The authors thank Mr. Kenta Yamada, Mr. Ryota Fujioka, and Mr. Mizuki Kyoda for their support on the experiments and data analyses. This work was supported by JSPS KAKENHI Grant Number 25630069, the Suzuki Foundation, and the Precise Measurement Technology Promotion Foundation, Japan.

1. Experimental Setup and Procedures
Prepare an optical rail to mount a sample and optics for NIR imaging as follows.
<ol>
	<li>Sample preparation. 
	Note: When using water or aqueous liquid, do Step 1.1.1. When using an aqueous gel with high viscosity, do Step 1.1.2.
	<ol>
		<li>Steel sphere setting in water.
		<ol>
			<li>Fix a 2.0-mm-diameter steel sphere to the end of a thin plastic string using a small amount of glue.</li>
			<li>Hang the steel sphere at the center...

<ol>
	<li>Moros, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Physics of Thermal Therapy. , (2012).</li><li>P&#233;rigo, E. G., Hemery, G., Sandre, O., Ortega, D., Garaio, E., Plazaola, F., Teran, F. 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O., Kvalheim, O. M., Christy, A. A., Toft, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectra+of+water+in+the+near-+and+mid-infrared+region.">Spectra of water in the near- and mid-infrared region.</a> Vib Spectrosc. 7, 243-254 (1994).</li><li>Siesler, H. W., Ozaki, Y., Kawata, S., Heise, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Near-Infared Spectroscopy. , (2002).</li><li>Shakher, C., Nirala, A. 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The authors have nothing to disclose.

The technique presented in this paper is a novel one using the temperature dependence of NIR absorption of water and presents no significant difficulty in setting up the necessary equipment and implementation. The incident light can be easily produced by using a halogen lamp and an NBPF. However, lasers cannot be used, because coherent interference patterns would appear on the images. Common optical lenses and glass cells for visible-light use can be used, as they transmit an adequate amount of light at &#955; =...

An erratum was issued for: <a href="https://www.jove.com/video/57407/near-infrared-temperature-measurement-technique-for-water-surrounding">Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere</a>. The Protocol section was updated.
In 2.2.7, the temperature coefficient of water, &#945;f, for &#955; = 1150 nm has been corrected from:
4.0 x 10-3 K-1 mm-1
to:
2.8&#160;x 10-4&#160;K-1&#160;mm-1

An erratum was issued for: <a href="https://www.jove.com/video/57407/near-infrared-temperature-measurement-technique-for-water-surrounding">Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere</a>. The Protocol section was updated.

Erratum: Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique to measure temperature near a small heat source within a medium is required in many scientific research fields and applications. For example, in the research on magnetic hyperthermia, which is a cancer therapy method using electromagnetic induction of magnetic particles, or small magnetic pieces, it is critical to accurately predict the temperature distributions generated by the magnetic particles1,2. However, although microwave3,4, ultrasound5,6,7,8, optoacoustic9, Raman10, and magnetic resonance11,12-based temperature measurement techniques have been researched and developed, such an inner temperature distribution cannot be accurately measured at present. Thus far, single-position temperatures or temperatures at a few positions have been measured via temperature sensors, which, in the case of induction heating, are non-magnetic optical fiber temperature sensors13,14. Alternatively, the surface temperatures of media have been remotely measured via infrared radiation thermometers to estimate the inner temperatures14. However, when a medium containing a small heat source is a water layer or a non-turbid aqueous medium, we have demonstrated that a near-infrared (NIR) absorption technique is useful to measure the temperatures15,16,17,18,19. This paper presents the detailed protocol of this technique and representative results.
The NIR absorption technique is based on the principle of temperature dependence of the absorption bands of water in the NIR region. As is shown in Figure 1a, the &#957;1 + &#957;2 + &#957;3 absorption band of water is observed in the 1100-nm to 1250-nm wavelength (&#955;) range and shifts to shorter wavelengths as the temperature increases19. Here, &#957;1 + &#957;2 + &#957;3 means that this band corresponds to the combination of the three fundamental O-H vibration modes: symmetric stretching (&#957;1), bending (&#957;2), and antisymmetric stretching (&#957;3)20,21. This change in the spectrum indicates that the most temperature-sensitive wavelength in the band is &#955; &#8776; 1150 nm. Other absorption bands of water also exhibit similar behavior with respect to the temperature15,16,17,18,20,21. The &#957;1 + &#957;3 band of water observed within the range &#955; = 1350&#8722;1500 nm and its temperature dependence are shown in Figure 1b. In the &#957;1 + &#957;3 band of water, 1412 nm is the most temperature-sensitive wavelength. Thus, it is possible to obtain two-dimensional (2D) temperature images by using an NIR camera to capture 2D absorbance images at &#955; = 1150 or 1412 nm. As the absorption coefficient of water at &#955; = 1150 nm is smaller than that at &#955; = 1412 nm, the former wavelength is suitable for approximately 10-mm-thick aqueous media, while the latter is suitable for approximately 1-mm-thick ones. Recently, using &#955; = 1150 nm, we obtained the temperature distributions in a 10-mm-thick water layer containing an induction-heated 1-mm-diameter steel sphere19. Moreover, the temperature distributions in a 0.5-mm-thick water layer have been measured by using &#955; = 1412 nm15,17.
An advantage to the NIR-based temperature imaging technique is that it is simple to setup and implement because it is a transmission-absorption measurement technique and needs no fluorophore, phosphor, or other thermal probe. In addition, its temperature resolution is less than 0.2 K15,17,19. Such a good temperature resolution cannot be achieved by other transmission techniques based on interferometry, which have often been used in heat and mass transfer studies22,23,24. We note, however, that the NIR-based temperature imaging technique is not suitable in cases with considerable local temperature change, because the deflection of light caused by the large temperature gradient becomes dominant19. This matter is referred in this paper in terms of practical use.
This paper describes the experimental setup and procedure for the NIR-based temperature imaging technique for a small magnetic sphere heated via induction; additionally, it presents the results of two representative 2D absorbance images. One image is of a 2.0-mm-diameter steel sphere in a 10.0-mm-thick water layer that is captured at &#955; = 1150 nm. The second image is of a 0.5-mm-diameter steel sphere in a 2.0-mm-thick maltose syrup layer that is captured at &#955; = 1412&#160;nm. This paper also presents the calculation method and results of the three-dimensional (3D) radial distribution of temperature by applying the inverse Abel transform (IAT) to the 2D absorbance images. The IAT is valid when a 3D temperature distribution is assumed to be spherically symmetric as in the case of a heated sphere (Figure 2)19. For the IAT calculation, a multi-Gaussian function fitting method is employed here, because the IATs of Gaussian functions can be obtained analytically25,26,27,28,29 and fit well to monotonically decreasing data; this includes experiments employing thermal conduction from a single heat source.

<table border="0" cellpadding="0" cellspacing="0" style="width:727px;" width="727">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Induction heating system</td>
			<td style="width:208px;">CEIA, Italy</td>
			<td style="width:119px;">SPW900/56</td>
			<td style="width:167px;">780 kHz, 5.6 kW (max).</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Coil</td>
			<td style="width:208px;">SA-Japan</td>
			<td style="width:119px;">custom</td>
			<td>Water-cooled copper tube; two-turn; outer dia. 28 mm.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Water chiller</td>
			<td style="width:208px;">Matsumoto Kikai, Japan</td>
			<td style="width:119px;">MP-401CT</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:233px;">Halogen lamp</td>
			<td style="width:208px;">Hayashi Watch-Works, Japan</td>
			<td style="width:119px;">LA-150UE-A</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:233px;">Narrow bandpass filter for &#955; = 1150 nm</td>
			<td style="width:208px;">Andover</td>
			<td style="width:119px;">115FS10-25</td>
			<td>Full width at half-maximum (FWHM): 10 nm.</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:233px;">Narrow bandpass filter for &#955; = 1412 nm</td>
			<td style="width:208px;">Andover</td>
			<td style="width:119px;">semi-custom</td>
			<td>Full width at half-maximum (FWHM): 10 nm.</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:233px;">Bandpass filter for &#955; = 850&#8722;1300 nm</td>
			<td style="width:208px;">Spectrogon</td>
			<td style="width:119px;">SP-1300</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:233px;">Bandpass filter for &#955; = 1100&#8722;2000 nm</td>
			<td style="width:208px;">Spectrogon</td>
			<td style="width:119px;">SP-2000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">NIR camera</td>
			<td style="width:208px;">FLIR Systems</td>
			<td style="width:119px;">Alpha NIR</td>
			<td>InGaAs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Image acquisition software</td>
			<td style="width:208px;">FLIR Systems</td>
			<td style="width:119px;">IRvista</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Image processing software</td>
			<td style="width:208px;">NIH</td>
			<td style="width:119px;">ImageJ</td>
			<td>ver. 1.51r</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Image processing software</td>
			<td style="width:208px;">MathWorks</td>
			<td style="width:119px;">Matlab</td>
			<td>ver. 2016a</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Telecentric lens</td>
			<td style="width:208px;">Edmond Optics</td>
			<td style="width:119px;">55350-L</td>
			<td>X1</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Steel sphere (0.5 mm dia.)</td>
			<td style="width:208px;">Kobe Steel, Japan</td>
			<td style="width:119px;"></td>
			<td>Fe-1.5Cr-1.0C-0.4Mn (wt %)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Steel sphere (2.0 mm dia.)</td>
			<td style="width:208px;">Kobe Steel, Japan</td>
			<td style="width:119px;"></td>
			<td>Fe-1.5Cr-1.0C-0.4Mn (wt %)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:233px;">Maltose syrup as aqueous gel</td>
			<td style="width:208px;">Sonton, Japan</td>
			<td style="width:119px;">Mizuame</td>
			<td>Food product</td>
		</tr>
	</tbody>
</table>

near-infrared temperature measurement technique for water surrounding an induction-heated small magnetic sphere

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter magnetic sphere is irradiated with 1150 nm or 1412 nm incident light, as selected using a narrow bandpass filter; additionally, two-dimensional absorbance images, which are the transverse projections of the absorption coefficient, are acquired via a near-infrared camera. When the three-dimensional distributions of temperature can be assumed to be spherically symmetric, they are estimated by applying inverse Abel transforms to the absorbance profiles. The temperatures were observed to consistently change according to time and the induction heating power.

Images of &#916;Ai(x, z) at &#955; = 1150 nm for a 2.0-mm-diameter steel sphere in water and at &#955; = 1412 nm for a 0.5-mm-diameter steel sphere in maltose syrup are presented in Figure 5a and Figure 6a, respectively. In both cases, the sphere was located 12 mm below the bottom of the coil along its central axis. Figu...

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Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This ...

The overall goal of this experiment is to measure temperature distributions near a heated small sphere or a point heat source located inside water or non-turbid acquiesce media. This method will be very helpful for researching local heating inside media, such as hyperthermia research using magnetic particles. The main advantage of this technique is that it's easy to set up and implement.Demonstrating the procedure will be Keisuke Nishijima and Van Cuong Han, who are grad students from my laboratory. to prepare a water or aqueous liquid sample, first use the minimum necessary amount of quick-drying, water resistant glue to fix a two millimeter diameter steel sphere to the end of a thin, non-metallic string or rod. Ensure that the glue minimally affects the shape of the sphere and the heat transfer rate, then thread the string through the center hole of a PTFE cuvette cap.Tape the string in place with 22 millimeters of the string hanging below the cap. Equip a water filled syringe with a 0.22 micrometer syringe filter and a plastic dispensing needle. Carefully fill a glass cell with an optical path length of 10 millimeters, and a height of 45 millimeters with filtered water, being careful to avoid the formation of air bubbles.Air bubbles and suspended particulates should be removed as much as possible in advance to obtain correct measures and successfully estimate temperatures. Place the cap on the cell so that the sphere hangs in the center of the rectangular cell. To prepare an aqueous gel sample, first heat the aqueous gel until its viscosity is sufficiently reduced to be poured smoothly.Use a syringe to half-fill a rectangular glass cell with an optical path length of two millimeters with the heated gel. Allow the gel to cool. Then place a 0.5 millimeter diameter steel sphere at the center of the gel surface.Fill the rest of the cell with heated aqueous gel in the same way and allow it to cool. Once the aqueous liquid or gel sample has been prepared, place the cell in a plastic holder on the optical rail of the Near-IR imaging system. To begin preparing the Near-IR imaging system, equip a halogen lamp with a fiber light guide.Place a narrow bandpass filter with the transmittance peak at either 1, 150 nanometers or 1, 412 nanometers between the fiber light guide in the cell. at 1, 150 nanometers and 1, 412 nanometers, the water absorbance increases as the water temperature increases. Place a bandpass filter with the wider transmission range around the chosen wavelength between the halogen lamp fiber light guide and the narrow bandpass filter.Mount an iris diaphragm between the narrow bandpass filter and the cell holder. Then set up a Near-IR camera in line with the sample cell. Fix an object-space telecentric lens between the cell and the camera.Turn on the Near-IR camera, ensure that the camera is connected to a computer, and open the image acquisition software. Turn on the halogen lamp, check the image displayed on the monitor, and adjust the lamp output power as needed. Adjust the axis, position, and focus of the telecentric lens to obtain a finely-detailed image of the steel sphere.The optical asset adjustment is important for achieving the telecentric optical system as to be carefully made to look at the reflected images. Then prepare an induction heating system consisting of a high frequency generator, a water-cooled coil, and a water chiller. Mount the coil on an XYZ moveable stage.Position the coil over the sample cell, so that the distance between the center of the coil and the steel sphere is approximately 15 millimeters. Ensure that no other metal components are near the coil. Turn on the water chiller for the induction heater and start the water circulation.Ensure that the frame rate and the camera integration time are set to the maximum available values. Once the induction heater is ready, set the maximum number of frames to record, name the image data file, and start recording images in the image acquisition software. Run the induction heater for the desired length of time.Either allow the image acquisition to run for the set duration, or manually stop recording after the desired length of time. Save the images in a non-compressed format, such as a TIFF sequence. Open the sequence in image processing software, and convert the saved images of transmitted light intensity to the absorbance difference images.Colorize the images with the desired color range. The temperature can then be estimated from these images using additional command scripts. The increase in water temperature around an induction-heated two millimeter diameter steel sphere was observed as a circularly symmetric change in absorbance with respect to the Near-IR image prior to heating.Free convection was observed after 1.2 seconds of heating, suggesting a transition from a pure thermal conduction regime to a free convection regime. Similar effects were observed around an induction-heated 0.5 millimeter diameter steel sphere in maltose syrup at three different induction heating powers. The radius and magnitude of the change in absorbance increased with increasing power.Free convection was not observed after 1.2 seconds. In the water sample, the magnitude of the change in absorbance over time was greatest close to the sphere. A combination of two or three Gaussian functions can achieve a good fit for the relationship between absorbance and the radius of the image plane.Similar results are observed in the gel sample. The fitted functions can then be transformed into the change in temperature in the water and the gel, assuming that thermal conduction occurs in the radial direction, and the temperature profiles are spherically symmetric. The key devices for the temperature measurement are a near-infrared camera, a narrow bandpass filter.Once they are prepared, the procedure from setup to image acquisition is easily done by any researcher. This imaging technique will be applied not only to induction heating, but also to various heating method. Temperature and heat generation inside media which have never been directly measured so far can be revealed.

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8.0K visualizações.  Tokyo Metropolitan University. The overall goal of this experiment is to measure temperature distributions near a heated small sphere or a point heat source located inside water or non-turbid acquiesce media. This method will be very helpful for researching local heating inside media, such as hyperthermia research using magnetic particles. The main advantage of this technique is that it's easy to set up and implement.Demonstrating the procedure will be Keisuke Nishijima and Van Cuong Han, who are grad students from ...