Quantitative single-photon emission tomography for tumour blood flow measurement in bronchial carcinoma.

A single-photon emission tomography (SPET) technique for the absolute measurement of tumour perfusion is described. Phantom studies have shown that source-background ratios are dependent upon source size and radial position within the phantom. A means of correcting source-background count ratios for these variables has been developed and used to correct tumour-lung ratios obtained in 28 patients with bronchial carcinomas who underwent technetium-99m hexamethyl-propylene amine oxime (Tc-HMPAO) SPET. On SPET images, the normal lung appears as a relatively homogeneous background. The relationship between Tc background concentration (kBq/ml) and counts/pixel was determined from phantom studies and the tumour Tc concentration from the background Tc concentration and corrected tumour-lung ratio. The total activity of the lipophilic Tc-HMPAO species injected was measured. The activity reaching the systemic circulation ( A) was obtained by subtracting the activity trapped in the pulmonary circulation (obtained from background Tc concentration and lung volume). Tumour blood flow may then be calculated from fraction of A contained in the tumour provided cardiac output and extraction fraction are known. Blood flow through the central region of tumours ranged from zero to 59.0 (mean 14.1) ml min 100 g and through the whole tumour from 0.6 to 68.0 (mean 20.6) ml min 100 g. [ABSTRACT FROM AUTHOR]