CT image quality metrics implementation during thorax SPECT/CT clinic studies

Abstract

In hybrid studies, the total patient’s radiation dose and the image’s quality are the results of the two technologies. This work studied the implementation and evaluation of some CT image´s quality metrics like noise,  contrast to noise ratio (CNR) and resolution through the half maximum (FWHM) of  different anatomical structure, and their preliminary relationship with patient’s radiation dose parameters including the volume CT dose index (CTDIvol), dose-length product (DLP), and size-specific dose estimate (SSDE), during thorax clinical studies, in a Mediso SPECT/CT equipment. 20 clinical SPECT/CT studies were analyzed using a homemade computed subroutine.   The SSDE preliminary result were between 2,6-23,6mGy. The different thorax structures typical noise varied from 2,1 to 42,3% among patient, showing very different behaviors between different tissues, example lungs and esophagus had average noise less than 5%. The CNR showed statistical difference between studies, varying from 1 to 57. The same structure FWHM estimation ranged between 14,8-50,5% during different studies, showing statistical differences. The SSDE and FWHM showed a statistically significant Pearson correlation coefficient of -0,454 (p=0,045). Conclusions: the SSDE inversely correlated with some of studied CT image´s quality metrics.  The FWHM clinical estimation of different anatomical structure is viable and showed the capability to detect image characteristic which could be direct related with their quality and clinical analysis.