Utility of camera-based FDG PET in the detection of recurrence in the follow-up of patients with malignant lymphomas

Evaluated the usefulness of F-18 FDG coincidence (CoDe) PET using a dual-head gamma camera in the detection of recurrence in patients with malignant lymphomas after treatment. Forty-four CoDe-PET studies were performed in 29 patients with histologically proven malignant lymphomas for the follow-up evaluation after the remission. CoDe-PET began 60 minutes after the injection of 111-185 MBq of F-19 FDG in the fasting state of 6-12 hours. CoDe-PET was performed using a dual-head gamma camera equipped with coincidence detection circuitry (Varicam R, Elscint, Haifa, Israel). A whole trunk from cervical to inguinal regions or selected region were scanned in supine position. There was no attenuation correction made and reconstruction was done using a filtered back-projection. CoDe-PET studies were evaluated visually and compared with the results of CT or MRI. The results of CoDe-PET and of CT or MRI were validated histologically or by radiological and clinical follow-ups. Of forty-four studies, 37 were validated. The overall sensitivity and specificity of CoDe-PET in the detection of recurrent lesions were 78% (7/9) and 89%( 25/28), respectively. MRI or CT showed the sensitivity of 83% (5/6) and the specificity of 67% (8/12). There were three false positive and two false negative CoDe-PET results. Positive and negative predictive values were 70% and 93% respectively for CoDe-PET, and 56% and 89% for CT or MRI. There were 7 patients of confirmed recurrence. The average recurrence time after the completion of treatment was 14.3 months. Camera-based PET with F-18 FDG has slightly lower sensitivity than CT or MRI but much higher specificity for the detection of recurrent malignant lymphomas. Therefore, for better sensitivity, it should be interpreted in conjunction with CT or MRI. However, camera-based PET shows high negative predicted value in the follow-up of patients with malignant lymphomas after the remission