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Biomedical subjects

S Wynchank

Publications and source records attributed to S Wynchank.

At least 55 records · Page 3Linked to original sources
PubMed1988

Computed limitations of spot scanning for therapeutic proton beams.

A calculation depending on the computed fit of a novel mathematical model of the depth dose distribution for a therapeutic proton beam in water and its relevance to a spot scanning system are described. The resulting requirements for lateral and longitudinal precision of the irradiated spots are derived using the standard criterion for allowed dose variation within the tumour volume and the implications of these exacting limits are discussed.

Computer Simulation↗
PubMed1987

Ultrastructural observations on the effects of different substrates on ischaemic contracture in global subtotal ischaemia in the rat heart.

Ultrastructural morphology was examined in myocardia perfused with different substrates, following the hypothesis that ultrastructural changes or differences would indicate the mechanism of early ischaemic contracture. Substrates used were glucose, acetate and no substrate (substrate-free). Isolated rat hearts were subjected to global low flow ischaemia followed by perfusion fixation at either no contracture, early contracture (5%) or full contracture (100%). Total tissue adenosine triphosphate (ATP) levels were analysed from myocardia of each group. Glucose perfused myocardia did not develop contracture for at least 30 minutes and maintained ultrastructural and ATP normality. Substrate-free and acetate perfused myocardia developed contracture after 10-12 minutes of ischaemia at which time myofibrillar morphology was altered within small sparse foci of developing mild oedema with contracture and hyperextension of myofibrils. ATP levels were normal. At full ischaemic contracture, both substrate-free and acetate perfused myocardia showed severe mitochondrial damage, oedema, myofibrillar contracture and hyperextension with accompanying distortion and swelling of the sarcoplasmic reticulum.

Animals↗
PubMed1987

The Proteus syndrome: the magnetic resonance and radiological features.

The Proteus syndrome is a recently delineated group of skeletal and mesodermal malformations. Its characteristics include hemihypertrophy and fatty/lymphangiomatous masses. This description outlines the imaging sequences available to the radiologist. It is mainly concerned with the use of magnetic resonance imaging. This shows the extent of the mesodermal malformation with particular reference to the extent of intra abdominal infiltration.

Child, Preschool↗
PubMed1985

Visualisation of a thyroglossal duct.

After ablation of an autonomously functioning thyroid nodule resulting from an adenoma, a previously suppressed scintigraphic image of a thyroglossal duct was visualised.

Adenoma↗
PubMed1984

Routine studies of swallowed radionuclide transit in paediatrics: experience with 400 patients.

Scintigraphic studies of swallowed 99m Tc-sulphur colloid mixed with a few millilitres of liquid, performed on 400 paediatric patients of all ages, allowed visualisation of foregut function and measurement of oesophageal transit time and gastric emptying proportions. This non-invasive and physiological procedure requires a standard gamma camera with computing facilities and was performed as an outpatient routine. It proved very effective for the detection of gastro-oesophageal reflux and aspiration of refluxed liquid in patients of all ages but especially in neonates. The relevance of these scintigraphic results to oesophagitis, repeated respiratory problems, cyanotic and apnoeic spells and alternative methods of investigation is described.

Apnea↗
PubMed1984

Biliary atresia and neonatal hepatobiliary scintigraphy.

Hepatobiliary scintigraphy using Tc-99m diethyl IDA was performed on 14 jaundiced neonates. It aided greatly the differential diagnosis between neonatal hepatitis and biliary atresia. Limitations in the interpretation of the results are described, as neonatal hepatitis may be accompanied by biliary excretion ranging from zero to normal. Also both biliary atresia (intra- and extrahepatic) and neonatal hepatitis may show no biliary excretion within 24 hours.

Bile Ducts↗
PubMed1984

Radionuclide angiocardiography in the diagnosis of congenitally corrected transposition of the great arteries.

Congenitally corrected transposition of the great arteries (CTGA) may constitute a pitfall for interpretation of radionuclide angiocardiography, since the two anatomic discordances cancel each other from a physiologic point of view. However, the unusual shape of the ventricles (due to ventricular discordance) and the relative position of the great arteries (due to transposition) can allow a clear scintigraphic diagnosis, especially for CTGA with mild or absent associated congenital anomalies. Five cases are described. Gated cardiac blood pool imaging is particularly helpful since it permits multiple views, allowing a more detailed study of the scintigraphic signs.

Adolescent↗
PubMed1984

Fetal responses to vibrotactile stimulation, a possible predictor of fetal and neonatal outcome.

This study measured the antenatal fetal heart rate changes in response to a single vibrotactile stimulus. In a group of 11 normal patients, this resulted in a significant change in the fetal heart rate (P less than 0.001). Sixty-eight high risk patients were also tested. In the group of 25 patients whose fetuses showed no response to the stimulus, there were 4 stillbirths and 4 neonatal deaths; 23 of these 25 infants were small for gestational age (SGA) compared to only 15 of the 43 that showed a response to the stimulus. Fetal habituation to a repeated vibrotactile stimulus was measured in a control group of 40 patients who had a normal antepartum and intrapartum course and delivered infants in an optimal condition. The same was done in a study group of 48 patients who delivered infants that were SGA. These infants were assessed at 1 year of age by the Griffiths Mental Developmental Scale (GMDS). Infants that were SGA did not differ significantly from the control group. However, infants who had a normal antenatal habituation pattern had a significantly better performance (P less than 0.01) compared to infants who had an abnormal antenatal habituation pattern.

Electrocardiography↗
PubMed1984

Single photon emission computed tomography (SPECT), planar scintigraphy, and transmission computed tomography: a comparison of accuracy in diagnosing focal hepatic disease.

A prospective evaluation of conventional planar scintigraphy (PS), single photon emission computed tomography (SPECT), and transmission computed tomography (TCT) was performed in 98 patients with suspected focal hepatic disease (FHD). The three examinations were performed on the same day. TCT had slightly higher sensitivity (91%) and specificity (96%) than either PS or SPECT. The sensitivity and specificity of TCT was also higher than that of the combination of PS and SPECT, which was more accurate than either radionuclide technique alone, with a sensitivity of 85-87% and a specificity of 90%. These differences were not statistically significant. However, receiver operating characteristic (ROC) analysis showed that the performance of TCT was significantly better. The ROC curves also showed, without statistical significance, that SPECT appears to have better diagnostic accuracy than PS and that it seems desirable to complement SPECT imaging with PS views, to reduce the number of equivocal results.

Adult↗
PubMed1984

Radionuclide studies in postoperative evaluation of the Fontan procedure.

Radionuclide studies were performed on 12 patients who had had a Fontan operation for cyanotic congenital heart disease, six of whom had undergone a prior palliative Glenn procedure. The patients without prior Glenn anastomoses were studied by radionuclide first-pass angiocardiography, using a right antecubital vein injection of 99mTc pertechnetate. The patients with Glenn anastomoses required two injections, one by femoral vein to study the Fontan procedure, using bolus injection of 99mTc pertechnetate or microspheres, and the second by right antecubital vein to study the Glenn anastomosis and right lung, using a bolus of microspheres. Gated cardiac blood-pool scintigraphy was used to measure right atrial and left ventricular ejection fraction in three patients. In nine patients, contrast angiography confirmed that these techniques allowed recognition of residual right-to-left shunts, right atrial stasis, right atrial outflow obstructions, left ventricular dysfunction, and right lung arteriovenous fistulas. Noninvasive radionuclide methods seem to be dependable in the postoperative evaluation of patients after the Fontan procedure. First-pass angiocardiography is most helpful in evaluating the dynamics and distribution of blood flow, especially the right atrial output, and gated blood-pool scintigraphy offers a better evaluation of right atrial and left ventricular contraction, so both supply complementary information.

Adolescent↗
PubMed1984

Quantitative analysis of left-ventricular function using gated single photon emission tomography.

We describe a quantitative method that measures segmental motion of the left ventricle, using tomographic slices obtained by gated single photon emission tomography (GSPECT). These slices contain the major axis of the left ventricle and are presumed to show wall motion directed towards a center of contraction. Values of parameters describing segmental wall motion in GSPECT were obtained from 61 patients, who received a left cardiac catheterization 1 hr later. These values were compared with results of similar calculations applied to data from contrast ventriculography. We conclude that GSPECT allows a detailed and quantitative, noninvasive study of wall motion of all left ventricular segments, with high inter- and intraobserver reproducibility.

Angiocardiography↗