Robert Davidson
University of Canberra, Australia
Title: Contrast-Detail Measurements in CT – A New Image Quality Evaluation Methodology
Biography
Biography: Robert Davidson
Abstract
Rationale: The essential principle of maintaining lower radiation dose and optimum image quality is to understand the effects of exposure factors on image quality. The evaluation method of low contrast detail (LCD) detectability performance—particularly the automated approach—is a good choice for deep understanding the influences of exposure parameters on image quality. However, this method requires a certain specification of an LCD phantom and dedicated software that are not commercially available. The study aimed to develop a new methodology of evaluation and optimisation of computed tomography (CT) image quality based on LCD detectability performance.\\r\\nMethodology: A new phantom was designed to obtain CT images of LCD. The specifications of the phantom design were optimised to satisfy the requirement of the new evaluation methodology of LCD detectability performance and based on evaluation of the limitations of available phantoms and the standard recommendations of phantom manufacturing. The phantom was manufactured with the cooperation of Artinis Medical Systems (Zetten, The Netherlands). A dedicated software was developed with the cooperation of Artinis Medical Systems to objectively evaluate the obtained CT images of the new phantom. The LCD detectability performance of CT images were measured by calculating the CT inverse image quality figure (CT IQFinv). The new methodology was validated by determining the influences of exposure factors of kVp and mAs, slice thicknesses and objects location within the phantom on the image quality in terms of CT IQFinv measurements. The validation was based on software and radiographers’ scoring results. \\r\\nResults: A new method of calculating the IQFinv values for CT images, CT IQFinv, was developed based on the method of calculating the IQFinv in digital radiography (Equation 1). A further requirement was the linear interpolation of the Hounsfield Units of the phantom’s objects to account for both positive and negative contrast values. \\r\\n