Fluctuation of quantitative values on acquisition time and the reconstruction conditions in 99mTc-SPECT

This study aims to carry out a quantitative analysis with high reproducibility using single-photon emission computed tomography/computed tomography (SPECT/CT); we investigated the optimum parameters for the acquisition and the reconstruction.

SPECT images were acquired with varying time per view using SPECT phantom (JS-10) and the body phantom of National Electrical Manufacturers Association and International Electrotechnical Commission (Body-phantom), respectively. For the image reconstruction condition, we changed the product of subset and iteration (SI product) and the Gaussian filter using a three-dimensional ordered subset expectation maximization. A combination of no scattering correction and no attenuation correction (SC-/AC-) and a combination of scattering correction and attenuation correction by CT images (SC+/AC+) were performed. The dose linearity, the recovery coefficient, the scatter ratio, and the coefficient of variation were evaluated using JS-10. Using Body-phantom, contrast-to-noise ratios of the hot spheres (13, 17 mm) were calculated. Moreover, the change in the maximum standardized uptake value (SUVmax) and the average SUV (SUVmean) were evaluated for each sphere.

From the evaluation results using the JS-10, dose linearity, recovery coefficient, scatter ratio, and coefficient of variation were all good when time per view was 50-150 s, the Gaussian filter was 8-12 mm, and the SI product was 150. From the evaluation results using Body-phantom, comparing the Gaussian filter with 8 mm and 12 mm, the contrast-to-noise ratio was better for 12 mm and the error rate to the change of the scan-time was up to 3.7%. However, SUVmax and SUVmean using 8 mm were closer to the design value of the phantom.

It is necessary that Quantitative SPECT be acquired at 50 s or more per view per detection, reconstructed using a three-dimensional ordered subset expectation maximization with SC+/AC+, the SI product is 150 times, and the Gaussian Filter is 8-12 mm. This suggested that the quantitative analysis would be carried out with good reproducibility.