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Biomedical subjects

A S Houston

Publications and source records attributed to A S Houston.

47 records · Page 3Linked to original sources
PubMed1977

Urinary clearance of 113m In-DTPA and 99mTc-(Sn)DTPA measured by external arm counting.

Single shot glomerular filtration rate measurements involving chelates (113mIn-DTPA, 99mTc-DTPA etc) assume direct loss from the plasma to urine via glomerular filtration and excretion. Inherent errors, due to considerable uptake of activity in tissue and uncertainty of complete bladder emptying are ignored and taking of half-hourly blood and urine samples involves patient discomfort. This paper describes a simple method of measuring urinary clearance of chelates using serial external arm counting which entails only an initial injection and takes into account tissue loss from plasma. The resultant plotted curve exhibits three phases, the first two depicting input and equilibration between plasma and tissue and the third and exponential part, which is a measure of the biological half-life of the chelate, being representative of the efficiency of renal glomerular filtration, the parameter to be measured. Results obtained, compared with single shot glomerular filtration rate measurements performed simultaneously, gave better correlation with clinical data including renography.

Glomerular Filtration Rate↗
PubMedDate not supplied

CA549 and TPS patterns in the diagnosis and staging of patients with breast carcinoma.

This study compares the clinical value of the breast cancer tumour makers CA549 and TPS, and their tandem use when one or both markers indicate abnormality. For 144 patients presenting with active disease, 33 were classified as Stage I, 37 as Stage II, 40 as Stage III and 34 as Stage IV. For these patients the sensitivity of CA549 using a cut-off of 10 U/ml was 27%, 32%, 42% and 79%, respectively. The sensitivity of TPS for each stage using a cut-off of 100 U/l was 12%, 22%, 28% and 73%, respectively. At these cut-off levels, 36%, 46%, 63% and 91% of patients, respectively, have either CA549 or TPS or both markers raised. For 161 patients with diagnosed benign breast disease, the specificity of marker levels was 96% for CA549, 88% for TPS and 84% for tandem use. CA549 is shown to be superior to TPS and this was confirmed by Receiver Operating Characteristic (ROC) analysis using variable threshold levels, with the areas under the curves for all stages combined being 0.74 +/- 0.03 (ISD) and 0.66 +/- 0.03, respectively. The corresponding area under the curve for tandem use (0.75 +/- 0.03) is marginally greater than for either individual marker, although the difference with respect to CA549 is statistically insignificant.

Adult↗
PubMedDate not supplied

The role of expert system shell induction in the analysis of phase and amplitude images obtained from nuclear cardiology.

In an attempt to explain the results of a perception experiment, estimates of statistical parameters were obtained from phase and amplitude images of nuclear medicine multiple-gated cardiac studies. A commercially available induction system was used to create a rule-based decision tree using these estimates as a training set. In the classification of normal and abnormal studies two useful rules were found; one of these involved the standard deviation of the left ventricular phase histogram and the other concerned the correlation of adjacent pixels in the left ventricular region of the amplitude image. A discriminant analysis performed on five amplitude and five phase parameters produced no better discrimination than the use of the phase standard deviation alone. Although it was hoped that induction would find more than two useful rules, the results of the discriminant analysis confirm that induction has performed creditably on a difficult problem.

Algorithms↗
PubMedDate not supplied

Computer aided test selection (CATS) for nuclear medicine--a prototype system for renal investigations.

An expert system for renal test selection in nuclear medicine has been developed as the first stage of a collaborative project on test selection in nuclear medicine. The stages of knowledge elicitation and knowledge representation were addressed by means of a questionnaire which was completed by five experts in the field of renal nuclear medicine. A flow chart was developed from the responses and implemented using a commercially available expert system shell (Crystal 4.5). A menu specifying clinical problems, for which renal nuclear medicine is useful, is displayed to the user who is prompted for a choice. Specific aspects of the chosen problem are then shown and again a choice is requested. Selected tests, in order of expert preference, are displayed and further information on any of these is available, if required, on selection from a menu subdivided into categories such as patient preparation, preliminary investigations, etc. The system provides cross-referencing to other areas of investigation and is currently being evaluated using a structured approach commonly employed in the assessment of user interfaces.

Decision Making, Computer-Assisted↗
PubMedDate not supplied

Case control study of cerebral perfusion deficits in divers using 99Tcm hexamethylpropylene amine oxime.

In a preliminary report, Adkisson et al. (Lancet 1989; 2:119-121) used 99Tcm-hexamethylpropylene amine oxime (HMPAO) single photon emission computed tomography (SPECT) to provide evidence for cerebral perfusion deficits in 28 cases of dysbarism. The report caused concern because these deficits were found even in cases in which the clinical manifestations were limited to the spinal cord. To address this issue further, a case-control study of cerebral perfusion using 99Tcm-HMPAO SPECT is reported. Four groups of 10 subjects were studied: a) divers scanned on average 11 days after treatment of neurologic decompression illness, b) divers scanned 3-5 yr after treatment for neurologic decompression illness, c) diver controls, and d) population controls. All groups were matched for age, and the divers were further matched for general diving experience. The scans were randomized and reported blind to history. Despite a trend toward larger numbers of deficits in individuals with decompression illness, the 4 groups were statistically indistinguishable. Furthermore, no correlation was found between the location of the perfusion deficits and the clinical presentation. These results indicate that 99Tcm-HMPAO SPECT scanning requires further evaluation before clinical significance can be ascribed to perfusion deficits found in divers.

Adult↗