Resolution For Real-time Imaging Research Articles

A Untethered Magnetic Micro-Robot for Local Therapeutic Delivery for Neurosurgical Oncology

INTRODUCTION: Microrobots designed for biomedical applications have garnered significant research interest, offering advantages in drug delivery, microsurgery, and biopsies. Magnetic fields enabled by electromagnetic coils permit untethered nonlinear movement of these tiny robots within the brain on the surface, the cerebrospinal fluid, and parenchyma. Microdrillers (either individually or in swarms) are a promising tool for microsurgery, capable of drilling through viscoelastic media (brain tissue). However, challenges remain in scaling down the robot size and exploring diverse applications. METHODS: Parallelizable (batch) microfabrication involved 3D printing via two-photon lithography. The pH-sensitive hydrogel was synthesized through UV-initiated radical polymerization mixed with a tracer (fluorescein sodium salt). Imaging via photon-counting CT was performed for microbot tracking in preclinical models including hydrogel phantoms, large animal cadaveric fresh brain tissue, and human cadaveric tissue. RESULTS: Microbot speeds in various tissues were characterized with speeds up to 800 um/sec over magnetic field amplitudes of 5 to 55 mT while performing complex nonlinear trajectories via open-loop surgeon control via surgeon. Targeted hydrogel delivery of fluorescein label/nanoparticle drug over a pH range of 6.2 (tumor tissue) and 7.8 (normal tissue) over a time interval of 50 s is demonstrated as proof of concept with a rate of 2.4 times faster in acidic conditions. Lastly, we show state-of-the-art micromillmetric resolution for real time imaging via photon-counting spectral CT for implementation of closed loop control. CONCLUSIONS: A novel minimally invasive microrobotic platform technology capable of targeted local drug delivery in brain parenchyma is demonstrated.

On the Use of Ultrasound-Based Technology for Cargo Inspection

A new guided wave imaging application for fast, low-cost ultrasound-based cargo scanning system is proposed. The ultimate goal is the detection of high-atomic-number, shielding containers used to diminish the radiological signature of nuclear threats. This ultrasonic technology has the potential to complement currently deployed X-ray-based radiographic systems, thus enhancing the probability of detecting nuclear threats. An array of ultrasonic transceivers can be attached to the metallic structure of the cargo to create a guided Lamb wave. Guided medium thickness and composition variation creates reflections whose placement can be revealed by means of an imaging algorithm. The knowledge of the reflection position provides information about the shielding metallic container location inside the cargo. Moreover, due to the low coupling between metallic and nonmetallic surfaces, only the footprint of metallic containers shows up in the imaging results, thus avoiding false positives from plastic or wooden assets. As imaging capabilities are degraded if working with dispersive Lamb wave modes, the operating frequency is tuned to provide a tradeoff between low dispersion and real-time image resolution. Reflected waves in the guided domain bounds may limit the performance of imaging methods for guided media. This contribution proposes a solution based on real-time Fourier domain analysis, where plane wave components can be filtered out, thus removing nondesired contributions from bounds. Several realistic examples, scaled due to limited calculation capabilities of the available computational resources, are presented in this work, showing the feasibility of the proposed method.

Quantification of left ventricular ejection fraction using through-time radial GRAPPA for real-time imaging

Background Cardiac MRI requires a steady cardiac rhythm for ECGgating, and multiple breath-holds to minimize respiratory artifacts. By employing a non-Cartesian parallel imaging in form of through-time radial GRAPPA [1], accelerated imaging can be performed with temporal resolutions of < 50 ms, obviating the need for gating or breath-holding. breath-holding. We tested the hypothesis that volumetric measurements in the LV obtained with the real-time method could replace traditional measurements. Methods A total of 31 subjects (23 patients, 8 volunteers) were scanned on a 1.5T Avanto or 1.5T Espree scanner (Siemens Medical Solutions, Erlangen, Germany) using a combined spine and abdominal receiver array with 12 to 15 channels. The gold-standard cardiac functional examination was performed in a short-axis orientation with ECG gating, requiring 12-16 breathholds with the following parameters: Cartesian bSSFP sequence, TR~3162 ms, in plane resolution = 1.4-2.6 mm 2 , slice thickness = 6-8 mm, cardiac phases = 18-30. The real-time scans (26 calibration frames per slice and accelerated acquisition) were performed immediately following the goldstandard scan with no ECG gating or breath-holding: radial bSSFP sequence, TR= 2.64 ms, resolution = 2.3 mm 2 , slice thickness = 6-8 mm. A data acceleration factor of R=8 (16 projections for 128 x 128 matrix) was used such that the temporal resolution for real-time imaging was 42.2 ms per image. Calibration data for non-Cartesian GRAPPA reconstruction was acquired without ECG gating or breath-holds. After data collection and reconstruction, the blood volume in the left ventricle was assessed to determine the ESV, EDV, and EF for both methods. Results Bland-Altman analysis [2] was used to analyze the agreement between the two methods. This showed that 30 of the 31 of the EF measurements using traditional breath-hold imaging and the real-time free breathing method were within the 95% limits of agreement. The mean difference in LVEF between the two methods was -2% (breath-hold minus real-time). All 31 measurements of EDV using both methods were within 95% limits of agreement. The mean difference in EDV between the two methods was -4ml. 30/ 31 measurements of ESV using both methods were within the 95% limits of agreement. The mean difference in ESV between the two methods was 2 ml. The differences in EF, EDV, and ESV are not clinically significant [3]. Conclusions Our results show no significant statistical or clinical difference between volumetric analysis determined using standard breathhold cine imaging and through-time radial GRAPPA. This indicates that standard method can be replaced by the real-time imaging approach which can be used even for patients with arrhythmia or difficulty with breath-holding. Funding

固体撮像とその関連技術 動画像圧縮イメージセンサ

In this paper, we propose a novel image sensor by which the image signal can be compressed. Since the image signal is compressed on the imager plane by making use of the parallel nature of image signals, the amount of signal readout from the imager can be significantly reduced. Thus, the proposed sensor can potentially be applied to high-pixel-rate cameras and real-time processing systems which require very high-speed imaging and very high resolution for real-time imaging; the very high bandwidth is the fundamental limitation to the feasibility of such high-pixel-rate sensors and processing systems. The proposed sensor utilizes a conditional replenishment algorithm; it detects temporally changing pixels as active pixels and output them. An analog circuit for processing in each pixel and an entire sensor architecture have been designed. A first prototype of a VLSI sensor chip has been fabricated. Results of experiments using the prototype chip are shown.