Development and quantitative assessment of a beam hardening correction model for preclinical micro-CT

Recommended Citation Mohapatra, Sucheta. "Development and quantitative assessment of a beam hardening correction model for preclinical micro-CT." MS his contributions of time, ideas, and funding to make my graduate study experience so productive and stimulating. accomplishments shall continue to inspire me towards my future goals. I owe a lot to all my friends and colleagues in Iowa City, who have stood by me in the best and worst of times, and made my life here, a joyful and learning experience. I am grateful to my parents, Sabita Mohapatra and Kailash Chandra Mohapatra, for their unflagging love and support, even when I am thousands of miles away. I am forever indebted to my father, who has spared no effort to provide me the best possible education despite all the hardships and financial constraints. Thanks to my brother, Shakti, who I grew up with a passion for Science. Finally, I am thankful to my beloved husband, Dr. Chandra Shekhar Mohapatra, for his unwavering faith in me, wealth of ideas, sparkling humor and for being the very special person that he is. iv ABSTRACT The phenomenon of x-ray beam hardening (BH) has significant impact on preclinical micro-CT imaging systems. The causal factors are the polyenergetic nature of x-ray beam used for imaging and the energy dependence of linear attenuation coefficient ation of beam in the imaged object, lower energy photons in the projected beam become preferentially absorbed. The penetrating, causing underestimation of the linear attenuation coefficient. When this phenomenon is not accounted for during CT reconstruction, it results in images with non-uniform CT number values across regions of uniform density. It leads to severe errors in quantitative applications of micro-CT and degradation in diagnostic quality of images. Hence, correction for beam hardening effect is of foremost importance and has been an active area of research since the advent of-CT [2][3][4]. The Inveon-CT system uses a common linearization approach for BH correction. It provides a set of standard default coefficients to be applied during CT reconstruction. However, our initial experiments with uniform water phantoms of varying diameters indicated that the correction coefficients provided by default in the Inveon system are applicable for imaging mouse-size (~28 mm) objects only. For larger objects observed in the uniform central region of the phantom. This study provides an insight into the nature and characteristics of beam hardening on the Inveon CT system using water phantoms of varying sizes. …