Two nuclear medicine physicians qualitatively interpreted the PET scans independently of other clinical or radiologic information during a joint reading session. The location, extent, and appearance (focal or diffuse) of the metabolically active sites were noted. The presence of nodal metastasis or transdiphragmatic extension was also recorded when present. Lesions with higher activity than that of the mediastinum on the attenuation corrected images were considered malignant, using criteria validated for non-small cell lung cancer. A subjective visual score was assigned to each area using a five-point scale (0=definitely normal; l=probably normal; 2=possibly abnormal; 3=probably abnormal; 4=definitely abnormal).
Semiquantitative measurements of tracer uptake (standardized uptake values or SUV) were also obtained by measuring the ratio of the decay-corrected tracer uptake per gram of tumor to the injected dose, normalized for body weight. Buy birth control More info The SUV values were calculated in the largest tumor deposits to minimize partial volume effects, using the average pixel value within the region of interest. A threshold of 50% of the maximal lesion activity was used to define the tumor boundaries and ensure reproducible and consistent tumor sampling. The ratios of tumor to normal lung activity were also calculated. These indexes were generated to determine whether FDG imaging can objectively distinguish normal from abnormal tissues and to assess tumor response to therapy. A two-tailed t test was used to compare the SUV values among the subgroups of patients.
Twenty-two patients underwent a diagnostic video-assisted thoracoscopy under anesthesia. Six patients did not undergo this procedure, and the diagnosis was obtained by needle biopsy (four), pleural fluid cytology (one), and clinical follow-up (one). With standard thoracoscopic techniques and real-time imaging equipment, biopsy specimens were taken from the parietal pleura at the apex, diaphragm, and lateral chest wall and from the mediastinal and visceral pleura. Biopsy tissue samples were evaluated by frozen and permanent histologic sections, in addition to electron microscopic examination. Special stains, such as immunohistochemical techniques, were used to confirm the diagnosis of mesothelioma. Routine biochemical, microbiological, hematologic, and cytopathologic examinations were performed on any fluid removed during the procedure.