Radiation dose and image-quality assessment in computed tomography

Computed tomography has experienced a number of significant technological advances over the past decade, and these have had pronounced impacts on the accuracy of radiation dosimetry and the assessment of image quality. After reviewing CT technology and clinical applications, this Report describes and discusses existing dosimetry methods and then presents new methods for radiation dosimetry, including the evaluation of beam quality, and measurement of CT-scanner output in air and in phantoms. Many of the proposed dosemetric quantities can be measured quickly using a real-time ionization chamber, which is introduced here. Traditional measurements of image quality for computed tomography rely upon simple and subjective observations. A more rigorous approach is proposed, including routine use of the modulationtransfer function for describing spatial resolution along all axes, and of the noise-power spectrum for describing the noise amplitude and texture properties of CT images. This Report focuses on new but practical methods for the assessment of radiation dose and image quality for CT scanners.