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D J Mott

Publications and source records attributed to D J Mott.

11 recordsLinked to original sources
PubMed1997

Estimation of fetal and effective dose for CT examinations.

Doses from CT examinations are difficult to estimate. However, they are requested more frequently due to the increase in CT examinations. In particular, fetal dose estimations are frequently required for patients who have discovered, subsequent to the examination, that they were pregnant when the examination was conducted. A computer model has been developed to facilitate such dose calculations. This model combines empirical beam data with anatomical information. The model has been verified using thermoluminescent dosemeter (TLD) readings of internal and surface dose from both phantoms and patients, including intrauterine doses for patients undergoing afterloading gynaecological intracavitary treatment. Although only limited experimental data were available, the results indicate that the model accurately predicts uterine doses within acceptable errors. This approach has been validated for fetal dose estimation. The model was also used in a comparison with the nationally available CT dose data from the National Radiological Protection Board (NRPB). The two models were found to be in agreement for fetal dose estimations.

Computer Simulation↗
PubMed1994

Technical note: measurement of computed tomography scanner slice widths.

The slice width of a computed tomography scanner can be considered as the full width at half maximum (FWHM) of the slice dose profile. A method is described which uses dental film to image the slice and allows the FWHM of the dose profile to be determine directly from the digitization and analysis of the film image.

Humans↗
PubMed1985

The removal of a "cupping" artefact from brain images produced by the EMI 7070 CT scanner.

Brain images produced on the EMI 7070 scanner exhibit a "cupping" artefact due to a combination of beam hardening and scatter effects. The magnitude of the artefact is assessed by statistically analysing a series of concentric regions of interest in the final image. Once the magnitude has been determined it can be subtracted from the image. While the result of the technique does not modify the clinical analysis of images it does increase the observer's appreciation of the image. Both the technique and clinical results are presented, and the implications of this type of reconstruction artefact removal discussed.

Brain↗
PubMed1984

Kinetic characteristics of beta-carotene uptake and depletion in rat tissue.

Rats were fed a semi-purified diet supplemented with 0, 0.002, 0.02 and 0.2% beta-carotene (BC) for 21 weeks, followed by a 5-week depletion period. At various time points liver, adrenal, ovary, lung, heart, kidney, plasma, skin, brain and muscle were analyzed for BC content. The results indicated a dose-response effect between ingested BC and BC tissue content. The tissue saturation levels of BC, and time to reach saturation were determined in animals fed 0.2% BC diets. The half-life for BC was also determined. There was no apparent relationship among tissue content, rate of uptake and rate of depletion of BC. Each tissue studied was different. The absence of BC in fat suggests to us that BC distribution is not simply a matter of deposition into lipid depots. There was a wide range in tissue levels of BC; liver had the greatest value with 50 micrograms/g tissue, and muscle had the lowest value with 0.03 micrograms/g tissue. Plasma was saturated within 3 days, whereas liver, adrenal and ovary had not yet reached saturation at 147 days. The half-life varied from less than 3 days for plasma to 18 days for muscle.

Adrenal Glands↗
PubMed1983

Enhancement of computed tomographic scanner based digital radiographic images.

Scanned digital radiographs are one of the imaging facilities available on the EMI 7070 scanner. The images offered by the system were found to be clinically poor and the reason for this was that the round shape of the patient was forming the major component of the image. Two empirical methods to account effectively for patient shape have been investigated and are now in clinical use. The first method assumes that the patient shape is approximated to a second-order polynomial of the picture element position. For each line of the image a second-order polynomial function is fitted to the image data, then removed from the image data. The second method involves using the existing CT wedge as an average compensation wedge to remove the majority of the effect of the patient shape. The relative merits and clinical application of both techniques are discussed.

Humans↗
PubMed1981

Modulation of glycosaminoglycan biosynthesis by retinoids.

In conclusion, retinoids modulate phenotypic changes such as morphology, adhesion, and growth rate. These changes also result in specific alterations of glycosaminoglycans. We have observed increases in the degree of sulfation in fibroblast matrix heparan sulfate and, a change in the ratio of sulfamido to ester sulfate in matrix heparan sulfate in 407 cell surface. Matrix glycosaminoglycans have been functionally implicated in cellular interactions, and have a specific role in adhesion and growth rates. Our results are consistent with the proposed role for heparan sulfate. It is possible that some of the modulation in cellular behavior resulting from retinoid treatment may be mediated by cell surface and cellular changes in heparan sulfate and other glycosaminoglycans.

Acitretin↗