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In population studies, in which patients and controls are of comparable size, bone mineral area density (BMD) gives reliable results for mean bone mass data although, with sequential data, BMD may under-estimate the degree of change in bone mass. In children BMD data should be reliable, provided that patients and controls, matched for age and sex, are also of the same size. With disease children may be small for their age so that low bone mass by BMD may be due to small body size and not necessarily to osteopoenia. In these situations the bone mineral content (BMC) index may be more reliable than BMD. To assess bone mass status in individuals, BMC index, as well as BMD, should be used, particularly with adults at the extremes of body size (the very small or very tall).

Measurements of body composition are made to assess nutritional status. The measurements used for these studies should be selected on the basis of reliability, as well as simplicity and costs, and reliability depends on the information required. In normal adults simple estimates of fat and lean tissue (LBM), i.e. the anthropometric measurements of weight, height and skin fold thickness, should be sufficient since the proportions, in LBM, of water, protein and bone mineral are relatively constant. Measurements of body water (by isotope dilution or bioelectrical impedance) allow indirect estimates of fat and LBM that are reliable, provided that water is a constant proportion of LBM. In disease states, however, including renal disease, it is well established that the proportion of water in LBM varies from significant water overload to dehydration. In disease, it is important to determine not only total LBM but also the quality of LBM, determining essential body protein as well as body water. Body protein can be measured directly by nuclear techniques. This procedure should be more readily available for the clinical investigation of nutritional status.

Nuclear magnetic resonance techniques can measure the fluoride levels in bone of the finger after a patient has ingested F in the treatment of osteoporosis, but does uptake in cortical bone reflect uptake in the critical trabecular bone? Investigation has been made of the relative uptake of fluoride from drinking water into trabecular and cortical bone of the rat. For fine detail of the uptake of F into the femur and vertebra, microprobe techniques were used with a spatial resolution of 10 microns; for broader studies, treating the femur as representative of cortical bone and the vertebra as typical of trabecular bone, chemical techniques using spectroscopy and ion-selective electrodes were employed. The conclusion is that in the rat uptake of F by cortical bone is indicative of uptake by trabecular bone, and that therefore as a working hypothesis NMR measurement of F in the finger may be taken as reflecting uptake of F by trabecular bone.

Two new facilities for in vivo activation analysis of patients have been designed, developed, and constructed at Toronto General Hospital. One of these is for the determination of body calcium for the diagnosis of osteoporosis and other diseases associated with bone loss. The other is for the measurement of total body nitrogen for the determination of protein status. These facilities replace old university facilities and take into account the comfort and management of patients. In addition, in the case of the calcium facility, the precision of the measurements has been improved because of larger detector volume and increased neutron source strength. Both the facilities are now in routine hospital clinical use.

The design and construction of a hospital clinical facility for in vivo prompt gamma neutron activation analysis for total body nitrogen (TBN) measurement is described. The use of 252Cf neutron sources gives a better signal-to-background ratio compared with 238Pu-Be sources of equal strength, thus yielding better reproducibility of measurements. By measuring the hydrogen and nitrogen signals separately using appropriate gating circuits, signal-to-background ratio is further improved. Measurements using a urea phantom (5.63 kg nitrogen as urea in 34.53 kg of water) show that 2 x 6 micrograms 252Cf sources gives a nitrogen signal-to-background ratio of 5.6 (compared with 3.4 in the case of a 2 x 10 Ci 238Pu-Be source) and a reproducibility for nitrogen signal of +/- 1.1% (CV) and for hydrogen signal (internal standard) of +/- 2.33% (CV). Approximately 30 minutes of patient's time is required for each TBN measurement with an estimated reproducibility of +/- 3.8% (CV). The radiation dose to the patient is about 0.2 mSv (effective dose equivalent; QF = 10) per 20 min measurement. A report for the clinician is produced within a few minutes after the measurement by a dedicated IBM-PC computer. The entire facility is clean, comfortable and the electronics and computer processing are simple and economical.

We have developed a localized noninvasive nuclear magnetic resonance (NMR) method for determining the accumulated bone fluoride content in human index fingers. Using a 27 MHz "split-ring" resonator probe, we measure the total fluoride (F) content within a 6.5 cm length of the distal end of the index finger from a calibrated determination of the intensity of the observed 19F free induction decay (FID) signal. Since fluoride impurities accumulate almost exclusively in bone mineral, the 19F resonance signal is broadened by rigid lattice magnetic dipole-dipole interactions, causing the FID signal to have a relatively short lifetime of approximately 75 microseconds. This short signal lifetime, plus the weakness of the signal strength prevents conventional magnetic resonance imaging equipment from observing the 19F in bone mineral. Nevertheless, we have achieved an in vivo sensitivity of +/- 0.5 mg fluoride in an observation period of 30 min. Assuming an index finger has between 0.25 and 0.5 g of bone calcium, this sensitivity is just sufficient to detect fluorides in the index finger of most adults whose bone fluoride concentration is greater than 2.0 mg fluoride/g calcium (0.8 mg/g ash weight). We are particularly interested in using this new NMR technique to monitor the rate of bone fluoride accumulation in osteoporotic patients receiving therapeutic levels of fluoride in their diets.

19F free induction decay (FID) signals have been observed from the index fingers of four male and two female adult volunteers using a 27-MHz pulsed nuclear magnetic resonance spectrometer equipped with a split ring resonator probe. The value of the in vivo spin-lattice relaxation time T1 of the fluoride ions naturally accumulated in bone mineral has been determined to be 2.0 +/- 0.3 s. The shape of the observed FID signals in the inhomogeneous external magnetic field indicates that the F distribution is not uniform along the length of the finger. The fluoride ion content of the index finger (within a 65-mm length from its distal end) was measured with a sensitivity of +/- 0.5 mg F within a 30-min observation time.

Data on five mining populations exposed to Rn progeny have been used to estimate the lifetime risk of lung cancer resulting from occupational and environmental exposure under current standards. Slopes of dose-response relations for lung cancer show a tendency to decrease with increasing dose. Our best estimate of curvilinearity is given by raising dose to the power 0.92 +/- 0.07, but the improvement in fit beyond simple linearity is not significant. On the other hand, the addition of a cell-killing term significantly improves the fit of the linear model. In any event, linear extrapolation is unlikely to underestimate the excess risk at low doses by more than a factor of 1.5. However, these inferences about curvilinearity are highly subject to error from the choice of reference populations, dosimetry, and latency. Under the linear-cell-killing model, our best estimate of excess relative risk is 2.28 +/- 0.35 per 100 working level month (WLM) (a doubling dose of 44 WLM). Attributable risks in these five studies range from 3.4-17.8 per 10(6) person-yr WLM-1. Risks from Rn progeny appear to interact with age and smoking in a form intermediate between additive and multiplicative. The "relative risk" model is therefore preferable for projecting lifetime risks, but life-table projections are described for a wide variety of assumptions. Our best estimate of the effect of a 50-yr occupational exposure to 4 WLM yr-1 is 130 excess lung cancer deaths per 1000 persons (0.65 per 1000 person-WLM), with a range from 60-250 per 1000. Similar calculations for lifetime exposure to an additional 0.02 working level (WL) beyond normal background produces an estimate of 20 excess lung cancers per 1000 persons.

Seven adults with familial hypophosphatemia have been investigated by histologic and radiographic examination of bone, and estimates of bone mineral status by in vivo neutron activation analysis (IVNAA). Histological examination showed severe osteomalacia and osteosclerosis in all cases. Radiography showed skeletal deformities and other sequelae of severe rickets of childhood in five of the seven cases, with, in addition, thickened well-mineralized bones; the other two showed normal radiographs. IVNAA measurements showed that the first five had greater than normal bone calcium and that the other two had normal values. Thus, in all cases there is a greater than normal total bone tissue (osteoid and mineralized bone together). The quantitative body calcium measurements show clearly that osteosclerosis occurs in familial hypophosphatemia, confirming the opinions based on histological and radiological data. Although there has been occasional reference to this sclerosis in the literature, up to the present it has received little attention.

A mehtod of measuring body nitrogen by neutron capture gamma analysis is described. The neutron flux is provided by four collimated 5 Ci Pu-Be sources, placed to give a bilateral irradiation of the subject. The 10-83 MeV thermal neutron capture gamma rays from 14N are detected by two heavily shielded 5 in X 4 in NaI(Tl) detectors. Results indicate a reproducibility +/-3% (1 SD) for a 10 min irradiation of the chest area, while giving a radiation dose equivalent of 50 mREM.

A major problem in the measurement of nitrogen in the body by in vivo neutron activation analysis is the size of the background. Investigations show that random summing of gamma rays in the range 4-7 MeV is a major contributor. By direct comparison, 252Cf is shown to be a better neutron source than Pu-Be in this regard. Data are presented on the contribution to the background of water and chloride in the body.

It has been widely believed that phosphate deficiency causes osteomalacia. Based on this belief, the rickets of familial hypophosphatemia has been attributed to phosphate deficiency associated with the hypophosphatemia. The present studies on rats have, however, demonstrated significant differences between the effects of phosphate deficiency on bone metabolism and the characteristic features of rickets. Weanling rats, maintained on a mildly phosphate deficient diet, had hypercalcemia and hypophosphatemia, and impairment of body growth, bone growth, and bone mineralization. The maximum effect was observed at 5 wk; between 5 and 20 wk the rats improved despite persistent hypophosphatemia. Histologically, at 5 wk the bone showed thick unmineralized osteoid seams covering most bone surfaces, but the epiphyseal cartilage was normal. In addition, the excess osteoid readily incorporated tetracycline indicating normal mineralization and, based on a new sequential pulse labeling technique, the linear bone apposition rate (LBA) was significantly (p < 0.001) increased above control values. This increase was observed within the initial 4 days of phosphate (P) deficiency and persisted up to 15 wk. This effect of P deficiency on LBA was dependent on vitamin D activity. At 4 wk, the mean LBA was 0.106 +/- 0.003 (1 SE) in control rats, 0.149 +/- 0.008 microns/hr in P deficient rats, 0.083 +/- 0.004 microns/hr in vitamin D deficient rats and 0.086 +/- 0.006 microns/hr in rats deficient in both P and vitamin D. We have reported a similar increase in LBA with parathyroid hormone activity. With vitamin D deficiency, phosphate deficient rats showed all the characteristic features of rickets; disorganization of epiphyseal cartilage, excessive unmineralized osteoid, and reduced mineralization based on the incorporation of tetracycline. We conclude that the effects of phosphate deficiency on bone metabolism more closely resembles the effects of PTH activity than the characteristic effects of osteomalacia and rickets.

Measurement of nitrogen in the human body gives a measure of total protein in the body. Nitrogen (N) may be measured in vivo by a nuclear technique in which the characteristic nitrogen gamma rays emitted after capture of neutrons are detected and counted. The accuracy (as determined by comparison of the measurement of nitrogen in a pig by nuclear and chemical methods) is better than 10%. The reproducibility is less than 6%. The radiation dose is about 5 millirads. This method had been used with 43 patients and 23 normal volunteers and the results are reported. The data are presented in the from of total N content, percentage N by weight, and as a comparison of N and potassium (K) in the body. It is found that the mean percentage of N in the normal males is 2.5%, giving a value of 1.75 kg in the 70-kg standard man. The mean percentage values are not greatly different between normal volunteers and malnourished patients. Taking all subjects, N/K ratios ranged from 7.5 to 20 g/g. Thus K cannot be used as a predictor of N. Nitrogen content of normals correlates well (r = 0.68) with height squared; for malnourished patients there is again a good correlation (r = 0.81) but the regression line for patients is approximately 34% below that for the volunteers consistent with their depleted state.

A 252Cf neutron-irradiation facility designed specifically for clinical in vivo measurement of calcium in the hand is described. Results of preliminary measurements are presented. Hand phantoms were exposed to the neutron beam for 10 min and the induced 49Ca activities were counted for 10 min after an elapsed time of 2 min. The results indicate that with a 2 X 100 micrograms 252Cf neutron source and two 20.3 X 12.7 cm NaI crystals, the counts per gram of bone mineral mass changes by about 4% for each 100 cm3 change in the overall volume (soft tissue plus bone) of the hand. For hands of equal volumes the counts per gram are expected to be almost independent of the bone volume. With an absorbed dose equivalent of 150 mSv (15 rem), the sensitivity is about 200 counts per 10 min per gram Ca. The statistical reproducibility of the results is better than 3% for the average value of 11 g Ca in the normal hand.

Lean body mass by anthropometry (AMLBM), total body potassium (TBK), and total body nitrogen (TBN) by prompt gamma analysis, are reported in 38 malnourished patients during total parenteral nutrition. Over long periods (greater than 2 months) TBN increased 32% while AMLBM and TBK rose only by 9.2 and 9.5%, respectively. Changes in AMLBM and in K were significantly correlated, but changes in nitrogen were not correlated with either. From short-term studies, the same conclusions can be obtained; although there are changes in lean body mass and in potassium, there is no correlation with such changes in nitrogen. With repletion, changes in body protein are not necessarily related to changes in AMLBM or to TBK: the latter two reflecting total and intracellular water, respectively, but not protein content.

The bone calcium status of 39 patients with chronic renal failure on hemodialysis has been measured by in vivo neutron activation analysis (IVNAA) and reported in terms of a calcium bone index (CaBl) which relates the calcium in a patient to that in a normal person of the same height. In 20 of the 39 cases sequential measurements were made over periods of up to 40 mo. The results are compared with data obtained by radiology and by histological examination of bone biopsies. CaBl values varied from below normal to, in one case, above the range of normal. Many of the higher values were associated with demonstrable osteosclerosis. As found in previous work here with IVNAA, significantly low values of CaBl were associated with vertebral deformities; however, some patients with deformity had normal CaBl values, indicating that these had both local mineral loss (resulting in fracture) and osteosclerosis. Taken all together, the data suggest that more than half the patients have osteosclerosis. Sequential data showed no uniform response to treatment.

Long-term anticonvulsant drug therapy may lead to abnormalities of calcium metabolism resulting in osteomalacia. The prevalence and severity of altered calcium metabolism was studied in an adult outpatient population of persons with epilepsy receiving anticonvulsant therapy for a minimum of 2 years. Assessment of calcium metabolism was based on serum concentrations of calcium, phosphorus, alkaline phosphatase and 25-hydroxycholecalciferol and of plasma parathyroid hormone, intestinal absorption of isotopic calcium and skeletal bone mineral mass as determined by in vivo neutron activation or x-ray photodensitometry.Thirty-nine patients who had been receiving anticonvulsant therapy for an average of 20 years were studied; none had clinical evidence of metabolic bone disease. Decreased serum calcium concentration was noted in 10%, decreased serum phosphorus concentration in 10% and elevated serum alkaline phosphatase concentration in 44%. The mean serum 25-hydroxycholecalciferol concentration was significantly lower (P < 0.001) than in a control group (11.6 v. 19.6 mg/mL). None of 18 patients studied had an increased plasma concentration of parathyroid hormone, and only 1 of 17 patients had decreased intestinal absorption of isotopic calcium. Bone mineral mass was decreased in 44% of 32 patients studied.It was concluded that long-term treatment with anticonvulsant drugs leads to mild abnormalities of calcium metabolism and decreased bone mineral mass in a substantial percentage of adult outpatients with epilepsy. These abnormalities probably predispose the patients to the development of clinically significant metabolic bone disease.

y composition was studied in 31 patients receiving chemotherapy for small-cell lung cancer. Patients were randomly assigned to receive either 4 weeks of total parenteral nutrition (study group) or to continue a self-regulated oral diet (control group). The relationship between height and total body nitrogen was altered initially for patients who had lost more than 5% of body weight. During the 4 weeks of parenteral nutrition, body weight, total body fat, and total body potassium, but not total body nitrogen, increased significantly in the study group (p less than 0.001). However, after parenteral nutrition was stopped, body weight and potassium levels in the study group fell significantly and to the same extent as in the control group. Nitrogen levels showed an overall fall in the 32 weeks of observation for both groups. After the period of parenteral nutrition, the decrease in body fat was significantly greater in the control group than in the study group (p less than 0.05). Thus, parenteral nutrition increased body fat and total body potassium, but not total body nitrogen.

Some non-rigid Malignant Hyperthermia Susceptible (MHS) patients have a greater than normal incidence of fractures. Radiologically their long bones are slightly thinner than normal. Excessive numbers of caries because of thin dental enamel may also be present. The Malignant Hyperthermic (MH) defects thus appears to involve cells of bone appendages as well as of muscle. We have measured the concentration of calcium in bone by neutron activation analysis and have found it to be reduced in both non-rigid and rigid malignant hyperthermia susceptible patients. The reductions were particularly marked for the non-rigid patients. Bone calcium concentrations were lower in males than in females and in those under 16 and over 60 years of age. This is additional evidence is favour of the hypothesis that malignant hyperthermia is a widespread defect affecting tissues and organs throughout the body.

In vivo free induction decay signals have been detected from the fluoride ion (F) content of human finger bones by a 27 MHz pulsed single-coil nuclear magnetic resonance (NMR) spectrometer. The intensity of these dipolar-broadened NMR signals can be used to estimate the F content of the middle phalanx of the index finger. This NMR procedure is the first non-invasive method capable of monitoring bone F contents. The preliminary results we report were obtained from patients known by previous biopsies to have relatively high bone F concentrations in their pelvis. This new monitoring technique does not yet have adequate sensitivity or accuracy for routine clinical use. As a research technique, it has applications to the diagnosis of fluorosis (both industrial and endemic) as well as renal osteodystrophy, and to the establishment of optimal NaF does for the treatment of osteoporosis.

Metabolic balance and calcium kinetic studies were performed in four patients with Paget's disease before treatment with salmon calcitonin and during the early and late stages of the treatment, which lasted 9 to 19 months, A significant decrease in bone turnover and 24-hour urine hydroxyproline and serum alkaline phosphatase values was observed in all patients. In contrast, the calcium, phosphorus and magnesium balances did not change significantly. In agreement with this, the partial body calcium, measured by in vivo neutron activation analysis, did not change. Intestinal calcium absorption increased initially, but returned to baseline levels 9 to 19 months after the study began. During the initial period there was a small, significant, but transient decrease in tubular reabsorption of phosphorus; this was accompanied by a significant decrease in serum phosphorus values--probably a direct effect of calcitonin rather than evidence of secondary hyperparathyroidism. Administration of salmon calcitonin to patients with Paget's disease decreases bone turnover without affecting calcium and phosphorus balances.

Dual-photon absorptiometry using 153Gd (44 and 100 keV) was used to measure the bone mineral content (BMC) of the trunk and of the total body (TBBM) in 7 volunteers with no overt bone disease. These values were compared to those obtained with partial-body neutron activation of calcium (trunk Ca). The trunk Ca seemed to represent best a 60 x 30 cm area; the correlation coefficient with the corresponding BMC in that area was 0.97 (SEE congruent to 7%). Trunk Ca was also highly correlated with TBBM (r = 0.96; SEE = 8%) and with radius BMC (r = 0.92; SEE = 11%), but the correlations with the BMC of smaller subareas of the trunk were lower (r congruent to 0.9; SEE approximately 12%). The BMC of the lumbar spine was only moderately correlated with trunk Ca, radius BMC and TBBM (r approximately 0.82; SEE approximately 18%), and only slightly more associated with trunk BMC (r approximately 0.88; SEE approximately 14%). The BMC of the combined lumbar-thoracic spine showed higher correlations with trunk Ca, radius BMC and TBBM (r approximately 0.87; SEE approximately 13%), and trunk BMC (r = 0.93; SEE approximately 10%). An accurate and sensitive measure of spinal status requires a direct measurement of that area.

In vivo neutron activation analysis has been used to measure bone mineral content in the central skeleton where osteoporotic fractures occur. To be of diagnostic value, the results must be normalized for body size. From data obtained from 74 healthy children and adults up to 55 years of age, we have found that the calcium in the central skeleton is approximately proportional to the cube of the subject's height. The correlation for the adults alone has an r value of 0.81. When data from both adults and children are used, r = 0.95. The validity of this cubic height relationship to the Ca concentration measurements has been further substantiated by studies on rats. The total femur calcium content of 110 rats from weanling to 25 weeks of age was proportional to the overall femur (length) 3.6 (or (length)2.6 per unit length) with r = 0.99. When the level of Ca content is related to data on normal subjects of the same body size (giving the Calcium Bone Index or CaBI) a good separation is obtained between normal volunteers and osteoporotic subjects. Volunteers who were 20 to 55 years of age had CABI 1.0 "/- .12 (SD) while osteoporotics had CaBI 0.69 +/- .10 (SD). When the calcium content as determined by in vivo activation analysis is expressed as a CaBI, it provides a powerful tool for the diagnosis of osteopenia. We suggest that all bone measurements, including peripheral ones, be normalized for body size in order to increase their diagnostic value.

The effect of sodium alginate on the gastrointestinal absorption of the tracers strontium-85 and calcium-47 was investigated in 19 human subjects. The tracers were administered orally with 100 mg. of a calcium carrier-calcium chloride. At the same time, sodium alginate was given in a commercial jelly. The sevenday per cent retentions of tracers were measured with a whole-body counter. After one month, the experiments were repeated without alginate so that each subject acted as his own control. Fifteen volunteers were given 1.5 g. of alginate, two were given 3.0 g. and two 0.3 g. 1.5 g. of alginate reduced the absorption of strontium by a factor of two with no significant effect on calcium absorption. The smaller dose of alginate (0.3 g.) appeared to have no effect on strontium or calcium absorption and the larger dose (3.0 g.) had no greater effect than the 1.5 g. dose.

Long-term bone calcium metabolism was measured using a whole body counter apparatus and the radioisotopes calcium-47 and strontium-85. Strontium was given with calcium in a single intravenous injection in order to estimate long-term retention of calcium. Calcium-47, with a short radio-active half-life, was measured directly for 20 days, and then indirectly from strontium retention for periods up to 200 days.The standard parameters of calcium transport were measured and, as well, a new parameter, calcium accretion to the fixed bone pool. These studies were carried out on 13 subjects, six of whom were selected "normals" and seven were patients with osteoporosis. Calcium accretion to the fixed bone pool, the new index of bone formation, varied from 100 to 210 mg. of calcium daily in normal subjects and from 70 to 340 mg./day in patients with osteoporosis. These values are one-third of those for the accretion to the total bone pool, the previously reported bone formation rate.