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Biomedical subjects

J H Simon

Publications and source records attributed to J H Simon.

At least 109 records · Page 6Linked to original sources
PubMed1987

Physiologic changes during high field strength MR imaging.

High field strength MR imaging systems may require several kilowatts of RF power to obtain images. A fraction of this power is absorbed by the patient, and changes in body temperature have been measured in experimental animals. The purpose of this study was to quantify changes in body surface temperature and other physiologic parameters in humans during MR scanning at 1.5 T. Blood pressure, heart rate, respiration, and axillary temperature measurements were obtained on 27 normal volunteers. Measurements were made at RF power levels of 0, 0.2, and 0.8 W/kg, with the power sequence randomized. In 14 volunteers receiving lumbar scans, statistically significant increases in temperature were observed at RF power levels of 0.2 (+0.2 +/- 0.1 degree C) and 0.8 (+0.5 +/- 0.1 degree C) W/kg. No significant changes related to RF power were observed in blood pressure or respiratory rate. At the 0.8 W/kg level there was a slight increase in heart rate (3 +/- 1.3 beats per minute). In the 13 patients receiving head scans, physiologic changes were substantially smaller. The temperature increases and other physiologic changes observed during MR scanning with the 1.5 T imager at RF powers of 0.2 and 0.8 W/kg were small and of no clinical concern. Additional studies should be performed in patients with cardiac failure, vascular occulusion, and metallic implants or prostheses.

Adult↗
PubMed1986

Corpus callosum and subcallosal-periventricular lesions in multiple sclerosis: detection with MR.

Examination with magnetic resonance imaging of 40 patients with confirmed diagnoses of multiple sclerosis showed that corpus callosum involvement is common. Thirty percent of the patients had focal callosal lesions similar to those described in the pathology literature. Long, inner callosal-subcallosal lesions were found in 55% of patients. These lesions had signal characteristics similar to those of noncallosal periventricular lesions. Diffuse moderate to severe atrophy of the corpus callosum was noted in 40% of patients, with one exception concurrent with inner callosal lesions. The nature of the inner callosal lesions is not known, since these lesions are not typically described in the literature. These lesions may represent demyelination or increased water content and may be the precursor to atrophy that progresses from the ependymal surface toward the outer fibers of the corpus callosum.

Adult↗
PubMed1986

Neurologic complications in diabetics after metrizamide lumbar myelography.

Recognized risk factors for metrizamide myelography are seizure disorder, seizure-threshold-lowering drugs, dehydration, and possibly age. After observing serious neurologic complications in diabetic patients after routine metrizamide myelography, a retrospective study was conducted to determine if diabetes should be considered another independent and important risk factor. Forty-one diabetic patients who had lumbar metrizamide myelograms were compared with a control group of 110 nondiabetic patients. A significantly higher incidence was found of severe vomiting (15% vs. 3%, p less than 0.01) and neurologic complications (20% vs. 2%, p less than 0.001) in the diabetic population. Neurologic complications included one case each of seizure, severe encephalopathy, auditory and visual hallucinations, and prolonged somnolence and four cases of confusion-anxiety. Four of the diabetic patients had major transient elevations of blood pressure. These findings suggest that diabetics are a high-risk population for metrizamide myelography. The dose of metrizamide should be minimized, whenever possible. The new nonionic myelographic agents may prove to be safer in this population, but caution and careful follow-up should be exercised in the initial trials with these patients.

Aged↗
PubMed1986

The effect of subarachnoid metrizamide and iohexol on cerebral glucose metabolism in vivo.

We studied the effect of metrizamide and iohexol on local cerebral glucose utilization (LCGU) using autoradiography. Metrizamide or iohexol was introduced into the subarachnoid space of rabbits and positioned over the right hemisphere for 3 or 6 hours. Using the unexposed (left) hemisphere as an internal control, we calculated relative changes in LCGU. In the three metrizamide-exposed animals the LCGU was decreased over the contrast media-exposed right temporoparietal cortex (L-R difference was positive). There was no significant changes in LCGU and no positive L-R difference after treatment with iohexol (three animals). We conclude that metrizamide does affect glucose metabolism in vivo, and this effect is dependent on localization of the contrast medium. The clinically safer drug, iohexol, in similar concentration and higher osmolality, did not decrease glucose metabolism.

Animals↗
PubMed1985

Progression of congenital anterior polar cataracts in childhood.

We studied five patients with the unusual and insidious progression of congenital anterior polar cataracts during childhood. All five children ultimately required surgery. In two children the progressive opacification occurred in posterior portions of the lens and was inapparent to parents. We therefore recommend a regular and careful follow-up of all children with anterior polar cataracts.

Adult↗
PubMed1984

Root extrusion. Rationale and techniques.

The root extrusion techniques are easily mastered and are within the realm of every general practitioner. They can be applied in various situations in which restoration is very difficult or impossible. The dentist must first decide whether or not elevating the root up to 4 mm will help treatment. If the answer is yes, then many different methods can be used to accomplish this goal. Teeth that were formerly extracted can now be saved and restored routinely, leading to a functional and esthetically pleasing result.

Dental Caries↗
PubMed1982

Endotoxic activity in periapical lesions.

Thirty tissue samples were examined histologically and classified as being inflamed (apical granulomas) or noninflamed (scars or noninflamed cysts). The samples were then homogenized in pyrogen-free water and treated to remove interfering substances. The presence of endotoxin was then determined by means of the limulus assay; 75 percent of the inflamed tissues were positive for endotoxin, while only 20 percent of the noninflamed tissues contained endotoxin. The presence of endotoxin was thus highly correlated (p = 0.015) with the presence of inflammation in these tissues.

Endotoxins↗
PubMed1980

Clinical and histologic evaluation of extruded endodontically treated teeth in dogs.

Clinical and histologic observations were made on three dogs at postextrusion intervals of 2, 4, and 7 weeks. At 2 weeks radiolucent areas were seen surrounding the roots. Histologically, however, these areas contained new immature bone or osteoid and a periodontal ligament of normal width. By the seventh week the radiographic picture was essentially normal, and this was confirmed histologically.

Animals↗
PubMed1980

Radiographic changes of the jawbones in end stage renal disease.

Thirty-eight patients with a history of end stage renal disease (ESRD) were evaluated with panoramic and periapical radiographs for changes in lamina dura, trabecular pattern, radiographic density, and pulp chamber size, as well as the presence of radiolucent lesions not associated with the roots of teeth. Partial or complete loss of lamina dura, delicate of absent trabecular patterns, and an overall granular or chalky white appearance associated with an increase in radiographic density were the most common alterations. These tended to occur together and were most easily observed in the lower molar area superior to the mandibular canal. Radiolucent lesions not associated with the roots of teeth, expansion of alveolar ridges, and radiographic loss of the cortical borders of the maxillary sinus, nasal floor, and mandibular canal were less common but were occasionally noted. Multiple correlation coefficients between radiographic changes and selected biomedical patient data were obtained by computer analysis, and their significance discussed. The pathogenesis of end stage renal disease was also reviewed.

Adult↗
PubMed1978

Extrusion of endodontically treated teeth.

Extrusion in a vertical direction was used in efforts to retain 14 teeth that had subcrestal fractures, perforations, or caries below the gingival tissue. Indications for the procedure, techniques, and complications are discussed.

Acid Etching, Dental↗