Quality Control of CT Scanners

The system NECR is computed as the sum of NECRs for all slices. These values for some PET scanners are shown in Table 6.1. 

The percent dead time count loss (%DT) as function of activity is calculated by 

An important parameter, CT dose index (CTDI, defined as the cumulative dose along the patient s axis for a single tomographic image), should be evaluated at least semiannually at different values of kVp and mA. It is measured by using an ionization chamber or a thermoluminescent dosimeters placed in a tissue-equivalent acrylic phantom simulating head or body. ACR (2007) recommends maximum doses CTDI) of 6 rad (60 mGy) for brain, 3.5 rad (35 mGy) for adult abdomen and 2.5 rad (25 mGy) for pediatric (5-year-old) abdomen. The details of these measurements are available in standard CT physics books. 

The typical transaxial resolution at 1 cm of a PET scanner ranges between 

What are the common factors that affect the spatial resolution of a PET scanner Out of these, which one is most predominant  

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