Evaluation of respiration‐correlated digital tomosynthesis in lunga)

Abstract

Digital tomosynthesis ͑DTS͒ with a linear accelerator-mounted imaging system provides a means of reconstructing tomographic images from radiographic projections over a limited gantry arc, thus requiring only a few seconds to acquire. Its application in the thorax, however, often results in blurred images from respiration-induced motion. This work evaluates the feasibility of respirationcorrelated ͑RC͒ DTS for soft-tissue visualization and patient positioning. Image data acquired with a gantry-mounted kilovoltage imaging system while recording respiration were retrospectively analyzed from patients receiving radiotherapy for non-small-cell lung carcinoma. Projection images spanning an approximately 30°gantry arc were sorted into four respiration phase bins prior to DTS reconstruction, which uses a backprojection, followed by a procedure to suppress structures above and below the reconstruction plane of interest. The DTS images were reconstructed in planes at different depths through the patient and normal to a user-selected angle close to the center of the arc. The localization accuracy of RC-DTS was assessed via a comparison with CBCT. Evaluation of RC-DTS in eight tumors shows visible reduction in image blur caused by the respiratory motion. It also allows the visualization of tumor motion extent. The best image quality is achieved at the end-exhalation phase of the respiratory motion. Comparison of RC-DTS with respiration-correlated cone-beam CT in determining tumor position, motion extent and displacement between treatment sessions shows agreement in most cases within 2-3 mm, comparable in magnitude to the intraobserver repeatability of the measurement. These results suggest the method's applicability for softtissue image guidance in lung, but must be confirmed with further studies in larger numbers of patients.

Digital tomosynthesis (DTS) for verification of target position in early stage lung cancer patients

“…24 In addition, we found the DTS registration accuracy to be consistent with the threshold of 2 mm sug-gested by Ren et al 25 Our DTS image reconstruction method is in broad agreement with the method of Godfrey et al 26 However, in our study the AvIP from the planning 4DCT, which also contains time averaged data, was used to generate Reference-DTS images. This may explain the acceptable performance of DTS.…”

Estimating 4D‐CBCT from prior information and extremely limited angle projections using structural PCA and weighted free‐form deformation for lung radiotherapy

“…4D Cone-beam CT (CBCT) and 4D digital tomosynthesis (DTS) have been developed recently to provide on-board 4D localization of moving targets. [7][8][9][10][11][12][13][14][15][16][17] Conventional 4D-CBCT reconstructed by the Feldkamp-Davis-Kress (FDK) algorithm requires the acquisition of 4D projections over a full rotation angle. This leads to long acquisition time (~a few minutes) and high imaging dose to patients (~2 cGy at isocenter and skin dose~1 À3.5 cGy).…”

A technique for estimating 4D‐CBCT using prior knowledge and limited‐angle projections

“…[7][8][9][10][11][12][13] and 4D digital tomosynthesis (4D-DTS) (Refs. [14][15][16][17] have been developed recently for localization of moving targets. Both methods use retrospectively sorted full-angle (4D-CBCT) or limited-angle (4D-DTS) cone-beam projections to reconstruct respiratoryphase-resolved 3D volumes through the Feldkamp-Davis-Kress (FDK) algorithm.…”