Blood Vessel Phantom Research Articles

Inter-subject cerebrovascular variability: a source of uncertainty for dose calculation to circulating blood cells for glioblastoma patients treated with modern radiotherapy techniques

Purpose. To assess how inter-subject variations in brain vasculature among glioblastoma (GBM) patients affects the calculated dose received by circulating blood cells (CBC) during radiotherapy and its subsequent impact on CBC depletion. Methods. Ten GBM patients treated with either intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) were selected. For each patient, 23 cerebrovascular models were developed based on 23 healthy subject MR-angiography data to simulate intra- and inter-subject blood vessel diversity. Based on the corresponding treatment plan of the patient, the dose to CBC was calculated for all the 230 scenarios. The impact of inter-subject variation on fraction of irradiated blood volume (VD >0 cGy) and lymphocyte kill rates as a function of the clinical target volume (CTV) size and treatment technique were analyzed. Results. The dose fluctuation to CBC was higher in IMRT plans compared to VMAT plans. The uncertainty in the VD >0 cGy was 18.3% for IMRT and 2.0% (CI95%) for VMAT and the dispersion of the D 2% index was 6 cGy for IMRT and 1 cGy for VMAT (CI95%) for one single treatment fraction of 200 cGy. The uncertainty in killed CBC due to inter-subject diversity in brain blood vessel increased with increasing CTV size and was σ = 11.2%. Conclusions. VMAT showed greater robustness against inter-subject variation in blood vessels compared to IMRT. We recommend considering the uncertainty in depleting CBC resulting from the use of less patient-specific and generic blood vessel phantoms to improve the radiation-induced lymphopenia assessments.

Monitoring holograms for therapeutic ultrasound using passive cavitation beamforming

Acoustic holograms can generate cavitation patterns of complex spatial distribution by shaping and steering the focal spot of therapeutic ultrasound systems. However, when monitoring these systems by passive cavitation detection, off-axis therapeutical targets and the receiver directivity may not be aligned. In this paper, we present passive cavitation beamforming to monitor a therapeutical ultrasound system using holograms targeted to arbitrary locations, in which both therapeutic and passive cavitation monitoring systems use 3D-printed acoustic lenses. The therapeutic system uses an acoustic hologram to focus the ultrasound beam on the target, which is off-axis. Then, a second lens is designed to beamform the cavitation signals which emerge from the therapeutic target, steering the directivity of the passive cavitation detector in the direction of the therapeutic focus and, in addition, compensating for skull aberrations. The system is experimentally tested with an ex-vivo macaque skull and a blood vessel phantom with microbubbles. In addition, results are compared with a standard confocal configuration and an off-axis configuration in the absence of the monitor lens. A parametric study is performed by varying the amplitude of the emitted signal and the impact on the behaviour of the microbubbles is analysed based on the cavitation index values. Results show that monitoring holograms align the passive cavitation detector response with the focal spot of the targeted therapeutic transducer. These holograms encode a fixed beamformer for cavitation signals in reception, increasing the sensitivity of cavitation emission at the target. In this way, cavitation doses can be used to locally monitor the cavitation activity of microbubbles, thus opening a new path to low-cost monitoring of therapeutic ultrasound systems.

A Soft Biodegradable Chitosan‐Based Medical Microrobot with Optimized Structural Design and X‐Ray Visibility for Targeted Vessel Chemoembolization

AbstractAlthough many medical microrobots have been developed for treating diseases, their designs have not been optimized for disease environments and their functionality and capabilities have been primarily demonstrated in vitro. In addition, the imaging of microrobots within blood vessels in deep tissues remains a challenge. Herein, a chitosan‐based biodegradable microrobot with optimized structural design and X‐ray imaging for targeted vessel chemoembolization is reported. The design of the microrobot takes into account its magnetizability and stackability in blood vessels. The microrobot is prepared through laser micromachining of a porous chitosan sheet, attachment of nanoparticles, and filling the pores with gelatin. The optimized microrobot is biocompatible, biodegradable, thrombogenic, magnetically targetable, and drug‐loadable, as demonstrated both in vitro and in a blood vessel phantom. X‐ray imaging of the gold nanoparticle‐attached microrobots compares well with using commercial iodinated contrast materials, thereby demonstrating their real‐time long‐term X‐ray imaging capability. The in vivo real‐time imaging and targeted vessel embolization of the microrobot are demonstrated in rat liver. The proposed microrobot overcomes the limitations of embolic microbeads currently used in targeted vessel chemoembolization (i.e., targeted vessel blocking and X‐ray visibility) and expands the capability of microrobots in advanced platforms for treating human diseases.

Determination of the Flow Parameters of a Scattering Liquid in a Microfluidic Blood Vessel Phantom Based on Laser Speckle Contrast Imaging

Determination of the Flow Parameters of a Scattering Liquid in a Microfluidic Blood Vessel Phantom Based on Laser Speckle Contrast Imaging

Bubble cavitation generation near blood vessel walls using amplitude-modulated wave irradiation

We propose an amplitude-modulated pump ultrasound irradiation sequence to generate bubble cavitation for efficient sonoporation. By matching the envelope wavelength of the modulated wave to four times the vessel diameter, we aimed to improve the efficiency of bubble collapse near the vessel wall and extend the duration of collapse during repeated application of the sequence. Using an agarose-based blood vessel phantom, we compared the effects of the amplitude-modulated sequence with those of the normal sinusoidal sequence in which the sound pressure was adjusted so that the acoustic energy in one burst length of each sequence was equal. Compared with the normal irradiation sequence, the amplitude-modulated sequence yielded 2.45- and 1.31-fold greater bubble collapse near the vessel walls proximal and distal, respectively, to the pump ultrasound source, a 1.59-fold longer duration of bubble collapse, and a 1.69-fold larger area of micropores on the channel wall.

Closed‐Loop Control Characterization of Untethered Small‐Scale Helical Device in Physiological Fluid with Dynamic Flow Rates

Untethered small‐scale helical devices (USHDs) have the potential to navigate blood vessels and treat vascular occlusive diseases. However, there are still many challenges in translating this method into clinical practice, both in terms of localization and wireless motion control. Herein, closed‐loop control characterization of the USHD against and along physiological fluid inside a blood vessel phantom at different penetration depths is shown. First the dynamic flow and ultrasound images noise affecting the measurement are modeled, and control system of the USHD based on bifurcation analysis of a 1D hydrodynamic model is designed. Then a region of attraction of a USHD driven by a permanent magnet robotic (PMR) system inside a blood vessel phantom around an equilibrium point is constructed. Further, the point‐to‐point closed‐loop control strategy is implemented based on the magnetic point‐dipole approximation and kinematic control of the PMR system and ultrasound feedback inside physiological fluid, blood vessel, and soft tissue. The frequency response of the USHD is characterized against and along the flowing streams of fetal bovine serum within different flow rates in the 6–20 mm s−1range. The experimental results demonstrate the ability to navigate the USHD inside blood vessel phantoms with maximum position error of mm.

Deep learning methods hold promise for light fluence compensation in three-dimensional optoacoustic imaging.

.Significance: Quantitative optoacoustic imaging (QOAI) continues to be a challenge due to the influence of nonlinear optical fluence distribution, which distorts the optoacoustic image representation. Nonlinear optical fluence correction in OA imaging is highly ill-posed, leading to the inaccurate recovery of optical absorption maps. This work aims to recover the optical absorption maps using deep learning (DL) approach by correcting for the fluence effect.Aim: Different DL models were compared and investigated to enable optical absorption coefficient recovery at a particular wavelength in a nonhomogeneous foreground and background medium.Approach: Data-driven models were trained with two-dimensional (2D) Blood vessel and three-dimensional (3D) numerical breast phantom with highly heterogeneous/realistic structures to correct for the nonlinear optical fluence distribution. The trained DL models such as U-Net, Fully Dense (FD) U-Net, Y-Net, FD Y-Net, Deep residual U-Net (Deep ResU-Net), and generative adversarial network (GAN) were tested to evaluate the performance of optical absorption coefficient recovery (or fluence compensation) with in-silico and in-vivo datasets.Results: The results indicated that FD U-Net-based deconvolution improves by about 10% over reconstructed optoacoustic images in terms of peak-signal-to-noise ratio. Further, it was observed that DL models can indeed highlight deep-seated structures with higher contrast due to fluence compensation. Importantly, the DL models were found to be about 17 times faster than solving diffusion equation for fluence correction.Conclusions: The DL methods were able to compensate for nonlinear optical fluence distribution more effectively and improve the optoacoustic image quality.

Development of Stereo NIR-II Fluorescence Imaging System for 3D Tumor Vasculature in Small Animals.

Near-infrared-II (NIR-II, 1000–1700 nm) fluorescence imaging boasts high spatial resolution and deep tissue penetration due to low light scattering, reduced photon absorption, and low tissue autofluorescence. NIR-II biological imaging is applied mainly in the noninvasive visualization of blood vessels and tumors in deep tissue. In the study, a stereo NIR-II fluorescence imaging system was developed for acquiring three-dimension (3D) images on tumor vasculature in real-time, on top of the development of fluorescent semiconducting polymer dots (IR-TPE Pdots) with ultra-bright NIR-II fluorescence (1000–1400 nm) and high stability to perform long-term fluorescence imaging. The NIR-II imaging system only consists of one InGaAs camera and a moving stage to simulate left-eye view and right-eye view for the construction of 3D in-depth blood vessel images. The system was validated with blood vessel phantom of tumor-bearing mice and was applied successfully in obtaining 3D blood vessel images with 0.6 mm- and 5 mm-depth resolution and 0.15 mm spatial resolution. The NIR-II stereo vision provides precise 3D information on the tumor microenvironment and blood vessel path.

Deformation-Aware Robotic 3D Ultrasound

Tissue deformation in ultrasound (US) imaging leads to geometrical errors when measuring tissues due to the pressure exerted by probes. Such deformation has an even larger effect on 3D US volumes as the correct compounding is limited by the inconsistent location and geometry. This work proposes a patient-specified stiffness-based method to correct the tissue deformations in robotic 3D US acquisitions. To obtain the patient-specified model, robotic palpation is performed at sampling positions on the tissue. The contact force, US images and the probe poses of the palpation procedure are recorded. The contact force and the probe poses are used to estimate the nonlinear tissue stiffness. The images are fed to an optical flow algorithm to compute the pixel displacement. Then the pixel-wise tissue deformation under different forces is characterized by a coupled quadratic regression. To correct the deformation at unseen positions on the trajectory for building 3D volumes, an interpolation is performed based on the stiffness values computed at the sampling positions. With the stiffness and recorded force, the tissue displacement could be corrected. The method was validated on two blood vessel phantoms with different stiffness. The results demonstrate that the method can effectively correct the force-induced deformation and finally generate 3D tissue geometries

Investigation of the need for an x-ray scatter-reduction grid during neurointerventional procedures.

X-ray guided neurointerventions are catheter-based treatments for cerebrovascular diseases such as strokes and aneurysms. During such procedures visualization of treatment devices is the primary imaging task. In this work we investigate the necessity of x-ray scatter-reduction grids in performing those tasks. Various endovascular treatment devices such as stents, coils and catheters along with a low contrast blood vessel phantom were placed on a head-equivalent phantom. Images of the objects were acquired with and without a grid (15:1 grid ratio, 80 lines/cm and Al interspace). The x-ray field was set to the full 8 x 8 inch FOV to allow for realistic scatter generation. The detector was positioned close to the phantom to investigate maximal scatter conditions. Contrast and Contrast to Noise (CNR) ratios of the catheter tip and the blood vessel phantom were measured and compared for images obtained with and without the grid. The x-ray technique parameters were kept constant for all acquisitions. For the catheter tip there was a 43% reduction in contrast with the removal of the grid due to increased scatter reaching the detector. However, due to increased primary there was a 18% increase in CNR. For the blood vessel phantom, there was a 33% reduction in contrast, whereas a 17% increase in CNR. All the devices and the blood vessels in the phantom were still visible even with the increased scatter without the grid. The results of the study indicate the use of grids during neurointervention procedures might not be necessary to perform the intervention.

Dynamic blood flow phantom for in vivo liquid biopsy standardization

In vivo liquid biopsy, especially using the photoacoustic (PA) method, demonstrated high clinical potential for early diagnosis of deadly diseases such as cancer, infections, and cardiovascular disorders through the detection of rare circulating tumor cells (CTCs), bacteria, and clots in the blood background. However, little progress has been made in terms of standardization of these techniques, which is crucial to validate their high sensitivity, accuracy, and reproducibility. In the present study, we addressed this important demand by introducing a dynamic blood vessel phantom with flowing mimic normal and abnormal cells. The light transparent silica microspheres were used as white blood cells and platelets phantoms, while hollow polymeric capsules, filled with hemoglobin and melanin, reproduced red blood cells and melanoma CTCs, respectively. These phantoms were successfully used for calibration of the PA flow cytometry platform with high-speed signal processing. The results suggest that these dynamic cell flow phantoms with appropriate biochemical, optical, thermal, and acoustic properties can be promising for the establishment of standardization tool for calibration of PA, fluorescent, Raman, and other detection methods of in vivo flow cytometry and liquid biopsy.

Photoacoustic fluctuation imaging: theory and application to blood flow imaging

Photoacoustic fluctuation imaging, which exploits randomness in photoacoustic generation, provides enhanced images in terms of resolution and visibility, as compared to conventional photoacoustic images. While a few experimental demonstrations of photoacoustic fluctuation imaging have been reported, it has to date not been described theoretically. In the first part of this work, we propose a theory relevant to fluctuations induced either by random illumination patterns or by random distributions of absorbing particles. The theoretical predictions are validated by Monte Carlo finite-difference time-domain simulations of photoacoustic generation in random particle media. We provide a physical insight into why visibility artefacts are absent from second-order fluctuation images. In the second part, we demonstrate experimentally that harnessing randomness induced by the flow of red blood cells produce photoacoustic fluctuation images free of visibility artefacts. As a first proof of concept, we obtain two-dimensional images of blood vessel phantoms. Photoacoustic fluctuation imaging is finally applied in vivo to obtain 3D images of the vascularization in a chicken embryo.

Electroactive polymer-based inner vessel-wall pressure transducer capable of integration with a PTA balloon catheter for examining blood vessel health.

This study presents a state-of-the-art soft and biocompatible transducer capable of detecting vessel inner-wall pressure for biomedical applications. The device includes a 3D electroactive polymer core element encapsulated by polydimethylsiloxane with an ellipsoidal structure. The device produces a voltage output when its sensing mechanism experiences different pressures, resulting in deformation at different orientations. Thus, it can be employed to detect the pressure exerted by inner vessel walls of different stiffness values. The output voltage is induced by the strain experienced by the sensing mechanism of the device without the need for any external electrical power source. The core element, which is made of an ionic polymer-metal composite, possesses a unique hollow design; this allows a catheter to pass through, and the core element can be anchored at an arbitrary position on the catheter. We also demonstrate that the fabricated device can be integrated with a medically used percutaneous transluminal angioplasty balloon catheter to form a smart sensing module. This module can detect different levels of fat accumulation around the inner wall of a blood vessel phantom. Evaluating vessel blockage and stiffness using the signals acquired from the developed device is discussed.

АЛГОРИТМ ПОВЫШЕНИЯ ТКАНЕВОГО КОНТРАСТА ПРИ ВИЗУАЛИЗАЦИИ СТРУКТУРЫ СИЛЬНО РАССЕИВАЮЩИХ СРЕД МЕТОДОМ ОПТИЧЕСКОЙ КОГЕРЕНТНОЙ ТОМОГРАФИИ

A phantom of a human blood vessel is used to study the quality of structural images in endoscopic OCT. Small-angle raster scanning, averaging and multilevel filtering are used. Compression of the structural image with raster averaging increases the contrast of the structural image by reducing the level of speckle noise. File compression is part of the imaging process and is performed for each pixel. The graphical dependence of the upper lines of the A-scans of the structural image of the blood vessel phantom wall is presented. The proposed algorithm allows obtaining high-quality structural images for gastroenterology, urology, gynecology, and in vivo cardiovascular diagnostics using conventional and endoscopic OCT; characterized by high processing speed of initial data and optimal file size; reduces the requirements for the detector bandwidth of the endoscopic OCT system. For calculations, an HP Z640 Workstation with two six-core E5-2620v3c processors and a 4GB NVIDIA Quadro K4200 video card was used.

Image enhancement of photoacoustic imaging for early endometrial cancer detection by employing a filtered delay multiply and sum beamforming algorithm

In endometrial cancer, patients in early stages have a 91% 5-year survival chance. By contrast, patients in advanced stages have only 20% survival chance. Therefore, early diagnosis of endometrial cancer is very important. Photoacoustic imaging is able to distinguish benign from malignant tumors. However, the images acquired through photoacoustic imaging contain inherent artifacts, caused by imperfect reconstruction algorithms. In this paper, to improve the said images, a filtered delay-multiply-and-sum (F-DMAS) algorithm, which was proven to have an increased dynamic range and better quality of B-mode images was employed in the reconstruction process. First, the images of two blood vessel phantom experiments, acquired through photoacoustic imaging, were reconstructed by employing the F-DMAS algorithm. The results show the lateral resolutions of the system improving from 2.22 mm (with traditional photoacoustic imaging reconstruction algorithms) to 1.47 mm. Next, images of a pig uterus, filled with intralipid-20% emulsion, were also reconstructed by employing the F-DMAS algorithm. The average signal-to-noise ratio increased from 11.14 dB (with traditional photoacoustic imaging reconstruction algorithms) to 64.90 dB. In order to improve the continuity of the 3D PA image, F-DMAS with an adaptive coefficient was discussed to find the best balance between the signal-to-noise ratio and continuity. In conclusion, this paper demonstrates that the use of F-DMAS algorithms in the reconstruction of the images acquired through photoacoustic imaging in clinical investigations would improve the detection rate of early endometrial cancer.

Development of a dynamic blood vessel phantom for evaluation of moving images.

In coronary angiography (CAG) and percutaneous coronary intervention (PCI), it is important for radiological technologists to optimize the balance between radiation dose and image quality for physicians to be able to perform CAG and PCI most effectively. Evaluation of image processing is necessary to ensure that technologists can optimally adjust image quality for clinical use to the extent that physicians require. However, few phantoms are available for evaluating fluoroscopic image processing, and this makes it necessary to adjust image quality in clinical settings while utilizing the image processing according to the manufacturer’s recommendations. In this study, we developed a dynamic phantom that mimics a pulsating coronary artery for use in image quality analysis of moving images. We also examined whether processed images (image lag) can be physically analyzed. Two issues require special attention in creating a new phantom: establishing the exact position of the simulated blood vessel in the phantom, and providing good reproducibility. The study used the rotational motion of a disk to generate images, with a circular simulated blood vessel on the rotating acrylic disk, with the center of the simulated blood vessel shifted from the center of the acrylic disk. This enabled the reproduction of translational motion of the simulated blood vessel. As a result, because this phantom has signals and afterimages at the same position (of a simulated blood vessel), a quantitative evaluation of the afterimages became possible. In the evaluation of the image processing with the angiograph, it was shown that evaluations of image lag which are typically performed in clinical settings can be performed with the dynamic blood vessel phantom.

Widefield illumination photoacoustic imaging of blood vessel phantom

AbstractWe achieved photoacoustic tomographic imaging by employing widefield illumination using a pulsed laser source that irradiates the entire area of interest for the specimen under investigation. This approach can be simpler and more efficient than the use of narrow point‐source scanning. Tomographic images were computed via an inverse‐reconstruction‐based algorithm from signals acquired using a single transducer with circular scanning configuration. The signals were coupled to the transducer probe with index‐matching gel around the circumference of the specimen, eliminating the need for aquatic immersion. A blood‐vessel‐mimicking phantom was used to demonstrate our setup and the image reconstruction was also verified by simulation, proving the feasibility of a miniaturized system based on this design.

A Novel Tip-positioning Control of a Magnetically Steerable Guidewire in Sharply Curved Blood Vessel for Percutaneous Coronary Intervention

This paper suggests a novel method for the positioning control of a magnetically steerable guidewire without needing to detect a tip angle, which can pass through sharply curved blood vessels with potentially reduced contact between the guidewire end tip and the blood vessel for Percutaneous Coronary Intervention (PCI). The proposed tip-positioning control consists of four parts: 1) Path-regeneration, 2) Feeding control, 3) EMA (Electromagnetic Actuator) control, and 4) Vision tracking. Path-regeneration provides an improved path based on the properties of the guidewire and the size of the blood vessel when the guidewire cannot follow the pre-planned path. Based on the desired path, the feeding control drives the translational motion of the guidewire while the EMA system steers the guidewire’s end tip, which is made of a permanent magnet. A pair of Helmholtz coils is employed for the EMA system, and a vision-tracking algorithm is used to detect the position of the magnet tip in real time. The system was integrated for the preliminary study, and the magnet tip could be controlled so as to track a desired path without any shape or curvature information, which requires the use of an additional catheter model or angle estimation algorithm. The proposed catheter tip position control method was verified by experiments on both smooth and sharply curved blood vessel phantoms. The results showed that the proposed method could accomplish the tip position control of the guidewire with high accuracy in real time.

Real-time co-registered photoacoustic and ultrasonic imaging for early endometrial cancer detection driven by cylindrical diffuser

In illuminating tissues, a cylindrical diffuser (CD) has an advantage over regular laser sources due to its ability to illuminate a larger volume of the target tissue. This paper presents a co-registered large volume photoacoustic (PA) and ultrasonic (US) imaging for early endometrial cancer (EEC) detection using CD. It has the advantage that the US imaging system is outside the body and only the PA excitation device is inside the body, which makes the system more efficient and less invasive for EEC detection. The paper reports on two sets of experiments. The first set produced real-time PA images of blood vessel phantom. The second set demonstrated the imaging of pig uterus ex vivo. The results show that the system has the potential for imaging and characterizing of EEC.

Ultrasound Modulated Droplet Lasers

We demonstrated the ultrasound modulated droplet lasers, in which the laser intensity from whispering gallery mode (WGM) of oil droplets can be reversibly enhanced up to 20-fold when the ultrasound pressure is beyond a certain threshold. The lasing enhancement was investigated with various ultrasound frequencies and pressures. Furthermore, the ultrasound modulation of the laser output was achieved by controlling the ultrasound pressure, the duty cycle, and the frequency of ultrasound bursts. Its potential application was explored via the study on a human whole blood vessel phantom. A theoretical analysis was also conducted, showing that the laser emission enhancement results from the directional emission from a deformed cavity under ultrasound pressure. Our studies reveal the unique capabilities of ultrasound modulated droplet lasers, which could lead to the development of laser emission-based microscopy for deep tissue imaging with high spatial resolution and detection sensitivity that may overcome the l...