Bone scintigraphy in pulmonary alveolar microlithiasis: a comparative study of radioactivity and density distribution.

A histologically proven case of pulmonary alveolar microlithiasis that demonstrated intense lung uptake of Tc-99m-MDP on a bone scan is presented. The spatial distribution within the lungs of the radioactivity and density was assessed either by single photon emission computed tomography (SPECT), or x-ray computed tomography (CT) respectively, and the regional magnitude of the two parameters were compared. The quantitative study of regional radioactivity and density revealed that both the parameters distributed symmetrically, showing gradual increase in magnitude from the upper to the lower lung regions. The radioactivity-density association observed in our patient may indicate on-going formation of microcalculi throughout the lungs, the degree of which is greater at the sites of more severe involvement.