P Tothill

Bone Mineral and Soft Tissue Measurements by Dual-Energy X-Ray Absorptiometry During Growth

There have been several previous compilations of reference ranges of total body bone mineral measured by dual-energy X-ray absorptiometry (DXA) in children and young adults during growth, but little attempt to compare the results or to consider differences arising from the use of instruments from different manufacturers. We measured bone mineral and soft tissue in 216 girls, aged 11-17 years, using a Hologic scanner. Our results were compared with those from four other studies, all performed on white subjects, but in different countries, and including measurements performed with Hologic, Lunar, and Norland scanners. The general pattern of bone growth with age was very similar in all the studies. Quantitative differences could largely be accounted for by known differences of calibration of DXA scanners from the different manufacturers. When bone mass was plotted against lean or total mass instead of age there were also close similarities. An apparent difference between boys and girls in one study was shown to be due to differences in soft tissue composition, rather than different patterns of bone growth. Conclusions from this apparent difference concerning the effect of estrogen at puberty were shown to be unwarranted.

Total body neutron activation analysis of calcium: calibration and normalisation.

An irradiation system has been designed, using a neutron beam from a cyclotron, which optimises the uniformity of activation of calcium. Induced activity is measured in a scanning, shadow-shield whole-body counter. Calibration has been effected and reproducibility assessed with three different types of phantom. Corrections were derived for variations in body height, depth and fat thickness. The coefficient of variation for repeated measurements of an anthropomorphic phantom was 1.8% for an absorbed dose equivalent of 13 mSv (1.3 rem). Measurements of total body calcium in 40 normal adults were used to derive normalisation factors which predict the normal calcium in a subject of given size and age. The coefficient of variation of normalised calcium was 6.2% in men and 6.6% in women, with the demonstration of an annual loss of 1.5% after the menopause. The narrow range should make single measurements useful for diagnostic purposes.

Changes in total body calcium following surgery for primary hyperparathyroidism

The aims of this study were to measure the deficit in total body calcium in patients with primary hyperparathyroidism and to observe whether this deficit was reversed by parathyroidectomy. Total body calcium was measured in five women and three men preoperatively, and the mean was found to be 11% below that of age-and sex-matched controls after normalization for postmenopausal age and body size (P less than 0.01). Following parathyroidectomy, repeat total body calcium measurements showed an increase of 7.1% over an average period of 14 months (P less than 0.03). In patients with primary hyperparathyroidism, total body calcium returns toward normal following surgical removal of the adenoma.

Normal levels of total body sodium and chlorine by neutron activation analysis

In vivo neutron activation analysis was used to measure total body sodium and chlorine in 18 male and 18 female normal adults. Corrections for body size were developed. Normalisation factors were derived which enable the prediction of the normal levels of sodium and chlorine in a subject. The coefficient of variation of normalised sodium was 5.9% in men and 6.9% in women, and of normalised chlorine 9.3% in men and 5.5% in women. In the range examined (40-70 years) no significant age dependence was observed for either element. Total body sodium was correlated with total body chlorine and total body calcium. Sodium excess, defined as the amount of body sodium in excess of that associated with chlorine, also correlated well with total body calcium. In females there was a mean annual loss of sodium excess of 1.2% after the menopause, similar to the loss of calcium.

Measurement of hand bone mineral content using single-photon absorptiometry

A single photon absorption imaging technique has been developed to assess the bone mass of the hand, especially in patients with rheumatoid arthritis or bronchial asthma. A modified rectilinear scanner images the hand by transmission scanning in a water bath with a 7.4 GBq 125I source. A microcomputer is used to calculate the bone mineral distribution, and the total bone mineral content (BMC) of the hand is determined from that distribution. The precision (coefficient of variation) of the measurement is 1.9%. A control population of 20 men and 58 women has been studied to determine normal variations in hand bone mineral content with age, sex, body size, hand volume and years since menopause. The normal men are found to have an average hand BMC of 25.1 g with a coefficient of variation (CV) of 22%, which is reduced to 12% by normalising for body size using span. The normal women had an average hand BMC of 18.0 g +/- 15%. The CV is reduced to 13% by normalising for span and years post-menopause.

Changes in Total Body Calcium after Renal Transplantation: Effect of Low-Dose Steroid Regime

Total body calcium was measured in 8 men and 4 women, aged 20-51 years, undergoing kidney transplantation. The initial measurement was made within 8 weeks of operation and subsequent measurements up to 33 months postoperatively. Transplant rejection was prevented by low-dose prednisolone therapy (20 mg/day). 2 patients underwent parathyroidectomy for hypercalcaemia, and their total body calcium increased by 29 g (3%) and 66 g (8%). In the remainder the mean annual change was -0.9% (3.7, SD) over an average follow-up period of 17 months. This fall in total body calcium was statistically insignificant and was smaller than that previously described in patients treated with higher doses of steroids.

The assessment of postmenopausal osteoporosis by total body neutron activation analysis.

Total body calcium (TBCa) was measured using a cyclotron for in vivo neutron activation analysis (IVNAA) in 20 healthy women, 15 women with vertebral compression fractures, and 8 women with wrist fractures. The precision of the technique, using phantoms, was 1.8% for a dose of 13 mSv. A formula for predicted TBCa (TBCap) was derived from the 20 normal women based on span and years postmenopause. The coefficient of variation of TBCa after normalization in the normal women was 6.6%. The mean TBCa values for the vertebral and wrist fracture groups were 69% and 84% of TBCap for women at the time of the menopause. The low TBCa in the wrist fracture group was attributable to post-menopausal bone loss. Of the low TBCa in the vertebral fracture group, about half the loss could be attributed to postmenopausal age and half to other factors.

In vivo precision of total body calcium and sodium measurements by neutron activation analysis

The authors show how measurements on patients over a long period of time to monitor either their bone loss as a result of disease or a change in bone calcium as a result of treatment, can be used to obtain a measurement of the long term precision of total body neutron activation analysis in vivo.

The seasonal variation of total body calcium.

Total body calcium was measured using in vivo neutron activation analysis in 156 patients with rheumatic diseases at six-month intervals. Evidence of seasonal variation was sought by relating deviation from a linear change to the month in which the measurement was made. A cyclic regression fitted to the data had an amplitude of 0.25% but a significance of only P = 0.08. The calcium balance studies of Malm were re-analysed to quantify the seasonal variation he had demonstrated in one group of men. The deduced variations of body calcium were highly significant, with a phase and amplitude very similar to the regression of our data. Both analyses differed from two previous reports of seasonal variations of part-body bone mineral of much greater amplitude and different phase.

Long-Term Effect of Dialysate Calcium and 1α-Hydroxycholecalciferol on Bone Calcium Content in Haemodialysis Patients as Measured by Neutron Activation Analysis of the Forearm

The effect of different concentrations of dialysate calcium and treatment with 1α-OHD3 on bone calcium content in haemodialysis patients was investigated over a 2½-year period. Part-body neutron activation analysis of the forearm with 252Cf was used to measure both an initial absolute calcium content and changes in the bone calcium. A highly significant inverse correlation (r = –0.84, p 3. The results of the study suggest that bone calcium loss is not necessarily influenced by dialysate calcium concentration but that 1α -OHD3 has a beneficial long-term effect on bone calcium content.