Optical phantom materials for near infrared laser photocoagulation studies

Iizuka, Megumi; Sherar, Michael D.; Vitkin, I. Alex

doi:10.1002/(sici)1096-9101(1999)25:2<159::aid-lsm10>3.0.co;2-v

Cited by 73 publications

(77 citation statements)

References 22 publications

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“…Measurements and calculations have been made for solder samples in a coagulated state only because solder solutions are virtually not scattering and the absorption coefficient is not expected to change significantly. 10 For the phantom the natural and coagulated states have been investigated since scattering occurs in both states.…”

Section: Optical Propertiesmentioning

confidence: 99%

Two-wavelength approach for control of coagulation depth during laser tissue soldering

et al. 2015

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In laser tissue soldering (LTS) protein solutions are used for closing of incisions or fixation of wound dressings. During coagulation and thermal denaturation of the protein solutions their morphology changes significantly such that light is strongly scattered. When scattering becomes major component extinction increases and the optical penetration depth shrinks which could lead to unsufficient coagulation and bonding. For adaption of extinction during coagulation we are investigating a two- wavelength approach. A strongly absorbed laser wavelength (1540 nm) and weakly absorbed wavelength (980 nm) can be applied simultaneously. Simulation of beam propagation is performed in natural and coagulated state of the solder. The model describes a three- layer system consisting of membrane, solder and phantom. The optical properties are determined by spectrometric measurements both in natural and coagulated state. The absorption coefficient mu(s), scattering coefficient mu(s) and anisotropy factor. are determined by numerical analysis from the spectrometric data. Beam propagation is simulated for 980 nm and 1540 nm radiation with ZEMAX r software based on the Monte Carlo method. For both wavelengths the beginning of the process with a clear solder layer, and the final state characterized by a coagulated solder layer are examined. The optical penetration depth depends mainly on the optical properties of the solder, which change in the course of coagulation process. The coagulation depth can be varied between 1.5 mm to 3.5 mm by changing the proportion of both laser sources. This leads to concepts for minimizing heat input while maintaining a constant coagulation depth

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Section: Optical Propertiesmentioning

confidence: 99%

Two-wavelength approach for control of coagulation depth during laser tissue soldering

et al. 2015

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“…A 2-cm cylindrical diffuser (Photoglow, Yarmouth, MA) was used to locally heat samples of temperature-sensitive albumen phantoms constructed according to a recipe developed by Iizuka et al (1999). The albumen-based phantom was chosen due to its demonstrated utility as a tissue-mimicking material for laser irradiation [7].…”

Section: B Laser Heating Experimentsmentioning

confidence: 99%

“…The albumen-based phantom was chosen due to its demonstrated utility as a tissue-mimicking material for laser irradiation [7]. The laser fiber was operated at a power of 7 Watts to conduct three similar laser heating experiments with the albumen phantom for heating periods of approximately 20 minutes.…”

Section: B Laser Heating Experimentsmentioning

confidence: 99%

P3D-3 Transmission Ultrasound Imaging to Guide Thermal Therapy

Soleimankhani

Kolios

2007

2007 IEEE Ultrasonics Symposium Proceedings

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Minimally Invasive Thermal Therapy (MITT) is an effective way to destroy diseased tissue and could replace surgery, chemotherapy or radiation. During MITT, temperatures in the range of 55-95 • C are produced locally, resulting in tissue coagulation. A real-time imaging method is required to prevent damage to the nearby normal tissue during heating and to visualize the changes in size and shape of the diseased tissue. It is known that acoustic attenuation is sensitive to both the tissue temperature and the structural changes during thermal therapy. This work examines the potential of ultrasound attenuation imaging during MITT to quantitatively monitor lesion formation dynamics. A transmission ultrasound camera (AcoustoCam, Imperium Inc., Silver Spring, MD) was used to collect acoustic images. The AcoustoCam was initially calibrated using a set of 10 PVCP (Polyvinyl Chloride Plastisol) tissue-mimicking phantoms. The attenuation values were measured by an insertion technique and found to be in the range of 2.18-26.46 dB at a frequency of 4.76 MHz. The 8 bit mean pixel intensity displayed on the screen, and 14 bit mean pixel intensity from the camera's sensor were extracted. A laser fiber (2 cm long cylindrical diffuser, Photoglow, Yarmouth, MA) was used to locally heat albumen temperaturesensitive phantoms and bovine liver tissue. The 8 bit mean pixel intensity as well as temperature were recorded for the heating and cooling periods every two seconds in a region close to the laser fiber. The relationship between the AcoustoCam mean pixel intensity and acoustic attenuation was established. Heating the agar-albumen phantoms and bovine liver tissue increased the local temperature and resulted in an ellipsoidal lesion. In all heating experiments an initial rapid attenuation decrease at low temperatures was followed by a gradual increase in attenuation as temperature increased. During the cooling procedure, attenuation increased rapidly until it reached a steady state, and remained at an attenuation value greater than the value when no thermal lesion was present within the sample. The initial attenuation decrease and the final attenuation increase are reversible and are hypothesized to be a temperature effect, while the gradual change in attenuation at higher temperatures is assumed to be due to protein coagulation. In summary, it was shown that the acoustic camera could monitor in real time the dynamics of lesion formation and that the attenuation profile during heating follows a reproducible pattern.

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“…Naphthol Green is an effective absorber for the short near infrared (NIR) light (700-850nm), which is highly watersoluble and introduces minimal scattering in the solution [12] . Intralipid is often used as a scattering agent in tissue models.…”

Section: Absorption Coefficients Measured By the Oct System 321 Liqmentioning

confidence: 99%

In-vitro imaging of bone tissue and monitoring of tissue viability by optical coherence tomography

Wang

Haj

2001

SPIE Proceedings

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Optical coherence tomography (OCT) has developed as a promising medical diagnostic imaging technology for noninvasive in situ cross-sectional imaging of biological tissues. We present this technique to image bone tissue and to monitor the redox state of mitochondria enzyme Cytochrome oxidase (CytOx) in bone for applications in tissue engineering. Superluminescent diode (SLD) with its peak emission wavelength (λ = 820nm) on the absorption band of oxidized form of CytOx was used in the experiments. The results demonstrate that the OCT system is capable of imaging the calvaria of newborn rats tomographically with a resolution at 9 microns, which could only be previously obtained by the conventional excisional biopsy. The thickness of periosteum of various calvarias from different ages of rats can be accurately determined by the system.The backscattered power-versus-depth profile from the liquid phantoms (naphthol green B with intralipid) and tissue specimens (periosteum of calvaria from newborn rats) are used to quantify the absorption changes of the sample. Absorption coefficients of naphthol green B could be quantified accurately by the linear relationship between attenuation coefficients from the slopes of the reflected signals and naphthol green B concentration. The results also show that the attenuation coefficient decreases in periosteums as CytOx being reduced by sodium dithionite, demonstrating the feasibility of this method to monitor the redox state of tissues studied.

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Optical phantom materials for near infrared laser photocoagulation studies

Cited by 73 publications

References 22 publications

Two-wavelength approach for control of coagulation depth during laser tissue soldering

Two-wavelength approach for control of coagulation depth during laser tissue soldering

P3D-3 Transmission Ultrasound Imaging to Guide Thermal Therapy

In-vitro imaging of bone tissue and monitoring of tissue viability by optical coherence tomography

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