Clinical experience with two frameless stereotactic radiosurgery (fSRS) systems using optical surface imaging for motion monitoring

Abstract

The purpose of this study was to compare two clinical immobilization systems for intracranial frameless stereotactic radiosurgery (fSRS) under the same clinical procedure using cone-beam computed tomography (CBCT) for setup and videobased optical surface imaging (OSI) for initial head alignment and intrafractional motion monitoring. A previously established fSRS procedure was applied using two intracranial immobilization systems: PinPoint system (head mold and mouthpiece) and Freedom system (head mold and open face mask). The CBCT was used for patient setup with four degrees of freedom (4DOF), while OSI was used for 6DOF alignment prior to CBCT, post-CBCT setup verification at all treatment couch angles (zero and nonzero), and intrafractional motion monitoring. Quantitative comparison of the two systems includes residual head rotation, head restriction capacity, and patient setup time in 25 patients (29 lesions) using PinPoint and 8 patients (29 fractions) using Freedom. The maximum possible motion was assessed in nine volunteers with deliberate, forced movement in Freedom system. A consensus-based comparison of patient comfort level and clinical ease of use is reported. Using OSIguided corrections, the maximum residual rotations in all directions were 1.1° ± 0.5° for PinPoint and 0.6° ± 0.3° for Freedom. The time spent performing rotation corrections was 5.0 ± 4.1 min by moving the patient with PinPoint and 2.7 ± 1.0 min by adjusting Freedom couch extension. After CBCT, the OSI-CBCT discrepancy due to different anatomic landmarks for alignment was 2.4 ± 1.3 mm using PinPoint and 1.5 ± 0.7 mm using Freedom. Similar results were obtained for setup verification at couch angles (< 1.5 mm) and for motion restriction: 0.4 ± 0.3 mm/0.2° ± 0.2° in PinPoint and 0.6 ± 0.3 mm/0.3° ± 0.1° in Freedom. The maximum range of forced head motion was 2.2 ± 1.0 mm using Freedom. Both intracranial fSRS immobilization systems can restrict head motion within 1.5 mm during treatment as monitored by OSI. Setting a motion threshold for beam-hold ensures that head motion is constrained within the treatment margin during beam-on periods. The capability of 6D setup is useful to improve treatment accuracy. Patient comfort and clinical workflow should play a substantial role in system selection, and Freedom system outperforms PinPoint system in these two aspects.

Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy

“…[1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases. [1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases.…”

“…[1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for intrafraction motion. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for intrafraction motion.…”

“…Frameless radiosurgery has been used to improve patient comfort during treatment and has been shown to have the same level of positional accuracy as framed treatments. [1][2][3][4] Our institution has previously published on the use of FFF-VMAT stereotactic radiotherapy (SRT) to significantly reduce treatment time 5 as well as utilizing a single isocenter for the treatment of multiple brain metastases. 6 Due to the use of a headrest and mask in place of an invasive headframe, imaging during treatment via x-ray or optical guidance has been used to monitor intrafraction motion.…”

“…6 Due to the use of a headrest and mask in place of an invasive headframe, imaging during treatment via x-ray or optical guidance has been used to monitor intrafraction motion. 4,7,8 We recently commissioned an Edge (Varian Medical Systems, Palo Alto, CA) linear accelerator with an optical surface monitoring system (OSMS), a camera based system for surface guided radiation therapy (SGRT), to monitor all SRT patients for intrafraction motion.…”

Feasibility of differential geometry-based features in detection of anatomical feature points on patient surfaces in range image-guided radiation therapy

“…Recently, marker-less range (distance) imaging systems, such as stereovision systems [e.g., AlignRT system (VisionRT, Ltd., London, UK)] [9][10][11] and laser range scanners [e.g., Galaxy system (LAP Laser, Lünberg, Germany)] [12], have been introduced for monitoring intra-fractional patient motion. Range images can be defined as three-dimensional (3D) images, i.e., point distribution representation of the patient surface with 3D coordinates in the Cartesian coordinate system.…”