C-arm positioning using virtual fluoroscopy for image-guided surgery

Abstract

Introduction Fluoroscopically guided procedures often involve repeated acquisitions for C-arm positioning at the cost of radiation exposure and time in the operating room. A virtual fluoroscopy system is reported with the potential of reducing dose and time spent in C-arm positioning, utilizing three key advances: robust 3D-2D registration to a preoperative CT; real-time forward projection on GPU; and a motorized mobile C-arm with encoder feedback on C-arm orientation. Method Geometric calibration of the C-arm was performed offline in two rotational directions (orbit α, orbit β). Patient registration was performed using image-based 3D-2D registration with an initially acquired radiograph of the patient. This approach for patient registration eliminated the requirement for external tracking devices inside the operating room, allowing virtual fluoroscopy using commonly available systems in fluoroscopically guided procedures within standard surgical workflow. Geometric accuracy was evaluated in terms of projection distance error (PDE) in anatomical fiducials. A pilot study was conducted to evaluate the utility of virtual fluoroscopy to aid C-arm positioning in image guided surgery, assessing potential improvements in time, dose, and agreement between the virtual and desired view. Results The overall geometric accuracy of DRRs in comparison to the actual radiographs at various C-arm positions was PDE (mean ± std) = 1.6 ± 1.1 mm. The conventional approach required on average 8.0 ± 4.5 radiographs spent “fluoro hunting” to obtain the desired view. Positioning accuracy improved from 2.6° ± 2.3° (in α) and 4.1° ± 5.1° (in β) in the conventional approach to 1.5° ± 1.3° and 1.8° ± 1.7°, respectively, with the virtual fluoroscopy approach. Conclusion Virtual fluoroscopy could improve accuracy of C-arm positioning and save time and radiation dose in the operating room. Such a system could be valuable to training of fluoroscopy technicians as well as intraoperative use in fluoroscopically guided procedures.

Development of pre-procedure virtual simulation for challenging interventional procedures: an experimental study with clinical application

“…In this study, a virtual X-ray simulation model was developed. Though there were other studies that created virtual X-rays using CT data and a movable C-arm [ 7 – 10 ], there were few simulation systems that directly access patient data and perform simulations that meet the needs of clinicians. It was essential to program the C-arm with the movement of surgical tools as in the actual operating room so that the clinician could use it directly and conveniently.…”

Intraoperative adjustment of radiographic standard projections of the spine: Interrater- and intrarater variance and consequences of ‘fluoro-hunting’ considering time and radiation exposure – A cadaveric study

“…In the aforementioned study by Da Silva et al it is stated that an average of 8.0±4.5 exposures were required before the results were accepted by the investigators [2]. In a different study performed by the same authors, an average of 6.4 radiographs was necessary to adjust the standard projections in an experimental setting.…”

“…During this process multiple radiographic images are acquired with corrections being made to patient positioning or positioning of the device in between until a correct setting is achieved. In addition to the time involved, this so-called ‘fluoro hunting’ leads to increased radiation exposure for both the patient and the staff[1, 2].…”

Technical Note: Towards Virtual Monitors for Image Guided Interventions - Real-time Streaming to Optical See-Through Head-Mounted Displays

“…Every day, countless image guided interventions are conducted by a diverse set of clinicians across many disciplines. From procedures performed by ultrasound technicians 1-3 , to orthopaedic surgeons 4,5 , to interventional radiologists 6,7 , one aspect unites them all: the viewing of medical images on conventional monitors [8][9][10] . In many of the aforementioned interventional scenarios, real time images are acquired to guide the procedure.…”