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Shao M, Li C, Meng C, Liu R, Yu P, Lu F, Zhong Z, Wei X, Zhou J, Zhong MC. Laser-induced microbubble as an in vivo valve for optofluidic manipulation in living Mice's microvessels. LAB ON A CHIP 2024; 24:3480-3489. [PMID: 38899528 DOI: 10.1039/d4lc00095a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Optofluidic regulation of blood microflow in vivo represents a significant method for investigating illnesses linked to abnormal changes in blood circulation. Currently, non-invasive strategies are limited to regulation within capillaries of approximately 10 μm in diameter because the adaption to blood pressure levels in the order of several hundred pascals poses a significant challenge in larger microvessels. In this study, using laser-induced microbubble formation within microvessels of the mouse auricle, we regulate blood microflow in small vessels with diameters in the tens of micrometers. By controlling the laser power, we can control the growth and stability of microbubbles in vivo. This controlled approach enables the achievement of prolonged ischemia and subsequent reperfusion of blood flow, and it can also regulate the microbubbles to function as micro-pumps for reverse blood pumping. Furthermore, by controlling the microbubble, narrow microflow channels can be formed between the microbubbles and microvessels for assessing the apparent viscosity of leukocytes, which is 76.9 ± 11.8 Pa·s in the in vivo blood environment. The proposed design of in vivo microbubble valves opens new avenues for constructing real-time blood regulation and exploring cellular mechanics within living organisms.
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Affiliation(s)
- Meng Shao
- Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, School of Instrument Science and Optoelectronics Engineering, Hefei University of Technology, Hefei 230009, China.
| | - Changxu Li
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
| | - Chun Meng
- Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, School of Instrument Science and Optoelectronics Engineering, Hefei University of Technology, Hefei 230009, China.
| | - Rui Liu
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
| | - Panpan Yu
- Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, School of Instrument Science and Optoelectronics Engineering, Hefei University of Technology, Hefei 230009, China.
| | - Fengya Lu
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
| | - Zhensheng Zhong
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
| | - Xunbin Wei
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
- Biomedical Engineering Department and Cancer Hospital and Institute, Key Laboratory of Carcinogenesis and Translational Research, Peking University, 100081, Beijing, China.
| | - Jinhua Zhou
- School of Biomedical Engineering, Anhui Medical University, Hefei, 230032, China.
| | - Min-Cheng Zhong
- Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, School of Instrument Science and Optoelectronics Engineering, Hefei University of Technology, Hefei 230009, China.
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Ross EV, Raythen J, Anderson RR. "Photon recycling" can enhance cutaneous response to lasers: A pilot human study. Lasers Surg Med 2021; 54:152-156. [PMID: 34939685 DOI: 10.1002/lsm.23505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 11/21/2021] [Accepted: 11/25/2021] [Indexed: 11/06/2022]
Abstract
BACKGROUND Depending on wavelength and pigmentation, human skin can reflect up to 70% of incident laser light. AIMS We tested the hypothesis that returning ("recycling") this diffusely reflected light to the site of laser exposure would increase cutaneous response. MATERIALS AND METHODS Thirteen adult volunteers with Fitzpatrick skin types I-IV participated in this IRB-approved study. Matched contralateral test sites on the volar forearms were exposed to a pulsed dye laser operated at 585 nm, 450 microseconds pulse duration in a uniform 5 mm circular exposure spot without skin cooling. On one arm, the laser handpiece was fitted with an aluminized hemispherical mirror with a reflectance of 67%. The minimum fluence causing skin purpura, and the purpura lesion diameter were measured. RESULTS The mean purpura threshold fluence with the reflector was 3.1 J/cm2 (0.5 SD), and 3.7 J/cm2 without the reflector (0.36 SD) (p < 0.001). The mean laser-induced purpura lesion diameter was approximately 5.3 mm with the reflector and 5.0 mm without the reflector. CONCLUSION Consistent with a theoretical model and in vitro measurements, this human study confirms that "recycling" reflected laser light can increase skin response. Potentially, the therapeutic response can also be improved with "photon recycling."
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Affiliation(s)
- Edward V Ross
- Department of Laser and Cosmetic Dermatology, Scripps Clinic, San Diego, California, USA
| | - Jill Raythen
- Department of Dermatology, Massachusetts General Hospital, Wellman Center for Photomedicine, Boston, Massachusetts, USA
| | - R Rox Anderson
- Department of Dermatology, Massachusetts General Hospital, Wellman Center for Photomedicine, Boston, Massachusetts, USA
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Zhao Y, Wang K, Li W, Zhang H, Qian Z, Liu Y. Laser speckle contrast imaging system using nanosecond pulse laser source. JOURNAL OF BIOMEDICAL OPTICS 2020; 25:1-10. [PMID: 32452171 PMCID: PMC7247735 DOI: 10.1117/1.jbo.25.5.056005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 05/13/2020] [Indexed: 06/11/2023]
Abstract
SIGNIFICANCE Nanosecond-pulsed laser has proven to be used to obtain the velocity of blood using the speckle contrast method. Without the scanning time, it has potential for achieving fast two-dimensional blood flow images in a photoacoustic imaging system with the same pulsed laser. AIM Our study aimed to evaluate the qualities of regional cerebral blood flow (rCBF) obtained in a laser speckle contrast imaging (LSCI) system using continuous wave (cw) and nanosecond pulse laser sources. APPROACH First, a LSCI system consisting of a cw laser with a wavelength of 632.8 nm and a cw laser/nanosecond pulse laser with a wavelength of 532 nm was developed. This system was used to obtain rCBF images of mouse in vivo with two different laser sources. RESULTS Continuous wave lasers (532 and 632.8 nm) show different imaging characteristics for rCBF imaging. The rCBF images obtained using 532-nm nanosecond pulse laser showed higher resolution than those using 532-nm cw laser. There was no significant difference in the results using nanosecond pulse laser among various pulse widths or repetition rates. CONCLUSIONS It is proved that a nanosecond pulse laser could be used for LSCI.
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Affiliation(s)
- Yuemei Zhao
- Nanjing University of Aeronautics and Astronautics, Department of Biomedical Engineering, Nanjing, China
| | - Kang Wang
- Nanjing University of Aeronautics and Astronautics, Department of Biomedical Engineering, Nanjing, China
| | - Weitao Li
- Nanjing University of Aeronautics and Astronautics, Department of Biomedical Engineering, Nanjing, China
| | - Huan Zhang
- Nanjing University of Aeronautics and Astronautics, Department of Biomedical Engineering, Nanjing, China
| | - Zhiyu Qian
- Nanjing University of Aeronautics and Astronautics, Department of Biomedical Engineering, Nanjing, China
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Li D, Li R, Jia H, Chen B, Wu W, Ying Z. Experimental and numerical investigation on the transient vascular thermal response to multi-pulse Nd:YAG laser. Lasers Surg Med 2017; 49:852-865. [DOI: 10.1002/lsm.22695] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2017] [Indexed: 11/10/2022]
Affiliation(s)
- Dong Li
- State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
| | - Ruohui Li
- State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
| | - Hao Jia
- State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
| | - Bin Chen
- State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
| | - Wenjuan Wu
- State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
| | - Zhaoxia Ying
- Department of Dermatology, Laser Treatment Center, Medical School; Xi'an Jiaotong University; Xi'an, Shaanxi 710049 China
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5
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Immediate skin responses to laser and light treatments. J Am Acad Dermatol 2016; 74:821-33; quiz 834, 833. [DOI: 10.1016/j.jaad.2015.06.026] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 05/29/2015] [Accepted: 06/03/2015] [Indexed: 12/17/2022]
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Moy WJ, Yakel JD, Osorio OC, Salvador J, Hayakawa C, Kelly KM, Choi B. Targeted narrowband intense pulsed light on cutaneous vasculature. Lasers Surg Med 2015; 47:651-7. [PMID: 26227344 DOI: 10.1002/lsm.22393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/22/2015] [Indexed: 11/05/2022]
Abstract
BACKGROUND AND OBJECTIVES Laser based therapies are the standard treatment protocol for port wine stain in the United States, but complete removal is infrequently achieved. Intense pulsed light (IPL) offers a broadband light spectrum approach as a viable treatment alternative. Previous studies suggest that IPL can be more effective in treatment of port wine stain by utilizing multiple wavelengths to selectively target different peaks in oxy- and deoxy-hemoglobin. Our study objectives were to (i) determine a characteristic radiant exposure able to achieve persistent vascular shutdown with narrowband IPL irradiation, (ii) determine the degree to which narrowband IPL irradiation can achieve persistent vascular shutdown, and (iii) compare the effectiveness of narrowband IPL radiation to single wavelength pulsed dye laser (PDL) irradiation in achieving persistent vascular shutdown. STUDY DESIGN/MATERIALS AND METHODS We utlized either single pulse or double, stacked pulses in narrowband IPL experiments, with the IPL operating over a 500-600 nm wavelength range on the rodent dorsal window chamber model. We compared the results from our narrowband IPL experiments to acquired PDL data from a previous study and determined that narrowband IPL treatments can also produce persistent vascular shutdown. We ran Monte Carlo simulations to investigate the relationship between absorbed energy, wavelength, and penetration depth. RESULTS For single and double pulse narrowband IPL irradiation we observed (i) little to no change in blood flow, resulting in no persistent vascular shutdown, (ii) marked acute disruption in blood flow and vascular structure, followed by partial to full recovery of blood flow, also resulting in no persistent vascular shutdown, and (iii) immediate changes in blood flow and vascular structure, resulting in prolonged and complete vascular shutdown. Monte Carlo modeling resulted in a 53.2% and 69.0% higher absorbed energy distribution in the top half and the total simulated vessel when comparing the composite narrowband IPL to the 595 nm (PDL), respectively. CONCLUSIONS Our data collectively demonstrate the potential to achieve removal of vascular lesions using a 500-600 nm range. Additionally, the narrowband IPL was tuned to optimize a specific wavelength range that can be used to treat PWS, whereas the PDL can only operate at one discrete wavelength.
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Affiliation(s)
- Wesley J Moy
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California.,Department of Biomedical Engineering, University of California, Irvine, California
| | - Joshua D Yakel
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California
| | - O Cecilia Osorio
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California
| | - Jocelynda Salvador
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California
| | - Carole Hayakawa
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California.,Department of Chemical Engineering and Materials Science, University of California, Irvine, California
| | - Kristen M Kelly
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California.,Department of Dermatology, University of California, Irvine, California.,Department of Surgery, University of California, Irvine, California
| | - Bernard Choi
- Beckman Laser Institute and Medical Clinic, University of California, Irvine, California.,Department of Biomedical Engineering, University of California, Irvine, California.,Department of Surgery, University of California, Irvine, California.,Edwards Lifesciences Center for Advanced Cardiovascular Technology, University of California, Irvine, California
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Panchaprateep R, Munavalli G. Low-fluence 585 nm Q-switched Nd:YAG laser: A novel laser treatment for post-acne erythema. Lasers Surg Med 2015; 47:148-55. [DOI: 10.1002/lsm.22321] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2014] [Indexed: 11/07/2022]
Affiliation(s)
- Ratchathorn Panchaprateep
- Division of Dermatology; Department of Medicine; King Chulalongkorn Memorial Hospital; Chulalongkorn University; Bangkok Thailand
| | - Girish Munavalli
- Dermatology, Laser and Vein Specialists of Carolinas; Charlotte; North Carolina
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Moy WJ, Patel SJ, Lertsakdadet BS, Arora RP, Nielsen KM, Kelly KM, Choi B. Preclinical in vivo evaluation of NPe6-mediated photodynamic therapy on normal vasculature. Lasers Surg Med 2012; 44:158-62. [PMID: 22334298 DOI: 10.1002/lsm.21155] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND AND OBJECTIVE Current treatments of port-wine stain birthmarks typically involve use of a pulsed dye laser (PDL) combined with cooling of the skin. Currently, PDL therapy protocols result in varied success, as some patients experience complete blanching, while others do not. Over the past decade, we have studied the use of photodynamic therapy (PDT) as either a replacement or adjuvant treatment option to photocoagulate both small and large vasculature. The objective of the current study was to evaluate a PDT protocol that involves use of an alternate intravascular photosensitizer mono-L-aspartylchlorin-e6 (NPe6) activated by an array of low-cost light emitting diodes. STUDY DESIGN/MATERIALS AND METHODS To monitor the microvasculature, a dorsal window chamber model was installed on 22 adult male mice. The light source consisted of a custom-built LED array that emitted 10 W at a center wavelength of 664 nm (FWHM = 20 nm). The light source was positioned at a fixed distance from the window chamber to achieve a fixed irradiance of 127 mW/cm(2). A retroorbital injection of NPe6 (5 mg/kg) was performed to deliver the drug into the bloodstream. Laser irradiation was initiated immediately after injection. To monitor blood-flow dynamics in response to PDT, we used laser speckle imaging. We employed a dose-response experimental design to evaluate the efficacy of NPe6-mediated PDT. RESULTS We observed three general hemodynamic responses to PDT: (1) At low radiant exposures, we did not observe any persistent vascular shutdown; (2) at intermediate radiant exposures, we observed an acute decrease in blood flow followed by gradual restoration of blood flow over the 7-day monitoring period; and (3) at high radiant exposures, we observed acute vascular shutdown that persisted during the entire 7-day monitoring period. Dose-response analysis enabled identification of 85 J/cm(2) as a characteristic radiant exposure required to achieve persistent vascular shutdown at Day 7 following PDT. CONCLUSION The experimental data suggest that NPe6-mediated PDT can achieve persistent vascular shutdown of normal microvasculature.
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Affiliation(s)
- Wesley J Moy
- Beckman Laser Institute and Medical Clinic, Department of Surgery, University of California, Irvine, California 92612, USA
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Abstract
Laser treatment of leg veins has been associated with a number of disadvantages, but the introduction of new devices has increased the role of lasers in the treatment of leg veins. This paper reviews the role of laser devices applied from the surface in the treatment of reticular and spider veins. Success is determined by the proper selection of wavelength, fluence, pulse duration, spot size, and number and frequency of treatments.
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Affiliation(s)
- Victor Ross
- Dermatology Department, Naval Medical Center, 34800 Bob Wilson Drive, San Diego, CA 92134-5000, USA.
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Ross E, Meehan K, Gilbert S, Domankevitz Y. Optimal pulse durations for the treatment of leg telangiectasias with an alexandrite laser. Lasers Surg Med 2009; 41:104-9. [DOI: 10.1002/lsm.20737] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sivarajan V, Smith G, Mackay IR. The validation of the Depth Measurement Videomicroscope (DMV) as a noninvasive tool for the assessment of capillary vascular malformations. J Plast Reconstr Aesthet Surg 2007; 60:79-86. [PMID: 17126271 DOI: 10.1016/j.bjps.2005.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2004] [Accepted: 08/31/2005] [Indexed: 11/23/2022]
Abstract
The assessment of capillary vascular malformation (CM) morphology can be performed using videomicroscopy. Previously only the type of capillary pattern could be demonstrated. The Depth Measurement Videomicroscope (DMV) allows both depth and diameter of CM vessels to be measured. The aim of this study was to examine how videomicroscope recordings correlated with biopsy recordings and to investigate pressure-related changes in recordings when using the device. For the first part of the study, 10 patients with CMs resting in a temperature-controlled room were assessed with the DMV. Following this a 3mm punch biopsy of the area was taken. The depth and diameter measurements taken with the DMV were compared to those obtained histologically. For the second part of the study, pressure measurement was used to determine the amount of pressure required on the tip of the DMV to alter the results obtained. Five recordings were taken on the forearm of one volunteer. When the DMV and biopsy measurements are compared using a Bland and Altman Test to determine their relationship there is a close agreement with the diameter measurements and a correction factor of -0.100mm for the depth measurements. The pressure required to alter the skin microcirculation when placing the DMV on the skin surface was found to be 62mmHg. This corresponds closely with other studies of pressure effects on the skin microcirculation and exceeds the pressure used when using the DMV. The DMV thus provides a useful tool for assessing CM capillary structure.
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Affiliation(s)
- Vivek Sivarajan
- Canniesburn Plastic Surgery Unit, Glasgow Royal Infirmary, Castle Street, Glasgow G4 OSF, UK.
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Kimel S, Choi B, Svaasand LO, Lotfi J, Viator JA, Nelson JS. Influence of laser wavelength and pulse duration on gas bubble formation in blood filled glass capillaries. Lasers Surg Med 2005; 36:281-8. [PMID: 15791670 DOI: 10.1002/lsm.20154] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND AND OBJECTIVES Hypervascular skin lesions (HVSL) are treated with medical lasers characterized by a variety of parameters such as wavelength lambda, pulse duration t(p), and radiant exposure E that can be adjusted for different pathology and blood vessel size. Treatment parameters have been optimized assuming constant optical properties of blood during laser photocoagulation. However, recent studies suggest that this assumption may not always be true. Our objective was to quantify thermally induced changes in blood that occur during irradiation using standard laser parameters. STUDY DESIGN/MATERIALS AND METHODS Glass capillary tubes (diameter D = 100, 200, and 337 microm) filled with fresh or hemolyzed rabbit blood were irradiated once at lambda = 585, 595, or 600 nm, t(p) = 1.5 milliseconds; and also at lambda = 585 nm, t(p) = 0.45 milliseconds. E was increased until blood ablation caused formation of permanent gas bubbles. In a corroborative study, human blood was heated at 50 degrees C and absorbance spectra were measured as a function of time. RESULTS Threshold radiant exposure, E(thresh), for gas bubble formation was found not to depend on lambda, which might be surprising in view of the 10-fold lower absorption coefficient at 600 nm as compared to 585 nm. The spectroscopic study revealed heat-induced changes in blood constituent composition of hemoglobins (Hb) from initially 100% oxyhemoglobin (HbO2) to deoxyhemoglobin (HHb) and, ultimately, methemoglobin (metHb) as the major constituent. Model calculations of E(thresh)(lambda,D) based on changing constituent blood composition during heating with milliseconds lasers were found to correlate with experimental results. CONCLUSIONS For laser treatment of HVSL it appears that lambda is of secondary importance and that the choice of t(p) is a more important factor.
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Affiliation(s)
- Sol Kimel
- Beckman Laser Institute, University of California, Irvine, California 92612, USA
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Ross EV, Domankevitz Y. Laser treatment of leg veins: Physical mechanisms and theoretical considerations. Lasers Surg Med 2005; 36:105-16. [PMID: 15704168 DOI: 10.1002/lsm.20141] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND AND OBJECTIVES A discussion of laser treatment of leg veins is based on a review of the literature, theoretical analysis, and the clinical experiences of the authors. Theoretical computations are discussed within the context of clinical observations. STUDY DESIGN/MATERIALS AND METHODS A Monte Carlo model is used to examine volumetric heat production, fluence rate, and temperature profiles in blood vessels at 1,064 and 532 nm wavelengths with various beam diameters, vessel diameters, and pulse durations. RESULTS Clinical observations, Monte Carlo results, and a review of the literature suggest that longer wavelengths and longer pulses durations favor vessel contraction over intraluminal thrombosis. Monte Carlo simulations show that longer wavelengths are more likely to uniformly heat the vessel compared to highly absorbing wavelengths. Methemoglobin production causes deeply penetrating wavelengths to generate more volumetric heat for the same input radiant exposure. CONCLUSIONS Clinical observations and models support the role of long wavelengths and long pulses in optimal clearance of most leg telangiectasias.
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Affiliation(s)
- Edward Victor Ross
- Dermatology Department, Naval Medical Center San Diego, San Diego, California 92134-2300, USA.
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Shafirstein G, Bäumler W, Lapidoth M, Ferguson S, North PE, Waner M. A new mathematical approach to the diffusion approximation theory for selective photothermolysis modeling and its implication in laser treatment of port-wine stains. Lasers Surg Med 2004; 34:335-47. [PMID: 15083495 DOI: 10.1002/lsm.20028] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND AND OBJECTIVES Monte Carlo (MC) simulations of light-tissue interactions and analytical solutions for the diffusion approximation theory have been used to determine the optimal laser wavelength and radiant exposure to treat port-wine stains (PWS). Both approaches suggest that optimal parameters are a wavelength of 585 or 595-nm with pulse times of 0.45-20 milliseconds. However, which parameters are optimal is still unclear. As differences in vessel size and in temperature distribution within vessels appeared to be the main reasons for the varied responses to the same laser treatments, we sought to develop a solution to the diffusion approximation in order to calculate temperature distribution and the resulting coagulation pattern within specific blood vessels. STUDY DESIGN/MATERIALS AND METHODS The light and heat diffusion equations were simultaneously solved with the finite element method (FEM). The latent heat of evaporation was included in the thermal analysis. The temperature and coagulation patterns across specific blood vessels, within a heterogeneous medium, were calculated for laser wavelengths of 585 and 595-nm with clinical parameters. RESULTS At 1.2 mm deep, the calculations predicted that vessels ranging from 50 to 100 microm in diameter would be coagulated from top to bottom, small vessels (10 microm) would be spared, and vessels larger than 150 microm would be partially coagulated. Coagulation across vessels was more uniform for the 595-nm than for the 585-nm wavelength. Maximal temperatures did not exceed 100 degrees C because of the inclusion of latent heat in the thermal calculations. CONCLUSIONS To study laser treatments of PWS with the diffusion approximation, FEM is an effective method to calculate the coagulation patterns within specific blood vessels. To improve coagulation efficacy at 585 and 595-nm wavelengths, the radiant exposure should be increased without increasing the irradiance.
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Affiliation(s)
- Gal Shafirstein
- Vascular Anomalies Center, Arkansas Children's Hospital and University of Arkansas for Medical Sciences, Little Rock, Arkansas 72202, USA.
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Suthamjariya K, Farinelli WA, Koh W, Anderson RR. Mechanisms of Microvascular Response to Laser Pulses. J Invest Dermatol 2004; 122:518-25. [PMID: 15009739 DOI: 10.1046/j.0022-202x.2004.22241.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
"Selective photothermolysis" is widely used for treating vascular lesions. In order to understand mechanisms of response, we investigated fast events during pulsed laser treatment of microvessels. A high-speed (2000 fps) CCD camera and microscope were used to image hamster cheek pouch microvessels during and after 532 nm and 1064 nm laser pulse exposures. Pulse duration and fluence were varied systematically (1-50 ms, 0-600 J per cm2). Threshold fluences for fast events were determined. On a millisecond time-scale, a specific series of fast events occur, which are wavelength, fluence, irradiance, and pulse duration dependent. In order of increasing fluence we observed: blood coagulation, vasoconstriction, thread-like appearance of the treated vascular segment, vessel disappearance, intravascular cavitation, bubble formation, vessel wall rupture and hemorrhage, and shrinkage of perivascular tissue. With increasing pulse duration, the threshold fluences for coagulation, vessel disappearance, and cavitation increase, and cavitation becomes less violent, conforming to the vessel lumen. Intravascular cavitation did not always rupture the vessel wall, and is not the mechanism for immediate vessel disappearance, a desired endpoint for treating vascular lesions. The apparent mechanism for immediate vessel disappearance is contraction of intravascular blood and perivascular collagen after thermal denaturation. This study suggests that detecting fast events in humans, in real time, may provide useful feedback signals for "smarter" laser devices.
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Affiliation(s)
- Kittisak Suthamjariya
- Wellman Laboratories of Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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Verkruysse W, Beek JF, VanBavel E, van Gemert MJ, Spaan JA. Laser pulse impact on rat mesenteric blood vessels in relation to laser treatment of port wine stain. Lasers Surg Med 2001; 28:461-8. [PMID: 11413559 DOI: 10.1002/lsm.1075] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND OBJECTIVE To study the impact of laser pulses on animal microvasculature as a model for laser treatment of port wine stains. STUDY DESIGN/MATERIALS AND METHODS Rat mesenteric blood vessels were irradiated with a laser pulse (585 nm, 0.2-0.6 ms pulse duration, 0.5-30 J/cm(2) radiant exposure). Video microscopy was used to assess vessel dilation, formation of intravascular thrombi, bubble formation, and vessel rupture. Changes in reflection during a laser pulse were measured by simultaneously recording the temporal behavior of the incident and reflected signals. RESULTS A threshold radiant exposure of approximately 3 J/cm(2) was found for changes in optical properties of blood in vivo, confirming previous in vitro results. Often, laser exposure induced a significant increase in vessel diameter, up to three times the initial diameter for venules and four times for arterioles, within 200 ms after laser exposure. Arterioles were more likely to dilate than venules. Sometimes, immediately after the pulse, round structures, interpreted as being gas bubbles, were seen within the vessel lumen. CONCLUSIONS A variety of phenomena can occur when blood vessels of sizes comparable to those in port wine stains are irradiated with laser pulses as used in port wine stain treatment. Thrombus formation and vessel rupture have been described before from histological sections of laser-irradiated port wine stains. However, vessel dilation and formation of non-transient gas bubbles as found in this study have not been described before.
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Affiliation(s)
- W Verkruysse
- Laser Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Abstract
The current status and challenges of small animal non-invasive imaging is briefly reviewed. The advantages of non-invasive studies on living animals versus post-mortem studies are evaluated. An argument is advanced that even in post-mortem situations, non-invasive imaging may play an important role in efficiently characterizing small animal phenotypes as well as pathology. Issues of data interpretation under anesthetized conditions in live animal studies are also reviewed. The five imaging technologies covered include CT, PET, ultrasound, MRI and optical imaging. The structural and physiological information content of these different modalities is reviewed along with the ability of these techniques to scale down for use in small mammals such as mice and rats. In general, it was found that most of these technologies scale favorably to the study of small mammals, generally providing more physiological information than when used on the larger human scale. This suggests that these types of small mammal imaging capabilities will play a very significant role in the full utilization of these important animal models in biomedical research.
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Affiliation(s)
- R S Balaban
- Laboratory Research Program, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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Loze MK, Wright CD. Temperature distributions in laser-heated biological tissue with application to birthmark removal. JOURNAL OF BIOMEDICAL OPTICS 2001; 6:74-85. [PMID: 11178583 DOI: 10.1117/1.1318217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/1999] [Revised: 08/18/2000] [Accepted: 08/21/2000] [Indexed: 05/23/2023]
Abstract
The time-dependent temperature distributions produced within thermally homogeneous media heated by a moving laser beam with Gaussian and uniform power density profiles are examined using a time-domain method based on Green's functions. Regions of finite length, width, and depth within the medium having exponential power absorption are considered. The temperature distribution is written as a single integral with respect to time of simple functions and the resulting expressions have been used to model the heating of blood vessels for birthmark (port-wine stain) removal. The temperature distributions obtained are in good agreement with those produced using Monte Carlo optical and finite difference thermal models.
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Affiliation(s)
- M K Loze
- University of Exeter, School of Engineering and Computer Science, United Kingdom
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