Timothy J P Bray

A diffusion-based quantification technique for assessment of sacroiliitis in adolescents with enthesitis-related arthritis

Objective: To investigate the use of a quantitative diffusion-weighted imaging (DWI) tool for measuring inflammation of the sacroiliac joints (SIJs) in enthesitis-related arthritis (ERA). Methods: A retrospective study was performed with institutional review board approval. Subjects were adolescents who had undergone MRI of the SIJs since January 2010. 10 patients with a clinical diagnosis of ERA and 10 controls with a clinical diagnosis of mechanical back pain were assessed. Axial T1 weighted, short tau inversion recovery (STIR) and DWI (b-values 0, 50, 100, 300 and 600 mm2 s−1) images were acquired. Apparent diffusion coefficient (ADC) maps were generated using a monoexponential fit. On each of four slices, two to three linear regions-of-interest were placed on each joint. Normalized ADC (nADC) values were defined as joint ADC divided by a reference ADC derived from normal sacral bone. STIR images were scored using a modification of an established technique. The correlation between nADC values and STIR scores was evaluated using Spearmans rank correlation. Results: Mean nADC values were significantly higher in cases than in controls (p = 0.0015). There was a strong correlation between STIR scores and nADC values (R = 0.85). Conclusion: ADC values are significantly increased in inflamed SIJs compared with controls. There is a good correlation between this diffusion-based method and STIR scores of inflammation. Advances in knowledge: We have described and provisionally validated a method for quantifying the severity of inflammation in the SIJs in ERA using ADC measurements. This method is quick, is reproducible and could potentially be automated.

Simultaneous Quantification of Bone Edema/Adiposity and Structure in Inflamed Bone Using Chemical Shift-Encoded MRI in Spondyloarthritis

To evaluate proton density fat fraction (PDFF) and R2* as markers of bone marrow composition and structure in inflamed bone in patients with spondyloarthritis.

Diffusion-weighted imaging is a sensitive biomarker of response to biologic therapy in enthesitis-related arthritis.

Objective. The aim was to evaluate diffusion-weighted imaging (DWI) as a tool for measuring treatment response in adolescents with enthesitis-related arthropathy (ERA). Methods. Twenty-two adolescents with ERA underwent routine MRI and DWI before and after TNF inhibitor therapy. Each patient’s images were visually scored by two radiologists using the Spondyloarthritis Research Consortium of Canada system, and sacroiliac joint apparent diffusion coefficient (ADC) and normalized ADC (nADC) were measured for each patient. Therapeutic clinical response was defined as an improvement of ⩾ 30% physician global assessment and radiological response defined as ⩾ 2.5-point reduction in Spondyloarthritis Research Consortium of Canada score. We compared ADC and nADC changes in responders and non-responders using the Mann–Whitney–Wilcoxon test. Results. For both radiological and clinical definitions of response, reductions in ADC and nADC after treatment were greater in responders than in non-responders (for radiological response: ADC: P < 0.01; nADC: P = 0.055; for clinical response: ADC: P = 0.33; nADC: P = 0.089). ADC and nADC could predict radiological response with a high level of sensitivity and specificity and were moderately sensitive and specific predictors of clinical response (the area under the receiver operating characteristic curves were as follows: ADC: 0.97, nADC: 0.82 for radiological response; and ADC: 0.67, nADC: 0.78 for clinical response). Conclusion. DWI measurements reflect the response to TNF inhibitor treatment in ERA patients with sacroiliitis as defined using radiological criteria and may also reflect clinical response. DWI is more objective than visual scoring and has the potential to be automated. ADC/nADC could be used as biomarkers of sacroiliitis in the clinic and in clinical trials.

Diagnostic utility of whole body Dixon MRI in multiple myeloma: A multi-reader study

Objective To determine which of four Dixon image types [in-phase (IP), out-of-phase (OP), fat only (FO) and water-only (WO)] is most sensitive for detecting multiple myeloma (MM) focal lesions on whole body MRI (WB-MRI) images. Methods Thirty patients with clinically-suspected MM underwent WB-MRI at 3 Tesla. Unenhanced IP, OP, FO and WO Dixon images were generated and read by four radiologists. On each image type, each radiologist identified and labelled all visible myeloma lesions in the bony pelvis. Each identified lesion was compared with a reference standard consisting of pre- and post-contrast Dixon and diffusion weighted imaging (read by a further consultant radiologist) to determine whether the lesion was truly positive. Lesion count, true positives, sensitivity, and positive predictive value were compared across the four Dixon image types. Results Lesion count, true positives, sensitivity and confidence scores were all significantly higher on FO images than on IP images (p>0.05). Discussion FO images are more sensitive than other Dixon image types for MM focal lesions, and should be preferentially read by radiologists to improve diagnostic accuracy and reporting efficiency.

Association of the apparent diffusion coefficient with maturity in adolescent sacroiliac joints

To determine the extent to which apparent diffusion coefficient (ADC) values vary with skeletal maturity in adolescent joints.

Fat fraction mapping using magnetic resonance imaging: insight into pathophysiology

Adipose cells have traditionally been viewed as a simple, passive energy storage depot for triglycerides. However, in recent years it has become clear that adipose cells are highly physiologically active and have a multitude of endocrine, metabolic, haematological and immune functions. Changes in the number or size of adipose cells may be directly implicated in disease (e.g. in the metabolic syndrome), but may also be linked to other pathological processes such as inflammation, malignant infiltration or infarction. MRI is ideally suited to the quantification of fat, since most of the acquired signal comes from water and fat protons. Fat fraction (FF, the proportion of the acquired signal derived from fat protons) has, therefore, emerged as an objective, image-based biomarker of disease. Methods for FF quantification are becoming increasingly available in both research and clinical settings, but these methods vary depending on the scanner, manufacturer, imaging sequence and reconstruction software being used. Careful selection of the imaging method-and correct interpretation-can improve the accuracy of FF measurements, minimize potential confounding factors and maximize clinical utility. Here, we review methods for fat quantification and their strengths and weaknesses, before considering how they can be tailored to specific applications, particularly in the gastrointestinal and musculoskeletal systems. FF quantification is becoming established as a clinical and research tool, and understanding the underlying principles will be helpful to both imaging scientists and clinicians.

Discordant inflammatory changes in the apophyseal and sacroiliac joints: serial observations in enthesitis-related arthritis

OBJECTIVE To determine the extent to which inflammation of the sacroiliac joints (SIJs) and apophyseal joints (AJs) changes concordantly after treatment in enthesitis-related arthritis (ERA). METHODS A retrospective study was performed with institutional review board approval. 31 young patients with ERA who had been scanned between March 2009 and November 2014 were included. All patients had post-contrast imaging of the SIJs and lumbar spine and short tau inversion-recovery (STIR) images of the SIJs. The severity of sacroiliitis was scored using a modification of an established technique, and inflammation of the AJs was evaluated using a recently described grading system. The changes in SIJ and AJ scores after treatment were classified as either concordant or discordant, and the proportion of scan pairs in these groups was recorded. In addition, the correlation between change in SIJ STIR score (Δnfla) and change in AJ score (ΔAJ) was assessed using Spearmans correlation coefficient. RESULTS Of a total of 43 scan pairs, the changes in inflammation were concordant in 16 scan pairs and discordant in 27 scan pairs. There was no significant correlation between Δnfla and ΔAJ (R = 0.14, p = 0.37). CONCLUSION Inflammatory changes in the SIJs and AJs are often discordant. This may be a reason why patients experience ongoing back pain despite apparent improvement in one or the other site. ADVANCES IN KNOWLEDGE Inflammation may behave differently at different anatomical sites. The SIJs and AJs should both be imaged in patients with ERA with back pain.

Low back pain in adolescents with inflammatory arthritis can be due to lumbar spine apophyseal joint inflammation, and this requires contrast enhancement for adequate assessment: comment on the article by Weiss et al

To the Editor: We read with interest the recent report by Weiss et al on magnetic resonance imaging (MRI) for detection of inflammatory sacroiliitis in children (1). We agree with the authors that MRI of the sacroiliac joints in children and adolescents does not require the use of intravenous gadolinium contrast enhancement for the diagnosis of sacroiliitis. However, low back pain in patients with inflammatory spondyloarthritis (SpA) can be due to causes other than sacroiliitis. In our experience at the Arthritis Research UK Centre for Adolescent Rheumatology (www.centre-for-adolescentrheumatology.org), we have demonstrated that 38% of 58 adolescent patients (median age 16.5 years) with enthesitis-related arthritis (as defined by the revised International League of Associations for Rheumatology classification criteria for juvenile idiopathic arthritis subtypes) (2) had apophyseal joint inflammation of the lumbar spine, and this was seen with or without concurrent sacroiliitis (3); in 23% of these patients with apophyseal joint synovitis there was no MRI evidence of definite sacroiliitis. Apophyseal joint inflammation was seen only on contrast-enhanced scans in a large proportion of the patients (70% of those with apophyseal joint inflammation). Even among patients with the most severe apophyseal joint changes (grade 3: synovitis and bone marrow edema), inflammation was visualized on water-sensitive images in only half the cases, as compared to postcontrast scans. Furthermore, sacroiliitis and apophyseal joint synovitis can change independently of one another (4). Persistent or deteriorating lumbar apophyseal joint synovitis can occur in patients with improving sacroiliitis and could account for persistent inflammatory pain in patients in whom disease would appear to be resolving if only the sacroiliac joints were examined. We acknowledge that more research needs to be undertaken to define the association between inflammatory lower back pain, sacroiliitis, and apophyseal joint synovitis in children and adolescents with enthesitis-related arthritis/childhoodonset SpA. Hence, the report by Weiss et al is a welcome addition to the evidence base in the study of this important area. However, given our findings that have been recently reported (3), we propose that clinicians use a low threshold for including imaging of the lumbar spine as an addition to the MRI scan of the sacroiliac joints in all young patients with inflammatory back pain, both at the time of diagnosis and during disease followup to monitor response. If the lumbar spine is imaged, then contrast enhancement to facilitate adequate assessment of the spinal component of this inflammatory disease is required. Timothy P. Bray, MBBChir Kanimozhi Vendhan, MBBS, DMRD, FRCR University College London Corinne Fisher, MBBCh Debajit Sen, FRCP, DCH Yiannis Ioannou, MBBS, BMedSci, PhD, FRCP University College London and Arthritis Research UK Centre for Adolescent Rheumatology Margaret A. Hall-Craggs, FRCR, MD University College London London, UK

Quantifying bone structure, micro-architecture, and pathophysiology with MRI

The radiology of bone has been transformed by magnetic resonance imaging, which has the ability to interrogate bones complex architecture and physiology. New techniques provide information about both the macrostructure and microstructure of bone ranging from micrometre detail to the whole skeleton. Furthermore functional information about bone physiology can be used to detect disease early before structural changes occur. The future of bone imaging is in quantifying the anatomical and functional information to diagnose and monitor disease more precisely. This review explores the state of the art in quantitative MRI bone imaging.

Sacroiliac Joint Ankylosis In Young Spondyloarthritis Patients Receiving Biologic Therapy: Observation of Serial MRI scans

To assess the temporal relationship between initiating biologic therapy and magnetic resonance imaging (MRI) scores of inflammation and structural damage in young patients with spondyloarthritis.