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Biomedical subjects

D D Patton

Publications and source records attributed to D D Patton.

At least 37 records · Page 2Linked to original sources
PubMed1992

Skin damage associated with the Norplant contraceptive.

Three cases of localized skin reaction in the first month after implantation of the Norplant contraceptive resulted in a partial implant expulsion and removal in one patient, and implant removal in another. Clinical evidence of infection was absent in all patients. While lidocaine with epinephrine was used in all three patients, the cause for these skin reactions remains unclear. Physicians should be alerted to the possibility of significant skin reactions associated with this procedure.

Adult↗
PubMed1990

A full-field modular gamma camera.

A modular gamma ray camera is described that gives useful image information over its entire crystal face. The lack of dead area on the periphery of the camera is made possible by a unique application of digital electronics and optimal position estimation using maximum likelihood (ML) estimates. The ML estimates are calculated directly from photomultiplier tube responses and stored in a lookup table, so the restriction of calculating the position estimates in separate circuitry is removed. Each module is designed to be optically and electronically independent, so that many modules can be combined in a large system. Results from a prototypical module, which has an active crystal area of 10 cm X 10 cm, are presented.

Equipment Design↗
PubMed1989

A utility-based model for comparing the cost-effectiveness of diagnostic studies.

The effective cost of a diagnostic test is the money spent per unit of diagnostic performance. The latter can be measured as diagnostic utility (DU), the probability-weighted sum of the utilities of the four test outcomes TP, TN, FP, and FN: DU = U(TP)P(TP) + U(TN)P(TN) + U(FP)P(FP) + U(FN)P(FN). DU (which also is called expected utility) incorporates the clinical decision analytic variables sensitivity (Se), specificity (Sp), equivocal fraction (EF), disease probability (P(D)), and outcome utility (U). DU is not an inherent property of a diagnostic test but of test-observer interactions in a clinical setting. The model sets the effective cost (EC) of a diagnostic test = actual direct cost (ADC)/DU. When DU = 1 (perfect test) EC = ADC and the patient benefits from the test dollar for dollar. When DU less than 1, EC exceeds ADC. If DU approaches O, EC becomes infinite; the test has no effectiveness at any cost. DU depends strongly on P(D) if Se and Sp differ significantly; then EC also depends on P(D), and the effective cost of a test performed in the wrong P(D) setting may be several times its actual direct cost. This model of comparing effective costs compares actual direct cost with clinical measures of test performance and utility values that allow expression of patient/doctor fears and preferences. It offers a more clinically realistic setting than models based on costs alone.

Cost-Benefit Analysis↗
PubMed1989

Whole-body lymphangioscintigraphy: preferred method for initial assessment of the peripheral lymphatic system.

In 20 patients with congenital and acquired lymphedema in either upper or lower extremities and in four patients without extremity edema, human serum albumin labeled with technetium-99m was injected intradermally into a digital web space of the hand or foot. With a digital gamma camera that permitted a "sweep" of the torso, serial extremity and whole-body lymphagioscintigraphy (LAS) of the peripheral lymphatic system was performed. In 11 patients with acquired lymphedema, a well-defined obstructive pattern was seen, characterized by discrete peripheral lymphatic trunks, delayed or absent depiction of regional nodes, and delayed but extensive soft-tissue tracer extravasation. Five of nine patients with congenital lymphedema showed hypoplasia characterized by poorly defined lymphatic trunks, delayed depiction of regional nodes, and early and extensive extravasation of tracer. The other four patients showed aplasia, with absence of trunks, no depiction of nodes, and little or no tracer extravasation. LAS is technically simple to perform and requires no special training. Radiation exposure is minuscule, and the procedure is safe and without apparent side effects. For these reasons, whole-body LAS should be the preferred method for the initial assessment of congenital or acquired lymphedema.

Adolescent↗
PubMed1987

Intravenous platelet activating factor does not affect lung epithelial permeability.

Administration of platelet activating factor has been shown to produce lung edema in several species including the rabbit. To determine if platelet activating factor increases lung alveolar epithelial permeability, we studied the effect of intravenous platelet activating factor administration on clearance of 99mTc-DTPA from the lung of the rabbit. Intravenous platelet activating factor produced marked hemodynamic and cellular responses but did not increase the clearance of 99mTc-DTPA from lung to blood. We conclude that although platelet activating factor can induce lung edema in the rabbit, it does not produce an acute increase in alveolar epithelial permeability.

Animals↗
PubMed1986

Hemodynamic comparison of ventricular pacing, atrioventricular sequential pacing, and atrial synchronous ventricular pacing using radionuclide ventriculography.

To assess the hemodynamic effects of physiologic pacing, 13 patients with DDD pacemakers who had varying degrees of atrioventricular (AV) block were studied with radionuclide ventriculography during VVI, DVI and VDD modes. Radionuclide ventriculography was performed with patient in the supine position at rest 5 to 10 minutes after the pacing mode and AV delay were changed. The AV delays selected were short (mean 147 +/- 4.8 ms) and long (mean 197 +/- 4.8 ms), with a constant difference of 50 ms. During VVI, 6 patients (group 1) had a left ventricular ejection fraction of 40% or less (mean 22 +/- 11) and 7 patients (group 2) had an ejection fraction of more than 40% (mean 59 +/- 11). Comparisons of ejection fraction, end-diastolic volume and cardiac index between VVI and both modes of AV pacing (VDD and DVI) and between long and short AV delays led to the following conclusions: DVI or VDD pacing produces more beneficial hemodynamic effects than VVI, and these effects are more pronounced in patients with low ejection fraction if longer AV delay is used. The VDD mode significantly improves ventricular function over the DVI mode in patients with an ejection fraction of more than 40% independent of heart rate. Longer AV delay is essential in patients with an ejection fraction of 40% or less to improve ventricular function with physiologic pacing.

Adult↗
PubMed1986

Functional studies in brain and heart with positron emission tomography.

Positron Emission Tomography (PET) has evolved in the last years into a powerful research technique for the study of the physiology and pathophysiology of the human brain in vivo. These procedures now need no longer be viewed only as research studies. They are ready to be applied clinically on a wide scale. This article will give a short overview of the technical and methodological background and outline the clinical research applications by using the most developed tracers in the field: glucose and its analogs, oxygen, fatty acids, various perfusion markers and receptors, all labelled with positron emitting isotopes. They allow the quantitative measurement of local tissue functions in an essentially non-invasive way.

Brain↗
PubMed1986

Glucose transport and utilization in the human brain: model using carbon-11 methylglucose and positron emission tomography.

3-0-[11C]-Methyl-D-glucose (CMG) is specifically suited for measuring carrier facilitated glucose (G) transport; it enters the free G pool in tissue from where it is not utilized for metabolism in contrast to G, but is transported back into circulation. The ratio of carrier affinity for G and CMG was reported to be 1.11. By simultaneously measuring CMG concentration in plasma and in cerebral cortex in vivo with positron tomography at 1-min intervals for 40 min, two time-activity curves are obtained, as reported previously, which together with the G concentration in plasma yield the in vivo rate constants of G transport across the blood-brain barrier and the rate of G inflow; a repeat measurement at a different G concentration in plasma gives the in vivo Michaelis-Menten constant KM and the maximal rate of transport VMAX. The present paper summarizes and extends this approach to analyzing the free G pool in tissue, the rate of G return to circulation, and the rate of G exit into metabolism with its corresponding rate constants. The data from six volunteers agreed with results reported for the individual biochemical parameters in primate brains.

3-O-Methylglucose↗
PubMed1985

Effect of noise correlation on detectability of disk signals in medical imaging.

Pixel signal-to-noise ratio is one accepted measure of image quality for predicting observer performance in medical imaging. We have found, however, that images with equal pixel signal-to-noise ratio (SNRp) but different correlation properties give quite different observer-performance measures for a simple detection experiment. The SNR at the output of an ideal detector with the ability to prewhiten the noise is also a poor predictor of human performance for disk signals in high-pass noise. We have found constant observer efficiencies for humans relative to the performance of a nonprewhitening detector for this task.

Fourier Analysis↗
PubMed1982

Subjective vs. objective evaluation of gallbladder opacification during oral cholecystography in comparative clinical trials: implications for studies involving visual assessment.

Radiographs and CT images taken during oral cholecystography in dogs were interpreted in an independent, blind fashion by three radiologists on two occasions and visual assessment of gallbladder density compared to the actual CT values. While there was significant intra- and inter-observer variation, the mean scores for the observers' interpretations of both radiographs and prints correlated well with the actual CT values (p less than 0.05). In five out of six comparisons between first and second readings, the observers gave a lower score on the second reading. The considerable variation reflects the problems inherent in subjective evaluation of agents that produce small but measurable differences in radiographic density. Studies involving such subjective data have to be carefully designed in order to obtain meaningful results.

Administration, Oral↗
PubMed1981

Left lateral view in liver scans.

The left lateral view (LLV) in liver scans is not a routine view in many institutions and has not been thoroughly described in the literature. To determine the limits of normal in the LLV, the authors examined this view in liver scans of 56 patients whose six-month follow-up showed no clinical or laboratory evidence of liver disease. The distribution of normal shapes and axis angles is described. Neither of these descriptors showed significant correlation with age, sex, weight, height, or body surface area, except for a slight correlation between axis angle and sex. The authors conclude that the appearance of the left lobe of the liver on LLV is not related to body habitus. The role of the LLV in routine liver scanning is yet to be defined.

Adolescent↗
PubMed1981

Mechanisms of satiety and gastric emptying after gastric partitioning and bypass.

The patterns of fundic and antral motility as well as changes in fundic pressure in response to balloon distention were evaluated in 26 patients before and after gastric partitioning (18 patients) or gastric bypass (8 patients). In addition, the rate of gastric emptying, as measured by the ingestion of 99mTc-tagged chicken liver, was determined after gastric partitioning (12 patients) and bypass (7 patients). A striking alteration in the motility of the fundus occurs after both gastric partitioning and bypass. Normal pressure waves of the fundus disappear with both procedures. Fullness after both operations is secondary to distension of the pouch rather than to an increase in pressure. Changes in antral motility, inhibition, and recovery seem to be neurally mediated. The gastric emptying rate was 6.9% +/0 2.9% per minute after gastric bypass and 1.8% +/- 0.4% per minute after partitioning. Delayed emptying could be an additional benefit of gastric partitioning.

Gastric Emptying↗