Comparison of 99m Tc-methylenediphosphonate and 68 Ga-BPAMD PET/computed tomography imaging in bone metastasis.

Objective: Bone is considered as the third most common site of metastases, besides lung and liver. Early detection of skeletal metastases aids in better management of skeletal-related events. In the present study cold kit-based 2,2 ' ,2 '' -(10-(2-((diphosphonomethyl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (BPAMD) was labeled with 68 Ga. The radiolabeling parameters and clinical evaluation in patients with suspected bone metastases were compared with routinely used 99m Tc-methylenediphosphonate ( 99m Tc-MDP).

Methodology: The kit components of MDP were incubated with at room temperature for 10 min, followed by radiochemical purity testing using thin-layer chromatography. For radiolabeling of BPAMD, the cold kit components reconstituted in 400 μL of HPLC grade water were transferred and incubated with 68 GaCl 3 in the reactor vessel of the fluidic module at 95°C for 20 min. Radiochemical yield and purity were determined with instant thin-layer chromatography using 0.5 M sodium citrate as mobile phase. For clinical evaluation, patients ( n  = 10) with suspected bone metastases were enrolled. 99m Tc-MDP and 68 Ga-BPAMD scans were performed on two different days in random order. Imaging outcomes were noted and compared.

Results: Radiolabeling of both tracers is facile using cold kit, although BPAMD requires heating. The radiochemical purity was observed to be greater than 99% for all preparations. Both MDP and BPAMD detected skeletal lesions; however, additional lesions were detected in total of seven patients which were not visualized clearly on 99m Tc-MDP scan.

Conclusion: BPAMD can be easily tagged with 68 Ga using cold kits. The radiotracer is suitable and efficient for detection of bone metastases using PET/computed tomography.