2983 - Triggered Spectral kV Imaging for Real-Time Intrafraction Bone Tracking Using a Novel Dual-Layer kV Imager

12:30pm - 01:45pm ET

Poster Hall - Exhibit Hall A

Screen: 17

POSTER

Presenter(s)

Francois De Kermenguy, PhD - Brigham and Women's Hospital, Cambridge, MA

F. De Kermenguy¹, M. Jacobson¹, Y. H. Hu¹, N. Lowther¹, R. Etemadpour¹, T. C. Harris¹, G. C. Sharp², B. Vecchione¹, M. Myronakis¹, M. Lehmann³, V. Birrer³, R. Fueglistaller³, P. Corral Arroyo³, R. Bruegger³, R. I. Berbeco¹, and D. Ferguson¹; ¹Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, ²Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, ³Varian Medical Systems, Baden-Dattwil, Switzerland

Purpose/Objective(s):

Intrafraction motion during ablative bone SBRT can compromise target coverage and organ-at-risk sparing due to steep dose gradients and millimeter-scale PTV margins. Conventional triggered kV imaging may be limited by suboptimal image quality, reducing alignment confidence during beam delivery. A novel dual-layer spectral kV imager enables rapid, energy-resolved triggered acquisition with material decomposition to generate bone-only projections. We evaluated the geometric accuracy and registration performance of triggered spectral kV imaging for direct intrafraction bone motion monitoring.

Materials/Methods:

A phantom study was performed to benchmark bone-tracking performance using triggered images acquired with the dual-layer imager (DLI). Following initial setup of an anthropomorphic pelvis phantom, triggered projections were acquired at 10-degree gantry intervals. From each DLI acquisition, two image sets were generated: (1) a top-layer image equivalent to a conventional clinical kV panel and (2) a bone-only image derived from combined top- and bottom-layer spectral decomposition using a bespoke algorithm developed for the DLI. Each image set was registered to digitally reconstructed radiographs and residual translational and rotational differences relative to known applied shifts were quantified.

Results:

Spectral bone-only imaging enabled high-confidence registration from single triggered projections. In preliminary phantom evaluation, bone-only images demonstrated reduced the mean translational offset from 8.0 mm to 2.8 mm and rotational offset from 1.5° to 0.7° compared with conventional triggered kV images.

Conclusion:

Triggered dual-layer spectral kV imaging provided high-contrast visualization of treated bony anatomy during beam delivery and improved positional accuracy relative to standard triggered kV imaging in phantom testing. These findings support dual-layer spectral imaging as a promising approach for intrafraction geometric verification in high-precision bone SBRT.

	X Registration Offset	Y Registration Offset	Pitch Registration Offset
Phantom	µ ± s [mm]	µ ± s [mm]	µ ± s [deg]
Top-layer kV (clinical equivalent)	-2.6 ± 32	-8.4 ± 48	1.5 ± 3.5
Bone Decomposed	2.5 ± 8.1	-1.4 ± 8.0	0.7 ± 1.4