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Biomedical subjects

E F Jackson

Publications and source records attributed to E F Jackson.

36 records · Page 2Linked to original sources
PubMed1991

Proton magnetic resonance spectroscopic studies of hypertrophied muscle. Effect of botulinum toxin treatment.

In vivo image-guided localized proton magnetic resonance spectroscopy (MRS) studies have been performed in a patient with hypertrophied tibialis anterior (TA) muscle and following two injections of botulinum toxin into the affected muscle. Prior to treatment, lipid levels in hypertrophied muscle were found to be low compared to normal. Lipid levels were observed to approach control levels after the second injection. Three months following treatment the trend in exercise-induced changes in lipids was observed to be similar between the hypertrophied and normal TA muscle. This preliminary report demonstrates the potential clinical utility of MRS in evaluating patient response to medical treatment.

Adult↗
PubMed1990

One-dimensional spectroscopic imaging with stimulated echoes: phantom and human leg studies.

One-dimensional phase encoding was incorporated in the stimulated echo single voxel localization sequence for in vivo proton spectroscopic studies. Phantom studies were performed to assess the effect of the number of phase encoding steps on the spectral contamination from the adjacent volumes. Both water suppressed and unsuppressed spectra were obtained in reasonable acquisition times from various regions in the human leg with a spatial resolution of around 1.1 cm3.

Adipose Tissue↗
PubMed1990

Histopathologic correlation of magnetic resonance imaging signal patterns in a spinal cord injury model.

Magnetic resonance imaging (MRI) provides a noninvasive method of monitoring the pathologic response to spinal cord injury. Specific MR signal intensity patterns appear to correlate with degrees of improvement in the neurologic status in spinal cord injury patients. Histologic correlation of two types of MR signal intensity patterns are confirmed in the current study using a rat animal model. Adult male Sprague-Dawley rats underwent spinal cord trauma at the midthoracic level using a weight-dropping technique. After laminectomy, 5- and 10-gm brass weights were dropped from designated heights onto a 0.1-gm impounder placed on the exposed dura. Animals allowed to regain consciousness demonstrated variable recovery of hind limb paraplegia. Magnetic resonance images were obtained from 2 hours to 1 week after injury using a 2-tesla MRI/spectrometer. Sacrifice under anesthesia was performed by perfusive fixation; spinal columns were excised en bloc, embedded, sectioned, and observed with the compound light microscope. Magnetic resonance axial images obtained during the time sequence after injury demonstrate a distinct correlation between MR signal intensity patterns and the histologic appearance of the spinal cord. Magnetic resonance imaging delineates the pathologic processes resulting from acute spinal cord injury and can be used to differentiate the type of injury and prognosis.

Animals↗
PubMed1988

In vivo localized proton spectroscopic studies of human gastrocnemius muscle.

In vivo proton magnetic resonance spectroscopy studies of gastrocnemius muscle were performed in six normal volunteers. Both spatially resolved spectroscopy (SPARS) and stimulated echo acquisition mode (STEAM) sequences were used for volume localization. A number of water suppression sequences have been combined with these localization schemes. Among the various techniques investigated in these studies, STEAM with an inversion pulse (T1-discriminated spectrum) seems to have the best potential for in vivo localized high-resolution proton spectroscopy studies of human muscle.

Adult↗
PubMedDate not supplied

Proton MR spectroscopy of gadolinium-enhanced multiple sclerosis plaques.

Magnetic resonance (MR) imaging and proton MR spectroscopy were performed in 14 patients with clinically definite multiple sclerosis (MS). Prominent resonances in the 0.5-2.0-ppm region were seen in the spectra of six of nine gadopentetate dimeglumine-enhanced plaques in seven patients. These resonances were presumed to originate in lipids and other myelin breakdown products. Similar resonances were detected in only seven of 21 unenhancing plaques. The more frequent presence of such signals in the gadolinium-enhanced regions indicates that myelin breakdown is often associated with the inflammation that occurs in early stages of MS plaque evolution. It remains uncertain, however, whether active inflammation as indicated by gadolinium enhancement is a necessary precursor of myelin breakdown as detected at MR spectroscopy. Quantitative spectral analysis did not indicate statistically significant differences in N-acetyl aspartate and choline levels relative to creatine plus phosphocreatine between healthy volunteers and MS patients.

Adult↗
PubMedDate not supplied

Short TE hydrogen-1 spectroscopic MR imaging of normal human brain: reproducibility studies.

Studies have been performed to evaluate the reproducibility of longitudinal acquisitions with short TE spectroscopic magnetic resonance (MR) imaging of human brain. In healthy volunteers, the ratios of N-acetyl-aspartate (NAA) and choline (Cho) with respect to total creatine (Cr) (creatine and phosphocreatine) have been examined in terms of voxel-to-voxel, acquisition-to-acquisition, and subject-to-subject variation. Overall coefficients of variation for NAA/Cr ratios and Cho/Cr ratios were 18% and 16%, respectively. The interacquisition variation was not statistically significant (P = .05) for either ratio. In terms of F ratios, the dominant source of variation in the NAA/Cr ratio was intersubject variability, whereas for the Cho/Cr ratio the dominant source of variation was intervoxel variability. Consequences of spectroscopic processing with spatial apodization and postacquisition water suppression and resolution enhancement were also examined. Such reproducibility studies are crucial if longitudinal spectroscopic evaluations are to be performed in a clinical setting to follow the natural course of disease states or the effects of therapy.

Adult↗
PubMedDate not supplied

Reproducibility of nonparametric feature map segmentation for determination of normal human intracranial volumes with MR imaging data.

Semiautomated segmentation of dual-contrast magnetic resonance images was used to determine volumes of total brain, gray matter, white matter, and cerebrospinal fluid (CSF) in healthy volunteers. Reproducibility of the technique was evaluated in terms of intraobserver, interobserver, and study-to-study variations. Intraobserver coefficients of variation ranged from 0.4% to 6.0%, while interobserver values ranged from 0.8% to 9.9%. In both cases, the maximum variations were obtained in volume measurements of tissues with maximum complexity (ie, CSF), and the minimum variation was obtained in determining total brain volume. This was also true in the case of study-to-study variations in volume measurements, for which the coefficients of variation ranged from 0.5% to 8.7%. The use of appropriate preprocessing techniques, which are crucial to the accuracy and reproducibility of the segmentation technique, are described in detail.

Adult↗
PubMedDate not supplied

Unsuppressed fat in the right anterior diaphragmatic region on fat-suppressed T2-weighted fast spin-echo MR images.

The authors retrospectively evaluated magnetic resonance images of the abdomen obtained in 52 consecutive patients. All cases included fast spin-echo (FSE) T2-weighted images acquired with a frequency-selective fat saturation technique. All imaging was performed with a 1.5-T unit. In 42 patients (81%), fat was not suppressed in the right anterior diaphragmatic region on the T2-weighted FSE images with fat suppression. In 11 (26%) of these 42 patients, subcutaneous fat adjacent to the unsuppressed anterior diaphragmatic fat was well suppressed. Hence, the fat in the diaphragmatic region mimicked fluid or peritoneal implants. The cause of the artifact appears to be the juxtaposition of liver, fat, and lung parenchymal air within a small anatomic space, creating a localized inhomogeneity of the magnetic field and susceptibility effects. Radiologists should be aware of this phenomenon to prevent confusion of an artifact with fluid or neoplasms.

Abdomen↗
PubMedDate not supplied

Dynamic imaging of intracranial lesions using fast spin-echo imaging: differentiation of brain tumors and treatment effects.

The purpose of this study was to develop a technique for differentiating between recurrent brain tumors and treatment-related changes, such as radiation necrosis, using dynamic MRI. Ninety-five patients with intracranial mass lesions were evaluated using T1-weighted fast spin-echo (FSE) MRI at 1.5 T. Pathologies included treatment-related changes (n = 32), primary tumors (n = 41), metastatic tumors (n = 5), meningiomas (n = 4), and mixed primary/treatment related changes (n = 13). Signal enhancement-time curves were analyzed by fitting to a sigmoidal-exponential function. Maximal enhancement rates were calculated as the first derivative of the fitted curve. Based on the maximal enhancement rates, treatment-related changes could be differentiated from primary tumors, metastatic tumors, and meningiomas at the P < .05 confidence level. Lesions of mixed tumor and treatment-related change had intermediate values. Dynamic MRI can be used to differentiate treatment-related changes from primary tumors in previously treated patient populations based on maximal enhancement rates. Individual case studies demonstrate the clinical significance of these findings.

Adolescent↗
PubMedDate not supplied

In vivo 1H spectroscopic studies of human gastrocnemius muscle at 1.5 T.

In vivo high resolution 1H magnetic resonance spectra are observed from the gastrocnemius muscle in 12 normal volunteers. The gross spectral features do not appear to significantly change from individual to individual. However, the number and the relative amplitudes of the resonances from the fatty acid chains are found to exhibit significant variation from normal to normal. The spectra observed on different occasions in the same individual exhibit very little variation. Our studies indicate that it is preferable to use the spin echo sequence with a long echo time to observe water-suppressed proton spectra from the muscle tissue.

Adult↗
PubMedDate not supplied

In vivo muscle magnetic resonance spectroscopy in a family with mitochondrial cytopathy: a defect in fat metabolism.

In vivo proton and phosphorus magnetic resonance spectroscopy (MRS) studies were performed at 1.5 T on two patients (siblings) diagnosed as having a mitochondrial cytopathy. The clinical diagnosis was based on a complete battery of biochemical tests, electron microscopy and modified Gomori trichrome stain studies of muscle. Proton spectra from the gastrocnemius muscle were recorded using the stimulated echo acquisition mode (STEAM) and the phosphorus spectra were obtained using the depth-resolved surface coil spectroscopy (DRESS) sequence. Proton resonances from neutral fats in the patients were found to be strikingly weak compared to normals. The ratios [PCr]/[ATP] and [PCr]/[Pi] and the pH values, as inferred from the phosphorus MRS, were found to be marginally decreased compared to normals. These studies indicate defective fatty acid metabolism in these two patients. It is, however, not known whether the abnormal mitochondrial ultrastructure represents a primary abnormality or secondary to defective fatty acid metabolism.

Adult↗
PubMedDate not supplied

Accuracy and reproducibility in volumetric analysis of multiple sclerosis lesions.

The accuracy and reproducibility of dual-contrast segmentation based on nonparametric feature map analysis have been investigated in a multicomponent gelatin phantom. The root mean square errors in volume ranged from 0.02 cm3 for small volumes to 3.8 cm3 for larger volumes, with a mean error of 0.97 cm3. Average inter- and intraobserver coefficients of variation were found to be < 7% for all compartments. To evaluate the reproducibility of segmentation of clinical image data, volumes of total brain, CSF, and multiple sclerosis (MS) lesions were obtained from five image sets of MS patients. Inter- and intraobserver coefficients of variations were computed for the patient data and were found to be < 5% for brain, 17% for CSF, and 20% for MS lesions. Such variations were found to be reduced by appropriate preprocessing of the images.

Adult↗