FDG-PET/CT with additional SUV(max) analysis improves the diagnostic accuracy of adrenal lesions in cancer patients.

No abstract

When a threshold value of 35% of the measured maximum (18)FDG activity was adopted, the sizes of PET delineation were almost the same for static and moving phantom spheres of 22 mm or more in the axial plane. In addition, PET images have the potential to provide an individualized ITV.

Malignant lymphoma is the most common form of hematologic cancer, yet because of advanced methods of assessment, the traditional histology-based classification of lymphoma is insufficient for understanding lymphoma imaging. Still, radiologists should be familiar with the imaging findings in lymphoma. Integrated positron emission tomography (PET)-computed tomography (CT) allows improved diagnostic accuracy, and uptake of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) can help predict response during treatment. The sensitivity and specificity of FDG PET are superior to those of gallium 67 scintigraphy in all but indolent lymphoma. Both magnetic resonance (MR) imaging and CT allow excellent assessment of bone texture, but FDG PET is superior in demonstrating bone marrow metabolic activity. Thus, FDG PET is important in both the primary diagnosis and the evaluation of therapy in lymphoma. It may be difficult to determine whether residual abnormalities seen after the completion of chemotherapy-radiation therapy represent residual tumor or fibrotic tissue, but PET/CT may allow more accurate diagnosis than MR imaging or CT, thereby helping identify patients who require more intensive treatment. Some diagnostic pitfalls are encountered at FDG PET. However, anatomic CT helps localize and define disease and avoid these potential pitfalls.

To visualize intratumoral hypoxic areas and their reoxygenation before and during fractionated radiation therapy (RT), 18F-fluoromisonidazole positron emission tomography and computed tomography (F-MISO PET/CT) were performed. A total of 10 patients, consisting of four with head and neck cancers, four with gastrointestinal cancers, one with lung cancer, and one with uterine cancer, were included. F-MISO PET/CT was performed twice, before RT and during fractionated RT of approximately 20 Gy/10 fractions, for eight of the 10 patients. F-MISO maximum standardized uptake values (SUVmax) of normal muscles and tumors were measured. The tumor-to-muscle (T/M) ratios of F-MISO SUVmax were also calculated. Mean SUVmax ± standard deviation (SD) of normal muscles was 1.25 ± 0.17, and SUVmax above the mean + 2 SD (≥1.60 SUV) was regarded as a hypoxic area. Nine of the 10 tumors had an F-MISO SUVmax of ≥1.60. All eight tumors examined twice showed a decrease in the SUVmax, T/M ratio, or percentage of hypoxic volume (F-MISO ≥1.60) at approximately 20 Gy, indicating reoxygenation. In conclusion, accumulation of F-MISO of ≥1.60 SUV was regarded as an intratumoral hypoxic area in our F-MISO PET/CT system. Most human tumors (90%) in this small series had hypoxic areas before RT, although hypoxic volume was minimal (0.0–0.3%) for four of the 10 tumors. In addition, reoxygenation was observed in most tumors at two weeks of fractionated RT.