[en] Recently, [I-123]IPT SPECT has been used for early diagnosis of Parkinson's patients (PP) by imaging dopamine transporter. The dynamic time activity curves in basal ganglia (BG) and occipital cortex(OCC) without blood samples were obtained for 2 hours. These data were then used to measure dopamine transporters by operationally defined ratio methods of (BG-OCC)/OCC at 2 hrs, binding potential R_v=k_3/k4 using graphic method or R_A=(ABBG-ABOCC)/ABOCC for 2 hrs, where ABBG represents accumulated binding activity in basal ganglia (∫^120min₀ BG(t)dt) and ABOCC represents accumulated binding activity in occipital cortex (∫^120min₀ OCC(t)dt). The purpose of this study was to examine the IPT pharmacokinetics and investigate the usefulness of simplified methods of (BG-OCC)/OCC, R_A, and R_v which are often assumed that these values reflect the true values of k₃/k₄. The rate constants K₁, k₂, k₃ and k₄ to be used for simulations were derived using [I-123]IPT SPECT and aterialized blood data with a standard three compartmental model. The sensitivities and time activity curves in BG and OCC were computed by changing K₁ and k₃(only BG) for every 5 min over 2 hours. The value (BG-OCC)/OCC, R_A, and R_v were then computed from the time activity curves and the linear regression analysis was used to measure the accuracies of these methods. The rate constants K₁, k₂, k₃, k₄ at BG and OCC were 1.26±5.41%, 0.044±19.58%, 0.031±24.36%, 0.008±22.78% and 1.36±4.76%, 0.170±6.89%, 0.007±23.89%, 0.007±45.09%, respectively. The Sensitivities for ((ΔS/S)/(Δk₃/k₃)) and ((ΔS/S)/(ΔK₁/K₁)) at 30 min and 120 min were measured as (0.19, 0.50) and (0.61, 0.23), respectively. The correlation coefficients and slopes of ((BG-OCC)/OCC,R_A, and R_V) with k₃/k₄ were (0.98, 1.00, 0.09) and (1.76, 0.47, 1.25), respectively. These simulation results indicate that a late [I-123]IPT SPECT image may represent the distribution of the dopamine transporters. Good correlations were shown between (BG-OCC)/OCC, R_A or R_v and true k₃/k₄, although the slopes between them were not unity. Pharmacokinetic computer simulations may be a very useful technique in studying dopamine transporter systems