Abstract
Digital tomosynthesis (DTS) was evaluated as an alternative to cone‐beam computed tomography (CBCT) for patient setup. DTS is preferable when there are constraints with setup time, gantry‐couch clearance, and imaging dose using CBCT. This study characterizes DTS data acquisition and registration parameters for the setup of breast cancer patients using nonclinical Varian DTS software. DTS images were reconstructed from CBCT projections acquired on phantoms and patients with surgical clips in the target volume. A shift‐and‐add algorithm was used for DTS volume reconstructions, while automated cross‐correlation matches were performed within Varian DTS software. Triangulation on two short DTS arcs separated by various angular spread was done to improve 3D registration accuracy. Software performance was evaluated on two phantoms and ten breast cancer patients using the registration result as an accuracy measure; investigated parameters included arc lengths, arc orientations, angular separation between two arcs, reconstruction slice spacing, and number of arcs. The shifts determined from DTS‐to‐CT registration were compared to the shifts based on CBCT‐to‐CT registration. The difference between these shifts was used to evaluate the software accuracy. After findings were quantified, optimal parameters for the clinical use of DTS technique were determined. It was determined that at least two arcs were necessary for accurate 3D registration for patient setup. Registration accuracy of 2 mm was achieved when the reconstruction arc length was > 5° for clips with HU ≥ 1000°; larger arc length (≥ 8°) was required for very low HU clips. An optimal arc separation was found to be ≥ 20° and optimal arc length was 10°. Registration accuracy did not depend on DTS slice spacing. DTS image reconstruction took 10–30 seconds and registration took less than 20 seconds. The performance of Varian DTS software was found suitable for the accurate setup of breast cancer patients. Optimal data acquisition and registration parameters were determined.PACS numbers: 87.57.‐s, 87.57.nf, 87.57.nj
Highlights
61 Ng et al.: Breast cancer patient setup using Varian Digital tomosynthesis (DTS) software the setup of breast cancer patients is using surrogates such as surgical clips in the vicinity of the tumor cavity.[3,4,5,6] Breast cancer patient setup using surgical clips with kV radiography has been demonstrated to be beneficial.[6,7] the visibility of the clips in orthogonal kV radiographs strongly depends on the type of clip used and distance from the rib cage, the gantry orientation, and the appearance of overlying structures/hardware.[8]
61 Ng et al.: Breast cancer patient setup using Varian DTS software the setup of breast cancer patients is using surrogates such as surgical clips in the vicinity of the tumor cavity.[3,4,5,6] Breast cancer patient setup using surgical clips with kV radiography has been demonstrated to be beneficial.[6,7] the visibility of the clips in orthogonal kV radiographs strongly depends on the type of clip used and distance from the rib cage, the gantry orientation, and the appearance of overlying structures/hardware.[8]. Our earlier study[8] showed that small clips (Horizon ligating clips, Teleflex Medical, Research Triangle Park, NC) and those that were placed close to the chest wall are less detectable in a kV radiograph
When clip localization with orthogonal kV radiographs is not feasible, cone-beam CT (CBCT) may be used.[9,10,11] there are two major drawbacks associated with the use of CBCT for a breast cancer patient’s setup: possible collision between the gantry head and the patient or couch, and relatively high imaging dose to the whole thorax.[12,13,14,15,16] In another earlier study,(15) depending on the placement of the imaging isocenter, five of eight breast cancer patients (63%) treated in the supine position were at risk of potential gantry collision during imaging
Summary
61 Ng et al.: Breast cancer patient setup using Varian DTS software the setup of breast cancer patients is using surrogates such as surgical clips in the vicinity of the tumor cavity.[3,4,5,6] Breast cancer patient setup using surgical clips with kV radiography has been demonstrated to be beneficial.[6,7] the visibility of the clips in orthogonal kV radiographs strongly depends on the type of clip used (density, size, and material) and distance from the rib cage, the gantry orientation, and the appearance of overlying structures/hardware.[8]. Other complicating factors include clips that overlap along the beam projectory, high-density structures (ribs or hardware), and scatter from the patient’s body that creates too much noise for visualization of the clips. When clip localization with orthogonal kV radiographs is not feasible, cone-beam CT (CBCT) may be used.[9,10,11] there are two major drawbacks associated with the use of CBCT for a breast cancer patient’s setup: possible collision between the gantry head and the patient or couch, and relatively high imaging dose to the whole thorax.[12,13,14,15,16] In another earlier study,(15) depending on the placement of the imaging isocenter, five of eight breast cancer patients (63%) treated in the supine position were at risk of potential gantry collision during imaging. A restraint system, if used, might increase the occurrence of gantry collision as the restraint system would extend beyond the patient’s body
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
