应用OBI系统分析胸部肿瘤调强放疗的摆位误差

目的：应用机载影像系统（on boardinmger,OBl）分析胸部肿瘤调强放射治疗时分次间的摆位误差,并依此计算CTV外扩PTV边界的大小。方法：应用Varian-21EX医用直线加速器治疗47例胸部肿瘤。每周治疗前获取锥形束断层扫描（cone beam computed tomography,CBCT）图像,将CBCT图像和计划CT图像及其靶中心匹配,计算平移和旋转误差。结果：平移误差左右（x）方向为（-0．3194±3．6943）mm,头脚（y）方向为（0．4851±6．2636）mm,前后（z）方向为（0．4144±5．2818）mm;旋转误差冠状面（c）为（0．2080±1．4925）°,矢状面（s）为（0．0922±1．2976）°结沦：对于胸部肿瘤调强放疗（IMRT）,临床靶体积（CTV）到计划靶体积（PTV）的外放边界在左右方向宜为7mm,头脚方向宦为11mm,前后方向宜为10mm。考虑到旋转误差,与靶区比较长时靶区两端外放要更大一些.     

提高渡越辐射强度的一种方法

本文在分析了高能相对论电子通过介质箔组时产生的渡越辐射量子谱的特点、产生渡越辐射的机理,以及影响渡越辐射强度提高的主要不利因素的基础上,提出了一种提高渡越辐射强度的新方法.     

A post-coding scheme for peak-to-average power ratio reduction in intensity modulated optical OFDM systems

An efficient post-coding strategy is proposed in this letter to reduce the peak-to-average power ratio （PAPR） of orthogonal frequency division multiplexing （OFDM） signals for optical intensity modulated direct detection （IM/DD） systems. The post-coding scheme based on discrete cgsine transform （DCT） is employed after the inverse fast Fourier transform （IFFT） in the transmitter to reduce the PAPR of OFDM signals. This method is different from the conventional pre-coding scheme which is employed before IFFT operation. Numerical simulations demonstrate that the new DCT post-coding strategy can significantly reduce the PAPR than the conventional pre-coding scheme. Meantime, the bit error rate （BER） performance of the proposed post-coding system can be improved compared with the conventional pre-coding scheme.     

A sorting system for hierarchical grading of diabetic fundus images: a preliminary study

Diabetic retinopathy is a leading cause of blindness in developed countries. Diabetic patients can prevent severe visual loss by attending regular eye examinations and receiving timely treatments. In the United States, standard protocols have been developed and refined for years to provide better screening and evaluation procedures of the fundus images. Due to the emerging number of diabetic retinopathy cases, accurate and efficient evaluations of the fundus images have become a serious burden for the ophthalmologists or care providers. While diabetic retinopathy remains too complicated to call for an automatic diagnosis system, an efficient tool to facilitate the grading process with a limited number of personnel is in great demand. The current study is to develop a sorting system with a user-friendly interface, based upon the standardized early treatment diabetic retinopathy study (ETDRS) protocol, to assist the professional graders. The raw fundus images will be screened and assigned to different graders according to their skill levels and experiences. The developed hierarchical sorting process will greatly support the graders and enhance their efficiency and throughput. The proposed hybrid intelligent system with multilevel knowledge representation is used to construct this sorting system. A preliminary case study is conducted using only the features of the spot lesion group coupled with the ETDRS standard to demonstrate its feasibility and performance. The results obtained from the case study show a promising future.     

Virtual-reality-based multidimensional therapy for the treatment of body image disturbances in binge eating disorders: a preliminary controlled study

The main goal of this paper is to preliminarily evaluate the efficacy of a virtual-reality (VR)-based multidimensional approach in the treatment of body image attitudes and related constructs. The female binge eating disorder (BED) patients (n=20), involved in a residential weight control treatment including low-calorie diet (1200 cal/day) and physical training, were randomly assigned either to the multidimensional VR treatment or to psychonutritional groups based on the cognitive-behavior approach. Patients were administered a battery of outcome measures assessing eating disorders symptomathology, attitudes toward food, body dissatisfaction, level of anxiety, motivation for change, level of assertiveness, and general psychiatric symptoms. In the short term, the VR treatment was more effective than the traditional cognitive-behavioral psychonutritional groups in improving the overall psychological state of the patients. In particular, the therapy was more effective in improving body satisfaction, self-efficacy, and motivation for change. No significant differences were found in the reduction of the binge eating behavior. The possibility of inducing a significant change in body image and its associated behaviors using a VR-based short-term therapy can be useful to improve the body satisfaction in traditional weight reduction programs. However, given the nature of this research that does not include a followup study, the obtained results are preliminary only.     

A neural-network-based controller for the cost-effective operation of a hybrid compensator for nonactive power

The need to eliminate distortion from power networks has led to the development of various compensator topologies. The increasing cost of electrical energy requires the choice of the most cost-effective compensator operation. An investigation of a neural-network-based controller that chooses the most cost-effective compensator mode of operation on the basis of a continuous analysis of load conditions and the operational losses of the elements in the compensator structure are reported. The modeling of operational losses of each subtopology and the required control strategy are discussed. The results show that the operational loss savings due to the neural-network-controlled hybrid compensator were 30%-70% as compared to the conventionally controlled hybrid compensator, while also conforming to other control strategy requirements.     

Simulating measurements for a cable radiation study

Accurate numerical simulations are needed for analyzing and developing better electrical interconnects and electromagnetic compatibility (EMC) measurement systems. Numerical simulations enable one to predict the field behavior and compute the voltages, currents, impedances and other parameters of interest for a given structure such as cable shielding. A numerical simulation is used to analyze measured data from a cable radiation study. The finite difference time domain (FDTD) and the method of moments based Numerical Electromagnetics Code (NEC) are used to compute the total radiated power from the cable, and the results are shown to be in agreement with measured data. A numerical study is carried out to demonstrate the usefulness of the method at aiding the design of a measurement system without much additional experimental work     

An image sensor with an in-pixel demodulation function for detecting the intensity of a modulated light signal

An image sensor with an in-pixel demodulation function for detecting modulated light is proposed and demonstrated. The pixel has two floating diffusion regions, one of which stores charges produced by static illumination, and the other stores charges produced by both static and modulated illumination. By subtracting the two outputs, images produced only by the modulated illumination can be obtained. Based on the proposed circuit, an image sensor with 64 /spl times/ 64 pixels is fabricated using a 0.6 /spl mu/m two-poly three-metal CMOS technology. Using this sensor, we successfully demonstrate the extraction of the modulated component of images under constant illumination conditions. In addition, for the application of motion capture, we demonstrate that a marker, which is a modulated light source, can be extracted from a captured image under several light conditions by using this sensor. Finally, means of improving the characteristics of charge transfer efficiency are discussed.     

Real-time control of angioplasty balloon inflation based on feedback from intravascular optical coherence tomography: preliminary study on an artery phantom

A method is proposed to achieve computerized control of angioplasty balloon inflation, based on feedback from intravascular optical coherence tomography (IVOCT). Controlled balloon inflation could benefit clinical applications, cardiovascular research, and medical device industry. The proposed method was experimentally tested for balloon inflation within an artery phantom. During balloon inflation, luminal contour of the phantom was extracted from IVOCT images in real time. Luminal diameter was estimated from the obtained contour and was used in a feedback loop. Based on the estimated actual diameter and a target diameter, a computer controlled a programmable syringe pump to deliver or withdraw liquid in order to achieve the target diameter. The performance of the control method was investigated under different conditions, e.g., various flow rates and various target diameters. The results were satisfactory, as the control method provided convergence to the target diameters in various experiments.     

A physiologic regurgitant cardiac valve phantom for magneticresonance imaging or color Doppler ultrasound study

Noninvasive imaging has proven successful in the evaluation of valvular heart disease; primarily with magnetic resonance imaging (MRI) and color Doppler ultrasound (CFM). However, the relationship between the morphology of regurgitant flow in MRI and CFM, as a function of hemodynamic parameters (chamber pressure difference, lesion size, compliance, etc.) is not understood. The goals for this work were: 1) to develop a computer-controlled regurgitant cardiac valve phantom, compatible with artifact-free CFM and MR imaging, 2) to create regurgitant lesions in the phantom which appear similar to those detected clinically, 3) to produce and measure physiologic pressure differences between chambers, compliances, and regurgitant fractions as seen in mild, moderate, and severe regurgitation. Mean chamber pressure differences ranged from 43-142 mmHg over the range of diseases simulated. Similarly, regurgitant flow rates ranged from approximately 0.54-18.6 L/min. Compliance values ranged from 0.83 to 21.95 cc/mmHg. No coherent or incoherent artifacts were observed in MRI or CFM images. Images show a high degree of similarity to regurgitant lesions detected with each modality, confirming that all design goals were met. The system should allow extensive comparative analysis of Doppler ultrasound and MRI flow jets under a wide range of controllable hemodynamic conditions in future experiments.     

Experimental study of a dielectric rod enclosed by a waveguide for use as a feed

A dielectric rod enclosed by a short length of cylindrical waveguide has been studied for use as a feed for a reflector antenna. The feed dimensions are optimised experimentally with respect to the E- and H- plane pattern symmetry, low crosspolarisation and input matching. The v.s.w.r. and phase patterns are also described.     

基于相对辐射强度的非接触式LED结温测量法

提出了一种新的非接触式发光二极管(LED)结温测量的相对辐射强度法。利用该方法对不同功率、不同封装材料、不同颜色的LED进行结温测量,并与正向电压法测得的结果进行比较。结果表明,相对辐射强度法能准确地确定其结温,采用硅凝胶封装的大功率LED,误差在4℃以内;而采用环氧树脂封装的直径5mmLED,当其结温不超过80℃时,误差在6℃以内。     

Three-dimensional trajectory assessment of an IVUS transducer from single-plane cineangiograms: a phantom study

The recovery of the three-dimensional (3-D) path of the transducer used during an intravascular ultrasound (IVUS) examination is of primary importance to assess the exact 3-D shape of the vessel under study. Traditionally, the reconstruction is done by simply stacking the images during the pullback, or more recently using biplane angiography to recover the vessel curvature. In this paper, we explain, how single-plane angiography can be used with two projection models, to perform this task. Two types of projection geometry are analyzed: weak-perspective and full-perspective. In weak-perspective projection geometry, the catheter path can be reconstructed without prior transducer depth information. With full-perspective projection geometry, precise depth location of reference points are needed in order to minimize the error of the recovered transducer angle of incidence. The transducer angulation reconstruction is based on the foreshortening effect as seen from the X-ray images. By comparing the measured to the true transducer length, we are able to get its incidence angle. The transducer trajectory is reconstructed by stitching together the different estimated angulations obtained from each image in a cineangiogram sequence. The method is described and validated on two helical vessel phantoms, giving on average a reconstructed path that is less than 2 mm distant from the true path when using full-perspective projection.     

Tests for positive jumps in the intensity of a Poisson process: apower study

Tests are considered for the hypothesis of a constant intensity against the alternative of an intensity which increases with time in a nonhomogeneous Poisson process. Attention is focused on step-function alternatives and tests designed for such alternatives. One application is testing for abrupt changes in equipment following scheduled overhauls. The authors recommend the order-restricted likelihood-ratio test over an ordered chi-square test for such situations, provided the points at which jumps can occur are known. Otherwise, they recommend the test based on the Laplace statistic. The performance of these tests is evaluated for smooth alternatives, with the result that the smallest relative power of the order-restricted likelihood-ratio test is 73%, while for the Laplace test it is 82%. A numerical example based on failure times for a main-propulsion diesel engine is presented. The result is that the order-restricted likelihood-ratio test corresponds to the lowest statistical significance level     

A novel method to obtain modulus image of soft tissues using ultrasound water jet indentation: a phantom study

The alteration of tissue stiffness is generally known to be associated with pathological changes. Ultrasound indentation is one of the methods that can be used to assess the mechanical properties of the soft tissues. It uses a flat-ended ultrasound transducer to directly contact the tissue to sense tissue deformation under an applied load. This paper introduced a novel noncontact ultrasound indentation system using water jet compression. The key idea was to utilize a water jet as the indenter as well as the coupling medium for propagation of the ultrasound beam. High frequency focused ultrasound (20 MHz) was used to measure the indentation deformation at a microscopic level. It has been demonstrated that the system could effectively assess the tissue-mimic phantoms with different stiffness. Water jet coupling allows the system to conduct C-scan on soft tissues rapidly and conveniently. By applying different pressures while taking C-scan sequences, the modulus images of the phantoms could be obtained based on the applied pressure and the phantom deformation and thickness. This paper presented the preliminary results on gel phantoms. The spatial resolution, the contrast resolution of the measurements and the reproducibility of the results were also discussed.     

A new method for reflection and radiation analysis of dielectric rod antenna excited with the HE11 mode

A new method, which combines the edge-element method with the mode-matching procedure, is developed for the reflection and radiation analysis of the dielectric rod antenna excited by the HE₁₁ hybrid mode. Unlike the conventional method to treat the radiation as a “source-field” problem, in the present approach, the eigenvalue problem of the dielectric guided-wave structure is calculated first, and then the radiation problem is transferred to the propagation problem of a series of surface waves and space waves from the viewpoint of scattering. As a result, the analysis procedure is tremendously simplified. Numerical results calculated with the present method agree well with those given in the literature; thus the effectiveness of the present approach is verified.     

Real-time fusion of endoscopic views with dynamic 3-D cardiac images: a phantom study

Minimally invasive robotically assisted cardiac surgical systems currently do not routinely employ 3-D image guidance. However, preoperative magnetic resonance and computed tomography (CT) images have the potential to be used in this role, if appropriately registered with the patient anatomy and animated synchronously with the motion of the actual heart. This paper discusses the fusion of optical images of a beating heart phantom obtained from an optically tracked endoscope, with volumetric images of the phantom created from a dynamic CT dataset. High quality preoperative dynamic CT images are created by first extracting the motion parameters of the heart from the series of temporal frames, and then applying this information to animate a high-quality heart image acquired at end systole. Temporal synchronization of the endoscopic and CT model is achieved by selecting the appropriate CT image from the dynamic set, based on an electrocardiographic trigger signal. The spatial error between the optical and virtual images is 1.4 +/- 1.1 mm, while the time discrepancy is typically 50-100 ms. Index Terms-Image guidance, image warping, minimally invasive cardiac surgery, virtual endoscopy, virtual reality.     

A wideband spiral antenna for ingestible capsule endoscope systems: experimental results in a human phantom and a pig

This paper presents the design of a wideband spiral antenna for ingestible capsule endoscope systems and a comparison between the experimental results in a human phantom and a pig under general anesthesia. As wireless capsule endoscope systems transmit real-time internal biological image data at a high resolution to external receivers and because they operate in the human body, a small wideband antenna is required. To incorporate these properties, a thick-arm spiral structure is applied to the designed antenna. To make practical and efficient use of antennas inside the human body, which is composed of a high dielectric and lossy material, the resonance characteristics and radiation patterns were evaluated through a measurement setup using a liquid human phantom. The total height of the designed antenna is 5 mm and the diameter is 10 mm. The fractional bandwidth of the fabricated antenna is about 21% with a voltage standing-wave ratio of less than 2, and it has an isotropic radiation pattern. These characteristics are suitable for wideband capsule endoscope systems. Moreover, the received power level was measured using the proposed antenna, a circular polarized receiver antenna, and a pig under general anesthesia. Finally, endoscopic capsule images in the stomach and large intestine were captured using an on-off keying transceiver system.     

A study on the radiation loss from a bent transmission line

This paper deals with the radiation loss of bent transmission lines in order to determine the most optimal design for a bent line from the standpoint of radiation loss. We have used the method of moments (MoM) for a numerical analysis on the radiation for different structures of bent lines and we have found that the simplest right-angle bend is the best with the least radiation loss. This theoretical expectation was confirmed experimentally     

A note on a new walsh transformation method for delta modulated functions

In this paper an extremely simple device for the calculation of the Walsh Discrete Transform of a function which is delta modulated is presented. The design presented allows the Transform to be calculated with a very simple hardware and making the demodulation unnecessary.