Comparison between early and delayed images of 67Ga scintigraphy for evaluation of recurrent lymphoma

Introduction: Despite widespread use of 67Gallium for lymphoma evaluation, timing of imaging after injection is a matter of controversy and to the extent of our knowledge no direct comparison has been made between early and delayed gallium images. We aimed to compare 24 and 48 hours post injection planar gallium imaging for evaluation of lymphoma recurrence. Methods: 255 patients suspicious of recurrent lymphoma were included in the study. Twenty four and 48 hours post injection (10 mCi) whole body Gallium imaging was performed. Semi-quantitative evaluation (background corrected) was carried out in positive whole body 67Gallium scans. Diagnosis of recurrence was made by combination of clinical or pathologic examination if possible. In 59 patients the final diagnosis was made by tissue biopsy. In case of uncertain diagnosis, follow up of the patients (mean duration of 13 months) was used. The diagnosis was finally made by the referring hematologist. Results: Whole body gallium scintigraphy was positive in 115 out of 150 patients with recurrence (sensitivity of 76%). Comparison of the 24 and 48 hour images did not show any new lesion in the 48 hour images. However, delayed 48 hours images were required for definite detection of the gallium avid lesions in the abdominal and pelvic areas in 40 patients. Semi-quantitative evaluation of the lesions showed higher lesion to background ratio for 48 compared to the 24 hour images (p<0.001). Conclusions: Considering higher lesion to background activity in the 48 hour images, delayed whole body 67Gallium imaging may be more desirable for diagnosis of recurrent lymphoma, however 24 hour images may be sufficient. Delayed imaging can be reserved for suspicious activities (such as in abdominal images). This strategy can save time and is more convenient for the imaging centers.