Temperature measurement on tissue surface during laser irradiation

Effect of gold nanoparticles distribution radius on photothermal therapy efficacy

Lasers are used in various fields, however, in the medical field, they are mainly used for incision or chemotherapy. Photothermal therapy (PTT) is an anti-cancer treatment technique that uses lasers and the photothermal effect to increase the temperature of tumor tissue and induce its death. In this study, the therapeutic effect of PTT using gold nanoparticles as a photothermal converter was analyzed numerically for the occurrence of squamous cell carcinoma inside a skin section consisting four layers. Numerical modeling was implemented to calculate the temperature distribution inside the biological tissue while varying the distribution radius of gold nanoparticles in the tumor tissue, the number of injections, and the intensity of the irradiating laser. For the given situation, the optimal treatment effect was observed when the distribution radius ratio of the injected gold nanoparticles (GNPs) was 1, the number of injections was 7, and the intensity of the irradiated laser was 52 mW. Three apoptotic variables were used to quantitively evaluate the effect of PTT in each case and thus suggest the optimal treatment effect. However, although the temperature range at which apoptosis occurs is known, the maintenance of that temperature range is still under research and the temporal influence of apoptosis remains to be determined.

Antigen presentation and interferon signatures in B cells driven by localized ablative cancer immunotherapy correlate with extended survival

Rationale: B cells have emerged as key regulators in protective cancer immunity. However, the activation pathways induced in B cells during effective immunotherapy are not well understood. Methods: We used a novel localized ablative immunotherapy (LAIT), combining photothermal therapy (PTT) with intra-tumor delivery of the immunostimulant N-dihydrogalactochitosan (GC), to treat mice bearing mouse mammary tumor virus-polyoma middle tumor-antigen (MMTV-PyMT). We used single-cell RNA sequencing to compare the transcriptional changes induced by PTT, GC and PTT+GC in B cells within the tumor microenvironment (TME). Results: LAIT significantly increased survival in the tumor-bearing mice, compared to the treatment by PTT and GC alone. We found that PTT, GC and PTT+GC increased the proportion of tumor-infiltrating B cells and induced gene expression signatures associated with B cell activation. Both GC and PTT+GC elevated gene expression associated with antigen presentation, whereas GC elevated transcripts that regulate B cell activation and GTPase function and PTT+GC induced interferon response genes. Trajectory analysis, where B cells were organized according to pseudotime progression, revealed that both GC and PTT+GC induced the differentiation of B cells from a resting state towards an effector phenotype. The analyses confirmed upregulated interferon signatures in the differentiated tumor-infiltrating B cells following treatment by PTT+GC but not by GC. We also observed that breast cancer patients had significantly longer survival time if they had elevated expression of genes in B cells that were induced by PTT+GC therapy in the mouse tumors. Conclusion: Our findings show that the combination of local ablation and local application of immunostimulant initiates the activation of interferon signatures and antigen-presentation in B cells which is associated with positive clinical outcomes for breast cancer. These findings broaden our understanding of LAIT's regulatory roles in remodeling TME and shed light on the potentials of B cell activation in clinical applications.

Numerical Simulation of Enhancement of Superficial Tumor Laser Hyperthermia with Silicon Nanoparticles

Biodegradable and low-toxic silicon nanoparticles (SiNPs) have potential in different biomedical applications. Previous experimental studies revealed the efficiency of some types of SiNPs in tumor hyperthermia. To analyse the feasibility of employing SiNPs produced by the laser ablation of silicon nanowire arrays in water and ethanol as agents for laser tumor hyperthermia, we numerically simulated effects of heating a millimeter-size nodal basal-cell carcinoma with embedded nanoparticles by continuous-wave laser radiation at 633 nm. Based on scanning electron microscopy data for the synthesized SiNPs size distributions, we used Mie theory to calculate their optical properties and carried out Monte Carlo simulations of light absorption inside the tumor, with and without the embedded nanoparticles, followed by an evaluation of local temperature increase based on the bioheat transfer equation. Given the same mass concentration, SiNPs obtained by the laser ablation of silicon nanowires in ethanol (eSiNPs) are characterized by smaller absorption and scattering coefficients compared to those synthesized in water (wSiNPs). In contrast, wSiNPs embedded in the tumor provide a lower overall temperature increase than eSiNPs due to the effect of shielding the laser irradiation by the highly absorbing wSiNPs-containing region at the top of the tumor. Effective tumor hyperthermia (temperature increase above 42 °C) can be performed with eSiNPs at nanoparticle mass concentrations of 3 mg/mL and higher, provided that the neighboring healthy tissues remain underheated at the applied irradiation power. The use of a laser beam with the diameter fitting the size of the tumor allows to obtain a higher temperature contrast between the tumor and surrounding normal tissues compared to the case when the beam diameter exceeds the tumor size at the comparable power.

Multi-Lens Arrays (MLA)-Assisted Photothermal Effects for Enhanced Fractional Cancer Treatment: Computational and Experimental Validations

Simple Summary

Colorectal cancer is one of the most common cancers and the third leading cause of cancer-related deaths in the United States. As a non- or minimally invasive cancer treatment, photothermal therapy (PTT) has been widely used to generate irreversible thermal injuries in tumors. However, conventional PTT employs an end-firing flat fiber to deliver laser energy, leading to the incomplete removal of tumor tissues due to an uneven beam distribution over the tumor surface. Multi-lens arrays (MLA) generate multiple micro-beams to uniformly distribute laser energy on the tissue surface. Therefore, the application of MLA for PTT in cancer affords a spatially enhanced distribution of micro-beams and laser-induced temperature in the tumor. The purpose of the current study is to computationally and experimentally demonstrate the therapeutic benefits of MLA-assisted fractional PTT on colorectal cancer, in comparison to flat fiber-based PTT.

Abstract

Conventional photothermal therapy (PTT) for cancer typically employs an end-firing flat fiber (Flat) to deliver laser energy, leading to the incomplete treatment of target cells due to a Gaussian-shaped non-uniform beam profile. The purpose of the current study is to evaluate the feasibility of multi-lens arrays (MLA) for enhanced PTT by delivering laser light in a fractional micro-beam pattern. Computational and experimental evaluations compare the photothermal responses of gelatin phantoms and aqueous dye solutions to irradiations with Flat and MLA. In vivo colon cancer models have been developed to validate the therapeutic capacity of MLA-assisted irradiation. MLA yields 1.6-fold wider and 1.9-fold deeper temperature development in the gelatin phantom than Flat, and temperature monitoring identified the optimal treatment condition at an irradiance of 2 W/cm² for 180 s. In vivo tests showed that the MLA group was accompanied by complete tumor eradication, whereas the Flat group yielded incomplete removal and significant tumor regrowth 14 days after PTT. The proposed MLA-assisted PTT spatially augments photothermal effects with the fractional micro-beams on the tumor and helps achieve complete tumor removal without recurrence. Further investigations are expected to optimize treatment conditions with various wavelengths and photosensitizers to warrant treatment efficacy and safety for clinical translation.

Mathematical modeling and experimental validation for expression microdissection

Using laser excitation, expression microdissection (xMD) can selectively heat cancer cells targeted via immunohistochemical staining to enable their selective retrieval from tumor tissue samples, thus reducing misdiagnoses caused by contamination of noncancerous cells. Several theoretical models have been validated for the photothermal effect in highly light absorbing and scattering media. However, these models are not generally applicable to the physics behind the process of xMD. In this study, we propose a thermal model that can analyze the transient temperature distribution and heat melt zone in an xMD sample medium composed of a thermoplastic film and a tumor tissue sample sandwiched between two glass slides. Furthermore, we experimentally examined the model using an ink layer with controllable optical properties to serve as a microscale-thin, tissue-mimicking phantom and found the experimentally measured film temperature is in good agreement with the model predictions. The validated model can help researchers to optimize cell retrieval by xMD for improved diagnostics of cancer and other diseases.

Mathematical simulation of temperature distribution in tumor tissue and surrounding healthy tissue treated by laser combined with indocyanine green

Background

Photothermal therapy is a local treatment method for cancer and the heat energy generated from it could destroy the tumor cells. This study is aimed to investigate the temperature distribution in tumor tissue and surrounding health tissue of tumor bearing mice applying mathematical simulation model. Tumor bearing mice treated by laser combined with or without indocyanine green. Monte Carlo method and the Pennes bio-heat equation were used to calculate the light distribution and heat energy. COMSOL Multiphysic was adopted to construct three dimensional temperature distribution model.

Results

This study revealed that the data calculated by simulation model is in good agreement with the surface temperature monitored by infrared thermometer. Effected by the optical parameters and boundary conditions of tissue, the highest temperature of tissue treated by laser combined with indocyanine green was about 65 °C which located in tumor tissue and the highest temperature of tissue treated by laser was about 43 °C which located under the tumor tissue. The temperature difference was about 20 °C. Temperature distribution in tissue was not uniform. The temperature difference in different parts of tumor tissue raised up to 15 °C. The temperature of tumor tissue treated by laser combined with indocyanine green was about 20 °C higher than that of the surrounding healthy tissue.

Conclusions

Reasonably good matching between the calculated temperature and the measured temperature was achieved, thus demonstrated great utility of our modeling method and approaches for deepening understand in the temperature distribution in tumor tissue and surrounding healthy tissue during the laser combined with photosensitizer. The simulation model could provide guidance and reference function for the effect of photothermal therapy.

Electronic supplementary material

The online version of this article (10.1186/s12976-019-0107-3) contains supplementary material, which is available to authorized users.

Characteristics of temperature changes in photothermal therapy induced by combined application of indocyanine green and laser

Photothermal therapy, a type of laser application, has the ability to eradicate tumor cells by a local thermal effect and elicit a tumor specific immune response. Indocyanine green (ICG), a photosensitizer, can effectively elevate the local temperature by absorbing energy from the laser. The present study aimed to investigate the characteristics of temperature changes during photothermal therapy with an infrared thermometer in an ICG solution and in tumor-bearing mice treated with a combination of laser and ICG. Additionally, the present study observed the morphological changes of tumor tissue by hematoxylin-eosin staining following photothermal therapy. In the solution experiment, when the laser power density was 1 W/cm² and the concentration of ICG was 0 or 0.0187 mg/ml, the temperature of the water was elevated by 3 and 28°C, respectively. In the tumor-bearing mice experiment, when the laser power density was 1 W/cm² and the concentration of ICG was 0 and 0.1 mg/ml, the temperature of the tumor-bearing mice was elevated by 6.9 and 28.5°C, respectively. With an increase in laser power density, including 0.6, 0.8 and 1.0 W/cm², the temperature was 23.3, 26.7 and 28.5°C, respectively. Pathological tissue sections demonstrated that a large number of tumor cells experienced necrosis, and the envelope of the tumor was destroyed. Numerous inflammatory cells, in particular lymphocytes, infiltrated into the tumor tissue following tumor tissue treatment with a combination of laser and ICG. These results indicated that a combination treatment with laser and ICG may significantly increase the temperature of the water solutions and in the tumor-bearing mice. The concentration of ICG and laser power density contributed to the temperature elevation, in particular to the concentration of ICG.

Thermal Image Enhancement through the Deconvolution Methods for Low-Cost Infrared Cameras

An infrared (IR) thermal camera may provide a tool for real-time temperature monitoring for precise disease treatment using heat generated by light-induced photosensitisers, i.e. photothermal/ablation therapies. In this work, we quantitatively demonstrated that the spatial resolution of a low-cost low-resolution IR camera could be improved via two deconvolution methods. The camera point spread function (PSF) was modeled experimentally and used to develop the deconvolution methods: 1) Richardson-Lucy blind deconvolution (BD); and 2) total variation constrained deconvolution (TD). The experimental results showed the improved spatial resolution (at 50% modulation transfer function (MTF): from the original 1.1 cycles/mm to 2.6 cycles/mm for the BD method and to 4.8 cycles/mm for the TD method) as well as contrast-to-noise ratio. With a properly chosen parameter, the TD method can resolve 1-mm size objects with the accurate temperature reading. The thermal image from the low-resolution IR camera enhanced by the TD method is comparable to that from a high-resolution IR camera. These results show that the TD method provides an effective way to improve the thermal image quality from a low-cost IR camera to monitor temperature of an object of 1-mm size, which meets the needed precision for advanced laser scanning protocols in photothermal/ablation therapies.

Low-level laser therapy to recovery testicular degeneration in rams: effects on seminal characteristics, scrotal temperature, plasma testosterone concentration, and testes histopathology

The aim of this study was to investigate the efficiency of low-level laser therapy (LLLT) to recovery testicular degeneration in rams. In the first study, rams were induced to testicular degeneration by scrotal insulation, and then, they were treated using LLLT at 28 J/cm(2) (INS28) or 56 J/cm(2) (INS56) energy densities. Sperm kinetics, morphology, and membranes integrity as well as proportion of lumen area in seminiferous tubule were assessed. In the second study, rams were submitted or not to scrotal insulation and treated or not by the best protocol of LLLT defined by experiment 1 (INS28). In this study were evaluated sperm kinetics, morphology, membranes integrity, ROS production, and DNA integrity. Testosterone serum concentration and proportion of lumen area in seminiferous tubule were also analyzed. Insulation was effective in promoting sperm injuries in both experiments. Biostimulatory effect was observed in experiment 1: INS28 presented smaller proportion of lumen area (P = 0.0001) and less degeneration degree (P = 0.0002). However, in experiment 2, there was no difference between the groups (P = 0.17). In addition, LLLT did not improve sperm quality, and there was a decreasing for total and progressive motility (P = 0.02) and integrity of sperm membranes (P = 0.01) in LLLT-treated groups. Moreover, testosterone concentration was not improved by LLLT (P = 0.37). Stimulation of aerobic phosphorylation by LLLT may have led to a deregulated increase in ROS leading to sperm damages. Thus, LLLT at energy of 28 J/cm(2) (808 nm of wavelength and 30 mW of power output) can induce sperm damages and increase the quantity of cells in seminiferous tubule in rams.

Carbon nanotubes in hyperthermia therapy

Thermal tumor ablation therapies are being developed with a variety of nanomaterials, including single- and multiwalled carbon nanotubes. Carbon nanotubes (CNTs) have attracted interest due to their potential for simultaneous imaging and therapy. In this review, we highlight in vivo applications of carbon nanotube-mediated thermal therapy (CNMTT) and examine the rationale for use of this treatment in recurrent tumors or those resistant to conventional cancer therapies. Additionally, we discuss strategies to localize and enhance the cancer selectivity of this treatment and briefly examine issues relating the toxicity and long term fate of CNTs.

Supervisory system for robot assisted laser phonomicrosurgery

This paper presents the development of a system capable of generating safety alarms when unexpected or unforeseen situations are detected during larynx phonomicrosurgery. Such system establishes relations between the application of laser power and changes in laryngeal tissue characteristics and appearance. As core component, we propose a model able to map inputs generated by the surgeon when controlling the laser to an estimation of tissue temperature. Situations where this supervision is relevant have been identified.

A noninvasive, remote and precise method for temperature and concentration estimation using magnetic nanoparticles

This study describes an approach for remote measuring of on-site temperature and particle concentration using magnetic nanoparticles (MNPs) via simulation and also experimentally. The sensor model indicates that under different applied magnetic fields, the magnetization equation of the MNPs can be discretized to give a higher-order nonlinear equation in two variables that consequently separates information regarding temperature and particle concentration. As a result, on-site tissue temperature or nanoparticle concentration can be determined using remote detection of the magnetization. In order to address key issues in the higher-order equation we propose a new solution method of the first-order model from the perspective of the generalized inverse matrix. Simulations for solving the equation, as well as to optimize the solution of higher equations, were carried out. In the final section we describe a prototype experiment used to investigate the measurement of the temperature in which we used a superconducting magnetometer and commercial MNPs. The overall error after nine repeated measurements was found to be less than 0.57 K within 310-350 K, with a corresponding root mean square of less than 0.55 K. A linear relationship was also found between the estimated concentration of MNPs and the sample's mass.

Assessment of thermal effects of interstitial laser phototherapy on mammary tumors using proton resonance frequency method

Laser immunotherapy (LIT) uses a synergistic approach to treat cancer systemically through local laser irradiation and immunological stimulation. Currently, LIT utilizes dye-assisted noninvasive laser irradiation to achieve selective photothermal interaction. However, LIT faces difficulties treating deeper tumors or tumors with heavily pigmented overlying skin. To circumvent these barriers, we use interstitial laser irradiation to induce the desired photothermal effects. The purpose of this study is to analyze the thermal effects of interstitial irradiation using proton resonance frequency (PRF). An 805-nm near-infrared laser with an interstitial cylindrical diffuser was used to treat rat mammary tumors. Different power settings (1.0, 1.25, and 1.5 W) were applied with an irradiation duration of 10 min. The temperature distributions of the treated tumors were measured by a 7 T magnetic resonance imager using PRF. We found that temperature distributions in tissue depended on both laser power and time settings, and that variance in tissue composition has a major influence in temperature elevation. The temperature elevations measured during interstitial laser irradiation by PRF and thermocouple were consistent, with some variations due to tissue composition and the positioning of the thermocouple's needle probes. Our results indicated that, for a tissue irradiation of 10 min, the elevation of rat tumor temperature ranged from 8 to 11°C for 1 W and 8 to 15°C for 1.5 W. This is the first time a 7 T magnetic resonance imager has been used to monitor interstitial laser irradiation via PRF. Our work provides a basic understanding of the photothermal interaction needed to control the thermal damage inside a tumor using interstitial laser treatment. Our work may lead to an optimal protocol for future cancer treatment using interstitial phototherapy in conjunction with immunotherapy.

Development of iron-containing multiwalled carbon nanotubes for MR-guided laser-induced thermotherapy

AIMS

To test iron-containing multiwalled carbon nanotubes (MWCNTs) as bifunctional nanomaterials for imaging and thermal ablation of tumors.

MATERIALS & METHODS

MWCNTs entrapping iron were synthesized by chemical vapor deposition. The T2-weighted contrast enhancement properties of MWCNTs containing increasing amounts of iron were determined in vitro. Suspensions of these particles were injected into tumor-bearing mice and tracked longitudinally over 7 days by MRI. Heat-generating abilities of these nanomaterials following exposure to near infrared (NIR) laser irradiation was determined in vitro and in vivo.

RESULTS

The magnetic resonance contrast properties of carbon nanotubes were directly related to their iron content. Iron-containing nanotubes were functional T2-weighted contrast agents in vitro and could be imaged in vivo long-term following injection. Iron content of nanotubes did not affect their ability to generate thermoablative temperatures following exposure to NIR and significant tumor regression was observed in mice treated with MWCNTs and NIR laser irradiation.

CONCLUSION

These data demonstrate that iron-containing MWCNTs are functional T2-weighted contrast agents and efficient mediators of tumor-specific thermal ablation in vivo.

Temperature increase in porcine cadaver iris during direct illumination by femtosecond laser pulses

PURPOSE

To measure the temperature rise in porcine cadaver iris during direct illumination by the femtosecond laser as a model for laser exposure of the iris during femtosecond laser corneal surgery.

SETTING

Department of Ophthalmology, University of California-Irvine, Irvine, California, USA.

DESIGN

Experimental study.

METHODS

The temperature increase induced by a 60 kHz commercial femtosecond laser in porcine cadaver iris was measured in situ using an infrared thermal imaging camera at pulse energy levels ranging from 1 to 2 μJ (corresponding approximately to surgical energies of 2 to 4 μJ per laser pulse).

RESULTS

Temperature increases up to 2.3 °C (corresponding to 2 μJ and 24-second illumination) were observed in the porcine cadaver iris with little variation in temperature profiles between specimens for the same laser energy illumination.

CONCLUSIONS

The 60 kHz commercial femtosecond laser operating with pulse energies at approximately the lower limit of the range evaluated in this study would be expected to result in a 1.2 °C temperature increase and therefore does not present a safety hazard to the iris.

Preclinical assessment of a 980-nm diode laser ablation system in a large animal tumor model

PURPOSE

To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model.

MATERIALS AND METHODS

This study was approved by the institutional animal care and use committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing-tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine-transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) at powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator tract, measured, and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed with hematoxylin and eosin and nicotinamide adenine dinucleotide hydrogen staining.

RESULTS

Gross pathologic examination confirmed a well circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 seconds) to 26 mm at the highest dose (15 W, 180 seconds). Multiple applicators created ablation zones as large as 42 mm in greatest diameter (with the lasers operating at 15 W for 120 seconds).

CONCLUSIONS

The new 980-nm diode laser and internally cooled applicator effectively create large ellipsoid thermal ablations in less than 3 minutes.

Temperature increase in human cadaver retina during direct illumination by femtosecond laser pulses

PURPOSE

Femtosecond lasers have been approved by the US Food and Drug Administration for ophthalmic surgery, including use in creating corneal flaps in LASIK surgery. During normal operation, approximately 50% to 60% of laser energy may pass beyond the cornea, with potential effects on the retina. As a model for retinal laser exposure during femtosecond corneal surgery, we measured the temperature rise in human cadaver retinas during direct illumination by the laser.

METHODS

The temperature increase induced by a 150-kHz iFS Advanced Femtosecond Laser (Abbott Medical Optics) in human cadaver retinas was measured in situ using an infrared thermal imaging camera. To model the geometry of the eye during the surgery, an approximate 11x11-mm excised section of human cadaver retina was placed 17 mm behind the focus of the laser beam. The temperature field was observed in 10 cadaver retina samples at energy levels ranging from 0.4 to 1.6 microJ (corresponding approximately to surgical energies of 0.8 to 3.2 microJ per pulse).

RESULTS

Maximal temperature increases up to 1.15 degrees C (corresponding to 3.2 microJ and 52-second illumination) were observed in the cadaver retina sections with little variation in temperature profiles between specimens for the same laser energy illumination.

CONCLUSIONS

The commercial iFS Advanced Femtosecond Laser operating with pulse energies at approximately the lower limit of the range evaluated in this study would be expected to result in a 0.2 degrees C temperature increase and do not therefore present a safety hazard to the retina.

Multilayer imaging and compositional analysis of human male breast by laser reflectometry and Monte Carlo simulation

The laser backscattering from biological tissues depends on their composition and blood flow. The onset of abnormalities in tissues is associated with the change in composition at a specific location which may affect laser backscattering. The objective of this work is to study the point-to-point compositional variation of male breast tissues as this site has been prone to cancer development. The normalized backscattered intensity (NBI) profiles at various locations of human chest region of five subjects by multi-probe laser reflectometer are obtained. Based on these data the images of tissue composition, showing the point-to-point changes at various depths from the tissue surface, are reconstructed. The analysis of data shows that the maximum NBI variation is at the pectoralis major muscle and minimum variation is observed at the sternum. The optical parameters, based on the NBI data obtained for five human subjects, show the maximum increase in absorption (p < 0.0001) and minimum change in scattering (p < 0.0001) coefficients compared to that as observed at the sternum. Also the minimum absorption and maximum scattering coefficients are observed at the pectoralis major muscles. The regional variations of NBI and optical parameters further support these findings. The variations in the NBI and optical parameters may indicate the compositional change in tissues, which could be used for diagnostic and therapeutic applications of laser.