Markerless motion tracking of lung tumors using dual‐energy fluoroscopy

Abstract

This work indicates the potential for markerless tumor tracking utilizing DE fluoroscopy. With DE imaging, the algorithm showed improved detectability vs SE fluoroscopy and was able to accurately track the tumor in nearly all cases.

Feasibility of markerless tumor tracking by sequential dual-energy fluoroscopy on a clinical tumor tracking system

“…Improved contrast of lung lesions after DE subtraction, resulting in significant improvement in markerless tumor localization, has been reported by several groups [16][17][18][19]. In this study, we evaluate the feasibility of markerless tumor tracking through the implementation of DE subtraction imaging into the current clinical RTTT workflow, using the implanted fiducials as a benchmark.…”

“…one imaging angle, a normalized cross-correlation (NCC) algorithm with an ad-hoc 200 Â 200 pixel region-of-interest (ROI), including sufficient patient anatomy, was applied to find the best-matching HE image for each LE image [17]. After LE-HE image matching, all LE-HE image couples were allocated to their respective breathing phase (inhale, exhale, maximum inhale and maximum exhale) based on the amplitude of the external breathing signal and synchronized timestamps.…”

Evaluation of a template-based algorithm for markerless lung tumour localization on single- and dual-energy kilovoltage images

“…Energies for DE imaging were selected based on previous studies where image quality and dose were optimized. 30,[43][44][45] A prior study demonstrated that the estimated mean dose at the skin per DE image pair was approximately 0.44 6 0.03 mGy, comparable with the expected skin dose from conventional SE imaging. 30 Image pairs were acquired once per treatment fraction with a maximum of five sets per patient.…”

“…Our previous study showed that the average displacement between the two physician's ground truth co-ordinates was 1.0 6 0.8 mm. 44 If more physicians were involved in the process, a more precise determination of ground truth may be possible. Additionally, this study uses a template-matching algorithm that is not yet commercially available and therefore this system cannot yet be employed in clinics without access to the software.…”

“…Using these images, a weighted logarithmic subtraction is performed that removes obscuring bony anatomy (ribs and vertebral bodies), thus creating a third image that highlights soft tissue, such as lung tumours. 30,43,44 Recently, Sherertz et al 30 published a prospective feasibility study investigating tumour visibility in DE radiographs compared with conventional kV radiographs used in image-guided radiation therapy of patients with lung cancer. In that study, obscuring bony anatomy was successfully removed in all analyzed DE images, and tumour visibility was improved when compared with conventional radiographs.…”