Purpose: Cardiac radioablation is a promising treatment for cardiac arrhythmias, but accurate dose delivery can be affected by heart motion. For this reason, real-time cardiac motion monitoring during radioablation is of paramount importance. Real-time ultrasound (US) guidance can be a solution. One of the possible workflow steps with this approach is simultaneous US-CBCT acquisition, which can result in US transducer induced metal artifacts on the CBCT scans. To reduce their impact, a new metal artifact reduction (MAR) algorithm, named Combined Clustered Scan-based MAR (CCS-MAR) has been developed and compared to Metal Deletion Technique (MDT) provided by ReVision Radiology.
Methods: A CIRS (Model 002LFC) thorax phantom was CBCT scanned with and without a Philips VL 13-5 US transducer, resulting in artifacts and reference scans, respectively. Then, the MAR algorithms were applied producing a corrected scan. The mean absolute differences (MAD) in HU values, structural similarity (SSIM) and Signal-to-Noise Ratio (SNR) were calculated for artifacts and corrected scans compared to the reference scan.
Results: The calculated MAD in HU values were lower for the corrected scans than for the artifacts scans. For example, in the heart region, for the artifacts scan the MAD was 68 HU, which was reduced in the corrected scans to 23 HU and 27 HU, after CCS-MAR and MDT applications, respectively. The SSIM values for the artifacts scan and for the corrected scan after CCS-MAR and MDT applications were 0.66, 0.86, and 0.81, respectively. The calculated SNR value for the artifacts scan was 27.26 and it improved to 29.62 after CCS-MAR, and to 30.03 after MDT application.
Conclusion: The application of MAR algorithms reduces the negative impact of US transducer-induced metal artifacts on CBCT scans. In comparison to MDT, CCS-MAR application on CBCT scans performs better or comparably in reducing these metal artifacts.
Cone-beam CT, Radiosurgery, Image Guidance
IM/TH- Cone Beam CT: Development (New Technology and Techniques)