S. L. Herr

Increased spatial resolution in transillumination using collimated light

In traditional transillumination of the breast (diaphanography), the abundance of diffuse light resulting from the use of extended noncollimated sources reduces the visibility of deep seated lesions. A prototype scanning imaging system has been developed to investigate the effectiveness of thin collimated light beams (1.5 mm cross section) synchronized with a similarly collimated detector to increase contrast in lesions normally lost due to the detection of diffuse light. The study demonstrates that detection of opaque 1.5 mm details is possible in phantoms simulating breast tissues 6 mm thick regardless of depth. This is about 10 times better than images obtained on the same samples using present transillumination methods. Furthermore, this study indicates that internal structures (lesions, cysts) in up to 12 mm thick excised breast sections can be visualized by exploiting their frequency-dependent attenuation. This is accomplished by inserting 50 nm interference filters in the input light path, which can be varied in a stepwise manner in the range of 400 nm to 1000 nm. These results demonstrate for the first time that images of lesion-bearing 1 cm or larger tissues can be obtained, thus opening promising possibilities for whole-breast imaging.

Increased spatial resolution for light images of tissues--especially for teeth

A new high resolution transillumination technique has been developed to detect small lesions in teeth and in tissues. It uses collimated, narrow light beams synchronized with a highly sensitive receiver to scan the sample. Extracted teeth and tissues have been examined with this technique. The teeth included a variety of conditions, some with caries, some previously restored, and others with metal pins inserted into them. The results show that a small carious lesion as small as 1 mm2 can be detected from either side of the tooth. Cysts and cancerous lesions in tissues were also detected. The new light imaging technique can find carious lesions better than dental x rays, however, the solution of mental pins inside a tooth is less than that of x rays. The technique is totally harmless to teeth and tissues and can be used as often as necessary even during any clinical procedure. The investigation shows that the resolution for carious lesions could be increased further to about 0.1 mm by incorporating presently available new semiconductor devices and that such a device could be designed for clinical oral use.

Vibrational structure in the infrared reflectance spectra of the high-temperature superconductor Bi2Sr2CaCu2O8

Abstract Pressed ceramic pellets of the high-temperature superconductor Bi 2 Sr 2 CaCu 2 O 8 ( T c = 85 K) were investigated by reflectance spectroscopy in the infrared and visible regions at several temperatures both below and above the superconducting transition. In the process of identifying and analyzing vibrational lines in these samples, two problems arise: diffuse scattering connected with the grainy surface and a non-conventional baseline caused by intense absorption of the electronic background present in the infrared region. After eliminating the effects due to these processes, the temperature dependence of the vibrational lines can be extracted. It is concluded that none of the lines behaves in an anomalous way, i.e., no vibration strongly coupled to the electronic system was found.

Investigation to expand the collimated transillumination method for improved identification and determination of the location of small details in very thick tissues

A collimated transillumination system has been developed for the detection of small lesions in thick tissues. The test object is raster scanned by a collimated light beam and a synchronous in-line post collimated receiver. The images are recorded either in analog form to a film using a light emitting diode, or stored digitally in a microcomputer and displayed by a 256 gray shade monitor. Tests show that the system can achieve high resolution in detecting small details in images of whole teeth, live mice, breast sections, and bones in the regular operating mode. The resolution can be increased by using a newly developed high resolution method and/or by digitizing the image. In addition, different types of details can be separated from each other by using different wavelengths of light.

Investigation of a light imaging system to detect small lesions in thick tissues

A light imaging system is being developed which can at this time detect and characterize small lesions on the surface and deep inside a tooth or tissue. It depends on the existence of light photons which can fully traverse a tooth in a straight path and therefore can make -- similar to x rays -- a clear shadow of a pathology on the receiver. To observe the very weak, transmitted, unscattered light rays a special patented system has been developed using collimated, narrow light beams and a highly sensitive, post collimated receiver which are rasterscanned over the entire sample. The image can be transferred in analog form to a film or observed after digitization on a 256 grayshade monitor. The light image can be observed in a regular or slower high sensitivity mode.

Study to increase the resolution and range of a light imaging system

Collimated transillumination is a technique based on the observation that some of photons from a laser beam can traverse an entire tooth, and other tissues in an apparent straight light path and therefore make a shadow of any pathology on the receiver similar to x-rays. To observe the very weak, transmitted, unscattered light rays a special patented system has been developed using collimated, narrow light beams and a highly sensitive, post collimated receiver which rasterscans the entire sample. The image is then transferred to a film. To increase the sensitivity a high resolution mode (HR) has been added.

Infrared spectra and the energy gap in thin film YBa2Cu3O7-delta

Interpretations of IR and millimeter wave measurements in superconductors are generally carried out in terms of the Mattis-Bardeen calculations, which apply either to the anomalous skin effect regime or to the dirty limit regime. In high temperature superconductors neither limit applies. Reflectance measurements on high quality, epitaxially-grown, laser-deposited films indicate that these samples are in the clean-limit, normal skin effect regime. Features that have been previously identified as the gap appear in both the superconducting and the normal-state spectra, although obscured by the free carrier absorption above Tc. Below Tc these features become more evident as the free carrier contribution condenses into a delta function at zero frequency.