Magnetic nanometer temperature measuring method based on effective relaxation time

Abstract

The invention discloses a magnetic nanometer temperature measuring method based on effective relaxation time. The method comprises the following steps that magnetic nanometer particles are placed in an object area to be detected inside a nontransparent article; the magnetic nanometer particles in the object area to be detected are subjected to tissue heating with a radio frequency magnetic field, and meanwhile magnetizing response information of the magnetic nanometer particles under the excitation of the radio frequency magnetic field is obtained with a coil of a hollow structure; the amplitude value of any harmonic signal in magnetizing response signals of the magnetic nanometer particles is extracted; effective relaxation time serves as an intermediate variable, and the relation between the amplitude values of harmonic signals and the absolute temperature is established with the harmonic information to solve the absolute temperature. According to the method, a mathematical model between the magnetizing response harmonic amplitude value information of the magnetic nanometer particles and temperatures is established with the effective relaxation time, the temperature information of the article can be rapidly and accurately obtained, and especially the temperatures are measured while a radio frequency field is heated under the premise that no excitation magnetic field is added in magnetic nanometer thermal therapy.

Description

Technical field [0001] The invention relates to the technical field of non-invasive temperature measurement, based on nanometer measurement technology, and specifically relates to a magnetic nanometer temperature measurement method based on effective relaxation time, which solves the problem that the magnetic nanometer temperature measurement method is not suitable for high-frequency excitation magnetic field for a long time. Using the temperature sensitivity of magnetic nanoparticles, the magnetic nanometer temperature measurement is carried out through the magnetization response of the magnetic nanometer in the radio frequency excitation magnetic field, and the temperature measurement is carried out while the radio frequency magnetic field heats the tissue in the field of magnetic nano thermotherapy. Background technique [0002] According to the "2015 China Cancer Registry Annual Report" issued by the National Cancer Registry, my country had 3.372 million new cancer cases that ...

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Problems solved by technology

The current internal temperature measurement methods used clinically in vivo, whether they are thermocouples, high-resistance wires, thermistors, or light, are all invasive and destructive temperature measurement methods that place heat-sensitive elements inside the measured tissue, and have the following limitations. : (1) The number of temperature probes to be tested and the structure of human tissue are limited, and the number of temperature monitoring points for invasive destructive temperature measurement is limited. The temperature data obtained are only a limited number of points inside the tissue, which cannot reflect the temperature distribution of the entire heated tissue

(2) The temperature measuring probe itself will affect the heat transfer characteristics of the heated tissue, which greatly interferes with the distribution of the thermal field, further affecting the uniformity of the temperature

(3) Bring pain to tumor patients, may cause cancer cell proliferation and metastasis, and increase the risk of treatment

In 2009, J.B.Weaver of the United States verified the temperature sensitivity of magnetic nanoparticles from the experimental point of view for the first time. When the magnetic nanoparticles are excited by a single-frequency alternating magnetic field, the amplitude of the third harmonic and the fifth harmonic in the AC magnetization information of the magnetic nanoparticles The ratio of the sub-harmonic amplitude is correlated with the temperature. It has been verified by experiments and fitting methods. Its initial temperature measurement accuracy in the thermotherapy temperature window is less than 1 degree Celsius, but unfortunately it lacks relevant theoretical basis.

However, its disadvantage is that the measurement time is long and the time resolution is low, which cannot meet the requirements of special applications.

In 2012, Dr. Zhong Jing and others used the temperature sensitivity of magnetic nanoparticles to propose a magnetic nanometer temperature measurement method under the excitation of a single-frequency alternating magnetic field. However, this method needs to measure the high-order harmonic amplitude information of the magnetization response of magnetic nanoparticles, but the measurement of high-order harmonic amplitude is difficult, because the temperature measurement accuracy of this method is low

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