Lasers in Surgery and Medicine

Published by Wiley

Online ISSN: 1096-9101


Print ISSN: 0196-8092


MR-based Thermometry of Laser Induced Thermotherapy: Temperature Accuracy and Temporal Resolution In vitro at 0.2 and 1.5 T Magnetic Field Strengths
  • Article

March 2012


153 Reads






To evaluate MR-thermometry using fast MR sequences for laser induced interstitial thermotherapy (LITT) at 0.2 and 1.5 T systems. In-vitro experiments were performed using Agarose gel mixture and lobes of porcine liver. MR-thermometry was performed by means of longitudinal relaxation time (T1) and proton resonance frequency shift (PRF) methods under acquisition of amplitude and phase shift images. Four different sequences were used for T1 thermometry: A gradient-echo (GRE), a True Fast Imaging with Steady Precession (TRUFI), a Saturation Recovery Turbo-FLASH (SRTF), and an Inversion Recovery Turbo-FLASH (IRTF) sequence (FLASH-Fast Low Angle Shot). PRF was measured with four sequences: Two fast-spoiled GRE sequences (one as WIP sequence), a Turbo-FLASH (TFL) sequence (WIP sequence), and a multiecho-TrueFISP sequence. Temperature was controlled and verified using a fiber-optic Luxtron device. The temperature was correlated with the MR measurement. All sequences showed a good linear correlation R(2) = 0.97-0.99 between the measured temperature and the MR-thermometry measurements. The only exception was the TRUFI sequence in the Agarose phantom that showed a non-linear calibration curve R(2) = 0.39-0.67. At 1.5 T, the Agarose experiments revealed similar temperature accuracies of 4-6°C for all sequences excluding TRUFI. During experiments with the liver, the PRF sequences showed better performance than the T1, with accuracies of 5-12°C, contrary to the T1 sequences at 14-18°C. The accuracy of the Siemens PRF-FLASH sequence was 5.1°C. At 0.2 T, the Agarose experiments provided the highest accuracy of 3.3°C for PRF measurement. At the liver experiments the T1 sequences SRTF and FLASH revealed the best accuracies at 6.4 and 7.0°C. The accuracy and speed of MR temperature measurements are sufficient for controlling the temperature-based tumor destruction. For 0.2 T systems SRTF and FLASH sequences are recommended. For 1.5 T systems SRTF and FLASH are the most accurate.

Peripheral thermal and mechanical damage to dentin with microsecond and sub-microsecond 9.6 ?m, 2.79 ?m, and 0.355 ?m laser pulses

September 2004


55 Reads

Background and objectives: It is desirable to minimize peripheral thermal damage during laser irradiation, since thermal damage to collagen and mineral compromises the bond strength to restorative materials in dentin and inhibits healing and osteointegration in bone. There were two primary objectives of this study. The first objective was to measure the degree of thermal damage peripheral to incisions in dentin produced with lasers resonant to the specific absorption bands of water, collagen, and hydroxyapatite with varying pulse duration using polarized-light microscopy (PLM). The second objective was to use synchrotron radiation infrared spectromicroscopy (SR-FTIR) to identify the specific chemical nature of the optical changes observed under PLM in the respective zones of thermal damage peripheral to the laser incisions. Study design/materials and methods: Precise incisions were produced in 3 x 3 mm2 blocks of human dentin using CO2 (9.6 microm), Er:YSGG (2.79 microm), and Nd:YAG (355 nm) lasers with and without a computer controlled water-spray. Optical coherence tomography (OCT) was used to obtain optical cross-sections of each incision to determine the rate of ablation. The peripheral thermal damage zone around each incision was analyzed using PLM and SR-FTIR. Results: Thermally induced chemical changes to both mineral and the collagen matrix were observed with SR-FTIR with a 10 microm spatial resolution and those changes were correlated with optical changes observed with PLM. Minimal (<10 microm) thermal damage was observed for pulse durations less than the thermal relaxation time (Tr) of the deposited laser energy, with and without applied water at 9.6 microm and with only applied water at 2.79 microm. For pulse durations greater than Tr, greater peripheral thermal damage was observed for both IR laser wavelengths with and without the water-spray. There was minimal thermal damage for 355 nm laser pulses less than Tr with and without applied water; however, extensive mechanical damage (cracks) was observed. Conclusions: High resolution SR-FTIR is well suited for characterization of the chemical changes that occur due to thermal damage peripheral to laser incisions in proteinaceous hard tissues. Sub-microsecond pulsed IR lasers resonant with water and mineral absorption bands ablate dentin efficiently with minimal thermal damage. Similar laser parameters are expected to apply to the ablation of alveolar bone.

Imaging temperature changes in an interventional 0.5 T magnet: In-vitro results

January 1997


16 Reads

To evaluate the ability of monitoring laser induced temperature changes in an open, interventional 0.5 T magnet, adopting fast T1-weighted sequences. A fast gradient echo- (FGRE) and a fast spoiled gradient echo-sequence (FSPGR), both enabling an image update every 2.5 s, were investigated for their ability to visualize laser tissue effects at 5 Watt. Laser induced temperature was fluorooptically measured and correlated with signal intensity (SI) changes depicted by magnetic resonance imaging (MRI). MRI-lesions were compared with macroscopic findings. SI changes on FGRE images appeared as early as 15 s following the onset of laser application and were significantly more pronounced than those seen on FSPGR images (p < .0001). A correlation of r = 0.94 (FGRE) and r = 0.92 (FSPGR) between temperature and SI loss was established. Owing to a steeper slope, the FGRE sequence was considered more sensitive to temperature changes. The areas of macroscopic tissue change correlated with those of SI loss, but lesion size was generally underestimated by MRI. Laser monitoring is possible with rapid image updates in a midfield (0.5 T) interventional MRI environment using fast gradient echo sequence designs.

Prospective Study of Port Wine Stain Treatment with Dye Laser: Comparison of Two Wavelengths (585 nm vs. 595 nm) and Two Pulse Durations (0.5 Milliseconds vs. 20 Milliseconds)

February 2004


23 Reads

Background and objectives: The conventional pulsed-dye laser (wavelength 585 nm, pulse duration 0.5 milliseconds) is seen as the standard treatment for port wine stains (PWS). Using the pulsed-dye laser at wavelengths of 590, 595, and 600 nm and at varying pulse durations of 1.5-40 milliseconds is one of the newest developments in the field, the therapeutic value of which has been examined in only a few studies. Treatment of PWS with short- and long-pulse dye lasers. Comparison of two wavelengths (585 nm vs. 595 nm) and two pulse durations (0.5 milliseconds vs. 20 milliseconds). Study design/materials and methods: Fifteen patients with untreated PWS were included in a randomized prospective study with three different laser settings. Patients underwent one treatment session. The following treatment parameters were chosen at a uniform spot size of 7 mm: (1) 585 nm/0.5 milliseconds/5.5 J/cm(2), (2) 595 nm/0.5 milliseconds/5.5 J/cm(2), and (3) 595 nm/20 milliseconds/13 J/cm(2). The clearance as well as side effects was evaluated. All treatments were performed with cold air-cooling. Follow-up took place immediately, 2 days and 4 weeks after the treatment. The PWS was assigned a clearance score (CS) from 1 to 4 (1 = poor to 4 = excellent). Results: Descriptively, 585 nm/0.5 milliseconds generated the best average CS of 2.7, followed by 595 nm/20 milliseconds (2.5) and 595 nm/0.5 milliseconds (1.6)); statistically, there is no difference between the CS of 585 nm/0.5 milliseconds and 595 nm/20 milliseconds. The best lightening rates overall were achieved in purple PWS (CS = 3.5) versus red (CS = 2.5) and pink (CS = 2.0). Purple PWS responded best to 585 nm/0.5 milliseconds; red and pink PWS yielded similar results with 585 nm/0.5 milliseconds and 595 nm/20 milliseconds. The setting, 595 nm/0.5 milliseconds was clearly not as effective as the other laser settings. Purpura, pain, and crusting were most commonly reported after treatments with 585 nm/0.5 milliseconds (93%/93%/33%), closely followed by treatments at 595 nm/20 milliseconds (86%/93%/20%). The settings 595 nm/0.5 milliseconds yielded the lowest rate of adverse effects (67%/60%/0%). Hypopigmentation only occurred in one case (585 nm/0.5 milliseconds), and there were no reports of hyperpigmentation or scarring. Conclusions: With respect to treating PWS, the conventional pulsed-dye laser set to 585 nm/0.5 milliseconds yields a significantly greater clearance rate than it does at a setting of 595 nm (with the same pulse duration, fluence, and spot size), although the former also entails the highest spectrum of adverse effects. In this study, purple PWS treated at these parameters showed the best results. In dealing with pink PWS, the results were similar to those of the conventional pulsed-dye laser when the pulse duration was increased to 20 milliseconds and fluence was increased. As a rule, the clearance rate corresponded to the extent of the postoperative purpura.

Effects of linearly polarized 0.6-1.6 mu M irradiation on stellate ganglion function in normal subjects and people with Complex Regional Pain (CRPS I)

June 2003


37 Reads

Stellate ganglion blocks are an effective but invasive treatment of upper extremity pain. Linearly polarized red and near-infrared (IR) light is promoted as a safe alternative to this procedure, but its effects are poorly established. This study was designed to assess the physiological effects of this latter approach and to quantitate its benefits in people with upper extremity pain due to Complex Regional Pain Syndrome I (CRPS I, RSD). This was a two-part study. In the first phase, six adults (ages 18-60) with normal neurological examinations underwent transcutaneous irradiation of their right stellate ganglion with linearly polarized 0.6-1.6 microm light (0.92 W, 88.3 J). Phase two consisted of a double-blinded evaluation of active and placebo radiation in 12 subjects (ages 18-72) of which 6 had upper extremity CRPS I and 6 served as "normal" controls. Skin temperature, heart rate (HR), sudomotor function, and vasomotor tone were monitored before, during, and for 30 minutes following irradiation. Analgesic and sensory effects were assessed over the same period as well as 1 and 2 weeks later. Three of six subjects with CRPS I and no control subjects experienced a sensation of warmth following active irradiation (P = 0.025). Two of the CRPS I subjects reported a >50% pain reduction. However, four noted minimal or no change and improvement did not reach statistical significance for the group as a whole. No statistically significant changes in autonomic function were noted. There were no adverse consequences. Irradiation is well tolerated. There is a suggestion in this small study that treatment is beneficial and that its benefits are not dependent on changes in sympathetic tone. Further evaluation is warranted.

Gas volume quantitation during argon ion laser ablation of atheromatous aorta in blood and 0.9% saline media with an optically shielded catheter

January 1988


11 Reads

Using an optically shielded fiber optic laser catheter, the amount of gas produced when firing an argon ion laser into 0.9% saline solution or blood alone and into atheromatous aorta in either a blood or 0.9% saline medium was quantitated. Energies from 0.25 to 4 joules (J) were used at powers of 2, 5, and 8 W. We found that total volume of gas produced is small not only at equilibrium (0.3 +/- 0.1 microliter/J when firing in blood alone and also when ablating aorta in blood or saline media) but also at peak (2.5 +/- 0.2 microliters/J firing in blood alone and 1.0 +/- 0.1 microliter/J or 0.9 +/- 0.1 microliter/J when ablating aorta in saline or blood, respectively). Because these volumes are small, a clinically significant event from a gas embolus is unlikely during intravascular laser ablation of atheromatous plaque in the energy and power range studied. No gas was quantitated when firing the argon ion laser into 0.9% saline solution alone. The peak gas volume when firing in blood alone was significantly greater than that produced in the other chamber environments. This is thought to be due to increased absorption of argon laser light by hemoglobin. The gas volumes produced by lasing aorta in 0.9% saline or blood were not statistically different.

Measurement of thermal effects on the optical properties of prostate tissue at wavelengths of 1,064 and 633 nm

February 1999


27 Reads

The extent of thermal injury during laser prostatectomy is dependent on the light distribution in laser-irradiated tissue. As tissue is irradiated, the optical properties change as a function of temperature due to an alteration of molecular and cellular structure. The purpose of the present study was to determine how the exposure of both fresh and previously frozen canine prostate tissue to elevated temperatures affects the optical properties. Optical properties were measured by using a double integrating sphere spectrophotometer with an inverse adding-doubling algorithm. Measurements were made at two wavelengths (1,064 nm and 633 nm) on samples heated in a waterbath in 5 degree-10 degree increments for 10 min through a 50 degrees C temperature range. Upon coagulation, the absorption coefficient of fresh tissue decreased from the baseline measurement for both wavelengths (0.027 +/- 0.003 to 0.019 +/- 0.002 for lambda = 1,064 nm; 0.073 +/- 0.007 to 0.061 +/- 0.006 for lambda = 633 nm). However, the scattering coefficient increased sharply from the baseline measurement following coagulation (3.06 +/- 0.26 to 6.05 +/- 0.29 for lambda = 1,064 nm; 4.89 +/- 0.23 to 7.22 +/- 0.30 for lambda = 633 nm). Thermal coagulation occurred during exposure to temperatures between 60 degrees C and 70 degrees C. Data obtained in this study indicate that thermal coagulation of tissue alters the optical properties. The extent to which these changes occur was found to be dependent on wavelength and freshness of tissue. These results are significant because they suggest how thermally induced changes in the optical properties may limit the depth of light penetration in tissue thus compromising treatment.

A Comparison of Three Separate Clinical Studies Evaluating the Safety and Efficacy of Laser-Assisted Lipolysis Using 1,064, 1,320 nm, and a Combined 1,064/1,320 nm Multiplex Device

December 2009


36 Reads

Laser-assisted lipolysis has been suggested to augment traditional liposculpture by improving skin laxity and providing hemostasis. Previous studies have reported improved hemostasis and smoother post-operative appearance with the 1,064 Nd:YAG laser-assisted lipolysis system. Three separate pilot studies were performed. In the first study, both arms were treated with tumescent liposculpture. One arm was randomized to treatment with a subcutaneous 1,064 nm Nd:YAG laser. The second study treated multiple sites with half of the area randomized to receive the 1,064 nm versus the 1,320 nm system followed by aspiration at equal power. The third study treated patients using a combined 1,064/1,320 nm multiplex laser system at multiple sites. The endpoint of laser treatment was determined by an external skin surface temperature of 40 degrees C. In all three studies, photographs were compared at 1 week, 1 month, and 3 months post-operatively. In the first study, no significant improvement over tumescent liposculpture alone was noted using the 10 W, 1,064 nm laser. The second study showed no difference using the 10 W, 1,320 nm versus the 10 W, 1,064 nm laser-assisted lipolysis system. Finally, the multiplex 1,064/1,320 nm system appeared to show improvement in skin laxity and fat reduction. Complications included intra-operative thermal burns in 2 of 20 patients using the multiplex system. No complications were noted using the 1,064 or 1,320 nm 10 W systems. Laser-assisted lipolysis provides an innovative way to address the problem of skin laxity and fat reduction. Clinical results increased dramatically with the combined 1,064/1,320 nm multiplex system. However, caution should be used when exceeding external skin temperatures of 40 degrees C to avoid unwanted thermal burns. Future studies comparing the end temperature and wavelengths independently may help to conclusively delineate the optimal system.

A useful algorithm for determining fluence and pulse width for vascular targets using 1,064 nm Nd:YAG laser in an animal model

June 2004


78 Reads

Many current parameters to ablate vascular beds using 1,064 nm lasers are based on high-energy settings and often fail to consider vessel diameter and/or pulse width. This study attempts to define the minimal effective dosage (MED) of energy and pulse width for specific vessel diameters in an animal model. 1,064 nm Nd: YAG was used in 15 Sprague-Dawley rats. Bilateral extended dorsolateral skin flaps were elevated and vessel diameters from 0.1 to 1 mm were identified. Pulse widths (PW) in a range of 15-60 milliseconds and fluences between 70-110 J/cm2 with contact cooling at 5 degrees C (Celsius) were utilized. Results were determined clinically and histologically. Ideal pulse width and MED for each vessel diameter were determined using a 6 mm spot size. Histology showed early hemostasis and subsequent thrombosis, which are consistent with clinical findings. This model allows in vivo monitoring of vessel ablation. Optimal pulse width and MED levels versus vessel diameter determined in this animal model provide a useful algorithm that may allow for more effective treatment of vascular targets utilizing the 1,064 nm Nd:YAG laser.

Comparison and Sequential Study of Long Pulsed Nd:YAG 1,064 nm Laser and Sclerotherapy in Leg Telangiectasias Treatment

March 2004


222 Reads

Millisecond pulsed 1,064 nm Nd:YAG lasers have been developed for the treatment of leg telangiectasias. To date there have been very few side by side comparison studies of laser versus the gold standard sclerotherapy in treating small leg veins. This study aims to compare a long pulsed Nd:YAG laser with contact cooling to sclerotherapy for treating small diameter leg telangiectasias by evaluating objective and subjective clinical effects. Fourteen patients were selected with leg telangiectasias ranging from 0.5 to 2 mm at four comparable sites. One site was treated with long pulsed Nd:YAG alone, the second received sclerotherapy alone, the third laser then sclerotherapy, and the last one sclerotherapy then laser. The patients were followed up at 3 months after the last treatment. Photographs were taken pre-operatively and at 3 months after the last session. They were used for objective and comparative analysis. Statistical analysis was performed using Friedman's test controlling for subject. Improvement was tabulated from the photographic assessment on an improvement scale from 0 (no change) to 4 (greater than 75% clearing). There were clinical improvements in the laser group than sclerotherapy without statistical significance. Side effects were minimal and included hyperpigmentation. This pilot study demonstrates that the Smartepil LS long pulse Nd:YAG 1,064 nm laser can yield results similar to sclerotherapy in the treatment of small leg telangiectasias. Combination of both methods could increase response to treatment.

Clinical evaluation of enhanced nonablative skin rejuvenation using a combination of a 532 and a 1,064 nm laser

June 2004


150 Reads

Improvements in the physical signs of photoaging can be achieved by non-invasive laser resurfacing procedures. To evaluate the effectiveness and safety of the Nd:YAG 1,064 nm and KTP 532 nm lasers for non-invasive skin rejuvenation. Subjects requesting non-invasive skin rejuvenation underwent two treatments with the 532 nm laser to one side of the face and with both lasers to the other side, followed by three treatments with the 1,064 nm laser to both sides. Skin characteristics were evaluated before, during, and up to 4 months after treatment. A >25% improvement in overall skin condition was observed for >30% of subjects at the 1 month follow-up and >40% of subjects at the 4 month follow-up. The greatest improvements were observed for visual dryness, roughness, and uneven pigmentation. No adverse events were reported. There was a trend for greater improvement in patients who received more 1,064 nm treatments but this was not statistically significant. The 532 nm KTP and 1,064 nm Nd: YAG lasers can be effectively and safely used for non-invasive skin rejuvenation.

60-minute application of S-Caine Peel prior to 1,064 nm long-pulsed Nd:YAG laser treatment of leg veins

June 2004


13 Reads

Advancements in laser treatment of leg veins necessitate concurrent investigations in topical anesthesia to minimize treatment-related pain. To evaluate the efficacy of the S-Caine Peel for providing topical anesthesia after a 60-minute application. A randomized, double-blinded, placebo-controlled trial was performed in two centers. Sixty patients received S-Caine Peel and placebo vehicle on different treatment sites for 60 minutes prior to laser treatment of leg veins using a 1,064 nm long-pulsed Nd:YAG laser. Patients rated their level of pain using a visual analog scale. Adequacy of anesthesia and expressed pain at each site were rated by the investigator. The mean visual analog scale (VAS) was 27 mm for active sites compared to 43 mm for placebo (P < 0.001). Improved pain relief was noted for 67% of active versus 30% of placebo sites (P < 0.001). Anesthesia was judged adequate by the investigator for 55% of active compared with 12% of placebo sites (P < 0.001). The S-Caine Peel is safe and effective when applied for 60 minutes prior to laser therapy of leg veins.

A Pilot Study of the Efficacy of a 1,064 and 1,320 nm Sequentially Firing Nd:YAG Laser Device for Lipolysis and Skin Tightening

December 2009


64 Reads

Laser-assisted lipolysis with a medium pulsed 1,064 nm Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG) system has been used since FDA approval in October 2006 [1]. Since then, this technology has been advanced to include an additional wavelength (1,320 nm) and an accelerometer designed to improve efficacy and safety. (1) Evaluate the efficacy and safety of a sequentially firing 1,064 and 1,320 nm Nd:YAG laser device for lipolysis. (2) Evaluate the skin tightening effect by photographic documentation and skin measurements. (3) Assess new collagen formation by histologic and scanning electron microscopic studies. Twenty subjects with unwanted local adiposities and skin laxity were enrolled. An Nd:YAG laser with sequentially firing wavelengths of 1,064/1,320 nm was used to treat localized areas of body adiposities. Digital photographs were taken before and after treatment, blinded independent observers graded improvement utilizing a percentile evaluation scale and subjects performed self-assessments. Five of the 20 subjects had the following tests performed: (1) Placement of 4 cmx4 cm square India Ink tattoos for measurement of skin tightening, (2) histology and electron microscopy, (3) biopsies prior to the procedure, 3 days and 1 month after the procedure to determine the presence of new collagen markers. Results showed reduction in localized adiposities with no adverse events from use of this device. Independent observers found 76-100% improvement in adiposities in 85% of subjects and 51-75% improvement in 15% of subjects. Of the subset of five patients, India Ink tattoo maps demonstrated an 18% decrease in surface area indicating a significant skin tightening effect. Histology by H&E, Methylene blue stains, and electron microscopy indicated new collagen formation compared to baseline. The 1,064 nm Nd:YAG and 1,320 nm Nd:YAG sequentially firing device with an accelerometer appears to be an effective and safe treatment for localized adiposities with the additional benefit of skin tightening.

Bactericidal effect of pulsed 1,064 nm Nd : YAG laser light on Staphylococcus epidermidis is of photothermal origin: An in vitro study

February 2000


59 Reads

The aim was to investigate the bactericidal effect of the 1,064 nm Nd:YAG laser on Staphylococcus epidermidis. S. epidermidis was inoculated on agar plates and then exposed to pulsed laser light in three different modes: with an uninterrupted train of pulses, or with two different repeated cycles of fractionated trains of pulses. The agar temperature was measured directly after uninterrupted radiation. A bacterial growth inhibition area of 0.3 cm(2) and maximum temperature of approximately 80 degrees C was observed after uninterrupted radiation at 2,000 J cm(-2). The corresponding figures after an exposure of 5,000 J cm(-2) were 0.9 cm(2) and 100 degrees C, respectively. No bacterial inhibition was observed after exposure to repeated cycles of 20 seconds of radiation followed by 60 seconds of rest. The antimicrobial effect of the 1,064 nm Nd:YAG laser light is caused by a photothermal rather than a photochemical effect.

Retrospective analysis of non-ablative scar treatment in dark skin types using the sub-millisecond Nd:YAG 1,064 nm Laser

February 2011


97 Reads

Background: The use of lasers to treat atrophic scarring conditions in darker skin types presents a significant challenge to laser practitioners. Current treatment modalities, including deep dermal peels; ablative; non-ablative; and fractional laser resurfacing and surgical techniques, are limited in skin types IV through VI due to increased risks of hyper- and hypo-pigmentation. This is especially true when attempting to treat large areas of acne scarring. This study investigates the treatment of atrophic scarring with a non-ablative sub-millisecond-pulsed 1,064 nm Nd:YAG laser in darker skin types. Objective: To evaluate the safety and efficacy of a sub-millisecond 1,064 nm Nd:YAG laser for the treatment of atrophic scarring in Fitzpatrick skin types III-VI through retrospective photographic analysis. Methods: A retrospective analysis was conducted of all patients (n = 22) who received sub-millisecond Nd:YAG laser treatments for atrophic scarring over a 6-month period. Patients had Fitzpatrick skin types III-VI and were treated for the indication of atrophic scarring using the fluence of 14-16 J/cm(2) , pulse duration of 300-500 microseconds and repetition rate of 5-7 Hz. An average of six treatments was performed on each patient approximately 3 weeks apart and the mean follow-up time after the final treatment was 9 months (range of 3-10 months). Blinded photographic assessments were performed by three independent physicians using photos unlabeled for before and after and arranged in non-chronological order. Reviewers were asked to determine before and after photos and the degree of improvement in scarring, textural change, and post-inflammatory hyper-pigmentation (PIH) secondary to the acne or scarring condition. Degree of improvement was graded using a four-point scale: 0 = <25%, 1 = 25-50%, 2 = 51-75%, 3 = 76-100%. Results: Based on blinded photo assessments by three independent reviewers, clinically and statistically significant median improvement of 2 in scarring, 2.3 in texture, and 2 in pigment were observed (one-sample Wilcoxon signed rank test, P < 0.001). Reviewers were highly consistent (inter-reviewer reliability) in identification of before and after photos (kappa of 0.88). Conclusions: Preliminary data collected in this retrospective study suggest that sub-millisecond 1,064 nm Nd:YAG laser treatment is a safe and effective treatment for atrophic scarring in patients with darker skin types, delivering clinically and statistically significant results with reduced risk of pigment complications and patient discomfort.

Histological evaluations following 1,064-nm Nd : YAG laser resurfacing

August 2003


57 Reads

The long pulse 1,064-nm Nd:YAG laser is used clinically to decrease rhytid formation. The dermal level at which this change occurs has not been established. This study attempts to answer these questions using a porcine skin model. Non-randomized prospective experimental trial involving the domestic piglet treated serially with the long pulse 1,064-nm Nd:YAG laser. Collagen formation occurred at the level of the reticular dermis. After one laser treatment, a significant level of collagen formation was induced in the reticular dermis compared to controls. The greatest gain was observed after four laser treatments. Energy levels of 20, 30, 40, and 50 J/cm2 were evaluated. Although not statistically significant, 30 J/cm2 had the greatest effect on collagen formation. However, at 50 J/cm2, marked ablative changes to the epidermis were observed. The long pulse 1,064-nm Nd:YAG laser induces collagen formation in the reticular dermis in porcine skin.

Combined 585nm Pulsed-Dye and 1,064nm Nd:YAG Lasers for the Treatment of Basal Cell Carcinoma

March 2014


87 Reads

Basal cell carcinomas (BCCs) have supporting vasculature that serves as a target for vascular selective lasers. The objective of this study was to determine the effect of repeated treatment with a combined 585 nm pulsed dye laser (PDL) and 1,064 nm Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser on BCCs of superficial and nodular subtypes of varying diameters. Ten subjects with 13 biopsy-proven BCCs received four combined PDL and Nd:YAG at treatments 2-4 week intervals. None of the BCCs met the criteria for Mohs micrographic surgery. The tumor and 4 mm of peripheral skin were treated using standardized parameters delivered with a 7 mm spot with 10% overlap. The treated area was excised and evaluated histologically for residual tumor. The primary study endpoint was histologic clearance of tumor. The secondary study endpoint was blinded investigator assessment of clinical endpoint and adverse effects. Approximately half of all tumors showed a complete response to four combined PDL and Nd:YAG treatments (n = 7/12, 58%). When stratified by size, 75% of all tumors <1 cm in diameter (n = 6/8) showed complete response. Tumor histologic types among the complete responders included superficial and nodular BCCs. All subjects with incompletely responding BCCs were on various forms of anticoagulation, which we hypothesize, may inhibit laser-mediated thrombosis necessary for the clinical effect. Blinded investigator assessment suggests that biopsy related erythema improves with subsequent laser treatments. Combined PDL and Nd:YAG laser is an effective means of reducing tumor burden in patients with BCC and may be a promising, emerging alternative therapy. Factors influencing treatment response includes the concomitant use of anticoagulation. Further studies are needed to investigate and optimize the utility of this treatment protocol. Lasers Surg. Med. © 2013 Wiley Periodicals, Inc.

Superior lipolytic effect of the 1,444nm Nd:YAG laser: Comparison with the 1,064nm Nd:YAG laser

December 2009


371 Reads

Recently developed laser lipolysis systems have been disappointing because they require more time to remove the same amount of fat than other liposuction methods. A new Nd:YAG laser has been introduced that uses the 1,444 nm wavelength, better absorbed by fat. This study consisted of two protocols. The first protocol was an in vivo minipig model. Four 10x10 cm(2) areas were treated on the back of the first minipig. Using the same total energy and power settings (5,000 J, 8 W), both the 1,064 nm and 1,444 nm lasers were used to irradiate the two cephalic areas. The two caudal areas were irradiated with both lasers, using the maximum power settings (12 W with the 1,064 nm laser, 8 W with the 1,444 nm laser). Another minipig was administered a preoperative injection of tumescent solution and treated with the same condition. Measurements of fat volume with computed tomography and histologic exams were conducted. The second experiment involved in vitro human fat. Equal amounts of human fat, harvested by liposuction, were put into test tubes and irradiated with 1,064 nm and 1,444 nm lasers. Oil production was measured from each test tube. A marked reduction in fat volume and more oil vacuoles and giant cells in histology were identified with the 1,444 nm wavelength compared to the 1,064 nm wavelength. Human fat in the in vitro experiments also revealed more oil production following the use of the 1,444 nm laser. The 1,444 nm Nd:YAG laser showed a greater lipolytic effect compared to the 1,064 nm Nd:YAG laser in in vivo minipig and in vitro human fat experiments. To achieve a full understanding of the effects of 1,444 nm Nd:YAG laser lipolysis on the human body, in vivo experimentation will be necessary.

Effects of non-invasive, 1,210 nm laser exposure on adipose tissue: Results of a human pilot study

August 2009


160 Reads

Laser radiation (1,210 nm) has been previously shown to be capable of selective photothermolysis of adipose tissue in vitro when applied non-invasively. The objective of this pilot study was to evaluate the in vivo effects of this laser in human subjects. Twenty-four adult subjects were exposed non-invasively on the abdomen to a 1,210 nm laser at fluences of 70, 80, and 90 J/cm(2), with a 10 mm spot size, 5 seconds pre-cooling, and 3 seconds exposure duration delivered with parallel contact cooling. There was an impairment of the skin-cooling device during the study. Exposure and control sites were biopsied at either 1-3 days or 4-7 weeks. Tissue was processed for nitroblue tetrazolium chloride (NBTC) staining, a marker for thermal damage, and hematoxylin and eosin (H&E) staining. Laser exposures were painful, requiring local anesthesia in most subjects, but otherwise well tolerated. At 1-3 days after exposure, there was a fluence-dependent loss of NBTC staining in the fat and dermis. In 2 of 14 subjects (2 of 42 exposure sites) evaluated at 1-3 days after exposure, epidermal damage was noted within a small portion of the test site, likely due to impaired contact cooling. At 4-7 weeks, lipomembranous changes of the fat were seen in 89% of test sites and 33% of control sites. This in vivo study shows histologic evidence of laser-induced damage of fat. With further development, this might become a useful treatment for disorders involving the fat and/or lower dermis.

In Vivo Near-IR Imaging of Approximal Dental Decay at 1,310 nm

April 2010


61 Reads

The high transparency of dental enamel in the near-IR (NIR) light at 1,310-nm can be exploited for imaging dental caries without the use of ionizing radiation (X-rays). We present the results of the first in vivo imaging study in which NIR images were acquired of approximal contact surfaces. NIR imaging hand-pieces were developed and attached to a compact InGaAs focal plane array and subsequently used to acquire in vivo NIR images of 33 caries lesions on 18 test subjects. The carious lesions were discernible on bitewing radiographs, but were not visible upon clinical examination. NIR images were acquired in vivo from three directions and the majority of lesions examined were too small to require restoration, based on accepted bitewing radiograph criteria. All but one of the 33 lesions examined were successfully imaged from at least one direction. This first in vivo study of imaging at the 1,310-nm wavelength region shows that NIR imaging has great potential as a screening tool for the detection of approximal lesions without the use of ionizing radiation.

Laser resection technique and results of multiple lung metastasectomies using a new 1,318 nm Nd:YAG laser system

January 2006


169 Reads

Advantages of a new 1,318 nm Nd:YAG laser based on multiple lung metastasectomies are shown. Ninety-three percent of 328 patients with metastases (8/patient, range 1-124) had precision laser resections (lobectomy-rate reduced to 7%); this laser delivers 20 kW/cm(2) 1,318 nm power densities with 400 microm fibers, and a focussing handpiece. Absorption in water is tenfold higher. Between 1/1996 and 12/2003 in 328 patients (164 males/females, 61 years) 3,267 nodules were removed. Pathologic examination revealed 2,546 metastases (range 3-80 mm) from kidney (n = 112), colorectal (n = 91), and breast cancers (n = 35). In 85% of patients where the complete resection was achieved the 5-year survival was 41%. For remaining 15% (incomplete resection) the 5-year survival was 7%. Five-year survival for patients with 10 (and more) metastases was 28%, for patients with 20 (and more) was 26%. No 30-day mortality was observed. This new laser system facilitates any kind of parenchymal lung resection in lobe-sparing manner and in case of complete resection improves significantly the survival.

TABLE 1 . Energy Deposition Parameters for the Nd:YAG, Nd:YAP, and KTP Laser
Figure 6: Temperature profiles induced in the same test spots as above using the KTP laser (λ = 532 nm). Temperature values are scaled to radiant exposure value of H0 = 10 J/cm2.
Figure 7: Depth z50, up to which 50% of the absorbed laser energy was deposited at either anatomic location. Average values for each laser under consideration (see the legend) and their standard deviations (bars) are determined from three measurements performed on each test site in every volunteer.
Figure 8: Temperature profiles as measured in shoulder of volunteer LV upon irradiation with the Nd:YAP (solid line) and Nd:YAG laser (dashed), scaled up to reach the same epidermal temperature rise of 40°C. Note the corresponding radiant exposure values in the legend.
Energy deposition profile in human skin upon irradiation with a 1,342 nm Nd:YAP laser
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January 2013


370 Reads

Background and objectives: Nd:YAP laser emitting at 1,342 nm appears promising for nonablative skin rejuvenation treatment, based on favorable absorption properties of water and melanin in this part of the spectrum. A quantitative determination of energy deposition characteristics of Nd:YAP in normal human skin should enable design of a safe and effective treatment protocol for future human studies. Study design: Energy deposition profile of a prototype Nd:YAP laser was determined using pulsed photothermal radiometry. This technique involves time-resolved measurement of mid-infrared emission from a sample after pulsed laser irradiation. The laser-induced temperature depth profile is reconstructed from the radiometric transients using a custom optimization algorithm, developed and tested earlier in our group. Measurements were performed on the extremities of four healthy volunteers at low radiant exposure (2.8 J/cm(2) ). For the purpose of comparison, energy deposition characteristics of commercial Nd:YAG and KTP lasers (at 1,064 and 532 nm, respectively), were also determined at the same test sites. Results: On average, the Nd:YAP laser deposits 50% of the absorbed energy within the top 0.36 mm of skin and 90% within 0.86 mm, which is significantly shallower than the Nd:YAG laser. The ratio between the dermal versus epidermal heating is more favorable and shows a smaller inter- and intra-patient variance as compared to both Nd:YAG and KTP laser. Conclusions: Energy deposition characteristics of the 1,342 nm Nd:YAP laser are very suitable for controlled heating of the upper dermis, as required for nonablative skin rejuvenation. The risks of overheating the epidermis or subcutis should be significantly reduced in comparison with the 1,064 nm Nd:YAG laser.

Acne treatment with a 1,450 nm wavelength laser and cryogen spray cooling

August 2002


409 Reads

A laser with a wavelength in the mid-IR range targeting the depth in skin where sebaceous glands are located in combination with cryogen spray cooling was evaluated for treatment of acne. In this non-ablative treatment, the laser energy heats the dermal volume encompassing sebaceous glands whereas the cold cryogen spray preserves the epidermis from thermal damage. Monte Carlo simulations and heat transfer calculations were performed to optimize the heating and cooling parameters. A variety of heating and cooling parameters were tested in an in vivo rabbit ear study to evaluate the histological effect of the device on sebaceous glands and skin. Similar experiments were performed on ex vivo human skin. A clinical study for the treatment of acne on backs of human males was also conducted. Monte Carlo simulations and heat transfer calculations resulted in a thermal damage profile that showed epidermal preservation and peak damage in the upper dermis where sebaceous glands are located. Ex vivo human skin histology confirmed the damage profile qualitatively. In vivo rabbit ear histology studies indicated short-term thermal alteration of sebaceous glands with epidermal preservation. In the human clinical study on the back, a statistically significant reduction in lesion count on the treated side compared to the control side was seen (p < 0.001). Side effects were transient and few. The studies reported here demonstrate the feasibility of treating acne using a photothermal approach with a mid-IR laser and cryogen cooling.

A pilot investigation comparing low-energy, double pass 1,450 nm laser treatment of acne to conventional single-pass, high-energy treatment

February 2007


33 Reads

Laser treatment using a 1,450 nm diode laser has been shown to improve acne and acne scarring. Its widespread adoption in younger populations has been significantly limited by discomfort. Six subjects with active papular acne were treated in a pilot study to determine parameters for a split-face, double-pass, low-energy protocol of 1,450 nm laser treatment. Sides of the face were randomized to receive single-pass, high-energy treatment (13-14 J/cm(2)), or double-pass, low energy treatment (8-11 J/cm(2)), for a total of four treatments delivered at monthly intervals. Acne counts and standardized, digital photograph were performed 2 months following the final treatment, and compared to pre-treatment counts and photographs. Improvement was evaluated comparing pre- and post-treatment photos and averaged 2.5 for the high-energy, single-pass side and 2.3 for the low-energy, double-pass side, using a 0 (worse) to 4 (max improvement) scale. Acne counts were reduced 78% on the high-energy, single-pass side and 67% on the low-energy, double-pass side. Pain ratings on a 1 (min) to 10 (max) scale averaged 5.6 (range 1-9) for the high-energy, single-pass side and 1.3 (range 1-2) for the low-energy, double-pass side. Low-energy, double-pass 1,450 nm laser treatment effectively reduces acne counts 2 months post-treatment, and dramatically reduces the pain associated with treatment. The treatment parameters used in this study have eliminated the need for anesthetic cream in daily practice.

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