Biomedical subjects

A E Profio

Publications and source records attributed to A E Profio.

28 records · Page 2Linked to original sources

PubMed1975

Semiconductor camera for detection of small tumors.

Early detection of small tumors (approximately 3 mm) with only a moderate uptake ratio is often difficult because of poor statistics and a small signal-to-background ratio. The detection capability of a germanium semiconductor camera is analyzed to show that a very large number of counts is required even when the spatial resolution is matched to the size of the tumor. A potential enhancement of statistics using the tissue-scattered gamma rays is discussed based on the superior energy resolution of the semiconductor.

Gamma Rays↗

PubMedDate not supplied

Laser fluorescence bronchoscope for localization of occult lung tumors.

A system for imaging occult bronchogenic carcinoma by the fluorescence of previously-injected, tumor-specific compound hematoporphyrin-derivative has been assembled and successfully used to locate a tumor 1 mm thick. The violet excitation source is a krypton ion laser coupled to fused quartz fiber light conductor. An electrostatic image intensifier attached to a standard flexible fiberoptic bronchoscope provides a bright image even at relatively low irradiance. A red secondary filter rejects most reflected background and autofluorescence. Sensitivity and contrast capability of the system should permit detection of a tumor less than 0.1 mm thick.

Bronchoscopes↗

PubMedDate not supplied

Dosimetry considerations in phototherapy.

Dosimetry in phototherapy involves a determination of the energy absorbed per unit mass of tissue, corrected for the quantum yield in a photochemical reaction. The dose rate in photochemotherapy of cancer with hematoporphyrin derivative and visible light is related to the extinction coefficient, quantum yield for singlet oxygen production, concentration of sensitizer and energy flux density at depth. Data or methods of determining these quantities are presented. Calculations have been performed for the energy flux density at depth, as a function of the total attenuation coefficient and ratio of scattering coefficient to total attenuation coefficient, for isotropic scattering in slab geometry. For small absorption, these depth dose curves exhibit a maximum within the tissue followed by an exponential decrease.

Fluorescence↗

PubMedDate not supplied

Fluorescence bronchoscopy for localization of carcinoma in situ.

A fluorescence bronchoscope system has been developed for imaging lung tumors by fluorescence of a previously injected, tumor-specific agent hematoporphyrin derivative. Carcinoma in situ has been localized, but there are too many false positives and negatives. A new system has been implemented which allows rapid switching between viewing of fluorescence, and viewing of the same area under white light illumination as in conventional bronchoscopy. The excitation source is a violet krypton ion laser coupled to a fused quartz fiber light conductor, with a diverging microlens to spread the light uniformly. A third-generation, microchannel plate image intensifier amplifies the weak fluorescence for viewing and video display, recording, and analysis. A movable mirror and periscope bypasses the intensifier for normal color viewing and video display and recording, with the laser shutter closed and the white light shutter open. This facilitates accurate localization, comparison of the color and fluorescence images, and precise sampling during biopsy. The improved system should reduce the false positive rate due to biopsy sampling error, and together with the video analyzer should reduce indeterminate results.

Bronchoscopes↗

PubMedDate not supplied

Fluorometer for endoscopic diagnosis of tumors.

A filter fluorometer suitable for endoscopic applications has been developed for detection and characterization of superficial tumors by the fluorescence of a previously injected, tumor-specific agent, hematoporphyrin derivative. Fluorescence is excited by violet light conducted through a fiberoptic lightguide in the endoscope, and the fluorescence emission together with reflected violet are collected by another fiberoptic lightguide. The red fluorescence and violet are separated by a dichroic mirror and filter and detected in photomultiplier tubes. The ratio of the fluorescence signal to the reflected violet signal is proportional to the ratio of the fluorescence yield to the violet reflectivity but is insensitive to variations in distance, angle, and violet power. The instrument may be useful for localizing small tumors, and for quantitative measurements of the amount of hematoporphyrin derivative in the tumor, a requirement for accurate dosimetry in photoradiation therapy.

Animals↗

PubMedDate not supplied

Spectral transmittance and contrast in breast diaphanography.

Diaphanography is an imaging technique using transillumination with visible and near-infrared radiation, and a video camera, to diagnose breast disease, including cancer. Originally based on luminance contrast only, there is now interest in false-color multispectral imaging in selected spectral bands to improve tissue differentiation. Some success has been achieved, but the scientific basis for the results was unknown. This research is concerned with measurements of the diffuse transmittance of breast tissues as a function of wavelength in the 600-1060 nm range (and calculations of contrast with a one-dimensional diffusion theory model). Carcinoma and glandular tissues were found to have similar spectral transmittances with an increase in transmittance between 750 and 900 nm, and an absorption window around 960 nm. Adipose tissue showed a distinct transmittance minimum at 930 nm. In vivo measurement of an intact normal breast showed a minimum at about 825 nm, as yet unexplained. The transmittance data and reflectance data were used to derive the scattering and absorption coefficients. The diffusion length was also determined from radiance versus depth measurements. These coefficients were used for calculations of contrast in a one-dimensional slab model, with and without a layer of cancerous tissue positioned between two slabs of normal tissue.

Biophysical Phenomena↗

PubMedDate not supplied

Digital background subtraction for fluorescence imaging.

A method of enhancing contrast in fluorescence imaging has been devised, based on real-time digital subtraction of a background video image from a signal-plus-background video image. Color filters are used to differentiate signal from background. The technique has been applied to detection of small tumors labeled with the tumor specific fluorescent drug hematoporphyrin derivative.

Biophysical Phenomena↗

PubMedDate not supplied

A system for real time fluorescence imaging in color for tumor diagnosis.

Early tumors can be diagnosed by the fluorescence of an injected, tumor-specific agent such as dihematoporphyrin ether. However, brightness or intensity contrast is low because of the autofluorescence of tissue. Addition of color (hue) information aids in detection of tumors, and in elimination of false positives. Standard color video cameras are not sensitive enough to image the weak fluorescence. Thus an intensified monochrome video camera has been equipped with a synchronized color filter wheel, and the image displayed by multiplexing alternate lines to a red green blue (RGB) monitor.

Animals↗

PubMedDate not supplied

Contrast in diaphanography of the breast.

Diaphanography is an imaging technique used in diagnosis of breast disease including cancer. The breast is illuminated with low intensity light and the transmission pattern of red and near-infrared radiation is detected, amplified, reconstructed and displayed in a monitor. The instrumentation for diaphanography has evolved empirically, mostly through clinical practice, without a very clear understanding of the scientific basis of the technique. This research is concerned with investigating theoretically the dependence of the contrast produced by a lesion in a diaphanography image on the size, depth at which a tumor is located, photon energy, and photon angular flux distribution. Contrast calculations using the DOT computer code in a two-dimensional geometry showed that decreasing the size of a tumor by 50% decreases the contrast by a factor of 3 and 4 for 695- and 853-nm photons, respectively. Decreasing the size of the normal tissue where a tumor is imbedded by 25% (from 4 to 3 cm) does not change the contrast very much (less than 20%) for both 695- and 853-nm photons. The contrast for 950- and 695-nm photons is comparable while the values for 853-nm photons are smaller by a factor of 5 for similar cases. The contrast was also found to be dependent on the angle at which the diffuse light is detected after it transverses the host tissue, maximum contrast was found for 695- and 853-nm photons at about 55 degrees. For a detection angle of 77 degrees the contrast observed is 3X and 12X smaller for 695- and 853-nm photons, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Diseases↗

PubMedDate not supplied

Scientific basis of breast diaphanography.

Diaphanography, also known as transillumination, is a breast diagnostic technique based on differences in the diffuse transmittance of visible or near-infrared radiation. Previous papers by the authors reported on investigations of the effect of tumor size, depth at which the tumor is located, the thickness of the breast, and the effect of using photons of different wavelengths. The results from the study reported here indicate that absorption of light in hemoglobin is the basis for the luminance contrast, and shift in the infrared to red transmission ratio, in the diaphanographic image. Evidence is based on known extinction coefficients for oxyhemoglobin and deoxyhemoglobin as a function of wavelength, measurements of the transmitted spectrum in specimens, in vivo dual wavelength transillumination imaging of lesions containing different amounts of blood (bloody and clear cysts, hematomas, veins, fibroadenomas, and carcinomas), and comparison of preoperative diaphanographic images to blood vessel volumes measured by microscopic analysis of surgical specimens. Oxygenation affects the relative proportions of infrared and red light transmitted, but does not influence the diagnosis based on luminance contrast.

Breast Neoplasms↗