Abstract

Transmission-emission scanning of the thorax with a flood source of technetium-99m (99mTc), autologous 99mTc labelled red blood cells, and diethylenetriaminepenta-acetic acid (99mTc DTPA) allows measurement of thoracic tissue thickness and blood and interstitial volume per pixel of the gamma camera image. Volume of blood or interstitium per pixel divided by pixel area gives the thoracic tissue thickness for these two compartments. A measure of lung tissue thickness may be obtained by subtracting chest wall thickness as measured on a lateral chest radiograph. As part of the evaluation of this technique 13 patients were scanned before treatment for proved or presumed pneumocystis pneumonia and their results were compared with those of 12 normal young men, approximately matched for age. In the patients with pneumocystis pneumonia lung tissue thickness at the base of the right lung averaged 3.4 cm (71%) more than that in the normal subjects, and interstitial thickness was 1.2 cm (150%) more than in the normal subjects. After treatment 10 of the patients with pneumocystis pneumonia were scanned again. Lung tissue thickness remained greater than the control value by 1.2 cm and interstitial tissue thickness by 0.5 cm. Blood thickness remained unchanged. Lung tissue and interstitial tissue thickness was correlated with a numerical score of the changes in the chest radiograph. The changes in the properties of the lung tissue compartments in the patients presumably reflect the mural and intra-alveolar inflammation found in pneumocystis pneumonia. Transmission scanning alone measures the increase of lung tissue thickness as well as transmission-emission scanning. It may be of value in monitoring the progress of this condition during treatment.