1 14 3 COO - 1422 - 124 PROGRESS IN CLINICAL USE OF PHOTON ABSORPTIOMETRY* R.B. Mazess, P.F. Judy, C. Wilson, and J.R. Cameron Department of Radiology (Medical Physics Section) University of Wisconsin Hospital, Madison 53706 Proc. Int. Symp. Clinical Aspects of Metabolic Bone Diseas-- Detroit, June 1972) ExcerETa Medica Press- (in press) INTRODUCTION Direct photon absorptiometry by low energy (20- to 100-keV) radionuclide transmission scanning provides a precise and accurate (less than 2% error) indication of bone mineral content. This method, since its introduction a decade ago, has achieved widespread acceptance by researchers and clinicians concerned with measurement of the skeleton. Details of the method, experi- mental results, and varied applications have been described in numerous publications, and have been dealt with in a recent symposium volume (Cameron, 1970). The essence of the absorptiometric method consists of passing a mono- energetic well llimated beam of radiation, typically from a several hundred ., mCi source of 75 1 (27.4keV) across a limb; the changes of beam attenuation '- due to the bone mineral are recorded and analyzed. In the past decade con- siderable sophistication has been gained relating to instrumentation, data interpretation, and biomedical application. This report describes some of the technical progress made in our laboratory, particularly those innovations with direct bearing on medical applications. In addition, some of the bio- medical applications of absorptiometry and clinical findings are discussed. TECHNICAL INNOVATIONS (a) Direct Readout System: For the past decade most systems for photon absorptiometry have used scaler-timers and digital output. Over the past several years our laboratory has developed an analog system, using a precision linear-ratemeter and logarithmic conversion of the ratemeter signal, to pro- vide immediate digital readout of bone mineral content and bone width (Mazess et al., in press).The direct readout system has several advantages over digital handling of scan data including: (1) lower operational and equipment costs, (2) immediate availability of results, and (3) smaller size and weight, allowing greater mobility. These advantages have lead one company (Norland Instruments) to produce a commercially-available direct readout system. Complete plans for construction of such a system are available from the University of Wisconsin Instrumentation System Center (Engineering Research Bldg.) * Supported by NASA - Y - NGR - 50 - 002 - 051 and AEC-(11-1)-1422 NOTICE This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United StBtes Atomic Energy MASTER \- Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any ' legal liability or responsibility for the accuracy, com- pleteness or usefulness of any information, apparatus, product or process disclosed, or represents that its use ' would not infringe privately owned rights. < mmeUTION w THIS DOCumEr dm 9