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Biomedical subjects

F L Lizzi

Publications and source records attributed to F L Lizzi.

60 records · Page 4Linked to original sources
PubMedDate not supplied

Thermal model for ultrasonic treatment of glaucoma.

Focused ultrasound, at a frequency of 4.6 MHz, was used to create lesions of the sclera in the proptosed glaucomatous eye of the anesthetized albino rabbit, with the result that elevated intra-ocular pressures were reduced to normal levels. Initial trials on carefully selected glaucoma patients have also shown that pressure reductions can be produced with high-intensity ultrasound. A theoretical model was developed to compute the spatio-temporal features of temperature rises induced in the sclera during these treatments. Experimental data confirmed the accuracy of the model.

Animals↗
PubMedDate not supplied

Regression of uveal malignant melanomas following cobalt-60 plaque. Correlates between acoustic spectrum analysis and tumor regression.

Parameters derived from computer analysis of digital radio-frequency (rf) ultrasound scan data of untreated uveal malignant melanomas were examined for correlations with tumor regression following cobalt-60 plaque. Parameters included tumor height, normalized power spectrum and acoustic tissue type (ATT). Acoustic tissue type was based upon discriminant analysis of tumor power spectra, with spectra of tumors of known pathology serving as a model. Results showed ATT to be correlated with tumor regression during the first 18 months following treatment. Tumors with ATT associated with spindle cell malignant melanoma showed over twice the percentage reduction in height as those with ATT associated with mixed/epithelioid melanomas. Pre-treatment height was only weakly correlated with regression. Additionally, significant spectral changes were observed following treatment. Ultrasonic spectrum analysis thus provides a noninvasive tool for classification, prediction and monitoring of tumor response to cobalt-60 plaque.

Cobalt Radioisotopes↗
PubMedDate not supplied

Therapeutic ultrasound in the treatment of retinal detachment: clinical observations and light and electron microscopy.

Osmotically-induced retinal detachments were created in rabbit eyes and treated with therapeutic ultrasound. Control eyes showed spontaneous retinal reattachment after ten days (range, 8-10 days), while eyes treated with therapeutic ultrasound showed retinal reattachment in a shorter time (average, 4.5 days). Light and electron microscopy demonstrates at least three major differences in the ultrasound-treated eyes compared to the controls. These findings are evidence of an earlier retinal reattachment, a stronger chorioretinal adhesion, less damage and faster repair in the ultrasound-treated retina than in the control retina. This method of producing chorioretinal adhesions may have applications in certain types of retinal detachments where choroidal thickness or vitreous opacity preclude conventional cryopexy, diathermy or photocoagulation techniques.

Animals↗
PubMedDate not supplied

Correlation of microcirculation architecture with ultrasound backscatter parameters of uveal melanoma.

Ultrasound tissue characterization parameters of size and acoustic concentration can be used to sub-classify uveal melanoma and estimate the patient's risk of death. Histologically determined microcirculation patterns have also been found to sub-classify uveal melanoma and predict patient's risk of death. This study examines the spatial relationship between tumor features detected by the two techniques. Three dimensional ultrasound images that depict the size and relative concentration of scattering elements in uveal melanoma within a range of approximately 50-120 microns were compared with PAS (without hematoxylin) stained histological sections graded and localized according to tumor microvascular patterns. Both ultrasound parameter imaging and histopathology were accomplished by workers masked to the other procedure. In three of five patients vascular networks were identified histopathologically. The predominant ultrasound feature seen in the regions of the histologically identified networks were clusters of scatterers in the range of approximately 50-80 microns. In the two cases without a network vascular pattern, lower range scatterers dominated the tumor volume. All the cases could be distinguished by the size and distribution of contiguous spatial clusters of acoustic scatterers. Scatterer size features detected in three dimensional ultrasound parameter images can identify tumor regions containing a specific microvascular pattern. Ultrasound tissue characterization features used to sub-classify uveal melanoma may have a biophysical basis related to patterns of tumor microcirculation.

Blood Vessels↗