Navigating the fluoroscope's C-arm back into position: an accurate and practicable solution to cut radiation and optimize intraoperative workflow

Radiation Exposure in XLIF Surgery Utilizing Ultra-Low Radiation Imaging with Image Enhancement Software: A Randomized Controlled Trial

BACKGROUND CONTEXT

Minimally invasive spine surgery has grown significantly over the last decade. Lateral approaches for interbody fusion, such as XLIF/LLIF result in higher radiation exposure for the operating room (OR) staff and the patient compared to posterior techniques. New technologies such as ultra-low radiation imaging (ULRI) combined with image enhancement (IE) software may help reduce this exposure while maintaining procedural efficacy.

PURPOSE

To evaluate whether using ULRI with IE software (mFluoro) reduces radiation exposure for OR staff and patients during lateral interbody fusion via the XLIF approach without increasing procedure time.

STUDY DESIGN

Prospective, randomized controlled trial.

PATIENT SAMPLE

The sample consists of 60 patients.

OUTCOME MEASURES

Primary outcome: Radiation exposure of the OR staff, measured in microsieverts (μSv), documented by personal dosimetry centrally in front of the sternum above the lead apron.

SECONDARY OUTCOMES

Radiation exposure of the patient, measured in cGy*cm2, documented by the fluoroscopy unit's dose report; Procedure time, measured in minutes.

METHODS

This single-center prospective randomized controlled single-blind study included 60 patients who all underwent single-level lateral interbody fusion via XLIF approach between 03/2023 and 12/2024. Patients were randomized into two groups: intervention group (mFluoro) or control group (cFluoro). Radiation exposure of the OR staff was measured using dosimeters, and imaging parameters were extracted from the fluoroscopy unit's dose report.

RESULTS

No significant difference was found between the two groups regarding age, gender, BMI, implant type, and diagnosis (all p>0.05). The mFluoro group showed a significant reduction in radiation exposure for the OR staff: 72.1% for the surgeon (p<0.001), 76.1% for the assistant (p<0.001), and 67.5% for the scrub nurse (p<0.001). Patient radiation exposure was also significantly reduced in the intervention group, with dose area product (DAP) values lowered by 66.1% (p<0.001). Fewer images were acquired in the mFluoro group (31.3% reduction, p<0.001), and procedure time was reduced by 17.7% (71.3 ± 21.3 min vs. 86.6 ± 31.5 min; p=0.034).

CONCLUSION

Using ULRI with IE software significantly reduces radiation exposure for the OR staff in single-level lateral interbody fusion via the XLIF approach. Furthermore, the radiation exposure for the patient was also significantly reduced.

[Mobile C-arm-Radiation exposure and workflow killer? : Potential of an innovative assistance system for intraoperative positioning]

Despite its versatile applicability the intraoperative use of a mobile C‑arm is often problematic and potentially associated with increased radiation exposure for both the patient and the personnel. In particular, the correct positioning for adequate imaging can become a problem as the nonsterile circulating nurse has to coordinate the various maneuvers together with the surgeon without having a good view of the surgical field. The sluggishness of the equipment and the intraoperative setting (sterile borders, additional hardware, etc.) pose further challenges. A light detection and ranging (LIDAR)-based assistance system shows promise to provide accurate and intuitive repositioning support as part of an initial series of experimental trials. For this purpose, the sensors are attached to the C‑arm base unit and enable navigation of the device in the operating room to a stored target position using a simultaneous localization and mapping (SLAM) algorithm. An improvement of the workflow as well as a reduction of radiation exposure represent the possible potential of this system. The advantages over other experimental approaches are the lack of external hardware and the ease of use without isolating the operator from the rest of the operating room environment; however, the suitability for daily use in the presence of additional interfering factors should be verified in further studies.

RAY-POS: a LIDAR-based assistance system for intraoperative repositioning of mobile C-arms without external aids

PURPOSE

In current clinical practice, intraoperative repositioning of mobile C-arms is challenging due to a lack of visual cues and efficient guiding tools. This can be detrimental to the surgical workflow and lead to additional radiation burdens for both patient and personnel. To overcome this problem, we present our novel approach Lidar-based X-ray Positioning for Mobile C-arms (RAY-POS) for assisting circulating nurses during intraoperative C-arm repositioning without requiring external aids.

METHODS

RAY-POS consists of a localization module and a graphical user interface for guiding the user back to a previously recorded C-Arm position. We conducted a systematic comparison of simultaneous localization and mapping (SLAM) algorithms using different attachment positions of light detection and ranging (LIDAR) sensors to benchmark localization performance within the operating room (OR). For two promising combinations, we conducted further end-to-end repositioning tests within a realistic OR setup.

RESULTS

SLAM algorithm gmapping with a LIDAR sensor mounted 40 cm above the C-arm's horizontal unit performed best regarding localization accuracy and long-term stability. The distribution of the repositioning error yielded an effective standard deviation of 7.61 mm.

CONCLUSION

We conclude that a proof-of-concept for LIDAR-based C-arm repositioning without external aids has been achieved. In future work, we mainly aim at extending the capabilities of our system and evaluating the usability together with clinicians.

The effect of artificial X-rays on C-arm positioning performance in a simulated orthopaedic surgical setting

PURPOSE

We designed an Artificial X-ray Imaging System (AXIS) that generates simulated fluoroscopic X-ray images on the fly and assessed its utility in improving C-arm positioning performance by C-arm users with little or no C-arm experience.

METHODS

The AXIS system was comprised of an optical tracking system to monitor C-arm movement, a manikin, a reference CT volume registered to the manikin, and a Digitally Reconstructed Radiograph algorithm to generate live simulated fluoroscopic images. A user study was conducted with 30 participants who had little or no C-arm experience. Each participant carried out four tasks using a real C-arm: an introduction session, an AXIS-guided set of pelvic imaging tasks, a non-AXIS guided set of pelvic imaging tasks, and a questionnaire. For each imaging task, the participant replicated a set of three target X-ray images by taking real radiographs of a manikin with a C-arm. The number of X-rays required, task time, and C-arm positioning accuracy were recorded.

RESULTS

We found a significant 53% decrease in the number of X-rays used and a moderate 10-26% improvement in lateral C-arm axis positioning accuracy without requiring more time to complete the tasks when the participants were guided by artificial X-rays. The questionnaires showed that the participants felt significantly more confident in their C-arm positioning ability when they were guided by AXIS. They rated the usefulness of AXIS as very good to excellent, and the realism and accuracy of AXIS as good to very good.

CONCLUSION

Novice users working with a C-arm machine supplemented with the ability to generate simulated X-ray images could successfully accomplish positioning tasks in a simulated surgical setting using markedly fewer X-ray images than when unassisted. In future work, we plan to determine whether such a system can produce similar results in the live operating room without lengthening surgical procedures.

A visual odometry base-tracking system for intraoperative C-arm guidance

PURPOSE

C-arms are portable X-ray devices used to generate radiographic images in orthopedic surgical procedures. Evidence suggests that scouting images, which are used to aid in C-arm positioning, result in increased operation time and excess radiation exposure. C-arms are also primarily used qualitatively to view images, with limited quantitative functionality. Various techniques have been proposed to improve positioning, reduce radiation exposure, and provide quantitative measuring tools, all of which require accurate C-arm position tracking. While external stereo camera systems can be used for this purpose, they are typically considered too obtrusive. This paper therefore presents the development and verification of a low-profile, real-time C-arm base-tracking system using computer vision techniques.

METHODS

The proposed tracking system, called OPTIX (On-board Position Tracking for Intraoperative X-rays), uses a single downward-facing camera mounted to the base of a C-arm. Relative motion tracking and absolute position recovery algorithms were implemented to track motion using the visual texture in operating room floors. The accuracy of the system was evaluated in a simulated operating room mounted on a real C-arm.

RESULTS

The relative tracking algorithm measured relative translation position changes with errors of less than 0.75% of the total distance travelled, and orientation with errors below 5% of the cumulative rotation. With an error-correction step incorporated, OPTIX achieved C-arm repositioning with translation errors of less than [Formula: see text]  mm and rotation errors of less than [Formula: see text]. A display based on the OPTIX measurements enabled consistent C-arm repositioning within 5 mm of a previously stored reference position.

CONCLUSION

The system achieved clinically relevant accuracies and could result in a reduced need for scout images when re-acquiring a previous position. We believe that, if implemented in an operating room, OPTIX has the potential to reduce both operating time and harmful radiation exposure to patients and surgical staff.

Co-localized augmented human and X-ray observers in collaborative surgical ecosystem

PURPOSE

Image-guided percutaneous interventions are safer alternatives to conventional orthopedic and trauma surgeries. To advance surgical tools in complex bony structures during these procedures with confidence, a large number of images is acquired. While image-guidance is the de facto standard to guarantee acceptable outcome, when these images are presented on monitors far from the surgical site the information content cannot be associated easily with the 3D patient anatomy.

METHODS

In this article, we propose a collaborative augmented reality (AR) surgical ecosystem to jointly co-localize the C-arm X-ray and surgeon viewer. The technical contributions of this work include (1) joint calibration of a visual tracker on a C-arm scanner and its X-ray source via a hand-eye calibration strategy, and (2) inside-out co-localization of human and X-ray observers in shared tracking and augmentation environments using vision-based simultaneous localization and mapping.

RESULTS

We present a thorough evaluation of the hand-eye calibration procedure. Results suggest convergence when using 50 pose pairs or more. The mean translation and rotation errors at convergence are 5.7 mm and [Formula: see text], respectively. Further, user-in-the-loop studies were conducted to estimate the end-to-end target augmentation error. The mean distance between landmarks in real and virtual environment was 10.8 mm.

CONCLUSIONS

The proposed AR solution provides a shared augmented experience between the human and X-ray viewer. The collaborative surgical AR system has the potential to simplify hand-eye coordination for surgeons or intuitively inform C-arm technologists for prospective X-ray view-point planning.

[3D augmented reality visualization for navigated osteosynthesis of pelvic fractures]

BACKGROUND

Despite great advances in the development of hardware and software components, surgical navigation systems have only seen limited use in current clinical settings due to their reported complexity, difficulty of integration into clinical workflows and questionable advantages over traditional imaging modalities.

OBJECTIVES

Development of augmented reality (AR) visualization for surgical navigation without the need for infrared (IR) tracking markers and comparison of the navigation system to conventional imaging.

MATERIAL AND METHODS

Novel navigation system combining a cone beam computed tomography (CBCT) capable C‑arm with a red-green-blue depth (RGBD) camera. Testing of the device by Kirschner wire (K-wire) placement in phantoms and evaluation of the necessary operating time, number of fluoroscopic images and overall radiation dose were compared to conventional x‑ray imaging.

RESULTS

We found a significant reduction of the required time, number of fluoroscopic images and overall radiation dose in 3D AR navigation in comparison to x‑ray imaging.

CONCLUSION

Our AR navigation using RGBD cameras offers a flexible and intuitive visualization of the operating field for the navigated osteosynthesis without IR tracking markers, enabling surgeons to complete operations quicker and with a lower radiation exposure to the patient and surgical staff.

New Calibrator with Points Distributed Conical Helically for Online Calibration of C-Arm

To improve the accuracy of calibration of C-arm, and overcome the space limitation in surgery, we proposed a new calibrator for online calibration of C-arm. After the image rectification by a polynomial fitting-based global correction method, the C-arm was assumed as an ideal pinhole model. The relationships between two kinds of spatial calibration errors and the distribution of fiducial points were studied: the performance of FRE (Fiducial Registration Error) and TRE (Target Registration Error) were not consistent, but both were best at the 12 marked points; the TRE decreased with the increase of the uniformity of calibration points distribution, and with the decrease of the distance between the target point and the center of calibration points. A calibrator with 12 fiducial points conical helically distributed, which could be placed on the knee, was an attractive option. A total of 10 experiments on C-arm calibration accuracy were conducted and the mean value of mapping error was 0.41 mm. We designed an ACL reconstruction navigation system and carried out specimen experiments on 4 pairs of dry femur and tibia. The mean accuracy of navigation system was 0.85 mm, which is important to the tunnel positioning for ACL reconstruction.

Augmented reality-based feedback for technician-in-the-loop C-arm repositioning

Interventional C-arm imaging is crucial to percutaneous orthopedic procedures as it enables the surgeon to monitor the progress of surgery on the anatomy level. Minimally invasive interventions require repeated acquisition of X-ray images from different anatomical views to verify tool placement. Achieving and reproducing these views often comes at the cost of increased surgical time and radiation. We propose a marker-free ‘technician-in-the-loop’ Augmented Reality (AR) solution for C-arm repositioning. The X-ray technician operating the C-arm interventionally is equipped with a head-mounted display system capable of recording desired C-arm poses in 3D via an integrated infrared sensor. For C-arm repositioning to a target view, the recorded pose is restored as a virtual object and visualized in an AR environment, serving as a perceptual reference for the technician. Our proof-of-principle findings from a simulated trauma surgery indicate that the proposed system can decrease the 2.76 X-ray images required for re-aligning the scanner with an intra-operatively recorded C-arm view down to zero, suggesting substantial reductions of radiation dose. The proposed AR solution is a first step towards facilitating communication between the surgeon and the surgical staff, improving the quality of surgical image acquisition, and enabling context-aware guidance for surgery rooms of the future.

The Effect of C-Arm Mobility and Field of Vision on Radiation Exposure in the Treatment of Proximal Femoral Fractures: A Randomized Clinical Trial

Objectives

To examine the effect of fluoroscopy devices with different sizes of image intensifier and C-arm maneuverability on operating time, fluoroscopy time, radiation dose and reduction, and fixation quality at intertrochanteric femoral fractures.

Design

Single-center, randomized, prospective study.

Setting

Academic Level I trauma hospital.

Patients and Intervention

34 patients treated with cephalomedullary nailing for a stable, intertrochanteric proximal femur fracture (OTA A1).

Main Outcome Measurement

The total working time of the fluoroscopy device, the dose-area product (DAP), operating time, reduction quality (cortical continuity, symmetrical collodiaphyseal angle, and shortness), and fixation quality (Bosworth quadrants, the tip-apex distance, TAD).

Results

There were no cases of poor reduction; also the placement of the blade was optimal for 14 patients and suboptimal in 3 patients in each group. Superior-posterior placement of the blade or TAD > 25 mm was not seen in any patient. Total operating time was significantly shorter when using device A compared to the use of device B (20.1 ± 3.4 mins versus 25.3 ± 5.4 mins, p < 0.001). Total radiation time was significantly shorter with device A compared to the use of device B (58.1 ± 19.4 secs versus 98.9  ±  55.4 secs, p = 0.008). The measured radiation dose was lower with the use of device A compared to device B (3.5  ±  1.2 Gy·cm² versus 7.3  ±  4.5 Gy·cm², p = 0.002).

Conclusion

Physical properties of fluoroscopy devices used during the fixation of intertrochanteric fractures could yield significant differences in operating times and the radiation dose while having comparable clinical results.

Multi-modal imaging, model-based tracking, and mixed reality visualisation for orthopaedic surgery

Orthopaedic surgeons are still following the decades old workflow of using dozens of two-dimensional fluoroscopic images to drill through complex 3D structures, e.g. pelvis. This Letter presents a mixed reality support system, which incorporates multi-modal data fusion and model-based surgical tool tracking for creating a mixed reality environment supporting screw placement in orthopaedic surgery. A red–green–blue–depth camera is rigidly attached to a mobile C-arm and is calibrated to the cone-beam computed tomography (CBCT) imaging space via iterative closest point algorithm. This allows real-time automatic fusion of reconstructed surface and/or 3D point clouds and synthetic fluoroscopic images obtained through CBCT imaging. An adapted 3D model-based tracking algorithm with automatic tool segmentation allows for tracking of the surgical tools occluded by hand. This proposed interactive 3D mixed reality environment provides an intuitive understanding of the surgical site and supports surgeons in quickly localising the entry point and orienting the surgical tool during screw placement. The authors validate the augmentation by measuring target registration error and also evaluate the tracking accuracy in the presence of partial occlusion.

Ionizing Radiation Doses Detected at the Eye Level of the Primary Surgeon During Orthopaedic Procedures

OBJECTIVES

To evaluate the ionizing radiation dose received by the eyes of orthopaedic surgeons during various orthopaedic procedures. Secondary objective was to compare the ionizing radiation dose received between differing experience level.

DESIGN

Prospective comparative study between January 2013 and May 2014.

SETTING

Westmead Hospital, a Level 1 Trauma Centre for Greater Western Sydney.

PARTICIPANTS

A total of 26 surgeons volunteered to participate within the study.

INTERVENTION

Experience level, procedure performed, fluoroscopy time, dose area product, total air kerma, and eye dose received was recorded. Participants were evaluated on procedure and experience level.

MAIN OUTCOME MEASUREMENTS

Radiation dose received at eye level by the primary surgeon during an orthopaedic procedure.

RESULTS

Data from a total of 131 cases was recorded and included for analysis. The mean radiation dose detected at the eye level of the primary surgeon was 0.02 mSv (SD = 0.05 mSv) per procedure. Radiation at eye level was only detected in 31 of the 131 cases. The highest registered dose for a single procedure was 0.31 mSv. Femoral nails and pelvic fixation procedures had a significantly higher mean dose received than other procedure groups (0.04 mSv (SD = 0.07 mSv) and 0.04 mSv (SD = 0.06 mSv), respectively). Comparing the eye doses received by orthopaedic consultants and trainees, there was no significant difference between the 2 groups.

CONCLUSIONS

The risk of harmful levels of radiation exposure at eye level to orthopaedic surgeons is low. This risk is greatest during insertion of femoral intramedullary nails and pelvic fixation, and it is recommended that in these situations, surgeons take all reasonable precautions to minimize radiation dose. The orthopaedic trainees in this study were not subjected to higher doses of radiation than their consultant trainers. On the basis of these results, most of the orthopaedic surgeons remain well below the yearly radiation dose of 20 mSv as recommended by the International Commission on Radiological Protection.

Desired-View--controlled positioning of angiographic C-arms

We present the idea of a user interface concept, which resolves the challenges involved in the control of angiographic C-arms for their constant repositioning during interventions by either the surgeons or the surgical staff. Our aim is to shift the paradigm of interventional image acquisition workflow from the traditional control device interfaces to 'desired-view' control. This allows the physicians to only communicate the desired outcome of imaging, based on simulated X-rays from pre-operative CT or CTA data, while the system takes care of computing the positioning of the imaging device relative to the patient's anatomy through inverse kinematics and CT to patient registration. Together with our clinical partners, we evaluate the new technique using 5 patient CTA and their corresponding intraoperative X-ray angiography datasets.

3D atlas-based registration can calculate malalignment of femoral shaft fractures in six degrees of freedom

Objective

This study presents and evaluates a semi-automated algorithm for quantifying malalignment in complex femoral shaft fractures from a single intraoperative cone-beam CT (CBCT) image of the fractured limb.

Methods

CBCT images were acquired of complex comminuted diaphyseal fractures created in 9 cadaveric femora (27 cases). Scans were segmented using intensity-based thresholding, yielding image stacks of the proximal, distal and comminuted bone. Semi-deformable and rigid affine registrations to an intact femur atlas (synthetic or cadaveric-based) were performed to transform the distal fragment to its neutral alignment. Leg length was calculated from the volume of bone within the comminution fragment. The transformations were compared to the physical input malalignments.

Results

Using the synthetic atlas, translations were within 1.71 ± 1.08 mm (medial/lateral) and 2.24 ± 2.11 mm (anterior/posterior). The varus/valgus, flexion/extension and periaxial rotation errors were 3.45 ± 2.6°, 1.86 ± 1.5° and 3.4 ± 2.0°, respectively. The cadaveric-based atlas yielded similar results in medial/lateral and anterior/posterior translation (1.73 ± 1.28 mm and 2.15 ± 2.13 mm, respectively). Varus/valgus, flexion/extension and periaxial rotation errors were 2.3 ± 1.3°, 2.0 ± 1.6° and 3.4 ± 2.0°, respectively. Leg length errors were 1.41 ± 1.01 mm (synthetic) and 1.26 ± 0.94 mm (cadaveric). The cadaveric model demonstrated a small improvement in flexion/extension and the synthetic atlas performed slightly faster (6 min 24 s ± 50 s versus 8 min 42 s ± 2 min 25 s).

Conclusions

This atlas-based algorithm quantified malalignment in complex femoral shaft fractures within clinical tolerances from a single CBCT image of the fractured limb.

Can a semi-automated surface matching and principal axis-based algorithm accurately quantify femoral shaft fracture alignment in six degrees of freedom?

Accurate alignment of femoral shaft fractures treated with intramedullary nailing remains a challenge for orthopaedic surgeons. The aim of this study is to develop and validate a cone-beam CT-based, semi-automated algorithm to quantify the malalignment in six degrees of freedom (6DOF) using a surface matching and principal axes-based approach. Complex comminuted diaphyseal fractures were created in nine cadaveric femora and cone-beam CT images were acquired (27 cases total). Scans were cropped and segmented using intensity-based thresholding, producing superior, inferior and comminution volumes. Cylinders were fit to estimate the long axes of the superior and inferior fragments. The angle and distance between the two cylindrical axes were calculated to determine flexion/extension and varus/valgus angulation and medial/lateral and anterior/posterior translations, respectively. Both surfaces were unwrapped about the cylindrical axes. Three methods of matching the unwrapped surface for determination of periaxial rotation were compared based on minimizing the distance between features. The calculated corrections were compared to the input malalignment conditions. All 6DOF were calculated to within current clinical tolerances for all but two cases. This algorithm yielded accurate quantification of malalignment of femoral shaft fractures for fracture gaps up to 60 mm, based on a single CBCT image of the fractured limb.

Closed-form inverse kinematics for interventional C-arm X-ray imaging with six degrees of freedom: modeling and application

For trauma and orthopedic surgery, maneuvering a mobile C-arm fluoroscope into a desired position to acquire an X-ray is a routine surgical task. The precision and ease of use of the C-arm becomes even more important for advanced interventional imaging techniques such as parallax-free X-ray image stitching. Today's standard mobile C-arms have been modeled with only five degrees of freedom (DOF), which definitely restricts their motions in 3-D Cartesian space. In this paper, we present a method to model both the mobile C-arm and patient's table as an integrated kinematic chain having six DOF without constraining table position. The closed-form solutions for the inverse kinematics problem are derived in order to obtain the required values for all C-arm joint and table movements to position the fluoroscope at a desired pose. The modeling method and the closed-form solutions can be applied to general isocentric or nonisocentric mobile C-arms. By achieving this we develop an efficient and intuitive inverse kinematics-based method for parallax-free panoramic X-ray imaging. In addition, we implement a 6-DOF C-arm system from a low-cost mobile fluoroscope to optimally acquire X-ray images based solely on the computation of the required movement for each joint by solving the inverse kinematics on a continuous basis. Through simulation experimentation, we demonstrate that the 6-DOF C-arm model has a larger working space than the 5-DOF model. C-arm repositioning experiments show the practicality and accuracy of our 6-DOF C-arm system. We also evaluate the novel parallax-free X-ray stitching method on phantom and dry bones. Using five trials, results show that parallax-free panoramas generated by our method are of high visual quality and within clinical tolerances for accurate evaluation of long bone geometry (i.e., image and metric measurement errors are less than 1% compared to ground-truth).