Katelyn Nye, Presenter: Employee, General Electric Company

John M. Sabol PhD, Abstract Co-Author: Employee, General Electric Company

Digital tomosynthesis (DTS) is increasingly used clinically as a low-dose tomographic imaging technique. It has been demonstrated to enable increased detection of lung nodules and aid in patient management, in particular for suspicious nodules seen on chest x-ray. This study examines the contrast and noise performance of DTS for a wide range of radiographic techniques and doses to optimize performance for the lung nodule detection task.

Chest DTS images of a medium adult chest phantom with 6 simulated lung nodules of various diameters (8 to 12mm) and attenuations (-800 to 100HU) were acquired using 72 different combinations of mAs; copper filtration (0.0, 0.1, and 0.3mm), and kVp (100 to 150kVp in steps of 10kVp). With 60 projection views and fixed kVp techniques, mAs parameters were determined by the AEC from the scout image. The total incident air kerma (IAK) was measured for each technique enabling Monte Carlo estimation of effective dose. The raw reconstructed DTS images were analyzed for the central slice through each nodule. Uniform regions of interest were selected for nodules and their neighboring backgrounds. CNR was calculated for each exam and nodule.

The lowest dose technique utilized 0.25mAs per projection, 0.3mm Cu filtration, and 100kVp resulting in 0.15mGy incident air kerma. mAs selection was observed to have minimal effect on dose, compared to copper filtration and kVp selection as a result of the use of minimal mAs techniques for each projection view for the medium adult sized phantom. As total IAK decreased, the CNR /sqrt(dose) increased, without reaching a maxima, for all nodules and techniques. This CNR behavior indicates that for the lung nodule imaging task, the DTS system is not dose-limited.

For routine clinical chest imaging techniques, there is potential to further reduce patient dose while maximizing CNR/sqrt(dose) by decreasing the incident air kerma beyond the capabilities of the current DTS system. After minimal dose acquisition techniques have been determined, there may be further opportunity to reduce dose, without sacrificing image quality, through the use of optimized reconstruction techniques.

Digital tomosynthesis is a low dose imaging technique that can improve lung nodule detection, there is opportunity to further reduce dose without sacrificing relative contrast to noise performance.

Nye, K, Sabol, J, Examination of the Contrast, Noise, and Dose Performance of Chest Digital Tomosynthesis for the Detection of Lung Nodules.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014257.html