HUMAN STUDIES WITH 99mTc ZOLEDRONIC ACID (99mTc-ZA) FOR SKELETAL SCINTIGRAPHY A PRELIMINARY EXPERIENCE

Aim: To study the optimal dose and optimal time of human skeletal imaging using Tc99m-ZA. Materials: 30 consecutive patients referred to the Nuclear Medicine department for bone scan were enrolled for the study after a valid consent.

Methods: The patients were divided into subgroups as described. Tc99m-ZA was prepared as per the standardised protocol. Patients were divided into 3 groups of 10 each. Group A1 was injected intravenously 5 mCi of tracer, Group A2 was injected 10 mCi of tracer and Group A3 was injected 15 mCi of tracer. The patients were asked to maintain good hydration. In each group the images were acquired at 1, 2, 2.5 hour(s) after tracer injection in all the patient groups in whole body mode using LEHR collimator. After completion of the study, the images were interpreted independently by two observers for the presence of adequate tracer uptake in the skeleton and also for optimal bone to background ratio. Their findings were then compared and when differences were there the decision was finalised by consensus. Findings: The skeletal images obtained using Tc99m-ZA were quite similar to those obtained with Tc99m MDP. The optimal dose for skeletal scintigraphy using Tc99m-ZA was 15 mCi. The optimal timing post tracer injection was 2 hours.

Conclusions: The images obtained with Tc99m-ZA are very encouraging. Their revelation of human skeleton matches with that is achieved with established agent Tc-MDP. However, further studies with a large cohort of patients are warranted for clinical use of Tc99m-ZA and establish its performance vis a vis Tc99m-MDP.