Search PubMed⌕ Search

Biomedical subjects

B Shuter

Publications and source records attributed to B Shuter.

16 recordsLinked to original sources
PubMed1996

The relaxivity of Gd-EOB-DTPA and Gd-DTPA in liver and kidney of the Wistar rat.

The NMR relaxivities of Gd-EOB-DTPA and Gd-DTPA were determined in the kidney and liver of intact male Wistar rats immediately following sacrifice and in vitro in solutions and gels, at 1.5 T using a clinical MR scanner, T1 and T2 values of tissue samples were derived from spin-echo image sequences. Tissue gadolinium concentrations were determined by radioassay of Gd153, Gd-EOB-DTPA T1 and T2 relaxivities, R1 and R2 (s-1 mmole-1 kg), were found to be 10.7 +/- 0.5 and 22.5 +/- 3.2 respectively, for liver, 2.4 +/- 0.2 and 12.1 +/- 1.7 for kidney cortex, 2.7 +/- 0.2 and 14.5 +/- 1.9 for kidney outer medulla, 2.0 +/- 0.2 and 11.4 +/- 2.1 for kidney inner medulla. Gd-DTPA R1 and R2 were found to be 4.8 +/- 0.4 and 14.5 +/- 3.7 for liver, 1.2 +/- 0.1 and 7.9 +/- 0.8 for kidney cortex, 1.6 +/- 0.1 and 10.2 +/- 1.4 for kidney outer medulla, 1.3 +/- 0.1 and 10.2 +/- 1.2 for kidney inner medulla. Gd-EOB-DTPA and Gd-DTPA R1 was increased in liver compared to agarose gets at 38 degrees C (4.49 +/- 0.03 and 3.47 +/- 0.06), but reduced in kidney tissues. All R2 were elevated compared to agarose gels at 38 degrees C (5.72 +/- 0.12 and 4.12 +/- 0.03). Elevated R2 and R1 (expressed in terms of the concentration of gadolinium per kg of tissue) can be accounted for in part by the lower water content of tissues compared with gels or solutions increased microviscosity and binding to macromolecules. In addition, susceptibility effects may give rise to further increases in R2. By contrast, the reduced R1 observed in kidney may be the result of compartmentalization of the magnetopharmaceuticals. Statistically improved fits were obtained for T1 recovery curves for liver in the presence of Gd-EOB-DTPA when a dual exponential model was used. Assuming in vitro values for the relaxivities of these artificial contrast agents will lead to inaccuracies when relating observed signal enhancement factors to tissue gadolinium concentration.

Animals↗
PubMed1995

The effect of sacrifice on image signal, T1, T2, and T*2 in liver, kidney, and brain of the Wistar rat.

Signal intensity in SE240/25 and GE240/25 images, T*2, T2, and T1 were measured prior to and after sacrifice at 1.5 T in liver, kidney, and brain of Wistar rats. Presacrifice, animals were maintained on 2-3% halothane, ensuring a high saturation of venous haemoglobin with oxygen, which emphasised blood oxygenation level dependent (BOLD) effects upon deoxygenation of haemoglobin postsacrifice. T*2 values (in ms) changed on sacrifice from 27.8 +/- 4.1 to 15.0 +/- 1.1 in liver (p << .001), from 57.4 +/- 6.5 to 52.8 +/- 5.7 in brain (p < .02), and from 52.3 +/- 10.3 to 37.6 +/- 11.9 in kidney cortex (p < .01). T*2 was also reduced in kidney medulla and papilla. T2 reduced on sacrifice (by a lesser amount than T*2), except in brain, which showed a small increase. T1 (ms) changed only in liver, showing a significant increase from 670 +/- 31 to 834 +/- 69 (p << .001). The ratio of signal postsacrifice to presacrifice was lowest in the SE240/25 and GE240/25 images of liver (0.73 +/- 0.03 and 0.52 +/- 0.05, respectively), but increased T1 may account for some of these changes. Expected signal ratios at sacrifice calculated from measured relaxation times agreed well with those observed experimentally. Relaxation changes observed on sacrifice were consistent with deoxygenation of haemoglobin. These results give an estimate of the maximum effects which changes of blood oxygen level might produce at 1.5 T and suggest that contrast due to variation of endogenous deoxyhaemoglobin may be exploitable in the liver.

Animals↗
PubMed1995

Efficacy of cisapride therapy in functional dyspepsia.

AIM: To assess the efficacy of cisapride therapy in relieving symptoms of functional dyspepsia. METHODS: After a 2-week placebo run-in period, 61 out of 74 patients were eligible to enter a 4-week double-blind treatment phase, consisting of treatment with cisapride (10 mg) or placebo tablets t.d.s. Gastric emptying was assessed scintigraphically at entry to the study. Patients were stratified before treatment into those with or without active chronic (Helicobacter pylori) gastritis. Patients were also classified retrospectively into those with 'reflux-like' dyspepsia (n = 29) and those with 'motility-like' dyspepsia (n = 32). RESULTS: At the end of the active treatment phase, there was a similar significant (P < 0.001) reduction in total symptom score from baseline in both cisapride (8.9 +/- 0.5 to 5.8 +/- 0.6) and placebo (9.7 +/- 0.6 to 5.5 +/- 0.6) groups. Scores for heartburn and continual bloating were significantly reduced in the cisapride but not the placebo group; improvement was attributable to patients with normal, rather than delayed, rates of gastric emptying. For continual bloating, significant improvement also occurred in the cisapride subgroup without gastritis, but not in the subgroup with gastritis (mean symptom score reduction 0.48 +/- 0.18, P = 0.03). For global evaluation by the investigator and by the patient, the overall improvement rates were not statistically different between cisapride and placebo groups. In those with normal gastric emptying, however, there was a significant (P = 0.01) improvement in general well-being in the cisapride but not in the placebo group. CONCLUSIONS: We were unable to show major differences in the short-term efficacy of cisapride and placebo in functional dyspepsia. There were indications, however, of beneficial effects of cisapride over placebo in those with 'reflux-like' dyspepsia, and in those without gastroparesis.

Adult↗
PubMed1993

Intragastric distribution and gastric emptying of solids and liquids in functional dyspepsia. Lack of influence of symptom subgroups and H. pylori-associated gastritis.

The relative contributions of altered gastric motor function and Helicobacter pylori-associated active chronic gastritis to the pathogenesis of functional dyspepsia are controversial. We therefore evaluated scintigraphically the intragastric distribution and gastric emptying of a mixed solid-liquid meal in 75 patients with functional dyspepsia; patients were subdivided on the basis of both specific symptom clusters and the presence or absence of H. pylori gastritis. Twenty-one (28%) patients displayed abnormal solid and/or liquid gastric emptying, with prolonged solid lag time the most prominent alteration detected. The number of patients with abnormal scintigraphic patterns increased to 36 (48%) when intragastric distribution parameters (fundal half-emptying time and antral maximal fraction) were examined. Although patients with reflux-like dyspepsia (N = 36) demonstrated significantly slower rates of liquid emptying at 45 and 70 min and a higher prevalence of abnormal liquid intragastric distribution when compared to patients with motility-like dyspepsia (N = 39) or to controls (N = 34), the absolute differences were small and unlikely to be of clinical significance. Patients without H. pylori gastritis (N = 50) demonstrated a significantly more prolonged solid lag time when compared to those with H. pylori gastritis (N = 25), but the difference was small and there were no other differences between these two subgroups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of cigarette smoking on solid and liquid intragastric distribution and gastric emptying.

BACKGROUND: The acute effects of cigarette smoking on gastric emptying are controversial, whereas its effects on the intragastric distribution of solids and liquids are not established. METHODS: Dual isotope gastric scintigraphy was performed in 15 habitual smokers (studied twice, either sham smoking or actively smoking) and in 15 age- and sex-matched nonsmokers. RESULTS: Acute smoking was associated with an increased prevalence of episodes of retrograde intragastric movement of solids (3 of 15 sham subjects vs. 12 of 15 actively smoking subjects; P < 0.01) and of liquids (0 of 15 vs. 7 of 15; P < 0.01) from distal to proximal stomach. Fundal half-emptying time (T1/2) for liquids was also prolonged by smoking (43 +/- 19 minutes sham vs. 125 +/- 216 minutes active; P < 0.05). Acute smoking delayed solid lag time (13 +/- 6 minutes sham vs. 32 +/- 18 active; P < 0.05) and liquid T1/2 (46 +/- 21 vs. 90 +/- 50 minutes; P < 0.05). In the nonsmokers, such episodes of proximal intragastric redistribution did not occur, and intragastric and overall emptying parameters did not differ significantly from those of habitual sham smokers. CONCLUSIONS: Acute cigarette smoking produces excessive antrofundal redistribution of both solid and liquid contents and delays solid and liquid gastric emptying.

Adult↗
PubMed1993

Ni-DTPA doped agarose gel--a phantom material for Gd-DTPA enhancement measurements.

In order to study the relationship between the concentration of Gd-DTPA in tissue, and the resulting changes in relaxation times and signal intensity, a phantom material that has similar relaxation times to tissue and that can be doped with Gd-DTPA is required. The "tissue-equivalent" material should not contain Gd; nor should it alter the relaxivities of Gd-DTPA from their values in aqueous solution (R1 = 4.5 sec-1 mM-1; R2 = 5.5 sec-1 mM-1 at 1.5 T). Conventional materials, based on CuSO4-, MnCl2-, or GdCl3/LaCl3-agarose mixtures, are not suitable, since Gd is displaced from the Gd-DTPA chelate. The new material, consisting of Ni-DTPA dissolved in agarose, is easy to prepare and does not interact with Gd-DTPA. Its relaxation times are stable; relaxivity R1 was within 4% of its aqueous value over 109 days. T1s have low dependence on temperature (0.2-1.0%/degrees C at 21 degrees C) and on field strength, allowing the material to be used as a relaxation time standard for quality assurance. Equations giving the concentration of Ni-DTPA and agarose to produce a required T1 and T2 are provided.

Contrast Media↗
PubMed1992

Suppression of anger and gastric emptying in patients with functional dyspepsia.

Psychologic distress and gastric motor dysfunction have both been implicated in the pathogenesis of functional (non-ulcer) dyspepsia (FD). This study assesses the association between psychologic factors and gastric emptying in 28 FD patients. Subjects completed an extensive range of psychologic questionnaires and underwent dual-isotope scintigraphic assessment of solid and liquid gastric emptying. Attempts to resist, control, suppress, and hold in anger, to adopt a fighting spirit whilst dealing with chronic stressors, and manifest unhappiness were predictors of prolonged gastric emptying. These findings suggest that psychologic factors may be important in the aetiology of gastric stasis and subsequent upper gastrointestinal symptoms in patients with functional dyspepsia.

Adaptation, Psychological↗
PubMed1991

Computer generation of random deviates.

The need for random deviates arises in many scientific applications, such as the simulation of physical processes, numerical evaluation of complex mathematical formulae and the modeling of decision processes. In medical physics, Monte Carlo simulations have been used in radiology, radiation therapy and nuclear medicine. Specific instances include the modelling of x-ray scattering processes and the addition of random noise to images or curves in order to assess the effects of various processing procedures. Reliable sources of random deviates with statistical properties indistinguishable from true random deviates are a fundamental necessity for such tasks. This paper provides a review of computer algorithms which can be used to generate uniform random deviates and other distributions of interest to medical physicists, along with a few caveats relating to various problems and pitfalls which can occur. Source code listings for the generators discussed (in FORTRAN, Turbo-PASCAL and Data General ASSEMBLER) are available on request from the authors.

Algorithms↗
PubMed1989

Lack of association between gastric emptying of solids and symptoms in nonulcer dyspepsia.

Gastric motor dysfunction and concomitant gastric stasis have been implicated in the pathogenesis of nonulcer dyspepsia, but a cause-and-effect relationship is not established. Essential dyspepsia refers to a subgroup of nonulcer dyspepsia patients who have no evidence of irritable bowel syndrome, gastroesophageal reflux, or pancreaticobiliary disease. In 32 patients with essential dyspepsia, and 32 randomly selected dyspepsia-free community controls of similar age and sex, we measured gastric emptying of solids using Tc99m-Sulphur Colloid in a fried egg sandwich. Subjects with neuromuscular or other diseases that may alter gastric emptying were excluded. Symptoms were assessed by a standard questionnaire. Data processing was carried out "blinded" to the subjects' clinical status. Female patients took significantly longer to empty half the initial stomach activity (mean 90 min) than female controls (mean, 73 min; p = 0.02). The rate of emptying at 25 min was also significantly less in female patients than in controls. Female and male controls, and male patients, had similar emptying times. Delayed emptying was not associated with the occurrence of postprandial pain, belching, or nausea; there was a trend for the half-time rate of emptying to be greater in patients with abdominal distention. While gastric emptying of solids is slightly delayed in females with essential dyspepsia as a group, this may not explain their symptoms.

Dyspepsia↗
PubMed1983

Reduced pregnancy rates in AID women with unsuspected ovulatory failure.

A review over five years of 232 patients attending an artificial insemination by donor (AID) clinic was undertaken in order to detect abnormalities in ovulation patterns. Ovulation was determined by luteal phase progesterone estimations. Unexpected anovulation was found in 36% of the patients attending despite an apparently normal previous menstrual history and investigations. This group consisted of 22% who were anovulatory from commencement in the programme and 14% who became anovulatory during treatment. The cumulative pregnancy rates at 15 months for these two groups were lower (73% and 55%) than that for the remaining patients who ovulated normally (90%). A proportion (16%) of the latter group were receiving clomiphene therapy for anovulation recognized before entering the programme. The lower pregnancy rate could not be related to other factors influencing conception and occurred in spite of clomiphene therapy. These results should assist in advising patients on their chances of conception, preventing early discouragement but not encouraging long term insemination which may not improve the pregnancy rate.

Anovulation↗
PubMed1982

The value of ultrasound, gonadotropin, and estradiol measurements for precise ovulation prediction.

The exact prediction of ovulation is becoming more important in the management of infertile women. Graafian follicle diameter, measured by ultrasound and plasma follicle-stimulating hormone, luteinizing hormone, and estradiol levels were compared retrospectively as predictors of ovulation in 14 normal women in whom ovulation was dated by conventional ultrasound techniques. Follicle diameter was found to be a better predictor of the anticipated time of ovulation than endocrine estimations for short-term as well as long-term predictions in normal women. The relationship between follicle diameter and plasma estradiol for each day before ovulation was linear but contained a great amount of scatter, suggesting that the assessment of normality of follicular development in infertile women may not be possible with the use of these parameters.

Estradiol↗
PubMed1978

Comparative studies on two combination oral contraceptives, one containing synthetic estrogen, the other "natural" estrogens.

Two combined oral contraceptives, one containing ethinyl estradiol and the other micronized estradiol and estriol, were compared by measuring a variety of endocrine and renal parameters over nine months. Significant changes were observed in plasma renin activity (P.R.A.) on the synthetic estrogen. Much larger changes were observed in the total urinary estrogens on patients taking the "natural" estrogens reflecting the amount of estrogens required to be excreted in the urine.

Adult↗