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Biomedical subjects

Peter Dawson

Publications and source records attributed to Peter Dawson.

8 recordsLinked to original sources
PubMed2002

The value of mathematical modelling in understanding contrast enhancement in CT with particular reference to the detection of hypovascular liver metastases.

OBJECTIVE: Few subjects in body imaging have generated such intensive debate as that surrounding the optimising of strategies for the detection of liver metastases using contrast-enhanced Computed Tomography (CT). Despite this, research on the subject has been almost entirely focused on experimental studies, little attention having been paid to the value of theoretical analyses. The authors' aim was to develop a relatively simple and robust mathematical model which could be implemented on a personal computer. METHODS: Simple differential equations describing the distribution of contrast agent between intra- and extra-vascular spaces during an infusion are set up. An analytic solution is obtained for the plasma/blood concentrations as a fraction of time and a solution for the interstitial concentrations as a fraction of time is obtained by converting the differential equations to difference equations which are solved in a stepwise manner. RESULTS: Vascular and hepatic parenchymal enhancement-time curves are generated which are in close agreement with expectations. The model may be used to compare different infusion regimes, e.g. lower versus higher dose, faster versus slower infusions, monophasic versus biphasic infusions and scan start delay. The implications of the results of the model for clinical protocol design are discussed and the special value of spiral/helical technology indicated. CONCLUSION: A simple mathematical model has been developed to model blood and tissue contrast enhancement in CT during contrast infusion. The model clarifies a number of issues related to contrast enhancement regimes for the study of the liver and these have been discussed.

Contrast Media↗
PubMed2002

Barriers to safer sex practices among African American college students.

African American college students are among the age group of African Americans with significantly higher heterosexual transmission of HIV. It has been projected that young African Americans of college age will be the next group to be affected by the HIV/AIDS epidemic. The goals of this research were to identify barriers to African American college students engaging in safer sex behaviors; determine whether barriers to safer sex differ for African American men versus African American women; and use the findings to help identify strategies likely to promote safer sex practices among African American college students. The Nominal Group Technique (NGT) was used to collect the information. The results yielded the following themes. For males and females, the combined themes, negative views of condoms were ranked the most important with a score of 70. Trust issues were ranked the second most important with a total score of 47. The third highest ranked theme was living for the moment with a total score of 43. The fourth highest ranked theme was feeling invincible with a total score of 42. The authors provide a number of recommendations for consideration in the development of HIV prevention programs for African American college students.

Adolescent↗
PubMedDate not supplied

Contrast agents in patients on dialysis.

Contrast media are used to enhance the structural and functional information that is provided by imaging methods. They are used particularly in conventional radiographic (X-ray) investigations, but are also used in magnetic resonance imaging (MRI) and increasingly in ultrasound (US). The water-soluble, iodinated, intravascular radiographic agents are commonly used, and in large doses. They are excreted almost exclusively by the kidney and may have nephrotoxic effects. The use of these agents in patients with renal impairment may potentially be problematic. In this article the chemical composition and pharmacokinetics of these contrast agents are reviewed, as are their potentially toxic effects on the heart, neural tissues, kidney, and endothelium. Their safety for use in the patient with end-stage renal disease (ESRD) and those on dialysis is discussed. This aspect is also addressed briefly for the contrast agents used to augment MRI and US.

Contrast Media↗