Herbert D. Zeman

First operation of the medical research facility at the NSLS for coronary angiography

The Synchrotron Medical Research Facility (SMERF) at the National Synchrotron Light Source has been completed and is operational for human coronary angiography experiments. The imaging system and hardware have been brought to SMERF from the Stanford Synchrotron Radiation Laboratory where prior studies were carried out. SMERF consists of a suite of rooms at the end of the high‐field superconducting wiggler X17 beam line and is classified as an Ambulatory Health Care Facility. Since October of 1990 the coronary arteries of five patients have been imaged. Continuously improving image quality has shown that a large part of both the right coronary artery and the left anterior descending coronary artery can be imaged following a venous injection of contrast agent.

Prototype vein contrast enhancer

Two different prototype vein contrast enhancers (VCEs) have been designed and constructed. The VCE is an instrument that makes vein access easier by capturing an infrared image of peripheral veins, enhancing the vein contrast using software image processing, and projecting the enhanced vein image back onto the skin using a video projector. The prototypes use software alignment to achieve alignment accuracy between the captured infrared image and the projected visible image better than 0.06 mm.

Engineering Aspects of a Kinestatic Charge Detector

The engineering aspects of a nine-channel digital radiographic system developed for bioimaging research, based on high gas pressure ionography and kinestatic principles, are presented. The research imaging system uses a pulsed x-ray beam which allows one to study simultaneously the ionic signal characteristics at 10 different ionization sites along the drift axis. This research imaging detector system allows one to investigate methods to improve the detection and image quality parameters as part of the development of a large scale prototype medical imaging system.

Theoretical analysis and experimental evaluation of a CsI(Tl) based electronic portal imaging system

This article discusses the design and analysis of a portal imaging system based on a thick transparent scintillator. A theoretical analysis using Monte Carlo simulation was performed to calculate the x-ray quantum detection efficiency (QDE), signal to noise ratio (SNR) and the zero frequency detective quantum efficiency [DQE(0)] of the system. A prototype electronic portal imaging device (EPID) was built, using a 12.7 mm thick, 20.32 cm diameter, Csl(Tl) scintillator, coupled to a liquid nitrogen cooled CCD TV camera. The system geometry of the prototype EPID was optimized to achieve high spatial resolution. The experimental evaluation of the prototype EPID involved the determination of contrast resolution, depth of focus, light scatter and mirror glare. Images of humanoid and contrast detail phantoms were acquired using the prototype EPID and were compared with those obtained using conventional and high contrast portal film and a commercial EPID. A theoretical analysis was also carried out for a proposed full field of view system using a large area, thinned CCD camera and a 12.7 mm thick CsI(TI) crystal. Results indicate that this proposed design could achieve DQE(0) levels up to 11%, due to its order of magnitude higher QDE compared to phosphor screen-metal plate based EPID designs, as well as significantly higher light collection compared to conventional TV camera based systems.

The clinical evaluation of vein contrast enhancement

A vein contrast enhancer (VCE) has been constructed to make vein access easier by capturing an infrared image of veins, enhancing the contrast using software, and projecting the vein image back onto the skin. The VCE also uses software to align the projected image with the vein to 0.06 mm. Clinical evaluation of earlier monitor-based vein enhancement test systems has demonstrated the clinical utility of the infrared imaging technology used in the VCE.

Adaptive median filter algorithm to remove impulse noise in x-ray and CT images and speckle in ultrasound images

An adaptive median filter algorithm to remove impulse noise in x-ray images and speckle in ultrasound images is presented. The ordinary median filter tends to distort or lose fine details in an image. Also, a significant amount of the original information in the image is altered. The proposed algorithm considers the local variability over the entire image to ensure that the fine details are preserved and more than 90 percent of the original information is retained. The robustness of the algorithm is demonstrated by applying it to images from different modalities like diagnostic x-ray, CT, portal imaging and ultrasound.

Commercialization of vein contrast enhancement

An ongoing clinical study of an experimental infrared (IR) device, the Vein Contrast Enhancer (VCE) that visualizes surface veins for medical access, indicates that a commercial device with the performance of the existing VCE would have significant clinical utility for even a very skilled phlebotomist. A proof-of-principle prototype VCE device has now been designed and constructed that captures IR images of surface veins with a commercial CCD camera, transfers the images to a PC for real-time software image processing to enhance the vein contrast, and projects the enhanced images back onto the skin with a modified commercial LCD projector. The camera and projector are mounted on precision slides allowing for precise mechanical alignment of the two optical axes and for measuring the effects of axes misalignment. Precision alignment of the captured and projected images over the entire field-of-view is accomplished electronically by software adjustments of the translation, scaling, and rotation of the enhanced images before they are projected back onto the skin. This proof-of-principle prototype will be clinically tested and the experience gained will lead to the development of a commercial device, OnTarget!, that is compact, easy to use, and will visualize accessible veins in almost all subjects needing venipuncture.

Preliminary performance characteristics of a dual-energy KCD

A kinestatic charge detector (KCD) with segmented signal-collection fingers was constructed to evaluate the dual-energy x-ray imaging performance of a KCD. The front segments of the KCD signal-collectors produce a digital low-energy image and the back segments produce a digital high-energy image. A gap between the front and back signal-collectors is used as a filter to increase the separation between the mean energies absorbed in the front and back segments. Preliminary measurements have been performed on the dual-energy KCD to determine its dual-energy imaging characteristics. The KCD output signal has been measured as a function of depth in the chamber. The ion drift velocity, modulation transfer function (MTF), detective quantum efficiency (DQE) and Wiener spectrum have been determined for both the front (low-energy) and back (high-energy) signal detection regions of the KCD.

Clinical applications of a dual-energy KCD

We have investigated possible clinical applications of a Kinestatic Charge Detector (KCD) for dual-energy x-ray imaging. The KCD is a good candidate as a detector for dual-energy radiography, because it is a digital detector with a high detective quantum efficiency, good spatial resolution and good scatter rejection. Computer simulations have been performed to design and optimize dual-energy KCDs for specific clinical applications. The clinical applications that have been investigated for dual-energy KCD imaging are chest radiography, mammography and osteoporosis. Experimental data have also been taken with a small research dual-energy KCD.

A variable resolution x-ray detector for computed tomography: II. Imaging theory and performance.

A computed tomography (CT) imaging technique called variable resolution x-ray (VRX) detection provides variable image resolution ranging from that of clinical body scanning (1 cy/mm) to that of microscopy (100 cy/mm). In this paper, an experimental VRX CT scanner based on a rotating subject table and an angulated storage phosphor screen detector is described and tested. The measured projection resolution of the scanner is > or = 20 lp/mm. Using this scanner, 4.8-s CT scans are made of specimens of human extremities and of in vivo hamsters. In addition, the systems projected spatial resolution is calculated to exceed 100 cy/mm for a future on-line CT scanner incorporating smaller focal spots (0.1 mm) than those currently used and a 1008-channel VRX detector with 0.6-mm cell spacing.