Energy Window Optimization Using Triple Energy Window Scatter Correction Method for In-111 SPECT Imaging: A SIMIND Monte Carlo Study

Detecting scattered photons in the photo peak window degrades the image contrast and quantitative accuracy of single-photon emission computed tomography (SPECT) imaging. This study aimed to determine optimal main- and sub-energy windows for Triple Energy Window (TEW) in In-111.
We used the simulating medical imaging nuclear detectors (SIMIND) program to simulate the Siemens SYMBIA gamma camera equipped with a medium energy (ME) collimator. We also used the SIMIND Monte Carlo program to generate theIn-111SPECT projection data of the Jaszczak phantom. The phantom consisting of six spheres with different diameters (9.5, 12.7, 19.1, 15.9, 25.4, and 31.8 mm) was used to evaluate the image contrast. Geometric, scatter, and penetration fraction, point spread functions, and contrast curves were drawn and compared.
The results showed that the 171keVphotopeak compared to the 245keVphotopeak yielded the best results with an ME collimator when the TEW scatter correction method was applied. The reason can be the large amount of scatter and penetration from the photo peak and the collimator for the 245keVphotopeak window.
With the TEW scatter correction method, it is better to use a 171keVphotopeak window because of its better spatial resolution and image contrast.