Non-invasive estimation of hepatic glucose uptake from [18F]FDG PET images using tissue-derived input functions.

PURPOSE: The liver is perfused through the portal vein and hepatic artery. Quantification of hepatic glucose uptake (HGU) using PET requires the use of an input function for both the hepatic artery and portal vein. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not practical in humans. The aim of this study was to develop and validate a new technique to obtain quantitative HGU by estimating the input function from PET images. METHODS: Normal pigs (n = 12) were studied with [18F]FDG PET, in which arterial and portal blood time-activity curves (TAC) were determined invasively to serve as reference measurements. The present technique consisted of two characteristics, i.e. using a model input function and simultaneously fitting multiple liver tissue TACs from images by minimizing the residual sum of square between the tissue TACs and fitted curves. The input function was obtained from the parameters determined from the fitting. The HGU values were computed by the estimated and measured input functions and compared between the methods. RESULTS: The estimated input functions were well reproduced. The HGU values, ranging from 0.005 to 0.02 ml/min per ml, were not significantly different between the two methods (r = 0.95, p < 0.001). A Bland-Altman plot demonstrated a small overestimation by the image-derived method with a bias of 0.00052 ml/min per g for HGU. CONCLUSION: The results presented demonstrate that the input function can be estimated directly from the PET image, supporting the fully non-invasive assessment of liver glucose metabolism in human studies.

Cerebral blood flow and metabolism measurement using positron emission tomography before and during internal carotid artery test occlusions: feasibility of rapid quantitative measurement of CBF and OEF/CMRO(2).

Balloon test occlusion (BTO) of the internal carotid artery (ICA) combined with cerebral blood flow (CBF) study is a sensitive test for predicting the outcome of permanent ICA occlusion. However, false negative results sometimes occur using single photon emission tomography (SPECT). We have recently developed a rapid positron emission tomography (PET) protocol that measures not only the CBF but also the cerebral oxygen metabolism before and during BTO in succession. We measured acute changes in regional CBF and OEF/CMRO(2) before and during BTO in three cases with large or giant cerebral aneurysms using the rapid PET protocol. Although no patients showed ischemic symptoms during BTO, PET studies exhibited mildly to moderately decreased CBF (9∼34%) compared to the values obtained before BTO in all cases. The average OEF during BTO was significantly increased (21% and 43%) than that of before BTO in two cases. The two cases were considered to be non-tolerant for permanent ICA occlusion and treated without ICA sacrifice. Measurement of the CBF and OEF/CMRO(2) using a rapid PET protocol before and during BTO is feasible and can be used for accurate assessment of tolerance prediction in ICA occlusion.

Non-invasive estimation of hepatic blood perfusion from H2 15O PET images using tissue-derived arterial and portal input functions.

PURPOSE: The liver is perfused through the portal vein and the hepatic artery. When its perfusion is assessed using positron emission tomography (PET) and (15)O-labeled water (H(2) (15)O), calculations require a dual blood input function (DIF), i.e., arterial and portal blood activity curves. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not feasible in humans. The aim of the present study was to develop a new technique to estimate quantitative liver perfusion from H(2) (15)O PET images with a completely non-invasive approach. METHODS: We studied normal pigs (n=14) in which arterial and portal blood tracer concentrations and Doppler ultrasonography flow rates were determined invasively to serve as reference measurements. Our technique consisted of using model DIF to create tissue model function and the latter method to simultaneously fit multiple liver time-activity curves from images. The parameters obtained reproduced the DIF. Simulation studies were performed to examine the magnitude of potential biases in the flow values and to optimize the extraction of multiple tissue curves from the image. RESULTS: The simulation showed that the error associated with assumed parameters was <10%, and the optimal number of tissue curves was between 10 and 20. The estimated DIFs were well reproduced against the measured ones. In addition, the calculated liver perfusion values were not different between the methods and showed a tight correlation (r=0.90). CONCLUSION: In conclusion, our results demonstrate that DIF can be estimated directly from tissue curves obtained through H(2) (15)O PET imaging. This suggests the possibility to enable completely non-invasive technique to assess liver perfusion in patho-physiological studies.

Spectroscopy of double-beta and inverse-beta decays from 100Mo for neutrinos.

Spectroscopic studies of two beta rays from 100Mo are shown to be of potential interest for investigating both the Majorana nu mass by neutrinoless double beta decay (0nubetabeta) and low energy solar nu's by inverse beta decay. With a multiton 100Mo detector, coincidence studies of correlated betabeta from 0nubetabeta, together with the large Q value ( Q(betabeta)), permit identification of the nu-mass term with a sensitivity of approximately 0.03 eV. Correlation studies of the inverse beta decay and the successive beta decay of 100Tc, together with the large capture rates for low energy solar nu's, make it possible to detect, in real time, individual low energy solar nu in the same detector.