Katsuhiko Kasai

High Reproducibility of Tumor Hypoxia Evaluated by 18F-Fluoromisonidazole PET for Head and Neck Cancer

Tumor hypoxia is well known to be radiation resistant. 18F-fluoromisonidazole (18F-FMISO) PET has been used for noninvasive evaluation of hypoxia. Quantitative evaluation of 18F-FMISO uptake is thus expected to play an important role in the planning of dose escalation radiotherapy. However, the reproducibility of 18F-FMISO uptake has remained unclarified. We therefore investigated the reproducibility of tumor hypoxia by using quantitative analysis of 18F-FMISO uptake. Methods: Eleven patients with untreated head and neck cancer underwent 2 18F-FMISO PET/CT scans (18F-FMISO1 and 18F-FMISO2) with a 48-h interval prospectively. All images were acquired at 4 h after 18F-FMISO injection for 10 min. The maximum standardized uptake (SUVmax), tumor-to-blood ratio (TBR), and tumor-to-muscle ratio (TMR) of 18F-FMISO uptake were statistically compared between the 2 18F-FMISO scans by use of intraclass correlation coefficients (ICCs). The hypoxic volume was calculated as the area with a TBR of greater than or equal to 1.5 or the area with a TMR of greater than or equal to 1.25 to assess differences in hypoxic volume between the 2 18F-FMISO scans. The distances from the maximum uptake locations of the 18F-FMISO1 images to those of the 18F-FMISO2 images were measured to evaluate the locations of 18F-FMISO uptake. Results: The SUVmax (mean ± SD) for 18F-FMISO1 and 18F-FMISO2 was 3.16 ± 1.29 and 3.02 ± 1.12, respectively, with the difference between the 2 scans being 7.0% ± 4.6%. The TBRs for 18F-FMISO1 and 18F-FMISO2 were 2.98 ± 0.83 and 2.97 ± 0.64, respectively, with a difference of 9.9% ± 3.3%. The TMRs for 18F-FMISO1 and 18F-FMISO2 were 2.25 ± 0.71 and 2.19 ± 0.67, respectively, with a difference of 7.1% ± 5.3%. The ICCs for SUVmax, TBR, and TMR were 0.959, 0.913, and 0.965, respectively. The difference in hypoxic volume based on TBR was 1.8 ± 1.8 mL, and the difference in hypoxic volume based on TMR was 0.9 ± 1.3 mL, with ICCs of 0.986 and 0.996, respectively. The maximum uptake locations of the 18F-FMISO1 images were different from those of the 18F-FMISO2 images and were within the full width at half maximum of the PET/CT scanner, except in 1 case. Conclusion: The values for 18F-FMISO PET uptake and hypoxic volume in head and neck tumors between the 2 18F-FMISO scans were highly reproducible. Such high reproducibility of tumor hypoxia is promising for accurate radiation planning.

EFFECTS OF INTENSIFIED PULMONARY HYPERTENSION SPECIFIC VASODILATOR THERAPY ON MYOCARDIAL OXIDATIVE METABOLISM AASSESSED USING C-11 ACETATE PET IN PATIENTS WITH PULMONARY HYPERTENSION

Background: Elevated pulmonary arterial pressure may increase right ventricular (RV) oxidative metabolism in patients with pulmonary hypertension (PH). A pulmonary hypertension (PH)-speciic vasodilator decreases pulmonary arterial pressure. However, it is not clear whether such a treatment favorably affects RV myocardial oxidative metabolism. The purpose of this study was to investigate the possible impacts of the intensiied PH-speciic vasodilator therapy on myocardial energetics using 11C acetate PET.