Amir M. Karamzadeh

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

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 (λ = 1.32 μm) combined with cryogen spray cooling (CSC) in an attempt to reshape porcine septal cartilage while enhancing chondrocyte viability.

A novel laryngoscope instrument stabilizer for operative microlaryngoscopy

OBJECTIVE: To evaluate and optimize the design of a removable and inexpensive internal stabilization device to reduce the effect of intention tremor during laryngeal microsurgery. STUDY DESIGN AND SETTING: In this laboratory investigation, stabilizers were designed and constructed to allow a nonobstructing view of the surgical field, permit simple insertion and removal, and accommodate microsurgical instruments. Prototype stabilizers were tested by using a Dedo laryngoscope, a measurement grid, and video recording equipment, which recorded instrument tremor within the magnified operative field for later analysis. Physicians also rated instrument stability, mobility, visualization, and ease of use on a survey form. RESULTS: Instrument tremor was reduced approximately 90%, with little obstruction of view of the surgical field. Instrument range of motion was reduced but improved rapidly as the stabilizer bar was moved further from the tip of the laryngoscope. CONCLUSIONS: Use of a stabilization device in the laryngoscope lumen reduces instrument tremor and has the potential to improve surgical performance during laryngeal microsurgery. EBM rating: B-3.

Aquatic Activities after Total Laryngectomy

OBJECTIVE: To assess the techniques used by patients who have undergone laryngectomies to enable them to participate in aquatic activities. STUDY DESIGN: Unstructured interviews. METHODS: The case histories of 4 patients who have returned to swimming and other aquatic activities after total laryngectomy were obtained by non-structured interviews emphasizing techniques used to swim, safety precautions taken, any accidents or near accidents, and perceived effect of aquatic activities on sense of well being and quality of life. RESULTS: All 4 of the interviewed subjects swim regularly using commercial breathing aids or manual tracheostomal occlusion. One of the four is a regular surfer, who uses a homemade breathing aid. All were active swimmers prior to the development of laryngeal cancer. A single aquatic-related accident was reported by 1 of the 4 swimmers. All subjects describe feeling an enhanced quality of life resulting from their participation in aquatic activities. CONCLUSION: Despite recommendations of most clinicians, a small number of highly motivated patients will return to aquatic activities after laryngectomy.

Photodynamic therapy on keloid fibroblasts in engineered keratinocyte-fibroblast co-culture

Abstract Objectives: Keloids are disfiguring proliferative scars that are a pathologic response to cutaneous trauma. An organotypic tissue culture system (the RAFT model) was used to investigate the feasibility of treating keloids using photodynamic therapy (PDT). The RAFT co-culture recreates skin by layering keratinocytes on top of fibroblasts embedded in a collagen matrix. PDT uses drugs that produce singlet oxygen in situ when irradiated by light and may lead to a number of effects in living tissues varying from the modulation of growth to apoptosis. Methods: Normal adult, neonatal, and keloid fibroblasts and keratinocytes were used to construct the RAFTs. Mature RAFTS were incubated with 5-ALA, a photosensitizer, and were laser-irradiated (635 nm) for energy delivery of 5 J/cm2, 10 J/cm2, or 20 J/cm2. RAFTS were examined 24 hours and 14 days later. Cell viability was determined using confocal imaging combined with live-dead fluorescent dyes. Multiphoton microscopy (MPM) imaged collagen structure and density. As RAFTs contracted over time, surface area was measured using optical micrometry daily. Results: At 20 J/cm2, near-total cell death was observed in all constructs. At 10 J/cm2 some cell viability was maintained, while at 5 J/cm2 cell viability was comparable to controls. After 14 days, cell viability in keloid and neonatal RAFTs was greater than that observed in normal adult RAFTs. Treated RAFTs contracted less over the 14-day period compared to controls. Contraction and collagen density were greatest in keloid and neonatal RAFTS. Conclusions: A PDT dosimetry range has been established that reduces tissue contraction and collagen synthesis while preserving cell viability.

A Cost–Benefit Analysis and Method of Creating High-Quality Posters for a Low Cost†‡

Objective To introduce the results of a cost–benefit analysis comparing an office‐based low‐cost technique for producing research posters versus conventional methods.

Angiogenic response in the chick chorioallantoic membrane model to laser-irradiated cartilage

Laser radiation can be used to reshape cartilage grafts via thermally mediated stress relaxation. While several studies have addressed the biophysical changes accompanying reshaping, cartilage viability following laser irradiation has not been extensively investigated. The objective of this study was to determine the extent of angioinvasion of irradiated cartilage explant placed onto the chick chorioallantoic membrane (CAM) model. Angioinvasion of the tissue matrix does not occur in viable cartilage tissue, whereas denatured tissue is readily vasculairzed and/or resorbed in vivo. Porcine septal cartilage specimens were removed from freshly sacrificed animals and divided into three protocols (n=10 each group) consisting of an untreated control, cartilage boiled in saline solution for one hour, and a laser irradiated group (Nd:YAG, λ=1.32 μm, 30.8 W/cm2, irradiation time = 10 sec). Following laser irradiation, tissue specimens were washed in antibiotic solution sand cut into small cubes (~1.5 mm3). The cartilage specimens were placed onto the surface of twenty CAMs, six of which, survived the entire 14 days incubation period. After incubation, the membranes and specimens were fixed in situ with formaldehyde, an then photographed using a dissection microscope. Cartilage specimens were prepared for histologic evaluation and stained with hematoxylin and eosin. Examination with a dissecting microscope showed no obvious vascular invasion of the cartilage or loss of gross tissue integrity in both the control and laser treated groups. In contrast, boiled specimens appeared to be partially or completely resorbed by the surrounding CAM vascular network. These gross findings were also confirmed by histological examination. In summary, our preliminary studies suggest that cartilage specimens treated using the present laser parameters remain resistant to angioinvasion or metabolism by the CAM, whereas boiled tissue undergoes resorption. Clinically, uncontrolled heating may result in total resorption of cartilage with catastrophic sequelae such as infection, necrosis, and total graft resorption. This study underscores the importance of preserving cartilage viability during laser surgical procedures relying on a photothermal mechanism.

Effect of osmolarity on shape retention following laser-mediated cartilage reshaping

Laser reshaping of mechanically deformed cartilage specimens accelerates stress relaxation and results in permanent shape change. The mechanism of laser-mediated cartilage reshaping is still unknown, but clearly depends upon the complex molecular interactions between the physio-chemical environment and matrix proteins (collagen, and proteoglycans). It is well known in articular tissues that the mechanical properties of cartilage are sensitive to changes in tissue pH and osmolarity. The objective of this study was to determine the effect of osmolarity on shape change during laser reshaping in morphologic cartilage tissues. Porcine nasal septal cartilage specimens were cut (20 x 5 x 1.5 mm) and immersed in osmotically graded NaCl (0.2NS, 0.8NS, 1.0NS, 1.2 NS and 5 NS) or Phosphate buffered (0.2NS, 0.9NS, 1.0NS, 1.1NS, and 5NS) solutions for 12 hours to establish equilibrium. Then, specimens were bent into semicircular shapes, secured with clamps, and irradiated with an Nd:YAG laser (λ= 1320nm, 5W, 15 secs, 5 mm spot size) along the region of maximum curvature. Resultant bend angle was measured. Shape retention was calculated by comparing resultant curvature with pre-irradiation measurements. Non-irradiated, untreated (negative controls) cartilage retained less than 46% of the original bend. There was no difference in shape retention with respect to varying osmolarity (changed tissue water content) in either group. Resultant bend angles varied from 84 degree(s) to 194 degree(s) corresponding to shape retention varying from 42% to 72% in specimens which were immersed in either NaCl of Phosphate buffered solutions. While laser heating of deformed specimens does result in significant reshaping, the alterations in osmolarity do not seem to effect this process significantly over the range of values evaluated in this study.

Distinguishing Edema vs Scar in the Rabbit Subglottis Using Optical Coherence Tomography

Problem: In neonates, subglottic stenosis is a tremendous problem related to prolonged enotracheal intubation. Despite the use of diagnostic endoscopy, differentiating between edema, scar, or neocartilage formation remains a challenge. Optical Coherence Tomography (OCT) is an imaging modality that uses light to produce high-resolution cross-sectional images in tissue. Using an ex vivo rabbit laryngotracheal model, we evaluate the efficacy of OCT to differentiate between several simulated subglottic pathologies. Methods: Seven laryngeal-tracheal complexes were harvested from freshly sacrificed rabbits. The specimens were divided into 4 groups: (1) control; (2) submucosal collagen injection (simulating scar formation); (3) dehydration/hydration (simulating edema); and (4) repeated intubation trauma. The subglottic region was imaged using an OCT system that produced images with axial and lateral resolution of 10 and 20 μm, respectively. The submucosal thickness (basement membrane to perichondrium) was measured in each group and compared to controls. OCT images were later correlated with conventional histology. Results: The epithelium, basement membrane, lamina propria, perichondrium, and cartilage (cricoid and tracheal) were very clearly imaged. A 50% increase in submucosal thickness was observed in group 2, and the collagen was clearly identified and distinct from surrounding native tissues. Dehydration (group 3) produced a 60% reduction while rehydrating the same specimen in distilled water resulted in a 350% increase. Edema, produced by either repeated intubation or distilled water immersion, was easily differentiated from both native and the collagen-injected tissues. Conclusion: OCT successfully identifies the layer micro-structure of the subglottis and can be used to differentiate between edema and increased collagen in the rabbit model. Significance: OCT can be readily adapted for use during rigid and flexible endoscopy. Likewise, since OCT imaging fibers can be placed within endotracheal tubes to image the airway, the technique is an extremely attractive option for use in the ICU to manage the neonatal airway. Support: None reported.

Laser applications in pediatric airway surgery

The smaller anatomy and limited access to instrumentation pose a challenge to the pediatric airway surgeon. The enhanced precision and ability to photocoagulate tissue while operating with the laser enhances the surgeon’s ability to successfully treat unique pediatric conditions such subglottic hemangiomas, congenital cysts, respiratory papillomatosis, and laryngeal or tracheal stenosis. Due to its shallow tissue penetration and thermal effect, the carbon dioxide (CO2) laser is generally considered the laser of choice for pediatric airway applications. The potential for increased scarring and damage to underlying tissue caused by the greater penetration depth and thermal effect of the Nd:YAG and KTP lasers preclude their use in this population. In this review, we will describe the specific advantages of using lasers in airway surgery, the current technology and where the current technology is deficient.

Cartilage reshaping: an overview of the state of the art

The laser irradiation of cartilage results in a plastic deformation of the tissue allowing for the creation of new stable shapes. During photothermal stimulation, mechanically deformed cartilage undergoes a temperature dependent phase transition, which results in accelerated stress relaxation of the tissue matrix. Cartilage specimens thus reshaped can be used to recreate the underlying framework of structures in the head and neck. Optimization of this process has required an understanding of the biophysical processes accompanying reshaping and also determination of the laser dosimetry parameters, which maintain graft viability. Extensive in vitro, ex-vivo, and in vivo animal investigations, as well as human trials, have been conducted. This technology is now in use to correct septal deviations in an office-based setting. While the emphasis of clinical investigation has focused on septoplasty procedures, laser mediated cartilage reshaping may have application in surgical procedures involving the trachea, laryngeal framework, external ear, and nasal tip. Future directions for research and device design are discussed.