Measurement of trabecular bone mineral density in the distal radius by two gamma-ray computed tomography scanners.

The precision and measurement agreement of two gamma-ray computed tomography forearm bone scanners have been evaluated. The inherent precision in vitro for the Stratec SCT 900 scanner was 0.28% compared with 0.04% for the OSCAR scanner. The measurements were linear over the range of densities found in humans. Increasing thickness of the cortical shell dramatically increased trabecular bone attenuation coefficient (TBAC) for the SCT 900, but only slightly affected results with the OSCAR. Short-term precision of the SCT 900 in 22 women (1.26%) was not as good as that previously reported for the OSCAR (0.50%). The measured TBAC for the same patients was significantly greater with the SCT 900. Corrections for the error introduced by the cortical shell of the radius with the SCT were calculated. Using this correction similar TBAC values could be obtained with both scanners, but the variance of the differences was too great for the results to be used interchangeably. Published bone density data for normal subjects indicate that Scottish women lose more trabecular bone in the two decades after 50 years of age than those in the Federal Republic of Germany.

The value of thallium scintigraphy in a district general hospital.

The usefulness of exercise Tl scintigraphy (combined with electrocardiography) in a district general hospital has been assessed in 80 patients in whom a previous exercise electrocardiogram (ECG) had not been definitive. Seventy-five of the patients presented with chest pain and five with no pain but an abnormal ECG. Case notes and test results were examined to establish the clinicians' judgment of the likelihood of having coronary heart disease (CHD) and the patient's outcome. The mean time of follow-up was 27 months. In the majority of patients the test was found to help the clinician come to a decision on the presence or absence of CHD. It was found to be particularly useful in patients with abnormal resting ECGs. There was a shorter time to discharge for patients classified as highly unlikely of having CHD. Only four patients were re-referred following discharge from the outpatient clinic. Nine patients were referred for coronary angiography with five being found to have significant stenosis. None of the 16 patients in whom the exercise ECG was normal had ischaemic myocardial segments in the Tl scintigraphy.

Quantitative gamma-ray computed tomography of the radius in normal subjects and osteoporotic patients.

A new design of gamma-ray computed tomography (CT) scanner was used to measure bone density in 516 normal adults and in 116 female patients with osteoporotic fractures. Trabecular bone density (TBD) was measured for a core of the ultradistal radius; cortical bone mass per unit length (MLS) and mass per unit volume (MVS) were computed for the radius shaft. TBD, MLS and MVS peaked at the age of about 40 in females and fell by 32%, 15% and 24%, respectively, by the age of 65. In males, TBD decreased from the third decade and MLS and MVS peaked in the fourth decade. The corresponding falls by 65 years were 20%, 6% and 7%. In patients with Colles' fracture TBD and MLS were reduced by 13% and 10%, respectively, relative to age matched normal female subjects. For patients with vertebral crush fracture the reductions relative to age matched normal females were 36%, 17% and 16% for TBD, MLS and MVS. In fracture patients the deficit in TBD was significantly greater than that for cortical bone but TBD was no better at discriminating normal and osteoporotic individuals because of its larger normal range. We conclude that gamma-ray CT may best be used for monitoring changes in bone rather than as a diagnostic screening tool.

Differential effect of long-term oestrogen therapy on trabecular and cortical bone.

The effect of long-term oestrogen therapy has been assessed in 40 oophorectomised women. Twenty-one of the women had received mestranol (mean 26 micrograms/day) and 19 received placebo tablets for a mean duration of 14 yr. A newly developed gamma-ray computed tomography (CT) scanner was used to measure trabecular and cortical bone separately in the distal radius. Bone density in the lumbar spine was measured using dual photon absorptiometry (DPA). Prevention against bone loss was demonstrated at all sites for the mestranol treated group (P less than 0.01). The deficit of radial trabecular bone (27%) was greater than that for radical cortical bone (14%). The deficit for the spine was intermediate (20%). One-year follow-up radial measurements showed a significant 1.2% increase (P less than 0.01) in cortical bone for the treated group. The DPA measurement was found to be best correlated (r = 0.80) with a mixed trabecular and cortical bone parameter in the radius. We conclude that the degree of bone loss at any site is dependent on the proportion of trabecular bone present.

Comparison of broadband ultrasonic attenuation of the os calcis and quantitative computed tomography of the distal radius.

The measurement of broadband ultrasonic attenuation (BUA) in the os calcis, which consists of predominantly trabecular bone, has been compared by others with single photon absorptiometry of forearm cortical bone. We have compared BUA in 24 female subjects with the separate measurement of trabecular and cortical bone in the distal radius using quantitative computed tomography (QCT). BUA was highly significantly correlated with each of the measurements in the radius (P less than 0.001). Paradoxically, BUA was found to be best correlated with the bone mass per unit length in the radial shaft (r = 0.85) rather than with radial trabecular bone (r = 0.66). The degree of correlation was not sufficient to predict radial bone mass accurately in individuals. Broadband ultrasonic attenuation, however, appears to be a useful measurement of bone in the appendicular skeleton.

Precision of measurement of bone density with a special purpose computed tomography scanner.

A new, special purpose, low-dose computed tomography scanner has been developed for the precise measurement of bone density in the distal radius. The instrument includes an 125I source and four scintillation detectors which are scanned across a section of the forearm to produce a cross-sectional image. A number of innovative features have been included to improve patient comfort and scanner precision. The reproducibility for trabecular bone measurement was 0.5% for repeated scans in 22 subjects. The long-term precision in a group of normal subjects was better than 5 mg cm-3. The high precision and the separate measurement of trabecular bone make this technique suitable for the longitudinal study of bone density in metabolic bone disease.

A gamma-ray computed tomography scanner for the quantitative measurement of bone density.

A special purpose gamma-ray computed tomography scanner has been developed for the precise measurement of bone density in the distal forearm. Details of the scanner hardware and computer analysis technique are given. Suitable phantoms have been used to test the operation of the scanner, which has been used to measure trabecular and cortical bone density with a precision better than 1%.

111Indium-labelled white blood cells in the diagnosis of Felty's syndrome.

The use of isotope scanning of the spleen in conjunction with 51Cr-labelled red blood cells has become an established technique in the evaluation of patients with hypersplenism. As far as we are aware the similar technique using labelled white blood cells to demonstrate splenic sequestration in a neutropenic patient has not been described. We report a case where this technique proved valuable in confirming the diagnosis and in predicting a favourable response to splenectomy.