Mobile C-arm Research Articles

Toward automatic C-arm positioning for standard projections in orthopedic surgery

PurposeGuidance and quality control in orthopedic surgery increasingly rely on intra-operative fluoroscopy using a mobile C-arm. The accurate acquisition of standardized and anatomy-specific projections is essential in this process. The corresponding iterative positioning of the C-arm is error prone and involves repeated manual acquisitions or even continuous fluoroscopy. To reduce time and radiation exposure for patients and clinical staff and to avoid errors in fracture reduction or implant placement, we aim at guiding—and in the long-run automating—this procedure.MethodsIn contrast to the state of the art, we tackle this inherently ill-posed problem without requiring patient-individual prior information like preoperative computed tomography (CT) scans, without the need of registration and without requiring additional technical equipment besides the projection images themselves. We propose learning the necessary anatomical hints for efficient C-arm positioning from in silico simulations, leveraging masses of 3D CTs. Specifically, we propose a convolutional neural network regression model that predicts 5 degrees of freedom pose updates directly from a first X-ray image. The method is generalizable to different anatomical regions and standard projections.ResultsQuantitative and qualitative validation was performed for two clinical applications involving two highly dissimilar anatomies, namely the lumbar spine and the proximal femur. Starting from one initial projection, the mean absolute pose error to the desired standard pose is iteratively reduced across different anatomy-specific standard projections. Acquisitions of both hip joints on 4 cadavers allowed for an evaluation on clinical data, demonstrating that the approach generalizes without retraining.ConclusionOverall, the results suggest the feasibility of an efficient deep learning-based automated positioning procedure, which is trained on simulations. Our proposed 2-stage approach for C-arm positioning significantly improves accuracy on synthetic images. In addition, we demonstrated that learning based on simulations translates to acceptable performance on real X-rays.

Endovascular Infrarenal Aortic Aneurysm Repair Performed in a Hybrid Operating Room Versus Conventional Operating Room Using a C-Arm

To compare contrast usage and radiation exposure during endovascular aneurysm repair (EVAR) using mobile C-arm imaging in a conventional operating room (OR) or fixed angiographic equipment in a hybrid OR (HR). A retrospective unicenter study from May 2016 to August 2019. All consecutive patients undergoing standard EVAR were included. Patients were divided into 2 groups. Group OR included EVARs performed in a conventional OR with a mobile C-arm (May 2016 to April 2018) and group HR included EVARs performed with a fixed angiographic equipment in an HR (May 2018 to August 2019). Data collected included patient demographics, aneurysm diameter, neck length, radiation dose: median dose-area product (DAP), fluoroscopy time, total operative time, contrast use, and 30-day clinical outcomes. A total of 77 patients were included in the study (42 patients in group OR and 35 patients in group HR). There was no difference in age, body mass index (BMI), mean aneurysm, and neck length between groups. Patients in the group HR received less contrast volume (108.6mL [±41.5] vs. 162.5mL [±52.6]; P<0.001), but higher radiation dose (154Gycm2 [±102.9] vs. 61.5Gy cm2 [±42.4]; P<0.001). There were no differences in fluoroscopy time (20.4min [±8.5] vs. 23.2min [±12.4]; P=0.274) and total operative time (106.4 [±22.3] vs. 109.4 [±25.8]; P=0.798). No difference was found in terms of 30-day complication rates or operative mortality between groups. DAP was positively correlated with BMI in the group OR (Spearman's rank correlation coefficient rs, 0.580; P<0.001), but no correlation could be seen in the group HR (rs, 0.408; P=0.028). Routine EVAR performed in a hybrid fixed-imaging suite may be associated with less contrast usage, but higher radiation exposure in our center. The significantly higherradiation exposure when the mobile C-arm is replaced by an HR should not be underestimated.

A Simulation Study With Electronic Dosimeter to Estimate Patient and Personnel Dose in Orthopedic Surgery

Background: The use of mini C-arm is required in many orthopedic surgeries as an image-guided tool. Studies have shown an unnecessarily high dose to patients if exposures are not properly optimized. Also, scatter radiation to personnel may increase the risk of cancer if an appropriate protective device is not used. Objectives: This study aims to determine the patient’s dose and scatter radiation to the surgeon, anesthetist, and scrub nurse. Also, a comparison will be made with other studies on this topic. Methods: A phantom was designed to simulate a patient on the operating table to produce scatter radiation. In the same vein, a mobile mini C-arm unit was positioned with the x-ray tube beneath the head and the image receptor above the operating table. Measurements were made with a measuring tape from the central axis to the position of the surgeon, anesthetist, and scrub nurse. The Entrance Surface Dose (ESD) was determined by placing the electronic dosimeter at the surface of the phantom to estimate the patient dose. Similarly, each personnel dose/dose rate from the central axis was determined using a similar detector. Results: The total average time for most orthopedic surgeries in the studied facility was 3.3 minutes. The estimated ESD to the patient was 25.03 µSv and the scatter radiation per patient reaching the simulated anesthetist, scrub nurse, and surgeon was, 3.75, 3.59, and 7.72 µSv, respectively. The estimated dose values per year to anesthetist, scrub nurse, and surgeon were 390, 373.36, and 802 µSv, respectively. Conclusion: The personnel recommended limit dose rate was &lt;20000 µSv/y. The technical factor used and total exposure time from this study could have affected the radiation dose. This study showed that personnel was safe even without the use of lead apron. Nevertheless, the use of an appropriate protective device should be encouraged to ensure safety.

Automatic and Accurate Repositioning of C-Arm Prototype Using Motion Capture Systems and Deep Learning

The C-Arm x-ray system (C-Arm) is a useful medical device commonly used in surgeries that require the use of x-ray images during operations. In some operations, surgeons rely heavily on the mobile C-Arm to effectively execute the surgery. In some cases, the success of the operation is directly correlated with the C-Arm and its ability to be repositioned to any desired position relative to the patient. In this paper, an integrated approach is provided for the automatic and accurate repositioning of a mobile C-Arm. The development of a C-Arm prototype is explained through the use of computer-aided design and manufacturing. To automatically reposition the C-Arm, a two-step integrated approach is introduced that uses motion capture systems and artificial intelligence-based repositioning. In the first step, the C-Arm is repositioned using Vicon motion capture along with a virtual platform and graphic user interface. In the second step, the accuracy of the repositioning of the C-Arm is further improved by incorporating a deep learning convolutional neural network with image processing and point feature matching. Key results indicate successful integration of the proposed method with the C-Arm prototype for the purpose of automatic and accurate repositioning.

Safety and Feasibility of Performing Fenestrated Endovascular Abdominal Aneurysm Repair Using a Portable C-arm Without Fusion Technology: A Single-Center Experience.

ObjectiveMost centers performing fenestrated endovascular aneurysm repair (F-EVAR) use hybrid rooms with fusion technology for mapping. We present our experience of successfully performing F-EVAR using C-arm without fusion technology.MethodsDuring the period of January 2016 to October 2018, data were collected from a prospectively maintained F-EVAR database at our tertiary care institute. The primary endpoint was technical success, and the secondary outcomes measured were short- and midterm clinical success (both defined by the Society for Vascular Surgery reporting standards), blood loss, radiation dose, operative time, postoperative endoleaks, aneurysm rupture, endograft patency, and complications.ResultsWe performed 11 F-EVARs during the study period in five (45.5%) males and six (54.5%) females, with a mean age of 75+8 years. All procedures were performed under general anesthesia using OEC 9900 Elite Mobile C-arm (GE Healthcare, Chicago, IL, USA) without the use of fusion technology. Three patients had planned preoperative open procedures for access due to prior cutdown or bypass. Technical success was achieved in all 11 (100%) cases. The mean length of stay was 5+2 days, and the mean follow-up was 7.5+6.5 months. The mean procedure time was 301+167 minutes, and the mean blood loss was 361+233 mL. Mean fluoroscopy time was 72+31 minutes, and the mean radiation exposure time was 2,160+930 mGy. No patients required intraoperative transfusion. Thirty-day (short term) clinical success was achieved in 10 (90.0%), cases whereas six-month (midterm) clinical success was achieved in 7 (77.7%) patients. Branch vessel patency was 11 (100%) at 30 days and 9 (81.8%) at six months, and primary endograft patency was 100% (11) at six months. We had no perioperative mortality or major adverse cardiac event at 30 days. Thirty-day postoperative morbidity included readmission for pulmonary edema from cardiac failure in one patient. Two patients had clinically insignificant silent cardiac enzyme elevation. Three patients had re-interventions performed during the mean follow-up period. Two patients developed renal stent thrombosis resulting in renal insufficiency, which is defined as an increase in creatinine concentration ≥0.5 mg/dL, without the need for dialysis. One type II endoleak was identified postoperatively that required trans-lumbar embolization. No type I or III endoleaks were identified during the study period. Asymptomatic common femoral artery thrombosis was seen on follow-up imaging in one patient.ConclusionsWe conclude that F-EVAR can be safely performed using C-arm without the use of fusion technology. Its utility can be expanded to centers with appropriate skill set but no hybrid technology

Comparing Mobile C-Arm with a Hybrid Operating Room for Imaging in Fenestrated Stent-Graft Endovascular Abdominal Aortic Aneurysm Repair

To evaluate the advantages of a hybrid operating room (OR) (group 2) compared with a fluoroscopic mobile C-arm (group 1) during fenestrated stent-graft endovascular aneurysm repair (f-EVAR). This single-center study retrospectively analyzed prospectively collected data of consecutive patients treated with f-EVAR for short-necked, juxtarenal, and suprarenal aortic aneurysms between January 2006 and July 2016. Primary end points were technical success and perioperative complications. Secondary end points included 30-day and 1-year mortality as well as target vessel patency. About 96 patients were treated (85 men; 74.1±6.3years); 46 patients (48%) belonging to group 1 and 50 (52%) patients belonging to group 2. Technical success was achieved in 92.7% of the procedures (group 1 91.3% vs. group 2 94%, P=0.72). Significantly more complex interventions were performed in group 2 (n=38 of 50) compared with group 1 (n=14 of 46; P<0.001), in which primarily renal f-EVAR interventions were performed. In group 2, significantly less contrast was used (median 150mL vs. 100mL; P<0.001). The 30-day mortality in group 1 was 9% and 2% in group 2 (P=0.14), and 1-year survival was also not significantly different between both groups. Target visceral vessel primary patency was significantly higher in group 1 (87.6% vs. 85.5% [P=0.006] and 83.8% vs. 78.3% [P=0.03]) at 6 and 12months, respectively). There was no significant difference in renal artery primary patency at 6 and 12months. Immediate and 1-year outcomes after f-EVAR for abdominal aortic aneurysm were comparable using a hybrid OR compared with a mobile C-arm, despite the use of significantly more complex stent grafts in the patients treated in the hybrid OR. The use of a hybrid OR may assist in achieving satisfying results in complex f-EVAR.

Assessing Femoral Rotation: A Survey Comparison of Techniques.

To compare 3 common techniques for assessing femoral malrotation through a response analysis. Ten intact human cadaveric pelvis-to-knee specimens were used to create a fracture model. A mobile C-arm x-ray system was used to capture images of an intact control femur and a contralateral test femur on each specimen. A midshaft femoral osteotomy was created on the test femur and it was then internally and externally rotated in 5-degree intervals up to 20 degrees. Images were obtained and stored at each increment of malrotation. Eight surveys of 20-paired images each were generated and presented for surgeon review. Accuracy of predicting femoral malrotation using the true lateral technique (TLT), neck horizontal angle (NHA) method, and lesser trochanter profile (LTP) was measured. Eighty-five surgeons completed a survey with 80 surgeons (94%) acknowledging the use of a described fluoroscopic method for assisting with rotational alignment. Surgeons correctly accepted a fracture rotated less than 20 degrees and rejected a fracture rotated 20 degrees or more 63% of the time. The ability to correctly identify 20 degrees of malrotation varied per technique used to assess rotation. With the LTP and NHA method, 67% of surgeons responded correctly. Surgeons performed significantly worse when using the TLT with only 53% providing correct responses (P < 0.0001). Surgeons using described fluoroscopic methods to identify acceptable rotation in femoral shaft fractures are correct 63% of the time. The LTP and NHA techniques are equally reliable and more effective than the TLT at detecting clinically significant femoral malrotation.

First experiences with intraoperative CT in navigated sacroiliac (SI) instrumentation: An analysis of 25 cases and comparison with conventional intraoperative 2D and 3D imaging

BackgroundIntraoperative imaging is regularly used for intraoperative reduction control and evaluation of the implant position in trauma surgery. 2D imaging is limited, especially in complex anatomical regions such as the pelvis. The introduction of mobile 3D C-arms (CBCT: cone-beam computed tomography) has significantly improved intraoperative assessment. Nevertheless, there are still limitations regarding the field of view and metal artifacts. The purpose of this study was to evaluate the potential of intraoperative computed tomography (iCT) in surgical treatment of sacroiliac (SI) injuries. MethodsTwenty-five cases with injuries of the posterior pelvic ring involving the SI region that were surgically treated with navigated SI screws using the mobile iCT Airo (Brainlab, Munich, Germany) were analysed. Subsequently, the data were compared with historical control groups (CBCT with and without navigation; 2D fluoroscopy only). ResultsThe average score for subjective image quality achieved using the Likert scale is significantly higher for the iCT (4.48 ± 0.65) than for the CBCT (3.04 ± 0.69) with p = 0.00. The average duration of surgery using iCT was 189.32 ± 88.64 min, which was not significantly different from the control groups (p = 0.14 - 0.70). The average fluoroscopy time using iCT was 81.96 ± 97.34 s, which was significantly shorter than in all of the control groups (p = 0.00 - 0.03).The rate for postoperatively detected complications after using iCT was 0% (n = 0). Compared with the 2D-only control group (25%; n = 1), there is a significant difference (p = 0.01). The remaining two control groups showed no significant differences (p = 0.09 - 0.19). ConclusionsThe iCT provides excellent image quality that allows reliable assessment of fracture reduction and implant placement even in complex anatomical regions. The radiation exposure for the medical staff is reduced by decreasing the fluoroscopy time without significantly prolonging the surgical time. Overall, the possibility of intraoperative correction improves clinical outcome and patient treatment in the long term.

Evaluation of image quality and task performance for a mobile C-arm with a complementary metal-oxide semiconductor detector.

We assessed interventional radiologists' task-based image quality preferences for two- and three-dimensional images obtained with a complementary metal-oxide semiconductor (CMOS) flat-panel detector versus a hydrogenated amorphous silicon (a-Si:H) flat-panel detector. CMOS and a-Si:H detectors were implemented on identical mobile C-arms to acquire radiographic, fluoroscopic, and cone-beam computed tomography (CBCT) images of cadavers undergoing simulated interventional procedures using low- and high-dose settings. Images from both systems were displayed side by side on calibrated, diagnostic-quality displays, and three interventional radiologists evaluated task performance relevant to each image and ranked their preferences based on visibility of pertinent anatomy and interventional devices. Overall, CMOS images were preferred in fluoroscopy ( ) and CBCT ( ), at low-dose settings ( ), and for tasks associated with high levels of spatial resolution [e.g., fine anatomical details ( ) and assessment of interventional devices ( )]. No significant difference was found for fluoroscopic imaging tasks emphasizing temporal resolution ( ), for radiography tasks ( ), when using high-dose settings ( ), or tasks involving general anatomy ( ). The image quality preferences are consistent with reported technical advantages of CMOS regarding finer pixel size and reduced electronic noise.

A mobile isocentric C-arm for intraoperative cone-beam CT: Technical assessment of dose and 3D imaging performance.

To characterize the radiation dose and three-dimensional (3D) imaging performance of a recently developed mobile, isocentric C-arm equipped with a flat-panel detector (FPD) for intraoperative cone-beam computed tomography (CBCT) (Cios Spin 3D, Siemens Healthineers) and to identify potential improvements in 3D imaging protocols for pertinent imaging tasks. The C-arm features a 30×30cm2 FPD and isocentric gantry with computer-controlled motorization of rotation (0-195°), angulation (±220°), and height (0-45cm). Geometric calibration was assessed in terms of 9 degrees of freedom of the x-ray source and detector in CBCT scans, and the reproducibility of geometric calibration was evaluated. Standard and custom scan protocols were evaluated, with variation in the number of projections (100-400) and mAs per view (0.05-1.65mAs). Image reconstruction was based on 3D filtered backprojection using "smooth," "normal," and "sharp" reconstruction filters as well as a custom, two-dimensional 2D isotropic filter. Imaging performance was evaluated in terms of uniformity, gray value correspondence with Hounsfield units (HU), contrast, noise (noise-power spectrum, NPS), spatial resolution (modulation transfer function, MTF), and noise-equivalent quanta (NEQ). Performance tradeoffs among protocols were visualized in anthropomorphic phantoms for various anatomical sites and imaging tasks. Geometric calibration showed a high degree of reproducibility despite ~19mm gantry flex over a nominal semicircular orbit. The dose for a CBCT scan varied from ~0.8-4.7mGy for head protocols to ~6-38mGy for body protocols. The MTF was consistent with sub-mm spatial resolution, with f10 (frequency at which MTF=10%) equal to 0.64mm-1 , 1.0mm-1 , and 1.5mm-1 for smooth, standard, and sharp filters respectively. Implementation of a custom 2D isotropic filter improved CNR~50-60% for both head and body protocols and provided more isotropic resolution and noise characteristics. The NPS and NEQ quantified the 3D noise performance and provided a guide to protocol selection, confirmed in images of anthropomorphic phantoms. Alternative scan protocols were identified according to body site and task - for example, lower-dose body protocols (<3mGy) sufficient for visualization of bone structures. The studies provided objective assessment of the dose and 3D imaging performance of a new C-arm, offering an important basis for clinical deployment and a benchmark for quality assurance. Modifications to standard 3D imaging protocols were identified that may improve performance or reduce radiation dose for pertinent imaging tasks.

Influence of syndesmotic injuries and posterior malleolar ankle fractures on fibula position in the ankle joint: a cadaveric study.

The aim of this study was to identify to what extent a dissection of the syndesmosis and an avulsed posterior edge of the tibia can change the tibiofibular diastasis and fibular rotation. Three-dimensional scans with a mobile C-arm of 22 cadaver legs were taken of the intact fibula, after dissection of the anterior part of the syndesmosis and the interosseous membrane, osteotomy of the posterior malleolus, and osteosynthesis. The tibiofibular diastasis as well as the angle of fibular rotation was identified in the four steps and the means compared to each other using a t test for paired samples. The distinction between the intact fibula vs. the osteotomy of the posterior tibia was 0.082 ± 0.332mm for the tibiofibular distance in the incisura tibiofibularis (p 0.261) and 0.046 ± 0.486 degrees for the angle of the fibular rotation (p 0.665). Neither the dissection of the syndesmosis nor the osteotomy of the posterior malleolus significantly influenced the position of the fibula in the incisura tibiofibularis in the cadaveric model. However, in the nonweight-bearing situation, a lesion of the syndesmotic complex might not be evident in intraoperative three-dimensional imaging.

Scatter Radiation Intensities during Transforaminal Lumbar Interbody Fusion Using a Mobile C-arm System

The purpose of this study was to measure the scatter radiation intensity during transforaminal lumbar interbody fusion using a mobile C-arm system (Arcadis Orbic 3D; Siemens) and minimize radiation exposure. Dosimetry was performed with anterior-posterior and lateral continuous fluoroscopy, and cone beam computed tomography (CT). A scaffold tower (L: 300 cm×W: 200 cm×H: 150 cm) was built with radiation-resistant paper cylinders at intervals of 50 cm and plastic joints over the bed, and 100 optically stimulated luminescence dosimeters (nanoDot; Nagase Landauer) were placed on each joint. A human torso phantom from head to pelvis (Kyoto Kagaku) was positioned on the bed in a prone position. The scatter radiation dose in a lateral view was highest on the X-ray tube side at the height of 100 cm (170.5 μGy/min). The scatter radiation dose increased significantly on the X-ray tube side during lateral continuous fluoroscopy. Continuous change of surgeons' standing positions is important to minimize radiation exposure received by a specific surgeon.

Scattered Radiation Dose Measurement of the Mobile C-arm X-ray Device in the Operating Room

Scattered Radiation Dose Measurement of the Mobile C-arm X-ray Device in the Operating Room

Radiation Protection of a Patient Undergoing an Orthopedic Procedure by Using a Mobile C-Arm X-Ray System

Modern medicine is unthinkable without X-rays. Accurate diagnosis, leading to effective treatment, is largely based on precise X-ray examinations. The creation of new, modern equipment and various medical procedures that meet the increased requirements are a priority in our time. X-ray examinations are of particular importance for the orthopedic and traumatological clinics, where they provide information about presence of a fracture in the patient’s body, about the concrete operation performed or about the effect of a suitable treatment. Along with their benefits X-rays have also a harmful effect. This requires special care to protect from this radiation. In this direction, research is constantly being done to improve the quality of radiation protection. Park MR, Lee KM and co-authors, compare the dose load obtained using C-arm and O-arm X-ray systems (which have the capability of combined 2D fluoroscopy and 3D computed tomography imaging). In their study, an orthopedic surgical procedure using C-arm and O-arm systems in 2D fluoroscopy modes was simulated. The radiation doses to susceptible organs of the operators were investigated. He results obtained show that the O-arm system delivered higher doses to the sensitive organs of the operator in all configurations [1]. The article of Stephen Balte briefly reviews the available technologies for measuring or estimation of patient skin dose in the interventional fluoroscopic environment, created by various X-ray equipment including C-arm systems. Given that many patients require multiple procedures, this documentation also aids in the planning of follow up visits [2]. Chong Hing Wong, Yoshihisa Kotani and co-authors evaluate the radiation exposures (RE) to the patient and surgeon during minimally invasive lumbar spine surgery with instrumentation using C-arm image intensifier or O-arm intraoperative CT. The results they get are in favor of the O-arm system [3]. The article “Virtual fluoroscopy for intraoperative C-arm positioning and radiation dose reduction” discusses positioning of an intraoperative C-arm system to achieve clear visualization of a particular anatomical feature by a system for virtual fluoroscopy (called FluoroSim) that could dramatically reduce time and received dose during the procedures. FluoroSim was found to reduce the radiation exposure required for C-arm positioning without reducing positioning time or accuracy, providing a potentially valuable tool to assist surgeons [4]. In our study, we performed practical measurements to show how the patient can be treated by applying most effective radiation protection when using a mobile C-arm X-ray system. For the study, we used exposure upon a phantom placed on the patient’s table. For an X-ray shielding, we used a protective apron with a lead equivalent of 1 mm, placed in two layers on the phantom. In each subsequent series of exposures, the protective apron was placed on the phantom, in a different position relative to the X-ray beam. The general conclusion of our study is that in order to obtain maximum protection from scattered radiation when using C-arm X-ray systems, the patient must be protected by a shielding with a suitable lead equivalent for the procedure performed which must be placed between patient’s body and X-ray tube, perpendicular to the X-ray beam pointed toward the region of interest.

Toward an End-to-End Calibration for Mobile C-Arm in Combination with a Depth Sensor for Surgical Augmented Reality Applications.

C-arm X-ray imaging is commonly applied in operating rooms for guiding orthopedic surgeries. Augmented Reality (AR) with C-arm X-ray images during surgery is an efficient way to facilitate procedures for surgeons. However, the accurate calibration process for surgical AR based on C-arm is essential and still challenging due to the limitations of C-arm imaging systems, such as instability of C-arm calibration parameters and the narrow field of view. We extend existing methods using a depth camera and propose a new calibration procedure consisting of calibration of the C-arm imaging system, and 3D/2D calibration of an RGB-D camera and C-arm system with a new method to achieve reliable data and promising accuracy and, at the same time, consistent with standard surgical protocols. For the calibration procedure, we apply bundle adjustment equations with a 3D designed Lego multi-modal phantom, in contrast to the previous methods in which planar calibration phantoms were applied. By using our method, the visualization of the X-ray image upon the 3D data was done, and the achieved mean overlay error was 1.03 mm. The evaluations showed that the proposed calibration procedure provided promising accuracy for AR surgeries and it improved the flexibility and robustness of existing C-arm calibration methods for surgical augmented reality (using C-arm and RGB-D sensor). Moreover, the results showed the efficiency of our method to compensate for the effects of the C-arm movement on calibration parameters. It was shown that the obtained overlay error was improved for the non-zero rotation movement of C-arm by using a virtual detector.

Tevar-Deployment Based on Digital Touch in case of Descending Aortic Rupture

Introduction - Thoracic endovascular aortic repair (TEVAR) is at present the preferred technique for treatment of a variety of thoracic aortic pathologies. Methods - We present a case of thoracic aortic rupture in which fluoroscopy was not available and transfer to an angiosuite was not possible. Results - A 66-year old female patient without any cardiovascular history presented herself at the emergency department of another hospital because of shortness of breath, progressive fatigue and weight loss with night sweats and chills. Chest X-ray showed a widened mediastinum. Additional CT-angiography revealed a multilobulated mycotic aneurysm just distal to the brachiocephalic trunk. Echocardiography was normal. C-reactive protein was 170mg/l. Conservative treatment with antibiotics was started. After four days, the patient was transferred to our hospital because of progressive growth of the aneurysm for which she had an aortic arch replacement (Gelweave graft 30mm, Vascutek) with supra-aortic branch reimplantation. Within the first 24 hours after cardiac surgery, the patient developed a hemodynamic collapse resulting in cardiac arrest. CPR was performed for more than 40 minutes before achieving sinus rhythm. The patient was rushed to the OR because of massive hemothorax. After establishing extracorporeal circulation (ECC), the diagnosis of descending aortic rupture was made. Open surgical repair was not deemed possible. The patient could not be transferred to the hybrid angiosuite and fluoroscopy with a mobile C-arm was not possible. A 0.035 guidewire was introduced through a 5Fr sheath in the left femoral artery. Transesophageal echocardiography (TEE) confirmed the position of the guidewire near the aortic valve. A Captivia 28*150mm endograft (Gore) was positioned over the rupture and deployed based on echocardiography and palpation of the descending aorta. Bleeding control was only achieved after deployment of a second Captivia 31*150mm endograft (Gore) more proximally. After weaning of the ECC, the patient was transferred to the hybrid angiosuite. Angiography showed patent supra-aortic branches, no endoleak, an overlap of both endografts of more than 5 cm and a patent celiac artery. The patient was weaned off the ventilator and recovered progressively at the intensive care unit. No neurological sequelae were present. Conclusion - This case illustrates that TEVAR should not be denied to patients in case of an emergency situation when fluoroscopy is not available. TEE provides relevant information and is not only an adjunct to fluoroscopy during TEVAR. In the absence of fluoroscopy, it can serve as the primary imaging technique.

Influence of reduction quality on functional outcome and quality of life in treatment of tibial plafond fractures: a retrospective cohort study

BackgroundThe aim of the study was to evaluate the impact of reduction quality, using intraoperative 3D imaging, on quality of life and functional outcome in the operative treatment of tibial plafond fractures.MethodsA group of patients with tibial plafond fractures was re-examined. The operative treatment was performed between September 2001 and October 2011. The follow-up examination was at least 2 years after the final surgical procedure. Final reduction result was assessed intraoperatively using a mobile 3D C-arm. A categorization with regard to descriptive parameters as well as type and size of joint surface irregularities was performed. Follow-up results were evaluated using: Olerud and Molander (O & M) score, Short-Form-36 (SF-36) score, movement deficit, Kellgren and Lawrence grade of osteoarthritis, and pain intensity.Results34 patients with operatively treated tibial plafond fracture could be re-examined. Reduction quality had the greatest influence on functional result measured by the O & M score (p = 0.001) and the PCS domain of the SF-36 score (p = 0.018).Significant differences with regard to O & M score (p = 0.000), SF-36 score (p = 0.001 to p = 0.02; without MCS domain), movement deficit (p = 0.001), grade of osteoarthritis (p = 0.005) and pain (p = 0.001) could be verified under consideration of the reduction quality. The group with the anatomically more accurate reduction also showed a better result for clinical follow-up and quality of life. Furthermore, it is not the type of joint surface irregularity that is always decisive, but rather the size.ConclusionsDespite other relevant factors, it appears that reduction quality –which can be analyzed with intraoperative 3D imaging– plays the most important role in postoperative quality of life and functional outcome. Corrections should therefore be performed on joint surface irregularities with a size above 2 mm.

Online mobile C-arm calibration using inertial sensors: a preliminary study in order to achieve CBCT.

Cone beam computed tomography (CBCT) became increasingly popular over the last years. It allows more accurate diagnosis and treatment planning with a lower effective radiation dose. However, volume reconstruction algorithms require a very precise knowledge of the imaging geometry. Due to mechanical instabilities, mobile C-arms are incompatible with existing tomography algorithms. Therefore, C-arm online calibration is essential in order to achieve an accurate volume reconstruction. We present an online calibration method for mobile C-arms. It is based on tracking the detector and the X-ray source of the C-arm using three-axis gyroscopes and accelerometers. It aims to be precise and noninvasive. The performance of the calibration algorithm is evaluated in regard to the precision of the sensors and to whether or not dynamic models are considered. In addition, we present an algorithm which propagate the errors from the positions and orientations estimates to the 2D projections on the detector plane. Thus, we can evaluate the impact of the estimation errors on the acquired images. The experiments are conducted on an experimental C-arm. The reached accuracy is [Formula: see text] for orientation and [Formula: see text] for position. These errors propagate as an error of [Formula: see text] for the 2D projections on the detector plane. The proposed calibration algorithm achieves an accuracy comparable to the precision of existing calibration methods. The required angle accuracy by CBCT algorithms is reached. However, improvements are needed to achieve the required position precision. The in-plane translations of the X-ray source and the detector are the most crucial parameters to estimate in order to conduct CBCT on mobile C-arms.

Distal radioulnar joint instability with three different injury patterns assessed by three-dimensional C-arm scans: a cadaveric study.

The aim of this study was to establish a radiographic method for detecting distal radioulnar joint instability intraoperatively. We created three successive instabilities in 12 intact Thiel-fixed upper limb specimens: lesion of the triangular fibrocartilage complex, Galeazzi injury and Essex-Lopresti injury. We made three-dimensional scans of the wrists in pronation and supination with a mobile C-arm. We used four validated measurement methods to quantify ulnar migration in the standard axial planes: the radioulnar line method, the subluxation ratio method, the epicentre method and the radioulnar ratio method. All types of instability showed significantly increased migration of the ulna compared with the control group. The subluxation ratio and the radioulnar ratio methods showed the highest sensitivity and specificity in detecting the instabilities. We conclude that these two methods are feasible for radiographically assessing distal radioulnar joint instability. Instability may be assumed if the migration of the ulna in the sigmoid notch is at least 45% of the length of the sigmoid notch, in which case wire transfixation of the distal radioulnar joint is advised.

Comparison of Patient Radiation Dose and Contrast Use during EVAR in a Dedicated Hybrid Vascular OR and Mobile Imaging

The aim of the study is to determine whether performing endovascular aortic aneurysm repair (EVAR) in a dedicated vascular hybrid operating room (OR) is associated with a decreased patient radiation and contrast dose compared with mobile C-arm imaging in a conventional OR. This is a retrospective study of patients undergoing standard EVAR from 2009-2016. "Standard EVAR" was defined as the elective EVAR performed with bifurcated graft for infrarenal aneurysm with no iliac aneurysms. Patients were divided into 2 groups. Group 1 included EVARs performed in conventional theater with a mobile C-arm (January 2009 to June 2012) and group 2 EVARs performed in the dedicated vascular hybrid OR (July 2012 to December 2016). Data collected included patient demographics, aneurysm diameter, neck length, radiation dose, screening time, and contrast use of each patient. There were 286 patients, 78 and 208 patients in group 1 and 2, respectively. There was no difference in age (77.6years [76.3-78.9] vs. 76.6years [75.9-77.9], P>0.05), body mass index (26.5kg/m2 [25.1-28.0] vs. 27.9kg/m2 [27.1-28.7] P>0.05), and mean aneurysm diameter (6.48cms [6.13-6.82] vs. 6.81cms [6.0-7.7], P>0.05) between groups. Patients in group 2 received approximately half the mean radiation dose (16,807cGycm2 [±11,078] vs. 8,233cGycm2 [±7,471], P<0.001), shorter fluoroscopy time (36.02min [±21.3] vs. 26.96min [±19], P=0.001), and less contrast use (114mls [±44.2] vs. 158mls [±63.9], P<0.001). Performing EVAR in a dedicated vascular Hybrid OR may be associated with a lower patient radiation dose, shorter screening time, and less contrast use than performing EVAR in a conventional OR.