The use of state-of-the-art technology in emergencies enables fast assessment of the situation. Modern rescue robots, but also rescuers with camera systems, record vast amounts of image data. In ...addition to the benefits for rescue operations, a quick overview based on this data can help medical staff in the search for suitable treatment strategies. However, such data must be examined and fused into an intuitive display. In this work, exemplary image streams of RGB-D cameras are searched for victims and transferred into separate 3D models per detected person for subsequent intuitive viewing, rotating, and zooming. The method was tested and preliminary evaluated for its functionality, detail accuracy and readability of textures at the German Rescue Robotics Center.
To perform a proof-of-principle dose-escalation study to radiosurgically induce scarring in cardiac muscle tissue to block veno-atrial electrical connections at the pulmonary vein antrum, similar to ...catheter ablation.
Nine mini-pigs underwent pretreatment magnetic resonance imaging (MRI) evaluation of heart function and electrophysiology assessment by catheter measurements in the right superior pulmonary vein (RSPV). Immediately after examination, radiosurgery with randomized single-fraction doses of 0 and 17.5-35 Gy in 2.5-Gy steps were delivered to the RSPV antrum (target volume 5-8 cm(3)). MRI and electrophysiology were repeated 6 months after therapy, followed by histopathologic examination.
Transmural scarring of cardiac muscle tissue was noted with doses ≥32.5 Gy. However, complete circumferential scarring of the RSPV was not achieved. Logistic regressions showed that extent and intensity of fibrosis significantly increased with dose. The 50% effective dose for intense fibrosis was 31.3 Gy (odds ratio 2.47/Gy, P<.01). Heart function was not affected, as verified by MRI and electrocardiogram evaluation. Adjacent critical structures were not damaged, as verified by pathology, demonstrating the short-term safety of small-volume cardiac radiosurgery with doses up to 35 Gy.
Radiosurgery with doses >32.5 Gy in the healthy pig heart can induce circumscribed scars at the RSPV antrum noninvasively, mimicking the effect of catheter ablation. In our study we established a significant dose-response relationship for cardiac radiosurgery. The long-term effects and toxicity of such high radiation doses need further investigation in the pursuit of cardiac radiosurgery for noninvasive treatment of atrial fibrillation.
4D ultrasound (4D US) is gaining relevance as a tracking method in radiation therapy (RT) with modern matrix array probes offering new possibilities for real-time target detection. However, for ...clinical implementation of USguided RT, image quality, volumetric framerate and artifacts caused by the probe’s presence during planning and / or setup computed tomography (CT) must be quantified. We compared three diagnostic 4D US systems with matrix array probes using a commercial wire phantom to measure spatial resolution as well as a calibration and a torso phantom to assess different image quality metrics. CT artifacts were quantified in the torso phantom by calculating the total variation and percentage of affected voxels between a reference CT scan and CT scans with probes in place. We found that state-of-the-art 4D US systems with small probes can fit inside the CT bore and cause fewer metal artifacts than larger probes. US image quality varies between systems and is task-dependent. Volume sizes and framerates are much higher than the commercial guidance solution for US-guided RT, warranting further investigation regarding clinical performance for image guidance.
To support surface registration in cranial radiation therapy by structural information. The risk for spatial ambiguities is minimized by using tissue thickness variations predicted from backscattered ...near-infrared (NIR) light from the forehead.
In a pilot study we recorded NIR surface scans by laser triangulation from 30 volunteers of different skin type. A ground truth for the soft-tissue thickness was segmented from MR scans. After initially matching the NIR scans to the MR reference, Gaussian processes were trained to predict tissue thicknesses from NIR backscatter. Moreover, motion starting from this initial registration was simulated by 5000 random transformations of the NIR scan away from the MR reference. Re-registration to the MR scan was compared with and without tissue thickness support.
By adding prior knowledge to the backscatter features, such as incident angle and neighborhood information in the scanning grid, we showed that tissue thickness can be predicted with mean errors of <0.2 mm, irrespective of the skin type. With this additional information, the average registration error improved from 3.4 mm to 0.48 mm by a factor of 7. Misalignments of more than 1 mm were almost thoroughly (98.9%) pushed below 1 mm.
For almost all cases tissue-enhanced matching achieved better results than purely spatial registration. Ambiguities can be minimized if the cutaneous structures do not agree. This valuable support for surface registration increases tracking robustness and avoids misalignment of tumor targets far from the registration site.
Robotic guided stereotactic radiosurgery has recently been investigated for the treatment of atrial fibrillation (AF). Before moving into human treatments, multiple implications for treatment ...planning given a potential target tracking approach have to be considered.
Theoretical AF radiosurgery treatment plans for twenty-four patients were generated for baseline comparison. Eighteen patients were investigated under ideal tracking conditions, twelve patients under regional dose rate (RDR = applied dose over a certain time window) optimized conditions (beam delivery sequence sorting according to regional beam targeting), four patients under ultrasound tracking conditions (beam block of the ultrasound probe) and four patients with temporary single fiducial tracking conditions (differential surrogate-to-target respiratory and cardiac motion).
With currently known guidelines on dose limitations of critical structures, treatment planning for AF radiosurgery with 25 Gy under ideal tracking conditions with a 3 mm safety margin may only be feasible in less than 40% of the patients due to the unfavorable esophagus and bronchial tree location relative to the left atrial antrum (target area). Beam delivery sequence sorting showed a large increase in RDR coverage (% of voxels having a larger dose rate for a given time window) of 10.8-92.4% (median, 38.0%) for a 40-50 min time window, which may be significant for non-malignant targets. For ultrasound tracking, blocking beams through the ultrasound probe was found to have no visible impact on plan quality given previous optimal ultrasound window estimation for the planning CT. For fiducial tracking in the right atrial septum, the differential motion may reduce target coverage by up to -24.9% which could be reduced to a median of -0.8% (maximum, -12.0%) by using 4D dose optimization. The cardiac motion was also found to have an impact on the dose distribution, at the anterior left atrial wall; however, the results need to be verified.
Robotic AF radiosurgery with 25 Gy may be feasible in a subgroup of patients under ideal tracking conditions. Ultrasound tracking was found to have the lowest impact on treatment planning and given its real-time imaging capability should be considered for AF robotic radiosurgery. Nevertheless, advanced treatment planning using RDR or 4D respiratory and cardiac dose optimization may be still advised despite using ideal tracking methods.
Transcranial alternating current stimulation (tACS) is an emerging non-invasive tool for modulating brain oscillations. There is evidence that weak oscillatory electrical stimulation during sleep can ...entrain cortical slow oscillations to improve the memory consolidation in rodents and humans. Using a novel method and a custom built stimulation device, automatic stimulation of slow oscillations in-phase with the endogenous activity in a real-time closed-loop setup is possible. Preliminary data from neuroplasticity experiments show a high detection performance of the proposed method, electrical measurements demonstrate the outstanding quality of the presented stimulation device.
Ultrasound is being increasingly investigated for real-time target localization in image-guided interventions. Yet,
validation remains challenging due to the difficulty to obtain a reliable ground ...truth. For this purpose, real-time volumetric (4D) ultrasound imaging was performed simultaneously with electromagnetic localization of three wireless transponders implanted in the liver of a radiotherapy patient. 4D ultrasound and electromagnetic tracking were acquired at framerates of 12Hz and 8Hz, respectively, during free breathing over 8 min following treatment. The electromagnetic antenna was placed directly above and the ultrasound probe on the right side of the patient to visualize the liver transponders. It was possible to record 25.7 s of overlapping ultrasound and electromagnetic position data of one transponder. Good spatial alignment with 0.6 mm 3D root-mean-square error between both traces was achieved using a rigid landmark transform. However, data acquisition was impaired since the electromagnetic tracking highly influenced the ultrasound equipment and vice versa. High intensity noise streaks appeared in the ultrasound scan lines irrespective of the chosen frequency (1.7-3.3 MHz, 2/4 MHz harmonic). To allow for target visualization and tracking in the ultrasound volumes despite the artefacts, an online filter was designed where corrupted pixels in the newest ultrasound frame were replaced with non-corrupted pixels from preceding frames. Aside from these artefacts, the recorded electromagnetic tracking data was fragmented and only the transponder closest to the antenna could be detected over a limited period of six consecutive breathing cycles. This problem was most likely caused by interference from the metal holder of the ultrasound probe and was solved in a subsequent experiment using a 3D-printed non-metal probe fixation. Real-time wireless electromagnetic tracking was compared with 4D ultrasound imaging
for the first time. For stable tracking, large metal components need to be avoided during data acquisition and ultrasound filtering is required.
Real-time target localization with ultrasound holds high potential for image guidance and motion compensation in radiosurgery due to its non-invasive image acquisition free from ionizing radiation. ...However, a two-step localization has to be performed when integrating ultrasound into the existing radiosurgery workflow. In addition to target localization inside the ultrasound volume, the probe itself has to be localized in order to transform the target position into treatment room coordinates. By adapting existing camera calibration tools, we have developed a method to extend the stereoscopic X-ray tracking system of a radiosurgery platform in order to locate objects such as marker geometries with six degrees of freedom. The calibration was performed with 0.1 mm reprojection error. By using the full area of the flat-panel detectors without pre-processing the extended software increased the tracking volume and resolution by up to 80%, substantially improving patient localization and marker detectability. Furthermore, marker-tracking showed sub-millimeter accuracy and rotational errors below 0.1°. This demonstrates that the developed extension framework can accurately localize marker geometries using an integrated X-ray system, establishing the link for the integration of real-time ultrasound image guidance into the existing system.
We present a novel framework for rigid point cloud registration. Our approach is based on the principles of mechanics and thermodynamics. We solve the registration problem by assuming point clouds as ...rigid bodies consisting of particles. Forces can be applied between both particle systems so that they attract or repel each other. These forces are used to cause rigid-body motion of one particle system toward the other, until both are aligned. The framework supports physics-based registration processes with arbitrary driving forces, depending on the desired behaviour. Additionally, the approach handles feature-enhanced point clouds, e.g., by colours or intensity values. Our framework is freely accessible for download. In contrast to already existing algorithms, our contribution is to precisely register high-resolution point clouds with nearly constant computational effort and without the need for pre-processing, sub-sampling or pre-alignment. At the same time, the quality is up to 28 percent higher than for state-of-the-art algorithms and up to 49 percent higher when considering feature-enhanced point clouds. Even in the presence of noise, our registration approach is one of the most robust, on par with state-of-the-art implementations.
Detecting cost-effectively and accurately the working area for autonomous lawn mowers is key for widespread automation of garden care. At present this is realized by means of perimeter wire, which ...leads to high setup and maintenance costs. Here, we propose an active low-cost sensor approach for detecting chlorophyll fluorescence response. Our novel and innovative sensing concept allows for a robust working area detection. The classification is thereby based on the averaging of multiple measurements using LED pulses and sensed fluorescence responses. By selecting only low-cost consumer components for the sensor design, we allow for high-volume production under low-cost aspects. We evaluated our novel sensor system by analyzing theoretically the signal path. Among other we investigated sampling frequencies, sensed surface areas and environmental influences. In real world experiments, we evaluated the performance of our sensor in an exemplary garden and on collected grass samples. Our theoretical and practical evaluations show that the sensor classification result is robust under different environmental conditions, such as changes in lawn quality.
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