance of our method with 5-fold cross-validation. The mean precision, recall, and dice similarity score were calculated.

RESULTS

The mean precision, recall, and Dice's coefficient (DSC) ± SD were 0.936 ± 0.029, 0.882 ± 0.045, and 0.907 ± 0.023, respectively. Compared with the state-of-the-art muscle segmentation method (constrained mutual-information-based free-form deformation), the proposed method using CNN showed high performance.

CONCLUSIONS

The automated method proposed in this study provides an accurate and efficient approach to the estimation of the muscle CSA during muscle contraction.

A Survey on Biofeedback and Actuation in Wireless Body Area Networks (WBANs)

Wireless body area networks (WBANs) have attained increasing popularity as the next generation framework of wearable technologies for human monitoring. Invasive or noninvasive wearable sensors designed in a WBAN are worn to gather vital information. Biofeedback is a recent concept where collected data are used to generate actuation signals in WBANs. Applications can be seen in various areas such as sports (e.g., locomotor velocity) or medicine (e.g., blood pressure measurement). However, since the body is closely regulated, the next generation WBAN technology must be smart enough to react to monitored data. The main aim of this paper is to review the current state of biofeedback and actuation technology on WBANs in terms of its structure, applications, benefits, and control approaches. The emphasis on the specific requirements when applying biofeedback to humans will be highlighted and discussed. Challenges and open research issues will be concluded at the end.

Investigation of random walks knee cartilage segmentation model using inter-observer reproducibility: Data from the osteoarthritis initiative

BACKGROUND

Existing knee cartilage segmentation methods have reported several technical drawbacks. In essence, graph cuts remains highly susceptible to image noise despite extended research interest; active shape model is often constraint by the selection of training data while shortest path have demonstrated shortcut problem in the presence of weak boundary, which is a common problem in medical images.

OBJECTIVES

The aims of this study is to investigate the capability of random walks as knee cartilage segmentation method.

METHODS

Experts would scribble on knee cartilage image to initialize random walks segmentation. Then, reproducibility of the method is assessed against manual segmentation by using Dice Similarity Index. The evaluation consists of normal cartilage and diseased cartilage sections which is divided into whole and single cartilage categories.

RESULTS

A total of 15 normal images and 10 osteoarthritic images were included. The results showed that random walks method has demonstrated high reproducibility in both normal cartilage (observer 1: 0.83±0.028 and observer 2: 0.82±0.026) and osteoarthritic cartilage (observer 1: 0.80±0.069 and observer 2: 0.83±0.029). Besides, results from both experts were found to be consistent with each other, suggesting the inter-observer variation is insignificant (Normal: P=0.21; Diseased: P=0.15).

CONCLUSION

The proposed segmentation model has overcame technical problems reported by existing semi-automated techniques and demonstrated highly reproducible and consistent results against manual segmentation method.

A novel outlier detection method for identifying torque-related transient patterns of in vivo muscle behavior

This paper proposed a novel outlier detection method, named l1-regularized outlier isolation and regression (LOIRE), to examine torque-related transient patterns of in vivo muscle behavior from multimodal signals, including electromyography (EMG), mechanomyography (MMG) and ultrasonography (US), during isometric muscle contraction. Eight subjects performed isometric ramp contraction of knee up to 90% of the maximal voluntary contraction, and EMG, MMG and US were simultaneously recorded from the rectus femoris muscle. Five features, including two root mean square amplitudes from EMG and MMG, muscle cross sectional area, muscle thickness and width from US were extracted. Then, local polynomial regression was used to obtain the signal-to-torque relationships and their derivatives. By assuming the signal-to-torque functions are basically quadratic, the LOIRE method is applied to identify transient torque-related patterns of EMG, MMG and US features as outliers of the linear derivative-to-torque functions. The results show that the LOIRE method can effectively reveal transient patterns in the signal-to-torque relationships (for example, sudden changes around 20% MVC can be observed from all features), providing important information about in vivo muscle behavior.

Clinical utility of quantitative imaging

Quantitative imaging (QI) is increasingly applied in modern radiology practice, assisting in the clinical assessment of many patients and providing a source of biomarkers for a spectrum of diseases. QI is commonly used to inform patient diagnosis or prognosis, determine the choice of therapy, or monitor therapy response. Because most radiologists will likely implement some QI tools to meet the patient care needs of their referring clinicians, it is important for all radiologists to become familiar with the strengths and limitations of QI. The Association of University Radiologists Radiology Research Alliance Quantitative Imaging Task Force has explored the clinical application of QI and summarizes its work in this review. We provide an overview of the clinical use of QI by discussing QI tools that are currently used in clinical practice, clinical applications of these tools, approaches to reporting of QI, and challenges to implementing QI. It is hoped that these insights will help radiologists recognize the tangible benefits of QI to their patients, their referring clinicians, and their own radiology practice.

Association between hip and knee cartilage measured using radiographs and magnetic resonance imaging: the Tasmanian Older Adult Cohort Study

OBJECTIVE

Cartilage loss is a key pathological feature of OA and can be assessed indirectly using radiography or directly through MRI. A number of cross-sectional studies have suggested that primary generalized osteoarthritis (PGOA) may be a distinct disease, but despite the high frequency of involvement of the hip and the knee joints in OA, very few studies have looked at the radiographic association between these two joints, and none has done so using MRI. The aim of this study was to examine the association of hip and knee cartilage measured by both radiography and MRI.

METHODS

We studied 151 participants from the Tasmanian Older Adult Cohort (TASOAC) study, who were selected randomly from the southern Tasmanian electoral rolls. MRI was used to assess hip and knee cartilage volume and radiography was used to assess joint space narrowing (JSN). Correlation analyses were used to compare cartilage volume measurements and JSN.

RESULTS

In adjusted analysis, there was a consistent, positive association between knee and hip cartilage volume that was best for total knee cartilage volume (r = 0.16-0.40, all P < 0.05). In contrast, there was at best a weak correlation, depending on the site, between hip and knee JSN (r = -0.01 to 0.21).

CONCLUSION

Hip and knee cartilage volume are more strongly associated than hip and knee JSN, suggesting a commonality of cartilage volume at different anatomic sites. The weaker radiographic association may reflect less measurement error with MRI or the contribution of multiple structures to joint space in the knee.

Imaging of alkaline phosphatase activity in bone tissue

The purpose of this study was to develop a paradigm for quantitative molecular imaging of bone cell activity. We hypothesized the feasibility of non-invasive imaging of the osteoblast enzyme alkaline phosphatase (ALP) using a small imaging molecule in combination with ¹⁹Flourine magnetic resonance spectroscopic imaging (¹⁹FMRSI). 6, 8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), a fluorinated ALP substrate that is activatable to a fluorescent hydrolysis product was utilized as a prototype small imaging molecule. The molecular structure of DiFMUP includes two Fluorine atoms adjacent to a phosphate group allowing it and its hydrolysis product to be distinguished using ¹⁹Fluorine magnetic resonance spectroscopy (¹⁹FMRS) and ¹⁹FMRSI. ALP-mediated hydrolysis of DiFMUP was tested on osteoblastic cells and bone tissue, using serial measurements of fluorescence activity. Extracellular activation of DiFMUP on ALP-positive mouse bone precursor cells was observed. Concurringly, DiFMUP was also activated on bone derived from rat tibia. Marked inhibition of the cell and tissue activation of DiFMUP was detected after the addition of the ALP inhibitor levamisole. ¹⁹FMRS and ¹⁹FMRSI were applied for the non-invasive measurement of DiFMUP hydrolysis. ¹⁹FMRS revealed a two-peak spectrum representing DiFMUP with an associated chemical shift for the hydrolysis product. Activation of DiFMUP by ALP yielded a characteristic pharmacokinetic profile, which was quantifiable using non-localized ¹⁹FMRS and enabled the development of a pharmacokinetic model of ALP activity. Application of ¹⁹FMRSI facilitated anatomically accurate, non-invasive imaging of ALP concentration and activity in rat bone. Thus, ¹⁹FMRSI represents a promising approach for the quantitative imaging of bone cell activity during bone formation with potential for both preclinical and clinical applications.

Correlations between strength and quantitative computed tomography measurement of callus mineralization in experimental tibial fractures

BACKGROUND

the evaluation of fracture healing in the clinic has not changed significantly during the past few decades, despite the development of modern tissue-imaging tools. Recent publications have reported significant and interesting associations between biomechanical properties and quantitative computed tomography data of fractures and grafts. We therefore studied the correlations between the strength and segmented quantitative computed tomography data of tibial diaphyseal fractures.

METHODS

forty male rats received a tibial-shaft osteotomy that was initially stabilized with either intramedullary nailing or external fixation. Evaluation at 30 and 60 days post-osteotomy included X-ray, quantitative computed tomography and bending testing. Quantitative computed tomography data were segmented by voxel density into soft callus (171-539 mg/cm(3)), hard callus (540-1199 mg/cm(3)) and cortical bone (≥ 1200mg/cm(3)), and volumetric bone mineral density was calculated.

FINDINGS

all fractures demonstrated pronounced formation of soft and hard callus tissues at 30 days post-osteotomy, and at 60 days the cortical bone volume was significantly increased with callus resorption. Bending strength correlated significantly and positively with fracture-site cortical bone volume and volumetric bone mineral density in the intramedullary nailed group in the early phase of healing.

INTERPRETATION

quantitative computed tomography was used to quantify characteristic secondary healing. The observed correlations indicate that biomechanically important mineralization can be measured by quantitative computed tomography in the early phase of healing in flexibly fixed fractures.

Quantitative cartilage imaging in knee osteoarthritis

Quantitative measures of cartilage morphology (i.e., thickness) represent potentially powerful surrogate endpoints in osteoarthritis (OA). These can be used to identify risk factors of structural disease progression and can facilitate the clinical efficacy testing of structure modifying drugs in OA. This paper focuses on quantitative imaging of articular cartilage morphology in the knee, and will specifically deal with different cartilage morphology outcome variables and regions of interest, the relative performance and relationship between cartilage morphology measures, reference values for MRI-based knee cartilage morphometry, imaging protocols for measurement of cartilage morphology (including those used in the Osteoarthritis Initiative), sensitivity to change observed in knee OA, spatial patterns of cartilage loss as derived by subregional analysis, comparison of MRI changes with radiographic changes, risk factors of MRI-based cartilage loss in knee OA, the correlation of MRI-based cartilage loss with clinical outcomes, treatment response in knee OA, and future directions of the field.

Herniation pits and cystic-appearing lesions at the anterior femoral neck: an anatomical study by MSCT and microCT

OBJECTIVE

To determine distinguishing features between herniation pits (HPs) and other cystic-appearing lesions at the anterior femoral neck in multi-slice computed tomography (MSCT) and micro-computed tomography (microCT) examinations.

MATERIALS AND METHODS

Institutional review board approval was obtained to examine 37 proximal femora of 23 cadaveric specimens (mean age available in 19 cadavers, 83 years; range 68-100 years; 9 female, 8 male, 6 unknown). All 37 femora were investigated by MSCT. 23 femora, which revealed cystic-appearing lesions at the anterior femoral neck in MSCT examinations, were additionally examined by microCT. Cystic-appearing lesions were categorized by their location, sclerotic margin, demarcation and shape in MSCT with assessment of inter-observer agreement. Detailed cortical and trabecular properties were evaluated in microCT examinations.

RESULTS

There were seven HPs in three femora. There were a number of abnormalities potentially imitating HPs, including focal osteoporosis (13 in 13 femora), degenerative changes (5 in 4 femora) and trabecular restructuring (5 in 4 femora) at the anterior femoral neck. HPs were differentiated on the basis of their subchondral/subcortical location, completely surrounding sclerosis, clear demarcation and round-to-oval shape in MSCT. Because of their location and their microscopic appearance, HPs seem to resemble intra-osseous ganglia at the anterior femoral neck.

CONCLUSION

HPs have to be differentiated from other cystic appearing lesions at the anterior femoral neck to avoid overestimation of their incidence in the context of diagnosis of femoroacetabular impingement.

Phase-sensitive X-ray imaging of synovial joints

OBJECTIVE

To test the efficacy of phase-sensitive X-ray imaging for intact synovial joints, whereby refraction effects, along with the attenuation of conventional radiography, can be exploited.

DESIGN

Intact cadaveric human knee joints were imaged, in the computed tomographic mode, using an analyzer-based X-ray system at the National Synchrotron Light Source, Brookhaven National Laboratory. A collimated fan beam of 51 keV X-rays was prepared by a silicon [1,1,1 reflection] double-crystal monochromator. The X-ray beam transmitted through the specimen was imaged after diffraction in the vertical plane by means of the analyzer crystal with the analyzer crystal tuned to its half-reflectivity point (6.5 microrad). A two-dimensional filtered backprojection (FBP) algorithm was used for reconstructing transverse slices of images.

RESULTS

The resulting images demonstrate simultaneous soft tissue and bone contrast at a level that has not been achieved previously. Identifiable structures include articular cartilage, cruciate ligaments, loose connective tissue, menisci, and chondrocalcinosis.

CONCLUSION

Phase-sensitive X-ray imaging using an analyzer-based system renders exceptionally high quality images of soft and hard tissues within synovial joints, with high contrast and resolution, and thus holds promise for the eventual clinical utility.

Overview of imaging in inflammatory arthritis

Whether magnetic resonance imaging (MRI) or ultrasound (US) are chosen for the purposes of musculoskeletal interrogation depends upon a variety of factors ranging from the anatomy targeted to cost considerations and the time of acquisition. Newer technologies such as higher-strength MRI or 3D-US promise to help overcome some of the disadvantages of each option. Improving technical proficiency is the thrust of efforts to support more widespread application of sonographic assessment in various clinical arenas. Finally, these technologies offer the opportunity to diagnose inflammatory conditions at early stages of their disease progression.