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.
A proof-of-principle prototype Vein Contrast Enhancer (VCE) has 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 modified
commercial projector. The prototype uses software alignment to achieve alignment accuracy between the captured
infrared image and the projected visible image of better than 0.06 mm. Figure 1 shows the prototype demonstrated in our
laboratory.
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.
A clinical study is underway to compare an experimental infrared (IR) device, OnTarget OnTarget at LeBonheur Children's Medical Center, Methodist Healthcare, in Memphis, TN, while the adult study site is the clinical research center at Bowld Hospital, also in Memphis, TN. Early results on 35 pediatric and 25 adult subjects indicate that OnTarget years' experience in accessing veins in pediatric subjects, and that it could be very helpful to a phlebotomist with limited experience when accessing veins in both adult and pediatric subjects. The study uses monitor based OnTarget area of the patients anatomy enlarged and contrast enhanced on a LCD monitor. The phlebotomist can then compare the OnTarget or feel when examining a subject.
A clinical study has been initiated to compare an experimental IR device, the Vein Contrast Enhancer (VCE), with standard techniques for finding veins for venipuncture. The aims of this proposal are (1) to evaluate the performance of the VCE in a clinical setting, specifically by comparing its sensitivity of detection with existing vein-finding techniques used by experienced nurses or phlebotomists, (2) to study its usefulness in subjects who are obese, who have difficult venous access or thrombosed veins, or whose veins are not visible or difficult to palpate, and (3) to show that it performs as well on subjects with darkly pigmented skin as on subjects with lightly pigmented skin. The VCE will first be studied in adult subjects, and then in pediatric subjects.
A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This techniques uses a near IR light source and one or more IR sensitive CCD TV cameras to produce a contrast enhanced image of the subcutaneous veins. This video image of the veins is projected back onto the patient's skin using a n LCD video projector. The use of an IR transmitting filter in front of the video cameras prevents any positive feedback from the visible light from the video projector from causing instabilities in the projected image. The demonstration contrast enhancing illuminator has been tested on adults and children, both Caucasian and African-American, and it enhances veins quite well in all cases. The most difficult cases are those where significant deposits of subcutaneous fat are present which make the veins invisible under normal room illumination. Recent attempts to see through fat using different IR wavelength bands and both linearly and circularly polarized light were unsuccessful. The key to seeing through fat turns out to be a very diffuse source of RI light. Results on adult and pediatric subjects are shown with this new IR light source.
A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This technique uses a near infrared light source and one or more infrared sensitive CCD TV cameras to produce a contrast enhanced image of the subcutaneous veins. This video image of the veins is projected back onto the patient's skin using an LCD vein projector. The use of an infrared transmitting filter in front of the video cameras prevents any positive feedback from the visible light from the video projector from causing instabilities in the projected image. The demonstration contrast enhancing illuminator has been tested on adults, both Caucasian and African-American, and it enhances veins quite well in most cases. Preliminary studies on a 9 month old girl indicate promise for pediatric use.
In a previous paper, a portal imaging system was described that used a 101 mm diameter, 3 mm thick CsI (Tl) transparent scintillating screen coupled to a liquid-nitrogen-cooled slow- scan CCD-TV camera with a 40 mm f1.0 macro lens with a 5:1 demagnification. Meanwhile, improved images have been acquired using a 50 mm f1.1 macro lens with a 7:1 demagnification. These images were presented at an AAPM International Symposium on Electronic Portal Imaging in Detroit, MI, in May, 1997. Since the Detroit meeting, a 203 mm diameter, 13 mm thick CsI(Tl) crystal has been purchased from Bicron. This transparent screen has been used with a Nikkor 35 mm f1.4 lens to show the whole 203 mm circular field at 0.53 mm pixel size with the existing Astromed liquid nitrogen cooled CCD TV camera system. The geometry of the imaging system has been optimized to achieve high spatial resolution (1 lp/mm) in spite of the increased thickness of the screen. This increased thickness allows the high image quality achieved with the older screen at 72 MU to be maintained with the newer screen while reducing the dose to 1 MU. Images have been acquired with the new screen of lead bar patterns, low-contrast hole patterns in Lucite blocks, and anthropomorphic phantoms.
A method utilizing digital dual-energy substraction x-ray radiography for measuring calcium densities localized to the cortical and cancellous regions of bone cross sections is described. The method is proposed as a technique for studying calcium loss in femurs of rats used in experiments modeling the temporal of osteoporosis. The densitometry data obtained for a rat leg consists of six x-ray projection images acquired at 30 degree(s) angular intervals about the bone axis by an intensifying screen/CCD camera imaging system. Images of bone cross sections are reconstructed by application of a maximum entropy algorithm constrained by the six projection images. The observed density data are further discriminated into cortical, cancellous and external regions on the basis of reference levels found on image density histograms.
A liquid nitrogen cooled CCD TV camera from Astromed, Ltd., has been used for quantitative x-ray medical imaging. The CCD is coupled to a Gd2O3(Eu) transparent ceramic scintillator on loan from the Ceramics Division of the General Electric Research Laboratories with an 80 mm f 1.3 oscilloscope camera lens optimized for 2:1 demagnification. High-resolution single-energy x-ray images have been acquired of lead bar patterns, human heel bones, and human teeth. Dual-energy bone-mineral densitometry images have been acquired of the foot and the femur of a rat.
A method utilizing digital dual-energy subtraction X-ray radiography for measuring calcium densities localized to the cortical and cancellous regions of bone cross sections is described. The method is being used to study calcium loss in femurs of two differently treated groups of rats. In each experimental cohort, one group of rats is restrained from weightbearing on hind limbs by suspension from a tail harness. The other (control) group is allowed normal weightbearing on all limbs. The densitometry data for each rat leg consists of six X-ray projection images acquired at roughly equal angles about the bone axis by an intensifying screen/CCD camera imaging system. Images of bone cross sections are reconstructed by application of a maximum entropy algorithm constrained by the six projection images. The observed density data are further discriminated into cortical, cancellous and external regions on the basis of reference levels found on image density histograms.
A liquid nitrogen cooled CCD TV camera from Astromed, Ltd. has been used for quantitative X-ray medical imaging. The CCD camera is coupled to a Kodak Lanex Regular X-ray intensifying screen with a 5:1 macro lens for bone mineral densitometry of the femur of a rat for a study of the development of osteoporosis. As a feasibility study of the use of the CCD for mammography, a 2:1 macro lens has been used to couple the CCD to a clear CsI(Tl) crystal, 100 mm in diameter and 3 mm thick. The spatial resolution and quantum efficiency of the system is significantly improved by replacing the Lanex Regular screen with the CsI(Tl) crystal.
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