A laser platform incorporating a novel 524 nm laser pumped by a commercial hair removal laser effectively treats facial redness and lower-extremity spider veins.

BACKGROUND AND OBJECTIVES: Treatment of vascular lesions is one of the main applications of cutaneous laser technology, while the other is laser hair removal. We present here a vascular laser pumped by a commercial hair removal laser. STUDY DESIGN/MATERIALS AND METHODS: A novel 524 nm vascular laser was designed using a 755 nm hair removal laser as a pumping source. This 524 nm vascular laser was used to treat facial redness and leg telangiectasias in 24 subjects. Four treatments were administered to the face at 4-6-week intervals and final photographs were taken 8 weeks following the final treatment, while two treatments were administered to lower-extremity spider veins at 2-month intervals with follow-up photographs 3 months following the final treatment. Blinded analysis of digital images was performed by two physicians not involved in the study. RESULTS: Blinded evaluation of digital photographs revealed an average improvement score of 3.3 ± 1.7 (mean ± SEM) on a 0-10 scale for removing facial redness (p < 0.001), representing a 33% improvement. Leg veins improved an average of 51% corresponding to a score of 5.1 ± 2.0 (p < 0.001). Side effects were mild and limited to erythema, purpura, edema, and one instance of mild hyperpigmentation. CONCLUSIONS: This novel 524 nm laser is safe and effective for treating vascularity on the face and legs, and proves the ability to create a laser platform incorporating a hair removal laser which then can be used as a pumping source for the attached vascular laser module.

Clinical evaluation of a non-ablative 1940 nm fractional laser.

BACKGROUND AND OBJECTIVES: Non-ablative fractional lasers cause little down-time, however, some patients want more noticeable results with fewer treatments. The 1940 nm wavelength matches one of the water absorption peaks in the mid infrared band of electromagnetic energy. The skin absorption is much stronger than other non-ablative wavelengths (1410-1550 nm) and weaker than ablative wavelengths (Er:YAG or CO2). The objective of this study was to characterize clinical efficacy using this technology to treat photodamaged skin in human subjects. MATERIALS AND METHODS: Under an IRB approved study, eleven subjects with facial photodamage (1 male and 10 female) were enrolled and completed the study. The fractional 1940 nm laser was comprised of a thulium rod pumped by a pulsed alexandrite laser. The fractional patterns were generated by four separate handpieces (two dot (0.48mm and 0.76mm dot-to-dot distance or pitch) and two grid geometries) whereby a larger beam was broken up into smaller microbeams by a microlens system or reflective square grids. The low -pitch circular dot array handpiece, which is used most frequently, has a macro-spot size of 12 mm and a total applied energy of approximately 2-5 J (~ 4-10 mJ per beamlet). Contact skin cooling (5-20degC) was provided via a sapphire window at the distal end of handpiece. Pulses from the dot handpieces were applied with 20% overlap. The microspot size for the dot handpieces was ~ 0.2-0.3 mm. The two grid pattern handpieces included 0.4 mm wide lines with 45% and 0.7 mm wide lines with 65% coverage. Each subject received 3 full-face treatments 4-6 weeks apart. Anesthesia was achieved by 5% lidocaine cream and a cold air chiller. Typical treatments were carried out with two passes. Outcome assessments included changes in pigment, rhytides, laxity, elastosis, and texture, using a diffuse pigmentation scale and the Alexiades-Armenakas Comprehensive Grading Scale of Rhytides, Laxity, and Photodamage. Photographs of each patient from prior to treatment, and 3 months after treatment were analyzed by 3 blinded physician raters. A paired t-test was applied for each category comparing the pre treatment and 3-month post treatment results. RESULTS: Three months after the final treatment, (a) mean pigment improvement was 21.1%, (b) rhytides were reduced by 14.3%, (c) laxity was reduced by 8.9%, elastosis was reduced by 22.3%, and (e) texture scores were unchanged. Reductions in pigmentation, rhytides, and elastosis were statistically significant (P≤ 0.05). Clinical downtime was 3-5 days. Pain was variable (mean of 2.8/10) and side effects included two cases of mild focal vesiculation. No long-term side effects were noted. Histological analysis showed focal damage that extended about 200 µm deep to the surface. CONCLUSION: The 1940nm thulium laser is safe, well tolerated, and results in reduced downtime compared to traditional resurfacing. The study demonstrated that the 1940 nm thulium laser could achieve injury patterns capable of skin rejuvenation.

Deep subsurface cavities in skin utilizing mechanical optical clearing and femtosecond laser ablation.

BACKGROUND AND OBJECTIVES: High precision subsurface ablation can be produced in transparent materials using femtosecond laser pulses and multiphoton absorption. Light scattering limits application of the same technique to most biological tissues. Previously, subsurface ablation was demonstrated at superficial depths (50-250 µm) in highly scattering tissues including murine skin and human sclera. We report application of mechanical optical clearing to produce deeper subsurface femtosecond ablation in rodent skin. Ability to target deeper structures in skin using subsurface ablation may allow novel clinical applications for dermatological laser surgery. STUDY DESIGN/MATERIALS AND METHODS: Operation of a prototype tissue optical clearing device (TOCD) was verified with white light photography in ex vivo rodent skin. A focused femtosecond beam transmitted through the TOCD and was scanned across rodent skin to produce subsurface ablation at increasing focal depths. Histological sections with H&E staining of the laser irradiated rodent skin were examined for subsurface ablation features following laser irradiation. RESULTS: Subsurface cavities were observed as deep as 1.7 mm below the skin surface in histological tissue sections. Diameter of subsurface cavities varied from tens of microns to over 100 µm. Subsurface cavities produced by scanning the focused femtosecond beam were contiguous and formed a continuous cut. Mechanical disruption of the overlying tissues was not observed. CONCLUSIONS: Mechanical optical clearing can be applied directly to in situ rodent skin and produces an optical clearing effect. High precision subsurface ablation can be produced at positions substantially deeper than previously demonstrated. Future studies may be targeted in in vivo human skin to investigate potential clinical applications of subsurface femtosecond ablation using mechanical optical clearing.

Optimal power settings for Holmium:YAG lithotripsy.

PURPOSE: We determined the optimal Ho:YAG lithotripsy power settings to achieve maximal fragmentation, minimal fragment size and minimal retropulsion. MATERIALS AND METHODS: Stone phantoms were irradiated in water with a Ho:YAG laser using a 365 µm optical fiber. Six distinct power settings were tested, including 0.2 to 2.0 J and 10 to 40 Hz. For all cohorts 500 J total radiant energy were delivered. A seventh cohort (0.2 J 40 Hz) was tested post hoc to a total energy of 1,250 J. Two experimental conditions were tested, including with and without phantom stabilization. Total fragmentation, fragment size and retropulsion were characterized. In mechanism experiments using human calculi we measured crater volume by optical coherence tomography and pressure transients by needle hydrophone across similar power settings. RESULTS: Without stabilization increased pulse energy settings produced increased total fragmentation and increased retropulsion (each p <0.0001). Fragment size was smallest for the 0.2 J cohorts (p <0.02). With stabilization increased pulse energy settings produced increased total fragmentation and increased retropulsion but also increased fragment size (each p <0.0001). Craters remained symmetrical and volume increased as pulse energy increased. Pressure transients remained modest at less than 30 bars even at 2.0 J pulse energy. CONCLUSIONS: Holmium:YAG lithotripsy varies as pulse energy settings vary. At low pulse energy (0.2 J) less fragmentation and retropulsion occur and small fragments are produced. At high pulse energy (2.0 J) more fragmentation and retropulsion occur with larger fragments. Anti-retropulsion devices produce more efficient lithotripsy, particularly at high pulse energy. Optimal lithotripsy laser dosimetry depends on the desired outcome.

Combined two-photon luminescence microscopy and OCT for macrophage detection in the hypercholesterolemic rabbit aorta using plasmonic gold nanorose.

BACKGROUND AND OBJECTIVES: The macrophage is an important early cellular marker related to risk of future rupture of atherosclerotic plaques. Two-channel two-photon luminescence (TPL) microscopy combined with optical coherence tomography (OCT) was used to detect, and further characterize the distribution of aorta-based macrophages using plasmonic gold nanorose as an imaging contrast agent. STUDY DESIGN/MATERIALS AND METHODS: Nanorose uptake by macrophages was identified by TPL microscopy in macrophage cell culture. Ex vivo aorta segments (8 × 8 × 2 mm(3) ) rich in macrophages from a rabbit model of aorta inflammation were imaged by TPL microscopy in combination with OCT. Aorta histological sections (5 µm in thickness) were also imaged by TPL microscopy. RESULTS: Merged two-channel TPL images showed the lateral and depth distribution of nanorose-loaded macrophages (confirmed by RAM-11 stain) and other aorta components (e.g., elastin fiber and lipid droplet), suggesting that nanorose-loaded macrophages are diffusively distributed and mostly detected superficially within 20 µm from the luminal surface of the aorta. Moreover, OCT images depicted detailed surface structure of the diseased aorta. CONCLUSIONS: Results suggest that TPL microscopy combined with OCT can simultaneously reveal macrophage distribution with respect to aorta surface structure, which has the potential to detect vulnerable plaques and monitor plaque-based macrophages overtime during cardiovascular interventions.

Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles.

The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques.

Comparison of pulsed photothermal radiometry, optical coherence tomography and ultrasound for melanoma thickness measurement in PDMS tissue phantoms.

Melanoma accounts for 75% of all skin cancer deaths. Pulsed photothermal radiometry (PPTR), optical coherence tomography (OCT) and ultrasound (US) are non-invasive imaging techniques that may be used to measure melanoma thickness, thus, determining surgical margins. We constructed a series of PDMS tissue phantoms simulating melanomas of different thicknesses. PPTR, OCT and US measurements were recorded from PDMS tissue phantoms and results were compared in terms of axial imaging range, axial resolution and imaging time. A Monte Carlo simulation and three-dimensional heat transfer model was constructed to simulate PPTR measurement. Experimental results show that PPTR and US can provide a wide axial imaging range (75 µm-1.7 mm and 120-910 µm respectively) but poor axial resolution (75 and 120 µm respectively) in PDMS tissue phantoms, while OCT has the most superficial axial imaging range (14-450 µm) but highest axial resolution (14 µm). The Monte Carlo simulation and three-dimensional heat transfer model give good agreement with PPTR measurement. PPTR and US are suited to measure thicker melanoma lesions (>400 µm), while OCT is better to measure thin melanoma lesions (<400 µm).

Depth-resolved blood oxygen saturation measurement by dual-wavelength photothermal (DWP) optical coherence tomography.

Non-invasive depth-resolved measurement of hemoglobin oxygen saturation (SaO(2)) levels in discrete blood vessels may have implications for diagnosis and treatment of various pathologies. We introduce a novel Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) for non-invasive depth-resolved measurement of SaO(2) levels in a blood vessel phantom. DWP OCT SaO(2) is linearly correlated with blood-gas SaO(2) measurements. We demonstrate 6.3% precision in SaO(2) levels measured a phantom blood vessel using DWP-OCT with 800 and 765 nm excitation wavelengths. Sources of uncertainty in SaO(2) levels measured with DWP-OCT are identified and characterized.

Femtosecond laser lithotripsy: feasibility and ablation mechanism.

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (lambda=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 microm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 microm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

Comparison of fluoride and sapphire optical fibers for Er: YAG laser lithotripsy.

The long-pulse (200-350 micros) Holmium: YAG (Ho: YAG) laser (lambda = 2.12 microm) is used extensively in urology for laser lithotripsy. The long-pulse Erbium: YAG (Er: YAG) laser (lambda = 2.94 microm) fragments urinary calculi up to 5 times more efficiently than the Ho: YAG laser, however, no optical fibers are available to transmit efficiently 2.94 microm laser light for laser lithotripsy. We report results of a study evaluating a fluoride glass fiber to transmit Er: YAG laser light for laser lithotripsy and compare to a sapphire fiber that provides good transmission of Er: YAG light at low irradiance. The fluoride fiber provides superior light transmission efficiency over the sapphire fiber at an Er: YAG wavelength (2.94 microm). The sapphire fiber provides a more durable and robust delivery waveguide than the fluoride fiber when ablating urinary calculi in contact mode. Results of our study suggest that further development to improve performance of fluoride fibers for laser lithotripsy is warranted.