Image-guided System Research Articles

Multimodal 3D ultrasound and CT in image-guided spinal surgery: public database and new registration algorithms.

Accurate multimodal registration of intraoperative ultrasound (US) and preoperative computed tomography (CT) is a challenging problem. Construction of public datasets of US and CT images can accelerate the development of such image registration techniques. This can help ensure the accuracy and safety of spinal surgeries using image-guided surgery systems where an image registration is employed. In addition, we present two algorithms to register US and CT images. We present three different datasets of vertebrae with corresponding CT, US, and simulated US images. For each of the two latter datasets, we also provide 16 landmark pairs of matching structures between the CT and US images and performed fiducial registration to acquire a silver standard for assessing image registration. Besides, we proposed two patch-based rigid image registration algorithms, one based on normalized cross-correlation (NCC) and the other based on correlation ratio (CR) to register misaligned CT and US images. The CT and corresponding US images of the proposed database were pre-processed and misaligned with different error intervals, resulting in 6000 registration problems solved using both NCC and CR methods. Our results show that the methods were successful in aligning the pre-processed CT and US images by decreasing the warping index. The database provides a resource for evaluating image registration techniques. The simulated data have two applications. First, they provide the gold standard ground-truth which is difficult to obtain with ex vivo and in vivo data for validating US-CT registration methods. Second, the simulated US images can be used to validate real-time US simulation methods. Besides, the proposed image registration techniques can be useful for developing methods in clinical application.

Thermal Ablation and High-Resolution Imaging Using a Back-to-Back (BTB) Dual-Mode Ultrasonic Transducer: In Vivo Results.

We present a back-to-back (BTB) structured, dual-mode ultrasonic device that incorporates a single-element 5.3 MHz transducer for high-intensity focused ultrasound (HIFU) treatment and a single-element 20.0 MHz transducer for high-resolution ultrasound imaging. Ultrasound image-guided surgical systems have been developed for lesion monitoring to ensure that ultrasonic treatment is correctly administered at the right locations. In this study, we developed a dual-element transducer composed of two elements that share the same housing but work independently with a BTB structure, enabling a mode change between therapy and imaging via 180-degree mechanical rotation. The optic fibers were embedded in the HIFU focal region of ex vivo chicken breasts and the temperature change was measured. Images were obtained in vivo mice before and after treatment and compared to identify the treated region. We successfully acquired B-mode and C-scan images that display the hyperechoic region indicating coagulation necrosis in the HIFU-treated volume up to a depth of 10 mm. The compact BTB dual-mode ultrasonic transducer may be used for subcutaneous thermal ablation and monitoring, minimally invasive surgery, and other clinical applications, all with ultrasound only.

A Review of Minimally Invasive Techniques in Thoracolumbar Trauma

AbstractThe development of endoscopy, microscopy, and image guidance system provided the impetus for the adoption of minimally invasive surgery (MIS) techniques in the management of spinal trauma patients. The underlying drive has been an attempt to achieve the functional and biomechanical goals inherent to trauma care but through MIS techniques. Broadly the MIS techniques for spinal trauma can be divided into two categories—fusion and nonfusion methods. Fusion methods include mini-open or keyhole approaches that allow for discectomy and/or corpectomy and cage reconstruction via an anterior/lateral/posterior operative corridor. The nonfusion methods primarily include percutaneous pedicle screw fixation, kyphoplasty, and vertebroplasty, all without placement of bone graft or other attempts at inducing arthrodesis. In this review article, we have stratified the MIS techniques based on the operative corridor used and briefly described the decision-making process, technical nuances, pros, and cons of each technique.

Quality Assurance in Modern Gynecological HDR-Brachytherapy (Interventional Radiotherapy): Clinical Considerations and Comments.

Simple SummaryThis is a focused review discussing quality assurance during interventional brachytherapy in gynecological cancers. This topic is very large and is usually addressed from the technical and physical sides, therefore, we decided to select “hot-spots” under this large title and discuss them from the point of view of clinicians. We hope that this concise and focused review will help clinicians in improving their quality assurance protocols and draw attention to the discussed issues.The use of brachytherapy (interventional radiotherapy) in the treatment of gynecological cancers is a crucial element in both definitive and adjuvant settings. The recent developments in high-dose rate remote afterloaders, modern applicators, treatment-planning software, image guidance, and dose monitoring systems have led to improvement in the local control rates and in some cases improved the survival rates. The development of these highly advanced and complicated treatment modalities has been accompanied by challenges, which have made the existence of quality assurance protocols a must to ensure the integrity of the treatment process. Quality assurance aims at standardizing the technical and clinical procedures involved in the treatment of patients, which could eventually decrease the source of uncertainties whether technical (source/equipment related) or clinical. This commentary review sheds light (from a clinical point of view) on some potential sources of uncertainties associated with the use of modern brachytherapy in the treatment of gynecological cancers.

Concept description and accuracy evaluation of a moldable surgical targeting system

.Purpose: We explain our concept for customization of a guidance instrument, present a prototype, and describe a set of experiments to evaluate its positioning and drilling accuracy.Methods: Our concept is characterized by the use of bone cement, which enables fixation of a specific configuration for each individual surgical template. This well-established medical product was selected to ensure future intraoperative fabrication of the template under sterile conditions. For customization, a manually operated alignment device is proposed that temporary defines the planned trajectory until the bone cement is hardened. Experiments () with half-skull phantoms were performed. Analysis of accuracy comprises targeting validations and experiments including drilling in bone substitutes.Results: The resulting mean positioning error was found to be at the level of the target point whereas drilling was possible with a mean accuracy of .Conclusion: We proposed a cost-effective, easy-to-use approach for accurate instrument guidance that enables template fabrication under sterile conditions. The utilization of bone cement was proven to fulfill the demands of an easy, quick, and prospectively intraoperatively doable customization. We could demonstrate sufficient accuracy for many surgical applications, e.g., in neurosurgery. The system in this early development stage already outperforms conventional stereotactic frames and image-guided surgery systems in terms of targeting accuracy.

Adaptive Physics-Based Non-Rigid Registration for Immersive Image-Guided Neuronavigation Systems.

Objective: In image-guided neurosurgery, co-registered preoperative anatomical, functional, and diffusion tensor imaging can be used to facilitate a safe resection of brain tumors in eloquent areas of the brain. However, the brain deforms during surgery, particularly in the presence of tumor resection. Non-Rigid Registration (NRR) of the preoperative image data can be used to create a registered image that captures the deformation in the intraoperative image while maintaining the quality of the preoperative image. Using clinical data, this paper reports the results of a comparison of the accuracy and performance among several non-rigid registration methods for handling brain deformation. A new adaptive method that automatically removes mesh elements in the area of the resected tumor, thereby handling deformation in the presence of resection is presented. To improve the user experience, we also present a new way of using mixed reality with ultrasound, MRI, and CT.Materials and methods: This study focuses on 30 glioma surgeries performed at two different hospitals, many of which involved the resection of significant tumor volumes. An Adaptive Physics-Based Non-Rigid Registration method (A-PBNRR) registers preoperative and intraoperative MRI for each patient. The results are compared with three other readily available registration methods: a rigid registration implemented in 3D Slicer v4.4.0; a B-Spline non-rigid registration implemented in 3D Slicer v4.4.0; and PBNRR implemented in ITKv4.7.0, upon which A-PBNRR was based. Three measures were employed to facilitate a comprehensive evaluation of the registration accuracy: (i) visual assessment, (ii) a Hausdorff Distance-based metric, and (iii) a landmark-based approach using anatomical points identified by a neurosurgeon.Results: The A-PBNRR using multi-tissue mesh adaptation improved the accuracy of deformable registration by more than five times compared to rigid and traditional physics based non-rigid registration, and four times compared to B-Spline interpolation methods which are part of ITK and 3D Slicer. Performance analysis showed that A-PBNRR could be applied, on average, in <2 min, achieving desirable speed for use in a clinical setting.Conclusions: The A-PBNRR method performed significantly better than other readily available registration methods at modeling deformation in the presence of resection. Both the registration accuracy and performance proved sufficient to be of clinical value in the operating room. A-PBNRR, coupled with the mixed reality system, presents a powerful and affordable solution compared to current neuronavigation systems.

Automatic deep learning-driven label-free image-guided patch clamp system

Patch clamp recording of neurons is a labor-intensive and time-consuming procedure. Here, we demonstrate a tool that fully automatically performs electrophysiological recordings in label-free tissue slices. The automation covers the detection of cells in label-free images, calibration of the micropipette movement, approach to the cell with the pipette, formation of the whole-cell configuration, and recording. The cell detection is based on deep learning. The model is trained on a new image database of neurons in unlabeled brain tissue slices. The pipette tip detection and approaching phase use image analysis techniques for precise movements. High-quality measurements are performed on hundreds of human and rodent neurons. We also demonstrate that further molecular and anatomical analysis can be performed on the recorded cells. The software has a diary module that automatically logs patch clamp events. Our tool can multiply the number of daily measurements to help brain research.

Development of a compact X-band linear accelerator system mounted on an O-arm rotating gantry for radiation therapy.

A compact X-band linear accelerator (LINAC) system equipped with a small and lightweight magnetron was constructed to develop a high-precision image-guided radiotherapy system. The developed LINAC system was installed in an O-ring gantry where cone-beam computed tomography (CBCT) was embedded. When the O-arm gantry is rotated, an x-ray beam is stably generated, which resulted from the stable transmission of radio frequency power into the X-band LINAC system. Quality assurance (QA) tests, including mechanical and dosimetry checks, were carried out to ensure safety and operation performance according to the American Association of Physicists in Medicine's TG-51, 142, an international standard protocol established by accredited institutions. In addition, delivery QA of the radiotherapy planning system was conducted to verify intensity-modulated radiotherapy techniques. Therefore, it was demonstrated that the developed X-band LINAC system mounted on the O-arm gantry proved to be valid and reliable for potential use in CBCT image-guided radiation therapy.

How I do it: ultrasound-guided placement of ommaya reservoir in a patient with small ventricles and cavum septum pellucidum.

Intraventricular chemotherapy via Ommaya reservoir is an important part of the treatment in patients with malignant central nervous system tumors. In these patients, catheter placement can be challenging due to the normal-sized ventricles. Intraoperative ultrasound guidance was used for Ommaya reservoir placement in a 56-year-old patient with multiple intracranial and leptomeningeal metastases who had cavum septum pellucidum et vergae malformation. The catheter was successfully placed into the frontal horn of the lateral ventricle outside the cavum. Intraoperative ultrasound is a suitable image guidance system in patients with slit-like or normal-sized ventricles. It can also be used in patients with ventricular malformations.

Comparison of two fluorescent probes in preclinical non-invasive imaging and image-guided debridement surgery of Staphylococcal biofilm implant infections

Implant-associated infections are challenging to diagnose and treat. Fluorescent probes have been heralded as a technologic advancement that can improve our ability to non-invasively identify infecting organisms, as well as guide the inexact procedure of surgical debridement. This study’s purpose was to compare two fluorescent probes for their ability to localize Staphylococcus aureus biofilm infections on spinal implants utilizing noninvasive optical imaging, then assessing the broader applicability of the more successful probe in other infection animal models. This was followed by real-time, fluorescence image-guided surgery to facilitate debridement of infected tissue. The two probe candidates, a labelled antibiotic that targets peptidoglycan (Vanco-800CW), and the other, a labelled antibody targeting the immunodominant Staphylococcal antigen A (1D9-680), were injected into mice with spine implant infections. Mice were then imaged noninvasively with near infrared fluorescent imaging at wavelengths corresponding to the two probe candidates. Both probes localized to the infection, with the 1D9-680 probe showing greater fidelity over time. The 1D9-680 probe was then tested in mouse models of shoulder implant and allograft infection, demonstrating its broader applicability. Finally, an image-guided surgery system which superimposes fluorescent signals over analog, real-time, tissue images was employed to facilitate debridement of fluorescent-labelled bacteria.

Image-guided EBUS bronchoscopy system for lung-cancer staging.

The staging of the central-chest lymph nodes is a major step in the management of lung-cancer patients. For this purpose, the physician uses a device that integrates videobronchoscopy and an endobronchial ultrasound (EBUS) probe. To biopsy a lymph node, the physician first uses videobronchoscopy to navigate through the airways and then invokes EBUS to localize and biopsy the node. Unfortunately, this process proves difficult for many physicians, with the choice of biopsy site found by trial and error. We present a complete image-guided EBUS bronchoscopy system tailored to lymph-node staging. The system accepts a patient’s 3D chest CT scan, an optional PET scan, and the EBUS bronchoscope’s video sources as inputs. System workflow follows two phases: (1) procedure planning and (2) image-guided EBUS bronchoscopy. Procedure planning derives airway guidance routes that facilitate optimal EBUS scanning and nodal biopsy. During the live procedure, the system’s graphical display suggests a series of device maneuvers to perform and provides multimodal visual cues for locating suitable biopsy sites. To this end, the system exploits data fusion to drive a multimodal virtual bronchoscope and other visualization tools that lead the physician through the process of device navigation and localization. A retrospective lung-cancer patient study and follow-on prospective patient study, performed within the standard clinical workflow, demonstrate the system’s feasibility and functionality. For the prospective study, 60/60 selected lymph nodes (100%) were correctly localized using the system, and 30/33 biopsied nodes (91%) gave adequate tissue samples. Also, the mean procedure time including all user interactions was 6 min 43 s All of these measures improve upon benchmarks reported for other state-of-the-art systems and current practice. Overall, the system enabled safe, efficient EBUS-based localization and biopsy of lymph nodes.

Image-Guidance for Non-Anatomical Liver Resections: An ex-vivo Study

Introduction: Non-anatomical resections of liver tumors are becoming more popular because they spare a larger portion of healthy liver parenchyma. However, the lack of anatomical landmarks to follow during the resection process makes them technically more challenging than anatomical resections. Image-guidance systems have been introduced to provide additional guidance, but are rarely used due to their inaccuracy, time-effort and complexity in usage and setup. Therefore, we have designed a new navigation approach that renders a surgical plan intra-operatively in real time using only navigated ultrasound. Method: The ultrasound based navigation approach comprises the following steps:i)scanning the surface using the navigated ultrasound,ii)marking the tumor location and size on a midsection ultrasound image,iii)specifying a resection shape and a safety margin to create an optimal surgical plan. In this study, we evaluated this method in an ex-vivo porcine model by three experienced hepatobiliary surgeons with respect to R0 resection status. Results: In 22 out of 23 resections an R0 resection (margin > 1mm) was achieved (95.7%) with a median resection margin of 5.9 mm (IQR 3.5 - 7.7 mm). There was a difference between the surgeons in terms of resection margin with operators 1,2 and 3 having 7.8 mm, 4.15 mm and 5.1 mm median resection margin respectively (p = 0.054). Conclusions: This navigation approach could represent a useful tool for intra-operative guidance in non-anatomical resection alongside conventional ultrasound guidance. A clinical pilot trial with 10 patients is currently in planning and will start beginning of 2020.

A real time image-guided reposition system for the loosed bone graft in orthognathic surgery

In traditional orthognathic surgery, the dental splint technique is typically used to assist surgeons to reposition the maxilla or mandible. However, the design and manufacturing of dental splints is time-consuming and labor-intensive, and the templates may not applicable for some complicated cases due to the anatomic intricacies in the maxillofacial region. During recent years, computer-aided navigation technology has been widely used in oral and maxillofacial surgery. However, due to the limitation of current calibration and registration methods, it has been rarely reported for the motion tracking of intraoperative reposition for the loosed bone graft. In this study, a novel surgical navigation system was developed. With the use of this system, not only the surgical saw can be tracked in real-time, but also the loosed bone graft can be navigated under the guidance of the interactive 2D and 3D views until it is aligned with the preoperatively planned position. The phantom experiments validated the feasibility of our surgical navigation system, and the mean error of image-guided reposition was 1.03 ± 0.10 mm, which was significantly more accurate than the mean error of 5.57 ± 1.40 mm based on the non-navigated methods.

SabreSource™: a novel percutaneous nephrolithotomy apparatus to aid collecting system puncture - a preliminary report

Successful percutaneous nephrolithotomy (PCNL) relies on a technically challenging, precise needle puncture of the renal collecting system. We aimed to compare, in an ex vivo model, the use of a real time image guidance system (the SabreSource™) and a mechanical stabilising device with conventional manual techniques for the accuracy of needle placement. The SabreSource™ system (Minrad International Inc.; New York, USA) is a real time image guidance system. The system platform is mounted on a C-arm fluoroscope. It employs targeting cross hairs on the fluoroscopic image that can be easily positioned to target the desired renal calyx. The system directs a visible laser beam onto the patient which is precisely aligned with the cross hairs on the fluoroscopic image. This provides the correct "bull's-eye" angle of approach to the calyx, even after the x-ray source is turned off. The locator then stabilises the needle in the "bull's-eye" position so that only screening for depth is required. Objective assessment using a simulated PCNL puncture was performed by 7 urologic trainees on a kidney phantom with and without using the SabreSource™. Fluoroscopy screening time (FST) and amount of radiation (mGy) used to achieve successful puncture were compared. Simulated PCNL puncture was quicker and resulted in reduced radiation exposure when the apparatus was used. The mean FST for traditional "bull's-eye" vs SabreSource™ puncture was 17 vs 5 seconds (p = 0.01), and the mean radiation exposure to puncture was 0.7 vs 0.2 mGy (p = 0.03), respectively. The SabreSource™ is a novel assistant to achieving successful PCNL puncture. In combination with "the locator" the preliminary in vitro testing suggests that the device reduces fluoroscopy exposure and is quicker. The device warrants further evaluation in the clinical setting.

Study on intelligent counter-countermeasures of infrared imaging air-to-air missiles

After four generations of development, the infrared air-to-air missile has developed from the attack mode of trailing pursuit to a high-performance tactical weapon with omnidirectional attack, over-the-shoulder launch and interception after launch, and its guidance system has also gone through the development process from unit, multiple to IIR at present. On account of the infrared imaging air-to-air missile anti-jamming problems, the composition of imaging guidance system, the principle of the angle tracking of the target in the imaging stage was introduced firstly, and the relevant anti-jamming methods that usually used at this time. Second, on the analysis of the application of intelligence technology requirement for air-to-air missiles in the course of actual combat, current complex air combat environment composition and infrared imaging counter-countermeasures against natural background as well as artificial interference sources, six anti-jamming methods, each dealing with a specific interference problem, were proposed from intelligent perception and guidance, intelligent guidance and control and intelligent cooperation, and the brief introduction was carried on. Some part of the simulation results show that above methods can achieve good effects on their respective anti-jamming problems.

Comparison of Setup Variations and Defining a CTV-PTV Margin in Fractionated Radiotherapy of Brain Tumor Using Novalis Tx Orthogonal OBI (kv) Versus Brain Lab ExacTrac (kv) Imaging Systems with Brain Lab Mask

The objective of this study is to evaluate the setup discrepancy between Brain Lab ExacTrac (kv) and Orthogonal Novalis Tx (kv) imaging systems and to obtain an optimal CTV-PTV margin. We recruited 35 consecutive brain tumor patients, immobilized with non-invasive thermoplastic BrainLab mask, between August 2016 and August 2017. The position verification done by ExacTrac, Infrared Positioning System was followed by a set of images by OBI at 0° and 90° position. The images were autofused and compared with DRR generated by TPS. The extent of translational and rotational shift was then applied and documented. The translational inter-fractional setup error (mean ± SD) in X-axis detected by OBI and ET was 0.002 ± 0.227 and −0.042 ± 0.084, respectively. In Y-axis, the error detected was −0.01 ± 0.176 and 0.075 ± 0.079, respectively, whereas in Z-axis the error with OBI and ET was 0.329 ± 0.521 and 0.051 ± 0.091, respectively. The P-value of inter-fractional errors in X, Y, and Z axes was 0.294, 0.013, and 0.004, which is statistically significant in Y- and Z-axes. Rotational inter-fractional setup errors (mean ± SD) for OBI and ET were −0.101 ± 0.257 and −0.076 ± 0.102, respectively. The rotational setup errors detected by ET in pitch and roll dimension are −0.003 ± 0.084 and −0.085 ± 0.073, respectively. The data obtained were put in Van Herk’s formula (PTV margin = 2.5 ∑ + 0.74 σ), and CTV-PTV margin was calculated. CTV-PTV margin for ET was 2.70, 2.72, and 2.94 mm and 3.38o, 2.84o, and 2.51o in lateral, longitudinal, vertical and pitch, roll, yaw dimension, respectively. The CTV-PTV margin for OBI was 7.40, 6.20, and 5.30 mm and 7.27o in lateral, longitudinal, vertical, and yaw dimension, respectively. Daily setup verifications that use the Brain LAB Exac Trac 6D image-guided system are very useful for brain tumor treatment; nevertheless, OBI kv imaging can be used for FRT of brain tumor with extended margin.

Automated Retinal Vein Cannulation on Silicone Phantoms Using Optical-Coherence-Tomography-Guided Robotic Manipulations.

Retinal vein occlusion is one of the most common causes of vision loss, occurring when a blood clot or other obstruction occludes a retinal vein. A potential remedy for retinal vein occlusion is retinal vein cannulation, a surgical procedure that involves infusing the occluded vein with a fibrinolytic drug to restore blood flow through the vascular lumen. This work presents an image-guided robotic system capable of performing automated cannulation on silicone retinal vein phantoms. The system is integrated with an optical coherence tomography probe and camera to provide visual feedback to guide the robotic system. Through automation, the developed system targets a vein phantom to within 20 μm and automatically cannulates and infuses the vascular lumen with dyed water. The system was evaluated through 30 experimental trials and shown to be capable of performing automated cannulation of retinal vein phantoms with no reported cases of failure.

Comprehensive characterization of ExacTrac stereoscopic image guidance system using Monte Carlo and Spektr simulations

The purpose of this work is to develop accurate computational methods to comprehensively characterize and model the clinical ExacTrac imaging system, which is used as an image guidance system for stereotactic treatment applications.The Spektr toolkit was utilized to simulate the spectral and imaging characterization of the system. Since Spektr only simulates the primary beam (ignoring scatter), a full model of ExacTrac was also developed in Monte Carlo (MC) to characterize the imaging system. To ensure proper performance of both simulation models, Spektr and MC data were compared to the measured spectral and half value layers (HVLs) values.To validate the simulation results, x-ray spectra of the ExacTrac system were measured for various tube potentials using a CdTe spectrometer with multiple added narrow collimators. The raw spectra were calibrated using a 57Co source and corrected for the escape peaks and detector efficiency. HVLs in mm of Al for various energies were measured using a calibrated RaySafe detector. Spektr and MC HVLs were calculated and compared to the measured values. The patient surface dose was calculated for different clinical imaging protocols from the measured air kerma and HVL values following the TG-61 methodology. The x-ray focal spot was measured by slanted edge technique using gafchromic films. ExacTrac imaging system beam profiles were simulated for various energies by MC simulation and the results were benchmarked by experimentally acquired beam profiles using gafchromic films. The effect of 6D IGRT treatment couch on beam hardening, dynamic range of the flat panel detector and scatter effect were determined using both Spektr simulation and experimental measurements.The measured and simulated spectra (of both MC and Spektr) for various kVps were compared and agreed within acceptable error. As another validation, the measured HVLs agreed with the Spektr and MC simulated HVLs on average within 1.0% for all kVps. The maximum and minimum patient surface doses were found to be 1.06 mGy for shoulder (high) and 0.051 mGy for cranial (low) imaging protocols, respectively. The MC simulated beam profiles were well matched with experimental results and replicated the penumbral slopes, the heel effect, and out-of-field regions. Dynamic range of detector (in terms of air kerma at detector surface) was found to be in the range of [6.1 × 10−6, 5.3 × 10−3] mGy.Accurate MC and Spektr models of the ExacTrac image guidance system were successfully developed and benchmarked via experimental validation. While patient surface dose for available imaging protocols were reported in this study, the established MC model may be used to obtain 3D imaging dose distribution for real patient geometries.

DDEL-05. BLOOD-BRAIN BARRIER DISRUPTION AND ENHANCED RADIOSENSITIZERS EXTRAVASATION UPON FOCUSED ULTRASOUND FOR TREATMENT OF DIFFUSE INTRINSIC PONTINE GLIOMA

Poor prognosis of diffuse midline glioma, including diffuse intrinsic pontine glioma (DIPG), reflects the low efficacy of current treatment strategies, mainly due to (1) a largely intact blood-brain barrier (BBB) and (2) the proficiency of tumour tissues to upregulate multiple DNA repair genes, resulting into radio-resistance. In vitro studies showed therapeutic benefit by combining radiotherapy and radiosensitizers, while pre-clinical and clinical studies evidenced safe and transient opening of the BBB using microbubble mediated focused ultrasound (FUS). Previously, we demonstrated the enhanced extravasation of olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor in the mouse pons. Local drug delivery was applied using an in-house built X-ray image-guided FUS system with a 1 MHz mono-element transducer delivering a tone-burst pulse with a mechanical index of 0.4. Tissue/blood drug concentrations were analysed by LC-MS/MS, 30 minutes after intraperitoneal injection of 10 mg/kg olaparib. The FUS system allowed for precise treatment of the pons, proven by local extravasation of Evans Blue-conjugated albumin. A significant 5.1 fold median increase was observed in absolute concentrations in the pons after FUS intervention compared to the control and a 4.9 fold increase of the median tissue-blood ratio (*p<0.05). No significant differences were detected in brain regions outside the ultrasound focus and other organs, confirming the local intervention. With this, the 299 nM equivalent olaparib concentration found in the pons will facilitate PARP inhibition in future murine patient-derived xenograft tumour models, thus leading to a greater therapeutic effect when in combination with radiotherapy treatment of DIPG.

Infrared Target Tracking Based on Improved Particle Filtering

Infrared target tracking technology is one of the core technologies in infrared imaging guidance systems and is also a hot research topic. The problem of particle degradation could be always found in traditional particle filtering, and a large number of particles are additionally required for accurate estimation. It is difficult to meet the requirements of a modern infrared imaging guidance system for accurate target tracking. To solve the problem of particle degradation and improve the performance of infrared target tracking, the extended Kalman filter and genetic algorithm are introduced into particle filtering, and an improved algorithm for infrared target tracking is proposed in this paper. In the framework of a particle filter algorithm, the Gaussian distribution for each particle is generated and propagated by a separate extended Kalman filter to improve the sampling accuracy and effectiveness of the probability density function of particles. Genetic algorithm is used to perform a resampling process to solve particle degradation and ensure the diversity of particle states in particle swarm. Simulation results show that the improved tracking algorithm based on improved particle filtering proposed in this paper can effectively solve the phenomenon of particle degradation and track the infrared target.