Tumor Blood Flow Measured by PET Dynamic Imaging of First-Pass ¹⁸F-FDG Uptake: A Comparison with ¹⁵O-Labeled Water-Measured Blood Flow

Abstract

PET molecular imaging of 15 O-labeled water is the gold standard for measuring blood flow in humans. However, this requires an on-site cyclotron to produce the short-lived 15 O tracer, which is cost-prohibitive for most clinical PET centers. The purpose of this study was to determine if the early uptake of 18 F-FDG could be used to measure regional blood flow in tumors in the absence of 15 O-water. Methods: PET scans were obtained in patients being evaluated for tumor perfusion and glucose metabolism in a phase I dose-escalating protocol for endostatin, a novel antiangiogenic agent. A 2-min perfusion scan was performed with a bolus injection of 2,220 MBq (60 mCi) of 15 O-water, which was followed by a 370-MBq (10 mCi) dose of 18 F-FDG. Four sequential scans of 18 F-FDG uptake were acquired, consisting of an early 2-min uptake scan-or first-pass scan-and 3 sequential 15-min late 18 F-FDG uptake scans. Regions of interest (ROIs) were drawn on 2 or more tumor sites and on back muscle, as a control ROI, for each patient. Arterial blood concentration was derived from the PET scans by drawing an ROI over a large artery in the field of view. Blood flow was computed with a simple 1-compartment blood flow model using the first 2 min of data after injection. Results: Blood flow estimated from the early uptake of 18 F-FDG was linearly correlated with 15 O-measured blood flow, with an intercept of 0.01, a slope of 0.86, and an R 2 regression coefficient of 0.74 (r 5 0.86). The 18 F-FDG tumor extraction fraction relative to 15 O-water averaged 0.86. A preliminary case study of a patient with prostate cancer confirms the utility of the first-pass 18 F-FDG blood flow analysis in tumor diagnosis. Conclusion: These results suggest that the first-pass uptake of 18 F-FDG may provide an estimate of perfusion in a tumor within the limitations of incomplete extraction of 18 F-FDG compared with 15 O-water.

Early Dynamic 18F-FDG PET to Detect Hyperperfusion in Hepatocellular Carcinoma Liver Lesions

“…Another noteworthy difference between our protocol and that of Bernstine et al was that we worked with a lower, more standard (20) 18 F-FDG activity and a faster injection rate and injection: 250 MBq at 100 MBq/s, for a 2.5-s bolus versus 500 MBq at 50 MBq/s, for a 10-s bolus. We thereby sought to produce well-distinguishable curves despite the use of standard 18 F-FDG activities.…”

“…Washout was defined as a downward trend in signal intensity in the focal finding after peak signal intensity had been attained. All findings of hypervascularized tumors were confirmed morphologically, through side-by-side comparison with a CE CT scan, because the Volumetric Analysis software did not support presentation of an 18 F-FDG PET/CT hybrid image.…”

“…Because only approximately 50%-70% of HCC tumors exhibit glucose metabolism higher than that of the liver parenchyma (14,15), conventional late static whole-body (WB) 18 F-FDG PET combined with CT plays a subordinate role in HCC primary diagnosis. However, this procedure is often used to help confirm liver transplant eligibility by excluding extrahepatic tumor (16,17).…”

Getting the Most out of 18F-FDG PET Scans: The Predictive Value of 18F-FDG PET–Derived Blood Flow Estimates for Breast Cancer

“…An alternative method for estimating BF from 18 F-FDG PET uses the first-pass extraction model of Mullani et al (5), which assumes highly extracted tracers can be used to estimate BF with a 1-compartment model during the first pass of the tracer through the tissue that in practice requires only a 2-min dynamic PET scan starting simultaneously with injection of 18 F-FDG (6)(7)(8). The average first-pass 18 F-FDG BF (first-pass BF) estimates using this method were found to correlate with 15 O-water (R 2 5 0.74), with first-pass BF estimates being on average 14% below BF estimates from 15 O-water PET scans (6).…”

Role of Positron Emission Tomography for the Monitoring of Response to Therapy in Breast Cancer

“…Indeed, dynamic FDG-PET can indirectly evaluate blood flow using a two-compartment model [100,102], but it requires an acquisition of 1 hour. Mullani et al [103] used a shorter first-pass method to calculate blood flow by dynamic imaging 2 minutes after FDG injection: it was linearly correlated with the 15 O-water method. Cochet et al [104] demonstrated that, in breast cancer, blood flow determined with this first-pass FDG method was correlated with tumor angiogenesis evaluated by immunohistochemistry.…”