An automated algorithm for the detection of cortical interruptions and its underlying loss of trabecular bone; a reproducibility study

Open-source image analysis tool for the identification and quantification of cortical interruptions and bone erosions in high-resolution peripheral quantitative computed tomography images of patients with rheumatoid arthritis

Identification of bone erosions and quantification of erosion volume is important for rheumatoid arthritis diagnosis, and can add important information to evaluate disease progression and treatment effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) is well suited for this purpose, however analysis methods are not widely available. The purpose of this study was to develop an open-source software tool for the identification and quantification of bone erosions using images acquired by HR-pQCT. The collection of modules, Bone Analysis Modules (BAM) - Erosion, implements previously published erosion analysis techniques as modules in 3D Slicer, an open-source image processing and visualization tool. BAM includes a module to automatically identify cortical interruptions, from which erosions are manually selected, and a hybrid module that combines morphological and level set operations to quantify the volume of bone erosions. HR-pQCT images of the second and third metacarpophalangeal (MCP) joints were acquired in patients with RA (XtremeCT, n = 14, XtremeCTII, n = 22). The number of cortical interruptions detected by BAM-Erosion agreed strongly with the previously published cortical interruption detection algorithm for both XtremeCT (r² = 0.85) and XtremeCTII (r² = 0.87). Erosion volume assessment by BAM-Erosion agreed strongly (r² = 0.95) with the Medical Image Analysis Framework. BAM-Erosion provides an open-source erosion analysis tool that produces comparable results to previously published algorithms, with improved options for visualization. The strength of the tool is that it implements multiple image processing algorithms for erosion analysis on a single, widely available, open-source platform that can accommodate future updates.

Analysis of bone erosions in rheumatoid arthritis using HR-pQCT: Development of a measurement algorithm and assessment of longitudinal changes

Purpose

The purpose of this study was to establish an algorithm for measuring bone erosions at metacarpophalangeal (MCP) joints using high-resolution peripheral quantitative computed tomography (HR-pQCT), to investigate the precision of measurements, and to assess longitudinal changes in bone erosions among patients with rheumatoid arthritis (RA).

Methods

The 2nd and 3rd MCP joints were scanned at a voxel size of 60.7 μm using second-generation HR-pQCT. Bone erosions on MCP joints were identified using a semi-automated algorithm we developed, and each erosion parameter was measured. Measurement reproducibility was evaluated in 19 healthy subjects using intraclass correlation coefficients (ICCs) and root mean square percent coefficient of variance (RMS%CV). Finally, longitudinal changes in bone erosions over a period of 12 months were assessed in 26 patients with RA based on the calculated least significant change (LSC).

Results

Reproducibilities for measurement parameters regarding bone erosions with our algorithm were good (all ICCs ≥ 0.98; all RMS%CVs < 5%). No erosion parameters showed significant changes after 12 months of treatment in terms of median values in all erosions, while both progression and repair of erosions were observed individually (e.g., erosion volume: progression, 26% (+0.62 mm3); repair, 34% (-0.85 mm3); no change, 40%).

Conclusions

The measurement algorithm developed for bone erosions at MCP joints showed good reproducibility. Both progression and repair of bone erosions were observed in patients with RA even after 12 months of appropriate treatment. Our algorithm may be useful to investigate the etiology of RA and assess drug efficacy.

Imaging Study on Acupuncture Inhibiting Inflammation and Bone Destruction in Knee Osteoarthritis Induced by Monosodium Iodoacetate in Rat Model

Objective

We aim to explore whether acupuncture inhibits inflammation and bone destruction in rat model monosodium iodoacetate (MIA)-induced knee osteoarthritis (KOA) by 18F-fluorodeoxyglucose (18F-FDG) small-animal positron emission tomography (PET) and micro-computed tomography (CT) imaging.

Methods

KOA was induced in rats by intra-articular injection MIA (2 mg/50 μL) through the right knee of the rats. Forty male Sprague Dawley rats weighing 280 to 340 g (12 weeks old) were randomly divided into four groups including Control group, KOA group, KOA plus manual acupuncture group (KOA+MA), KOA plus sham acupuncture group (KOA+SA). The acupuncture treatment lasted for three weeks (one-day rest after six days of treatment). Paw withdrawal threshold test and open-field test were used to assess mechanical allodynia and locomotor activity respectively for once a week. Hematoxylin and eosin (H&E) staining was used to assess the damage of the cartilage, synovium and infrapatellar fat pad (IFP). 18F-FDG PET was performed to quantify joint inflammation. The influence on the subchondral bone in these rats was confirmed by micro-CT.

Results

Mechanical hyperalgesia, joint inflammation, and obvious bone destruction were observed in the KOA group. H&E staining of the knee joint found that manual acupuncture played a protective effect in cartilage, synovium and IFP destruction. However, compared with KOA group, the results in sham acupuncture had no significant difference. After manual acupuncture treatment in KOA rats, inflammation was significantly suppressed shown by 18F-FDG PET imaging. Micro-CT analysis of the knee joint revealed that manual acupuncture protected bone by inhibiting osteophyte development and subchondral bone remodeling.

Conclusion

The results of 18F-FDG PET and micro-CT showed that manual acupuncture inhibited inflammation and bone destruction, which provides reliable evidence for the effectiveness of acupuncture in hindering development of KOA, and provides reliable evidence for clinical application of acupuncture.

Bone erosions and osteophytes in premenopausal women with long-standing rheumatoid arthritis: association with systemic bone involvement by HR-Pqct

OBJECTIVE

To evaluate premenopausal women with long-standing RA and to explore the relationship between parameters of systemic and localized bone involvement.

METHODS

Eighty consecutive RA premenopausal women were evaluated. Volumetric bone mineral density (vBMD), microarchitecture and finite element analysis were performed using high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius (DR) and tibia (DT) and compared with parameters from 160 female healthy controls matched by age and body mass index. Localized bone involvement was also analyzed using HR-pQCT in the metacarpophalangeal and proximal interphalangeal joints to identify erosions and osteophytes.

RESULTS

The mean age of RA patients was 39.4±6.7years and disease duration 9.8±5.3years. RA patients had impaired trabecular, cortical and bone strength parameters, at DR and DT, compared with healthy controls (p<0.05). Bone erosions and osteophytes were found in 75% and 41.3% of patients, respectively. Comparing patients with and without erosions, at DR and DT, a lower cortical vBMD (DR: 980±72 versus 1021±47mgHA/cm³ , p=0.03; DT:979±47 versus 1003±34 mgHA/cm³ , p=0.04) and higher cortical porosity (DR:2.8±2.5 versus 1.8±1.6%, p=0.04; and DT:3.7±1.6 versus 2.7±1.6%, p=0.01) were observed in patients with erosions. At the DR, osteophyte volume was positively correlated with trabecular vBMD (0.392, p=0.02), trabecular number (0.381, p=0.03) and stiffness (0.411, p=0.02), and negatively with trabecular separation (-0.364, p=0.04).

CONCLUSION

Our findings showed that premenopausal women with long-standing RA had systemic bone fragility at peripheral sites. Moreover, erosions were associated mainly with cortical bone fragility at the DR and DT, and osteophytes correlated with repair of trabecular bone at the radius.

The clinical application of high-resolution peripheral computed tomography (HR-pQCT) in adults: state of the art and future directions

High-resolution peripheral computed tomography (HR-pQCT) was developed to image bone microarchitecture in vivo at peripheral skeletal sites. Since the introduction of HR-pQCT in 2005, clinical research to gain insight into pathophysiology of skeletal fragility and to improve prediction of fractures has grown. Meanwhile, the second-generation HR-pQCT device has been introduced, allowing novel applications such as hand joint imaging, assessment of subchondral bone and cartilage thickness in the knee, and distal radius fracture healing. This article provides an overview of the current clinical applications and guidance on interpretation of results, as well as future directions. Specifically, we provide an overview of (1) the differences and reference data for HR-pQCT variables by age, sex, and race/ethnicity; (2) fracture risk prediction using HR-pQCT; (3) the ability to monitor response of anti-osteoporosis therapy with HR-pQCT; (4) the use of HR-pQCT in patients with metabolic bone disorders and diseases leading to secondary osteoporosis; and (5) novel applications of HR-pQCT imaging. Finally, we summarize the status of the application of HR-pQCT in clinical practice and discuss future directions. From the clinical perspective, there are both challenges and opportunities for more widespread use of HR-pQCT. Assessment of bone microarchitecture by HR-pQCT improves fracture prediction in mostly normal or osteopenic elderly subjects beyond DXA of the hip, but the added value is marginal. The prospects of HR-pQCT in clinical practice need further study with respect to medication effects, metabolic bone disorders, rare bone diseases, and other applications such as hand joint imaging and fracture healing. The mostly unexplored potential may be the differentiation of patients with only moderately low BMD but severe microstructural deterioration, which would have important implications for the decision on therapeutical interventions.

Computed tomography in rheumatology - From DECT to high-resolution peripheral quantitative CT

In this chapter, we discuss current updates and applications of Dual Energy Computed Tomography (DECT), iodine-DECT mapping, and high-resolution peripheral quantitative CT (HR-pQCT) in rheumatology. DECT provides a noninvasive diagnosis of gout and can help to differentiate gout from CPPD. Accuracy of DECT varies in various stages of gout. DECT needs specialized hardware, software, and skilled post-processing and interpretation. Sensitivity reduces significantly with deeper tissues such as hip and shoulder. Iodine map enables to delineate inflammatory lesions such as capsulitis and tenosynovitis by improving iodine contrast. Iodine quantification with an iodine map is a promising objective method to evaluate therapeutic effect of inflammatory arthritis. HR-pQCT allows for highly sensitive and specific measures of bone erosions and osteophytes in inflammatory joint diseases, documenting change over time, e.g. in cohorts undergoing immunosuppressive treatments. However, assessing the images requires trained readers, and (semi)-automated scripts to detect bone damage are still undergoing validation and further development.

Multi-Modal Imaging to Assess the Interaction Between Inflammation and Bone Damage Progression in Inflammatory Arthritis

Combining results from multiple imaging techniques (i.e., multi-modal imaging) through image registration can result in the better characterization of joint tissue characteristics. In the context of inflammatory arthritis conditions, high-resolution peripheral quantitative computed tomography (HR-pQCT) provides excellent bone contrast while magnetic resonance imaging (MRI) provides superior contrast and resolution of soft tissue and inflammatory characteristics. Superimposing these imaging results upon each other provides a robust characterization of the joint. In a preliminary study of nine rheumatoid arthritis (RA) participants in clinical remission, we acquired HR-pQCT and MR images of their 2nd and 3rd metacarpophalangeal (MCP) joints at two timepoints 6 months apart. We present the benefits of a multi-modal imaging approach, in which we demonstrate the ability to localize regions of inflammation with subtle changes in bone erosion volume. Using HR-pQCT and MRI to visualize bone damage and inflammation, respectively, will improve our understanding of the impact that subclinical inflammation has on bone damage progression, and demonstrating if bone repair occurs where inflammation is resolved. The presented multi-modal imaging technique has the potential to study the progression of bone damage in relation to inflammation that otherwise would not be possible with either imaging technique alone. The multi-modal image registration technique will be helpful to understanding the development and pathogenesis of RA-associated bone erosions. Additionally, multi-modal imaging may provide a technique to probe the tissue-level changes that occur as a result of treatment regimes.

High-Resolution Peripheral Quantitative Computed Tomography for Bone Evaluation in Inflammatory Rheumatic Disease

High resolution peripheral quantitative computed tomography (HR-pQCT) is a 3-dimensional imaging modality with superior sensitivity for bone changes and abnormalities. Recent advances have led to increased use of HR-pQCT in inflammatory arthritis to report quantitative volumetric measures of bone density, microstructure, local anabolic (e.g., osteophytes, enthesiophytes) and catabolic (e.g., erosions) bone changes and joint space width. These features may be useful for monitoring disease progression, response to therapy, and are responsive to differentiating between those with inflammatory arthritis conditions and healthy controls. We reviewed 69 publications utilizing HR-pQCT imaging of the metacarpophalangeal (MCP) and/or wrist joints to investigate arthritis conditions. Erosions are a marker of early inflammatory arthritis progression, and recent work has focused on improvement and application of techniques to sensitively identify erosions, as well as quantifying erosion volume changes longitudinally using manual, semi-automated and automated methods. As a research tool, HR-pQCT may be used to detect treatment effects through changes in erosion volume in as little as 3 months. Studies with 1-year follow-up have demonstrated progression or repair of erosions depending on the treatment strategy applied. HR-pQCT presents several advantages. Combined with advances in image processing and image registration, individual changes can be monitored with high sensitivity and reliability. Thus, a major strength of HR-pQCT is its applicability in instances where subtle changes are anticipated, such as early erosive progression in the presence of subclinical inflammation. HR-pQCT imaging results could ultimately impact decision making to uptake aggressive treatment strategies and prevent progression of joint damage. There are several potential areas where HR-pQCT evaluation of inflammatory arthritis still requires development. As a highly sensitive imaging technique, one of the major challenges has been motion artifacts; motion compensation algorithms should be implemented for HR-pQCT. New research developments will improve the current disadvantages including, wider availability of scanners, the field of view, as well as the versatility for measuring tissues other than only bone. The challenge remains to disseminate these analysis approaches for broader clinical use and in research.

The utility of multi-stack alignment and 3D longitudinal image registration to assess bone remodeling in rheumatoid arthritis patients from second generation HR-pQCT scans

BACKGROUND

Medical imaging plays an important role in determining the progression of joint damage in rheumatoid arthritis (RA). High resolution peripheral quantitative computed tomography (HR-pQCT) is a sensitive tool capable of evaluating bone microarchitecture and erosions, and 3D rigid image registration can be used to visualize and quantify bone remodeling over time. However, patient motion during image acquisition can cause a "stack shift" artifact resulting in loss of information and reducing the number of erosions that can be analyzed using HR-pQCT. The purpose of this study was to use image registration to improve the number of useable HR-pQCT scans and to apply image-based bone remodeling assessment to the metacarpophalangeal (MCP) joints of RA patients.

METHODS

Ten participants with RA completed HR-pQCT scans of the 2nd and 3rd MCP joints at enrolment to the study and at a 6-month follow-up interval. At 6-months, an additional repeat scan was acquired to evaluate reliability. HR-pQCT images were acquired in three individual 1 cm acquisitions (stacks) with a 25% overlap. We completed analysis first using standard evaluation methods, and second with multi-stack registration. We assessed whether additional erosions could be evaluated after multi-stack registration. Bone remodeling analysis was completed using registration and transformation of baseline and follow-up images. We calculated the bone formation and resorption volume fractions with 6-month follow-up, and same-day repositioning as a negative control.

RESULTS

13/57 (23%) of erosions could not be analyzed from raw images due to a stack shift artifact. All erosions could be volumetrically assessed after multi-stack registration. We observed that there was a median bone formation fraction of 2.1% and resorption fraction of 3.8% in RA patients over the course of 6 months. In contrast to the same-day rescan negative control, we observed median bone formation and resorption fractions of 0%.

CONCLUSIONS

Multi-stack image registration is a useful tool to improve the number of useable scans when analyzing erosions using HR-pQCT. Further, image registration can be used to longitudinally assess bone remodeling. These methods could be implemented in future studies to provide important pathophysiological information on the progression of bone damage.

Consensus approach for 3D joint space width of metacarpophalangeal joints of rheumatoid arthritis patients using high-resolution peripheral quantitative computed tomography

Background

Joint space assessment for rheumatoid arthritis (RA) by ordinal conventional radiographic scales is susceptible to floor and ceiling effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides superior resolution, and may detect earlier changes. The goal of this work was to compare existing 3D methods to calculate joint space width (JSW) metrics in human metacarpophalangeal (MCP) joints with HR-pQCT and reach consensus for future studies. Using the consensus method, we established reproducibility with repositioning as well as feasibility for use in second-generation HR-pQCT scanners.

Methods

Three published JSW methods were compared using datasets from individuals with RA from three research centers. A SPECTRA consensus method was developed to take advantage of strengths of the individual methods. Using the SPECTRA method, reproducibility after repositioning was tested and agreement between scanner generations was also established.

Results

When comparing existing JSW methods, excellent agreement was shown for JSW minimum and mean (ICC 0.987-0.996) but not maximum and volume (ICC 0.000-0.897). Differences were identified as variations in volume definitions and algorithmic differences that generated high sensitivity to boundary conditions. The SPECTRA consensus method reduced this sensitivity, demonstrating good scan-rescan reliability (ICC >0.911) except for minimum JSW (ICC 0.656). There was strong agreement between results from first- and second-generation HR-pQCT (ICC >0.833).

Conclusions

The SPECTRA consensus method combines unique strengths of three independently-developed algorithms and leverages underlying software updates to provide a mature analysis to measure 3D JSW. This method is robust with respect to repositioning and scanner generations, suggesting its suitability for detecting change.

Prospective Follow-Up of Cortical Interruptions, Bone Density, and Micro-structure Detected on HR-pQCT: A Study in Patients with Rheumatoid Arthritis and Healthy Subjects

OBJECTIVES

The purpose of the study was to prospectively investigate change (repair or progression) in the number, surface area and volume of cortical interruptions, bone density (vBMD) and micro-structural parameters assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) in finger joints of patients with rheumatoid arthritis (RA) treated with synthetic disease modifying anti-rheumatic drugs (sDMARDs) and/or biologic DMARDs (bDMARDs) over a 1-year follow-up period, and in comparison with healthy subjects (HS).

METHODS

Thirty-two patients with RA (221 joints, 53% on bDMARDs) and 32 HS (117 joints) were assessed at baseline and after 1 year using semi-automatic analysis of HR-pQCT images. Mean changes (group level) and the proportion of joints (joint level) with changes beyond the least significant change were calculated.

RESULTS

At baseline, 530 interruptions were identified in patients, and 136 in HS. The mean of the interruption parameters did not significantly change in either group Mean vBMD decreased more in patients than in HS (- 4.4 versus - 1.1 mgHA/cm³, respectively). In patients versus HS, proportionally more joints showed repair in interruption volume (6.6% versus 1.7%, respectively) and loss of vBMD (26.7% versus 12.9%, respectively). In patients on sDMARDs versus patients on bDMARDs, proportionally more joints showed progression in the number of interruptions and loss of vBMD (6.1% versus 1.8% and 31.3% versus 17.2%, respectively).

CONCLUSIONS

HR-pQCT is able to quantify bone repair and progression. Cortical interruption-, vBMD-, and micro-structure were impaired in RA, of which vBMD and micro-structure further deteriorated, particularly in patients on sDMARDs.