基于悬臂梁模型的针挠曲预测

目的 分析针穿刺组织过程中的挠曲量和穿刺针受力情况，提高针穿刺精度。方法 搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验，利用力传感器得到不同穿刺速度（5、10和15 mm/s）下的穿刺力，通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上，构建预测针挠曲量的悬臂梁模型。结果 利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测，其绝对误差小于0.5 mm，相对误差小于10%。结论 所建模型能够实现对针穿刺挠曲的预测，可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

基于悬臂梁模型的针挠曲预测

目的 分析针穿刺组织过程中的挠曲量和穿刺针受力情况,提高针穿刺精度。方法 搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验,利用力传感器得到不同穿刺速度（5、10和15 mm/s）下的穿刺力,通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上,构建预测针挠曲量的悬臂梁模型。结果 利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测,其绝对误差小于0.5 mm,相对误差小于10%。结论 所建模型能够实现对针穿刺挠曲的预测,可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

基于悬臂梁模型的针挠曲预测

目的分析针穿刺组织过程中的挠曲量和穿刺针受力情况,提高针穿刺精度。方法搭建包括工业相机、步进电机和光源等组成的测量设备。用针轴直径分别为1.3、0.9、0.6 mm的穿刺针进行针穿刺软组织实验,利用力传感器得到不同穿刺速度(5、10和15 mm/s)下的穿刺力,通过数字图像处理得到穿刺针的挠曲量。在分析针受力的基础上,构建预测针挠曲量的悬臂梁模型。结果利用悬臂梁模型对直径为1.3、0.6 mm穿刺针在5 mm/s速度下的挠曲量进行预测,其绝对误差小于0.5 mm,相对误差小于10%。结论所建模型能够实现对针穿刺挠曲的预测,可以为机器人辅助柔性针穿刺路径规划和避障运动提供参考。     

Measurement and Stochastic Modeling of Kidney Puncture Forces

The development of needle insertion robots and training simulators requires knowledge of the forces that arise when a needle is inserted into soft-tissue. The present study aims to construct stochastic models of the force required to puncture a kidney using a trocar needle, based on measurements. To this end, a total of sixty insertions were performed into porcine kidneys (ex vivo), at constant speed, using a linear motion stage. Axial force was measured at the needle hub and an ultrasound probe moved with the needle to enable identification of anatomical structures. Two force peaks were observed for each tissue layer punctured, one caused by the tip and one by the edge of the cannula. Based on ultrasound data these double-peaks were classified into four groups, related to kidney capsule and internal structures. Group size varied from 7 to 55 double-peaks. Force peaks in each group were evaluated in terms of peak force and drop in force for both tip and cannula, and stochastic models were constructed that describe the multivariate distribution of these metrics. Peak forces in the capsule and internal structures ranged up to 2 N and 8 N, respectively. The resulting models can be used to simulate kidney puncture events in a variety of applications.     

An MRI-Guided Telesurgery System Using a Fabry-Perot Interferometry Force Sensor and a Pneumatic Haptic Device

This paper presents a surgical master-slave teleoperation system for percutaneous interventional procedures under continuous magnetic resonance imaging (MRI) guidance. The slave robot consists of a piezoelectrically actuated 6-degree-of-freedom (DOF) robot for needle placement with an integrated fiber optic force sensor (1-DOF axial force measurement) using the Fabry-Perot interferometry (FPI) sensing principle; it is configured to operate inside the bore of the MRI scanner during imaging. By leveraging the advantages of pneumatic and piezoelectric actuation in force and position control respectively, we have designed a pneumatically actuated master robot (haptic device) with strain gauge based force sensing that is configured to operate the slave from within the scanner room during imaging. The slave robot follows the insertion motion of the haptic device while the haptic device displays the needle insertion force as measured by the FPI sensor. Image interference evaluation demonstrates that the telesurgery system presents a signal to noise ratio reduction of less than 17% and less than 1% geometric distortion during simultaneous robot motion and imaging. Teleoperated needle insertion and rotation experiments were performed to reach 10 targets in a soft tissue-mimicking phantom with 0.70 ± 0.35 mm Cartesian space error.     

Needle insertion into soft tissue: a survey

Needle insertion in soft tissue has attracted considerable attention in recent years due to its application in minimally invasive percutaneous procedures such as biopsies and brachytherapy. This paper presents a survey of the current state of research on needle insertion in soft tissue. It examines the topic from several aspects, e.g. modeling needle insertion forces, modeling tissue deformation and needle deflection during insertion, robot-assisted needle insertion, and the effect of different trajectories on tissue deformation. All studies show that the axial force of a needle during insertion in soft tissue is the summation of different forces distributed along the needle shaft such as stiffness force, frictional force and cutting force. Some studies have modeled these forces. The force data in some procedures is used for identifying tissue layers as the needle is inserted or for path planning. Needle deflection and tissue deformation are major problems for accurate needle insertion and attempts have been made to model them. Using current models several insertion techniques have been developed which are briefly reviewed in this paper.     

Dose area product evaluations with Gafchromic XR-R films and a flat-bed scanner

Gafchromic XR-R films are a useful tool to evaluate entrance skin dose in interventional radiology. Another dosimetric quantity of interest in diagnostic and interventional radiology is the dose area product (DAP). In this study, a method to evaluate DAP using Gafchromic XR-R films and a flat-bed scanner was developed and tested. Film samples were exposed to an x-ray beam of 80 kVp over a dose range of 0-10 Gy. DAP measurements with films were obtained from the digitalization of a film sample positioned over the x-ray beam window during the exposure. DAP values obtained with this method were compared for 23 cardiological interventional procedures with DAP values displayed by the equipment. The overall one-sigma dose measurement uncertainty depended on the absorbed dose, with values below 6% for doses above 1 Gy. A maximum discrepancy of 16% was found, which is of the order of the differences in the DAP measurements that may occur with different calibration procedures. Based on the results presented, after an accurate calibration procedure and a thorough inspection of the relationship between the actual dose and the direct measured quantity (net optical density or net pixel value variation), Gafchromic XR-R films can be used to assess the DAP.     

Feasibility of a semiconductor dosimeter to monitor skin dose in interventional radiology.

The design and preliminary test results of a semiconductor silicon dosimeter are presented in this article. Use of this dosimeter is foreseen for real-time skin dose control in interventional radiology. The strong energy dependence of this kind of radiation detector is well overcome by filtering the silicon diode. Here, the optimal filter features have been calculated by numerical Monte Carlo simulations. A prototype has been built and tested in a radiological facility. The first experimental results show a good match between the filtered semiconductor diode response and an ionization chamber response, within 2% fluctuation in a 2.2 to 4.1 mm Al half-value layer (HVL) energy range. Moreover, the semiconductor sensor response is linear from 0.02 Gy/min to at least 6.5 Gy/min, covering the whole dose rate range found in interventional radiology. The results show that a semiconductor dosimeter could be used to monitor skin dose during the majority of procedures using x-rays below 150 keV. The use of this device may assist in avoiding radiation-induced skin injuries and lower radiation levels during interventional procedures.     

Use of puncture force measurement to investigate the conditions of blood vessel needle insertion

Central venous catheterization involves venous puncture and catheter insertion for transfusions. Quantitative conditions that facilitate insertion of the needle, such as the angle and velocity of insertion, have not been clarified. We previously developed a robotic system for guiding the needle along a specified puncture path with high precision and are currently implementing a hardware design for a robotic system to assist in blood vessel puncture. In this study, we proposed the insertion angle and velocity for stopping the needle in a blood vessel, assuming that a robotic system such as ours is used during the procedure. We inserted a needle into a segment of porcine jugular vein and obtained the puncture reaction force. Evaluation indices were the magnitude of the sudden decrease in reaction force at the point at which the needle advances and the length of time that the needle is present within the vein. Results indicated that the conditions under which it was easiest to stop the needle inside the vein were an insertion angle range of 10–20 and an insertion velocity of 3 mm/s.     

An Artificial Neural Network Approach to the Predictive Modeling of Tensile Force during Renal Suturing

Further understanding of the mechanical deformation and tear behavior of kidney during suturing helps to enhance surgical task execution that requires fine suture manipulation. This paper aims to develop a model to describe the relationship between the tensile force acting on suture line and the resulted kidney deformation in the tension of suture line. The tensile force was recorded during multiple suture procedures, filtered, and we extracted the force data between the beginnings of tensioning suture line and tearing renal remnant. The extracted data were interpolated to obtain the same data sample length for each suture procedure, and then used to train the back propagation (BP) neural network. In order to predict the tearing force, force data were collected in sequence and interpolated to be input into BP network. Suture processes were performed on in vitro porcine kidneys, and experimental results verified the effectiveness of predictive modeling and the accuracy of tearing force prediction. The relative error for tearing force prediction was about 15%. The predictive modeling method can be used to forecast the tearing force before the suture line tears through soft tissues.     

An augmented reality simulator for ultrasound guided needle placement training

Details are presented of a low cost augmented-reality system for the simulation of ultrasound guided needle insertion procedures (tissue biopsy, abscess drainage, nephrostomy etc.) for interventional radiology education and training. The system comprises physical elements; a mannequin, a mock ultrasound probe and a needle, and software elements; generating virtual ultrasound anatomy and allowing data collection. These two elements are linked by a pair of magnetic 3D position sensors. Virtual anatomic images are generated based on anatomic data derived from full body CT scans of live humans. Details of the novel aspects of this system are presented including; image generation, registration and calibration.     

Needle-tissue interaction forces--a survey of experimental data

The development of needles, needle-insertion simulators, and needle-wielding robots for use in a clinical environment depends on a thorough understanding of the mechanics of needle-tissue interaction. It stands to reason that the forces arising from this interaction are influenced by numerous factors, such as needle type, insertion speed, and tissue characteristics. However, exactly how these factors influence the force is not clear. For this reason, the influence of various factors on needle insertion-force was investigated by searching literature for experimental data. This resulted in a comprehensive overview of experimental insertion-force data available in the literature, grouped by factor for quick reference. In total, 99 papers presenting such force data were found, with typical peak forces in the order of 1-10N. The data suggest, for example, that higher velocity tends to decrease puncture force and increase friction. Furthermore, increased needle diameter was found to increase peak forces, and conical needles were found to create higher peak forces than beveled needles. However, many questions remain open for investigation, especially those concerning the influence of tissue characteristics.     

Patient dose management in digital radiography

Purpose:

To present the experience in patient dose management and the development of an online audit tool for digital radiography.

Materials and methods:

Several tools have been developed to extract the information contained in the DICOM header of digital images, collect radiographic parameters, calculate patient entrance doses and other related parameters, and audit image quality.

Results:

The tool has been used for mammography, and includes images from over 25,000 patients, over 75,000 chest images, 100,000 computed radiography procedures and more than 1,000 interventional radiology procedures. Examples of calculation of skin dose distribution in interventional cardiology based upon information of DICOM header and the results of dosimetric parameters for cardiology procedures in 2006 are presented.

Conclusion:

Digital radiology has great advantages for imaging and patient dose management. Dose reports, QCONLINE systems and the MPPS DICOM service are good tools to optimise procedures and to manage patient dosimetry data. The implementation of the ongoing IEC-DICOM standard for patient dose structured reports will improve dose management in digital radiology.     

Adult patient doses in interventional neuroradiology

We investigated radiation doses to 149 adult patients who underwent interventional neuroradiologic procedures, consisting of 132 patients who had diagnostic imaging examinations and 17 patients who had therapeutic procedures. The interventional procedures were carried out on a biplane system capable of performing fluoroscopy and digital subtraction angiography (DSA). The x-ray imaging system was interfaced to a patient dosimetry system, which computed surface (skin) doses based on the selected radiographic technique factors in each of the radiographic and fluoroscopic imaging modes. For each patient, an assessment was made of the maximum surface dose received during the procedure, which predicts the possibility of inducing deterministic effects. Knowledge of the surface doses, beam quality and x-ray cross sectional area permitted the computation of the total energy imparted to each patient. Energy imparted values were converted to effective dose, which provides an estimate of the stochastic radiation risk to the patient. The median surface dose for the frontal plane during diagnostic imaging examinations was 1.3 Gy, with a maximum surface dose of 5.1 Gy. The median surface dose for the frontal plane during therapeutic procedures was 2.8 Gy with a maximum surface dose of 5.0 Gy. Ratios of the lateral to frontal median surface doses were 0.47 for diagnostic examinations and 0.68 for interventional procedures. The median energy imparted was 1.8 J during fluoroscopy, and 4.3 J during radiography, showing that on average, 66% of the patient exposure comes from radiographic imaging (DSA). For diagnostic examinations, the median patient effective dose was 33 mSv, with a maximum of 152 mSv. For therapeutic procedures, the median patient effective dose was 74 mSv, with a maximum of 156 mSv. In interventional neuroradiology, surface doses could induce deterministic effects, and the corresponding effective doses are noticeably higher than those normally encountered in diagnostic radiology.     

Oesteogenic Study of Lumbosacral Transitional Vertebra in Central India Region

The morphological variations in the lumbosacral region are accidental findings during the study of dry human sacra. Most easily identified and detectable anatomical variations are related with change in the number of sacral vertebra by union of fifth lumbar vertebra or first coccyx and deletion of first sacral vertebra. These variations may be found in the living during radiological investigations for pain and neurological symptoms of patients.The study was designed to know the prevalence of Lumbosacral Transitional Vertebra in Central India as there is paucity of available literature. Considering the variations, we conduct this study as a prelude to any type of experimental work in biomechanics, for diagnostic and therapeutic purposes in low back pain and for interventional procedures like spinal anesthesia and lumbar puncture.Setting & Design: Observational study was carried out on 206 dry sacra including human skeletons obtained from Department of Anatomy and Forensic Medicine & Regional Medicolegal Institute of Bhopal & Raipur.Morphometric measurements of 168 normal and 38 lumbosacral transitional vertebras were recorded and classified as per Castellvi's classification. Sacra showing fusion of coccyx were also included. All the parameters of variant sacra were compared with normal sacra.38 (18.4%) lumbosacral transitional vertebra of which 29 (14.1 %) cases of sacralization, 9 (4.3%) cases of lumbarization and 16 (7.8%) cases of fusion of coccyx were found. 14(36.8%), 5(13.2%),17(44.7%) and 2(5.3%) sacra falls in type I; type II, type III and type IV of Castellvi's classification.Lumbosacral transitional vertebra is attributed to its embryological origin. These variations is outcome of series of morphological changes during the transition and may interfere with the normal functioning because of compression of nerves, soft tissue and ligamentous strain between joints. Knowledge of these variations have become increasing important because of increased incidence of lower back pain, sciatica, disc prolapsed and in interventional procedures like spinal anesthesia and lumbar puncture.     

Biopsy needle tips with markers--MR compatible needles for high-precision needle tip positioning

Needle tip visualization is of high importance in magnetic resonance imaging (MRI) guided interventional procedures, for example for taking biopsies from suspicious lesions in the liver or kidney. The exact position of the needle tip is often obscured by image artifacts arising from the magnetic properties of the needle. The authors investigated two special biopsy needle tip designs using diamagnetic coatings. For common interventional MR sequences, the needle tip can be identified in the MR image by several equidistant dark spots arranged along a straight line. A dotted instead of a solid line allows for an improved control of the movement of the needle, not only if the needle is tilted toward the imaging plane, but also if the needle leaves an empty canal with signal extinction, which cannot be distinguished from the needle material itself. With the proposed design the position of the needle tip can be estimated with a precision of approximately 1 mm using conventional FLASH, FISP, and TSE sequences, as used for interventional MR. Furthermore, the size of the biopsy probe can be estimated from the artifact. In using needles with a properly designed tip coating, taking biopsies under MR control is beginning to be greatly simplified. The approach to design artifacts using diamagnetic material in combination with paramagnetic material paves the way toward new instruments and implants, suitably tailored to the needs of the interventional radiologist.     

A wireless sensor network system to determine biomechanics of spinal braces during daily living

A spinal brace is a hard shell corset used to treat scoliosis. The force distribution inside the brace is not well understood. This study developed a battery-powered wireless sensor network to continuously monitor forces exerted by the braces to scoliotic patients. This network consisted of one master, up to 15 slave loggers, and one base station. The time of the loggers were synchronized every 6 h to ensure that force measurements were taken at the same time. Each logger could continuously log data for at least 4 months with a sample rate of 1 sample/min. The wireless system was fully tested in the laboratory and individual logger units were tested in 6 patients. The power consumption of each logger for 4 months at 1.2 V was 454 mAh. This system will allow us to investigate the force distribution inside the brace during daily activities.     

Combining ultrasound-based elasticity estimation and FE models to predict 3D target displacement

During minimally invasive surgical procedures (e.g., needle insertion during interventional radiological procedures), needle–tissue interactions and physiological processes cause tissue deformation. Target displacement is caused by soft-tissue deformation, which results in misplacement of the surgical tool (needle). This study presents a technique to predict target displacement in three-dimensions (3D) by combining soft-tissue elasticity estimation using an ultrasound-based acoustic radiation force impulse (ARFI) technique and finite element (FE) models. Three different phantoms with targets are manufactured, and subjected to varying loading and boundary conditions. Ultrasound images are acquired using a 3D probe during loading and unloading of each phantom, and subsequently target displacement is calculated. 3D FE models of the phantoms are developed, and they are used to predict target displacement. The maximum absolute error in target displacement between the experiments and FE analyses is found to be 1.39 mm. This error is less than the smallest tumor diameter (2.0–3.0 mm) which can be detected in breast tissue. This study shows that the combination of soft-tissue elasticity estimation using the ARFI technique and 3D FE models can accurately predict target displacement, and could be used to develop patient-specific plans for surgical interventions.     

Accidental blood exposure: risk and prevention in interventional radiology

There is a growing concern about the transmission of bloodborne pathogens during medical procedures among health care workers and patients. Over the last three decades, radiological services have undergone many changes with the introduction of new modalities. One of these new disciplines is interventional radiology (IR) which deals with procedures such as arteriography, image-guided biopsies, intravascular catheter insertions, angioplasty and stent placements. Despite these developments, the potential for accidental blood exposure and exposure to other infectious material continues to exist. Therefore, it is important for all radiologists who perform invasive procedures to observe specific recommendations for infection control. In this review, we look at the different policies for protection and universal standards on infection control.     

In vitro assessment of the trackability of neurovascular intermediate catheters: a comparative analysis

The advent of new flexible intermediate catheters facilitated manual aspiration thrombectomy (MAT) for treating neurovascular ischaemic diseases. While these catheters are somewhat flexible, most catheters were not designed specifically for aspiration. Trackability is an important property of catheters facilitating catheter advancement in highly tortuous cerebrovasculature. In this study, a novel in vitro trackability test system has been developed using micro pressure transducers and silicone tubes. The exerted force from the catheter tips were quantitatively evaluated while the catheter passed the curved regions. The trackability of three different types of catheters were compared, i.e. Penumbra 054, Concentric DAC 057 and Reverse Reflex. The exerted forces obtained from the first sensor (Sensor 1) during passing the second curve showed the maximum values through the entire transcatheter procedure. When compared, the exerted forces were least for the Penumbra 054 (0.272?±?0.012?N), representing highly trackable systems in highly tortuous vessel navigation.