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Biomedical subjects

D J Dowsett

Publications and source records attributed to D J Dowsett.

18 recordsLinked to original sources
PubMed1994

Renal haemodynamics and prostaglandin synthesis in partial unilateral ureteric obstruction.

Haemodynamic changes in partial unilateral ureteric obstruction (PUUO) may be related to altered prostaglandin synthesis. In 12 dogs the left ureter was partially obstructed for 5 weeks. In six dogs the ureter was reimplanted into the bladder and to investigate the effect of this procedure on the contralateral side the other six animals underwent ipsilateral nephroureterectomy. Renal blood flow (RBF) was measured by the distribution of radiolabelled microspheres. Changes in urinary prostaglandin (PG) concentrations were validated by renin activity using angiotensin I. Reduced left RBF during obstruction was associated with increased thromboxane A2 synthesis (P < 0.01). Increased RBF to the non-obstructed side was associated with elevated PGE2 formation (P < 0.05). Elevated angiotensin I levels (P < 0.01) corresponded to maximal increases in PG synthesis. Reimplantation of the obstructed kidney did not exert a direct effect on contralateral RBF or PG concentration. Haemodynamic changes in PUUO in vivo are associated with alterations in renal PGs.

Angiotensin I↗
PubMed1992

Assessment of mammographic film processor performance in a hospital and mobile screening unit.

In contrast to the majority of mammographic breast screening programmes, film processing at this centre occurs on site in both hospital and mobile trailer units. Initial (1989) quality control (QC) sensitometric tests revealed a large variation in film processor performance in the mobile unit. The clinical significance of these variations was assessed and acceptance limits for processor performance determined. Abnormal mammograms were used as reference material and copied using high definition 35 mm film over a range of exposure settings. The copies were than matched with QC film density variation from the mobile unit. All films were subsequently ranked for spatial and contrast resolution. Optimal values for processing time of 2 min (equivalent to film transit time 3 min and developer time 46 s) and temperature of 36 degrees C were obtained. The widespread anomaly of reporting film transit time as processing time is highlighted. Use of mammogram copies as a means of measuring the influence of film processor variation is advocated. Careful monitoring of the mobile unit film processor performance has produced stable quality comparable with the hospital based unit. The advantages of on site film processing are outlined. The addition of a sensitometric step wedge to all mammography film stock as a means of assessing image quality is recommended.

Breast Neoplasms↗
PubMed1990

Peripheral arteriovenous malformation: diagnosis and localization by intraarterial injection of technetium-99m-MAA.

Radionuclide angiography with technetium-99m-labeled macroaggregates of albumin (99mTc-MAA), was successful in a single patient with a lower limb arteriovenous (AV) malformation, not only in diagnosis and quantitation of AV shunting, but also in localizing the site of shunting. This information proved useful to the angiographer, permitting a carefully tailored examination of the area of interest. This technique may hold promise as a preliminary examination in patients with limb AV malformations prior to angiography.

Adult↗
PubMed1985

Gold-195m: a steady-state imaging agent for venography that gives blood velocity measurement.

Gold-195m has found applications in first-pass studies for investigating both right and left ventricular activity as well as lung transit. Owing to its reasonably short half-life of 30 sec we have found it particularly useful for imaging leg veins up to and including the inferior vena cava. Its short half-life prevents recirculation activity from appearing, so continuous perfusion into a superficial foot vein and application of ankle tourniquets yield a steady-state image of the deep veins, with particularly good resolution. Its decay pattern along a vessel is very sensitive to blood velocity, so measurement of activity at various points on a vein in a computer static image can give velocity values that reveal abnormalities due to partial or complete thrombosis. The radiation dosimetry of 195mAu used in this way is lower than contrast and technetium-99m macroaggregated albumin [( 99mTc]MAA) venography, making it particularly useful for investigating deep vein thrombosis (DVT) in pregnancy.

Abdomen↗
PubMed1978

Femoral head activity in Perthes' disease: clinical evaluation of a quantitative technique for estimating tracer uptake.

A method for quantifying the uptake of Tc-99m-labeled phosphate complexes in the femoral head has been clinically evaluated, being used specifically for studying the uptake of these bone-seeking agents in Perthes' disease. The analysis depends on the selection, by computer program, of a reliable reference area in the femoral shaft, which is then compared with the mean uptake from each femoral head. The femoral-head activity is then represented as an uptake ratio. These ratios, together with a fixed contour representing the uptake in the femoral-head regions, provide more clinical information than the radiograph or scintiphoto, particularly in the early stages of unilateral or bilateral femoral-head disease and during followup. No correlation has been found between these ratios and qualitative techniques for assessing Perthes' disease by radiograph. From the quantitative data so far obtained it is clear that osteotomy reduces the vascularity of the femoral head, and in certain cases this reduction persists for some years. Tc-99m-labeled diphosphonate compounds were used in more recent studies, and a significant increase in sensitivity was obtained, compared with earlier polyphosphate data.

Child↗
PubMed1976

A quantitative assessment of femoral head activity using 99Tcm -polyphosphate and a computer data collection system.

Abnormal femoral head activity in Legg-Calve-Perthes' disease has been measured using 99Tcm -polyphosphate and a gamma camera/computer data collection system. A reference point on the data matrix, which is unaffected by the diease, is used for deriving comparative uptake ratios in each femoral head. The reference point remains unaltered after surgical procedures or short intervals between follow-up studies. Early abnormality can be measured in both unilateral and bilateral femoral head pathology.

Child↗