Comparison of 99mTc-methylenediphosphonate and 68Ga-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 68Ga. The radiolabeling parameters and clinical evaluation in patients with suspected bone metastases were compared with routinely used 99mTc-methylenediphosphonate (99mTc-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 68GaCl3 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. 99mTc-MDP and 68Ga-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 99mTc-MDP scan.

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