Showing papers by "Scott A. Prahl published in 1995"
22 May 1995
TL;DR: It is found that while the dye can be driven a few millimeters into the gels in both the axial and radial directions, the penetration was less than 500 micrometers when the gel surface remained macroscopically undamaged.
Abstract: Photoacoustic drug delivery is a technique for delivering drugs to localized areas by timing laser-induced pressure transients to coincide with a bolus of drug. This study explores the effects of target material, laser energy, absorption coefficient, fiber size, repetition rate, and number of pulses on the spatial distribution of delivered drug. A microsecond flash-lamp pumped dye laser delivered 30-100 mJ pulses through optical fibers with diameters of 300-1000 micrometers . Vapor bubbles were created 1-5 mm above clear gelatin targets submerged in mineral oil containing a hydrophobic dye (D&C Red#17). The absorption coefficient of the oil-dye solution was varied from 50-300 cm-1. Spatially unconfined geometry was investigated. We have found that while the dye can be driven a few millimeters into the gels in both the axial and radial directions, the penetration was less than 500 micrometers when the gel surface remained macroscopically undamaged. Increasing the distance between the fiber tip and target, or decreasing the pulse energy reduced the extend of the delivery.
15 citations
12 May 1995
TL;DR: An elastin-based biomaterial that elicits minimal foreign body reaction to the intimal surface of porcine aorta is welded with a pulsed diode laser thermally confines heating to stained portion of tissue, minimizing adjacent tissue damage.
Abstract: Laser tissue welding is a sutureless method of wound closure that has been used successfully in nerve, skin, and arterial anastomoses We welded an elastin-based biomaterial that elicits minimal foreign body reaction to the intimal surface of porcine aorta The aorta was stained with indocyanine green dye to efficiently absorb the 808 nm diode laser light Laser welding with a pulsed diode laser thermally confines heating to stained portion of tissue, minimizing adjacent tissue damage Laser welds of stained aorta to biomaterial were attempted by sandwiching the samples between glass slides and applying pressure ranging from 4 - 20 N/cm 2 for 5 ms pulse durations and 83 mJ/mm 2 radiant exposure Welds were successful for pressure above 5 N/cm 2 Transmission measurements of stained aorta were made using radiant exposures of 6 - 129 mJ/mm 2 using pulse durations of 05 - 5 ms Transmission increases and reaches a maximum of 80 - 85% with successive pulses for radiant exposure greater than 26 mJ/mm 2 for a spot size of 9 mm 2 and 13 mJ/mm 2 for a spot size of 36 mm 2
14 citations
22 May 1995
TL;DR: In this article, a 1 microsecond (s) pulsed dye laser (504 nm) was used to ablate a gelatin-based thrombus model containing an absorbing dye under water.
Abstract: The efficiency of laser ablation of thrombus depends on spot size, pulse energy and repetition rate. A 1 microsecond(s) pulsed dye laser (504 nm) was used to ablate a gelatin-based thrombus model containing an absorbing dye under water. The gelatin was confined in 3 mm inner diameter tubes and pulse energies of 25-100 mJ were delivered via 300, 600, and 1000 micrometers core diameter fibers. The experiments were conducted at pulse repetition rates of 3 Hz and 10 Hz. The amount of gelatin removed was measured using a spectrophotometric method and ablation efficiency was defined as mass removed per pulse per unit energy. Flash photography was used to visualize the ablation process in 1 cm cuvettes. Results: More material was removed using bigger fibers in the 3 mm tubes at similar pulse energies. The amount of gelatin removed per pulse increased linearly with pulse energy. There was no significant change in the amount removed at pulse repetition rates of 3 Hz and 10 Hz. In the 1 cm cuvettes, the ablation mass was roughly the same with both the 300 micrometers and 1000 micrometers fibers. Flash photography of the ablation process in 1 cm cuvettes showed that less than 1% of the laser energy went into formation of a vapor bubble. The mass removed increased roughly linearly with bubble energy. Conclusions: Ablation mass increases linearly with pulse energy, but does not have a direct relationship with radiant exposure. It is independent of the repetition rate under 10 Hz.
5 citations