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Biomedical subjects

L Reese

Publications and source records attributed to L Reese.

At least 19 recordsLinked to original sources
PubMed1992

Correction for attenuation in technetium-99m-HMPAO SPECT brain imaging.

We present a correction technique that uses the effective bone and tissue attenuation coefficients to compensate 99mTc-HMPAO brain SPECT projections for attenuation. Transverse images of a human skull filled with a uniform mixture of 99mTc and gelatin have a greater count density at the center with respect to the periphery when corrected for attenuation with the effective water/tissue coefficient of 0.12 cm-1. An attenuation coefficient of 0.09 cm-1 produces uniform images at the expense of a reduced count density. Additional experiments with phantoms wrapped with aluminum (to simulate bone) indicate that the greater count density at the image center is a result of increased attenuation at the edges of the projections where there is a greater path length through the aluminum (or bone). SPECT projections explicitly corrected for both bone and soft-tissue attenuation result in images of improved uniformity and increased count density.

Brain↗
PubMed1992

Effects of dipyridamole infusion on human renal function observed using technetium-99m-DTPA.

Our observation that a prolonged dipyridamole infusion reduced or eliminated blood clearance of Gd-DTPA in dogs led us to investigate if dipyridamole, infused intravenously at rates comparable to those used in thallium myocardial perfusion tests, would alter renal filtration in humans. Renal filtration was assessed using a bolus injection of 10 mCi of 99mTc-DTPA in five males (19-63 yr old) with normal serum urea and creatinine. Twenty minutes following the bolus injection a 10-min intravenous infusion of either dipyridamole (0.14 mg/kg/min) or saline sham was given. Four to 10 min following the start of the dipyridamole infusion, a paradoxical rise in counts in the kidney region of interest was observed and persisted for 10 to 27 min. During this time, a 13% to 52% (mean +/- s.d., 40% +/- 16%, p less than 0.007) reduction in the exponential slope defining the clearance of counts from the cardiac region of interest occurred (implying a reduction of glomerular filtration rate), mean heart rate increased 27 +/- 5 bpm, p less than 0.002 and mean diastolic pressure decreased 12.9 +/- 6.4 mmHg, p less than 0.028. This finding indicates that renal clearance of tracers such as thallium or contrast agents such as Gd-DTPA is reduced during dipyridamole infusion.

Adult↗
PubMed1990

Hearing screening in a dental office using self-assessment.

Experiences in a statewide health fair screening program prompted development of alternate methods for screening hearing of adults including one in a dental office summarized here. Because it was considered impractical to use pure-tone screening, several self-assessment procedures were tested against pure-tone findings in a pilot study. As a result, the Rating Scale for Each Ear (RSEE) was selected for use. In the pilot and main study, 796 adult dental patients were evaluated and 21 to 29% failed the screening, depending on whether self-assessment procedures or pure tones were used. Although the dental office staff was generally supportive of the program, there were some problems in implementation. The number who returned for follow-up (N = 14) was disappointing, but there were several very positive benefits to the program including distribution of earplugs and education on the adverse effects of noise. In terms of general feasibility of such screening, from an epidemiology standpoint the program was judged to have good efficacy and efficiency but there were serious problems in effectiveness.

Adolescent↗
PubMed1987

Cost analysis of magnetic resonance imaging at St. Joseph's Health Centre of London.

In April 1986 St. Joseph's Health Centre of London, Ont., completed 3 years of operating a magnetic resonance imaging unit. The first 2 years were devoted to research and development. From Apr. 1, 1985, to Mar. 31, 1986, the unit operated as the first clinical service unit in Canada. Over the 12 months 1671 patients (an average of 9 patients per 12-hour day) were examined. Studies of the brain (62%) and the spine (21%) accounted for most of the procedures. The operating costs for the year were $892,000; revenues totalled $449,000, for a deficit of $443,000. The average technical cost per patient was $534. Increasing the number of patients examined per year would lower the cost to $431.

Brain Diseases↗
PubMed1986

Magnetic resonance imaging for detecting lesions of multiple sclerosis: comparison with computed tomography and clinical assessment.

Eighty-two patients with known or suspected multiple sclerosis (MS) were examined by means of magnetic resonance imaging (MRI) with a 0.15-T resistive scanner. The diagnosis could be made by MRI in 34 (97%) of the 35 patients with chronic, well-documented, stable MS and by high-volume delayed x-ray computed tomography (HVD CT) in only 6 (54%) of 11 patients in this group. The stage of the disease as judged from the MRI scans correlated poorly with the clinical status of the patient and with the known duration of the disease. MRI identified 28 (88%) of the 32 patients in whom MS was subsequently diagnosed by a neurologist, whereas regular contrast or HVD CT identified only 11 (52%) of 21 such patients. MRI is the most sensitive imaging modality for MS but is of little value in assessing the severity of the disease: many of the lesions seen on MRI scans are clinically "silent", and MRI does not usually detect small lesions in the brainstem, cerebellum or spinal cord that may be clinically significant.

Brain↗
PubMed1986

Hyperbaric oxygen therapy in chronic stable multiple sclerosis: double-blind study.

We carried out a randomized, double-blind, placebo-controlled trial of hyperbaric oxygen therapy (HBO) in patients with chronic stable MS. Eighty-two patients were treated in a multiplace hyperbaric chamber with gas supplied by mask. Forty-one patients received 20 consecutive daily treatments of 100% O2 followed by 7 "booster" treatments in the next 6 months; 41 control patients received "air" (12.5% O2 at 1.75 atmospheres absolute). There was no significant difference in treatment and control groups in the Extended Kurtzke Disability scores, Kurtzke Functional scores, magnetic resonance imaging, or evoked potentials after the initial 20 treatments or after the boosters. HBO is not effective in treating chronic stable MS.

Adult↗
PubMed1985

Quantitation of lung water by nuclear magnetic resonance imaging. A preliminary study.

Pulmonary edema was produced in four anesthetized dogs by saline lavage. The animals were maintained by assisted ventilation with O2/halothane and examined by a nuclear magnetic resonance (NMR) 0.15T resistive-magnet imager. The distribution of edematous fluid was clearly observed. Image contrast increased with prolongation of the cycle time (TR). Tomographic maps of spin-lattice relaxation times (T1) of the lungs were calculated from the NMR images. Comparison of T1 values with gravimetric measurements of water content of lung samples showed significant correlation (r = .7, P less than .02, n = 12) suggesting a potential for in vivo lung water quantitation by NMR imaging. This in vivo correlation is qualitatively similar to the in vitro correlation. Accurate in vivo determinations of pulmonary T2 values may require respiratory gating.

Animals↗
PubMed1982

Microanalysis of action and fear arousal as a function of differential levels of perceived self-efficacy.

Two experiments combining intergroup and intrasubject designs were conducted to test the hypothesis that self-percepts of efficacy operate as cognitive mediators of coping behavior and fear arousal. Differential levels of self-efficacy were induced in phobic subjects through either inactive mastery or modeling. Their coping behavior and accompanying fear arousal were then measured. In the next phase, self-efficacy was successively raised to designated levels within the same subjects, whereupon their behavior and fear arousal were again measured. Coping behavior corresponded closely to instated self-percepts of efficacy, with higher levels of perceived self-efficacy being accompanied by greater performance attainments. The efficacy-action relationship was replicated across different modes of efficacy induction, different types of behavioral dysfunctions, and in both intergroup and intrasubject comparisons. The hypothesis that fear arousal stems largely from perceived coping inefficacy also received support from the findings. As subjects' self-efficacy level was raised, they experienced progressively less anticipatory and performance distress while coping with threats. Results of a third experiment using cardiac acceleration and elevation in blood pressure as indicants of arousal further corroborate the generality of the relationship between perceived coping inefficacy and stress reactions.

Adolescent↗
PubMed1981

Radioimmunoassay of serum myoglobin in screening for acute myocardial infarction.

Over an 8-month period 289 patients consecutively admitted to a coronary care unit were studied to assess the value of serum myoglobin determinations by radioimmunoassay in screening for acute myocardial infarction. Of the 289 patients 127 (44%) had an infarction. It was found that when blood sampling was done within 5 to 15 hours after the onset of chest pain this assay had a sensitivity, specificity, and positive and negative predictive values of more than 97%. In this study healthy young adults had a mean serum myoglobin level of 37 +/- 11 (standard deviation) ng/ml, and values above 80 ng/ml were considered positive for acute myocardial infarction. False-positive results can be due to stock, vigorous exercise, skeletal muscle damage and several renal failure, but, except for the last one, these conditions also caused an increase in the serum level of the creatine kinase isoenzyme CK-MB.

Adult↗
PubMed1980

Relation of cord blood thyroxine and thyrotropin levels to gestational age and birth weight.

A program of screening cord blood for evidence of primary neonatal hypothyroidism was implemented in a general hospital. In 13 months 3456 newborns were screened: the thyroxine (T4) and triiodothyronine (T3) concentrations were measured in cord blood samples, and when the T4 level was below 8.0 micrograms/dl thyrotropin was also assayed in the sample. The two-tier program was effective. One hypothyroid newborn was detected and treated. More boys than girls had T4 levels below 8.0 micrograms/dl (9.7% v. 4.7%). The T4 level correlated with birth weight slightly better in the boys (r = 0.28 v. 0.21), and in the boys this correlation was stronger when the birth weight was lower. Regression analysis of the data for 54 sets of twins indicated that the T4 level was more strongly related to gestational age than to birth weight.

Birth Weight↗
PubMed1980

The retrocaval ureter: an intrinsic abnormality.

An 11-year-old boy underwent resection of an abnormally draining ureteral segment of a retrocaval right ureter. Compression by the inferior vena cava may have caused the faulty drainage. End-to-end ureteroureteral anastomosis was carried out. Intraoperative study of perfusion was helpful in the management of this child's condition.

Child↗
PubMed1979

Effect of insulin-induced hypoglycemia on the serum concentrations of thyroxine, triiodothyronine and reverse triiodothyronine.

The effect of insulin-induced hypoglycemia on serum thyroid hormone concentrations was studied in nine healthy individuals. Before, during and after the hypoglycemia blood samples were taken for measurement of the concentrations of glucose, thyroxine (T(4)), triiodothyronine (T(3)), reverse triiodothyronine (rT(3)), catecholamines and pituitary hormones.There was no change in the mean serum T(4) level (+/- the standard error of the mean) of 67 +/- 2 mug/l. However, the T(3) concentrations rose from a mean basal level of 1.86 +/- 0.06 mug/l to a mean peak of 2.51 +/- 0.21 mug/l (P < 0.01) at 45 minutes after the insulin injection, and the rT(3) concentrations fell from a mean basal level of 0.184 +/- 0.008 mug/l to a mean nadir of 0.171 +/- 0.022 mug/l (not a significant change). The mean peak epinephrine level was 545 +/- 103 ng/l and it occurred between 30 and 45 minutes after the insulin injection; the mean peak norepinephrine level was 584 +/- 114 ng/l and it occurred between 30 and 90 minutes after the injection. The growth hormone levels reached a mean peak of 26.1 +/- 4.8 mug/l and the plasma cortisol levels rose to 215 +/- 9 mug/l. The mean basal prolactin level was 8.5 +/- 0.9 mug/l; in five subjects there was a rise to a mean peak of 50.6 +/- 14.6 mug/l, whereas in the remaining four no significant increase occurred. No correlation was found between the changes in the serum T(3) concentration and any of the other factors studied.It was concluded that acute hypoglycemia is associated with a rapid increase in the serum T(3) concentration.

Adult↗