Intakes of radionuclides are estimated with the personal air sampler (PAS) and by biological monitoring techniques: in the case of plutonium, there are problems with both methods. The statistical variation in activity collected when sampling radioactive aerosols with low number concentrations was investigated. By treating man as an ideal sampler, an analytical expression was developed for the probability distribution of intake following a single measurement on a PAS. The dependence on aerosol size, specific activity and density was investigated. The methods were extended to apply to routine monitoring procedures for plutonium. Simple algebraic approximations were developed to give the probability of exceeding estimated intakes and doses by given factors. The conditions were defined under which PAS monitoring meets the ICRP definition of adequacy. It was shown that the PAS is barely adequate for monitoring plutonium at ALl levels in typical workplaceconditions. Two algorithms were developed, enabling non-recycling and recycling compartmental models to be solved. Their accuracy and speed were investigated, and methods of dealing with partitioning, continuous intake, and radioactive progeny were discussed. Analytical, rather than numerical, methods were used. These are faster, and thus ideally suited for implementation on microcomputers. The algorithms enable non-specialists to solve quickly and easily any first order compartmental model, including all the ICRP metabolic models. Nonrecycling models with up to 50 compartments can be solved in seconds: recycling models take a little longer. A biokinetic model for plutonium in man following systemic uptake was developed. The proposed ICRP lung model (1989) was represented by a first order compartmental model. These two models were combined, and the recycling algorithm was used to calculate urinary and faecal excretion of plutonium following acute or chronic intake by inhalation. The results indicate much lower urinary excretion than predicted by ICRP Publication 54.

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Microwave thermography has been used for the objective assessment of inflammation in the knee joints and wrist and finger joints of patients suffering with rheumatoid arthritis by comparison with similar information obtained from a control group of subjects. Combined microwave and thermal modelling has been used to estimate the effective blood supply to the anterior intra-articular region of the patella, and the perfusion of the quadriceps muscle in both groups. 2-D numerical modelling was compared with results obtained using 1-D modelling. Microwave thermography has also been used for the detection of breast cancer. However, problems such as high false positive detection rates have occurred due to natural cyclical breast temperature changes. The thermal behaviour of the normal breast throughout the menstrual cycle has been investigated and it is shown that microwave thermography is capable of detecting temperature variations in the female breast corresponding to the ovulatory and luteal phase of the menstrual cycle. Combined microwave and thermal modelling estimated the effective perfusion of the normal breast to be in the range 0.2 - ˜ 2 kg m-3s-1. This is consistent with previous work. Microwave thermography is a quick, simple technique which clinicians can easily use. It is non-invasive, passive and causes the patient no distress. By using combined microwave and thermal modelling it is possible to estimate tissue blood perfusions and water contents and compare them with expected values. The technique has many potential applications and will hopefully find a secure niche in clinical medicine.

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