Purpose: To implement the first clinical model-based CT simulation system employing the 5D motion model.
Methods: We recently started the clinical implementation of the 5DCT simulation protocol. The protocol utilizes a combination of free-breathing helical CT and simultaneous breathing monitoring. The breathing is monitored by an abdominal bellows tube synchronized to CT acquisition. 25 low-mAs helical scans are acquired, and the breathing amplitude and rate are assigned to each CT slice. The first CT scan is defined as the reference scan and the other 24 scans are deformably mapped to it, providing 25 locations for each reference image voxel. The positions are coupled with the breathing amplitudes and rates to fit a voxel-specific motion modeling equation. A representative breath is defined using an average breathing period and amplitude to enable the generation of inhalation and exhalation images. Eight CT images are prepared, from the 5th percentile amplitude (defined as exhalation), through the 85th percentile amplitude (defined as inhalation) and back. To assure the process provides quantitative phase-specific images, the original 25 CT scan geometries are simulated using the motion model and the simulated and original scans are compared.
Results: The 5DCT simulation protocol was built using workflows and techniques developed over the past 12 years. We conducted a TG-100 based safety review of the software and workflow and placed the protocol into clinical use in early 2019. The protocol provides, for the first time, sorting artifact-free, low stochastic noise, CT images of free-breathing patients at quantitatively defined breathing amplitudes.
Conclusion: A significant improvement to the commercial 4DCT workflow has been accomplished using a modern but conventional CT multislice scanner, a pneumatic bellows with voltage sensor, and a workflow that provides sorting-artifact-free images even for irregular breathing patients.
Not Applicable / None Entered.