Bone scintigraphy with 99mTc-Alendronate: a potential bone imaging agent in place of other bisphosphonates

The aim of our study was to search the possibility of second generation bisphosphonates (4-amino-1 hydroxybutylidene-1, 1-biphosphonic acid) [Alendronate (A)] labeled with 99m Tc as a bone scanning radiopharmaceutical agent. Materials and methods. Kits with (A) 5 mg, stannous chloride 0.4 mg at a ph 4.8 and ascorbic acid 1 mg were labeled with 300 Mci of freshly eluted 99mTc and kept at room temperature for 10-15 min before injection. Patients (n=>200, range 6-85 years) with different bone pathology were studied 3-4 hrs after the i.v. injection of 20-25 mCi of 99mTc (A) according to routine whole body scanning. Scintigraphy with 99mTc (A) and 99mTc MDP (n=9) were compared in same patients regarding the quality of skeletal images. and uptake ratio bone/soft tissue (B/ST) calculated by region of interest (ROI) in lumbar vertebrae, sacrum and proximal femur. Scintigraphic images were evaluated and scored according to: a) bone delineation:(1, vertebrae ribs and other bones well delineated :(2, all bone delineated but vertebral bodies and ribs not all separated, 3:all bone delineated ribs and vertebrae not delineated); b)soft tissue uptake:(1: minimal, 2: moderate, 3: similar to bone) and c)image acceptability:(1: excellent, 2: good, 3: fair, 4: poor). Results: Images with 99mTc (A) showed high bone to background uptake with excellent contrast, no extra skeletal localization or other organ uptake due to the presence of free 99mTc. Comparisons of images of 99m Tc (A) with 99mTc MDP were of same quality and differences in (B/ST) were not statistically significant. Conclusion: The results of this study revealed that the scintigraphy with 99m Tc (A) produced excellent image of the skeleton. Therefore the use of this bisphosphonate is an adequate agent for routine bone scanning.