Positron emission tomographic measurement of blood-to-brain and blood-to-tumour transport of ⁸²Rb. II: Clinical data and validation of technique

For pt.I see ibid., vol.34, no.12, p.1773-84 (1989). Computer simulations and error analysis of a simple two-compartment, passive-diffusion exchange model for ⁸²Rb across the blood-brain-barrier (BBB) have demonstrated the feasibility of obtaining useful estimates of unidirectional rate constant (K₁) and tissue-blood water volume (V_b) in vivo using dynamic positron tomography (PET). The coefficients of variation (CV) in parameter estimates for 20 studies on ten patients are shown to have mean values of 10% for tumour K₁ and V_b, 6% for normal brain V_b and 30% for normal brain K₁. Ten test-retest studies show a very high correlation (R²>0.88) between the estimated parameter values. Apparent tissue blood volume (V_b) estimates obtained from ⁸²Rb studies underestimate the blood volumes obtained by single-breath C¹⁵O studies by approximately 15%. The data from these clinical studies are in agreement with the predictions of the computer simulations and suggest the suitability of ⁸²Rb/PET in the quantification of BBB functional changes.