The diagnostic value of biexponential apparent diffusion coefficients in myopathy

Imaging biomarkers in the idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are a group of acquired muscle diseases with muscle inflammation, weakness, and other extra-muscular manifestations. IIMs can significantly impact the quality of life, and management of IIMs often requires a multi-disciplinary approach. Imaging biomarkers have become an integral part of the management of IIMs. Magnetic resonance imaging (MRI), muscle ultrasound, electrical impedance myography (EIM), and positron emission tomography (PET) are the most widely used imaging technologies in IIMs. They can help make the diagnosis and assess the burden of muscle damage and treatment response. MRI is the most widely used imaging biomarker of IIMs and can assess a large volume of muscle tissue but is limited by availability and cost. Muscle ultrasound and EIM are easy to administer and can even be performed in the clinical setting, but they need further validation. These technologies may complement muscle strength testing and laboratory studies and provide an objective assessment of muscle health in IIMs. Furthermore, this is a rapidly progressing field, and new advances are going to equip care providers with a better objective assessment of IIMS and eventually improve patient management. This review discusses the current state and future direction of imaging biomarkers in IIMs.

The Diagnostic Value of MR IVIM and T2 Mapping in Differentiating Autoimmune Myositis From Muscular Dystrophy

RATIONALE AND OBJECTIVES

To confirm the feasibility and compare the accuracy of magnetic resonance imaging intravoxel incoherent motion (IVIM) and T2 mapping models for the differentiation of autoimmune myositis from muscular dystrophy.

MATERIALS AND METHODS

Fourty-two autoimmune myositis and 11 muscular dystrophy patients proven by diagnostic criteria were enrolled in the study. Conventional MR sequences, IVIM, and T2 mapping through the bilateral thighs were obtained as well as blood samples for all patients. IVIM and T2 mapping parameters as well as serum markers were compared between the autoimmune myositis and muscular dystrophy groups. Mann-Whitney U tests were performed for statistical analysis along with receiver operating characteristic curves. Spearman correlation coefficient models were constructed to analyze the correlation between IVIM and T2 mapping with serological parameters.

RESULTS

The intramuscular apparent diffusion coefficient, tissue diffusivity (D), perfusion fraction (f_p), and T2 relaxation time values were statistically significantly different between the autoimmune myositis and muscular dystrophy groups (p < 0.05). Pseudo diffusivity (D_p) values showed no statistical difference between the groups (p > 0.05). D parameter of IVIM sequences differentiated autoimmune and muscular dystrophy with a higher specificity of 75.60%. T2 values within the thighs were correlated with serum creatine kinase and lactate dehydrogenase levels (p < 0.05).

CONCLUSION

Thigh muscle IVIM and T2 mapping parameters are useful in differentiating autoimmune myositis from muscular dystrophy, particularly the IVIM parameters.

The effect of ageing on skeletal muscle as assessed by quantitative MR imaging: an association with frailty and muscle strength

Background

Skeletal muscles undergo changes with ageing which can cause sarcopenia that can result in frailty. Quantitative MRI may detect the muscle-deficit component of frailty which could help improve the understanding of ageing muscles.

Aims

To investigate whether quantitative MRI measures of T2, fat fraction (FF), diffusion tensor imaging and muscle volume can detect differences within the muscles between three age groups, and to assess how these measures compare with frailty index, gait speed and muscle power.

Methods

18 ‘young’ (18–30 years), 18 ‘middle-aged’ (31–68 years) and 18 ‘older’ (> 69 years) healthy participants were recruited. Participants had an MRI of their dominant thigh. Knee extension and flexion power and handgrip strength were measured. Frailty (English Longitudinal Study of Ageing frailty index) and gait speed were measured in the older participants.

Results

Young participants had a lower muscle MRI T2, FF and mean diffusivity than middle-aged and older participants; middle-aged participants had lower values than older participants. Young participants had greater muscle flexion and extension power, muscle volume and stronger hand grip than middle-aged and older participants; middle-aged participants had greater values than the older participants. Quantitative MRI measurements correlated with frailty index, gait speed, grip strength and muscle power.

Discussion

Quantitative MRI and strength measurements can detect muscle differences due to ageing. Older participants had raised T2, FF and mean diffusivity and lower muscle volume, grip strength and muscle power.

Conclusions

Quantitative MRI measurements correlate with frailty and muscle function and could be used for identifying differences across age groups within muscle.

Associations between apparent diffusion coefficient values and histopathological tissue alterations in myopathies

OBJECTIVES

Diffusion-weighted imaging (DWI) can reflect histopathologic changes in muscle disorders. The present study sought to elucidate possible associations between histopathology derived from muscle biopsies and DWI in myositis and other myopathies.

METHODS

Nineteen patients (10 women, 52.6%) with a mean age 51.43 ± 19 years were included in this retrospective study. Apparent diffusion coefficients (ADC) were evaluated with a histogram approach of the biopsied muscle. The histopathology analysis included the scoring systems proposed by Tateyama et al., Fanin et al., Allenbach et al. and immunhistochemical stainings for MHC, CD68, CD8, and CD4.

RESULTS

There was a tendency that skewness was lowered with increasing Tateyama score, but it did not reach statistical significance (p = .14). No statistical differences for the other scores were identified. There was a tendency that kurtosis was higher in MHC negative stained patient compared to positive patients, but statistically significance was not reached (p = .07). ADC histogram parameters did not correlate with CD68 and CD8 positive stained cells. There was a trend for skewness to correlate with the amount of CD4-positive cells (r = .57, p = .07).

CONCLUSION

The present study could not identify statistical significant associations between DWI and histopathology in muscle diseases based upon a small patient sample. Presumably, the investigated histopathology scores are more specific for certain disease aspects, whereas ADC values reflect the whole cellularity of the investigated muscle, which might cause the negative results.

Quantitative MRI in myositis patients: comparison with healthy volunteers and radiological visual assessment

AIM

To assess whether magnetic resonance imaging (MRI)-based measurements of T2, fat fraction, diffusion tensor imaging, and muscle volume can detect differences between the muscles of myositis patients and healthy controls, and to identify how they compare with semi-quantitative MRI diagnosis.

MATERIALS AND METHODS

Sixteen myositis patients and 16 age- and gender-matched healthy controls underwent MRI of their thigh. Quantitative MRI measurements and radiologists' semi-quantitative scores were assessed. Strength was assessed using an isokinetic dynamometer.

RESULTS

Fat fraction and T2 values were higher in myositis patients whereas muscle volume was lower compared to healthy controls. There was no difference in diffusion. Muscle strength was lower in myositis patients compared to healthy controls. In a subgroup of eight patients, scored as unaffected by radiologists, T2 values were still significantly higher in myositis patients.

CONCLUSIONS

Quantitative MRI measurements can detect differences between myositis patients and healthy controls. Changes in the muscles of myositis patients, undetected by visual, semi-quantitative scoring, can be detected using quantitative T2 measurements. This suggests that MRI T2 values may be useful for the management of myositis patients.

Advancements in magnetic resonance imaging-based biomarkers for muscular dystrophy

Recent years have seen steady progress in the identification of genetic muscle diseases as well as efforts to develop treatment for these diseases. Consequently, sensitive and objective new methods are required to identify and monitor muscle pathology. Magnetic resonance imaging offers multiple potential biomarkers of disease severity in the muscular dystrophies. This Review uses a pathology-based approach to examine the ways in which MRI and spectroscopy have been used to study muscular dystrophies. Methods that have been used to quantitate intramuscular fat, edema, fiber orientation, metabolism, fibrosis, and vascular perfusion are examined, and this Review describes how MRI can help diagnose these conditions and improve upon existing muscle biomarkers by detecting small increments of disease-related change. Important challenges in the implementation of imaging biomarkers, such as standardization of protocols and validating imaging measurements with respect to clinical outcomes, are also described.

Advances in Quantitative Imaging of Genetic and Acquired Myopathies: Clinical Applications and Perspectives

In the last years, magnetic resonance imaging (MRI) has become fundamental for the diagnosis and monitoring of myopathies given its ability to show the severity and distribution of pathology, to identify specific patterns of damage distribution and to properly interpret a number of genetic variants. The advances in MR techniques and post-processing software solutions have greatly expanded the potential to assess pathological changes in muscle diseases, and more specifically of myopathies; a number of features can be studied and quantified, ranging from composition, architecture, mechanical properties, perfusion, and function, leading to what is known as quantitative MRI (qMRI). Such techniques can effectively provide a variety of information beyond what can be seen and assessed by conventional MR imaging; their development and application in clinical practice can play an important role in the diagnostic process and in assessing disease course and treatment response. In this review, we briefly discuss the current role of muscle MRI in diagnosing muscle diseases and describe in detail the potential and perspectives of the application of advanced qMRI techniques in this field.

Short- and long-term reproducibility of diffusion-weighted magnetic resonance imaging of lower extremity musculature in asymptomatic individuals and a comparison to individuals with spinal cord injury

Background

Diffusion-weighted magnetic resonance imaging (DW-MRI) of skeletal muscle has the potential to be a sensitive diagnostic and/or prognostic tool in complex, enigmatic neuromusculoskeletal conditions such as spinal cord injury and whiplash associated disorder. However, the reliability and reproducibility of clinically accessible DW-MRI parameters in skeletal muscle remains incompletely characterized – even in individuals without neuromusculoskeletal injury – and these parameters have yet to be characterized for many clinical populations. Here, we provide normative measures of the apparent diffusion coefficient (ADC) in healthy muscles of the lower limb; assess the rater-based reliability and short- and long-term reproducibility of the ADC in the same muscles; and quantify ADC of these muscles in individuals with motor incomplete spinal cord injury.

Methods

Twenty individuals without neuromusculoskeletal injury and 14 individuals with motor incomplete spinal cord injury (SCI) participated in this investigation. We acquired bilateral diffusion-weighted MRI of the lower limb musculature in all participants at 3 T using a multi-shot echo-planar imaging sequence with b-values of 0, 100, 300 and 500 s/mm² and diffusion-probing gradients applied in 3 orthogonal directions. Outcome measures included: (1) average ADC in the lateral and medial gastrocnemius, tibialis anterior, and soleus of individuals without neurological or musculoskeletal injury; (2) intra- and inter-rater reliability, as well as short and long-term reproducibility of the ADC; and (3) estimation of average muscle ADC in individuals with SCI.

Results

Intra- and inter-rater reliability of the ADC averaged 0.89 and 0.79, respectively, across muscles. Least significant change, a measure of temporal reproducibility, was 4.50 and 11.98% for short (same day) and long (9-month) inter-scan intervals, respectively. Average ADC was significantly elevated across muscles in individuals with SCI compared to individuals without neurological or musculoskeletal injury (1.655 vs. 1.615 mm²/s, respectively).

Conclusions

These findings provide a foundation for future studies that track longitudinal changes in skeletal muscle ADC of the lower extremity and/or investigate the mechanisms underlying ADC changes in cases of known or suspected pathology.

MRI assessment of the thigh musculature in dermatomyositis and healthy subjects using diffusion tensor imaging, intravoxel incoherent motion and dynamic DTI

INTRODUCTION

Dermatomyositis (DM) is an idiopathic inflammatory myopathy involving severe debilitation in need of diagnostics. We evaluated the proximal lower extremity musculature with diffusion tensor imaging (DTI), intravoxel incoherent motion (IVIM) and dynamic DTI in DM patients and controls and compared with standard clinical workup.  METHODS: In this IRB-approved, HIPAA-compliant study with written informed consent, anatomical, Dixon fat/water and diffusion imaging were collected in bilateral thigh MRI of 22 controls and 27 DM patients in a 3T scanner. Compartments were scored on T1/T2 scales. Single voxel dynamic DTI metrics in quadriceps before and after 3-min leg exercise were measured. Spearman rank correlation and mixed model analysis of variance/covariance (ANOVA/ANCOVA) were used to correlate with T1 and T2 scores and to compare patients with controls.

RESULTS

DM patients showed significantly lower pseudo-diffusion and volume in quadriceps than controls. All subjects showed significant correlation between T1 score and signal-weighted fat fraction; tissue diffusion and pseudo-diffusion varied significantly with T1 and T2 score in patients. Radial and mean diffusion exercise response in patients was significantly higher than controls.

CONCLUSION

Static and dynamic diffusion imaging metrics show correlation with conventional imaging scores, reveal spatial heterogeneity, and provide means to differentiate dermatomyositis patients from controls.

KEY POINTS

• Diffusion imaging shows regional differences between thigh muscles of dermatomyositis patients and controls. • Signal-weighted fat fraction and diffusion metrics correlate with T1/T2 scores of disease severity. • Dermatomyositis patients show significantly higher radial diffusion exercise response than controls.

Apparent diffusion coefficient (ADC) does not correlate with different serological parameters in myositis and myopathy

Background Magnetic resonance imaging (MRI) is widely used in several muscle disorders. Diffusion-weighted imaging (DWI) is an imaging modality, which can reflect microstructural tissue composition. The apparent diffusion coefficient (ADC) is used to quantify the random motion of water molecules in tissue. Purpose To investigate ADC values in patients with myositis and non-inflammatory myopathy and to analyze possible associations between ADC and laboratory parameters in these patients. Material and Methods Overall, 17 patients with several myositis entities, eight patients with non-inflammatory myopathies, and nine patients without muscle disorder as a control group were included in the study (mean age = 55.3 ± 14.3 years). The diagnosis was confirmed by histopathology in every case. DWI was obtained in a 1.5-T scanner using two b-values: 0 and 1000 s/mm². In all patients, the blood sample was acquired within three days to the MRI. The following serological parameters were estimated: C-reactive protein, lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatine kinase, and myoglobine. Results The estimated mean ADC value for the myositis group was 1.89 ± 0.37 × 10^-3mm²/s and for the non-inflammatory myopathy group was 1.79 ± 0.33 × 10^-3 mm²/s, respectively. The mean ADC values (1.15 ± 0.37 × 10^-3 mm²/s) were significantly higher to unaffected muscles (vs. myositis P = 0.0002 and vs. myopathy P = 0.0021). There were no significant correlations between serological parameters and ADC values. Conclusion Affected muscles showed statistically significantly higher ADC values than normal muscles. No linear correlations between ADC and serological parameters were identified.

Associations between apparent diffusion coefficient and electromyography parameters in myositis-A preliminary study

OBJECTIVE

MRI is widely used in several muscle disorders. Diffusion-weighted imaging (DWI) is an emergent imaging modality sensitive to microstructural alterations in tissue. The apparent diffusion coefficient (ADC) is used to quantify the random motion of water molecules. Electromyography (EMG) is a clinically used diagnostic tool in myositis. The aim of this study was to elucidate possible associations between ADC values and EMG findings in myositis patients.

METHOD

Seven patients (eight investigated muscles) with myositis (mean age 51.43 ± 19 years) were included in this study. The diagnosis was confirmed by histopathology in every case. DWI was obtained with a 1.5-T scanner using two b-values 0 and 1000 s/mm². In all patients, a needle electromyography (EMG) was performed within 3 days to the MRI. The following EMG parameters were studied: motor unit action potential (MUAP) amplitudes and durations, as well as pathological spontaneous activity. Spearman's correlation coefficient was used to analyze associations between investigated parameters.

RESULTS

The estimated mean ADC _mean value was 1.51 ± 0.29 × 10^-3 mm²/s, mean ADC _min was 1.28 ± 0.27 × 10^-3 mm²/s, and mean ADC _max was 1.73 ± 0.28 × 10^-3 mm²/s. Correlation analysis identified significant associations between ADC _mean and duration of the MUAP (p = .78 P = .0279) and between ADC _min and duration of the MUAP (p = .85, P = .01). There were no significant differences according to pathological spontaneous activity.

CONCLUSION

ADC _mean and ADC _min showed strong positive correlations with the duration of the MUAP in myositis patients. Both modalities might similarly reflect muscle fiber loss in myositis patients.

Diffusion weighted imaging demystified: the technique and potential clinical applications for soft tissue imaging

Diffusion-weighted imaging (DWI) is a fast, non-contrast technique that is readily available and easy to integrate into an existing imaging protocol. DWI with apparent diffusion coefficient (ADC) mapping offers a quantitative metric for soft tissue evaluation and provides information regarding the cellularity of a region of interest. There are several available methods of performing DWI, and artifacts and pitfalls must be considered when interpreting DWI studies. This review article will review the various techniques of DWI acquisition and utility of qualitative as well as quantitative methods of image interpretation, with emphasis on optimal methods for ADC measurement. The current clinical applications for DWI are primarily related to oncologic evaluation: For the assessment of de novo soft tissue masses, ADC mapping can serve as a useful adjunct technique to routine anatomic sequences for lesion characterization as cyst or solid and, if solid, benign or malignant. For treated soft tissue masses, the role of DWI/ADC mapping in the assessment of treatment response as well as recurrent or residual neoplasm in the setting of operative management is discussed, especially when intravenous contrast medium cannot be given. Emerging DWI applications for non-neoplastic clinical indications are also reviewed.

Histogram analysis derived from apparent diffusion coefficient (ADC) is more sensitive to reflect serological parameters in myositis than conventional ADC analysis

OBJECTIVE

Diffusion-weighted imaging (DWI) has the potential of being able to reflect histopathology architecture. A novel imaging approach, namely histogram analysis, is used to further characterize tissues on MRI. The aim of this study was to correlate histogram parameters derived from apparent diffusion coefficient (ADC) maps with serological parameters in myositis.

METHODS

16 patients with autoimmune myositis were included in this retrospective study. DWI was obtained on a 1.5 T scanner by using the b-values of 0 and 1000 s mm^-2. Histogram analysis was performed as a whole muscle measurement by using a custom-made Matlab-based application. The following ADC histogram parameters were estimated: ADCmean, ADCmax, ADCmin, ADCmedian, ADCmode, and the following percentiles ADCp10, ADCp25, ADCp75, ADCp90, as well histogram parameters kurtosis, skewness, and entropy. In all patients, the blood sample was acquired within 3 days to the MRI. The following serological parameters were estimated: alanine aminotransferase, aspartate aminotransferase, creatine kinase, lactate dehydrogenase, C-reactive protein (CRP) and myoglobin. All patients were screened for Jo1-autobodies.

RESULTS

Kurtosis correlated inversely with CRP (p = -0.55 and 0.03). Furthermore, ADCp10 and ADCp90 values tended to correlate with creatine kinase (p = -0.43, 0.11, and p = -0.42, = 0.12 respectively). In addition, ADCmean, p10, p25, median, mode, and entropy were different between Jo1-positive and Jo1-negative patients.

CONCLUSION

ADC histogram parameters are sensitive for detection of muscle alterations in myositis patients. Advances in knowledge: This study identified that kurtosis derived from ADC maps is associated with CRP in myositis patients. Furthermore, several ADC histogram parameters are statistically different between Jo1-positive and Jo1-negative patients.