Author: Nawal Alqethami, Felix Ginzinger, Prasannakumar Palaniappan, Marco Riboldi, Philipp Steininger, Wentao Xie 👨🔬
Affiliation: Research & Development, medPhoton GmbH, Department of Medical Physics, Ludwig-Maximilians-Universität (LMU) München, Department of Medical Physics, Ludwig-Maximilians-Universität München (LMU Munich) 🌍
Purpose:
This study evaluates the image quality of Dual-Energy (DE) X-ray imaging for lung tumor tracking across various sizes and protocols, comparing its imaging dose to Single-Energy (SE) imaging.
Methods:
We developed an in-house setup using pork ribs mounted on a cylinder, with a holder for artificial tumors. Six spherical tumors (0.5–3.0 cm) underwent DE planar scans with fast kV switching (300 frames at 11.9 fps). These scans used 60 kV/17 ms paired with 120 kV/12 ms and 80 kV/17 ms paired with 120 kV/12 ms, each at 15 and 20 mA. SE scans were acquired for comparison using the same parameters.
A weighted logarithmic subtraction procedure was applied, to suppress the bones and enhance the tumor contrast, with weighting factors (wst) ranging from 0.55 to 0.7, in increments of 0.01.
The contrast-to-noise ratio (CNR) was calculated to assess the image quality by calculating the CNR between the tumor segmentation and the background. The imaging dose rate was evaluated by measuring the Dose-Area-Product (DAP) for all DE scans, and comparing it to the SE scans.
Results:
The optimal wst ranged from 0.78 to 0.79 for the 80/120 KV and 0.56 to 0.61 for the 60/120 KV in both current settings. Increasing the mA from 15 to 20 improved the CNR by 5% for 80/120 kV and 6% for 60/120 kV for the DE images.
The lowest DE dose rate (0.063 mGy/sec) was achieved using 60/120 kV at 15 mA. Increasing the kV to 80 elevated the dose by 22%, while increasing the mA to 20 increased it by 28%. SE scans at 120 kV resulted in the highest dose, due to sustained high-energy exposure throughout the scan.
Conclusion:
This study demonstrates DE imaging effectiveness in enhancing lung tumor tracking compared to SE imaging, balancing radiation dose and image quality.