Is ultra low-dose CT with tin filtration useful for examination of SI joints? Can it replace X-ray in diagnostics of sacroiliitis?

Axial Imaging in Spondyloarthritis

Imaging plays a crucial role in diagnosing and forecasting treatment outcomes in axial spondyloarthritis. Conventional radiography may overlook patients in the initial stages of the disease, while MRI is sensitive in identifying inflammation early on. Computed tomography reliably detects structural abnormalities. Practicing rheumatologists must possess a fundamental understanding of interpreting both active inflammatory and structural lesions in axial spondyloarthritis.

ESR Essentials: Imaging of sacroiliitis-practice recommendations by ESSR

Sacroiliitis is commonly seen in patients with axial spondyloarthritis, in whom timely diagnosis and treatment are crucial to prevent irreversible structural damage. Imaging has a prominent place in the diagnostic process and several new imaging techniques have been examined for this purpose. We present a summary of updated evidence-based practice recommendations for imaging of sacroiliitis. MRI remains the imaging modality of choice for patients with suspected sacroiliitis, using at least four sequences: coronal oblique T1-weighted and fluid-sensitive sequences, a perpendicular axial oblique sequence, and a sequence for optimal evaluation of the bone-cartilage interface. Both active inflammatory and structural lesions should be described in the report, indicating location and extent. Radiography and CT, especially low-dose CT, are reasonable alternatives when MRI is unavailable, as patients are often young. This is particularly true to evaluate structural lesions, at which CT excels. Dual-energy CT with virtual non-calcium images can be used to depict bone marrow edema. Knowledge of normal imaging features in children (e.g., flaring, blurring, or irregular appearance of the articular surface) is essential for interpreting sacroiliac joint MRI in children because these normal processes can simulate disease. CLINICAL RELEVANCE STATEMENT: Sacroiliitis is a potentially debilitating disease if not diagnosed and treated promptly, before structural damage to the sacroiliac joints occurs. Imaging has a prominent place in the diagnostic process. We present a summary of practice recommendations for imaging of sacroiliitis, including several new imaging techniques. KEY POINTS: • MRI is the modality of choice for suspected inflammatory sacroiliitis, including a joint-line-specific sequence for optimal evaluation of the bone-cartilage interface to improve detection of erosions. • Radiography and CT (especially low-dose CT) are reasonable alternatives when MRI is unavailable. • Knowledge of normal imaging features in children is mandatory for interpretation of MRI of pediatric sacroiliac joints.

Enhancing the Diagnostic Accuracy of Sacroiliitis: A Machine Learning Approach Applied to Computed Tomography Imaging

Aims/Background Sacroiliitis is a challenging condition to diagnose accurately due to the subtle nature of its presentation in imaging studies. This study aims to improve the diagnostic accuracy of sacroiliitis by applying advanced machine learning techniques to computed tomography (CT) images. Methods We employed five convolutional neural network (CNN) models-Visual Geometry Group 16-layer Network (VGG16), ResNet101, DenseNet, Inception-v4, and ResNeXt-50-to analyze a dataset of 830 CT images, including both sacroiliitis and non-sacroiliitis cases. Each model's performance was evaluated using metrics such as accuracy, precision, recall, F1 score, Receiver Operating Characteristic (ROC), and Area Under the Curve (AUC). The interpretability of the models' decisions was enhanced using Gradient-weighted Class Activation Mapping (Grad-CAM) visualization. Results The ResNeXt-50 and Inception-v4 models demonstrated superior performance, achieving the highest accuracy and F1 scores among the tested models. Grad-CAM visualizations offered insights into the decision-making processes, highlighting the models' focus on relevant anatomical features critical for accurate diagnosis. Conclusion The use of CNN models, particularly ResNeXt-50 and Inception-v4, significantly improves the diagnosis of sacroiliitis from CT images. These models not only provide high diagnostic accuracy but also offer transparency in their decision-making processes, aiding clinicians in understanding and trusting Artificial Intelligence (AI)-driven diagnostics.

Clash of the titans: Current CT and CT-like imaging modalities in sacroiliitis in spondyloarthritis

Sacroiliitis is characterised by active and structural changes of the joint. While the Assessment of Spondyloarthritis international Society (ASAS) classification criteria stress the importance of bone marrow inflammation, recent reports suggest that osteitis can occur in various diseases, mechanical conditions and healthy individuals. Thus, structural lesions such as joint surface erosion and ankylosis are important factors for differential diagnosis. Various imaging modalities are available to examine these changes. However, computed tomography (CT) is generally considered the reference standard. Nonetheless, recent advances in magnetic resonance imaging (MRI) allow for direct bone imaging and the reconstruction of CT-like images that can provide similar information. This way, the ability of MRI to detect and measure structural lesions is strengthened. The aim of this review is to provide an overview of the pros and cons of CT and CT-like imaging modalities in sacroiliitis.

Is it time to move on from pelvic radiography as the first-line imaging modality for suspected sacroiliitis?

PURPOSE OF REVIEW

Pelvic radiography in which structural lesions characteristic of sacroiliitis can be detected, is recommended as the first imaging modality when axial spondyloarthritis (axSpA) is suspected clinically. However, cross-sectional modalities like computed tomography (CT) and magnetic resonance imaging (MRI) are superior to radiographs for diagnosing sacroiliitis. Thus, we currently debate the role of radiography as first imaging modality in the diagnostic workup of axSpA.

RECENT FINDINGS

Diagnosing sacroiliitis on pelvic radiographs is challenging with large interobserver and intraobserver variation. Low-dose CT (ldCT) of the sacroiliac joints (SIJs) was proved to be more sensitive and reliable than radiographs with comparable ionizing radiation exposure. MRI is the preferred modality for detecting early SIJ inflammation, well before structural lesions evolve. New, promising MRI sequences sensitive to cortical bone improve erosion detection, making MRI a one-stop shop for the diagnosis of sacroiliitis.

SUMMARY

Given the debatable additive value of pelvic radiographs for the detection of sacroiliitis, and the presence of excellent alternatives for imaging the bony cortex of the SIJs such as ldCT and MRI with state-of-the-art sequences sensitive to cortical bone, it is high time to discuss the use of these more accurate modalities instead of radiographs.

Zero echo time MRI improved detection of erosions and sclerosis in the sacroiliac joint in comparison with LAVA-flex

Background

T1-weighted spoiled 3D Gradient Recalled Echo pulse sequences, exemplified by Liver Acquisition with Volume Acceleration-flexible MRI (LAVA-Flex), are currently the preferred MR sequence for detecting erosions of the sacroiliac joint (SIJ). However, zero echo time MRI (ZTE) is recently reported to provide excellent visualization of the cortical bone.

Purpose

To directly compare the diagnostic accuracy of ZTE and LAVA-Flex in the detection of structural lesions of the SIJ, including erosions, sclerosis and joint space changes.

Materials and methods

Two readers independently reviewed the ldCT, ZTE and LAVA-Flex images of 53 patients diagnosed as axSpA and scored the erosions, sclerosis and joint space changes. Sensitivity, specificity and Cohen's kappa (κ) of ZTE and LAVA-Flex were calculated, while McNemar's test was employed to compare the two sequences for the positivity of detecting the structural lesions.

Results

Analysis of diagnostic accuracy showed a higher sensitivity of ZTE in comparison with LAVA-Flex in the depiction of erosions (92.5% vs 81.5%, p<0.001), especially first-degree erosions (p<0.001) and second-degree erosions (p<0.001), as well as sclerosis (90.6% vs 71.2%, p<0.001), but not joint space changes (95.2% vs 93.8%, p=0.332). Agreement with ldCT was also higher in ZTE in the detection of erosions than LAVA-Flex as indicated by the κ values (0.73 vs 0.47), as well as in the detection of sclerosis (0.92 vs 0.22).

Conclusion

With ldCT as the reference standard, ZTE could improve diagnostic accuracy of erosions and sclerosis of the SIJ in patients suspected of axSpA, in comparison with LAVA-Flex.

Use of Imaging in Axial Spondyloarthritis for Diagnosis and Assessment of Disease Remission in the Year 2022

Medical imaging remains the cornerstone of diagnostics and follow-up of axial spondyloarthritis (axSpA) patients. With the lack of specific biomarkers allowing monitoring of disease activity and progression, clinicians refer to imaging modalities for accurate evaluation of the axSpA burden. Technological advances and increasing availability of modern imaging techniques such as MRI have enabled faster diagnosis of the disease, hence dramatically changed the diagnostic delay and improved the prognosis and functional outcomes for axSpA patients.Active sacroiliitis as visualized by MRI has been widely accepted as a diagnostic tool, and definitions of inflammatory and structural lesions within the axial skeleton have been developed. Recently, it has been acknowledged that bone marrow edema, suggestive of sacroiliitis, is a common finding among non-SpA patients, and could be attributed to mechanical loading or accumulate with age in healthy individuals. Therefore, it is crucial to distinguish between true pathological and concealing imaging findings, not only for diagnostic but also for disease remission purposes. New imaging modalities, aimed for in vivo visualization of specific molecular processes, could be employed to cross-validate findings from techniques used in daily clinical practice. This review critically evaluates the use of different imaging modalities for diagnosis and assessment of disease remission in axSpA in the year 2022.

Novel imaging techniques for sacroiliac joint assessment

PURPOSE OF REVIEW

Imaging of the sacroiliac joints is one of the cornerstones in the diagnosis and monitoring of axial spondyloarthritis. We aim to present an overview of the emerging imaging techniques for sacroiliac joint assessment and provide an insight into their relevant benefits and pitfalls.

RECENT FINDINGS

Evaluation of structural and active inflammatory lesions in sacroiliitis are both important for understanding the disease process. Dual-energy computed tomography (CT) can detect inflammatory bone marrow edema in the sacroiliac joints and provides an alternative for magnetic resonance imaging (MRI). Three-dimensional gradient echo sequences improve the visualization of erosions on MRI. Susceptibility weighted MRI and deep learning-based synthetic CT are innovative MRI techniques that allow for generating 'CT-like' images and better depict osseous structural lesions than routine MRI sequences.

SUMMARY

New imaging innovations and developments result in significant improvements in the imaging of spondyloarthritis. Advanced MRI techniques enhance its potential for the accurate detection of structural and active inflammatory lesions of sacroiliitis in one single imaging session.

Low-dose computed tomography for axial spondyloarthritis: update on use and limitations

PURPOSE OF REVIEW

Recent developments in low-dose computed tomography (ldCT) have greatly reduced radiation exposure levels. This article reviews what a ldCT is and its use and limitations for imaging axial spondyloarthritis.

RECENT FINDINGS

Detection of structural damage in bone with CT is far superior to radiography and ldCT of the sacroiliac joints (SIJ) can now be done at radiation exposure levels equivalent to, or even less than, conventional radiography. ldCT should be considered a 'first-choice' test for arthritis imaging, and wherever available, SIJ ldCT may completely replace conventional radiography. Radiation exposure in the spine with ldCT is lower than conventional CT. However, it is unclear whether the additional information regarding structural damage changes in the spine provided by ldCT will alter patient management sufficiently often to merit switching from spinal radiography to ldCT in routine clinical practice. In addition, ldCT cannot assess osteitis disease activity for which MRI remains the best test.

SUMMARY

ldCT of the sacroiliac joints (SIJ) can be done at radiation exposure levels equivalent to, or less than, radiography and ldCT may completely replace SIJ radiography. However, the role of spinal ldCT for spondyloarthritis is not clear and MRI is far superior for detecting disease activity.