Comparison Studies of SPECT Dopamine Transporter Imaging and Noninvasive Quantification using < Tc-99m > TRODAT-1 and < I-123 > IPT

Kim, Hee Joung; Bong, Jung Kyun; Lee, Hee Kyung

Abstract

The SPECT radiopharmaceuticals labeled with I-123 for dopamine transporter imaging have been used to measure dopamine transporters in patients with movement disorders. However, a cyclotron produced I-123 limits its availiability and ease of use as a radioisotope to be labeled with pharmaceuticals in routine clinical diagnostic procedures. Recently, new radiopharmaceuticals for Tc-99m which has optimal characteristic for SPECT imaging have been developed to overcome the limits of using I-123. The purpose of this study was to compare the quality of [Tc-99m]TRODAT-1 with [I-123]IPT SPECT data and then to evaluate the usefulness of [Tc-99m]TRODAT-I SPECT by using three noninvasive simplified quantitative methods. TRODAT-1 labeled with Tc-99m(15.93+/-0.82 mCi) and IPT labeled with I-123(6.60+/-0.11 mCi) were injected into five normal controls. Dynamic [Tc-99m] TRODAT-I SPECT scans of brain were performed for 10 minutes each over 180 minnutes, and for 20 minutes at 4 hrs and 5 hrs. [I-123IPT SPECT scans were performed for 5 minutes each over 120 minutes. Time activity curves were generated for the left basal ganglia(LBG), right basal ganglia(RBG), and occipital cortex(OCC). Dopamine transporter parameters were obtained using (BG-OCC)/OCC, graphical method(Rv), and area ratio method(RA). TRODAT-1 and IPT SPECT imaging showed high uptake at the level of the basal ganglia. (BG-OCC)/OCC ratios for TRODAT-1 and IPT were 0.80+/-0.14, and 3.22+/-0.81, Rvs were 0.62+/-0.12, and 2.30+/-0.35, and RAs were 0.37+/-0.08 and 1.73+/-0.31, respectively. In conclusion, further improvement of [Tc-99m]TRODAT-I imaging characteris- tics may be required to estimate the dopamine transporter concentrations in human brains although it shows clear BG localization.