High-speed Image Acquisition Research Articles

Development of a high speed imaging microscope and new software for nuclear track detector analysis

Automated digital imaging optical microscopy is widely used for diagnostic applications in the health care and biology fields and for routine inspection in industrial applications such as semiconductor fabrication. These applications require the imaging of large areas at high speed in order to obtain sufficient data for image processing with good statistics. Track detector analysis also benefits from the rapid acquisition of large areas on the detector surface. We have developed a new microscope system, the HSP-1000, for high speed image acquisition that uses a line sensor camera in place of a traditional CCD camera. Continuous, automatic focusing of the microscope is achieved by means of an optical pick-up system that provides fast feedback for control of distance between the objective and the image surface. Using transmitted light illumination, the microscope is able to digitize a 1 cm 2 area at 0.35 μ m / pixel resolution in ∼ 20 s . As a result of continuous stage motion and continuous focusing, we have attained image acquisition speeds that are 50–100 times faster than conventional CCD-based microscope systems. In this paper, we describe a number of aspects of the microscope system including the use of the line sensor and the automatic focus system.

A variational approach to magnetic resonance coil sensitivity estimation

A variational method for estimating a magnetic resonance coil sensitivity from its corresponding non-uniform illumination of magnetic resonance images is proposed and analyzed. The estimated sensitivity can then be used to correct non-uniformities and indeed to facilitate high-speed parallel image acquisition. The data available for estimation include two images of the same field of view but obtained with and without a uniform coil sensitivity. The non-uniformly illuminated image is ideally the product of the uniformly illuminated image with the coil sensitivity. Thus, the desired sensitivity is estimated roughly from a quotient of the two given images over the effective data support. However, the measurements are corrupted by noise, the data are discontinuous at tissue boundaries, and yet the coil sensitivity is very smooth. In the selected estimation procedure, the sum of a residual and a high order penalty is minimized. In this form, the problem is related to the surface estimation problem of early vision. In the present context, higher coil sensitivity decay rates are captured non-parametrically by higher order penalties together with natural boundary conditions. The role of alternative penalties and boundary conditions is investigated both analytically and numerically. Although high order operators are often approximated numerically with a product of low order factors, such factorizations are shown here to lead to conspicuously spurious boundary conditions for surface estimation with sparse data support. Furthermore, while finite elements present a natural numerical approach for solving the optimality system, it is demonstrated here that lumping is required to avoid aberrant consequences in the limit of vanishing regularization corresponding to an ever improving signal-to-noise ratio. Finally, with a proper analytical and numerical formulation, the estimation procedure is demonstrated for a magnetic resonance imaging application involving parallel image acquisition.

Investment Strategies in Private Equity

We present a method for localised two-photon photoconversion of fluorescent cells within distinct microanatomical compartments in intact lymph nodes. This method allows efficient photoconversion of whole cell populations as well as of single cells while preserving cell viability and motility. Moreover, the combination of high-speed image acquisition and real-time display permits us to target and lock-on to individual cells for photoconversion as they migrate within the lymph node. Optical cell marking makes it possible to differentiate otherwise homogenous responding cells based on their microanatomical location. It also enables discontinuous in vivo tracking of cell fates to distal sites after extended time intervals.

Prototype of an in vitro model of the microcirculation

We have used microfabrication technology to construct a network of microchannels, patterned after the dimensions and architecture of the mammalian microcirculation. The network is cast in transparent silicone elastomer and the channels are coated with silanated mPEG to provide lubrication. Flow of red and white blood cells through the network is readily visualized by the use of high-speed digital image acquisition. The acquired sequences of high-quality images are used to calculate hematocrits and rates of red cell movement in the microchannels. Our prototype system has significant advantages over scaled-up room-size experimental systems in that it permits experimentation with actual human blood cells. Experiments can be carried out under well-controlled conditions in a network of microchannels with precisely known dimensions using cell suspensions of defined composition. Moreover, there is no need to counteract or anticipate the host’s adaptive responses that may confound live animal experiments. Notwithstanding its limitations, the current prototype demonstrates certain features characteristic of the microcirculation, such as parachute and bullet shapes of red cells deformed in capillary channels, rouleaux formation, plasma skimming, and the utilization of collateral flow pathways due to flow obstruction caused by a white cell blocking a microchannel. We present this device as a prototype scale-to-scale model of the mammalian microcirculation. Limitations of the system as well as a variety of possible applications are described.

Identification of vertebral fractures in osteoporosis.

Osteoporosis is a systemic skeletal disease characterized by reduced bone mass and microarchitectural deterioration. These lead to subsequent increase in bone fragility and susceptibility to low-trauma or atraumatic fractures, most commonly vertebral fractures but also fractures of hip and wrist. These have a significant impact on morbidity, mortality, and health care cost. Studies have demonstrated that the presence of vertebral fractures is an independent and significant predictor of the increased risk for further fractures. The occurrence of a vertebral fracture is often clinically asymptomatic, and many of these fractures, therefore, remain undiagnosed. Recently, a number of techniques have been developed that allow for reliable identification of vertebral fractures on radiographs. The two most widely used methods in clinical research are the semiquantitative assessment of vertebral deformities, which is based on visual evaluation, and the quantitative approach, which is based on different morphometric criteria. In our practice for osteoporosis evaluation we use the Genant semiquantitative approach-an accurate and reproducible method, tested and applied in many clinical studies. The newest generation of fan-beam dual energy X-ray absorptiometry (DXA) systems delivering "high-resolution" lateral spine images offer a potential practical alternative to radiographs for clinical vertebral fracture analysis. The advantages of using DXA over conventional X-ray devices are its minimal radiation exposure and high-speed image acquisition. It also allows combined evaluation of vertebral fracture status and bone mineral density, which could become a standard for patient assessment in osteoporosis.

Dynamics of zigzag destabilized solitary stripes in a dc-driven pattern-forming semiconductor gas-discharge system

Zigzag destabilization of self-organized solitary stripes was detected recently in the current density of a planar semiconductor gas discharge system. In the present work it is revealed that this instability is accompanied by the propagation of the zigzag deformation along the body of a stripe. This phenomenon is quantitatively analyzed using a high-speed image acquisition technique based on a framing camera system. The velocity of propagation has been found to increase monotonously with the global electric current, while the characteristic wavelength of the pattern shows a complicated behavior. The connection of the obtained data to available results of theoretical analysis of secondary bifurcations of solitary stripes in reaction-diffusion media is considered.

Evaluation of adnexal masses using three-dimensional ultrasonographic technology: preliminary report

The purpose of the current study was to demonstrate the ability of three-dimensional ultrasonographic technology to enhance the morphologic scoring system and further improve the ability to differentiate benign from malignant ovarian masses. We performed conventional two-dimensional and three-dimensional transabdominal and transvaginal ultrasonography on eight women with adnexal masses. All patients underwent exploratory laparotomy or diagnostic laparoscopy. The three-dimensional ultrasonographic findings were compared with the two-dimensional ultrasonograms, the intraoperative observations, and gross and histopathologic findings. The morphologic scoring system as described by Sassone and coworkers was adopted, with scores of less than 9 suggestive of benign lesions, and this system was applied in both the two-dimensional and three-dimensional ultrasonographic examinations. The morphologic scores were subsequently compared. The images were dissected in the XYZ planes, and the areas suggestive of malignancy, as suggested by two-dimensional ultrasonography, were determined to be either negative or positive and confirmatory. In each of the eight adnexal masses, three-dimensional ultrasonography confirmed the preoperative diagnoses. The morphologic scores did not differ between two-dimensional and three-dimensional ultrasonograms for the benign cysts. In one case of benign solid fibroma, both the two-dimensional and three-dimensional gray scale morphologic scores were falsely positive at greater than 9. In one case of malignant serous papillary cystadenocarcinoma the two-dimensional morphologic score was a 9, where- as the three-dimensional score was 13. This difference in scores can be attributed to the additional views available with three-dimensional volume scanning, which allowed better characterization of the pathologic conditions. In addition, three-dimensional sonographic technology had the added advantage of high-speed image acquisition and recording to decrease the time of scanning to improve patient comfort. Furthermore, three-dimensional ultrasonography allowed the real-time analysis of the acquired image data to be conducted at a later time when the patient is off the examination table. Our preliminary results suggest that three-dimensional transvaginal ultrasonographic technology can enhance and facilitate the morphologic evaluation of both benign and malignant adnexal masses.

Evaluation of adnexal masses using three-dimensional ultrasonographic technology: preliminary report.

The purpose of the current study was to demonstrate the ability of three-dimensional ultrasonographic technology to enhance the morphologic scoring system and further improve the ability to differentiate benign from malignant ovarian masses. We performed conventional two-dimensional and three-dimensional transabdominal and transvaginal ultrasonography on eight women with adnexal masses. All patients underwent exploratory laparotomy or diagnostic laparoscopy. The three-dimensional ultrasonographic findings were compared with the two-dimensional ultrasonograms, the intraoperative observations, and gross and histopathologic findings. The morphologic scoring system as described by Sassone and coworkers was adopted, with scores of less than 9 suggestive of benign lesions, and this system was applied in both the two-dimensional and three-dimensional ultrasonographic examinations. The morphologic scores were subsequently compared. The images were dissected in the XYZ planes, and the areas suggestive of malignancy, as suggested by two-dimensional ultrasonography, were determined to be either negative or positive and confirmatory. In each of the eight adnexal masses, three-dimensional ultrasonography confirmed the preoperative diagnoses. The morphologic scores did not differ between two-dimensional and three-dimensional ultrasonograms for the benign cysts. In one case of benign solid fibroma, both the two-dimensional and three-dimensional gray scale morphologic scores were falsely positive at greater than 9. In one case of malignant serous papillary cystadenocarcinoma the two-dimensional morphologic score was a 9, where- as the three-dimensional score was 13. This difference in scores can be attributed to the additional views available with three-dimensional volume scanning, which allowed better characterization of the pathologic conditions. In addition, three-dimensional sonographic technology had the added advantage of high-speed image acquisition and recording to decrease the time of scanning to improve patient comfort. Furthermore, three-dimensional ultrasonography allowed the real-time analysis of the acquired image data to be conducted at a later time when the patient is off the examination table. Our preliminary results suggest that three-dimensional transvaginal ultrasonographic technology can enhance and facilitate the morphologic evaluation of both benign and malignant adnexal masses.

Rapid acquisition of in vivo biological images by use of optical coherence tomography

The development of techniques for high-speed image acquisition in optical coherence tomography (OCT) systems is essential for suppressing motion artifacts when one is imaging living systems. We describe a new OCT system for performing micrometer-scale, cross-sectional optical imaging at four images/s. To achieve OCT image-acquisition times of less than 1 s, we use a piezoelectric fiber stretcher to vary the reference arm delay. A Kerr-lens mode-locked chromium-doped forsterite laser is employed as the low-coherence source for the highspeed OCT system. Dynamic, motion-artifact-free in vivo imaging of a beating Xenopus laevis (African frog) heart is demonstrated.

A fast scanner for fluorescence microscopy using a 2-D CCD and time delayed integration

We have developed an imaging system for high speed image acquisition in fluorescence microscopy. The use of a two- dimensional CCD array in a special operation mode called TDI (Time Delayed Integration) permits a significant increase in photon integration time compared to 1D scanners (higher signal-to-noise ratio) without compromising the total data throughput rate. Instead of a start–stop system we use continuous stage motion in the CCDs parallel shift direction. Synchronizing the parallel clock and the stage velocity guarantees a one-to-one relationship between a moving cell and its image onto the CCD. Compared to start-stop system, TDI scanning offers a speed improvement, negligible blurring in the scanning direction and a complete suppression of pixel variability boosting the SNR more than 10 dB.

A high-speed image acquisition system for robotics

There are many applications in industry for imaging systems. The majority of these use a video camera as the input device. The output from the camera is sampled and stored in memory and a computer used to analyse the image. Until recently, the time for the analysis of the image was relatively long in comparison with the acquisition time of the image. However, with the development of new high-speed microprocessors decreasing the processing time, the acquisition time of the image will become the limiting factor of the analysis rate. This paper describes the development of a prototype system to make possible the capture of a full frame image (256 lines), in under 15 ms, for analysis by a computer. With the use of programmable logic devices (PLDS) and hardware windowing techniques, the acquisition time for a part frame (40 lines) is 2.8 ms. Shorter acquisition times can be obtained, but with reduned resolution. An application of the imaging system is also presented.

An electron-beam inspection system for x-ray mask production

SEMSpec is a scanning electron-beam inspection system designed for high-resolution die-to-die inspections of conductive x-ray masks, wafer prints, or stencil masks in a production environment. The inspection sensitivity can be varied from 97% detection of 50-nm defects, at a rate of 27 min cm−2, to 97% detection of 250-nm defects at 1 min cm−2. A thermal-field-emission source produces a Gaussian profile electron beam that is moved by electrostatic deflectors over the continuously moving substrate that is being inspected. Secondary electrons from the substrate are collected in a high-speed detector and the resulting digitized image data is stored in a specialized memory system. Pairs of images to be compared are continuously transferred from the memory to a high-speed defect processor for analysis. Defect reports from the defect processor are analyzed during inspection and stored for subsequent review. We describe the overall system including the electron-beam column with its six-emitter field-emission gun, the deflection system, the secondary-electron detector, the linear-motor drive stage, the control system, the robotic mask handler, and the image-data flow from the high-speed image acquisition subsystem through the analysis system. The electron-beam column is described in detail in a companion paper [W. D. Meisburger, A. A. Desai, and A. D. Brodie, J. Vac. Sci. Technol. B 9, xxxx (1991)]. All functions of the highly automated system—including vacuum control, mask loading, electron-beam column setup, and inspection— can be operated from the system control computer.

MR fluoroscopy: initial clinical studies.

Magnetic resonance (MR) fluoroscopy is a method for high-speed MR image acquisition with the goals of short acquisition time per image (500 msec or less), high image rate (10 images or more per second), and high-speed image reconstruction (150 msec or less from data acquisition to image display). The authors present their results with the first two goals in volunteers. MR fluoroscopic image data were acquired with a limited flip angle pulse sequence with reduced repetition times (TRs) and fewer phase encodings used per image. The sequence was applied continuously, and images were formed by updating one set of data with data from the most recently taken measurements. Sample head images were generated with TR/echo times as small as 11/5.5 msec and 48 phase encodings for a total acquisition time of about 500 msec. Images were acquired while the volunteer flexed his head. Artifacts from the motion became less evident on images as progressively shorter acquisition times were used.

Applications of real-time image processing for electron microscopy

Using a television-rate, digital image processing system, a number of applications areas for electron microscopy have been developed for high-speed performance. The main component of the system is a digital television frame store which is linked to a large mainframe computer. Many features of the frame store such as digitization, zoom and pan, arithmetic and Boolean processors, image video routing, lookup table modification and histogram generation can be performed rapidly from menu-driven software. It is the purpose of this paper to describe methods whereby high-speed image creation, acquisition, manipulation and measurements can be made using the above mentioned frame store functions as opposed to the images being processed or modified on the host computer. Examples will be given in the areas of multiple image digitization, optimal imaging determination via gray-level histograms, contrast correction and compression, particle analysis and Fourier analysis.