Biomedical subjects

L Reinisch

Publications and source records attributed to L Reinisch.

At least 19 recordsLinked to original sources

PubMed2000

Wound healing and collagen thermal damage in 7.5-microsec pulsed CO(2) laser skin incisions.

BACKGROUND AND OBJECTIVE: Wound-healing delays caused by lateral thermal damage to tissue remain a drawback of CO(2) surgical lasers. This study compares the thermal damage and wound-healing properties of a 7.5-micros pulsed CO(2) laser with scalpel and continuous wave (CW) CO(2) laser incisions. STUDY DESIGN/MATERIALS AND METHODS: We created incisions on the dorsal pelts of rats with a 7.5-micros pulsed CO(2) laser at 5-, 10-, or 15-Hz repetition rate, a conventional CW laser, or scalpel. Animals were euthanized at postoperative days 3, 7, 14, 21, and 80. Tissue was harvested and analyzed histologically and for wound tensile strength. In addition, tissue was harvested acutely and analyzed for acute thermal injury lateral to the incisions. RESULTS: Incisions made with the pulsed laser had significantly higher tensile strength and histologic rankings than did CW laser incisions at days 3-21, producing 118 microm of thermal damage to tissue as compared with 333 microm for CW laser. Pulsed laser incisions were not statistically different than scalpel incisions at days 3-14 of healing. Mathematical modeling showed the pulsed laser to produce a wound healing delay of 1.0 day by tensiometry and 1.9 days by histology, compared with 3.2 days by tensiometry and 6.0 days by histology for CW laser. There were no significant differences in wound healing when the pulsed laser was used at repetition rates of 5-15 Hz. CONCLUSIONS: Using a 7.5-micros pulse duration, CO(2) laser incisions healed at a rate similar to scalpel incisions and reduced the wound-healing delay seen with typical surgical CO(2) lasers.

Animals↗

PubMed2000

Effects of thermal conducting media on the skin surface during laser irradiation.

OBJECTIVES: To investigate the effects of thermally conductive, optically transparent media placed on skin during treatment with the flashlamp excited dye laser (FEDL). The use of higher energy densities to treat persistent cutaneous vascular lesions may result in a decrease in the number of treatment sessions. However, increased fluences can cause complications of scarring, hyperpigmentation, infection, skin texture changes, or hypopigmentation. The thermally conductive media should assist in dissipating surface thermal energy and thereby protect the skin from the complications. STUDY DESIGN: This was a prospective laboratory study using an animal model. The results were verified in a prospective, pilot, human-use trial. METHODS: The threshold for acute skin damage and measurements of the thermal transients were made using a rabbit model. The threshold for purpura was noted with and without the use of a sapphire as a thermal conductor. The thermal transients were measured with small thermocouples placed subcutaneously. On a human subject, purpura intensities were photographed and measured using computer morphometrics after treatment with the FEDL and skin surface protection with air, glass, sapphire, and diamond as conductive media. RESULTS: With the interposition of the sapphire thermal conductor during the FEDL treatment, excessive temperature increases of the epidermis were prevented during the laser pulse compared with glass and controls. Both sapphire and diamond resulted in decreased purpuric intensities with the applications of equivalent fluences. Wound recovery time for the purpura was decreased by approximately half a day when any of the surface conductors were used. CONCLUSIONS: The decreased transient temperature and decrease in purpura seen with the use of sapphire and diamond protecting the epidermis during treatment with the FEDL should result in fewer untoward effects during treatment of vascular lesions and facilitate their management.

Adult↗

PubMed2000

Comparative histology and vibration of the vocal folds: implications for experimental studies in microlaryngeal surgery.

OBJECTIVES/HYPOTHESIS: To determine the most suitable animal model for experimental studies on vocal fold surgery and function by a histological comparison of the microflap surgical plane and laryngeal videostroboscopy (LVS) in different species of animals. A second goal was to determine how the layered vocal fold structure in humans and three different animal species affects surgical dissection within the lamina propria. STUDY DESIGN: Prospective laboratory. METHODS: Three larynges each from dogs, monkeys, and pigs were compared with three ex vivo human larynges. Microflap surgery was performed on one vocal fold from each larynx. Both the operated and nonoperated vocal folds were examined histologically using stains specific for elastin, mature collagen, and ground substance. Based on the histological results, LVS was performed on two dogs and two pigs after first performing a tracheotomy for ventilation and airflow through the glottis. Arytenoid adduction sutures were placed to facilitate vocal fold adduction. RESULTS: The distributions of the collagen and elastin fibers were found to differ among the species with concentrations varying within species. Unlike the human vocal fold, which has a higher elastin concentration in the deeper layers of the lamina propria, both the pig and the dog had a thin band of elastin concentrated just deep to the basement membrane zone in the superficial layer. Just deep to this thin band, the collagen and the elastin were less concentrated. The monkey vocal fold had a very thin mucosal layer with less elastin throughout the mucosa. The microflap dissections in each of the dog, pig, and human vocal folds were similar, being located within that portion of the superficial lamina propria where the elastin and mature collagen are less concentrated. The microflap plane in the monkey vocal fold was more deeply located near the vocalis fibers. Despite the differences in elastin concentration, the microflap plane in both the dog and the pig was found to be similar to that in humans. The dog anatomy was much more suitable for microsuspension laryngoscopy and stroboscopic examination. The dog vocal folds vibrated in a similar fashion to human vocal folds with mucosal waves and vertical phase differences, features not seen in the pig vocal folds. CONCLUSIONS: Based on both the histological and stroboscopic results, the dog was believed to be a more suitable animal model for studies on vocal fold surgery, acknowledging that no animal's laryngeal anatomy is identical to that of the human. The dog LVS model presented allows for longitudinal laryngeal studies requiring repeated examinations at multiple time periods with histological correlation applied at sacrifice.

Animals↗

PubMed2000

Noninvasive fluorescent identification of bacteria causing acute otitis media in a chinchilla model.

OBJECTIVES: To evaluate a noninvasive method of bacterial identification via fluorescence spectroscopy in the setting of acute otitis media in a chinchilla model. STUDY DESIGN: Prospective. METHODS: For each chinchilla, transbullar inoculation with Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus was performed bilaterally and clinical infection was determined by otoscopy. An optical fiber coupled to a spectrofluorometer allowed for the delivery of an excitation wavelength to the inflamed tympanic membrane and the acquisition of the resulting emission signal. Sequential emission spectra obtained over a range of excitation wavelengths were assembled by a computer algorithm, and a single, three-dimensional plot was created for each test ear. Similarly, plots from the healthy external auditory canal (EAC) were also recorded. Twelve animals were used to establish a library of four reference plots representing the three bacteria and the EAC. Of the 24 ears available for study, 10 were excluded from analysis because of lack of clinical infection or presence of tympanic membrane perforation with purulent drainage. From four additional animals, four samples from ears infected with the above bacteria and three samples of the EAC served as unknowns. The unknown plots were analyzed by an investigator blinded to their identity. RESULTS: Using a multiple correlation of the unknown to the reference plots, seven of seven samples were correctly identified. CONCLUSIONS: We were able to establish a prototype method for the noninvasive identification of a limited library of pathogens in a chinchilla model of acute otitis media.

Acute Disease↗

PubMed1999

Free electron laser infrared wavelength specificity for cutaneous contraction.

BACKGROUND AND OBJECTIVE: Short pulsed and scanned CO(2) lasers that target water molecules are currently used for cutaneous resurfacing. These CO(2) resurfacing lasers produce acute cutaneous contraction, which can be quantitated as a measure of the laser's effect. We postulated that targeting the vibrational and rotational modes of proteins with specific infrared laser wavelengths might be more effective at inducing cutaneous contraction than the CO(2) resurfacing lasers. STUDY DESIGN/MATERIALS AND METHODS: The Vanderbilt University Free Electron Laser (FEL) was used at wavelengths between 6.0-8.6 microm. The cutaneous contraction and histologic thermal damage observed was compared to that seen with a scanned CO(2) resurfacing laser. RESULTS: Peaks of cutaneous contraction at 7.2-7.4 and 7.6-7.7 microm were found, which were three-fold more efficient at producing cutaneous contraction than the 10.6 microm CO(2) laser. The 7.2 microm wavelength is associated with the CH bend of C-CH(3), 7.4 microm to the CH bend of O=C-CH(3), 7.6 microm to the C-C-C stretch, and 7.7 microm to the amide III (C-N-H) absorption band for proteins. Using light microscopy, an approximately 40 microm denaturation zone of dermal collagen was found at all FEL wavelengths tested, regardless of the effectiveness of cutaneous contraction. CONCLUSION: The mechanism of action of these infrared wavelengths on cutaneous contraction is unknown, but appears to be independent of the amount of collagen denatured as observed by light microscopy. Infrared lasers such as the FEL that target vibrational and rotational modes of proteins therefore hold promise for cutaneous application at selected wavelengths.

Collagen↗

PubMed1999

Eyelid resurfacing.

BACKGROUND AND OBJECTIVE: Laser resurfacing of eyelids was examined in a series of experiments designed to measure beam parameters, surface temperatures, ablation characteristics, thermal damage, tissue responses and clinical outcomes. These data were collected for the purpose of developing a logical basis for clinical dosimetry. STUDY DESIGN: All experiments were conducted with similar short-pulse CO(2) lasers (TruPulse, Albuquerque, NM) where the beam had been carefully characterized and calibrated. The chronological sequence examined begins with the photophysical laser/tissue interactions during the first few microsec of irradiation and ends with an evaluation of the efficacy of wrinkle reduction nine months after treatment. RESULTS: Eyelid tissue removed by the first and second passes consisted mostly of epidermis with about 38 microm of thermal damage into the papillary dermis. Erythema resolved within four weeks and most patients experienced 70-100% wrinkle reduction by nine months. CONCLUSION: A layer of contracted dermal scar tissue that replaced the thermally challenged zone in the dermis is identified as the substrate for wrinkle reduction. The data support the following dosimetry for periorbital wrinkle reduction: One pass 4-6 J/cm(2) (350-500 mJ into a 3 x 3 mm spot). A second treatment after 9-12 months may be more beneficial than a second pass.

Animals↗

PubMed1999

Comparison of cortical bone ablations by using infrared laser wavelengths 2.9 to 9.2 microm.

BACKGROUND AND OBJECTIVE: The purpose of this study was to compare the ablation of cortical bone at wavelengths across the near and midinfrared region. STUDY DESIGN/MATERIALS AND METHODS: An free electron laser generating 4-micros macropulses at specific wavelengths between 2.9 and 9.2 microm was used to ablate cortical bone. The same pulse intensity, repetition rate, radiant exposure, number of pulses, and delivery was used for each wavelength. Tissue removal, collateral thermal injury, and morphologic characteristics of the ablation sites were measured by light and scanning electron microscopy, and compared with the infrared absorption characteristics of cortical bone. RESULTS: Within the parameters used, bone ablation was found to be wavelength dependent. Incisions were deepest where protein has strong absorption, and were most shallow where mineral is a strong absorber. No char was observed on ablation surfaces where 3.0, and 5.9-6.45 microm wavelengths were used. CONCLUSIONS: The use of wavelengths in the 6.1-microm amide I to 6.45-microm amide II region, with the pulse characteristics described, were the most efficient for cutting cortical bone and produced less collateral thermal injury than cutting with a surgical bone saw. This study confirms previous observations that the ablation mechanism below plasma threshold is consistent with an explosive process driven by internal vaporization of water in a confined space and demonstrates that ablation is enhanced by using wavelengths that target the protein matrix of cortical bone.

Absorption↗

PubMed1999

Osteoplastic flap for obliteration of the frontal sinus: five years' experience.

The objective of this retrospective study was to evaluate the osteoplastic flap (OPF) for the obliteration of the frontal sinus in this current era of endoscopic management of frontal sinus disease. A review of consecutive OPF procedures (n = 43) performed by the senior author (J.A.D.) from 1992 to 1997 was carried out. Data were gathered regarding chief symptom, medical history, previous sinus surgery, endoscopic findings in the office and at surgery, CT scan findings, and follow-up results (mean 19.4 months). Previous endoscopic management of frontal sinus disease had failed in 24% of patients; 97% had eventual resolution of frontal sinusitis with OPF. After OPF, 63% also had improvement or resolution of disease in other paranasal sinuses. Statistically significant, positive correlations (P < 0.05) were noted between the resolution of frontal sinusitis and improved or resolved pain, as well as the resolution of frontal sinusitis and improved or resolved infections in other paranasal sinuses. In 1998 OPF remains the standard for treating frontal sinus disease refractory to other methods. OPF can decrease the pain associated with frontal sinus infections and has a positive impact on inflammatory disease in other paranasal sinuses.

Adult↗

PubMed1999

Preservation of function and histologic appearance in the injured glottis with topical mitomycin-C.

OBJECTIVE: To evaluate the functional and histological effects of a single application of topical mitomycin-C after laser injury in the posterior canine glottis. STUDY DESIGN: A prospective, randomized study of 16 canines. METHODS: A supersaturated (1%) solution of topical mitomycin-C was applied to a unilateral, laser-induced injury near the cricoarytenoid joint in eight dogs. The mitomycin-soaked pledget was placed immediately after induction of the injury and was left in contact with exposed cartilage for 3 minutes. The opposite side was not injured to provide an internal control. In eight additional dogs, the same laser injury was allowed to heal untreated. After 6 weeks, the animals were sacrificed and their larynges harvested. Arytenoid adduction sutures were placed bilaterally, and the force required to bring the vocal folds to midline was measured for each side using tensiometry. Gross and microscopic histological analysis was performed. Statistical analysis was accomplished using a two-tailed Student t test of unpaired samples, and the Wilcoxon Signed Rank Test where appropriate. RESULTS: The mitomycin-C treated larynges demonstrated improved cricoarytenoid joint mobility (P = .007), decreased granulation tissue development (P = .03), and complete prevention of secondary "vocal granuloma" formation (P = .0004) when compared with eight dogs with identical laser injuries allowed to heal untreated. No complications were noted. CONCLUSIONS: This study demonstrates functional preservation and improved histological appearance of the injured glottis after a single treatment with topical mitomycin-C. Potential applications of these findings include prophylactic use of topical mitomycin-C on glottic insults that commonly progress from granulation tissue formation to scarring and decreased vocal fold function.

Administration, Topical↗

PubMed1999

Analysis of a critical pathway in osteoplastic flap for frontal sinus obliteration.

OBJECTIVES: A critical pathway was applied to patients undergoing osteoplastic flap (OPF) for frontal sinus obliteration to determine whether efficiency could be improved. STUDY DESIGN: A retrospective review of consecutive OPF procedures (n = 51) performed between 1992 and July 1997 was conducted. METHODS: The patient groups were subdivided into those who underwent OPF alone and those who had endoscopic sinus procedures performed in addition to OPF. Comparisons were made between the precritical pathway and post-critical pathway groups, specifically noting operative time, total operating room (OR) time, estimated blood loss (EBL), length of hospital stay, and costs. We used a critical pathway that was developed for endoscopic sinus procedures at our institution through a multidisciplinary team approach. Preoperative evaluation and testing, intraoperative equipment and medications, and postoperative care including follow-up clinic visits were all standardized. An unpaired, two-tailed Student t test was used to evaluate the data. RESULTS: Statistically significant (P<.05) reductions in operative times, total OR time, EBL, and length of hospital stay were observed in the post-critical pathway group who underwent endoscopic sinus procedures as well as OPF. Costs to the OR were reduced 29% and 15% for OPF and for OPF with endoscopic surgery, respectively. Patient costs were reduced 5% and 4% in these groups, respectively. CONCLUSIONS: With implementation of effective critical pathways, significant decreases in length of stay are seen, and cost reductions can be realized through the improved efficiency, shortened OR times, and decreases in redundancy of ordering materials.

Bone Transplantation↗

PubMed1999

Histologic and physiologic effects of electrocautery, CO2 laser, and radiofrequency injury in the porcine soft palate.

OBJECTIVES: This study was undertaken to compare the effects of electrosurgery, CO2 laser, and radiofrequency on the histological structure and physiological properties of the soft palate. These surgical techniques are used for stiffening and reducing the soft palate in the treatment of snoring and mild sleep apnea. STUDY DESIGN: Fifteen pigs were divided into five groups. METHODS: group 1 underwent electrosurgery incision of the lateral soft palate and excision of the uvula. Group 2 underwent the same procedure with the CO2 laser. Group 3 underwent CO2 laser ablation of the midline soft palate mucosa. Group 4 underwent radiofrequency volumetric reduction. Group 5 served as control. After 5 weeks the animals were sacrificed. Soft palate mucosa and muscle were subjected to tensiometric and histological analysis. Statistical analysis of tensiometric measurements was done with an ANOVA using a Bonferroni-Dunn correction. RESULTS: Tensiometric measurements of the mucosa were increased over normal controls when the surgical technique resulted in mucosal disruption. When the surgical technique resulted in primarily muscle disruption (radiofrequency) tensiometric measurements of the muscle were increased over controls. Histological analysis demonstrated normal remucosalization in all specimens, with fibrosis increased at the site of the primary injury. CONCLUSIONS: The type of injury produced resulted in identifiable patterns of physiological and histological change. Understanding of the effects of available surgical techniques is important in guiding our choice of surgical approach and allows us to better counsel our patients on their surgical options.

Animals↗

PubMed1999

Radiofrequency tissue ablation of the inferior turbinates using a thermocouple feedback electrode.

OBJECTIVE: The objective of this clinical trial was to assess the safety and efficacy of radiofrequency (RF) tissue ablation of the inferior turbinates in the treatment of nasal obstruction using an RF energy delivery system with a thermocouple feedback electrode. METHODS: A prospective, nonrandomized study of 11 patients (mean age, 47+/-12 y) with chronic nasal obstruction was conducted. Using patient-based visual analogue scales (VAS), symptom parameters were assessed. These included degree of nasal obstruction, frequency of nasal obstruction, and pain. Physician assessment of nasal obstruction was also collected by the principal investigator. Follow-up was conducted at 24 hours, 1 week, 4 weeks, 8 weeks, and 1 year. ANOVA was carried out to determine statistically significant differences in the data. Data were fit to a regression model, and confidence intervals were determined from a 95% confidence level. RESULTS: In patient-assessed degree of nasal obstruction, statistical significance was seen among baseline and 4 weeks, 8 weeks, and 1 year (P<.001, P<.0001, and P<.0008, respectively). There was no difference between 8 weeks and 1 year (P<.15). The data appeared to follow an exponential decay to a constant value. The pretreatment baseline average degree of obstruction was 7.5+/-0.5 on a scale of 0 to 10. The degree of obstruction after 8 weeks was 2.7+/-0.6. The time constant for this change was 21 days to reach 90% of the final value. At 1 year, degree of obstruction was 3.3+/-0.7. For frequency of nasal obstruction, statistical significance was seen among baseline and 4 weeks, 8 weeks, and 1 year (P<.0001, P<.0001, and P<.0001, respectively). There was no difference between 8 weeks and 1 year (P<.15). The pretreatment baseline average frequency of obstruction was 7.8+/-0.5. The remaining frequency of obstruction after 8 weeks was 2.9+/-0.6. The time constant was 18 days. At 1 year, frequency of obstruction was 3.3+/-0.6. Physician assessment of nasal obstruction revealed statistical significance among baseline and 4 weeks, and baseline and 8 weeks (P<.0055 and P<.0056, respectively). There was no difference between 4 weeks and 8 weeks (P<.24). The average initial obstruction was 83%+/-4%. The remaining obstruction after 8 weeks was 58% +/-5%. The time constant was 14 days. Mild pain was reported by 55% of patients during the procedure; the remaining 45% reported no pain. Only one patient required pain medication consisting of acetaminophen after the procedure. There were no significant complications. CONCLUSIONS: Degree and frequency of nasal obstruction, as reported by patients, decreased following RF tissue ablation of the inferior turbinates. This improvement in symptoms was still evident after 1 year (P<.001). Physician assessment of obstruction also correlated with patient reports for the initial 8-week study period. The procedure was safe and well tolerated. Thermocouples within the active electrode provided additional feedback to the operating surgeon allowing the use of relatively lower tissue temperatures, power, and energy as compared with traditional techniques. These results support the need for continued research to evaluate this modality as a treatment for chronic nasal obstruction.

Adult↗

PubMed1999

Ablation of Teflon granulomas in the canine larynx with the free-electron laser.

This study develops a canine model for the treatment of laryngeal Teflon granulomas and demonstrates endoscopic ablation using the free-electron laser (FEL) set at a wavelength of 8.5 microm. Laryngeal Teflon granulomas may cause dysphonia and airway obstruction, and they are difficult to remove. The infrared absorption spectrum of Teflon reveals a strong absorption peak centered at 8.5 microm. In this study, 12 dogs had the right vocal cord injected with Teflon paste. Two months later, Teflon granuloma formation was confirmed histologically. Laser incisions into the granulomas were performed at 3 different wavelengths: 7.4 microm (FEL), 8.5 microm (FEL), and 10.6 microm (carbon dioxide laser). Histopathologic analysis was performed at 1 week and 6 weeks after the laser incisions. The FEL at the 8.5-microm wavelength was found to optimally ablate the Teflon granulomas, but the granulomas persisted in the specimens treated with 7.4 microm (FEL) and 10.6 microm (carbon dioxide laser).

Animals↗

PubMed1999

Histomorphometric and laryngeal videostroboscopic analysis of the effects of corticosteroids on microflap healing in the dog larynx.

The histologic and functional effects of unilateral, layered corticosteroids on lateral microflap healing in 15 dogs were analyzed. Histologic sections of steroid-treated vocal folds (VFs) were studied with computer morphometry to examine differences in the tissue healing response. Paired analysis revealed increases in the inflammatory infiltrate around the microflap in the steroid-treated VFs at 2, 4, and 6 weeks (6.3%, 30.6%, and 34.9%, all with p < .02). The neovascular response in the steroid-treated VFs was less at 2 weeks (-20.9%, p < .005) but greater at 4 and 6 weeks (16.3% and 4.3%, p < .005). To better characterize the effect of steroids on the healing process, a normal, time-dependent distribution was applied to the histologic data and demonstrated a delay in the steroid-treated VF tissue response of 12 days for the inflammatory infiltrate and 21 days for the neovascular response. Qualitative and quantitative analysis of in vivo laryngeal videostroboscopy (LVS) samples taken preoperatively and at sacrifice could not identify significant differences in appearance, amplitude, mucosal wave, or suppleness between the 2 VFs. Therefore, although corticosteroids cause a delay in wound healing, LVS does not discern differences in microflap characteristics between healing steroid-treated and control VFs at 2, 4, or 6 weeks. If steroids are used, the surgeon should account for a probable delay in wound healing, but should not expect an overall difference in functional outcome.

Administration, Topical↗

PubMed1999

Inhibition of subglottic stenosis with mitomycin-C in the canine model.

The objective of this randomized, prospective study was to study the efficacy of topical mitomycin-C in the inhibition of subglottic stenosis in a canine model. Subglottic stenosis was elicited with the carbon dioxide laser in 10 mongrel dogs. Radial incision and serial dilation of the subglottic airway were then carried out. The animals were randomized to receive a topical solution of 1% mitomycin-C to the dilated area for a 5-minute duration or no further treatment. Weekly direct microlaryngoscopy and photodocumentation were performed during the 6-week study. Airway distress developed in 4 of the 5 control dogs, requiring early sacrifice, while all treatment group animals survived the duration of the study (p < or = .006). Morphometric analysis of the subglottic photographs confirmed a greater than 100% increase in the percentage of relative airway at sacrifice in the treatment group (p < or = .049). A statistically significant (p < or = .015) decrease in collagen formation in the subglottic scar of dogs treated with topical mitomycin-C was documented. Mitomycin-C favorably altered the clinical progression of subglottic stenosis, improved quantified airway patency, and reduced the amount of subglottic collagen formation in the canine model.

Administration, Topical↗

PubMed1999

Effective laser ablation of bone based on the absorption characteristics of water and proteins.

BACKGROUND: Collateral thermal damage and residual char formation have severely limited the use of conventional lasers in the surgical preparation of bony tissue. Thermal damage from lasers can be minimized by selecting a wavelength that is strongly absorbed and by reducing the laser pulse duration. In contrast to the fixed wavelengths and microsecond pulse intervals of conventional lasers, the Vanderbilt free electron laser (FEL) can be set at wavelengths ranging from 2.1 to 9.8 microm, and the pulse duration can be reduced to a series of 1 to 2 picosecond (ps) micropulses delivered in succession over intervals of 4 microsecond macropulses. The purpose of this study was to compare the morphologic and chemical changes induced in the near-surface region of bone following exposure to the FEL at 3.0, 6.1, and 6.45 microm wavelengths. The selected wavelengths coincide with the vibrational modes of proteins and water within bone. METHODS: Under general anesthesia, laser incisions were made in the tibias of 14 skeletally mature rabbits. Laser parameters included 22.5+/-2.5 mJ/pulse delivered in individual 4 microsecond macropulses at a repetition rate of 30 Hz, focused to 200 microm and 500 microm spot sizes. Laser incisions were made using a computer-assisted surgical program, and control incisions were created with a bone saw. Rabbits were euthanized after the final incision, tibias recovered, and non-decalcified specimens processed for light microscopy. Separate samples were prepared for FTIR (Fourier transform infrared) photoacoustic spectroscopic analysis. RESULTS: The light microscopy sections of the ablation defects created at the differing wavelengths showed similar features, i.e., 2 zones of collateral damage, a zone generally < 10 mm of extensive thermal damage, and a wider zone of empty lacunae. In comparing treated and untreated surfaces, the spectral differences were limited to a relative decrease in intensity of the amide II and III absorption peaks in all laser-treated surfaces. CONCLUSIONS: Spectroscopic and histologic results indicated minimal thermal damage to bone ablated at 3.0, 6.1, and 6.45 microm wavelengths using the FEL (Fourier transform infrared) at the specified parameters. The FTIR photoacoustic spectroscopic results suggest that the char layer is limited to an area less than approximately 6 microm from the surface.

Absorption↗

PubMed1998

Optimizing fluence and debridement effects on cutaneous resurfacing carbon dioxide laser surgery.

OBJECTIVE: To develop methods to compare carbon dioxide (CO2) resurfacing lasers, fluence, and debridement effects on tissue shrinkage and histological thermal denaturation. DESIGN: In vitro human or in vivo porcine skin samples received up to 5 passes with scanner or short-pulsed CO2 resurfacing lasers. Fluences ranging from 2.19 to 17.58 J/cm2 (scanner) and 1.11 to 5.56 J/cm2 (short pulsed) were used to determine each laser's threshold energy for clinical effect. Variable amounts of debridement were also studied. MAIN OUTCOME MEASURES: Tissue shrinkage was evaluated by using digital photography to measure linear distance change of the treated tissue. Tissue histological studies were evaluated using quantitative computer image analysis. RESULTS: Fluence-independent in vitro tissue shrinkage was seen with the scanned and short-pulsed lasers above threshold fluence levels of 5.9 and 2.5 J/cm2, respectively. Histologically, fluence-independent thermal depths of damage of 77 microns (scanner) and 25 microns (pulsed) were observed. Aggressive debridement of the tissue increased the shrinkage per pass of the laser, and decreased the fluence required for the threshold effect. In vivo experiments confirmed the in vitro results, although the in vivo threshold fluence level was slightly higher and the shrinkage obtained was slightly lower per pass. CONCLUSIONS: Our methods allow comparison of different resurfacing lasers' acute effects. We found equivalent laser tissue effects using lower fluences than those currently accepted clinically. This suggests that the morbidity associated with CO2 laser resurfacing may be minimized by lowering levels of tissue input energy and controlling for tissue debridement.

Animals↗

PubMed1998

Interstitial Nd:YAG photocoagulation for vascular malformations and hemangiomas in childhood.

BACKGROUND: Vascular malformations and cavernous hemangiomas are common in childhood. Although cavernous hemangiomas may resolve spontaneously, aggressive intervention is required when their growth could damage vital adjacent structures, such as the orbit, nose, or tongue. OBJECTIVE: To evaluate the efficacy of interstitial Nd:YAG photocoagulation as an adjunct to intralesional and systemic corticosteroids for treatment of hemangiomas and vascular malformations that had failed to respond to other therapies. DESIGN: Prospective, nonrandomized trial. SETTING: Two referral practices of facial plastic and reconstructive surgery in tertiary care, academic medical centers. PATIENTS: Ten consecutive pediatric patients with either hemangioma or vascular malformation of the head and neck. INTERVENTION: Laser photocoagulation with an interstitial technique. The Nd:YAG fiber was introduced into the lesion via a 14-gauge angiocatheter needle, and the laser fiber was advanced as coagulation proceeded within the tissue. MAIN OUTCOME MEASURES: Decrease in the area of the target lesion, amount of energy applied, and number of treatments required to achieve reduction in size. RESULTS: Long-term follow-up demonstrated regression of the lesion in all 10 patients with good cosmetic results. The range of reduction in size was 20% to 98%. No reexpansion of the lesions was noted after a mean follow-up of 13 months. CONCLUSIONS: Interstitial photocoagulation of hemangiomas and vascular malformations is an effective treatment for carefully selected patients. When properly applied, this technique can achieve reduction in the size of these lesions without compromising cosmesis.

Adolescent↗