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Biomedical subjects

B Y Croft

Publications and source records attributed to B Y Croft.

33 records · Page 2Linked to original sources
PubMed1988

Considerations in the purchase of a nuclear medicine computer system.

Selection of a nuclear medicine computer system is a process that should be approached with care and forethought. The general scheme should be to define your needs and constraints, determine what is available, investigate the leading candidates, make a site visit, and, finally, submit an order. Through a series of discussions between members of the Computer Council of the Society of Nuclear Medicine and representatives from the manufacturers of computer systems, a set of important considerations emerged, which are reported in this paper. This paper is not intended to be a step-by-step guideline to the purchase of a computer system. Rather, it is a set of concepts and considerations with which the prospective purchaser should be familiar before undertaking such a purchase.

Computer Systems↗
PubMed1983

Effects of percutaneous transluminal angioplasty on renal plasma flow.

Percutaneous transluminal angioplasty is being used with increasing frequency for the treatment of renal artery stenosis. Several noninvasive techniques that utilize radioactive tracers have been used for monitoring the effects of angioplasty and progression of disease. Forty-one patients were studied before and after renal angioplasty by using renograms and fractionated measurements of effect renal plasma flow. Although there were striking examples of improvement in effective renal plasma flow following angioplasty, this was not a consistent finding. There was a tendency for effective renal plasma flow to revert to the baseline level on follow-up studies. Cure of hypertension was more likely in patients without renal insufficiency and in patients with shorter periods of sustained hypertension. Fractionated effective renal plasma flow studies did not reliably differentiate patients who were cured from those who were improved nor were we able to delineate clearly those requiring repeat dilatation. Nevertheless, this technique is useful for noninvasively measuring fractionated renal function in the immediate postoperative or postdilatation recovery period and for detecting the difference between occlusion of the renal artery and transient renal insufficiency due to contrast material. Also, long-term measurement of fractionated function has value in following potential progression of the basic disease process.

Adult↗
PubMed1983

Emission tomography of the kidney.

Single photon emission computerized tomography (SPECT) was done on two patients with suspected renal masses. Nuclear scintigraphy was equivocal on two tumors readily identified by SPECT. Single photon tomography is cost effective and increases the reliability of nuclear scintigraphy.

Adenocarcinoma↗
PubMed1982

Evaluation of digital image enhancement techniques for liver scintigrams.

Digital image enhancement techniques were employed in an effort to improve the resolution of Anger camera liver images. The premise employed was that methods which improve lesion detectability in liver phantoms should also do so in actual liver scintigrams. The types of image processing evaluated were: contrast enhancement, finite and infinite impulse response, modulation transfer function correction, homomorphic and median filtering. Observers were used to evaluate each method for its ability to improve lesion detectability using a five category rating system. The Localization Receiver Operating Characteristic (LROC) curve was used as the primary rank ordering method. A point system and analysis of variance were used as corroborative methods, incorporating measures of accuracy and consistency of the observers' answers.

Humans↗
PubMed1980

Cytopathogenic mechanisms of Entamoeba histolytica.

Cinemicrography of Entamoeba histolytica destruction of Chinese hamster ovary (CHO) cells shows that ameba cytopathogenicity consists of separate components: a contact-dependent cytolethal effect, and phagocytosis. Cells not in contact with amebae remain intact. Quantitation of ameba destruction of CHO cells by applying the one-hit hypothesis confirms that the cytoethal effect of amebae is contact dependent. Studies with 111Indium oxine-labeled cells provide further evidence of extracellular killing by E. histolytica and indicate that > 94% of the target cells are killed before phagocytosis. When we examined for a cytotoxin release by E. histolytica, we found no effect on CHO cells with filtrates of amebae, and a nonspecific effect of cell rounding and release with sonicates of amebae. The ameba sonicate effect was time-dose dependent, was not cytolethal, was reversible, and was inhibited by alpha II macroglobulin. Cytochalasin B altered ameba motility and morphology, and monolayer experiments confirmed that cytochalasins A, B, or D inhibited CHO cell destruction by E. histolytica. Cytochalasin D also inhibited extracellular killing of CHO cells by amebae in pellets, apparently independent of effects on ameba motility or phagocytosis. Colchicine and vinblastine, alone or in combination with cytochalasin D, did not inhibit E. histolytica cytopathogenicity, which indicates that microtubule function is not required for target cell killing by amebae.

Amebiasis↗
PubMed1979

Effects of biorhythms on blood flow distribution in the pregnant uterus (Macaca mulatta).

Ten rhesus monkeys were studied between 143 and 161 days of gestation. The unanesthetized animals were confined to restraining chairs and maintained in a controlled environment with continuous monitoring of spontaneous uterine dynamics. Forty-five determinations of blood flow distribution were made using radionuclide-labeled microspheres. The microsphere injections confirmed a circadian pattern of uterine blood flow. These biorhythms are related to alterations in distribution of blood flow to placental and nonplacental portions of the uterus. Myometrial blood flow is highest during the period of light. It is correlated positively to aortic blood pressure (r = 0.490, p less than 0.05) and inversely to uterine artery blood flow (r = -0.508, p less than 0.05). Placental blood flow is highest during the period of darkness. The flow rates are significantly correlated to intra-amniotic pressure (r = -0.602, p less than 0.05) but not to aortic blood pressure (r = -0.185, p less than 0.05). The data indicate that blood flow distribution in the primate uterus is modulated by factors in addition to physiologic pressure-flow relationships. Extrapolation to the human has potential significance.

Animals↗
PubMed1978

"Lunch syndrome," a bone-scanning artifact: case report.

After a photon-deficient area in the region of the stomach under the ribs on the left side was noted in some bone-scanning patients, a successful attempt was made to produce the artifact by having a cooperative patient eat a large lunch. The comparison of the scans before and after lunch showed the presence of a postprandial artifact in the area in question. It is important not to confuse this artifact with a space-occupying avascular mass in that part of the abdomen.

Adenocarcinoma↗
PubMedDate not supplied

Radiographic examination of the stomach and duodenum: comparison of single-, double- and biphasic-contrast methods.

We compared retrospectively three groups of 150 patients who had undergone radiologic examinations of the stomach and duodenum. Each group was examined with a different barium suspension and radiographic technique: single-contrast (SC), double-contrast (DC), or biphasic-contrast (BC). The radiographs of each study were evaluated for technical quality and visualization of lesions. The number of X-ray exposures, films, and the amount of fluoroscopic time for each study were tabulated. The total radiation dose and cost for each technique were calculated. The BC examinations required the greatest number of radiographic exposures and X-ray films; however, cost was highest for the DC method. Fluoroscopy was significantly longer during the DC procedures, and the total radiation dose was also highest with this technique. Gaseous distention and barium coating of the stomach were equally good for the BC and DC groups, but X-ray penetration of the barium suspension during compression filming was significantly better in the BC and SC groups. Areae gastricae were most frequently seen during the BC studies and artifacts from excess secretions, barium flocculation or gas bubbles were least commonly present using this technique. Significantly more lesions were demonstrated in the stomach with the BC technique than with the other methods; however, the number of lesions found in the duodenum was the same for each technique.

Adult↗
PubMedDate not supplied

Preparation and pharmacokinetics of samarium(III)-153-labeled DTPA-bis-biotin. Characterization and theoretical studies of the samarium(III)-152 conjugate.

The complex(153)Sm(III)DTPA-bis-biotin was prepared with a 99% radiochemical purity and a specific activity of 370 MBq/mg employing a molar ratio of DTPA-bis-biotin/Sm from 2 to 4 at pH 8.0. In vitro studies demonstrated that the complex is stable after dilution in saline and in human serum. Avidity of labeled biotin for avidin was not affected by the labeling procedure. Pharmacokinetic data of (153)Sm(III)DTPA-bis-biotin in normal mice showed that blood clearance is biexponential during the time interval from 0 to 24 h and that 3 h postinjection 92 +/- 4.32% of the dose is eliminated in the urine. To have further evidence which could sustain that (153)Sm(III)DTPA-bis-biotin is stable in solution as a real coordination complex, (152)Sm(III)DTPA-bis-biotin was obtained in macroscopic quantities and its characterization was done by IR, TGA, and conductivity measurements. The results indicated that the complex was chemically pure, where the Sm(3+) ion is neutralized by three carboxylate groups of the DTPA-bis-biotin ligand and coordinated to it. Using the Force Field method followed by ab initio calculations, the DTPA-bis-biotin and the Sm(III)DTPA-bis-biotin molecules were done. Accordingly, the coordination sphere of Sm(III) was totally satisfied with nitrogen and oxygen donors; the best coordination number was 9. The conformation geometry of both compounds is presented.

Analysis of Variance↗