Investigation of the impact of table positioning, protocol adjustments, and internal shielding on CT image quality, organ doses, and organ dose calculations in postmortem subjects.

摘要

Multiple dose reducing systems and methods for CT imaging results in vast variability in implementing this imaging modality. In this work the clinical variability of CT use was investigated. This was completed through retrospective investigation of the frequency of miscentering, subjective image quality assessment and postmortem organ dosimetry measurements for investigating miscentering and tube potential variations, retrospective investigation of the implementation of iterative reconstruction for dose savings to the highly irradiated kidney-stone-positive population, development of a new patient metric describing the thickness of adipose tissue surrounding the core of the anatomy and its possible use in organ dose modeling, and further development of previously established organ dose models and the clinical application to different detector row configurations, reconstruction algorithms, varied protocol types and clinically relevant variability.;The results showed misalignment of the patient center to isocenter in any direction occurred 75 out of 80 times in the clinic. No diagnostic quality differences were observed from these centering errors. Organ doses increased as much as 8mGy for AP and 1.5mGy for lateral miscentering. Tube potential variations revealed a preference for 100 kV energy levels and clinical indications proved to be the key for the overall application of tube potential variations with a dose savings up to 8mGy. The retrospective application of previously established organ dose estimation equations resulted in the quantified organ dose savings to different sized kidney stone forming patients with a maximum dose savings of 58mGy to the skin possible for larger sized patients from using iterative reconstruction techniques. The novel adipose tissue thickness metric developed was used for modeling organ dose estimation proving to be statistically promising but limited by the number of applicable subjects. The size-specific organ dose estimate equation set produced proved to traverse all investigated clinical variations and was applicable across protocol types.;CT acquisition techniques and parameters vary greatly. With the proper investigation of image quality paired with organ dose quantification, these variations can be utilized to optimize patient outcomes. The size-specific organ dose estimation equations make it possible to investigate these variations in living patients resulting in a method for patient outcome optimization.