Experimental evaluation of absolute quantification in Tc-TRODAT-1 SPECT/CT brain dopamine transporter (DAT) studies.

Objective: To evaluate the quantitative accuracy of clinical brain dopamine transporters (DAT) investigations utilizing Tc-TRODAT-1 single-photon emission computed tomography (SPECT)/computed tomography (CT) in experimental and clinical settings.

Materials And Methods: The study used an experimental phantom evaluation and a clinical dataset. Three-dimensional-ordered subsets expectation-maximization reconstructed the original and resampled datasets using attenuation correction, scatter correction, and resolution recovery. The reconstructed data were analyzed and reported as percentage difference, standardized uptake value reference (SUVr), and a coefficient of variation (CoV). The Taguchi method tested the impact of the three different parameters on signal-to-noise ratio (SNR) and SUVr, including number iteration, Poisson resampling, and phantom setup, with and without the plaster of Paris (POP). Six Tc-TRODAT-1 SPECT/CT scans were acquired in healthy subjects for verification purposes.

Results: The percentage activity difference between the phantom with and without POP is 20% and 5%, respectively. The SUVr reveals a 10% underestimate for both with and without POP. When it comes to the influence of Poisson resampling, the SUVr value for 75% Poisson resampling indicates 10% underestimation on both sides of the caudate and putamen area, with and without POP. When 25% of Poisson resampling is applied, the SUVr value is overestimated (±35%). In the Taguchi analysis, iteration numbers were the most dominant factor with the F-value of 9.41 and the contribution rate of 52.66% (p < 0.05) for SNR. In comparison, F-value of 9.1 for Poisson resampled with contribution rate of 58.91% (p < 0.05) for SUVr. Reducing counts by 25% from the original dataset resulted in a minimal bias in SUVr, compared to 50% and 75%.

Conclusion: The optimal absolute SPECT/CT quantification of brain DAT studies using Tc-TRODAT-1 appears achievable with at least 4i10s and SUVr as the surrogate parameter. In clinical investigations, it is possible to reduce the recommended administered dose by up to 25% while maintaining accurate measurement.