A novel tool for three-dimensional roadmapping reduces radiation exposure and contrast agent dose in complex endovascular interventions.

OBJECTIVE: The volume and complexity of endovascular procedures are increasing. Multidetector computed tomography (CT) made precise three-dimensional (3D) planning of these procedures possible, but intraoperative imaging, even with the use of modern flat-panel detectors, is limited to two dimensions. Flat detectors, however, allow C-arm cone-beam CT. This technology can be used to generate a 3D data set that can be fused with a preoperative high-resolution CT scan, thus generating a live 3D roadmap. We hypothesized that use of a novel image fusion software, VesselNavigator (Philips Healthcare, Best, The Netherlands), facilitates precise and expeditious procedures and therefore reduces radiation exposure and contrast agent dose. METHODS: A retrospective review of patients undergoing standard aortobi-iliac endovascular aneurysm repair at our institution between January 2011 and April 2014 was performed. Conventional imaging was compared with VesselNavigator-assisted imaging, and a matched analysis based on body mass index (BMI) was performed because of the dependence of radiation dose on body habitus. Outcome parameters were procedure time, fluoroscopy time, radiation, and contrast agent dose. RESULTS: A total of 75 patients were identified. After matching based on BMI, control and VesselNavigator groups each had 16 patients with BMI of 27.0 ± 3.6 kg/m(2) and 27.0 ± 3.6 kg/m(2), respectively (mean ± standard deviation). R(2) was 6.37 × 10(-7). Radiation dose measured as air kerma was lower with VesselNavigator (1067 ± 470.4 mGy vs 1768 ± 696.2 mGy; P = .004). Fluoroscopy time was shorter (18.4 ± 6.8 minutes vs 26.8 ± 10.0 minutes; P = .01) and contrast agent dose was lower (37.4 ± 21.3 mL vs 77.3 ± 23.0 mL; P < .001) with VesselNavigator compared with control. Procedure time was also shorter with VesselNavigator (80.4 ± 21.2 minutes vs 110.0 ± 29.1 minutes; P = .005). CONCLUSIONS: Image fusion using VesselNavigator enhances the functionality of conventional fluoroscopy in standard endovascular aneurysm repair. It reduces radiation exposure to patients and providers. It also limits the amount of contrast agent and shortens the overall procedure length. The benefit of this technology is demonstrated on this typically straightforward procedure but may be even more useful for complex procedures.

Clinical experience with cone-beam CT navigation for tumor ablation.

PURPOSE: To describe clinical use and potential benefits of cone-beam computed tomography (CT) navigation to perform image-guided percutaneous tumor ablation. MATERIALS AND METHODS: All ablations performed between February 2011 and February 2013 using cone-beam CT navigation were included. There were 16 patients who underwent 20 ablations for 29 lesions. Cone-beam CT ablation planning capabilities include multimodality image fusion and tumor segmentation for visualization, depiction of the predicted ablation zones for intraprocedural planning, and segmentation of the ablated area for immediate verification after treatment. Number and purpose of cone-beam CT scans were examined. The initial ablation plan, defined as number of probes and duration of energy delivery, was recorded for the 20 of the 29 lesions ablated. Technical success and local recurrences were recorded. Primary and secondary effectiveness rates were calculated. RESULTS: Image fusion was used for 16 lesions, and intraprocedural ultrasound was used for 4 lesions. Of the 20 ablations, where the ablation plans were recorded, there was no deviation from the plan in 14 ablations. In the remaining 6 ablations, iterative planning was needed for complete tumor coverage. An average of 8.7 cone-beam CT scans ± 3.2 were performed per procedure, including 1.3 ± 0.5 for tumor segmentation and planning, 1.7 ± 0.7 for probe position confirmation, and 3.9 ± 2 to ensure complete coverage. Mean follow-up time was 18.6 months ± 6.5. Ablations for 28 of 29 lesions were technically successful (96.5%). Of ablations performed with curative intent, technical effectiveness at 1 month was 25 of 26 lesions (96.1%) and 22 of 26 lesions (84.6%) at last follow-up. Local tumor progression was observed in 11.5% (3 of 26 lesions). CONCLUSIONS: Cone-beam CT navigation may add information to assist and improve ablation guidance and monitoring.

Effect of real-time radiation dose feedback on pediatric interventional radiology staff radiation exposure.

PURPOSE: To measure and compare individual staff radiation dose levels during interventional radiologic (IR) procedures with and without real-time feedback to evaluate whether it has any impact on staff radiation dose. MATERIALS AND METHODS: A prospective trial was performed in which individuals filling five different staff roles wore radiation dosimeters during all IR procedures during two phases: a 12-week "closed" phase (measurements recorded but display was off, so no feedback was provided) and a 17-week "open" phase (display was on and provided real-time feedback). Radiation dose rates were recorded and compared by Mann-Whitney U test. RESULTS: There was no significant difference in median procedure time, fluoroscopy time, or patient dose (dose-area product normalized to fluoroscopy time) between the two phases. Overall, the median staff dose was lower in the open phase (0.56 µSv/min of fluoroscopy time) than in the closed phase (3.01 µSv/min; P < .05). The IR attending physician dose decreased significantly for procedures for which the physicians were close to the patient, but not for ones for which they were far away. CONCLUSIONS: A radiation dose monitoring system that provides real-time feedback to the interventional staff can significantly reduce radiation exposure to the primary operator, most likely by increasing staff compliance with use of radiation protection equipment and dose reduction techniques.

Cone-beam computed tomography fusion and navigation for real-time positron emission tomography-guided biopsies and ablations: a feasibility study.

PURPOSE: To describe a novel technique for multimodality positron emission tomography (PET) fusion-guided interventions that combines cone-beam computed tomography (CT) with PET/CT before the procedure. MATERIALS AND METHODS: Subjects were selected among patients scheduled for a biopsy or ablation procedure. The lesions were not visible with conventional imaging methods or did not have uniform uptake on PET. Clinical success was defined by adequate histopathologic specimens for molecular profiling or diagnosis and by lack of enhancement on follow-up imaging for ablation procedures. Time to target (time elapsed between the completion of the initial cone-beam CT scan and first tissue sample or treatment), total procedure time (time from the moment the patient was on the table until the patient was off the table), and number of times the needle was repositioned were recorded. RESULTS: Seven patients underwent eight procedures (two ablations and six biopsies). Registration and procedures were completed successfully in all cases. Clinical success was achieved in all biopsy procedures and in one of the two ablation procedures. The needle was repositioned once in one biopsy procedure only. On average, the time to target was 38 minutes (range 13-54 min). Total procedure time was 95 minutes (range 51-240 min, which includes composite ablation). On average, fluoroscopy time was 2.5 minutes (range 1.3-6.2 min). CONCLUSIONS: An integrated cone-beam CT software platform can enable PET-guided biopsies and ablation procedures without the need for additional specialized hardware.

First experiences with the use of intraoperative 3D-RX for wrist surgery.

With the use of conventional C-arm fluoroscopy for hand surgery, suboptimal positioning of implants, K-wires, insufficient reconstructions and joint incongruities frequently remain unrevealed We prospectively compared the performance of the surgeon interpreted from conventional methods (2D fluoroscopy and direct visual and physical inspection) versus 3D imaging as well as the occurrence of revision surgeries based on post-op radiological findings. Twenty-four intraoperative findings based on 2D fluoroscopy and findings on direct visual and physical inspections were compared with intraoperatively acquired 3D-RX scans by means of a questionnaire. Moreover, record was kept of revision surgery (minimal three months follow up) for all patients treated with the aid of 3D-RX. A clear difference in findings was observed between the performance based on fluoroscopy and direct visual and physical inspection and that based on intraoperative 3D-RX for hand surgery (p < 0.05). Post-operative radiological examinations revealed that none of the 56 patients treated with the aid of 3D-RX needed revision surgery. Intraoperative 3D-RX provides information for the hand surgeon that is additional to the information acquired with conventional fluoroscopy. Intraoperative 3D-RX provides well defined images of the positioning of osteosynthesis material, of the spatial orientation of carpals, and of reconstruction of the wrist joint.

Migration of the ball electrode after cochlear implantation.

OBJECTIVE: To review the postoperative radiographic investigations of patients implanted with a cochlear implant. STUDY DESIGN: Retrospective case series. PATIENTS: Thirty-nine patients (22-77 yrs old) implanted for sensorineural deafness in the cochlear implants program of the Academic Medical Center of Amsterdam. INTERVENTION: Cochlear implantation with Cochlear Nucleus 24 Contour and Cochlear Nucleus Freedom (Cochlear Corp., Lane Cove, New South Wales, Australia) implant. RESULTS: This retrospective analysis of the postoperative computed tomographic scans showed that, in a large number of the implantations, the external ball electrode of the cochlear implant migrated from the insertion place toward the magnet of the receiver/stimulator unit of the implant. It seems that this migration of the external ball electrode does not influence the function of the cochlear implant and the result of the hearing rehabilitation in the short term. CONCLUSION: Because of the magnetic field of the receiver/stimulator unit of the cochlear implant and the magnet of the external transmitting coil of the speech processor, it seems to be possible that the extracochlear ball electrode can migrate in the space between the temporal bone and the temporal muscle during the postoperative healing phase. The importance of our observation is still not clear.

4D rotational x-ray imaging of wrist joint dynamic motion.

Current methods for imaging joint motion are limited to either two-dimensional (2D) video fluoroscopy, or to animated motions from a series of static three-dimensional (3D) images. 3D movement patterns can be detected from biplane fluoroscopy images matched with computed tomography images. This involves several x-ray modalities and sophisticated 2D to 3D matching for the complex wrist joint. We present a method for the acquisition of dynamic 3D images of a moving joint. In our method a 3D-rotational x-ray (3D-RX) system is used to image a cyclically moving joint. The cyclic motion is synchronized to the x-ray acquisition to yield multiple sets of projection images, which are reconstructed to a series of time resolved 3D images, i.e., four-dimensional rotational x ray (4D-RX). To investigate the obtained image quality parameters the full width at half maximum (FWHM) of the point spread function (PSF) via the edge spread function and the contrast to noise ratio between air and phantom were determined on reconstructions of a bullet and rod phantom, using 4D-RX as well as stationary 3D-RX images. The CNR in volume reconstructions based on 251 projection images in the static situation and on 41 and 34 projection images of a moving phantom were 6.9, 3.0, and 2.9, respectively. The average FWHM of the PSF of these same images was, respectively, 1.1, 1.7, and 2.2 mm orthogonal to the motion and parallel to direction of motion 0.6, 0.7, and 1.0 mm. The main deterioration of 4D-RX images compared to 3D-RX images is due to the low number of projection images used and not to the motion of the object. Using 41 projection images seems the best setting for the current system. Experiments on a postmortem wrist show the feasibility of the method for imaging 3D dynamic joint motion. We expect that 4D-RX will pave the way to improved assessment of joint disorders by detection of 3D dynamic motion patterns in joints.

Direct navigation on 3D rotational x-ray data acquired with a mobile propeller C-arm: accuracy and application in functional endoscopic sinus surgery.

Recently, three-dimensional (3D) rotational x-ray imaging has been combined with navigation technology, enabling direct 3D navigation for minimally invasive image guided interventions. In this study, phantom experiments are used to determine the accuracy of such a navigation set-up for a mobile C-arm with propeller motion. After calibration of the C-arm system, the accuracy is evaluated by pinpointing divots on a special-purpose phantom with known geometry. This evaluation is performed both with and without C-arm motion in between calibration and registration for navigation. The variation caused by each of the individual transformations in the calibration and registration process is also studied. The feasibility of direct navigation on 3D rotational x-ray images for functional endoscopic sinus surgery has been evaluated in a cadaver navigation experiment. Navigation accuracy was approximately 1.0 mm, which is sufficient for functional endoscopic sinus surgery. C-arm motion in between calibration and registration slightly degraded the registration accuracy by approximately 0.3 mm. Standard deviations of each of the transformations were in the range 0.15-0.31 mm. In the cadaver experiment, the navigation images were considered in good correspondence with the endoscopic images by an experienced ENT surgeon. Availability of 3D localization information provided by the navigation system was considered valuable by the ENT surgeon.

The Effect of Realtime Monitoring on Dose Exposure to Staff Within an Interventional Radiology Setting.

PURPOSE: The purpose of this study is to evaluate a new device providing real-time monitoring on radiation exposure during fluoroscopy procedures intending to reduce radiation in an interventional radiology setting. MATERIALS AND METHODS: In one interventional suite, a new system providing a real-time radiation dose display and five individual wireless dosimeters were installed. The five dosimeters were worn by the attending, fellow, nurse, technician, and anesthesiologist for every procedure taking place in that suite. During the first 6-week interval the dose display was off (closed phase) and activated thereafter, for a 6-week learning phase (learning phase) and a 10-week open phase (open phase). During these phases, the staff dose and the individual dose for each procedure were recorded from the wireless dosimeter and correlated with the fluoroscopy time. Further subanalysis for dose exposure included diagnostic versus interventional as well as short (<10 min) versus long (>10 min) procedures. RESULTS: A total of 252 procedures were performed (n = 88 closed phase, n = 50 learning phase, n = 114 open phase). The overall mean staff dose per fluoroscopic minute was 42.79 versus 19.81 µSv/min (p < 0.05) comparing the closed and open phase. Thereby, anesthesiologists were the only individuals attaining a significant dose reduction during open phase 16.9 versus 8.86 µSv/min (p < 0.05). Furthermore, a significant reduction of total staff dose was observed for short 51 % and interventional procedures 45 % (p < 0.05, for both). CONCLUSION: A real-time qualitative display of radiation exposure may reduce team radiation dose. The process may take a few weeks during the learning phase but appears sustained, thereafter.

CT angiography-fluoroscopy fusion imaging for percutaneous transapical access.

OBJECTIVES: The aim of this proof-of-principle study is to validate the accuracy of fusion imaging for percutaneous transapical access (TA). BACKGROUND: Structural heart disease interventions, including TA, are commonly obtained under fluoroscopic guidance, which lacks important spatial information. Computed tomographic angiography (CTA)-fluoroscopy fusion imaging can provide the 3-dimensional information necessary for improved accuracy in planning and guidance of these interventions. METHODS: Twenty consecutive patients scheduled for percutaneous left ventricular puncture and device closure using CTA-fluoroscopy fusion guidance were prospectively recruited. The HeartNavigator software (Philips Healthcare, Best, the Netherlands) was used to landmark the left ventricular epicardium for TA (planned puncture site [PPS]). The PPS landmark was compared with the position of the TA closure device on post-procedure CTA (actual puncture site). The distance between the PPS and actual puncture site was calculated from 2 fixed reference points (left main ostium and mitral prosthesis center) in 3 planes (x, y, and z). The distance from the left anterior descending artery at the same z-plane was also assessed. TA-related complications associated with fusion imaging were recorded. RESULTS: The median (interquartile range [IQR]) TA distance difference between the PPS and actual puncture site from the referenced left main ostium and mitral prosthesis center was 5.00 mm (IQR: 1.98 to 12.64 mm) and 3.27 mm (IQR: 1.88 to 11.24 mm) in the x-plane, 4.48 mm (IQR: 1.98 to 13.08 mm) and 4.00 mm (IQR: 1.62 to 11.86 mm) in the y-plane, and 5.57 mm (IQR: 3.89 to 13.62 mm) and 4.96 mm (IQR: 1.92 to 11.76 mm) in the z-plane. The mean TA distance to the left anterior descending artery was 15.5 ± 7.8 mm and 22.7 ± 13.7 mm in the x- and y-planes. No TA-related complications were identified, including evidence of coronary artery laceration. CONCLUSIONS: With the use of CTA-fluoroscopy fusion imaging to guide TA, the actual puncture site can be approximated near the PPS. Moreover, fusion imaging can help maintain an adequate access distance from the left anterior descending artery, thereby, potentially reducing TA-related complications.

Dual-phase cone-beam computed tomography to see, reach, and treat hepatocellular carcinoma during drug-eluting beads transarterial chemo-embolization.

The advent of cone-beam computed tomography (CBCT) in the angiography suite has been revolutionary in interventional radiology. CBCT offers 3 dimensional (3D) diagnostic imaging in the interventional suite and can enhance minimally-invasive therapy beyond the limitations of 2D angiography alone. The role of CBCT has been recognized in transarterial chemo-embolization (TACE) treatment of hepatocellular carcinoma (HCC). The recent introduction of a CBCT technique: dual-phase CBCT (DP-CBCT) improves intra-arterial HCC treatment with drug-eluting beads (DEB-TACE). DP-CBCT can be used to localize liver tumors with the diagnostic accuracy of multi-phasic multidetector computed tomography (M-MDCT) and contrast enhanced magnetic resonance imaging (CE-MRI) (See the tumor), to guide intra-arterially guidewire and microcatheter to the desired location for selective therapy (Reach the tumor), and to evaluate treatment success during the procedure (Treat the tumor). The purpose of this manuscript is to illustrate how DP-CBCT is used in DEB-TACE to see, reach, and treat HCC.

Spread of excitation measurements for the detection of electrode array foldovers: a prospective study comparing 3-dimensional rotational x-ray and intraoperative spread of excitation measurements.

OBJECTIVE: The optimal positioning of electrode arrays in the cochlea is extremely important. Our standard approach is to use a 3-dimensional rotational x-ray for the intraoperative determination of the position of the electrode array. We wanted to see if spread of excitation (SOE) is useful for determining the electrode array position within the cochlea. STUDY DESIGN: Prospective blind study design. SETTING: Tertiary University Referral Center (Cochlear Implantation Center Amsterdam-Academic Medical Center, University of Amsterdam). PATIENTS: Seventy-two implanted ears with a Cochlear Freedom device. INTERVENTION: After cochlear implantation, we compared the 3-dimensional rotational x-ray imaging and SOE measurements. The investigators were blinded for the intraoperative surgeon findings and also for the imaging findings. OUTCOME MEASURE(S): Electrode array foldovers within the cochlea and the reliability of the SOE measurements. RESULTS: We placed implants in 72 ears in this study, and all procedures seemed to be surgically uneventful. To our surprise, we discovered 4 electrode foldovers in this group. Of the 4 foldovers, 3 were corrected intraoperatively. CONCLUSION: We found that intraoperative imaging and/or electrophysiologic measurements such as the SOE provide very useful information regarding electrode position within the cochlea. Spread of excitation is effective in detecting electrode array foldovers if the audiologist is experienced. Some software modifications are suggested.

Detection of in vivo dynamic 3-D motion patterns in the wrist joint.

We present a method for measurement dynamic in vivo carpal motion patterns. The method consists of a 4-D rotational X-ray (RX) with improved image quality and image processing for accurate detection in vivo wrist motion measurements. Dynamic 3-D imaging yields a number of volume reconstructions of the wrist at different phases of its cyclic motion. Next, the carpal reconstructions are registered to their static acquired and segmented counterpart in all phases. With this information, the relation between the applied motion and carpal kinematic behavior is acquired, i.e., the motion patterns. We investigated the precision of the image acquisition and processing and tested it on three healthy subjects. The precision of the image acquisition and image processing is in the range of submillimeters and subdegrees, respectively, which is better than existing systems and sufficient for clinical investigations. Reproducibility measurements show some more deviation ( > 1 degrees). This method was tested on four human volunteers and agrees for the greater part with previously done invasive and nondynamic measurements. In vivo motion pattern measurement with 4-D-RX imaging and processing is accurate and noninvasive. The motion patterns can reveal disorders that could not have been detected in either video fluoroscopy, computed tomography, or MRI.