Diastolic function assessments using 16-frame 201Tl-gated myocardial perfusion SPECT was made by Nagamichi et al. [1]. The time-to-peak filling (TTPR) in no-defect group is 195.8 ± 97.6 ms by using QGS software. On the other hand, TTPR obtained by 99mTc, which is reported by Japanese Society of Nuclear Medicine, is 167 ± 38 ms in all the subjects (aged 58 ± 15) [2]. The other reports from US shows TTPR is 165 ± 22 ms [3]. The values obtained by 201Tl (195 ± 97.6 ms) is not only higher but also has a bigger standard deviation, indicating the limitation of the measurement by 201Tl acquisition at 15 s per projection and 16 frames per R–R interval. Quantitative measurement depends on the type of radionuclide used. It is expected that 201Tl images will be more blurred than 99mTc images, due to both to increased account of Compton scatter associated with 201Tl and the use of a smoother pre-reconstruction filter.

Keen investigation to establish the standard of diastolic function by nuclear technique is absolutely needed.