Use of ¹⁹⁹Tl-diethyldithiocarbanate for radionuclide investigation of the brain: radiochemical and scintigraphic aspects

The aim of the work is to define the optimal technological conditions for preparing ¹⁹⁹Tl-DDC injection form extempore and to develop the methodology of single-photon emission computer-aided tomography (SPECT) with this radiopharmaceutical (RP). The lipophilic properties of ¹⁹⁹T1-DDC were tested by ascending paper chromatography in methylethylketone. Sixty-five brain SPECT investigations with ¹⁹⁹T1-DDC were performed. For comparing this method with a known analog, 14 of these patients were examined using ⁹⁹⁴Tc-hezamethyl propylene amine oxime (^99mTc-HMPAO). The injection form of 199Tl-DDC is prepared by heating 9-10 mg of DDC and ¹⁹⁹Tl-chloride solution with specific radioactivity of 2.7-3.6 mCi/ml at 85-90°C in a thermostat for 20 min. The best tomoscintigrams and maximal accumulation of RP in the brain were observed 25-30 min after intravenous injection of ¹⁹⁹T1-DDC. In order to decrease the interference of the Compton effect caused by short-wave electromagnetic radiation of ¹⁹⁹T1, high-power parallel collimator should be used. Preparation of ¹⁹⁹Tl-DDC injection form as described above insures high quality of brain scintigrams.