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The whole-body and part-body retention of 85Sr has been measured over a period of 150 days in 12 patients with Paget's disease, seven of whom were treated with calcitonin, starting 60 days after the 85Sr administration. Retentions were compared with those in a group of seven control subjects. The retention data were analysed using multiple exponential, single and double power-law and combined power law and exponential functions. The mean retention of 85Sr over a long period was greater in the Paget's patients than in the controls, 1.9 times at two months. No significant effect of calcitonin treatment was demonstrated. Part-body measurements based on profile scanning demonstrated a significantly increased uptake of 85Sr in sites where disease was present. The longer-term rate of disappearance from such sites was faster than from unaffected bones.

A comparison is made of the isotopic neutron sources 252 Cf and 238 Pu, Be for partial-body in vivo neutron activation analysis. Depth distributions of thermal neutron fluences in a water phantom are very similar for the two sources. The peak depth occurs at 5 cm. This value is approximately 2 cm less than the values obtained with uncollimated neutrons produced in broad-beam irradiations. With respect to the fluence-to-dose ratio, the 252 Cf neutrons have an advantage of approximately 1.4 over the 238 Pu, Be source. The use of 252 Cf offers two additional advantages for the investigator. First, it minimizes the on-line fast-neutron damage in Ge(Li) semiconductor detectors. Secondly, it is subject to much less stringent transport regulations that 238 Pu, Be. The latter feature takes on particular importance in view of the increasing usefulness of transportable instruments for in vivo cadmium measurements at the workplace.

An improved instrument is described for the measurement of liver and kidney cadmium by in vivo neutron activation analysis in both occupationally and environmentally exposed persons. Detailed calibrations of the instrument used in a study of 83 male workers at a cadmium production plant are give. The importance of accurate organ localisation by ultrasound is stressed, without which errors of 40 and 25% in individual and group kidney measurements, respectively, can occur. The detection limit (2 SD of the background) is 2.2 mg cadmium in the kidney and 1.5 micrograms g-1 (wet weight) in the liver for a local dose of 4.7 mSv. This instrument therefore combines the advantages of portability with high sensitivity of detection of cadmium.

Additional investigation of the authors' original technique for measuring total body nitrogen by prompt gamma neutron activation has demonstrated the need for certain changes in the calibration procedures in order to apply the method to studies of patients with abnormal metabolism. In the present technique, total body nitrogen, hydrogen, and fat were derived, simultaneously, from data obtained by neutron capture gamma-ray analysis combined with the measurements of body weight, total body water, and total body calcium. In this improved calibration technique total body nitrogen is more accurately measured, not only in normal subjects, but also in obese subjects and in patients with marked changes in hydration, such as cancer patients. The fat values calculated do not rely on a fixed relationship of total body water or total body potassium with lean body mass as in the previous studies, but are calculated as the difference between body weight and the sum of body water, protein and bone mineral ash. This improved technique has been applied to the study of three groups of subjects, the general population with a normal weight distribution and two extremes represented by obese and cancer patients.

A technique for the measurement of body iron utilising nuclear resonant scattering of gamma rays has been developed. 847 keV photons emitted from a gaseous 56MnCl2 source are resonantly scattered from 56Fe present in the body. Measurement is made using large volume Ge(Li) detectors. The spatial uniformity of activation, the sensitivity of the detection system and the limits of detection have been investigated. Measurements were made on a liver phantom. The resonance scattering technique permits determination of normal levels of Fe in the liver with a radiation dose of 2 rem.

A method for measuring Li in vivo in human brain is presented. The technique is based on the measurement of tritium gas exhaled by the subject following neutron irradiation of the organ of interest. The gas collection facility used to separate minute amounts of tritium from the breath is described. Methods for reducing the background levels of tritium were investigated. The limit of detection of the system is estimated to be 350 micrograms of Li for the whole brain for a dose of 10 mSv. This detection limit is sufficient for the study of patients treated with lithium compounds, but is too high to study 'normal' brain lithium content. The rate of elimination of tritium gas from the body was also investigated in animal studies. The method also appears suitable for the measurement of lithium levels in the kidney.

An in vivo method for the determination of Cd levels in human kidney and liver has been developed. The method allows detection of absolute quantities of Cd in the left kidney and Cd concentration in the liver. The limit of detection of cadmium is 2.5 mg for the left kidney and 1.8 microgram/g (wet weight) for the liver, for a localized dose of 670 mrem. The effects of patient positioning, organ geometry and liver-kidney interference on the measurement have been investigated using an Alderson phantom.