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Biomedical subjects

M R Fisher

Publications and source records attributed to M R Fisher.

At least 19 recordsLinked to original sources
PubMed1995

Decreased splanchnic perfusion measured by duplex ultrasound in humans undergoing small volume hemorrhage.

OBJECTIVES: To quantitate duplex Doppler measurements of splanchnic perfusion to determine if these measurements are reproducible in euvolemic humans and if such measurements are sensitive to mild degrees of systemic hypovolemia. DESIGN: Prospective, nonrandomized, controlled trial. SETTING: Clinical research center. PARTICIPANTS: Seven fasting, healthy male and female volunteers, ranging in age from 25 to 37 yrs and weighing 60 to 90 kg. INTERVENTIONS: Pulse, blood pressure, hematocrit, and duplex Doppler measurements of the peak systolic velocity and time averaged velocity of the subdiaphragmatic aorta, celiac artery, and superior mesenteric artery were obtained at four time points. Time points I and II were on separate days before hemorrhage and consisted of routine blood donation of 450 mL. Time point III was immediately after blood donation. Time point IV was 24 hrs after donation. Estimated blood flow was calculated from time averaged velocity (estimated blood flow = 60[vessel cross-sectional area][time averaged velocity]). MEASUREMENTS AND MAIN RESULTS: Vital signs and hematocrit remained without significant change at all time points. Peak systolic velocity, time averaged velocity, and estimated blood flow were also unchanged between measurements at time points I and II. However, after a mean reduction of 9.1% of total blood volume, duplex ultrasound detected significant decreases of 14.5% in celiac artery and superior mesenteric artery peak systolic velocity, as well as 15.1%, 17.3%, and 20.2% decreases in aorta, celiac artery and superior mesenteric artery time averaged velocity and estimated blood flow, respectively (all values p < .05 vs. baseline, Duncan's multiple range test). All measured variables returned to baseline 24 hrs after hemorrhage. CONCLUSIONS: Noninvasive duplex Doppler measurements of splanchnic peak systolic velocity, time averaged velocity, and estimated blood flow are reproducible and sensitive to small changes in intravascular volume. These data suggest a potential clinical role for duplex imaging in the treatment of critically ill patients to guide therapy to optimize splanchnic perfusion.

Adult↗
PubMed1993

Factors influencing response to strabismus surgery.

Based on analyses in a series of 116 patients, we found that the response to strabismus surgery (degrees of change of ocular alignment per millimeter of rectus recession) correlated significantly with the preoperative deviation for esotropic and exotropic patients. The prediction of response to strabismus surgery was not improved significantly with the inclusion of axial length, age, and/or preoperative refractive error beyond the prediction provided with use of only the preoperative deviation, even though we have previously suggested that the response to strabismus surgery should be related to axial length. We believed that larger eyes should have a smaller response for the same number of millimeters of surgery than smaller eyes. We now believe that although the response to strabismus surgery does correlate significantly and inversely with axial length, this correlation may not be clinically important given the much stronger influence of preoperative deviation.

Adolescent↗
PubMed1993

A diet history questionnaire ranks nutrient intakes in middle-aged and older men and women similarly to multiple food records.

We evaluated the reproducibility of a modified version of the National Cancer Institute diet history questionnaire and also studied comparability of nutrient estimates from this questionnaire to those from four 2-d food records. Subjects (n = 211) were from a population-based sample of middle-aged and older adults participating in the Beaver Dam Eye Study in south-central Wisconsin. Median age-specific correlation coefficients between the questionnaire, administered twice at a 3-mo interval, were 0.8 in men and 0.7 in women (range = 0.5 to 0.9). Questionnaire estimates of protein, cholesterol, thiamin, niacin, iron and zinc were consistently lower than food record estimates whereas estimates of fat were higher. Correlation coefficients between estimates from the questionnaire and records were generally > 0.5, indicating overall good agreement in ranking. However, the range in correlation coefficients was wide [ranging from 0.06 for iron (without supplements) in middle-aged women to 0.8 for alcohol in middle-aged men and women]. Questionnaire estimates similarly classified persons into the lowest two food record quintiles of intake 50 to 93% of the time depending on nutrient. These results suggest that the questionnaire produces nutrient estimates that rank individuals on the basis of intake of most nutrients similarly to estimates from multiple food records.

Adult↗
PubMed1993

Gamma Knife thalamotomy and pallidotomy in patients with movement disorders: preliminary results.

The Leksell Gamma Knife is a useful and safe method to perform thalamotomy and pallidotomy in selected older patients with Parkinson's disease and related movement disorders. In this preliminary report, 2 of 3 patients with severe intention tremor were relieved of their symptoms by thalamotomy, as were 4 of 7 patients with Parkinson's tremor. Four of 8 patients had significant improvement of contralateral rigidity following pallidotomy.

Aged↗
PubMed1993

Leksell Gamma Knife treatment of tic douloureux.

Stereotactic radiosurgery under local anesthesia with the Leksell Gamma Knife can effectively treat some patients with recurrent tic douloureux after unsuccessful medical/surgical procedures. Seven of 12 patients have shown complete relief or improvement of their trigeminal neuralgia. No complications have been observed.

Adult↗
PubMed1993

Systemic hypertension produces pericyte changes in retinal capillaries.

PURPOSE: The purpose of this study was to examine retinal capillaries and their pericytes that previous research suggests to be contractile. A contractile role regulating capillary blood flow may be more apparent when the vasculature is subjected to the stress of systemic hypertension. METHODS: Using ultrastructural morphometry and the myosin subfragment-1 technique, retinal capillaries of normal and hypertensive rats were measured at three different time points, early, intermediate, and late (24, 44, and 68 wk). RESULTS: Hypertensive capillaries seemed to dilate at the early time point (P = 0.002), were constricted at the intermediate time point (P < 0.001), and did not redilate later. Wall thickness was enlarged at all times, pericyte coverage (the ratio of plasma membrane length in contact with the vascular circumference to the outer circumference of the endothelial tube) was greater at early and intermediate time points, and the total area of viable cytoplasm relative to the vessel wall area was increased at the intermediate time (all P < 0.001). Also, at the intermediate time, the circumferential coverage of the endothelial tube by actin filament bundles within pericytes and the actin area relative to the vessel wall area had increased (P < 0.001). CONCLUSIONS: These data indicate that the effects of systemic hypertension extend into the retinal capillary bed, causing pericyte change with actin increase and capillary constriction. They represent the first in vivo indirect evidence by morphologic criteria for pericyte contractility in retinal vascular disease.

Actins↗
PubMed1991

MRI of hepatic iron deposition in patients with renal transplant.

Excess hepatic iron deposition was found in five of 15 (33%) renal transplant patients undergoing magnetic resonance (MR) screening for avascular necrosis of the femoral heads. Only one of these patients had overt liver disease. The number of prior blood transfusions was a significant factor for this deposition, whereas the age and sex of the patients, number and type of transplants, histocompatibility alleles (HLA), and years of hemodialysis and of chronic renal failure were not significant etiological factors. Liver/fat intensity ratios of less than 0.29 on T1-weighted images and ratios of less than 0.21 on T2-weighted images and a calculated T2 value of less than 35 ms were the best indicators of iron overload. Renal transplant patients are at great risk for excess hepatic iron deposition and MR imaging is a promising tool for the diagnosis of iron overload in this patient population.

Adult↗
PubMed1991

MRI of cardiac pseudoaneurysm and other complications of myocardial infarction.

The purpose of this paper is to review the spectrum of pathology revealed by cardiac magnetic resonance (MR) in the evaluation of myocardial infarction. In addition, the paper is intended to provide a concise introduction to the capabilities and limitations of MR in the evaluation of myocardial infarction and its complications. To provide this introductory guide, three cases of infarction are reviewed in detail, including one unusual case of infarction with both true and false ventricular aneurysm formation. A selected review of the literature is included to demonstrate the current role of MR in the work-up and follow-up of acute infarction.

Aged↗
PubMed1990

Relationship between rate of patient enrollment and quality of clinical center performance in two multicenter trials in ophthalmology.

Those responsible for managing and overseeing multicenter clinical trials often express concern that differential rates of patients enrollment among participating clinical centers may be reflected in poorer compliance with study protocols or poorer patient care in the centers enrolling fewer patients. The purposes of the present investigation were (1) to determine whether rate of patient enrollment was related to other measures of clinical center performance in two multicenter clinical trials in ophthalmology, the Macular Photocoagulation Study (MPS) and the Early Treatment Diabetic Retinopathy Study (ETDRS), and (2) to compare findings from these two studies with findings reported from cooperative oncology groups. Percent of major data forms ever failing computerized edit was the only measure of performance examined that demonstrated a strong positive relationship to rate of patient enrollment in both studies under both analytic approaches employed (F test for linear trend in means and Spearman's rank correlation). In the MPS, but not in the ETDRS, percent of patients who had missed all visits scheduled during the past 12 months (inactive patients) also was related to rate of patient enrollment. However, the major finding from this investigation has been that it is not possible to predict overall performance of an individual clinical center based on rate of patient enrollment. Clinical centers enrolling fewer patients in these multicenter clinical trials performed in some areas as well as or better than centers enrolling larger numbers of patients.

Diabetic Retinopathy↗
PubMed1989

Magnetic resonance for evaluation of the thorax.

Evaluation of diseases in the chest by MR is continually evolving. Early studies showed the potential of the technique for imaging the mediastinal and hilar structures and for demonstrating the normal anatomy of the thorax on sagittal, coronal, and transverse MR images. As more data have been compiled, investigators have compared MR to computed tomography for its ability to assess mediastinal and hilar adenopathy and masses, bronchogenic carcinoma and other pulmonary parenchyma lesions, and for assessment of the pulmonary vascularity. MR has been shown in these situations generally to provide equivalent information to that provided by computed tomography. MR, compared to computed tomography, is still in its infancy in regard to the length of time of its availability and in relation to the MR technology for obtaining images. MR is a technique that has wide variation as to type of image quality obtained depending upon the MR system utilized and the pulse sequence utilized. Because of the diverse nature of potential variables for imaging, many times the images are not equal in quality. As a consequence of this significant variability, the data in the literature are divergent on the precise utility of MR. Although the recommended use of MR may change rapidly, the current feeling is that MR should be used as a procedure complementary to computed tomography in those patients with allergy to iodinated contrast material and to aid in defining equivocal lesions as seen on computed tomography, such as small central hilar bronchogenic carcinomas.

Humans↗
PubMed1987

Endometrial carcinoma staging by MR imaging.

The potential of magnetic resonance (MR) imaging in the detection of endometrial carcinoma and in the assessment of its extent was evaluated prospectively in 51 patients clinically suspected of having the disease. MR imaging findings were compared with the results of surgical-pathologic staging and lymph node sampling following hysterectomy. Histologic findings showed 45 patients to have endometrial carcinoma, three to have no residual tumor after dilatation and curettage, and three to have adenomatous hyperplasia of the endometrium. MR imaging demonstrated an endometrial abnormality in 43 of the 51 patients (84%). Endometrial carcinoma could not be differentiated from adenomatous hyperplasia or blood clots. Therefore, MR imaging was not specific for tumor detection, and histologic diagnosis remains essential. The overall accuracy of MR imaging in staging endometrial carcinoma was 92%; its overall accuracy in demonstrating the depth of myometrial invasion was 82%. Demonstration of lymphadenopathy and adnexal or peritoneal metastases by MR imaging was suboptimal.

Adult↗
PubMed1987

Hyperparathyroidism: comparison of MR imaging with radionuclide scanning.

Twenty-three patients with hyperparathyroidism were evaluated preoperatively with magnetic resonance (MR) imaging. Twenty patients also underwent thallium-201/technetium-99m scintigraphy. Of 22 patients with primary hyperparathyroidism, 12 had persistent or recurrent disease. One had secondary hyperparathyroidism due to end-stage renal disease. MR imaging allowed accurate localization of abnormal parathyroid glands in 64% evaluated prospectively and 82% evaluated retrospectively. Scintigraphy allowed localization of 60% evaluated prospectively and 70% retrospectively. The two imaging modalities together allowed detection of 68% evaluated prospectively and 91% retrospectively. MR imaging allowed detection of two of five mediastinal adenomas evaluated prospectively and four of five retrospectively. In patients who underwent both imaging studies, MR was more successful in those with previous neck surgery (73% evaluated prospectively and 91% retrospectively) than in those with no prior surgery (57% prospectively and 71% retrospectively). Scintigraphy allowed accurate localization in 64% evaluated prospectively and 64% retrospectively in patients with previous surgery versus 57% prospectively and 86% retrospectively in patients with no prior neck surgery. Four false-positive results were obtained with MR imaging and three with scintigraphy. MR imaging was useful for parathyroid localization in patients with hyperparathyroidism, particularly in patients requiring additional surgery.

Adult↗
PubMed1987

Acute myocardial infarction: MR evaluation in 29 patients.

This study evaluated the ability of MR to identify and characterize the region of myocardial infarction in humans. Twenty-nine patients, all with ECG and enzyme rises consistent with an acute myocardial infarction, were studied by MR 3-17 days from the onset of acute chest pain. Four patients were excluded because of inability to acquire adequate MR studies. For comparison, 20 normal subjects were studied who also had gated MR examinations. The site of infarction was visualized in 23 patients as an area of high signal intensity in relation to the normal myocardium, a contrast that increased on the second-echo image. The regions of abnormal signal intensity corresponded to the anatomic site of infarction as defined by the ECG changes. The mean T2 relaxation time of the infarcted myocardium (79 +/- 22 msec) was significantly prolonged in comparison with the mean T2 (43.9 +/- 9 msec) of normal myocardium (p less than .01). The mean percentage of contrast (intensity difference) between normal and infarcted myocardium was much greater on the second-echo images (65.6 +/- 34.0%) than the first-echo images (27.5 +/- 18.7%). In the normal subjects there was no difference in T2 between the anterolateral (40.3 +/- 5.7 msec) and septal (39.5 +/- 7.4 msec) regions, and percentages of contrast between these two regions of myocardium on the first-echo (9.1 +/- 7.4%) and second-echo (15.0 +/- 13.3%) images were similar. Thus, MR can be used to directly visualize acute infarcts. However, it has several pitfalls, including the necessity to differentiate signal from slowly flowing blood in the ventricle, from increased signal from a region of infarction and artifactual variation of signal intensity in the myocardium due to respiratory motion or residual cardiac motion.

Adult↗
PubMed1987

MR imaging of congenital anomalies of the aortic arch.

Eighteen patients with congenital aortic arch anomalies were evaluated by ECG-gated MR imaging. Transverse images encompassing the heart and thoracic aorta were available in all patients; sagittal or coronal studies were available in 12 patients. Visualization of the aortic arch, its orientation, and the origin and course of the arch vessels was assessed. Associated intracardiac abnormalities were noted, and the effect of aberrant vessels on the trachea or esophagus was determined. Thirteen patients had a right aortic arch. Mirror-image branching was found in 10 cases, and an aberrant left subclavian artery was found in three of these. Three patients had a left aortic arch with aberrant right subclavian artery, and two patients had a double arch. Tracheal compression caused by vascular rings was found in two patients with respiratory symptoms. Corroborating studies (angiography, surgery, CT, and autopsy) in 16 patients confirmed the MR diagnoses in all but one. We conclude that MR could substitute for other techniques as an effective, noninvasive method for the evaluation of congenital aortic arch anomalies.

Adolescent↗