Improving portable low-field MRI image quality through image-to-image translation using paired low- and high-field images.

Low-field portable magnetic resonance imaging (MRI) scanners are more accessible, cost-effective, sustainable with lower carbon emissions than superconducting high-field MRI scanners. However, the images produced have relatively poor image quality, lower signal-to-noise ratio, and limited spatial resolution. This study develops and investigates an image-to-image translation deep learning model, LoHiResGAN, to enhance the quality of low-field (64mT) MRI scans and generate synthetic high-field (3T) MRI scans. We employed a paired dataset comprising T1- and T2-weighted MRI sequences from the 64mT and 3T and compared the performance of the LoHiResGAN model with other state-of-the-art models, including GANs, CycleGAN, U-Net, and cGAN. Our proposed method demonstrates superior performance in terms of image quality metrics, such as normalized root-mean-squared error, structural similarity index measure, peak signal-to-noise ratio, and perception-based image quality evaluator. Additionally, we evaluated the accuracy of brain morphometry measurements for 33 brain regions across the original 3T, 64mT, and synthetic 3T images. The results indicate that the synthetic 3T images created using our proposed LoHiResGAN model significantly improve the image quality of low-field MRI data compared to other methods (GANs, CycleGAN, U-Net, cGAN) and provide more consistent brain morphometry measurements across various brain regions in reference to 3T. Synthetic images generated by our method demonstrated high quality both quantitatively and qualitatively. However, additional research, involving diverse datasets and clinical validation, is necessary to fully understand its applicability for clinical diagnostics, especially in settings where high-field MRI scanners are less accessible.

Clinical Tests of Tibialis Posterior Tendinopathy: Are They Reliable, and How Well Are They Reflected in Structural Changes on Imaging?

OBJECTIVE: To determine the reliability of common clinical tests for tibialis posterior tendinopathy (TPT) and to investigate their relationship with grayscale ultrasound findings in individuals who have medial foot/ankle pain. DESIGN: Prospective cohort. METHODS: Fifty-two individuals reporting medial foot/ankle pain were clinically examined by 2 physical therapists using 4 clinical tests for TPT: pain on tendon palpation, swelling around the tendon, pain/weakness with tibialis posterior contraction, and pain during or inability to perform a single-leg heel raise (SLHR). Individuals also underwent an ultrasound examination by a sonographer. Physical therapists and the sonographer were blind to each other's findings. Positive ultrasound examination included at least 1 of the following grayscale changes: hypoechogenicity, fibrillar disruption, or thickening of the tendon. For reliability between the 2 physical therapists, we calculated kappa coefficients and 95% confidence intervals (CIs). To assess relationships between clinical and imaging findings, we calculated odds ratios and 95% CIs. RESULTS: The SLHR was the most reliable test, with substantial agreement between physical therapists (κ = 0.74; 95% CI: 0.54, 0.93), while the other tests had moderate levels of reliability. Of all clinical tests, the SLHR was most related to grayscale findings on ultrasound (odds ratio = 5.8), but was imprecisely so, with a 95% CI of 1.7 to 20.4. CONCLUSION: Of all tests, the SLHR was the most reliable between clinicians and best related to imaging findings in individuals presenting with TPT, aligning with contemporary thinking of tendinopathy as a load-related clinical presentation. There was a disconnect between clinical findings and ultrasound grayscale changes in the tibialis posterior tendon in individuals with TPT. J Orthop Sports Phys Ther 2021;51(5):253-260. Epub 28 Mar 2021. doi:10.2519/jospt.2021.9707.

Magnetic Resonance Spectroscopy Assessment of Brain Metabolite Concentrations in Individuals With Chronic Whiplash-associated Disorder: A Cross-sectional Study.

OBJECTIVES: Pathophysiologic mechanisms underpinning ongoing pain in whiplash-associated disorder (WAD) are not well understood, however, alterations in brain morphology and function have been observed in this population and in other chronic pain conditions. This study investigated metabolite profiles of brain regions in people with chronic WAD compared with controls. MATERIALS AND METHODS: Thirty-eight individuals with chronic WAD (mean [SD] age, 39.5 [11.3] years, 23 female individuals) and 16 pain-free controls (38.9 [12.7] years, 11 female individuals) underwent multivoxel brain magnetic resonance spectroscopy. At the anterior cingulate cortex (ACC), primary motor cortex (1MC), and somatosensory cortex (SSC), ratios of metabolite concentrations were calculated for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (Ins), and glutamate/glutamine (Glx). Chronic WAD group participants completed clinical questionnaires and cold and pressure pain threshold assessment. Data were analyzed with hypothesis testing and Spearman correlations (P≥0.05), with Benjamini-Hochberg corrections (5% false discovery rate). RESULTS: No group differences were observed for NAA:Cr, NAA:Cho, Cr:Cho, Glx:NAA, Glx:Cr, Glx:Cho, Ins:NAA, Ins:Cr, Ins:Cho or Ins:Glx for left or right ACC, 1MC, or SSC following correction for multiple comparisons. No significant correlations were observed between metabolite ratios and any clinical variable. DISCUSSION: These results suggest that ongoing pain and disability in this population may not be underpinned by metabolite aberrations in the brain regions examined. Further research is required to progress our understanding of cortical contributions to neurophysiologic mechanisms in chronic WAD.

Spinal cord injury is not a feature of chronic whiplash-associated disorder: a magnetic resonance spectroscopy study.

PURPOSE: Injury to the cervical spinal cord has been suggested as a mechanism that may underpin chronic whiplash-associated disorder (WAD). This study aimed to assess metabolite concentrations indicative of neuronal injury or pathology in the cervical cord in people with chronic WAD. METHODS: Forty-one people with chronic WAD (mean [SD] age 39.6 [11.0] years, 25 females) and 14 healthy controls (39.2 [12.6] years, 9 females) underwent cervical spinal cord magnetic resonance spectroscopy to measure the metabolites N-acetylaspartate (NAA), creatine (Cr) and choline (Cho). Participants with WAD completed clinical questionnaires on pain intensity (Visual Analogue Scale), disability (Neck Disability Index) and psychological factors (Pain Catastrophising Scale, Post-traumatic Diagnostic Scale), and underwent cervical range of motion assessment and pain threshold testing to cold and pressure stimuli. Data were analysed using hypothesis testing and Spearman correlations (p < 0.05). RESULTS: There were no differences between the WAD and control groups for NAA/Cr (median [IQR] WAD 1.73 [1.38, 1.97], controls 2.09 [1.28, 2.89], p = 0.37), NAA/Cho (WAD 1.50 [1.18, 2.01], controls 1.57 [1.26, 1.93], p = 0.91) or Cr/Cho (WAD 0.84 [0.64, 1.17], controls 0.76 [0.60, 0.91], p = 0.33). There were no significant correlations between NAA/Cr, NAA/Cho or Cr/Cho and any clinical variable (p ≥ 0.06). CONCLUSIONS: Findings are consistent with major metabolic changes not being present in chronic WAD.

Changes in internal carotid and vertebral arterial wall stiffness with head movement can be detected with shear wave elastography.

Background: Safe practice is important for patients with neck pain, with the potential for injury to cervical arteries. Cervical manipulation or end range techniques/positions may place considerable strain on the arteries. Altered integrity of the arterial wall may render them more susceptible to minor trauma, particularly in the upper cervical region. Screening of blood flow velocity is limited for predicting those at risk. Examining properties of the cervical arterial wall (stiffness characteristics) and their response to head movement may provide an alternate measure of arterial susceptibility.Objectives: To investigate whether shear wave ultrasound elastography can detect any changes in internal carotid (ICA) and vertebral (VA) arterial wall stiffness in neutral compared with contralateral head rotation.Design: Observational studyMethods: Shear wave ultrasound elastography was used to measure the stiffness of the ICA and VA. Shear wave velocity (m/s), indicative of arterial stiffness, was measured in both arteries proximally (C3-4) and distally (C1-2) in neutral and contralateral head rotation as were intimal thickness (mm) and flow velocity (cm/s).Results: Thirty participants (20-62 years) were successfully imaged. The VA was stiffer than ICA and it became significantly stiffer in contralateral rotation (p = 0.05). The ICA became significantly less stiff (p = 0.01). Effects were more apparent at C1-2 but significant in the ICA only (p = 0.03). Flow velocity and intimal thickness were unchanged in rotation.Conclusions: Changes in VA and ICA arterial wall stiffness can be measured with shear wave ultrasound elastography. This measure may ultimately help identify arteries with greater vulnerability to rotational stresses.

Shear wave elastography of the cervical arteries: A novel approach to the assessment of cervical arterial wall stiffness. An investigation of psychometric properties and intra-rater reliability.

BACKGROUND: Cervical arterial dissection, can occur spontaneously and is a rare but catastrophic adverse event associated with neck manipulation. Pathophysiology involves altered integrity of the arterial wall increasing its vulnerability to minor trauma. Those at risk are difficult to detect. Previous screening investigated blood flow but altered mechanical properties as stiffness of cervical arterial wall could provide a more valid indication of arterial integrity or even early dissection. OBJECTIVES: To investigate suitability and intra-rater reliability of shear wave ultrasound elastography to measure mechanical properties of the cervical arterial wall. Suitability was assessed by ability to track arteries along their length and measurement accuracy. DESIGN: Observational and intra-rater reliability study. METHODS: Internal carotid (ICA) and vertebral arteries (VA) of healthy participants were examined with shear wave elastography. Shear wave velocity (m/s) indicative of wall stiffness was measured with the head in the neutral position: proximally (C3-4) and distally (C1-2) where injuries have been more commonly reported. Proximal measures were repeated to assess intra-rater reliability. RESULTS: Thirty healthy participants (13 female), mean age of 29 (±12.8) years were imaged. Mean VA wall stiffness (3.4 m/s) was greater than ICA (2.3 m/s) (p < 0.000). Intra-rater reliability for ICA was ICC 0.81 (CI 0.52 to 0.92) and for VA ICC 0.76 (CI 0.38 to 0.9). Standard error of measurement was 0.16 for ICA and 0.34 for VA. CONCLUSIONS: Shear wave ultrasound elastography appears a suitable and reliable method to measure cervical arterial wall stiffness, justifying further research into its use for screening arterial integrity.

Intramuscular fat is present in cervical multifidus but not soleus in patients with chronic whiplash associated disorders.

The presence of intramuscular fat (IMF) in the cervical spine muscles of patients with whiplash associated disorders (WAD) has been consistently found. The mechanisms underlying IMF are not clear but preliminary evidence implicates a relationship with stress system responses. We hypothesised that if systemic stress system responses do play a role then IMF would be present in muscles remote to the cervical spine. We aimed to investigate if IMF are present in muscle tissue remote (soleus) to the cervical spine in people with chronic WAD. A secondary aim was to investigate associations between IMF and posttraumatic stress symptom levels. Forty-three people with chronic WAD (25 female) and 16 asymptomatic control participants (11 female) participated. Measures of pain, disability and posttraumatic stress symptoms were collected from the WAD participants. Both groups underwent MRI measures of IMF in cervical multifidus and the right soleus muscle. There was significantly greater IMF in cervical multifidus in patients with WAD and moderate/severe disability compared to controls (p = 0.009). There was no difference in multifidus IMF between the mild and moderate/severe disability WAD groups (p = 0.64), or the control and mild WAD groups (p = 0.21). IMF in the right soleus was not different between the groups (p = 0.47). In the WAD group, we found no correlation between PDS symptoms and cervical multifidus IMF or between PDS symptoms and soleus IMF. Global differences in IMF are not a feature of chronic WAD, with differences in IMF limited to the cervical spine musculature. While the mechanisms for the development of IMF in the cervical spine following whiplash injury remain unclear, our data indicate that local factors more likely contribute to these differences.

Magnetic resonance imaging: fundamental safety issues.

SYNOPSIS: Medical practitioners have a variety of imaging modalities at their disposal. The exquisite soft tissue delineation available with magnetic resonance imaging (MRI) has resulted in the rising utilization of this particular modality. Increasingly, physical therapists around the world are actively involved in not only referring patients with musculoskeletal conditions for MRI but also in the acquisition of MRI data in both the clinical and research arenas. The MRI process involves the use of a very strong static magnetic field, time-varying (gradient) fields, and radiofrequency energy. To ensure the well-being of patients, staff, and visitors, an understanding of the primary hazards of this environment and the rigorous safety procedures that must be followed is imperative to the clinician. This paper describes the basic components of an MRI system, discusses various MRI safety issues, and presents the screening procedure necessary prior to using MRI. Primary hazards associated with the imaging process are also reviewed. J Orthop Sports Phys Ther 2011;41(11):820-828. doi:10.2519/jospt.2011.3906.

Craniocervical orientation affects muscle activation when exercising the cervical extensors in healthy subjects.

OBJECTIVE: To evaluate the activity of neck extensor muscles during different extension exercises with muscle functional magnetic resonance imaging (mfMRI). DESIGN: Cross-sectional. SETTING: University laboratory. PARTICIPANTS: Healthy subjects (N=11; 7 men, mean age +/- SD, 34+/-5.6y; 4 women, mean age +/- SD, 23.3+/-5.2y; group mean age +/- SD, 30.1+/-7.5y). INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: mfMRI measures of T2 relaxation were made for the multifidus (Mul), the semispinalis cervicis (SCe), the semispinalis capitis (SCa), and the splenius capitis (SpC) at C2-3, C5-6, and C7-T1 in response to 2 head/neck orientations: craniocervical neutral (CCN) and craniocervical extension (CCE). Subjects performed three 1-minute repetitions of each condition at 20% maximum voluntary contraction. RESULTS: Significant shifts were observed in all muscle groups at the C5-6 and C7-T1 levels after both conditions (P=.04) except the SpC muscle at C5-6 with CCN (P=.17). T2 shifts in the SCa were significantly greater in response to CCE than CCN at C2-3 (P=.03) and C5-6 (P=.02). Similarly, CCE resulted in larger shifts than CCN in the Mul/SCe at C7-T1 (P=.003). No segmental differences were observed between exercises for SpC (P=.25). CONCLUSIONS: The results of this study provide some preliminary insight into the impact of craniocervical orientation on the differential response of the deep and superficial cervical extensor muscles during the performance of cervical extensor exercises.

The association between degenerative hip joint pathology and size of the gluteus medius, gluteus minimus and piriformis muscles.

This study aimed to investigate changes in the deep abductor muscles, gluteus medius (GMED), piriformis (PIRI), and gluteus minimus (GMIN), occurring in association with differing stages of unilateral degenerative hip joint pathology (mild: n=6, and advanced: n=6). Muscle volume assessed via magnetic resonance imaging was compared for each muscle between sides, and between groups (mild, advanced, control (n=12)). GMED and PIRI muscle volume was smaller around the affected hip in subjects with advanced pathology (p<0.01, p<0.05) while no significant asymmetry was present in the mild and control groups. GMIN showed a trend towards asymmetry in the advanced group (p=0.1) and the control group (p=0.076) which appears to have been associated with leg dominance. Between group differences revealed a significant difference for the GMED muscle reflecting larger muscle volumes on the affected side in subjects with mild pathology, compared to matched control hips. This information suggests that while GMED appears to atrophy in subjects with advanced hip joint pathology, it may be predisposed to hypertrophy in early stages of pathology. Assessment and exercise prescription methods should consider that the response of muscles of the abductor synergy to joint pathology is not homogenous between muscles or across stages of pathology.

Dorsal digital septum of the distal interphalangeal joint.

PURPOSE: Clinical observation has led to the discovery of a distinct anatomic septum from the extensor tendon to the skin at the distal phalanx that appears to limit the proximal spread of infection from the dorsum of the distal phalanx. This study employed histology and high-resolution magnetic resonance imaging (MRI) to identify this anatomic structure at the level of the distal interphalangeal (DIP) joint. METHODS: We used high-resolution (16.4-T) MRI to image and section 10 cadaveric fingers (9 female, 1 male) from both left and right hands. Once imaged, we made histologic sections using hematoxylin and eosin, or Van Gieson's stain, and examined them microscopically for concordant findings. RESULTS: In all 10 scans, the proposed septum was visualized using MRI with histologic confirmation. It was observed to extend from the skin creases overlying the dorsal aspect of the DIP joint to the extensor tendon. It is composed of collagen bundles arranged in a variable network that adhere extensor tendon to skin at the DIP joint. CONCLUSIONS: Clinical observations proposed the existence of a distinct septum between extensor tendon and skin at the level of the DIP joint. We confirmed this structure to be a collagen septum by MRI and histology. This previously undescribed structure is called the dorsal septum.

The association between degenerative hip joint pathology and size of the gluteus maximus and tensor fascia lata muscles.

The aim of this study was to obtain, using Magnetic Resonance Imaging (MRI), muscle volume measurements for the gluteus maximus (upper: UGM and lower: LGM portions) and tensor fascia lata (TFL) muscles in both healthy subjects (n=12) and those with unilateral osteoarthritis (OA) of the hip (mild: n=6, and advanced: n=6). While control group subjects were symmetrical between sides for the muscles measured, subjects with hip joint pathology showed asymmetry in GM muscle volume dependent on stage of pathology. The LGM demonstrated atrophy around the affected hip in subjects with advanced pathology (p<0.05), however asymmetry of the UGM (p<0.01) could be attributed largely to hypertrophy on the unaffected side, based on between group comparisons of muscle volume. TFL showed no significant asymmetry, or difference compared to the normal control group. This study highlights the functional separation of UGM and LGM, and the similarities of the UGM and TFL, both superficial abductors appearing to maintain their size around the affected hip. Further research is required to determine the specific changes occurring in the deeper abductor muscles. This information may assist in the development of more targeted and effective exercise programmes in the management of OA of the hip.

Altered white matter diffusion anisotropy in normal and preterm infants at term-equivalent age.

To investigate white matter (WM) development, voxelwise analyses of diffusion tensor MRI (DTMRI) data, acquired from 12 very preterm and 11 preterm infants with gestational ages (GA) ranging from 25 to 29 and 29 to 32 weeks, respectively, and 10 newborn normal term infants were performed. T(2) relaxation measures were also generated to assess brain water content. Compared with newborn term infants, very preterm infants were found to possess reduced fractional anisotropy (FA) within the frontal lobe, and a number of anterior and posterior commissural pathways. Preterm infants possessed reduced FA mainly within the posterior regions of the corpus callosum. Unexpectedly, we observed significantly reduced FA and increased T(2) within a number of corticospinal projections in the newborn term infants compared to the preterm groups. This finding may reflect increased water concentration and/or a lowering of FA due to the presence of crossing interhemispheric WM projections. These findings indicate that care should be taken when interpreting FA indices without knowledge of the possible effects of water concentration in the newborn infant brain.