Real‐time 3D‐surface‐guided head refixation useful for fractionated stereotactic radiotherapy

Abstract

Accurate and precise head refixation in fractionated stereotactic radiotherapy has been achieved through alignment of real-time 3D-surface images with a reference surface image. The reference surface image is either a 3D optical surface image taken at simulation with the desired treatment position, or a CT/MRI-surface rendering in the treatment plan with corrections for patient motion during CT/MRI scans and partial volume effects. The real-time 3D surface images are rapidly captured by using a 3D video camera mounted on the ceiling of the treatment vault. Any facial expression such as mouth opening that affects surface shape and location can be avoided using a new facial monitoring technique. The image artifacts on the real-time surface can generally be removed by setting a threshold of jumps at the neighboring points while preserving detailed features of the surface of interest. Such a real-time surface image, registered in the treatment machine coordinate system, provides a reliable representation of the patient head position during the treatment. A fast automatic alignment between the real-time surface and the reference surface using a modified iterative-closest-point method leads to an efficient and robust surface-guided target refixation. Experimental and clinical results demonstrate the excellent efficacy of <2 min set-up time, the desired accuracy and precision of <1 mm in isocenter shifts, and <1 degree in rotation.

Initial Validation and Clinical Experience with 3D Optical-Surface-Guided Whole Breast Irradiation of Breast Cancer

“…We are reporting the remaining 6 patients with BC for feasibility evaluation of SGRT. The second trial accrued 23 BC patients, one with synchronous bilateral disease, at the Henry Ford Health System (HFHS) from 2005 to 2007 for clinical validation of accuracy, precision, and efficiency of the SGRT of WBI (24, 25). All patients signed the consents for participation of the studies.…”

“…The reference surface was constructed based on the skin contours in treatment plan. The surface matching was archived by a modified iterative closest point method (24). All surface images were automatically saved in a patient-specific folder and those online corrections results were appended to a patient file to be used for this clinical validation that included following procedures and measurements.…”

Clinical Results of a Pilot Study on Stereovision-Guided Stereotactic Radiotherapy and Intensity Modulated Radiotherapy

“…The two cameras are separated by 65 cm to view the patient’s head from different angles. All 3D surface points in the view of a CCD camera (image matrix of 480 × 640) are determined by an analytical solution based on the modified triangular principle (34, 35). Therefore, a full frame of 3D surfaces can be captured in one snapshot.…”

Non-invasive tumor localization by 3D registration of range sensor and computer tomography images.

“…Recently, an interesting head positioning method has been proposed, their method uses two 3D sensor, one of them is fixed in the CT-room and the other is fixed at treatment room [8]. The algorithm principle can be divided in three parts consisting of a reference surface generation during CT-simulation, "controlled" patient face acquisitions in the therapy room and data alignments providing the patient positioning parameters.…”