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Biomedical subjects

B C Bowen

Publications and source records attributed to B C Bowen.

At least 19 recordsLinked to original sources
PubMed2006

Quantitative analysis of the effects of physiologic brain motion on point-resolved spectroscopy.

BACKGROUND AND PURPOSE: Although single-voxel proton MR spectroscopy is a noninvasive method that enables measurement of brain metabolite concentrations, it has been shown that physiologic brain motion causes inaccuracies in measurement of metabolite concentrations and increases the overall SD of the measurements when the stimulated echo acquisition mode (STEAM) is used. We tested the hypothesis that the point-resolved spectroscopy (PRESS) technique is less sensitive to physiologic brain motion than the STEAM technique. METHODS: In 10 healthy subjects, spectra were obtained from a voxel located in the left basal ganglia by using the PRESS sequence with cardiac gating and without water suppression to assess global phase change as a function of physiologic brain motion. This was accomplished by acquiring data at various time delays from the R wave throughout the cardiac cycle. Subsequently, spectra were obtained in 10 healthy subjects by using PRESS both without and with cardiac gating, and with water suppression, to determine whether brain motion resulted in a statistically significant difference in mean and SD of measured metabolite concentration. RESULTS: At various time delays from the R wave throughout the cardiac cycle, no significant global phase difference was noted in water signal intensity. In addition, when PRESS data were obtained both without and with cardiac gating (by using an optimal delay obtained from previously published data by using STEAM), no significant difference was seen in measured metabolite concentrations and SDs. CONCLUSION: The PRESS technique is relatively insensitive to physiologic brain motion.

Adult↗
PubMed2000

MR imaging and localized proton spectroscopy of the precentral gyrus in amyotrophic lateral sclerosis.

BACKGROUND AND PURPOSE: In the search for a diagnostic test for amyotrophic lateral sclerosis (ALS), especially upper motor neuron (UMN) involvement, MR imaging and proton spectroscopy techniques have each received attention, but their findings have not been correlated. The purpose of this study was to identify relationships among the results of current techniques, taking into account the severity of clinical UMN disease, so that objective measures of the pathogenesis of ALS may be established. METHODS: Eighteen subjects with clinically diagnosed ALS and 12 healthy volunteers underwent MR imaging of the brain and localized proton MR spectroscopy. Water-suppressed spectra from the left precentral gyrus and from the left cuneus gyrus were analyzed with the LCModel method, yielding concentrations for N-acetyl (NA), total creatine (Cr), choline (Cho), glutamate (Glu), glutamine (Gin), and myo-inositol (Ins) metabolic substrates. Signal intensities of the precentral gyrus on T2-weighted images were assessed qualitatively in a blinded fashion. RESULTS: For the precentral gyrus, mean Cho (1.3 mM) and Ins (3.25 mM) for the ALS group were significantly increased. After adjustment for Cr covariance, mean Glu (5.08 mM) and NA (6.31 mM) were decreased. For the cuneus gyrus, no difference in metabolite concentrations between groups was observed. Trend analysis of the precentral gyrus metabolite concentrations revealed significant increases in Cho and Ins and decreases in NA and Glu with respect to the severity of clinical UMN signs. Metabolic changes were greater in the subset of ALS patients with precentral gyrus signal changes on imaging, and significantly increased Ins was associated with cortical hypointensity on fast spin-echo images. CONCLUSION: Mean metabolite concentrations determined from precentral gyrus spectra reflect clinical and pathologic changes that occur in ALS. Imaging findings, while related to the spectral and clinical results, are not specific to ALS.

Adult↗
PubMed2000

Contrast-enhanced MR angiography of spinal vessels.

Compared to routine spin-echo images, contrast-enhanced MR angiography provides improved characterization of the spinal vasculature. This technique can help narrow the differential diagnosis and guide further treatment in patients with radiculopathy or myelophathy. The most useful application to date has been in screening for spinal dural fistulae. The fast, three-dimensional method offers the possibility of distinguishing the largest spinal arteries and veins, although additional technical improvements and clinical experience are needed to accomplish this goal.

Arteriovenous Malformations↗
PubMed1999

1H-magnetic resonance spectroscopy in amyotrophic lateral sclerosis.

1H-magnetic resonance spectroscopy (MRS) is potentially a powerful tool for the investigation of the chemicals of the brain in vivo in health and disease. Levels of N-acetyl-aspartate (NAA) in the motor cortex and brainstem of patients with amyotrophic lateral sclerosis (ALS) have been reported to be reduced by up to 68%, and in one report the level of glutamate in the brainstem was increased by 58%. We studied levels of metabolites in the cerebral cortex and brainstem of 20 ALS patients and 14 age-matched controls with a 1.5 Tesla Picker magnet using MRS. We used the same spectra for determining both the area of the metabolite peaks expressed as a ratio of the area of the creatine (Cr) peak, and the absolute concentrations using the Provencher LC model. These produced different results. With the LC model, the NAA content of the motor cortex of ALS patients was reduced by 7.7% (P=0.015), and that of the brainstem was reduced by 21.5% (P=0.035), compared with controls. The degree of reduction of NAA was related to the severity of upper motor neuron abnormalities. No effect of treatment with anti-glutamate agents on NAA concentration could be detected. Concentrations of other metabolites were not affected in ALS. It appears that MRS is a technique that is still in development, and that further refinement is required before it can be used to understand disease mechanisms and investigate treatment in ALS.

Adult↗
PubMed1999

Vascular anatomy and disorders of the lumbar spine and spinal cord.

The design and interpretation of MR imaging studies of patients with suspected spinal vascular disease are based on a knowledge of arterial and venous anatomy. This article describes the major intradural vessels and their appearance on spin-echo MR images and gadolinium-enhanced MR angiography. Current gadolinium-enhanced MR techniques primarily detect veins, which may be increased in apparent number, size, or tortuosity in the pathological conditions discussed. These characteristics of abnormal veins have yet to be quantified, and differentiation between normal and abnormal is sometimes difficult. Familiarity with the appearance of normal veins on MR angiography facilitates recognition of abnormal vessels and thus the formulation of a more accurate differential diagnosis in the patient with a conus or cauda equina lesion. In the future, gadolinium-enhanced 3D MR angiography may achieve adequate spatial and temporal resolution to differentiate spinal arteries from spinal veins. This differentiation could further simplify the diagnosis of vascular lesions, depending or the complexity of the vascular pattern observed. Also, the combination of MR angiography and diffusion imaging of the cord may finally provide the information needed for characterization by MR imaging of clinically suspected arterial infarction.

Arteries↗
PubMed1998

Diagnostic and surgical management of spinal dural arteriovenous fistulas.

OBJECTIVE: A retrospective review was conducted to compare magnetic resonance (MR) and conventional spinal angiographic images and to investigate the outcome of our treatment protocol for patients with spinal dural arteriovenous fistulas (DAVFs). MATERIALS AND METHODS: Nine patients with a diagnosis of DAVF based on clinical myelopathy and preoperative MR imaging (MRI) and MR angiography (MRA) findings were treated at our institution by the senior author (BAG). All nine patients initially presented with progressive myelopathy. Preoperative MRI revealed T2-weighted signal abnormalities in all patients, and MRA was diagnostic in all patients. Each patient underwent a laminectomy and ligation of the arterialized draining vein. Selective spinal angiograms were used to confirm the level of fistula immediately before the surgical procedure was performed and to document complete obliteration after clip ligation of the medullary draining vein. Follow-up MRI and MRA were performed approximately 2 months postoperatively. RESULTS: MRI T2-weighted signal hyperintensity improved after surgery in all nine patients. Postoperatively, progression of motor weakness and gait difficulty was halted and some improvement was observed in all patients. No patient was neurologically normal, however. To date, there has been no clinical or MRA evidence of recurrence in any patient. CONCLUSION: Preoperative MRA and intraoperative spinal x-ray angiography present as an effective combination for diagnosing and intraoperatively confirming DAVF. Both T1-weighted enhancement and T2-weighted signal hyperintensity on MR images improved after the obliteration of the DAVFs and correlated with clinical improvement in all nine patients. MRA provides adequate visualization and localization of spinal DAVFs and may serve as a useful noninvasive tool for diagnosing and following patients with spinal DAVFs in the future.

Adult↗
PubMed1998

MR angiography of the spine.

Postcontrast MR angiography complements the standard spinal MR imaging study by improving detection and display of normal and abnormal intradural vessels, primarily veins. Detection of abnormal veins facilitates diagnosis of spinal vascular malformations and vascular tumors. The most useful application has been in screening for spinal dural arteriovenous fistula, in which MR angiography demonstrates the medullary vein into which the fistula drains, thus allowing noninvasive identification of the spinal level of the fistula.

Arteriovenous Fistula↗
PubMed1997

Spine MR angiography.

The use of MR angiography to evaluate spinal vessels is in an early stage of development. Both time-of-flight (3D) and phase-contrast (2D and 3D) techniques have been applied, and for both types of techniques, the vessels are best visualized following intravenous gadolinium administration. The vessels of interest are the millimeter-sized intradural arteries and veins, which are located on the cord surface and travel from the cord to the epidural space. Only the post gadolinium 3D TOF technique has been shown to display normal intradural vessels (thoracolumbar region), principally veins. Both TOF and PC techniques provide better delineation of enlarged intradural vessels associated with spinal vascular malformations than standard MR imaging alone. PC techniques are much less sensitive in detecting the arterial supply to dural arteriovenous fistula than intramedullary arteriovenous malformation. The TOF technique can predict the foraminal level of a dural fistula when an enlarged medullary vein, resulting from retrograde drainage, is present. MR angiography, in conjunction with MR imaging, is now suggested for screening of suspected spinal vascular malformation. Other applications such as vascular tumors and arterial or venous occlusive disease are under investigation.

Humans↗
PubMed1996

Lyme neuroborreliosis masquerading as a brainstem tumor in a 15-year-old.

A 15-year-old boy had onset of unilateral facial weakness. A few days later, he experienced mild vertigo, double vision, and headache. Examination confirmed a peripheral right seventh nerve weakness in addition to an internuclear ophthalmoplegia. The neurologic features suggested a pontine glioma. A T2-weighted MRI scan revealed demyelinating lesions in the pons and in several areas of the cerebrum, including the periventricular region. Subsequent history revealed that he had been diagnosed with Lyme arthritis 7 years earlier while living in Connecticut. The radiographic studies favored a diagnosis of multiple sclerosis. However, studies of blood and cerebrospinal fluid established a diagnosis of Lyme neuroborreliosis.

Adolescent↗
PubMed1996

MR angiography of normal intradural vessels of the thoracolumbar spine.

PURPOSE: To identify and describe the normal intradural vessels detected on MR angiograms of the thoracolumbar spine. METHODS: Six adult subjects who had clinical evidence of myelopathy, yet normal findings at spinal digital subtraction angiography (DSA), were also studied without and with contrast-enhanced MR imaging and three-dimensional time-of-flight, single-slab MR angiography. Sagittal and coronal subvolume (targeted) maximum intensity projection images were compared with arterial and venous phase DSA images. Angiographic images were then compared with postmortem, formalin-fixed cord specimens. RESULTS: Recognizable intradural vessels were detected only on contrast-enhanced MR angiograms. These vessels corresponded to the posterior and/or anterior median (midline) veins and the great medullary veins. The median veins had variable but mild tortuosity. The medullary veins, which extended from the median veins and coronal venous plexus on the cord surface to the epidural venous plexus, were relatively straight and usually located at T-12 or L-1. The anterior spinal artery could partially contribute to the anterior midline vascular signal. CONCLUSION: The intradural vessels identified on contrast-enhanced MR angiograms are primarily veins, and these are usually the largest vessels on or near the cord surface. The limited number and minimal tortuosity of these veins may serve as a baseline for the examination of patients with clinically suspected arteriovenous malformation or fistula.

Adult↗
PubMed1995

Reversible parkinsonian syndrome complicating cysticercus midbrain encephalitis.

We describe a clinical picture similar to Parkinson's disease in a patient with midbrain encephalitis due to cysticercosis. The clinical, radiographic, and cerebrospinal fluid findings suggested an inflammatory reaction to a dying cyst that involved midbrain structures. The encephalopathy appeared to worsen temporarily after the institution of anticysticercus therapy. A discordance between worsening parkinsonian symptoms and improving pyramidal features was noted. Virtually a complete clinical recovery eventually ensued.

Adult↗
PubMed1995

Imaging of the postoperative neck with emphasis on surgical flaps and their complications.

Radiologists are playing an increasingly important role in the management of patients with head and neck cancer. Imaging is often essential in preoperative planning. It is therefore imperative for the radiologist to be familiar with the wide variety of surgical procedures used as well as the normal CT and MR imaging appearance after such procedures. In addition, familiarity with the appearance of tumor recurrence and postoperative complications is essential. This pictorial essay illustrates the appearance of the normal and abnormal postoperative neck on CT scans and MR images, with an emphasis on reconstructive flaps. Postoperative complications evident on imaging studies are depicted, as is the appearance of tumor recurrence. One lymph node classification system is briefly reviewed as a basis for discussion of neck dissection and other surgical procedures.

Aged↗
PubMed1995

MR of omental myelosynangiosis.

PURPOSE: To describe MR findings in patients who have undergone omental transposition (omental myelosynangiosis) for spinal cord revascularization. METHODS: Spin-echo MR images, without and with intravenous gadolinium, were obtained before and after surgery in three patients using a quadrature spine coil. Three-dimensional time-of-flight spinal MR angiography was also performed. RESULTS: On routine MR, the transposed omentum is an irregular, lobulated fat-equivalent mass, containing serpiginous areas of flow void, which extends through the laminectomy site to lie directly adjacent to the cord surface. MR angiography demonstrated small omental vessels, some coursing to the omentum-cord interface; however, no definite extension into the cord was detected. In all patients, there was alteration in cord size and contour after transposition, but no change in cord signal. Clinical improvement was observed in one of the three patients. The signal characteristics of the transposed omentum changed, showing less homogeneity and a gradual loss of the signal over a period of 4 months. CONCLUSIONS: MR delineates transposed omentum and associated postoperative changes in omental myelosynangiosis. MR angiography is useful as an adjunct to demonstrate the small vessels near the omentum-cord interface, but lacks sufficient resolution to demonstrate neoangiogenesis within the cord.

Adult↗
PubMed1995

Proton MR spectroscopy of the brain in 14 patients with Parkinson disease.

PURPOSE: To determine whether the proton spectra from patients with clinically diagnosed Parkinson disease differ from the spectra of age-matched healthy subjects with respect to the major cerebral metabolite resonances as well as lactate. METHODS: Fourteen patients with Parkinson disease (38 to 81 years of age) and 13 healthy control subjects (37 to 81 years of age) were studied using image-guided, single-voxel (27-cm3 volume) proton MR spectroscopy of the occipital lobe. RESULTS: The peak area ratios of N-acetyl aspartate to creatine and N-acetyl aspartate to choline for Parkinson patients did not show a statistically significant difference from the corresponding ratios for control subjects. There was a very significant increase in the ratio of lactate to N-acetyl aspartate for patients with Parkinson disease, with the greatest increase (threefold) manifested by the subgroup (n = 4) with dementia. The difference in N-acetyl aspartate to choline between women (n = 7) with Parkinson disease and healthy women (n = 9) approached significance. No dependence of the peak ratios on age, duration of Parkinson disease, or medication (L-dopa) regimen was found. CONCLUSION: Preliminary results indicating an increase in cerebral lactate in patients with Parkinson disease support the hypothesis that Parkinson disease is a systemic disorder characterized by an impairment of oxidative energy metabolism. The larger increases for Parkinson patients with dementia may be diagnostically useful in assessing clinical course and in differentiating Parkinson disease from other causes of dementia. Additional studies are needed, though, to quantitate lactate changes and identify potential contributions from lipid resonances better.

Adult↗
PubMed1994

A longitudinal examination of crossed aphasia.

OBJECTIVE: To longitudinally examine neuropsychological performance in an adult dextral man with crossed aphasia after cerebrovascular accident. DESIGN: Case report using longitudinal neuropsychological, neurological, and radiological examinations performed in close temporal proximity to one another. SETTING: The patient was seen on both an inpatient and an outpatient basis by members of the Department of Neurology and Radiology of the University of Miami (Fla) School of Medicine. PATIENT: Thirty-four-year-old right-handed monolingual Hispanic man without family history of left-handedness. RESULTS: Initial neuropsychological testing revealed classic Broca's dysphasia, visual neglect, and visuospatial disturbances. The visuospatial disturbance resolved within 6 months whereas expressive language remained severely impaired. There was a dissociation between praxis and language. Mood was jovial with indifference toward his neurologic and cognitive limitations. Serial magnetic resonance imaging studies unequivocally localized the lesions to the right hemisphere, involving the right frontal, anterior parietal, and subcortical white matter. CONCLUSIONS: The clinicoanatomic correlation is compatible with the view that crossed aphasia is a "mirror" representation of that seen in cases of uncrossed aphasia. The course of recovery suggests complete lateralization of language to the right hemisphere with bilateral or crossed representation of nonverbal skills.

Adult↗
PubMed1994

Late presentation of congenital muscular torticollis: use of MR imaging and CT scan in diagnosis.

A 17-year old boy presented with a 10-year history of progressive head tilt to the right. Bilateral posterolateral cervical pain was mild and he was fully functional. The right sternocleidomastoid (SCM) muscle was prominent without rotation of the head to the left. The SCM had a cord-like consistency on palpation. Magnetic resonance (MR) and computed tomography (CT) scan imaging of the neck musculature suggested fibrous tissue within the substance of the muscle. This was histopathologically confirmed when the right SCM was surgically explored and resected. Congenital muscular torticollis is usually seen in newborns, infants, and children but may also present in adolescence and young adulthood. It should be included in the differential diagnosis of cervical dystonia as one of the nondystonic causes of abnormal head posture. Combined use of MR and CT scan of neck muscles may be of help in the diagnosis.

Adolescent↗