422 URIST, MACDONALD, MOSS, AND SKOOG 



spine has long been suspected bnt has yet to be subjected to a sys- 

 tematic investigation. 



Densitometric Methods of Diagnosis 



Renewed effort has been made to perfect densitometry to enable 

 physicians to diagnose osteoporosis at an early stage of the disease 

 and evaluate the efficacy of dijfferent methods of treatment. Nordin 

 et al. ( 1962a ) devised an interesting technic in which lateral tomo- 

 grams were prepared of the patient and a dissected specimen of 

 the lumbar spine was placed next to the subject. The film images 

 were fed through a Laurence-Locarte recording densitometer. The 

 ratio of the densities of the subject and the standard was called the 

 relative vertebral density. It was concluded that the codfish spine 

 occurred when the vertebral body was less dense than the inter- 

 vertebral discs. Mavo ( 1961 ) made a similar survey and concluded 

 that the individual could lose a relatively large amount of bone 

 mineral and still fall within the range of normal individuals, and 

 that the early diagnosis of osteoporosis is limited by these considera- 

 tions. Such limitations did not applv to the use of quantitative 

 methods for measuring changes in the bones with time in the same 

 individual. Doyle (1961) surveved the proximal end of the ulna, 

 and Wagner and Schaaf (1961) examined the thumb, and corrob- 

 orated these results. 



Vose ( 1962 ) described microradiographic changes in cortical bone. 

 The mineral content varied from 0.94 to 1.19 gm of hydroxyapatite 

 per cc of bone in normals and from 1.12 to 1.50 in osteoporotics. 

 Thus, while the bone mass was reduced in volume in osteoporosis, 

 the bone tissue that persisted was hypermineralized. This incre- 

 ment was apparently in amorphous plugs in blood vessels and in 

 the interstitial lamellae of old deposits. In view of the technical diffi- 

 culties, physical variables, and other complexities of con\'entional 

 x-rays for measurement of bone densit\', it is now desirable to search 

 for entirely different principles for obtaining quantitati\ e informa- 

 tion about osteoporosis. Jacobson (1962) is testing dichromatic ab- 

 sorption radiography for calcium in mineralized tissues; this method 

 gives greater contrast than an ordinary radiograph (Jacobson, 1953). 



