Evaluation of the setup discrepancy between 6D ExacTrac and cone beam computed tomography in spine stereotactic body radiation therapy

Abstract

The objective of this study was to analyze the difference in residual setup errors between 6D ExacTrac and 3D cone-beam computed tomography (CBCT) image-guided systems in spinal stereotactic body radiation therapy (SBRT). We investigated 76 patients with spinal tumors who received SBRT using Novalis Tx at our institution between January 2013 and September 2020. A Vac-lok (EZ-FIX®, Arlico Medical Company, South Korea) fixture and an assistive device, based on the region involved, were used to immobilize patients and to increase the inter-fractional setup reproducibility. The difference in the root mean square (RMS) between the 6D ExacTrac and 3D CBCT was -0.75 mm, 0.45 mm, 0.16 mm, and -0.03°; the RMS value was 1.31 mm, 1.06 mm, 0.87 mm, and 0.64°; and the standard deviation was 0.80 mm, 0.72 mm, 0.62 mm, and 0.44° for lateral, longitudinal, vertical, and yaw directions, respectively. The difference in the average RMS between ExacTrac and CBCT was <1.03 mm in the translation direction and <0.47° in the rotational direction; the results were statistically significant in the lateral, longitudinal, and vertical directions, but not in the yaw direction. Thus, it is necessary to verify the ExacTrac image according to the CBCT image.

Shift detection discrepancy between ExacTrac Dynamic system and cone‐beam computed tomography

“…These results were comparable with the previous study on the setup discrepancies measured with the ExacTrac X‐ray 6D (previous version of EXTD) and CBCT on an anthropomorphic phantom containing spine structure by Chang et al. (<1.0 mm and <1.0 degree) 12,29 . Also, Ma et al.…”

Optimized workflow to minimise intra-fractional motion during stereotactic body radiotherapy of spinal metastases

“…Some studies have questioned whether ExacTrac imaging can provide the same degree of precision as CBCT [3] , [5] . The low percentage of ExacTrac verification images within tolerance (1 mm/1°) in the ExacTrac pre- RT Arc 1 ( Fig.…”

“…Stereotactic body radiotherapy (SBRT) also referred to as Stereotactic body radiosurgery (SBRS) is a non-invasive radiotherapy technique used to deliver high doses of radiation to a tumour in a single or limited number of fractions [1] , [2] , [3] , [4] . SBRT for spinal metastases is established as an effective treatment modality with proven clinical efficacy [1] , [3] , [4] , [5] . A high degree of spatial accuracy is achieved by using image-guided radiotherapy (IGRT) to accurately irradiate the target, whilst minimizing the dose delivered to the healthy neighbouring tissues, thus avoiding potential toxicities, particularly to the spinal cord [2] , [6] , [13] .…”

“…For high precision treatments techniques such as spinal SBRT, it is crucial to minimize positional errors in order to ensure a high dose gradient at the spinal cord and tumour interface [1] , [2] , [3] , [4] , [13] . Patient positioning in six degrees of freedom (6 DoF) with stereoscopic kilovoltage imaging (ExacTrac, BrainLab, Germany) and 3D kV- cone beam computerized tomography (CBCT) image guidance systems can be used in combination, to achieve the required high precision and is highly beneficial for spinal SBRT [5] , [3] .…”

Single-pulse X-ray Acoustic Computed Tomography Image Guided Precision Radiation Therapy

“…CBCT is performed prior to treatment delivery to confirm target position with respect to the isocenter 9 ; whereas robotic couch uses a 6D frameless system that permits translational and rotational robotic couch corrections 10 . These two technologies have been widely combined 11 , nonetheless, these target localization methods involve an additional imaging dose to the patient.…”