Measurement Standardized Uptake values By Single Photon Emission Computed Tomography

Abstract

ABSTRACT In the last few decades, a huge improvement and development has been applied for all medical imaging systems. At Nuclear Medicine, Single Photon Emission Computed Tomography (SPECT) systems have been developed to be an integrated with Computed Tomography (CT) as one modality. Many factors play major role in quantitative accuracy of SPECT images. One of these factors is using of photon attenuation correction (AC) technique from the generated CT attenuation map. As a result of using AC, the spatial accuracy of the system will be enhanced, which will add more value to the quantitative accuracy of SPECT images. In this study, enhancement of the spatial resolution has been utilized to quantify the values of the Recovery Coefficient (RC) for different object sizes surrounded with high concentration activity and then apply this factor to calculate the standardized uptake values (SUV).The aim of this study is to calculate the (Standardized Uptake values) SUV in SPECT/CT systems which is using relatively long half-life radioisotopes compared with the isotopes used in PET/CT systems. This would increase the diagnostic efficiency especially in the low-income countries that cannot afford such technologies. This will also enable the users to use SUV which is not used yet in SPECT/CT clinical practice due to the quantitative limits. Study Problem: SPECT images are known with their low quantitative and spatial accuracy which led to a problem with applying SUV to these studies. These images were not designed from the beginning of their creation to produce images in units of (kBq.ml-1). Several factors may cause this problem; they may include device sensitivity, dead time of the isotope used, as well as spatial accuracy in addition to photon attenuation and dispersion. All these factors make quantization in SPECT difiicult to achieve unlike as in PET. PET image reconstruction is using accurate corrections to quantify the activity since its initiation Methodology: The SPECT/CT system sensitivity has been measured to convert the collected photon counts to the relative activity. The SUV has been corrected using the calculated RCfor the used SPECT/CT system for different volumes and different matrixes by using NEMA IEC Body phantom. The study concluded that, the accuracy of SUV measurement depends on the size of the object volume and the matrix size, using l28>< 128 matrix size was the ideal setup to be used for clinical practice. These calculations would clear the path for more research to develop new methods of this important field. It would also guide the researchers in the software development to improve the quantitative quality of the generated SPECT images and the application of this technique clinically.