Graham J. Galloway

Fatty Infiltration in the Cervical Extensor Muscles in Persistent Whiplash-Associated Disorders: A Magnetic Resonance Imaging Analysis

Study Design. Cross-sectional investigation of muscle changes in patients suffering from persistent whiplash-associated disorders (WAD). Objectives. To quantitatively compare the presence of fatty infiltrate in the cervical extensor musculature in a cohort of chronic whiplash patients (WAD II) and healthy control subjects across muscle and cervical segmental level. Summary of Background Data. Magnetic resonance imaging (MRI) can be regarded as the gold standard for muscle imaging; however, there is little knowledge about in vivo features of neck extensor muscles in patients suffering from persistent WAD and how fat content alters across the factors of muscle, vertebral segments, age, self-reported pain and disability, compensation status, body mass index, and duration of symptoms. Methods. A reliable MRI measure for fatty infiltrate was performed of the cervical extensor muscles bilaterally in 113 female subjects (79 WAD, 34 healthy control; 18–45 years, 3 months to 3 years post injury). The measure was performed on all subjects for the rectus capitis posterior minor and major, multifidus, semispinalis cervicis and capitis, splenius capitis, and upper trapezius. Results. The WAD subjects had significantly larger amounts of fatty infiltrate for all of the cervical extensor muscles compared with healthy control subjects (all P < 0.0001). In addition, the amount of fatty infiltrate varied by both cervical level and muscle, with the rectus capitis minor/major and multifidi at C3 having the largest amount of fatty infiltrate (P < 0.0001). Intramuscular fat was independent of age, self-reported pain/disability, compensation status, body mass index, and duration of symptoms. Conclusion. There is significantly greater fatty infiltration in the neck extensor muscles, especially in the deeper muscles in the upper cervical spine, in subjects with persistent WAD when compared with healthy controls. Future studies are required to investigate the relationships between muscular alterations and symptoms in patients suffering from persistent WAD.

Use of spherical harmonic deconvolution methods to compensate for nonlinear gradient effects on MRI images.

Spatial encoding in MR techniques is achieved by sampling the signal as a function of time in the presence of a magnetic field gradient. The gradients are assumed to generate a linear magnetic field gradient, and typical image reconstruction relies upon this approximation. However, high‐speed gradients in the current generation of MRI scanners often sacrifice linearity for improvements in speed. Such nonlinearity results in distorted images. The problem is presented in terms of first principles, and a correction method based on a gradient field spherical harmonic expansion is proposed. In our case, the amount of distortion measured within a typical field of view (FOV) required for head imaging is sufficiently large that without the use of some distortion correction technique, the images would be of limited use for stereotaxy or longitudinal studies, where precise volumetric information is required. Magn Reson Med 52:115–122, 2004.

Fatty infiltrate in the cervical extensor muscles is not a feature of chronic insidious onset neck pain

AIM To investigate the presence of fatty infiltrate in the cervical extensor musculature in patients with insidious-onset neck pain to better understand the possible pathophysiology underlying such changes in chronic whiplash-associated disorders (WAD). MATERIALS AND METHODS A sample of convenience of 23 women with persistent insidious-onset neck pain (mean age 29.2+/-6.9 years) was recruited for the study. Magnetic resonance imaging (MRI) was used to quantify fatty infiltration in the cervical extensor musculature. Quantitative Sensory Testing (QST; pressure and thermal pain thresholds) was performed as sensory features are present in chronic whiplash. Self-reported pain and disability, as well as psychological distress, were measured using the Neck Disability Index (NDI) and the General Health Questionnaire-28 (GHQ-28), respectively. RESULTS Measures were compared with those of a previous dataset of chronic whiplash patients (n=79, mean age 29.7+/-7.8 years). Using a classification tree, insidious-onset neck pain was clearly identified from whiplash (p<0.001), based on the presence of MRI fatty infiltrate in the cervical extensor musculature (0/102 individuals) and altered temperature thresholds (cold; 3/102 individuals). CONCLUSION Fatty infiltrates in the cervical extensor musculature and widespread hyperalgesia were not features of the insidious-onset neck pain group in this study; whereas these features have been identified in patients with chronic WAD. This novel finding may enable a better understanding of the underlying pathophysiological processes in patients with chronic whiplash.

Assessment of human liver metabolism by phosphorus-31 magnetic resonance spectroscopy

Phosphorus 31 magnetic resonance (MR) spectroscopy was used for the study of liver metabolism in vivo in seven healthy subjects. Subjects were examined in a 1.6 T whole-body magnet using surface coils for data acquisition. The region of the liver from which MR signals were collected was selected by magnetic-field profiling. The concentration ratios of adenosine triphosphate (ATP), inorganic phosphate (Pi) and sugar phosphates contained in liver cells could be reproducibly assessed. Cytosolic pH and the free magnesium concentration were determined to be 7.18 and 300 microM, respectively. During intravenous fructose tolerance tests the hepatic concentrations of sugar phosphates, ATP and Pi altered markedly. During the first 5 min following bolus injection of 250 mg fructose/kg body weight the concentration of sugar phosphates increased sevenfold whereas Pi and ATP decreased by three- to fourfold. Metabolism of sugar phosphates was complete within 20 min and could be followed by 31P MR with a time resolution of 5 min. Thus, 31P MR spectroscopy yields insight into liver metabolism which has not been accessible so far using conventional non-invasive methods. In conjunction with intravenous fructose loading, 31P MR spectroscopy may provide a means for the functional assessment of the liver.

4D deformation modeling of cortical disease progression in Alzheimer's dementia

This work describes the development of a model of cerebral atrophic changes associated with the progression of Alzheimers disease (AD). Linear registration, region‐of‐interest analysis, and voxel‐based morphometry methods have all been employed to elucidate the changes observed at discrete intervals during a disease process. In addition to describing the nature of the changes, modeling disease‐related changes via deformations can also provide information on temporal characteristics. In order to continuously model changes associated with AD, deformation maps from 21 patients were averaged across a novel z‐score disease progression dimension based on Mini Mental State Examination (MMSE) scores. The resulting deformation maps are presented via three metrics: local volume loss (atrophy), volume (CSF) increase, and translation (interpreted as representing collapse of cortical structures). Inspection of the maps revealed significant perturbations in the deformation fields corresponding to the entorhinal cortex (EC) and hippocampus, orbitofrontal and parietal cortex, and regions surrounding the sulci and ventricular spaces, with earlier changes predominantly lateralized to the left hemisphere. These changes are consistent with results from post‐mortem studies of AD. Magn Reson Med 46:661–666, 2001.

The temporal development of fatty infiltrates in the neck muscles following whiplash injury: An association with pain and posttraumatic stress

Background Radiological findings associated with poor recovery following whiplash injury remain elusive. Muscle fatty infiltrates (MFI) in the cervical extensors on magnetic resonance imaging (MRI) in patients with chronic pain have been observed. Their association with specific aspects of pain and psychological factors have yet to be explored longitudinally. Materials and Findings 44 subjects with whiplash injury were enrolled at 4 weeks post-injury and classified at 6 months using scores on the Neck Disability Index as recovered, mild and moderate/severe. A measure for MFI and patient self-report of pain, loss of cervical range of movement and posttraumatic stress disorder (PTSD) were collected at 4 weeks, 3 months and 6 months post-injury. The effects of time and group and the interaction of time by group on MFI were determined. We assessed the mediating effect of posttraumatic stress and cervical range of movement on the longitudinal relationship between initial pain intensity and MFI. There was no difference in MFI across all groups at enrollment. MFI values increased in the moderate/severe group and were significantly higher in comparison to the recovered and mild groups at 3 and 6 months. No differences in MFI values were found between the mild and recovered groups. Initial severity of PTSD symptoms mediated the relationship between pain intensity and MFI at 6 months. Initial ROM loss did not. Conclusions MFI in the cervical extensors occur soon following whiplash injury and suggest the possibility for the occurrence of a more severe injury with subsequent PTSD in patients with persistent symptoms.

Super-resolution track-density imaging studies of mouse brain: Comparison to histology

The recently proposed track-density imaging (TDI) technique was introduced as a means to achieve super-resolution using diffusion MRI. This technique is able to increase the spatial resolution of the reconstructed images beyond the acquired MRI resolution by incorporating information from whole-brain fibre-tracking results. It not only achieves super-resolution, but also provides very high anatomical contrast with a new MRI contrast mechanism. However, the anatomical information-content of this novel contrast mechanism has not yet been assessed. In this work, we perform such a study using diffusion MRI of ex vivo mouse brains acquired at 16.4 T, to compare the results of the super-resolution TDI technique with histological staining (myelin and Nissl stains) in the same brains. Furthermore, a modified version of the directionally-encoded colour TDI map using short-tracks is introduced, which reduces the TDI intensity dynamic range, and therefore enhances the directionality colour-contrast. Good agreement was observed between structures visualised in the super-resolution TDI maps and in the histological sections, supporting the anatomical information-content of the images generated using the TDI technique. The results therefore show that the TDI methodology does provide meaningful and rich anatomical contrast, in addition to achieving super-resolution. Furthermore, this study is the first to show the application of TDI to mouse brain imaging: the high-resolution, high-quality images demonstrate the useful complementary information that can be achieved using super-resolution TDI.

A mitochondrial encephalomyopathy. A combined 31P magnetic resonance and biochemical investigation.

A 15-year-old girl presented with recurrent encephalopathic episodes, epilepsy, myopathy and chronic lactic acidosis. A muscle biopsy revealed the presence of ragged red fibres and mitochondria with paracrystalline inclusions. Biochemical studies on freshly isolated skeletal muscle mitochondria demonstrated a deficiency of NADH-CoQ reductase activity. Investigation of her gastrocnemius muscle at rest by phosphorus nuclear magnetic resonance displayed a reduced phosphocreatine concentration with elevated levels of inorganic phosphate and ADP. Abnormalities were also apparent in her brain spectrum. It is therefore possible that the mitochondrial defect present in skeletal muscle is also being expressed in the brain.

Study of human liver disease with P-31 magnetic resonance spectroscopy.

Liver metabolism and energetics of 24 patients with liver disease were studied using phosphorus-31 magnetic resonance spectroscopy. Significant abnormalities were detected in the majority of these patients. A striking diversity in metabolic patterns was observed. Patients with acute viral hepatitis had low liver phosphodiesters and high phosphomonoesters, possibly phosphocholine and phosphoethanolamine. In alcoholic hepatitis phosphomonoesters were raised. Intracellular inorganic phosphate and inorganic phosphate/ATP ratios were decreased in primary biliary cirrhosis and in some patients with hepatitis. These spectroscopic results were evaluated in respect of the pattern of liver damage and cellular regeneration. Liver tumours had raised phosphomonoesters and also showed evidence for altered spin-lattice relaxation of the phosphorus nucleus in various metabolites. In iron overload the liver ATP resonances were broadened. The line broadening correlated with the degree of iron overload suggesting the potential use of P-31 magnetic resonance spectroscopy for measuring liver iron.

Water signal elimination in vivo, using suppression by mistimed echo and repetitive gradient episodes

A number of techniques (I) are available for the elimination of an unwanted signal (usually the ‘H signal from water) from a spectrum. Unless the unwanted signal is removed before the preamplifier and ADC are encountered in the signal detection pathway, difficulties are experienced in the observation of very weak signals because of dynamic range problems. O f the available techniques the most efficient appears to be the 1331 method developed by Hore (I, 2); however, as Hore points out, this technique is only of limited value if the water resonance is broad. This is the situation often encountered in vivo where very broad water signals are observed, the broadness usually being the result of magnetic field inhomogeneity. In general, for signal elimination the most successful methods have in the past relied on overall nonexcitation of the unwanted resonance, the aim being to leave the unwanted spin coherence along the z axis and away from the detection plane. The alternative procedure would be to destroy selectively the unwanted spin coherence and it is this strategy which has led to the application of reverse polarization transfer methods (3) as probably the most efficient water signal elimination method yet devised. In this paper we develop a method for selectively destroying the water signal, applicable to in vivo NMR studies where broad water signals are often encountered. We call the technique SUBMERGE. The method eliminates transverse water spin coherence over a wide but controllable frequency band. The significant point is that the water spin coherence is destroyed, thus eliminating the signal from the preamplifier and ADC, allowing the efficient detection of weak signals. As a test, we attempt to observe the methyl signal from lactic acid at a concentration of 10 mM in neat HzO. The water signal is thus about 3700 times more intense than the signal of interest. A 250 ml round-bottom flask was used as the sample container. A water signal having a half-height width of 10 Hz was typically detected in a single pulse experiment. In Fig. 1 is shown the experimentally determined excitation profile from a 10 ms 7r/2 sine pulse. The excitation profile from a 10 ms 7r/2 gaussian pulse is also shown for comparison. At a ‘H resonance frequency of 100 MHz (field strength 2.4 T) the chemical-shift separation between the two resonances of interest is about 345 Hz. Thus, by use of such shaped pulses, it is possible to excite the water signal but not the