GA-67 SCINTIGRAPHY WITH A DUAL-HEAD CAMERA

High quality images are necessary for correct interpretation of Ga-67 studies in lymphoma. The authors were interested if there is a signifi cant change in the quality of the Ga-67 images using a newly introduce d dual-head camera compared with a conventional single-head camera. Th e tomographic spatial resolution, full width at half maximum, was foun d to be 9.63 mm compared with 13.7 for a single-head camera. The volum e sensitivity was 380 cps/muCi/ml per axial cm as compared with 333 cp s/muCi/ml, and point source sensitivity was 5.6 cps/muCi compared with 3.8. There was a significant difference (P < 0.001), when using the t hreshold technique, in the number of counts per pixel over a wide rang e of volumes and concentrations in phantoms when the two cameras were compared. There was also a significant difference (P < 0.001) in Ga-67 uptake in lymphoma lesions in patients when the same parameters were used for both cameras when using SPECT. The average uptake in lymphoma lesions, using a dual-head camera, was 529 counts/pixel with a range of 112 to 1275 counts/pixel in different tumors. With a single-head ca mera, the average for the same tumor was 216 counts/pixel with a range of 59 to 469 counts/pixel. The high sensitivity of the dual-head came ra enabled high-quality, whole body scintigraphy, including the limbs, in 20 minutes compared with the 35 minutes necessary for the single-h ead camera for images which did not include the legs. Whole body Ga-67 scintigraphy is shown to be important in patients with lymphoma of th e upper and lower limbs. The high sensitivity of the dual-head camera enables the performance of SPECT studies at 7 days after injection and planar studies of satisfactory quality at 14 days, resulting in clear ance of the colonic activity and better evaluation of the abdomen. The authors conclude that, at the present time, a dual-head camera appear s to be the most appropriate equipment to use for Ga-67 scintigraphy.