Scanning electron microscopy of otic capsule and calvarial bone ablated by a holmium-YAG laser

Abstract

Abstract. Scanning electron microscopy (SEM) was performed oll holmium-YAG laser ablated bone in order to study the surface morphology of the ablation crater. An otosurgical bone model of porcine otic capsule and calvarial cortical bone was used. Otic capsule bone is dense and homogeneous whereas cortical bone is porous. Both bone tissues were studied under fresh and dehydrated conditions to investigate the role of water in the ablation process. Laser irradiation time was varied from 5 to 60s. Laser flux was 85mJ pulse-~ at 4-Hz pulse repetition rate. Globular spheroids of melted bone material were noted in both wet and dried specimens for both tissues. Several of these globules ruptured yielding an SEM image which suggests a violent ejection process. SEMs of dry cortical bone demonstrated the presence of fibres which reflect the selective removal of inorganic surface bone constituents with preservation of subsurface residual collagen fibres. The ablation crater walls in wet tissues appear rougher and possibly reflect a more violent ablation process due to water vaporization causing expulsion of bone material. In contrast, the crater walls in dry tissue appear smoother.

Pattern of healing of calvarial bone in the rat following application of the erbium-YAG laser

“…A reduction of this magnitude could easily take the interaction near to, or below, the threshold for photoablation, in which case the en- ergy absorbed goes entirely into heating the tissue, and the formation of a carbon layer. Using the holmium-YAG laser, Wong et al [3] found a selective removal of inorganic bone constituents, leaving collagen fibres at the base of the ablation crater. In our experiments, however, the erbium-YAG laser caused selective removal of organic material in a narrow zone adjacent to the laser defect, leaving the surface covered by single and clustered microspheres.…”

“…Erbium-YAG lasers tend to produce narrower zones of damage in bone than holmium-YAG lasers in vitro [2]. The bone composition and state of hydration also appear to be important variables [3]. Calvarial bone in vivo is a composite of mineralized and unmineralized matrix, cells, vessels and marrow, the latter often being rich in lipid-laden adipocytes.…”

Time and Frequency Resolved XeCl Laser-Induced Mechanical Transients in Otic Capsule Bone

“…14,16 The animal was of slaughter age, approximately 21 wk old. The bone surrounding the structures of the inner ear is called endochondral bone and forms the otic capsule.…”

“…12 High-intensity short-lived acoustic signals may also result in noise-induced hearing loss. 13 In this study, we measured photoacoustic transients created by XeCl laser ablation of porcine otic capsule, 14 and examined their frequency characteristics to determine its suitability for inner ear surgery. The time-resolved results are compared to an analytic model derived from a solution to the thermal-elastic stress equation.…”

Holmium-YAG Laser ablation characteristics in calvarial lamellar and cortical bone: The role of water and tissue micro-architecture

“…The specific methods for tissue preparation and machining have been previously-described (29). Cortical and lameItar bone were haz d vested from the parietal and frontal bones of freshly sacrificed dom_estic pigs (Farmer John's Clougherty Packing Company, Vernon, California, USA).…”