Validity of a Newly Developed Noninvasive Method for Estimating Cerebral Blood Flow Using 123I-IMP Acquisition Data from the Lungs and Brain

Objective: Previously we devised a method for estimating ¹²³I-IMP activity at 10 min after intravenous injection of ¹²³I-IMP (Ca10) without any blood sampling using ¹²³I-IMP autoradiography (ARG) acquisition data, and verified its usefulness for quantification of the regional cerebral blood flow (rCBF). In this study, we attempted to develop a more simplified method for estimation of Ca10 and to validate its usefulness for quantification of rCBF in a number of patients with different cerebrovascular diseases.

Methods: Consecutive 134 patients were examined for ¹²³I-IMP ARG study. Dynamic images of the lungs for 5 min and brain SPECT images for 30 min (6×5 min) and Ca 10 values were acquired from the first 35 patients. Using the data of the 35 patients, the regression equation for estimating Ca10 was calculated by the multiple regression analysis. The regression equation was applied to the other 99 patients who comprised 29 patients with Parkinson’s disease, 32 with common or internal carotid artery occlusion or stenosis, 14 with moyamoya disease, 12 with cerebral infarction, and 12 with other diseases. The mean of rCBFs in various regions of the brain (mCBF) calculated using the estimated Ca10 was compared with that calculated using directly measured Ca10 in the 99 patients. 

Results: The regression equation obtained was as follows: Estimated Ca10 =1070.1 +2.17 ×10^-3a-8.08 ∙ b - 2.23 ×c +2.47 ×10^-3d, where a: the area under the time-activity curve of the lungs (UCL), b: body weight, c: sum of UCL and the counts of brain projection data from 10 to 15 min after injection (CB1), d: those from 35 to 45 min (CB6), respectively. The estimated Ca10 closely correlated with the directly measured Ca10 (r=077). The mCBF values calculated using the estimated Ca10 closely correlated with those calculated using the directly measured Ca10 in all the patient groups (r=0.80, 0.78, 0.62, 0.77, 0.85 and 0.79 in patients with Parkinson’s disease, common or internal carotid artery occlusion or stenosis, moyamoya disease, cerebral infarction, and the other diseases, and total 99 patients, respectively).  

Conclusion: This study verified that the newly developed noninvasive method, which is more simplified than the previous method, can estimate reliably the Ca10 values which are available for quantification of rCBF in different patient groups.