TH‐C‐ValB‐05: Rapid Low‐Dose 3D Image‐Guided Treatment Verification of Sites Prone to Respiratory Motion Using Breath‐Hold On‐Board Digital Tomosynthesis (DTS)

Abstract

Purpose: This study examines the potential use of on‐board digital tomosynthesis (DTS) for image‐guided treatment verification of sites prone to respiratory motion. DTS is a fast, low‐dose method for reconstructing 3‐ D images from 2‐D projection data, acquired with a limited scan angle. In the treatment room, a 45° DTS scan can be acquired in less than 10 seconds, making rapid breath‐hold DTS a simple method for acquiring 3‐D treatment verification images, devoid of respiratory motion. Method and Materials: On‐board DTS images of ten human liver, pancreas, and lung subjects were reconstructed from kV CBCT projection data, acquired on a Varian 21EX Clinac equipped with an on‐board imager (OBI), either during a breath‐hold or while subjects were freely breathing. Corresponding reference DTS (RDTS) images were reconstructed from breath‐hold planning CT data. Soft‐tissue visibility was compared between breath‐hold DTS and free‐breathing DTS and CBCT, to assess the potential efficacy of the breath‐hold DTS strategy for 4‐D image‐guided treatment verification. Results: Breath‐hold DTS markedly improved the rendering of soft‐tissue abdominal and thoracic anatomy, compared with free‐breathing DTS or CBCT. Organ structures were clearly defined, and even low‐contrast target malignancies were often visible in breath‐hold DTS reconstructions. Free‐breathing DTS and CBCT reconstructions, on the other hand, often exhibited artificially enlarged target volumes and poor visibility of soft‐tissue anatomy, due to motion averaging effects. Conclusion: Rapid breath‐hold DTS enhances the visibility of bony and soft‐tissue anatomy in sites prone to respiratory motion, facilitating daily localization of soft‐tissue targets. Breath‐hold DTS localization is superior to free‐breathing on‐board CBCT for thoracic and abdominal image‐guidance. Conflict of Interest: This research was supported in part by a grant from Varian Medical Systems.