Integrated Digital Tomosynthesis for patient positioning of image-guided radiation therapy

Abstract

Purpose: Digital Tomosynthesis (DTS), originally developed for diagnostic applications, has been recently introduced to image guided radiotherapy (IGRT). Due to limited scan range, DTS was featured by anisotropic spatial resolution. A new approach, integrated DTS (IDTS), was developed to improve image resolution of DTS for patient positioning in IGRT.

Materials and methods: For registration purpose, both on-board IDTS (O-IDTS) and reference IDTS (R-IDTS) were required. O-IDTS was generated from cone-beam (CB) projections acquired in two narrow scan ranges separated by 90°. R-IDTS was generated from digitally reconstructed radiographs (DRR) computed from planning CT in the same two narrow scan ranges. Target offsets were determined by registration of O-IDTS and R-IDTS. The reconstruction algorithms of DRR and IDTS were implemented on general purpose graphics processing unit (GPGPU) for acceleration purpose. IDTS approach was evaluated by phantom and patient cases.

Results: Comparing with DTS, IDTS provided high-resolution images in both coronal view and sagittal views. The image resolution of IDTS in axial view was significantly improved compared to that of DTS, but still inferior compared to that of cone-beam computed tomography (CBCT). Reconstruction accuracy and registration accuracy for all cases were high which was within 1mm. Reconstruction performance of IDTS using general purpose graphics processing unit (GPGPU) can be substantially improved, thus competent for daily clinical use.

Conclusions: IDTS can provide high-resolution images in coronal and sagittal views with fewer CB projections. Image registration based on IDTS was simple and reliable compared to DTS. IDTS is potentially a useful imaging tool for fast patient positioning in IGRT.

Keywords: Cone-beam computed tomography; Digital Tomosynthesis; Digitally reconstructed radiographs; General purpose graphics processing unit; Image-guided radiotherapy.