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Biomedical subjects

K Maravilla

Publications and source records attributed to K Maravilla.

At least 19 recordsLinked to original sources
PubMed2001

The relative roles of intragenic polymorphisms of the vitamin d receptor gene in lumbar spine degeneration and bone density.

STUDY DESIGN: A retrospective cohort study. OBJECTIVES: To compare the magnitudes of the associations of TaqI polymorphisms of the vitamin D receptor gene with bone density and lumbar spine degeneration in the same sample. SUMMARY OF BACKGROUND DATA: Vitamin D receptor gene variations are associated with osteoporosis, osteoarthritis, and disc degeneration. Their role in these conditions remains poorly understood. METHODS: Bone density of the spine and femur were determined through DEXA, and lumbar disc degeneration was determined from magnetic resonance imaging assessments of signal intensity, disc narrowing, bulging, anular tears, herniations, and osteophytes. Associations between these measures and TaqI polymorphisms of the coding region of the Vitamin D receptor locus were examined in a population-based sample of 142 men. RESULTS: The strongest associations were with signal intensity and anular tears, which were worse for the subjects with tt genotypes than for those with TT genotypes in the L4-S1 spine discs. Conversely, the prevalences of disc bulges and osteophytes were lowest for the tt genotype. Bone density, disc height, and herniations did not differ significantly by genotype. CONCLUSIONS: The strongest association of Vitamin D receptor TaqI polymorphisms with degeneration in nonmineralized connective tissues suggests that the underlying mechanism of TaqI polymorphisms is not specific to bone. This study demonstrated for the first time that those with the tt genotype had more anular tears than those with the TT genotype, a finding that should stimulate further analyses of this gene in conditions that result in back pain. The apparent discrepancies of the associations of the tt genotype with lower signal intensity and more anular tears, but less bulges and osteophytes, could be explained if bulging and osteophytes primarily represented remodeling related to lifetime physical loading.

Adult↗
PubMed2000

Magnetic resonance imaging in patients with central nervous system pathology: a comparison of OptiMARK (Gd-DTPA-BMEA) and Magnevist (Gd-DTPA).

RATIONALE AND OBJECTIVES: The objective of the two pivotal phase 3 studies was to evaluate the safety and efficacy of OptiMARK (Gd-DTPA-bis(methoxyethylamide) [Gd-DTPA-BMEA]) compared with Magnevist (Gd-DTPA) in magnetic resonance imaging of the central nervous system. METHODS: Two multicenter, randomized, double-blind, parallel group studies were conducted in 395 patients with known or suspected central nervous system pathology. Subjects were randomized to receive a single 0.1 mmol/kg intravenous injection of either Gd-DTPA-BMEA or Gd-DTPA. The safety of Gd-DTPA-BMEA and Gd-DTPA was monitored for up to 72 hours after study drug administration. Precontrast and postcontrast administration magnetic resonance scans were acquired using identical imaging planes and techniques. RESULTS: No deaths or unexpected adverse events were reported in either group. A comparison of adverse events by intensity and relation demonstrated no statistically significant differences between the two groups. Gd-DTPA-BMEA and Gd-DTPA were equivalent with respect to confidence in diagnosis, conspicuity, and border delineation. CONCLUSIONS: Gd-DTPA-BMEA and Gd-DTPA demonstrated comparable efficacy profiles, and the safety profiles were considered similar.

Adult↗
PubMed1998

MR imaging and proton MR spectroscopy in A-to-G substitution at nucleotide position 3243 of leucine transfer RNA.

MR imaging of the brain in a 38-year-old woman with maternally inherited diabetes and deafness (MIDD) showed extensive subcortical and basal ganglia high signal intensity on T2-weighted studies though she was neurologically asymptomatic. High-signal-intensity changes were also seen in the basal ganglia on T1-weighted studies. Proton MR spectroscopy showed increased lactate, an increased choline/creatine ratio, and a decreased N-acetylaspartate/creatine ratio. Our observations suggest that patients with MIDD may have subclinical neurologic dysfunction identifiable by proton MR spectroscopy.

Adult↗
PubMed1997

Visualization-based mapping of language function in the brain.

Cortical language maps, obtained through intraoperative electrical stimulation studies, provide a rich source of information for research on language organization. Previous studies have shown interesting correlations between the distribution of essential language sites and such behavioral indicators as verbal IQ and have provided suggestive evidence for regarding human language cortex as an organization of multiple distributed systems. Noninvasive studies using ECoG, PET, and functional MR lend support to this model; however, there as yet are no studies that integrate these two forms of information. In this paper we describe a method for mapping the stimulation data onto a 3-D MRI-based neuroanatomic model of the individual patient. The mapping is done by comparing an intraoperative photograph of the exposed cortical surface with a computer-based MR visualization of the surface, interactively indicating corresponding stimulation sites, and recording 3-D MR machine coordinates of the indicated sites. Repeatability studies were performed to validate the accuracy of the mapping technique. Six observers-a neurosurgeon, a radiologist, and four computer scientists, independently mapped 218 stimulation sites from 12 patients. The mean distance of a mapping from the mean location of each site was 2.07 mm, with a standard deviation of 1.5 mm, or within 5.07 mm with 95% confidence. Since the surgical sites are accurate within approximately 1 cm, these results show that the visualization-based approach is accurate within the limits of the stimulation maps. When incorporated within the kind of information system envisioned by the Human Brain Project, this anatomically based method will not only provide a key link between noninvasive and invasive approaches to understanding language organization, but will also provide the basis for studying the relationship between language function and anatomical variability.

Brain Mapping↗
PubMed1997

Evaluation of a visualization-based approach to functional brain mapping.

We describe a method for mapping stimulation data, obtained at the time of neurosurgery for intractable epilepsy, onto a 3D MRI-based neuroanatomic model of the individual patient. The mapping is done by comparing an intraoperative photograph of the exposed cortical surface with a computer-based MR visualization of the surface, interactively indicating corresponding stimulation sites, and recording 3-D MR machine coordinates of the indicated sites. Repeatability studies were performed to validate the accuracy of the mapping technique. Six observers--a neurosurgeon, a radiologist, and four computer scientists, independently mapped 218 stimulation sites from 12 patients. The mean distance of the six locations from the mean location of each site was 2.07 mm, with a standard deviation of 1.5 mm, or within 5.07 mm with 95% confidence. Since the surgical sites are accurate within approximately 1 cm, these results show that the visualization-based approach is accurate within the limits of the stimulation maps. When incorporated within the kind of information system envisioned by the Human Brain Project, this anatomically-based method will not only provide a key link between non-invasive and invasive approaches to understanding language organization, but will also provide the basis for studying the relationship between language function and anatomical variability.

Brain Mapping↗
PubMed1996

Ulnar nerve entrapment at the elbow: correlation of magnetic resonance imaging, clinical, electrodiagnostic, and intraoperative findings.

The diagnosis of ulnar nerve entrapment at the elbow has relied primarily on clinical and electrodiagnostic findings. Recently, magnetic resonance imaging (MRI) has been used in the evaluation of peripheral nerve entrapment disorders to document signal and configuration changes in nerves. We performed a prospective study on a population of 31 elbows in 27 patients with ulnar nerve entrapment at the elbow. The study correlated MRI findings with clinical, electrodiagnostic, and operative findings. A control population consisting of 10 asymptomatic subjects also was studied by MRI. Electrodiagnostic evaluation confirmed ulnar neuropathy in 24 (77%) elbows of the 31, with localization to the elbow region in 21 (68%). MRI, using a short tau inversion recovery sequence, demonstrated increased signal of the ulnar nerve in 30 (97%) elbows of the 31 and enlargement of the ulnar nerve in 23 (74%). No MRI abnormalities were found in the control population. MRI signal increase of the ulnar nerve occurred an average of 27 mm proximal to the distal humerus and extended distally an average of 4 mm below the distal humerus. The mean total length of increased ulnar nerve signal was 34 mm. Ulnar nerve enlargement occurred an average of 19 mm proximal to the distal humerus and extended distally an average of 8 mm above the distal humerus. The mean total length of ulnar nerve enlargement was 12 mm. The 12 patients who underwent a surgical procedure for ulnar nerve entrapment were found to have ulnar nerve compression, with 9 (75%) having excellent and 3 (25%) having good postoperative results. In this study, MRI was both sensitive and specific in diagnosing ulnar nerve entrapment at the elbow as defined by clinical, electrodiagnostic, and operative findings.

Adult↗
PubMed1996

Magnetic resonance neurography of peripheral nerve lesions in the lower extremity.

OBJECTIVE: We describe the clinical application and utility of high-resolution magnetic resonance neurography (MRN) techniques to image the normal fascicular structure of peripheral nerves and its distortion by mass lesions or trauma in the lower extremity. METHODS: MRN images were obtained using a standard 1.5 Tesla magnet and custom built phased-array coils. Patients were imaged using T1-weighted spin echo without and with gadolinium, T2-weighted fast spin echo with fat peripheral nerve tumors (three neurofibromas and one schwannoma), two with intraneural cysts, and three with traumatic peripheral nerve lesions. Six patients with peripheral nerve mass lesions underwent surgery, thereby allowing MRN images to be correlated with intraoperative and pathological findings. RESULTS: Preoperative MRN accurately imaged the normal fascicular anatomy of peripheral nerves and precisely depicted its relation to tumor and cystic lesions. Increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences was seen in the peripheral nerve fascicles of patients with clinical and electrodiagnostic evidence of nerve injury. CONCLUSION: MRN proved useful in the preoperative evaluation and planning of surgery in patients with peripheral nerve lesions.

Adult↗
PubMed1994

Safety and efficacy of iopromide in cerebral arteriography.

RATIONALE AND OBJECTIVES: Iopromide is a new nonionic monomeric contrast medium for cerebral arteriography. This agent has been approved for sale in over 45 countries; however, it is still undergoing clinical review in the United States. This study evaluated the safety and efficacy of iopromide in comparison with two other nonionic contrast media. METHODS: A total of 173 patients participated in the study, which was prospective, double-blind, and randomized. In two centers, patients received iopromide or iohexol; in the other three centers, patients received iopromide or iopamidol. Adverse events were monitored by investigators, and efficacy was evaluated by grading the radiographic images. RESULTS: Most adverse events were mild or moderate in severity; all resolved completely. Twenty-one percent of patients given iopromide were reported to have a drug-related adverse event, versus 44% of patients given a comparator. No statistically significant difference emerged between iopromide and the comparators with regard to efficacy. CONCLUSIONS: These study results indicate that iopromide is a safe and effective contrast medium for cerebral angiography.

Cerebral Angiography↗
PubMed1992

Measurement of blood-brain barrier permeability in a tumor model using magnetic resonance imaging with gadolinium-DTPA.

Sequential MR imaging with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and sequential measurements of plasma Gd-DTPA concentration by inductively coupled plasma atomic emission spectroscopy (ICP-AES) were used to estimate the blood-to-tissue transport coefficient (Ki) in the 36B-10 rat glioma model. For these measurements, tissue Gd-DTPA concentration was estimated from tumor enhancement by correlation with calibration measurements obtained by ICP-AES analysis of tumor tissue. The 14 animals for which Ki was calculated can be grouped into those imaged at 11 days following tumor implantation, at 13-18 days, and at 20 days. The mean (+SEM) Ki values for these groups were 1.1 + 0.24, 9.2 + 0.8, and 13.4 + 1.7 ml/kg-min, respectively. These results correspond well with published data obtained by quantitative autoradiography. It is concluded that frequent sequential imaging and a graphical approach to Ki calculation are promising methods for determining the blood-to-tissue transport coefficient noninvasively by contrast-enhanced MRI.

Animals↗
PubMed1989

Multicenter double-blind placebo-controlled study of gadopentetate dimeglumine as an MR contrast agent: evaluation in patients with cerebral lesions.

A multicenter double-blind randomized study was designed to evaluate and compare the safety and diagnostic efficacy of gadopentetate dimeglumine (Gd-DTPA) (0.1 mmol/kg) against a saline placebo for use as an IV contrast agent for MR. The randomization code provided for a 2:1 ratio of Gd-DTPA and saline patients. Six investigators studied 88 patients with signs and symptoms of a cerebral lesion. Although safety data were complete in all 88 cases, only 83 had valid efficacy data (57 received Gd-DTPA, 26 placebo). Three patients were excluded from efficacy evaluation because of incomplete scans or scans with severe motion artifacts. Two patients were excluded for protocol variations (did not have a mass lesion). The protocol required that spin-echo MR images be acquired both before and after infusion at mode 1, 500/30/2 (TR/TE/excitations), and at a single-echo mode 2 sequence within a selected range, 1500-2000/56-90/2. Additional TEs could also be used at the discretion of each investigator. Efficacy was determined by comparing post- with preinjection images for relative degree of enhancement and improvement of diagnostic ability after injection, and by comparing these results with placebo results. Enhancement was reported in 43 (75%) of 57 Gd-DTPA patients and in none of the 26 placebo patients. Improvement of diagnostic ability was noted in 37 of 57 Gd-DTPA patients and in no placebo patients. Of 17 patients receiving Gd-DTPA for whom no diagnosis could be made before infusion, nine of 17 were diagnosed after infusion. By comparison, none of five patients not diagnosed before infusion of placebo could be diagnosed after infusion. Of 43 patients in whom lesion enhancement was observed after Gd-DTPA infusion, the diagnosis changed after infusion in 16 (37%) and the number of lesions detected after infusion increased in 10 (23%). Safety studies showed no clinically significant abnormal trends. Minor changes in blood pressure, pulse, and serum iron levels were noted in a higher percentage of Gd-DTPA patients. This study confirms that Gd-DTPA is an efficacious contrast agent for use with MR and that it exhibits excellent patient tolerance. Enhancement allows for a decisive diagnosis to be made in selected cases in which such capability had previously been lacking with unenhanced MR.

Adolescent↗
PubMed1984

Atlanto-axial instability and spinal cord compression in children--diagnosis by computerized tomography.

Five children who were at risk for atlanto-axial instability underwent computerized tomography scanning of the cervical spine in flexion and extension to document the degree of bone instability and the presence or absence of spinal cord compression. Two patients had Morquio's syndrome, two had os odontoideum , and one had Klippel-Feil syndrome, and in all five the lateral radiographs of the cervical spine in flexion and extension were equivocal with regard to instability or were difficult to interpret because of the bone anomalies. The computerized tomography scan then provided a diagnosis by a non-invasion technique and quantitated the amount of compromise of the spinal cord by delineating flattening of the cord. The scan therefore helped the surgeon to decide if the spinal cord was at significant risk and if atlanto-axial fusion was advisable.

Atlanto-Axial Joint↗
PubMed1982

Computed tomographic assessment of squamous cell carcinoma of oral and pharyngeal cavities.

Computed tomographic (CT) scans were prospectively obtained on 68 patients with previously untreated stages III and IV squamous cell carcinoma of the oral and pharyngeal cavity. We report herein the results of CT evaluation of primary disease arising in these sites, improvements in contrast-enhancement techniques, and CT assessment of the patient's condition after radiation or chemotherapy treatment.

Biopsy↗
PubMed1981

Computerized axial tomography with air contrast of the cerebellopontine angle and internal auditory canal.

The introduction of computerized axial tomography (C.T.) in 1973 completely changed the diagnostic evaluation of acoustic neuromas. Seventy to eighty percent of all acoustic neuromas can be diagnosed with intravenous enhanced C.T. scan. Acoustic tumors with a diameter of less than 1.5 cm, however, are not consistently seen on C.T. scan. Twenty-six consecutive patients were evaluated by C.T. scan with air contrast posterior fossa myelography (C.T. air cisternography). Nineteen studies were normal, with complete air filling of the internal auditory canal. Surgically verified acoustic neuromas were demonstrated in four patients. Two studies were inconclusive and there was one false positive. Other than headaches, there is no morbidity associated with this technique. C.T. air cisternography should be considered as the definitive study for evaluating patients for acoustic neuromas who have normal intravenous contrast enhanced C.T. scans. This study reports the first intracanalicular tumor diagnosed with this technique.

Adult↗