Master of Science (MS)
Physics and Astronomy
Purpose: The quality of a computed tomography (CT) image and the dose delivered depend upon the acquisition parameters used to acquire the CT scan. Current, voltage and pitch are acquisition parameters that affect the image quality. The purpose of this study was to determine the influence of current, voltage and pitch on physicians’ ability to characterize small, solid nodules with low-dose computed tomography. Methods: A database of lung scans with various acquisition parameters was compiled. A torso phantom and acrylic beads were used to simulate the lungs and nodules within the lungs. Several sizes of acrylic sphere were used to simulate different size nodules. An image visualization software was used to display the images for physicians and to assess. The physicians’ assessments were compared to known objects. The reliability of CTDI estimates reported by the CT acquisition software was verified. Results: The diameter that physician’s measured for the sphere became closer to the actual diameter of the sphere as the sphere size, tube current, and kVp increased. The pitch did not affect the physicians’ measurement of sphere size for the larger sphere as much as it did for the smaller spheres. Conclusion: We concluded that physicians are still able to judge size and shape of nodules accurately using low-dose CT. The 80 kV tube voltage proved to be an ineffective voltage for screening for lung cancer. Between the machines used there was not a substantial difference in perceived image quality when a current of 50 mA or higher was used. Based on this work, a low-dose protocol of 120 kV, 50 mA, and a pitch of 1.4 is recommended to balance patient dose and acceptable image quality.
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Williams, Kendrick J., "Assessment of detection and characterization of simulated lung nodules with low-dose CT" (2013). LSU Master's Theses. 3320.