Detection of Active Sacroiliitis with Ankylosing Spondylitis through Intravoxel Incoherent Motion Diffusion-Weighted MR Imaging. Eur Radiol. 2015;25:2754-2763. [PMID: 25678080 DOI: 10.1007/s00330-015-3634-2]

Intravoxel Incoherent Motion Factors Affecting Collapse and Nonunion of Osteoporotic Vertebral Fracture

STUDY DESIGN

Longitudinal study.

OBJECTIVES

Intravoxel incoherent motion (IVIM), a magnetic resonance imaging (MRI) scanning technique that applies diffusion-weighted imaging (DWI), is effective for the quantitative assessment of malignant tumors of the vertebral bone. We hypothesized that IVIM parameters of vertebral bodies are associated with the prognosis of osteoporotic vertebral fracture (OVF). We aimed to explore the relationships between IVIM parameters for vertebral collapse and non-union after OVF and calculate the cut-off values of these parameters for vertebral collapse and non-union.

METHODS

A total of 150 patients with acute OVF (150 women; mean age: 79.1 ± 7.4 years) were included and treated conservatively with bracing. MRI was performed at the time of injury. IVIM parameters, such as apparent diffusion coefficient (ADC), molecular diffusion coefficient (D), and perfusion-related diffusion (D*) were recorded. The patients were classified into 3 groups: low-collapse (height loss of ≤50%), high-collapse (height loss of >50%), and non-union. We compared ADC, D, and D* among the low-collapse, high-collapse, and non-union groups and performed a receiver operating characteristic (ROC) curve analysis to determine the boundary values of the high-collapse and non-union groups.

RESULTS

The low-collapse, high-collapse, and non-union groups had no significant differences in ADC and D. However, D* differed significantly among the 3 groups. ROC analysis revealed cut-off values of 19.0 × 10-3 mm2/s and 12.3 × 10-3 mm2/s for the high-collapse and non-union groups, respectively.

CONCLUSIONS

D* is a significant prognostic indicator for high-collapse and non-union groups with OVF. This suggests that D* should be considered when assessing OVF.

Whole-joint histogram analysis of different models of diffusion weighted imaging in evaluating disease activity of axial spondyloarthritis

OBJECTIVES

To assess whole-joint histogram analysis of mono-exponential and bi-exponential diffusion weighted and diffusion kurtosis imaging in evaluating disease activity of axial spondyloarthritis (axSpA).

METHODS

A total of 82 patients with axSpA who underwent both DKI and multi b diffusion weighted imaging of the sacroiliac joints were divided into active and inactive disease groups based on clinical activity indices. Another 17 patients with nonspecific low back pain were included as a control group. The SPARCC scoring system was used to assess the level of sacroiliac joint bone marrow edema. Histogram parameters of apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion fraction (f), pseudodiffusion coefficient (D*), mean kurtosis (MK), and mean diffusivity (MD) were calculated. Regions of interest were placed covering the entire sacroiliac joint. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance of imaging parameters in distinguishing different groups. Regression analysis was applied to determine the correlation between imaging parameters and clinical activity indices.

RESULTS

All of the histogram parameters distinguished the active from inactive groups with a low area under the curve (AUC) (max AUCs≤0.71), while the SPARCC score failed to differentiate the two groups (p = 0.08). MD, MK, D, D*, and ADC showed good performance in differentiating active and inactive from control groups (max AUC = 0. 81 ~ 0.98). f50 differentiated the active from control groups with an AUC of 0.72, significantly lower than the maximum AUC for MD, MK, D, ADC, and SPARCC score (all p < 0.05). The max AUC of MD in differentiating inactive from control groups was significantly higher than that of D* and the SPARCC score. MD, D, D*, f, and ADC were positively correlated with BASDAI, while MK was negatively correlated with BASDAI. Only MD was positively correlated with hsCRP.

CONCLUSIONS

Whole-joint histogram analysis of mono-exponential, bi-exponential diffusion weighted, and diffusion kurtosis imaging showed good diagnostic performance in differentiating active and inactive axSpA from patients with non-specific back pain. All the imaging parameters were correlated with BASDAI except for SPARCC score. Only DKI-derived MD was correlated with an increase in hsCRP, suggesting its potential use as an imaging biomarker for disease activity in axSpA.

ADVANCES IN KNOWLEDGE

1. No significant difference was found between the three models of diffusion weighted imaging in evaluating disease activity of axial spondyloarthritis.2. Only DKI-derived MD was correlated with an increase in hsCRP, suggesting its potential use as an imaging biomarker for disease activity in axSpA.

Quantitative magnetic resonance imaging (qMRI) in axial spondyloarthritis

Imaging, and particularly MRI, plays a crucial role in the assessment of inflammation in rheumatic disease, and forms a core component of the diagnostic pathway in axial spondyloarthritis. However, conventional imaging techniques are limited by image contrast being non-specific to inflammation and a reliance on subjective, qualitative reader interpretation. Quantitative MRI methods offer scope to address these limitations and improve our ability to accurately and precisely detect and characterise inflammation, potentially facilitating a more personalised approach to management. Here, we review quantitative MRI methods and emerging quantitative imaging biomarkers for imaging inflammation in axial spondyloarthritis. We discuss the potential benefits as well as the practical considerations that must be addressed in the movement toward clinical translation of quantitative imaging biomarkers.

Water Fraction Ratio of the Sacroiliac Joint Subchondral Bone Marrow in Patients with Ankylosing Spondylitis Predicts the Degree of Disease Activity

Objectives: Ankylosing spondylitis (AS) is a chronic inflammatory arthritis with characteristic involvement of the spine and sacroiliac joints. MRI may be the only indicator of disease activity or response. This study aimed to use a novel water fraction measurement technique on MRI as a biomarker to predict disease activity in patients with AS. Methods: We enrolled 39 patients (18 men [mean age, 38.6 years; range, 18−59 years] and 21 women [mean age, 39.3 years; range, 23−61 years]) who were clinically diagnosed with AS and underwent MRI, including mDixon sequences. Water fraction values of sacroiliac joint subchondral bone marrow were derived from the mDixon sequences. The Ankylosing Spondylitis Disease Activity Score (ASDAS) was recorded using clinical information and laboratory values from medical records. Multiple linear regression, Firth logistic regression, and intraclass correlation coefficients were used for the statistical analysis. Results: In multiple linear regression, water fraction, subchondral bone marrow edema, subchondral bone erosion, and subchondral bone marrow enhancements were significantly associated with ASDAS with C-reactive protein (ASDAS-CRP). The water fraction parameters showed a good linear correlation with ASDAS-CRP and ASDAS with erythrocyte sedimentation rate (ASDAS-ESR) (beta coefficient = 1.98, p < 0.001 and beta coefficient = 1.60, p = 0.003). Firth logistic regression showed that water fraction was a significant predictor of ASDAS-CRP but not ASDAS-ESR. The intraclass correlation coefficient showed excellent repeatability for the three repeated measures of the water fraction. Conclusion: Water fraction parameter could be a good imaging biomarker of disease activity status. The sacroiliac joint evaluated by mDixon MRI may be a promising biomarker of disease progression in patients with spondyloarthritis.

Preliminary study of monoexponential, biexponential, and stretched-exponential models of diffusion-weighted MRI and diffusion kurtosis imaging on differential diagnosis of spinal metastases and chordoma

PURPOSE

Quantitative comparison of diffusion parameters from various models of diffusion-weighted (DWI) and diffusion kurtosis (DKI) imaging for distinguishing spinal metastases and chordomas.

METHODS

DWI and DKI examinations were performed in 31 and 13 cases of spinal metastases and chordomas, respectively. DWI derived apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudo diffusion coefficient (D*), perfusion fraction (f), water molecular distributed diffusion coefficient (DDC), and intravoxel water diffusion heterogeneity (α). DKI derived mean diffusivity (MD) and mean kurtosis (MK). Independent sample t-testing compared statistical differences among parameters. Sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve were determined. Pearson correlation analysis evaluated the parameters' correlations.

RESULTS

ADC, D, f, DDC, α, and MD were significantly lower in spinal metastases than chordomas (all P < 0.05). MK was significantly higher in spinal metastases than chordomas (P < 0.05). D had the highest area under the ROC curve (AUC) of 0.886, greater than MD (AUC = 0.706) or DDC (AUC = 0.742) in differentiating the two tumors (both P < 0.05). Combining D with f and α statistically significantly increased the AUC for diagnosis (to 0.995) relative to D alone (P < 0.05). There was a certain correlation among DDC, ADC, and D (all P < 0.05).

CONCLUSIONS

Monoexponential, biexponential, and stretched-exponential models of DWI and DKI can potentially differentiate spinal metastases and chordomas. D combined with f and α performed best.

Magnetic resonance image compilation sequence to quantitatively detect active sacroiliitis with axial spondyloarthritis

BACKGROUND

To evaluate the diagnostic value of quantitative parameters [T1, T2, and proton density (PD) value] generated from magnetic resonance image compilation (MAGiC) sequence for active sacroiliitis in the patients with axial spondyloarthritis (ax-SpA).

METHODS

A total of 90 consecutive ax-SpA patients were recruited and divided into an active group (n=48) and inactive group (n=42) based on the Spondyloarthritis Research Consortium Canada (SPARCC) score in this prospective study. In addition, 47 healthy volunteers were recruited as the control group. All participants underwent magnetic resonance (MR) scanning (including MAGiC sequence and T2 mapping sequence) to obtain the T1 value, T2 value, PD value of MAGiC sequence (MAGiC T1 value, T2 value, PD value), and the T2 value of T2 mapping sequence (T2 map T2 value). Intraclass correlation coefficients (ICC) were calculated to assess the inter‑ and intra‑observer agreement. The correlation between the MAGiC T2 value and the T2 map T2 value was analyzed using Spearman's Rho. One-way analysis of variance (ANOVA) and receiver operating characteristic (ROC) analysis were performed for all parameters.

RESULTS

For the active group, inactive group, and control group, the MAGiC T1 value, T2 value, PD value, and T2 map T2 value were (1,700.91±725.40, 546.58±59.49, 640.25±95.79 ms), (129.37±23.85, 117.16±20.37, 90.52±12.05 ms), (76.47±15.92, 82.69±9.51, 75.51±9.17 pu), and (96.75±16.06, 87.96±9.27, 82.03±10.17 ms), respectively. The difference of the MAGiC T1 value and the MAGiC T2 value in the three groups was statistically significant (P<0.05). The MAGiC PD value was only statistically significant between inactive and control groups (P=0.001). When comparing the ROC curves of quantitative values among the three groups, MAGiC T1 value showed higher diagnostic efficacy than MAGiC T2 value between the active and inactive groups (MAGiC T1AUC: 0.971, MAGiC T2AUC: 0.655, P<0.0001), and the MAGiC T2 value showed higher diagnostic efficacy than T2 map T2 value between the active group and control group, and the inactive group and control group (MAGiC T2AUC: 0.940, T2 map T2AUC: 0.784, P=0.0021; MAGiC T2AUC: 0.877, T2 map T2AUC: 0.644, P=0.0011). The consistency of measurements was excellent (ICC =0.972-0.998). The MAGiC T2 value was positively correlated with the T2 map T2 value, but with a low correlation (r=0.402; P<0.001).

CONCLUSIONS

A significant difference was detected between the MAGiC T1 and T2 values among the three groups, while MAGiC PD value had limited diagnostic value. MAGiC T1 value was better at differentiating the active group and inactive group than MAGiC T2 value. MAGiC T2 value was better at differentiating the active group and control group, the inactive group and control group than T2 map T2 value.

Detection of the disease activity with ankylosing spondylitis through intravoxel incoherent motion diffusion-weighted MR imaging of sacroiliac joint

OBJECTIVE

To explore the value of the quantitative parameter of intravoxel incoherent motion diffusion (IVIM-DWI) at 3.0 T MRI of the sacroiliac joint in differentiating different disease activity statuses of ankylosing spondylitis (AS) and to compare it with traditional diffusion-weighted imaging (DWI) and Spondyloarthritis Research Consortium of Canada (SPARCC) score.

METHODS

56 AS patients (active group, inactive group) and 24 healthy controls were included. Clinical data, quantitative parameters of IVIM-DWI MR images and the SPARCC scores were collected. The Kruskal-Wallis test was used to compare the differences between the groups. Receiver operating characteristic (ROC) curve analysis of histogram data and the SPARCC scores identified the efficacy of the three groups. The Spearman correlation coefficients were used to analyse the correlation between the quantitative IVIIM-DWI parameters and the SPARCC score.

RESULTS

The f (10th percentile) and SPARCC score of the active group were significantly higher than those of the inactive group. The f (10th, 25th, 50th percentiles), Dslow (average, entropy, 10th ~ 90 th percentiles), Dfast (kurtosis, skewness), ADC (average, 10th ~ 90 th percentiles) and the SPARCC score of the active group were significantly higher than the control group (p < 0.05). The AUC of the SPARCC score was the highest (0.799) in the identification between the active and inactive groups, and the sensitivity and specificity were 69.23 and 82.35%, respectively, at the cut-off value of 12. The SPARCC score was positively correlated with each percentile and the average value.

CONCLUSIONS

Quantitative IVIIM-DWI parameters are helpful for the identification of different AS disease activity levels and are superior to traditional DWI. IVIM-DWI quantitative parameters had a good correlation with the SPARCC score.

ADVANCES IN KNOWLEDGE

A new MR technology-quantitative parameters of IVIM-DWI contribute to the identification of AS disease activity. IVIM-DWI quantitative parameters were well correlated with the SPARCC score.

Intravoxel Incoherent Motion Imaging on Sacroiliitis in Patients With Axial Spondyloarthritis: Correlation With Perfusion Characteristics Based on Dynamic Contrast-Enhanced Magnetic Resonance Imaging

BACKGROUND

To prospectively explore the relationship between intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) parameters of sacroiliitis in patients with axial spondyloarthritis (axSpA).

METHODS

Patients with initially diagnosed axSpA prospectively underwent on 3.0 T MRI of sacroiliac joint (SIJ). The IVIM parameters (D, f, D ^*) were calculated using biexponential analysis. K ^trans, K _ep, V _e, and V _p from DCE-MRI were obtained in SIJ. The uni-variable and multi-variable linear regression analyses were used to evaluate the correlation between the parameters from these two imaging methods after controlling confounders, such as bone marrow edema (BME), age, agenda, scopes, and localization of lesions, and course of the disease. Then, their correlations were measured by calculating the Pearson's correlation coefficient (r).

RESULTS

The study eventually enrolled 234 patients (178 men, 56 women; mean age, 28.51 ± 9.50 years) with axSpA. With controlling confounders, D was independently related to K ^trans (regression coefficient [b] = 27.593, p < 0.001), K _ep (b = -6.707, p = 0.021), and V _e (b = 131.074, p = 0.003), whereas f and D ^* had no independent correlation with the parameters from DCE MRI. The correlations above were exhibited with Pearson's correlation coefficients (r) (r = 0.662, -0.408, and 0.396, respectively, all p < 0.001).

CONCLUSION

There were independent correlations between D derived from IVIM DWI and K ^trans, K _ep, and V _e derived from DCE-MRI. The factors which affect their correlations mainly included BME, gender, and scopes of lesions.

Improved Performance of Compartments in Detecting the Activity of Axial Spondyloarthritis Based on IVIM DWI with Optimized Threshold b Value

Purpose

To explore the diagnostic performance of the optimized threshold b values on IVIM to detect the activity in axial spondyloarthritis (axSpA) patients.

Method

40 axSpA patients in the active group, 144 axSpA patients in the inactive group, and 20 healthy volunteers were used to evaluate the tissue diffusion coefficient (D_slow), perfusion fraction (f), and pseudodiffusion coefficient (D_fast) with b thresholds of 10, 20, and 30 s/mm². The Kruskal-Wallis test and one way ANOVA test was used to compare the different activity among the three groups in axSpA patients, and receiver operating characteristic (ROC) curve analysis was applied to evaluate the performance for D_slow, f, and D_fast to detect the activity in axSpA patients, respectively.

Results

D_slow demonstrated a statistical difference between two groups (P < 0.05) with all threshold b values. With the threshold b value of 30 s/mm², f could discriminate the active from control groups (P < 0.05). D_slow had similar performance between the active and the inactive groups with threshold b values of 10, 20, and 30 s/mm² (AUC: 0.877, 0.882, and 0.881, respectively, all P < 0.017). Using the optimized threshold b value of 30 s/mm², f showed the best performance to separate the active from the inactive and the control groups with AUC of 0.613 and 0.738 (both P < 0.017) among all threshold b values.

Conclusion

D_slow and f exhibited increased diagnostic performance using the optimized threshold b value of 30 s/mm² compared with 10 and 20 s/mm², whereas D_fast did not.

Task-driven assessment of experimental designs in diffusion MRI: A computational framework

This paper proposes a task-driven computational framework for assessing diffusion MRI experimental designs which, rather than relying on parameter-estimation metrics, directly measures quantitative task performance. Traditional computational experimental design (CED) methods may be ill-suited to experimental tasks, such as clinical classification, where outcome does not depend on parameter-estimation accuracy or precision alone. Current assessment metrics evaluate experiments' ability to faithfully recover microstructural parameters rather than their task performance. The method we propose addresses this shortcoming. For a given MRI experimental design (protocol, parameter-estimation method, model, etc.), experiments are simulated start-to-finish and task performance is computed from receiver operating characteristic (ROC) curves and associated summary metrics (e.g. area under the curve (AUC)). Two experiments were performed: first, a validation of the pipeline's task performance predictions against clinical results, comparing in-silico predictions to real-world ROC/AUC; and second, a demonstration of the pipeline's advantages over traditional CED approaches, using two simulated clinical classification tasks. Comparison with clinical datasets validates our method's predictions of (a) the qualitative form of ROC curves, (b) the relative task performance of different experimental designs, and (c) the absolute performance (AUC) of each experimental design. Furthermore, we show that our method outperforms traditional task-agnostic assessment methods, enabling improved, more useful experimental design. Our pipeline produces accurate, quantitative predictions of real-world task performance. Compared to current approaches, such task-driven assessment is more likely to identify experimental designs that perform well in practice. Our method is not limited to diffusion MRI; the pipeline generalises to any task-based quantitative MRI application, and provides the foundation for developing future task-driven end-to end CED frameworks.

Repeatability and reproducibility of MRI apparent diffusion coefficient applied on four different regions of interest for patients with axial spondyloarthritis and healthy volunteers scanned twice within a week

Objectives:

The apparent diffusion coefficient (ADC) may be used as a biomarker for diagnosis and/or monitoring treatment response in patients with axial spondyloarthritis (axSpA), but this requires reliable ADC measurements. This study assessed test–retest repeatability and reproducibility of ADC measurements using four different region of interest (ROI) settings.

Methods:

In this prospective study, the sacroiliac joints (SIJs) of 25 patients with axSpA and 24 age- and sex-matched healthy volunteers were imaged twice at a mean interval of 6.8 days in a 1.5 T scanner using, multishot echoplanar diffusion-weighted sequences. ADCs at four ROI settings were assessed: 5 mm and 10 mm anatomic band-shaped, 15 mm linear, and 40 mm² circular.

Results:

Intraclass correlation coefficient (ICC) assessments showed that the interstudy repeatability was good for median ADC (ADC_med) and 95th-percentile ADC (ADC₉₅) measurements in patients with axSpA (0.77–0.83 and 0.75–0.83, respectively), but poor-to-moderate in healthy subjects (0.27–0.55 and 0.13–0.37, respectively). For all ROI settings, intrareader reproducibility was excellent for ADC_med-measurements (ICC:0.85–0.99) and moderate-to-excellent for ADC₉₅ measurements (ICC:0.68–0.96). The 5 mm ROI had the least estimated bias and highest level of agreement on Bland–Altman plots. The interreader reproducibility was moderate (ICC:0.71). The 15 mm linear ROI produced significantly greater ADC_med and ADC₉₅ measurements than all other ROI settings (p < 0.01–0.02), except for the circular ROI ADC₉₅ measurements.

Conclusion:

ROI settings influence ADC measurements. Interstudy repeatability of SIJ ADC measurements is independent of ROI settings. However, the 5 mm ROI showed the least bias and random error and seems preferable.

Advances in knowledge:

ADC measurements are affected by ROI settings, and this should be taken into account when assessing ADC maps.

An information-based comparison of diffusion attenuation models in normal and inflamed bone marrow

Diffusion-weighted imaging has received attention as a method for characterizing inflammatory exudates in bone marrow in immune-mediated inflammatory diseases and reveals an increase in diffusivity in regions of bone marrow oedema. Various models of diffusion attenuation have been investigated but the model providing the best description of tissue pathophysiology in regions of marrow oedema is unknown. Determining the most appropriate model is an important step towards protocol optimization and the development of a robust and clinically useful method. We aimed to determine which of three candidate models of diffusion attenuation most accurately describes the acquired signal from normal and inflamed bone marrow. 11 subjects with spondyloarthritis and evidence of active inflammation (ie bone marrow oedema) on MRI and 17 patients with no evidence of active inflammation underwent diffusion-weighted imaging of the sacroiliac joints (b-values 0, 50, 100, 300 and 600 s/mm² ). Monoexponential, intravoxel incoherent motion (IVIM) and kurtosis models were fitted to the acquired signal from regions of interest in areas of bone marrow oedema and normal marrow. The three models were compared in terms of sum of squared error and information content (corrected Akaike information criterion). Model parameters were compared between regions of bone marrow oedema and regions of normal marrow. f the three models investigated, the IVIM model provided the best description of the signal over the 0-600 s/mm² range across normal and inflamed bone marrow. There was a particular advantage of the IVIM model in normal marrow, where it was best able to capture the pronounced fast diffusion component observed in several cases. However, IVIM and kurtosis effects both became smaller and the signal behaviour became closer to monoexponential in the presence of bone marrow oedema. Our data suggest that increases in D_tissue (in the IVIM framework) might account for the reduced deviation from monoexponential behaviour in oedematous bone.

Quantitative Imaging in Inflammatory Arthritis: Between Tradition and Innovation

Radiologic imaging is crucial for diagnosing and monitoring rheumatic inflammatory diseases. Particularly the emerging approach of precision medicine has increased the interest in quantitative imaging. Extensive research has shown that ultrasound allows a quantification of direct signs such as bone erosions and synovial thickness. Dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography (CT) contribute to the quantitative assessment of secondary signs such as osteoporosis or lean mass loss. Magnetic resonance imaging (MRI), using different techniques and sequences, permits in-depth evaluations. For instance, the perfusion of the inflamed synovium can be quantified by dynamic contrast-enhanced imaging or diffusion-weighted imaging, and cartilage injury can be assessed by mapping (T1ρ, T2). Furthermore, the increased metabolic activity characterizing the inflammatory response can be reliably assessed by hybrid imaging (positron emission tomography [PET]/CT, PET/MRI). Finally, advances in intelligent systems are pushing forward quantitative imaging. Complex mathematical algorithms of lesions' segmentation and advanced pattern recognition are showing promising results.

Three tesla and 3D multiparametric combined imaging evaluation of axial spondyloarthritis and pelvic enthesopathy

PURPOSE

Axial spondyloarthritis (SpA) is a group of diseases with temporally disseminated symptoms and clinical signs, which render the diagnosis challenging. Laboratory and MRI findings are used in addition for confirming the diagnosis and evaluation of disease activity. The purpose of this study was to evaluate clinically suspected axial SpA to determine the technical success of a multiparametric and 3D rheumatology lumbosacral MR imaging (MRLI) protocol and to assess the disease distribution, inter-reader reliability, and impact on patient management.

METHODS

A consecutive series of patients with clinical suspicion of axial SpA were included. Two rheumatologists recorded the clinical findings and disease activity on a confidence scale before and after MRLI. Two musculoskeletal (MSK) radiologists read the imaging data including enthesitis, arthritis, osseous lesions, ADC values, and enhancement. Prevalence-adjusted and bias-adjusted kappa (PABAK), ICC and Fisher exact test were calculated.

RESULTS

There were 41 patients including 31 females and 10 males with ages of 41 ± 10 and 41 ± 12 (mean ± SD), respectively. The spine T2W imaging received the highest quality scores followed by whole abdomen-pelvis 3D-T2W imaging, 3D-CEMR (contrast-enhanced MRI), and DWI. On spine imaging, acute and chronic lesions of lumbar spine and sacroiliac joints were seen in 4/41, 18/41 and 6/41, and 27/41 of the patients, respectively. Several additional enthesopathy lesions were seen on the whole abdomen-pelvis 3D sequence. ADC value of bone lesions was different 0.95 ± 0.23 (mean ± SD) than normal bone (0.20 ± 0.1). PABAK for acute and chronic findings ranged 0.70-1.0 and 0.41-0.51, respectively. Imaging changed the diagnosis in 17 of 41 patients. No association was noted with respect to treatment change (p = 1) or clinical response (p = 0.2).

CONCLUSION

Multiparametric lumbosacral MR imaging is a technically successful modality to identify multiple spinal and additional extraspinal sites of involvement in SpA, which are helpful in establishing the diagnosis of axial SpA. Larger patient population study is warranted to evaluate further impact on the treatment efficacy.

Test-retest repeatability of the apparent diffusion coefficient in sacroiliac joint MRI in patients with axial spondyloarthritis and healthy individuals

Background

The apparent diffusion coefficient (ADC) may be used as a biomarker to diagnose axial spondyloarthritis (axSpA) and monitor therapeutic response.

Purpose

To measure the repeatability of the ADC in healthy individuals and in patients with axSpA with and without active sacroiliitis in a test–retest set-up, and to correlate ADC to conventional magnetic resonance imaging (MRI) bone marrow edema (BME) scores and clinical findings.

Material and Methods

A total of 25 patients with axSpA and 24 sex- and age-matched healthy individuals were prospectively examined with MRI twice within 10 days. Short tau inversion recovery (STIR), T1-weighted and diffusion-weighted imaging sequences were performed. Mono-exponential ADC maps were based on four b-values: 0; 50; 500; and 800. Inter-study repeatability and intra-reader reproducibility were investigated in subgroups, as were associations with conventional MRI and clinical findings.

Results

The inter-study repeatability for the median ADC was moderate for all individuals (intraclass correlation coefficient [ICC] 0.66); it was good in patients with axSpA (ICC 0.79) and poor in healthy individuals (ICC 0.27). Significant differences in ADC were found between women and men (P = 0.03), and between patients with versus without BME on STIR (P = 0.01). ADC was associated with an MRI BME score and with age in women.

Conclusion

ADC seems to be a repeatable parameter in patients with axSpA but not in healthy individuals. ADC is correlated with MRI sacroiliac joint BME score and with age in women.

Emerging quantitative MR imaging biomarkers in inflammatory arthritides

PURPOSE

To review quantitative magnetic resonance imaging (qMRI) methods for imaging inflammation in connective tissues and the skeleton in inflammatory arthritis. This review is designed for a broad audience including radiologists, imaging technologists, rheumatologists and other healthcare professionals.

METHODS

We discuss the use of qMRI for imaging skeletal inflammation from both technical and clinical perspectives. We consider how qMRI can be targeted to specific aspects of the pathological process in synovium, cartilage, bone, tendons and entheses. Evidence for the various techniques from studies of both adults and children with inflammatory arthritis is reviewed and critically appraised.

RESULTS

qMRI has the potential to objectively identify, characterize and quantify inflammation of the connective tissues and skeleton in both adult and pediatric patients. Measurements of tissue properties derived using qMRI methods can serve as imaging biomarkers, which are potentially more reproducible and informative than conventional MRI methods. Several qMRI methods are nearing transition into clinical practice and may inform diagnosis and treatment decisions, with the potential to improve patient outcomes.

CONCLUSIONS

qMRI enables specific assessment of inflammation in synovium, cartilage, bone, tendons and entheses, and can facilitate a more consistent, personalized approach to diagnosis, characterisation and monitoring of disease.

Intravoxel incoherent motion MR imaging for differentiating malignant lesions in spine: A pilot study

PURPOSE

To determine the diagnostic potential of Intravoxel Incoherent Motion (IVIM) MRI for differentiating malignant spinal tumours from acute vertebral compression fractures and tuberculous spondylitis, and to compare IVIM with diffusion-weighted imaging (DWI) and chemical shift imaging (CSI).

METHODS

The Institutional Review Board approved this prospective study, and informed consent was obtained. IVIM MRI, DWI, and CSI at 1.5 T were performed in 25 patients with 12 acute compression fractures, 14 tuberculous spondylitis, and 18 malignant spinal tumours. The parameters of these techniques were assessed using the Kruskal-Wallis test. The diagnostic performance of the parameters was evaluated using receiver operating characteristic (ROC) analysis.

RESULTS

ADC, SIR, D_slow, D_fast, and f values of malignant tumours were significantly different from those of acute compression fracture (for all, p < 0.05). The mean D_slow and D_fast values of malignant spinal tumours had significant differences compared with those of tuberculous spondylitis (for all, p < 0.05). However, no significant differences were observed in any quantitative parameters between the acute compression fracture and the tuberculous spondylitis (p > 0.05). D_slow•f showed the highest AUC value of 0.980 (95%CI: 0.942-1.000) in differentiating acute compression fracture and malignant spinal tumours. D_slow showed the highest AUC value of 0.877 (95%CI: 0.713-0.966) in differentiating tuberculous spondylitis and malignant spinal tumours.

CONCLUSIONS

IVIM MR imaging may be helpful for differentiating malignant spinal tumours from acute vertebral compression fractures and tuberculous spondylitis.

Whole-lesion ADC histogram analysis and the spondyloarthritis research consortium of canada (SPARCC) MRI index in evaluating the disease activity of ankylosing spondylitis

BACKGROUND

Conventional MRI is limited in quantitative evaluation of ankylosing spondylitis (AS) activity states. A comparison of the effectiveness of the whole-lesion apparent diffusion coefficient (ADC) histogram analysis with the Spondyloarthritis Research Consortium of Canada (SPARCC) MRI index in evaluating the disease activity of AS might aid in this assessment.

PURPOSE

To compare the effectiveness of the whole-lesion ADC histogram analysis with the SPARCC MRI index in evaluating the disease activity states of AS.

STUDY TYPE

Prospective.

POPULATION

A total of 57 AS patients and 27 healthy matched volunteers were included.

FIELD STRENGTH/SEQUENCE

3.0T MR including a diffusion-weighted imaging (DWI) sequence (b = 0, 1000 s/mm² ).

STATISTICAL TESTS

One-way analysis of variance (ANOVA) and Scheffe's post-hoc was used to compare the parameters among different groups. A receiver operating characteristic (ROC) analysis and the Spearman rank correlation were performed to test the diagnostic performance of all parameters in distinguishing different disease activity states and determining the correlations between them.

ASSESSMENT

AS disease activity states was evaluated according to the Ankylosing Spondylitis Disease Activity Score (ASDAS). Initial DWI images and corresponding ADC maps were imported into our in-house software. Regions of interest (ROIs) were drawn in all slices and the relevant parameters were derived simultaneously. The SPARCC MRI index scores were counted artificially based on T₂ -PDW-SPAIR images.

RESULTS

The ADC_mean , ADC percentiles, and SPARCC MRI index of the active group were significantly higher than the inactive and control groups (all P < 0.001). The 90th percentile could differentiate the inactive from the control group and the low disease activity group from the inactive group (P = 0.011 and 0.006, respectively). The 50th percentile of the high disease activity group was significantly higher than the low group (P = 0.004), while the SPARCC MRI index of the very high disease activity group was higher than the high group (P < 0.001).

DATA CONCLUSION

The whole-volume ADC histogram analysis was superior to the SPARCC MRI index in assessing AS activity states.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:114-126.

Increased diffusion and decreased perfusion in epiphyses of femoral heads detected via intravoxel incoherent motion after closed reduction in children with developmental dysplasia of the hip

Background Patients with developmental dysplasia of the hip (DDH) may have decreased blood supply to the femoral heads. Finding a non-invasive method to evaluate whether the femoral heads in patients with DDH are ischemic is paramount for orthopedic surgeons. Purpose To identify whether parameters reflecting perfusion and diffusion in intravoxel incoherent motion (IVIM) sequences can be used to assess ischemia in femoral heads in patients with DDH after closed reduction. Material and Methods Twenty-eight patients with DDH who had undergone closed reduction were enrolled. IVIM data were acquired using a 3-T magnetic resonance scanner, regions of interest were placed on the epiphyses; ADC_slow, ADC_fast, f, and ADC_fast×f were measured. A Mann-Whitney U test was performed to compare ADC_slow, ADC_fast, f, and ADC_fast×f between the lesion and control sides. Receiver operating characteristic curves were generated with respective cut-off values. The lesion sides were classified based on the International Hip Dysplasia Institute (IHDI) classification. ADC_slow, ADC_fast, f, and ADC_fast×f were compared among the groups. Results ADC_slow was higher and ADC_fast, f, and ADC_fast×f were lower on the lesion sides ( P = 0.000-0.002). The optimal cut-off value for ADC_fast×f, ADC_fast, ADC_slow, and f were 0.030, 0.626, 0.000251, and 0.636, respectively. Higher IHDI classification scores on the lesion side were associated with lower ADC_fast, f, and ADC_fast×f, and higher ADC_slow values. Conclusion IVIM is a promising method to investigate the perfusion and diffusion of epiphyses of femoral heads.

Comparison of bi-exponential and mono-exponential models of diffusion-weighted imaging for detecting active sacroiliitis in ankylosing spondylitis

Background There has been a growing need for a sensitive and effective imaging method for the differentiation of the activity of ankylosing spondylitis (AS). Purpose To compare the performances of intravoxel incoherent motion (IVIM)-derived parameters and the apparent diffusion coefficient (ADC) for distinguishing AS-activity. Material and Methods One hundred patients with AS were divided into active (n = 51) and non-active groups (n = 49) and 21 healthy volunteers were included as control. The ADC, diffusion coefficient ( D), pseudodiffusion coefficient ( D*), and perfusion fraction ( f) were calculated for all groups. Kruskal-Wallis tests and receiver operator characteristic (ROC) curve analysis were performed for all parameters. Results There was good reproducibility of ADC /D and relatively poor reproducibility of D*/f. ADC, D, and f were significantly higher in the active group than in the non-active and control groups (all P < 0.0001, respectively). D* was slightly but significant lower in the active group than in the non-active and control group ( P = 0.0064, 0.0215). There was no significant difference in any parameter between the non-active group and the control group (all P > 0.050). In the ROC analysis, ADC had the largest AUC for distinguishing between the active group and the non-active group (0.988) and between the active and control groups (0.990). Multivariate logistic regression analysis models showed no diagnostic improvement. Conclusion ADC provided better diagnostic performance than IVIM-derived parameters in differentiating AS activity. Therefore, a straightforward and effective mono-exponential model of diffusion-weighted imaging may be sufficient for differentiating AS activity in the clinic.

Diffusion-weighted Imaging Is a Sensitive and Specific Magnetic Resonance Sequence in the Diagnosis of Ankylosing Spondylitis

OBJECTIVE

We tested the discriminatory capacity of diffusion-weighted magnetic resonance imaging (DWI) and its potential as an objective measure of treatment response to tumor necrosis factor inhibition in ankylosing spondylitis (AS).

METHODS

Three cohorts were studied prospectively: (1) 18 AS patients with Bath Ankylosing Spondylitis Disease Activity Index > 4, and erythrocyte sedimentation rate > 25 and/or C-reactive protein > 10 meeting the modified New York criteria for AS; (2) 20 cases of nonradiographic axial spondyloarthritis (nr-axSpA) as defined by the Assessment of Spondyloarthritis international Society (ASAS) criteria; and (3) 20 non-AS patients with chronic low back pain, aged between 18 and 45 years, who did not meet the imaging arm of the ASAS criteria for axSpA. Group 1 patients were studied prior to and following adalimumab treatment. Patients were assessed by DWI and conventional magnetic resonance imaging (MRI), and standard nonimaging measures.

RESULTS

At baseline, in contrast to standard nonimaging measures, DWI apparent diffusion coefficient (ADC) values showed good discriminatory performance [area under the curve (AUC) > 80% for Group 1 or 2 compared with Group 3]. DWI ADC values were significantly lower posttreatment (0.45 ± 0.433 before, 0.154 ± 0.23 after, p = 0.0017), but had modest discriminating capacity comparing pre- and posttreatment measures (AUC = 68%). This performance was similar to the manual Spondyloarthritis Research Consortium of Canada (SPARCC) scoring system.

CONCLUSION

DWI is informative for diagnosis of AS and nr-axSpA, and has moderate utility in assessment of disease activity or treatment response, with performance similar to that of the SPARCC MRI score.

Assessment of Correlation between Intravoxel Incoherent Motion Diffusion Weighted MR Imaging and Dynamic Contrast-Enhanced MR Imaging of Sacroiliitis with Ankylosing Spondylitis

The relationships between IVIM and DCE-MRI parameters in AS are not clear. We explore the correlation between intravoxel incoherent motion (IVIM) diffusion weighted imaging (DWI) and dynamic contrast-enhanced (DCE) parameters obtained on MR images in patients with ankylosing spondylitis (AS). Forty-four patients with AS were prospectively examined using a 1.5-T MR system. IVIM DWI was performed with 11 b values (range, 0–800 s/mm²) for all patients. The correlation coefficients between IVIM and DCE-MRI parameters were analyzed using Spearman's method. Our results showed that intra- and interobserver reproducibility were excellent to relatively good (ICC = 0.804–0.981; narrow width of 95% limits of agreement). Moderate positive correlations were observed between pure molecular diffusion (Ds) and maximum enhancement (ME) and relative enhancement (RE) (r  =  0.700, P < 0.001; r = 0.607, P < 0.001, resp.). Perfusion-related diffusion (Df) showed negative moderate correlation with ME (r  =  −0.608, P < 0.001). However, no correlation was observed between perfusion fraction (f) and any parameters of ME, RE, TTP, and BE (r = −0.093–0.213; P > 0.165). In conclusion, the IVIM parameters, especially f, might play a critical role in detecting the progression of AS, because it can provide more perfusion information compared with DCE-MRI; besides the IVIM MRI is a noninvasive method.

Quantification of fat infiltration in the sacroiliac joints with ankylosing spondylitis using IDEAL sequence

AIM

To quantitatively assess fat infiltration in the sacroiliac joints (SIJs) of patients with ankylosing spondylitis (AS) by measuring the fat/water signal ratios of periarticular bone marrow with iterative decomposition of water and fat with echo asymmetry and least square estimation (IDEAL).

MATERIALS AND METHODS

Routine SIJ magnetic resonance imaging (MRI) and IDEAL were performed on 40 patients with AS and 30 healthy subjects. The fat infiltration regions (FIRs) and normal-appearing regions (NARs) of patients were measured based on the fat/water signal intensity on IDEAL.

RESULTS

AS patients had higher fat/water signal ratios on FIRs and NARs (65.4-85.4%, p<0.05, and 44.1-70.7%, p<0.05, respectively) compared to healthy controls (38.3-43.3%). After treatment, the fat/water signal ratios of FIRs and NARs decreased (42.1-53.7% and 41.5-50.3%, respectively), but they remained higher than in the healthy controls (p<0.05). The fat infiltration was detected more effectively with a fat fraction map of the IDEAL sequence (95%) than other sequences, including the T1-weighted sequence (65%), and the fat/water signal ratios of the sacrum and ilium between the left and right sides of SIJs were approximately the same.

CONCLUSION

The findings of this study suggest that IDEAL may be useful as a quantitative and objective method for evaluating the fat infiltration in the periarticular bone marrow of SIJs with AS; additionally, the sensitivity of IDEAL is better than that of routine sequences in detecting micro-fat infiltration of SIJs, and IDEAL can be used to quantitatively measure the adipose content and monitor patient follow-up after AS treatment.

Intravoxel incoherent motion MRI as a means to measure in vivo perfusion: A review of the evidence

The idea that in vivo intravoxel incoherent motion magnetic resonance signal is influenced by blood motion in the microvasculature is exciting, because it suggests that local and quantitative perfusion information can be obtained in a simple and elegant way from a few diffusion-weighted images, without contrast injection. When the method was proposed in the late 1980s some doubts appeared as to its feasibility, and, probably because the signal to noise and image quality at the time was not sufficient, no obvious experimental evidence could be produced to alleviate them. Helped by the tremendous improvements seen in the last three decades in MR hardware, pulse design, and post-processing capabilities, an increasing number of encouraging reports on the value of intravoxel incoherent motion perfusion imaging have emerged. The aim of this article is to review the current published evidence on the feasibility of in vivo perfusion imaging with intravoxel incoherent motion MRI.

Readout-segmented multi-shot diffusion-weighted MRI of the knee joint in patients with juvenile idiopathic arthritis

BACKGROUND

Diffusion-weighted MRI has been proposed as a new technique for imaging synovitis without intravenous contrast application. We investigated diagnostic utility of multi-shot readout-segmented diffusion-weighted MRI (multi-shot DWI) for synovial imaging of the knee joint in patients with juvenile idiopathic arthritis (JIA).

METHODS

Thirty-two consecutive patients with confirmed or suspected JIA (21 girls, median age 13 years) underwent routine 1.5 T MRI with contrast-enhanced T1w imaging (contrast-enhanced MRI) and with multi-shot DWI (RESOLVE, b-values 0-50 and 800 s/mm²). Contrast-enhanced MRI, representing the diagnostic standard, and diffusion-weighted images at b = 800 s/mm² were separately rated by three independent blinded readers at different levels of expertise for the presence and the degree of synovitis on a modified 5-item Likert scale along with the level of subjective diagnostic confidence.

RESULTS

Fourteen (44%) patients had active synovitis and joint effusion, nine (28%) patients showed mild synovial enhancement not qualifying for arthritis and another nine (28%) patients had no synovial signal alterations on contrast-enhanced imaging. Ratings by the 1st reader on contrast-enhanced MRI and on DWI showed substantial agreement (κ = 0.74). Inter-observer-agreement was high for diagnosing, or ruling out, active arthritis of the knee joint on contrast-enhanced MRI and on DWI, showing full agreement between 1st and 2nd reader and disagreement in one case (3%) between 1st and 3rd reader. In contrast, ratings in cases of absent vs. little synovial inflammation were markedly inconsistent on DWI. Diagnostic confidence was lower on DWI, compared to contrast-enhanced imaging.

CONCLUSION

Multi-shot DWI of the knee joint is feasible in routine imaging and reliably diagnoses, or rules out, active arthritis of the knee joint in paediatric patients without the need of gadolinium-based i.v. contrast injection. Possibly due to "T2w shine-through" artifacts, DWI does not reliably differentiate non-inflamed joints from knee joints with mild synovial irritation.

Clinical applications of advanced magnetic resonance imaging techniques for arthritis evaluation

Magnetic resonance imaging (MRI) has allowed a comprehensive evaluation of articular disease, increasing the detection of early cartilage involvement, bone erosions, and edema in soft tissue and bone marrow compared to other imaging techniques. In the era of functional imaging, new advanced MRI sequences are being successfully applied for articular evaluation in cases of inflammatory, infectious, and degenerative arthropathies. Diffusion weighted imaging, new fat suppression techniques such as DIXON, dynamic contrast enhanced-MRI, and specific T2 mapping cartilage sequences allow a better understanding of the physiopathological processes that underlie these different arthropathies. They provide valuable quantitative information that aids in their differentiation and can be used as potential biomarkers of articular disease course and treatment response.

Intravoxel incoherent motion magnetic resonance imaging of the knee joint in children with juvenile idiopathic arthritis

BACKGROUND

MRI of synovitis relies on use of a gadolinium-based contrast agent. Diffusion-weighted MRI (DWI) visualises thickened synovium but is of limited use in the presence of joint effusion.

OBJECTIVE

To investigate the feasibility and diagnostic accuracy of diffusion-weighted MRI with intravoxel incoherent motion (IVIM) for diagnosing synovitis in the knee joint of children with juvenile idiopathic arthritis.

MATERIALS AND METHODS

Twelve consecutive children with confirmed or suspected juvenile idiopathic arthritis (10 girls, median age 11 years) underwent MRI with contrast-enhanced T1-weighted imaging and DWI at 1.5 T. Read-out segmented multi-shot DWI was acquired at b values of 0 s/mm², 200 s/mm², 400 s/mm² and 800 s/mm². We calculated the IVIM parameters perfusion fraction (f) and tissue diffusion coefficient (D). Diffusion-weighted images at b=800 s/mm², f parameter maps and post-contrast T1-weighted images were retrospectively assessed by two independent readers for synovitis using the Juvenile Arthritis MRI Scoring system.

RESULTS

Seven (58%) children showed synovial hypertrophy on contrast-enhanced imaging. Diagnostic ratings for synovitis on DWI and on f maps were fully consistent with contrast-enhanced imaging, the diagnostic reference. Two children had equivocal low-confidence assessments on DWI. Median f was 6.7±2.0% for synovitis, 2.1±1.2% for effusion, 5.0±1.0% for muscle and 10.6±5.7% for popliteal lymph nodes. Diagnostic confidence was higher based on f maps in three (25%) children and lower in one child (8%), as compared to DWI.

CONCLUSION

DWI with IVIM reliably visualises synovitis of the knee joint. Perfusion fraction maps differentiate thickened synovium from joint effusion and hence increase diagnostic confidence.

Intravoxel incoherent motion MRI assessment of chemoradiation-induced pelvic bone marrow changes in cervical cancer and correlation with hematological toxicity

PURPOSE

To investigate bone marrow changes after chemoradiation (CRT) using intravoxel incoherent motion magnetic resonance imaging (IVIM-MRI) and correlate imaging changes with hematological toxicity (HT) in patients with locally advanced cervical cancer.

MATERIALS AND METHODS

Thirty-nine patients with newly diagnosed cervical cancer were prospectively recruited for two sequential 3.0T IVIM-MRI studies: before treatment (MRI-1) and 3-4 weeks after standardized CRT (MRI-2). The irradiated pelvic bone marrow was outlined as the regions of interest to derive the true diffusion coefficient (D) and perfusion fraction (f) based on a biexponential model. The apparent coefficient diffusion (ADC) was derived using the monoexponential model. Changes in these parameters between MRI-1 and MRI-2 were calculated as ΔD, Δf, and ΔADC. HT was defined accordingly to NCI-CTCAE (v. 4.03) of grade 3 and above. Statistical analysis was performed using Mann-Whitney U-test.

RESULTS

The median age of patients was 54 years old (range 27-83 years old); 14 patients suffered from HT. Early bone marrow changes (3-4 weeks) of ΔD showed a significant difference between HT and non-HT groups (6.4 ± 19.7% vs. -6.4 ± 19.4%, respectively, P = 0.041). However, no significant changes were noted in Δf (3.7 ± 13.3% vs. 1.5 ± 12.5% respectively, P = 0. 592) and ΔADC (5.5 ± 26.3% vs. -3.3 ± 27.0% respectively, P = 0.303) between the HT and non-HT groups. Δf increased insignificantly for both groups.

CONCLUSION

ΔD was the only significant parameter to differentiate early cellular environment changes in bone marrow after CRT, suggestive that ΔD was more sensitive than Δf and ΔADC to reflect the underlying microenvironment injury.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1491-1498.

Assessment of active and inactive sacroiliitis in patients with ankylosing spondylitis using quantitative dynamic contrast-enhanced MRI

PURPOSE

To investigate the feasibility of using quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) to differentiate the active and inactive stage of sacroiliitis and the correlation between quantitative parameters and disease activity as measured by clinical scores.

MATERIALS AND METHODS

Forty-two patients with ankylosing spondylitis underwent DCE-MRI on a 3.0T MRI unit. According to the results of the blood sedimentation rate (ESR), C-reactive protein (CRP), and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the patients were grouped into inactive and active groups. Pharmacokinetic models were used to generate the semiquantitative and quantitative hemodynamic parameters of DCE-MRI. The between-group differences were analyzed using the Wilcoxon rank sum test, and the correlations between the pharmacokinetic parameters and BASDAI score were analyzed using Spearman's correlation coefficient. The efficacies of different parameters in differentiating the active and inactive phase of sacroiliitis were evaluated and compared using receiver operator characteristics (ROC) curve analysis.

RESULTS

K^trans , K_ep , V_e , time to peak (TTP), max concentration (MAX Conc), and area under the curve (AUC) of the active group were significantly higher than those of the inactive stage group (P < 0.05). There were significant correlations between all parameters and BASDAI (P < 0.05). AUC of the receiver operator characteristics curve (AUC_R ) of different parameters were not statistically different (P >0.05), except between AUC and MAX Conc (P = 0.0012).

CONCLUSION

Quantitative DCE-MRI parameters can differentiate between active and inactive ankylosing spondylitis. Among those, K^trans had the highest correlation coefficient with the BASDAI score.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:71-78.

Application of Diffusion-Weighted Imaging in the Detection of Active Sacroiliitis and the Comparison of Apparent Diffusion Coefficient and Relative Apparent Diffusion Coefficient Values

Objectives

This study aims to evaluate the role of diffusion-weighted imaging in detection of active sacroiliitis and compare the apparent diffusion coefficient (ADC) and normalized relative ADC (r-ADC) values by using vertebra and iliac wings as reference organs.

Patients and methods

The study included 56 patients (26 males, 30 females; mean age 37.7±10.1 years; range 18 to 66 years) with chronic back pain and without history of sacroiliitis who underwent magnetic resonance imaging. T2-weighted spectral presaturation with inversion recovery, contrast-enhanced T1-weighted spectral presaturation with inversion recovery, and diffusion-weighted (b values: 0 and 600 s/mm2) images were obtained. All images were evaluated by two different radiologists for interobserver variability. All individuals were grouped in either mechanical low back pain (control group) or active sacroilitis (disease group) groups according to the presence or absence of MRI findings of active sacroilitis. ADC values of both surfaces were measured from normal and affected areas of joints. Also, ADC values of L5 vertebra and iliac wings were measured as reference organs to calculate r-ADC values.

Results

Mean ADC and r-ADC values measured from lesions were significantly higher than that of normal appearing bone marrow areas in both patients with mechanical low back pain (n=17) and active sacroiliitis (n=39). Both ADC values and r-ADC values could differentiate active lesions from normal appearing bone marrow areas as well as contrast-enhanced T1-weighted images. According to r-ADC values calculated with the L5 vertebra, unaffected portions of bone marrow areas in patients with sacroiliitis were normalized whereas r-ADC remained higher than normal in affected portions of the bones.

Conclusion

Diffusion-weighted imaging is a fast, sensitive magnetic resonance imaging sequence in detection of active sacroiliitis. It does not require contrast agent and can be safely used as an adjunct to conventional magnetic resonance images. r-ADC is also highly sensitive in detecting active sacroiliitis and may be used as an alternative to standard ADC measurements for the demonstration of inflammation. It helps eliminate individual bone marrow differences by using patients' own normal bone marrow measurements and increases diagnostic accuracy.

Frequency of sacroiliitis among patients with low back pain

Introduction

Sacroiliitis is one of the important symptoms in patients attending infectious diseases and rheumatology clinics. Some patients with sacroiliitis are asymptomatic, and some have unspecific symptoms. The aim of this study was to determine the frequency of sacroiliitis causes among patients attending Shahid Sadoughi’s infectious disease and rheumatology clinics.

Methods

In this study, we evaluated patients attending Shahid Sadoughi rheumatology and infectious diseases clinic in 2014. Patients who had positive findings in favor of sacroiliitis were evaluated by history, physical exam, laboratory tests, and imaging. The patients were divided into infectious, inflammatory non-infectious, and degenerative causes. The data were analyzed by IBM SPSS version 20 using the independent samples t-test, ANOVA, the chi-squared test, and the Fisher’s exact test.

Results

We studied 136 patients. Among them 64 (47.1%) were male, and 72 (52.9%) were female. The mean age of the participants was 34.28 ± 10.36 years. Among the patients, 12 (8.8%) had infectious causes, 120 (88.2%) had inflammatory non-infectious causes, and four (2.9%) had degenerative causes.

Conclusion

Based on our results, inflammatory non-infectious causes are at the top of the list of sacroiliitis causes, but we should always consider infectious causes, including brucellosis.