Injectable chondroplasty: Enzymatic reshaping of cartilage grafts.

OBJECTIVE/HYPOTHESIS: To develop an injection-based enzymatic technique that selectively softens cartilage tissue for reshaping cartilaginous structures in the head and neck. MATERIALS AND METHODS: Two groups were formed using fresh rabbit ears: (1) whole rabbit ear group; (2) composite graft group (2.5mm×3.0cm specimens sectioned from the central region of the pinna). Subperichondrial injections using three enzymes (hyaluronidase, pronase, and collagenase II) in sequence were performed for the experimental specimens from both groups. In the control specimens, phosphate buffered saline was injected in a similar fashion. The whole ear specimens were then photographed while held upright in the anatomical vertical position to evaluate for buckling, which corresponds to the integrity of the cartilage. In addition, backlight photography was performed for all specimens to further evaluate the effect of the enzymes, such that increased light intensity represents increased cartilage digestion. RESULTS: The application of the digestive enzymes resulted in marked reduction of cartilage tissue matrix resiliency, while preserving overlying skin layers. Enzymatically treated whole pinnae buckled at the site where enzymes were delivered. Backlit images revealed increased local light intensity at the regions of digestion. There was no obvious destruction of the overlying skin upon visual inspection. CONCLUSIONS: This study demonstrates the feasibility of injectable chondroplasty as a potential alternative method to conventional surgery for auricular cartilage reshaping. Sequential injection of hyaluronidase, pronase, and collagenase II into the subperichondrial space can be performed to digest and soften cartilage structure with minimal involvement of surrounding tissue. Future studies will need to include chondrocyte viability testing and optimization of delivery techniques.

Optimizing the Soft Tissue Triangle, Alar Margin Furrow, and Alar Ridge Aesthetics: Analysis and Use of the Articulate Alar Rim Graft.

The alar lobule, alar margin, and soft triangle facet are receiving more attention in the literature as critical elements to address both preoperatively and during rhinoplasty. We have found that the use of the articulated alar rim graft (AARG) corrects deficiencies in these areas as well as provides mechanical stability to the external valve. In this article, we describe indications for AARG, describe in detail the procedure for AARG placement, and highlight the transformation AARGs can achieve in two illustrated case studies.

Glomus jugulare tumours: a 15 year radiotherapy experience in South Australia.

Glomus jugulare tumours (GJT) are one of a family of benign hypervascular neoplasms that arise from chief cells of the paraganglionic tissue from the dome of the jugular bulb. Historically, these tumours have primarily been managed surgically but radiation is an alternative treatment modality. The purpose of this retrospective review was to determine the patient survival, tumour control, clinical control rates and long term toxicity of GJT treated with radiation in South Australia. Between 1996 and 30 June 2012, 15 patients with GJT (16 tumours) were managed with radiotherapy. Twelve patients were female and the median age was 62 years. Thirteen patients (87%) were treated with conventional external beam radiotherapy and two patients (13%) with stereotactic radiosurgery. The mean duration of follow-up was 4 years (range 1 month-15 years 4 months). The close-out date for survival analyses was 31 October 2012. Crude overall survival, tumour control, clinical control and long term grade >2 toxicity rates were 100%, 94% (15/16), 94% and 7% (1/16), respectively. The Kaplan-Meier 5 and 10 year clinical and tumour control rates were both 93% (95% confidence interval: 61-99%). Radiation is an effective treatment modality for GJT. With comparable patient survival, arguably improved tumour and clinical control rates relative to surgery, minimal toxicity and ongoing advances in radiotherapy technologies, radiation should be strongly considered for the primary management of GJT.

No direct role for A1/A2 adenosine receptor activation to reflex cutaneous vasodilatation during whole-body heat stress in humans.

AIM: The precise mechanisms underlying reflex cutaneous vasodilatation during hyperthermia remain unresolved. The purpose of this study was to investigate a potential contribution of adenosine A1/A2 receptor activation to reflex cutaneous vasodilatation. METHODS: Eight subjects were equipped with four microdialysis fibres on the left forearm, and each fibre was randomly assigned one of four treatments: (1) lactated Ringer's (control); (2) 4 mm of the non-selective A1/A2 adenosine receptor antagonist theophylline; (3) 10 mm L-NAME to inhibit nitric oxide (NO) synthase; and (4) combined 4 mm theophylline and 10 mm L-NAME. Laser-Doppler flowmetry (LDF) was used as an index of skin blood flow, and blood pressure was measured beat-by-beat via photoplethysmography and verified via brachial auscultation. Whole-body heat stress to raise oral temperature 0.8 °C above baseline was induced via water-perused suits. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure and normalized to maximal (%CVC max) via infusion of 28 mm nitroprusside and local heating to 43 °C. RESULTS: There was no difference between control (65 ± 5%CVC max) and theophylline (63 ± 5%CVC max) sites. L-NAME (44 ± 4%CVC max) and theophylline + L-NAME (32 ± 3%CVC max) sites were significantly attenuated compared to both control and theophylline only sites (P<0.05), and combined theophylline + L-NAME sites were significantly reduced compared to L-NAME only sites (P<0.05). CONCLUSION: These data suggest A1/A2 adenosine receptor activation does not directly contribute to cutaneous active vasodilatation; however, a role for A1/A2 adenosine receptor activation is unmasked when NO synthase is inhibited.

Laryngeal epithelial thickness: a comparison between optical coherence tomography and histology.

OBJECTIVES: Optical coherence tomography, an imaging modality using near-infrared light, produces cross-sectional tissue images with a lateral pixel resolution of 10 microm. However, normative data is first needed on epithelial thickness for lesion characterisation, and, to date, little exists. The purpose of our study is to measure normal laryngeal epithelial thickness by in vivo optical coherence tomography, and compare these values to those obtained from fixed ex-vivo laryngectomy specimens. DESIGN AND SETTING: Prospective at a single medical center in California, United States. PARTICIPANTS: A total of 116 patients undergoing operative endoscopy. MAIN OUTCOME MEASURES: Optical coherence tomography images of clinically normal laryngeal subsites were selected. Calibrated measurements of epithelial thickness at various laryngeal subsites were recorded. Measurements of epithelial thickness from corresponding areas were obtained using optical micrometry on histologically normal regions of 15 total laryngectomy specimens. Descriptive statistics were performed. RESULTS: Mean epithelial optical coherence tomography thicknesses were: true vocal cords (81 microm), false vocal cords (78 microm), subglottis (61 microm), aryepiglottic folds (111 microm), laryngeal epiglottis (116 microm) and lingual epiglottis (170 microm). Epithelial thicknesses in fixed tissues were: true vocal cords (103 microm), false vocal cords (79 microm), aryepiglottic folds (205 microm) subglottis (61 microm), laryngeal epiglottis (38 microm) and lingual epiglottis (130 microm). CONCLUSIONS: Optical coherence tomography does not have the artifacts associated with conventional histologic techniques. The inevitable development of office-based optical coherence tomography devices will increase the precision of laryngeal measurements and contribute to the clinical application of this technology in diagnosing laryngeal disease.

Measurement of the elastic modulus of porcine septal cartilage specimens following Nd: YAG laser treatment.

Laser cartilage reshaping is a temperature-dependent process that results in stress relaxation with subsequent formation of a new and stable specimen geometry. The objective of this study was to quantitatively measure changes in the elastic moduli of porcine cartilage following laser heating. The elastic modulus of porcine nasal septal cartilage specimen (25 x 5 x 2 mm) was measured before and after Nd: YAG laser (lambda=1.32 Irvinem, 21.22 W/cm2) irradiation and following rehydration in saline solution. Specimens were secured in a single beam cantilever configuration and displaced using a calibrated thin beam load cell attached to a motorised micropositioner. Elastic modulus was calculated using elastic beam theory. Measurements were recorded before and immediately after laser heating, and following rehydration in saline solution (40 minutes, 25 degrees C). Specimens heated in saline (100 degrees C and then re-hydrated) were used as controls to determine the effect of total thermal denaturation. The calculated moduli before and after irradiation were 4.86 +/- .145 MPa and 1.166 +/- .055 MPa respectively. Following rehydration in saline, the modulus returned to near-baseline values (5.119 +/- .163 MPa). In contrast, elasticity remained lower in specimens boiled and re-hydrated (3.25 +/- .130 MPa). These findings suggest that cartilage matrix does not undergo complete thermal denaturation during laser reshaping, given the return in tissue properties with rehydration.

Shape retention in porcine-septal cartilage following Nd:YAG (lambda = 1.32 microm) laser-mediated reshaping.

BACKGROUND AND OBJECTIVE: Photothermal heating of mechanically deformed cartilage accelerates stress relaxation and results in sustained shape change. In this study, shape retention was measured in Nd:YAG laser reshaped porcine septal cartilage. MATERIALS AND METHODS: Specimens were laser reshaped either 4 (Group I) or 28 hours (Group II) following extraction from the crania. Specimens were bent into approximately semicircular shapes and irradiated half way between the endpoints of the semicircle. Resultant bend angle was calculated based on linear measurements. Shape retention was calculated by comparing resultant curvature with pre-irradiation measurements. RESULTS: Mechanical deformation alone resulted in initial bend angles varying from 188 degrees to 229 degrees. Resultant bend angles varied from 84 degrees to 194 degrees corresponding to shape retention varying from 58 to 75%. Non-irradiated cartilage retained less than 46% of the original bend. Shape retention was greater in Group II, compared to Group I. In Group I, no cephalocranial difference in shape retention was observed, though in Group II greater shape retention was observed in rostral specimens. CONCLUSION: While laser heating does significantly reshape cartilage, clinical use of this technology will require "overbending" of the cartilage graft to compensate for this memory effect. The degree of overbending is likely to vary with cartilage type and location.

Laser-mediated cartilage reshaping with feedback-controlled cryogen spray cooling: biophysical properties and viability.

BACKGROUND AND OBJECTIVE: Recent studies have indicated that chondrocyte viability decreases with prolonged or repeated laser irradiation. To optimize laser-mediated cartilage reshaping, the heating process must be finely controlled. In this study, we use high-power Nd:YAG laser irradiation (lambda = 1.32 microm) combined with cryogen spray cooling (CSC) in an attempt to reshape porcine septal cartilage while enhancing chondrocyte viability. STUDY DESIGN/MATERIALS AND METHODS: Chondrocyte viability was determined after high-power (50 W/cm2) Nd:YAG-mediated cartilage reshaping with and without cryogen spray cooling (CSC) and correlated with dynamic measurements of tissue optical and thermal properties. RESULTS: After 1.5 to 2.0 seconds of laser exposure, characteristic changes in diffuse reflectance (indicating the onset of accelerated stress relaxation) was observed in both laser only and laser with CSC specimens. After 2 seconds of laser exposure, specimens in both groups retained the curved shape for up to 14 days. After one laser exposure, chondrocyte viability was 94.35 +/- 6.1% with CSC and 68.77 +/- 20.1% (P < 0.05) without CSC. After two laser exposures, a similar trend was observed with CSC (70.18 +/- 16.44%) opposed to without CSC (28 +/- 45%; P < 0.05). CONCLUSION: CSC during high-power laser irradiation allows rapid heating while minimizing extreme front surface temperature elevations and axial thermal gradients. Laser irradiation with CSC can be used to effectively reshape cartilage tissue with the additional advantage of increasing chondrocyte viability.

The porcine and lagomorph septal cartilages: models for tissue engineering and morphologic cartilage research.

Interest in reconstruction and modification of the facial cartilaginous frameworks using advanced technology and instrumentation is growing rapidly. Despite this maturing interest, no animal model has been established to provide morphologic cartilage tissue with similar characteristics to human septum in suitable quantities. The objective of this study was to characterize porcine and lagomorph (rabbit) nasal septal cartilage tissue. Both models share great similarity with their human counterpart and provide a low-cost, high-volume, and easily obtained source of bulk cartilage tissue. We present a technique for harvesting intact septal cartilages from these species, and characterize select cellular, metabolic, and physical properties using pulse-chase radiolabeling, flow cytometry, and mechanical analysis. Our selective evaluation of key tissue properties establishes these species as appropriate animal models for nasal septal cartilaginous surgery.

Theramal, mechanical, optical, and morphologic changes in bovine nucleus pulposus induced by Nd:YAG (lambda = 1.32 microm) laser irradiation.

UNLABELLED: BACKGROUND AND OBJECTIVE To examine the biophysical effects of photothermal heating on herniated intervertebral discs during laser decompression surgery. STUDY DESIGN/MATERIALS AND METHODS: Ex vivo bovine nucleus pulposus specimens were irradiated with a Nd: YAG laser (lambda = 1.32 microm, 100 seconds exposure time, 9-31 W/cm(2), 4.8 mm spot diameter), whereas changes in tissue thermal, mechanical, and optical properties were monitored by using, respectively, infrared radiometry, tissue tension measurements, and diffuse reflectance from a HeNe probe laser. Morphologic changes and mass reduction were monitored by recording shape changes on video and weighing specimens before and after laser exposure. RESULTS: At power densities below 20 W/cm(2), evaporation of water and specimen volume reduction (shrinking) were consistently observed on video during irradiation. In contrast, above 20 W/cm(2), vapor bubbles formed within the specimen matrix and subsequently ruptured (releasing heated vapors). When radiometric surface temperature approaches approximately 60 to 70 degrees C (denaturation threshold for tissue), tissue tension begins to increase, which is consistent with observations of specimen length reduction. The onset of this change in tissue tension is also reflected in characteristic alterations in diffuse reflectance. With cessation of laser irradiation, a sustained increase in tissue tension is observed, which is consistent with changes in specimen length and volume. Higher laser power results in a faster heating rate and subsequently an accelerated tension change. Specimen mass reduction increased with irradiance from 19 to 72% of the initial mass for 9--31 W/cm(2), respectively. Irradiated specimens did not return to their original shape after immersion in saline (48 hours) in contrast to air-dried specimens (24 hours), which returned to their original shape and size. CONCLUSION: These observations suggest that photothermal heating results in irreversible matrix alteration causing shape change and volume reduction (observed on video and evidenced by the increase in tissue tension) taking place at approximately 65 degrees C. Inasmuch as high laser power results in vapor bubble formation and specimen tearing, the heating process must be controlled. Diffuse reflectance measurements provide a noncontact, highly sensitive means to monitor dynamically changes in tension of nucleus purposus.

Laser-assisted hair transplantation: histologic comparison between CO2 and Ho:YAG lasers.

BACKGROUND: Various laser wavelengths and devices have been advocated for use in the creation of recipient channels during hair transplant surgery, including flash-scanned CO2, Ho:YAG (lambda = 2.12 microm), and Er:YAG (lambda = 2.94 microm). OBJECTIVE: To determine the tissue injury caused by flash-scanned CO2 and pulsed Ho:YAG lasers during the creation of hair transplant recipient channels and to assess the efficacy of the Ho:YAG laser. METHODS: Recipient channels were created in vivo in human scalp tissue using both lasers, and were excised and prepared for histologic examination. Optical micrometry of tissue sections was used to assess thermal injury. RESULTS: The Ho:YAG laser created jagged, irregular-shaped channels with larger zones of thermal injury (superficial deepithelialization, thermal necrosis, and thermal damage). In contrast, the CO2 laser produced well-defined cylindrically shaped channels free of cellular debris with minimal epithelial disruption and significantly less lateral thermal injury. CONCLUSION: Given that the Ho:YAG produced larger regions of thermal injury and recipient channels that were unacceptable for graft, the CO2 laser remains the better choice for the creation of recipient channels during hair transplant surgery. However, ongoing research will be necessary to determine the optimal laser wavelength and/or devices for this procedure.

Angioresistance of thermally modified cartilage grafts in the chick chorioallantoic membrane model.

BACKGROUND: The chick chorioallantoic membrane (CAM) model allows direct observation of vascularization acutely in explanted or cultured tissues in an immunologically isolated environment. In vivo, angioinvasion of the tissue matrix does not occur in viable cartilage tissue, whereas denatured or nonviable grafts are readily vascularized and/or resorbed. OBJECTIVE: To determine, using the CAM model, whether angioinvasion of thermally altered cartilage explants occurs acutely. MATERIALS AND METHODS: Porcine septal cartilage specimens were removed from freshly killed animals and divided into 3 groups (n = 10): an untreated control group, a group in which cartilage was boiled in isotonic sodium chloride solution (normal saline) for 1 hour, and a laser-irradiated group (Nd:YAG, lambda = 1.32 microm, 30.8 W/cm2, irradiation time = 10 seconds). Tissue specimens were then washed in antibiotic solutions, cut into small cubes (approximately 1.5 mm3), placed on the surface of 30 CAMs (7 days after fertilization), and allowed to incubate for an additional 7 days. After incubation, the membranes and specimens were fixed in situ with formaldehyde and then photographed using a dissection microscope. RESULTS: Examination with a dissecting microscope showed no obvious vascular invasion of the cartilage or loss of gross tissue integrity in any of the 3 experimental groups, although all specimens were completely enveloped by the CAM vascular network. No vascular invasion of the tissue matrix was observed histologically. CONCLUSION: These experiments demonstrate that cartilage specimens remain acutely resistant to angioinvasion or metabolism by the immunologically immature CAM whether native unmodified tissue, completely denatured (boiled), or thermally modified following laser irradiation.

Optical and thermal properties of nasal septal cartilage.

BACKGROUNDS AND OBJECTIVES: The aim of the study was to measure the spectral dependence of optical absorption and reduced scattering coefficients and thermal conductivity and diffusivity of porcine nasal septal cartilage. Values of optical and thermal properties determined in this study may aid in determining laser dosimetry and allow selection of an optical source wavelength for noninvasive diagnostics for laser-assisted reshaping of cartilage. MATERIALS AND METHODS: The diffuse reflectance and transmittance of ex vivo porcine nasal septal cartilage were measured in the 400- to 1,400-nm spectral range by using a spectrophotometer. The reflectance and transmittance data were analyzed by using an inverse adding-doubling algorithm to obtain the absorption (mu(a)) and reduced scattering (mu(a)') coefficients. A multichannel thermal probe controller system and infrared imaging radiometer methods were applied to measure the thermal properties of cartilage. The multichannel thermal probe controller system was used as an invasive technique to measure thermal conductivity and diffusivity of cartilage at three temperatures (27, 37, 50 degrees C). An infrared imaging radiometer was used as a noninvasive method to measure the thermal diffusivity of cartilage by using a CO(2) laser source (lambda = 10.6 microm) and an infrared focal plane array (IR-FPA) camera. RESULTS: The optical absorption peaks at 980 nm and 1,180 nm in cartilage were observed and corresponded to known absorption bands of water. The determined reduced scattering coefficient gradually decreased at longer wavelengths. The thermal conductivity values of cartilage measured by using an invasive probe at 27, 37, and 50 degrees C were 4.78, 5.18, and 5.76 mW/cm degrees C, respectively. The corresponding thermal diffusivity values were 1.28, 1.31, and 1.40x 10(-3) cm(2)/sec. Because no statistically significant difference in thermal diffusivity values with increasing temperature is found, the average thermal diffusivity is 1.32 x 10(-3) cm(2)/sec. The numerical estimate for thermal diffusivity obtained from infrared radiometry measurements was 1.38 x 10(-3) cm(2)/sec. CONCLUSION: Values of the spectral dependence of the optical absorption and reduced scattering coefficients, and thermal conductivity and diffusivity of cartilage were measured. The invasive and noninvasive diffusivity measurements were consistent and concluded that the infrared imaging radiometric technique has an advantage to determine thermal properties, because damage to the cartilage sample may be avoided. The measured values of absorption and reduced scattering coefficients can be used for predicting the optical fluence distribution in cartilage and determining optical source wavelengths for the laser-assisted cartilage reshaping studies. The thermal conductivity and diffusivity values can play role in understanding thermal-dependent phenomenon in cartilage during laser irradiation and determining laser dosimetry for the laser-assisted cartilage reshaping studies.

Measurement of Acoustic Transients During Pulsed Holmium:YAG Laser Ablation of Cadaveric Human Temporal Bone.

Pulsed infrared (IR) and ultraviolet (UV) lasers have been suggested for use in middle ear surgery due to potential fiberoptic delivery, decreased thermal trauma and precise ablation characteristics. Although attention has been focused on the thermal and photoacoustic events that occur during pulsed laser ablation of hard tissue, there are few studies which evaluate the acoustic energy generated from these devices from an audiological standpoint. In this study, the mastoid cavities of cadaveric human temporal bones were irradiated with a holmium: yttrium aluminium garnet (Ho:YAG) laser (λ=2.12 µm) using the following parameters: 5, 10, and 15 Hz pulse repetition rate and 1, 2, 4, 6, 8, and 10 W average power. During ablation, acoustic measurements were made using a sound level meter positioned 5 cm away from the target site. With each set of laser parameters, the sound intensity exceeded 85 dB (dBA scale). Peak intensities of 125 dB were measured, and a saturation effect noted above 4 W or 500 mJ/pulse. The clinical significance of these findings is discussed and the acoustical aspects of middle ear function and noise trauma are reviewed.

Prevalence of external auditory canal exostoses in surfers.

OBJECTIVE: To determine (1) the prevalence of external auditory exostoses in a population of surfers and (2) the relationship between the length of time spent surfing and the prevalence, severity, and location of the exostoses. DESIGN: Cross-sectional epidemiological study. SETTING: General community. PATIENTS: Three hundred seven avid surfers (93.5% males and 6.5% females; age distributions: 11.2% were < or =20, 67.9% were 21 to 40, 17.5% were 41 to 50, and 3.3% were >50 years). MAIN OUTCOME MEASURES: Questionnaires focusing on surfing habits (number of years, geographic region, and number of days per year of surfing) were correlated with otoscopic findings. A simple grading system was devised, based on the degree of external auditory canal stenosis. Grades of normal, mild, moderate, and severe corresponded to 100%, 99% to 66%, 65% to 33%, and less than 33% effective patent surface area, respectively. RESULTS: There was a 73.5% overall prevalence of external auditory exostoses and a 19.2% overall prevalence of osteomas in the group studied. Of 441 ears with exostoses, 54.2% were mild, 23.6% were moderate, and 22.2% were severe. Of individuals who had surfed for 10 years or less, 44.7% had normal ear canals and only 6% had severely obstructed auditory canals. In comparison, in the group that had surfed for longer than 20 years, only 9.1% had normal auditory canals and 16.2% were severely affected. Of surfers with no exostoses, 61.1% had surfed for 10 years or less. In contrast, of surfers with severe exostoses, 82.4% had surfed for more than 10 years. Finally, the lesions seemed to affect all external auditory canal quadrants equally. CONCLUSION: A positive association exists between the amount of time individuals spend surfing and the presence and severity of exostoses of the external auditory canal.

Mirror-focused handpiece for laser-assisted uvulopalatoplasty for the treatment of snoring and sleep apnea.

We describe how a novel mirror-based laser handpiece device allows for the pinpoint coincidence of aiming and surgical beams during uvulopalatoplasty and other laser ablation procedures.

Feedback-controlled laser-mediated cartilage reshaping.

OBJECTIVE: To demonstrate feedback-controlled laser-mediated cartilage reshaping using dynamic measurements of tissue optical properties and radiometric surface temperatures. DESIGN: Flat cartilage specimens were reshaped into curved configurations using a feedback-controlled laser device. MATERIALS: Fresh porcine nasal septum, stripped of perichondrium and cut into uniform strips (25 x 10 x 1.5-2.1 mm) with a custom guillotine microtome. INTERVENTIONS: Cartilage specimens secured in a cylindrical reshaping jig (2.5 cm in diameter) and irradiated with an Nd:YAG laser (lambda = 1.32 microns, 25 W/cm2, 50-Hz pulse repetition rate). During laser irradiation, radiometric surface temperature was measured along with changes in forward-scattered light from a diode probe laser (lambda = 650 nm, 5 mW), using a lock-in detection technique. Sequential irradiation of the specimen outer surface was made (3 laser passes). Characteristic changes in tissue temperature and light-scattering signals were used to terminate laser irradiation. RESULTS: Effective reshaping was accomplished for both thin (1.5-mm) and thick (2.1-mm) specimens. Following reshaping, specimens were stored in saline solution at 4 degrees C for 21 days. No return to the original flat configuration was noted during this period. CONCLUSIONS: The prototype device effectively reshapes flat native porcine cartilage into curve configurations. The use of optical and thermal signals provides effective feedback control for optimizing the reshaping process.

XeCl laser surgery of the vocal cords: a histologic comparison with CO2 laser in a porcine model.

Fresh cadaveric pig larynxes were ablated with a CO2 (lambda = 10.6 microm) and a XeCl excimer (lambda = 308 nm) laser. Histologic comparison of the ablation craters created by the two lasers was performed, and ablation crater depth and marginal tissue damage were measured. Crater depth for both laser treatments is correlated with energy deposition and exposure time. The CO2 laser creates three times more nonspecific, marginal tissue damage than the XeCl laser at the ranges of total energy and exposure times used. This study demonstrates the potential of the XeCl laser as an alternative to the CO2 laser in microlaryngeal surgery.

Surface temperature distributions in carbon dioxide, argon, and KTP (Nd:YAG) laser ablated otic capsule and calvarial bone.

HYPOTHESIS: The spatial and temporal surface temperature distribution was measured after laser irradiation in fresh porcine otic capsule and calvarial bone tissue using an HgCdTe (mercury-cadmium-tellurium) infrared camera. BACKGROUND: Carbon dioxide (CO2) (lambda = 10.6 mm), argon (lambda = 514 nm), and Potassium-Titanyl-Phosphate Neodynium: Yttrium-Aluminum-Garnet (KTP[Nd:YAG]) (lambda = 532 nm) lasers are used for stapes surgery and in the treatment of chronic ear disease. Despite extensive clinical use, little is known about the thermal perturbations in otic capsule calcified tissues and what are safe energy parameters for laser use. METHODS: A microspot manipulator, lens, and microfiber were used for continuous wave (CW) and super-pulse (SP) CO2, argon, and KTP(Nd:YAG) lasers, respectively. Peak temperatures after ablation were measured simultaneously along with the full-width--half-maximum of the thermal disturbance and fitted to a Gaussian distribution. The cooling time for the hot spot to return to ambient temperature also was recorded. RESULTS: Temperature changes with CW CO2 irradiation were markedly elevated relative to SP mode and also required longer to cool. The KTP and argon-treated bone were irradiated in the presence and absence of an initiator (black ink): minimal surface temperature elevation was recorded in the absence of an initiator. Further, no surface modification was observed. In contrast, the addition of an initiator resulted in marked temperature elevations and significant surface carbonization with these two visible wavelength lasers. Cooling times varied from 10-40 seconds. No consistent relation to the measured thermal values and tissue microarchitecture was observed. CONCLUSIONS: The measured cooling times and Gaussian distribution of surface temperatures serve as empiric guidelines for minimizing thermal injury to critical structures during laser surgery in the middle ear.

Thermal imaging of the temporal bone in CO2 laser surgery: an experimental model.

The unique properties of lasers create an enormous potential for specific treatment of chronic ear disease. Despite the widespread acceptance and use of the laser, however, a complete understanding of the time- and space-dependent temperature distribution in otic capsule bone immediately after pulsed laser exposure has not been elucidated. Using a liquid nitrogen-cooled mercury-cadmium telluride infrared detector, the temperature distribution in human cadaveric otic capsule bone was determined immediately after pulsed (100 msec) carbon dioxide laser exposure (0.3 to 4.0 W; 200 microm spot diameter). The time- and space-dependent temperature increases and thermal diffusion were determined as a function of the laser power density and were found to vary linearly.