Gamma camera scintigraphy of tumours using (195m)Pt-cisplatin

Platinum enriched with 194Pt was irradiated for 4 days in NRG's TIRO 1 reactor, to produce (195m)Pt. Spectral analysis of the product was performed using a calibrated hyper pure germanium detector and its constituent radioisotopes were identified as (195m)Pt, 199Au and 192Ir. Using the detector's intrinsic efficiency calibration, their activities were estimated to be 1049, 133 and 5.8 MBq, respectively. The performance of the gamma camera was tested using quality control procedures recommended by the Institute of Physics and Engineering in Medicine (IPEM) and was found to be satisfactory. A torso phantom was used to determine the minimum detection limit (MDL) of (195m)Pt in a 2 cm diameter tumour using SPECT acquisitions (32 steps, 60 s per step). The MDL was found to be 8 ppm assuming an administered patient dose of 50 MBq and a total cisplatin dose of 105 mg. This work indicates that (195m)Pt-cisplatin is suitable for clinical scintigraphy and has led to the development of a clinical protocol that has been approved for a pilot study.