The DXL Calscan heel densitometer: evaluation and diagnostic thresholds

The DXL Calscan (Demetech AB) is a new dual energy X-ray absorptiometry device for determining heel bone mineral density (BMD). The system is based on the standard technique of dual energy X-ray absorptiometry (DXA), using a fan beam configuration, but introduces an additional laser measurement of heel thickness intended to improve accuracy. We have examined the utility, in vitro and in vivo performance of the DXL Calscan and established triage thresholds based on the UK's National Osteoporosis Society guidelines on peripheral densitometry. The Calscan proved convenient, easy to use and was stable over time and within a range of operating temperatures. Short-term in vitro precision as %CV, with phantom repositioning, was 0.75% and long term precision 0.73%. Precision in vivo, determined from duplicate right heel scans of 67 subjects, was 1.19%. Effective radiation dose to the patient was <0.1 microSv per scan. 140 white females (70 osteoporotic and 70 non-osteoporotic), aged 55-70 years underwent scans of both heels. Subjects were defined as osteoporotic or non-osteoporotic on the basis of axial DXA (spine L2-L4 and total hip). Triage thresholds for reassurance-referral or referral-treatment were 0.391 g cm(-2) and 0.306 g cm(-2) for non-dominant and 0.395 g cm(-2), 0.294 g cm(-2) for dominant heel, respectively. The non-dominant heel proved slightly superior to the dominant for triage purposes. Of the seven non-osteoporotic subjects misclassified as osteoporotic by Calscan of either heel, six had severe axial osteopenia. If operated by trained personnel and used in appropriate populations exhibiting risk factors, the Calscan is well suited for use in the management of post-menopausal osteoporosis.