RU2103920C1 - Computer tomograph - Google Patents

Abstract

FIELD: medical engineering. SUBSTANCE: device has coaxially mounted casing and measurement chamber with carcass mounted between them rotatable about longitudinal axis, the carcass having K emitting sources possessing fan-shaped pattern and L receivers which outputs are connected to corresponding inputs of multi-channel recording unit connected to computer. The first control output of the computer is connected to executive device kinematically coupled with the carcass. Extremely high frequency energy excitation source with horizontal polarization of electromagnetic wave at a frequency of F1 is additionally introduced. Each of its m outputs is connected to m inputs of controlled dividers and phase rotation units united in one group which m outputs are connected to each of inputs of K emitting sources possessing fan-shaped pattern. K-m inputs of emitting sources are connected to each of n outputs of extremely high frequency energy excitation source with vertical polarization of electromagnetic wave at a frequency of F2 which base outlets are connected to corresponding base inputs of multi-channel recording unit, respectively. The second control output of computer is connected to extremely high frequency energy excitation source with frequency F1 and the third one is connected to the second executive unit kinematically coupled with frame surrounding measurement chamber along its perimeter and provided with longitudinally movably mounted receivers. Toroidal reservoir made from flexible dielectric material is positioned inside of measurement chamber made from dielectric material and filled with matching liquid to enable object under examination to be placed in it. EFFECT: high sensitivity to internal temperature gradients of visceral organs. 1 dwg

Description

 The invention relates to non-destructive testing and can be used for tomographic examination of objects and medical diagnostics for various human diseases, as well as for the treatment of a number of diseases and control of internal temperature gradients in the process of hyperthermia.

 A device is known that implements a method of microwave tomographic examination of an object [2]. The device contains a resonator 1, exciting elements 2, a transmitting device 6, receiving devices 5, a signal extraction device 7, a recording device 8. An object under investigation is placed in the resonator 1, and the spectrum of electromagnetic oscillations of the resonator without an object is pre-recorded, then with the object.

The disadvantage of this device is that it cannot be used to study the internal organs of a person due to the large attenuation of the signal in the human body. In the microwave range, this is explained by the fact that θ _o / θ _m <1, where θ _o is the intrinsic Q factor of the resonator with the object; θ _m is the loaded Q-factor of the resonator.

 In addition, the device fundamentally cannot provide information for solving the three-dimensional reconstruction problem and does not have the ability to locally heat the object under study and control the temperature gradient of the internal organs of a person.

 The closest in technical essence is an X-ray computer tomograph [1], containing a coaxially mounted housing, a measuring chamber, between which a frame with radiation sources with a fan radiation pattern, L-radiation receivers rigidly placed along the perimeter between the measuring chamber and the housing, while the terminals of the receivers are connected to the testing device through a multi-channel recording device and displayed information, and one of the outputs of the computer through the actuator is connected to the frame.

 X-ray receivers detect received signals. The measurement results obtained from the detectors are mathematically processed to obtain the spatial distribution of the attenuation, which is visualized, for example, on a computer or video matrix.

 The disadvantage of this device is that it provides a visualization of the internal structure of biological objects by measuring tissue density. Thus, the presence of a sharp change in the density along the path of the beam (for example, the presence of bones) leads to irreparable artifacts (distortions). This is due to the fact that the processing of measurement results does not take into account the effect of three-dimensional scattering of the propagating beam.

 In some cases, the total beam attenuation due to the scattering effect is so great that there is practically no signal behind such an obstacle.

 In addition, the measurement result does not depend on changes in the temperature of internal organs, which is often necessary to know for medical diagnosis of internal organs.

So for an X-ray tomograph, the measurement result is related to temperature by the ratio
ρ (t ^° ) = ρ _o (1 - βt ^° ),
where β is the coefficient of volumetric thermal expansion (β _max = 0.001 1 / deg);
t ^o - temperature, ^o C;
ρ is the tissue density.

With the required temperature sensitivity of 1 ^o C, it is necessary to record a change in ρ of less than 0.1%, which is practically unattainable.

 An X-ray tomograph provides visualization of the internal structure of a person based on the measurement of attenuation in each radiation direction.

Moreover, the larger the total number of rays crossing the body under study in different directions, the higher the spatial resolution when rendering the image. The total number of rays in the considered tomograph is
M = L • N • m,
where N is the number of exposures (the number of positions of transmitting emitters);
L is the number of receiving detectors in each exposure;
m is the number of simultaneously operating emitters.

где S - площадь квадрата, в который вписано исследуемое тело;
M - общее число лучей.The potential resolution of the tomograph is

where S is the area of the square into which the investigated body is inscribed;
M is the total number of rays.

 An X-ray tomograph provides visualization of a slice of an object under study, the thickness of which is several millimeters and is equal to the thickness of the beam.

The disadvantages of an x-ray tomograph are:
- practical insensitivity to internal temperature gradients;
- the impossibility of accounting for scattered fields, which does not allow the diagnosis of tissues adjacent to the human skeleton;
- the inability to use for treatment.

The technical effect that can be achieved using the proposed computed tomography device is that it:
- provides visualization of three-dimensional objects;
- sensitive to temperature gradients of internal organs;
- provides diagnostics of tissues adjacent to the skeleton;
- can be used for treatment in the process of hyperthermia.

 The drawing shows the general diagram of a computer tomograph, where: 1 - housing, 2 - measuring chamber, 3 - housing, 4 - radiation sources with a fan radiation pattern, 5 - receiving devices, 6 - matching fluid, 7 - measured object, 8 - reservoir , 9 - a source of excitation of microwave energy at a frequency of F1 with horizontal wave polarization, 10 - a source of excitation of microwave energy at a frequency of F2 with vertical polarization of a wave, 11 - a multi-channel recording device, 12 - a computer, 13 - a control unit for dividers and phase shifters, 14 - first use itelnoe device, 15 - second actuating device 16 - the frame.

 A computed tomograph contains a coaxially mounted housing 1, a measuring chamber 2 mounted on the housing 1, a frame 3 mounted inside the housing 1 with the possibility of rotation around a vertical axis, K radiation sources with a fan radiation pattern 4, rigidly mounted on the frame 16, L receiving devices 5, installed around the perimeter of the measuring chamber 2, the source of excitation of microwave energy at a frequency F1 with horizontal polarization of wave 9, the source of excitation of microwave energy at a frequency F2 with vertical polarization of wave 10, is many a channel recording device 11, the output of which is connected to the input of a computer 12, a unit of controlled dividers and phase shifters 13, each of the m-inputs of which is respectively connected to each of the m-outputs of a microwave energy excitation source at a frequency F1 with a horizontal polarization of wave 9, and each from the m-outputs of the block of controlled dividers and phase shifters 13 connected to the corresponding input of each of K radiation sources with a fan radiation pattern 4, while km of inputs of radiation sources with a fan radiation pattern p Connected respectively to each of the n-outputs of the microwave energy excitation source at a frequency F2 with vertical polarization of wave 10, the reference outputs of which are connected to the corresponding reference inputs of the multi-channel recording device 11, the inputs of which are connected to each output of the receiving device 5, while the control output of the computer 12, is connected to the control input of the unit of controlled dividers and phase shifters 13 and to the control input of the microwave energy excitation source at frequency F1 with horizontal wave polarization, W The second control output of the computer 12 through the first actuator 14 is kinematically connected to the frame 16, and the third control output of the computer 12 through the second actuator is kinematically connected to the frame 3, while inside the measuring chamber 2, made of dielectric material, a tank 8 is made of elastic dielectric material in the form of a torus filled with matching fluid 6, while the measured object 7 is located inside the reservoir 8.

 Computed tomography works as follows.

. В резервуар 8 поступает согласующая жидкость 6, которая создает избыточное давление, достаточное для плотного прилегания эластичных стенок резервуара к диэлектрическому объекту. При этом диэлектрическая проницаемость согласующей жидкости

должна быть заранее известна. Идеальным случаем является

,
где

- усредненная проницаемость тела человека.Calibration is initially performed. For this, a homogeneous cylindrical dielectric object (f ≃ 350 mm) with a known dielectric constant is coaxially placed inside the measuring chamber 2

. The matching fluid 6 enters the reservoir 8, which creates an excess pressure sufficient for the elastic walls of the reservoir to fit snugly against the dielectric object. In this case, the dielectric constant of the matching fluid

must be known in advance. The ideal case is

,
Where

- the average permeability of the human body.

и величиной

. Приемные устройства 5, число которых L, воспринимают вертикальную составляющую электромагнитного поля всех зондирующих сигналов, которые после преобразования на промежуточную частоту поступают в многоканальное регистрирующее устройство 11. В многоканальном регистрирующем устройстве 11 осуществляется их детектирование путем свертки со своим опорным сигналом (со своей копией), поступающим от соответствующего канала источника 10 возбуждения СВЧ-энергии на частоте F2 с вертикальной поляризацией волны 10. В результате детектирования регистрируются постоянные напряжения Re E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ и Im E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ для данного направления распространения зондирующих сигналов, значения которых фиксируются в компьютере 12. Время регистрации (измерения) составляет Δτ, после которого компьютер 12 выдает команду на перемещение рамы 16 через первое исполнительное устройство 14, на которой установлены приемные устройства 5, в вертикальном направлении на заданную величину. В новом положении приемных устройств 5 регистрируются новые значения Re E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ и Im E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ , которые фиксируются в памяти компьютера 12. Этот процесс повторяется для каждого нового положения приемных устройств 5 в вертикальном направлении. Обычно число положений составляет ≈15 с дискретом ≈10 мм. Далее компьютер 12 выдает команду через второе дополнительное устройство 15 на разворот каркаса 3 на заданный угол Δθ_m. Процесс повторяется до тех пор, пока угол разворота каркаса 3 относительно исходного не составит 270^o. В результате в компьютере 12 накоплена информация, достаточная для калибровки компьютерного томографа и нормирования зондирующих сигналов при последующих измерениях пациента.From the excitation source of microwave energy with vertical polarization of wave 10, operating at a frequency of F2, in which n identical channels are formed, probing signals are transmitted to radiation sources with a fan radiation pattern 4. The probe signals of each of the n-channels have an independent modulation law . Each sounding signal is fed to one of the inputs of the radiation source with a fan radiation pattern 4. The radiation sources with a fan radiation pattern 4 are mounted on the frame 3 and are adjacent with openings to the outer wall of the measuring chamber 2. In this case, the sounding signals propagate in the direction of the receiving devices 5, which mounted on a frame 16 mounted on the frame 3 with the possibility of vertical movement. All sounding signals have a vertical polarization of the electromagnetic field. During propagation, each probe signal acquires an additional phase shift and decays in amplitude in accordance with the value

and size

. Receiving devices 5, the number of which is L, perceive the vertical component of the electromagnetic field of all the probing signals, which, after conversion to an intermediate frequency, enter the multi-channel recording device 11. In the multi-channel recording device 11, they are detected by convolution with their reference signal (with its copy), coming from the corresponding channel of the microwave energy excitation source 10 at a frequency F2 with vertical polarization of wave 10. As a result of detection, the register ruyutsya constant voltage Re E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ and im e $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ for this direction of propagation of sounding signals, the values of which are recorded in the computer 12. The registration (measurement) time is Δτ, after which the computer 12 issues a command to move the frame 16 through the first actuator 14, on which the receiving devices 5 are installed, in the vertical direction for a given value. In the new position of the receiving devices 5, new values of Re E are recorded. $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ and im e $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ , which are recorded in the computer 12. This process is repeated for each new position of the receiving devices 5 in the vertical direction. Typically, the number of positions is ≈15 with a discrete of ≈10 mm. Next, the computer 12 issues a command through the second additional device 15 to turn the frame 3 by a given angle Δθ _m . The process is repeated until the angle of rotation of the frame 3 relative to the original is 270 ^o . As a result, sufficient information is stored in computer 12 to calibrate the computed tomograph and to normalize the probing signals during subsequent measurements of the patient.

(X, Y, Z) и

(X, Y, Z) и выдает на экран дисплея компьютера 12 (либо другого обычного компьютера) в виде картографической проекции. При проведении исследований в нескольких сечениях возможно получение изображения в виде объемной структуры. Выявленные патологические особенности органов (например, злокачественные опухоли на ранней стадии), связанные с аномальным отклонением

в области (Xi, Yi, Zi) фиксируются компьютером 12, который дает команду через второе исполнительное устройство 15 на разворот каркаса 3 таким образом, чтобы расстояние от центра области (Xi, Yi, Zi) до источника излучения с веерной диаграммой направленности 4, работающего на частоте F1, было минимальным. От компьютера 12 поступают сигналы на блок управляемых фазовращателей и делителей 13 для оптимального распределения амплитуд (Ai) и фаз (Фi) каждого m-ого источника возбуждения СВЧ-энергии на частоте F1 с горизонтальной поляризацией волны 9. Блок управления фазовращателей и делителей 13 по своей сущности аналогичен обычно используемым при построении фазированных антенных решеток. Значения Ai и Фi вычисляются, так как известно распределение

(X, Y, Z) и

(X, Y, Z). В результате источники излучения с веерной диаграммой направленности 4, число которых m, образует фазированную антенную решетку с точкой фокусировки в центре заданной области (Xi, Yi, Zi). Включаются источники возбуждения СВЧ-энергии на частоте F1 с горизонтальной поляризацией волны. При этом устанавливается выходная мощность намного ниже номинальной (номинальная мощность 100. ..200 Вт). При работающем источнике возбуждения СВЧ-энергии на частоте F1 с горизонтальной поляризацией волны 9 проводятся исследования пациента как описано выше с той лишь разницей, что перемещение совокупности приемных устройств 5 по вертикали не производится. Так же отключается и синхронизация от кардиоцикла. В результате число измерений уменьшается и увеличивается скорость измерения и вычисления

(X, Y, Z) и

(X, Y, Z). При этом для каждого нового углового положения каркаса 3 компьютер вычисляет свои новые значения фаз Фi и амплитуд Ai и соответствующие сигналы поступают на блок управляемых фазовращателей и делителей 13. Поскольку

сильно зависит от температуры (≈2% на 1^oC), что наблюдается резкое изменение

в области фокусировки. Если область фокусировки (максимальное изменение

) с достаточной степенью совпадает с заданной областью (Xi, Yi, Zi), то следующий цикл проводится при номинальной выходной мощности источника возбуждения СВЧ-энергии на частоте F1 9 и включенной синхронизацией от кардиоцикла. При этом сигналы, излучаемые k-n источниками излучения 9, имеют горизонтальную поляризацию и частоту F1 < F2. Это обеспечивает достижение необходимой развязки между сигналами источника возбуждения СВЧ-энергии на частоте F1 9 и зондирующими сигналами k-m=n, поступающими на L входов приемных устройств 5. При проведении измерений при номинальной выходной мощности источника возбуждения СВЧ-энергии на частоте F1 9 на дисплее компьютера 12 постоянно наблюдается распределение

(X, Y, Z), нормированное в величинах превышения температуры относительно исходной температуры в области (Xi, Yi, Zi). Когда значение превышения температуры превосходит заданное, то источник возбуждения СВЧ-энергии на частоте F1 9 автоматически отключается по команде, поступающей от компьютера.Before examining the patient, part of the matching fluid 6 is removed from the reservoir 8 to relieve excess pressure. The calibration object is deleted and the patient is placed in its place. An excess pressure is again created in the reservoir 8, sufficient for the walls of the reservoir 8 to fit snugly against the patient's body. The plane of the studied section of the patient’s body should coincide with the plane of symmetry of the radiation source radiation pattern with a fan radiation pattern 4. Further, the research process is completely similar to the calibration process. As a result, Re E measurements are accumulated in computer 12 $\genfrac{}{}{0ex}{}{\text{d}}{\text{nm}}$ and in e $\genfrac{}{}{0ex}{}{\text{d}}{\text{nm}}$ which are normalized with respect to Re E $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ and in e $\genfrac{}{}{0ex}{}{\text{°}}{\text{nm}}$ for the corresponding angular positions of radiation sources with a fan pattern 4 and receiving devices 5. If it is necessary to measure the parameters of the patient’s organs in the dynamics, commands to move the frame 16 with the receiving devices 5 installed and the frame 3 are not immediately received from the computer after the measurement time Δτ, and after a longer period of time determined by the heartbeat period RR ₁ > Δτ. To do this, standard cardiogram removal equipment is coupled to computer 12 and measurements are synchronized from the R tooth of the patient's cardiogram. After the patient research process is completed, computer 12 calculates the distribution according to a given algorithm

(X, Y, Z) and

(X, Y, Z) and displays on the display screen of the computer 12 (or other ordinary computer) in the form of a map projection. When conducting studies in several sections, it is possible to obtain an image in the form of a volumetric structure. Identified pathological features of organs (for example, malignant tumors at an early stage) associated with abnormal deviation

in the region (Xi, Yi, Zi) are fixed by a computer 12, which gives a command through the second actuator 15 to turn the frame 3 so that the distance from the center of the region (Xi, Yi, Zi) to the radiation source with a fan radiation pattern 4, working at a frequency of F1, was minimal. From computer 12, signals are sent to a block of controlled phase shifters and dividers 13 for an optimal distribution of amplitudes (Ai) and phases (Фi) of each m-th microwave energy source at frequency F1 with horizontal polarization of wave 9. The control unit for phase shifters and dividers 13 entities similar to those commonly used in the construction of phased array antennas. The values of Ai and Фi are calculated, since the distribution is known

(X, Y, Z) and

(X, Y, Z). As a result, radiation sources with a fan radiation pattern 4, the number of which is m, forms a phased antenna array with a focal point in the center of a given region (Xi, Yi, Zi). Microwave energy sources are turned on at a frequency of F1 with horizontal wave polarization. At the same time, the output power is set much lower than the rated power (rated power 100 ... 200 W). With a working source of excitation of microwave energy at a frequency F1 with a horizontal polarization of wave 9, the patient is examined as described above with the only difference being that the collection of receiving devices 5 is not moved vertically. Also, the synchronization from the cardiocycle is turned off. As a result, the number of measurements decreases and the speed of measurement and calculation increases.

(X, Y, Z) and

(X, Y, Z). Moreover, for each new angular position of the frame 3, the computer calculates its new values of the phases Фi and amplitudes Ai and the corresponding signals are fed to the block of controlled phase shifters and dividers 13. Since

strongly dependent on temperature (≈2% per 1 ^o C), which is observed a sharp change

in focus area. If the focus area (maximum change

) with a sufficient degree coincides with the specified area (Xi, Yi, Zi), then the next cycle is carried out at the rated output power of the microwave energy excitation source at a frequency of F1 9 and the synchronization from the cardiac cycle is turned on. In this case, the signals emitted by kn from radiation sources 9 have horizontal polarization and a frequency of F1 <F2. This ensures the necessary isolation between the signals of the microwave energy excitation source at a frequency of F1 9 and the probing signals km = n supplied to the L inputs of the receiving devices 5. When measuring at a rated output power of the microwave energy excitation source at a frequency of F1 9 on a computer display 12 distribution is constantly observed

(X, Y, Z) normalized in the values of the temperature rise relative to the initial temperature in the region (Xi, Yi, Zi). When the temperature rise value exceeds a predetermined value, the microwave energy excitation source at a frequency of F1 9 is automatically turned off by a command from the computer.

Claims (1)

A computer tomograph containing a coaxially mounted housing and a measuring chamber, between which a frame is mounted with rotation around the longitudinal axis K with radiation sources placed on it with a fan radiation pattern and L receiving devices, the outputs of which are connected to the corresponding inputs of a multi-channel recording device connected to a computer , while the first control output of the computer is connected to an actuator kinematically connected to the frame, characterized in that an additional microwave energy excitation source with horizontal polarization of the electromagnetic wave at a frequency of F _{1 has} been introduced, each of m outputs of which is connected to m inputs of a unit of controlled dividers and phase shifters, m outputs of which are connected to each of the inputs of K radiation sources with a fan radiation pattern, K m of the radiation source inputs are connected respectively to each of n outputs excitation source of microwave energy with vertical polarization of the electromagnetic wave at the frequency F _2, the reference outputs cat They are connected to the corresponding reference inputs of a multi-channel recording device, the second control output of the computer is connected respectively to a microwave energy source with horizontal polarization of the electromagnetic wave at frequency F1 and a block of controlled dividers and phase shifters, and the third is connected to a second actuator kinematically connected to a frame placed along the perimeter of the measuring chamber and equipped with receiving devices mounted on it with the possibility of longitudinal movement you, the inside of the measuring chamber made of a dielectric material is arranged in a torus vessel of a resilient dielectric material and filled with the matching liquid to be placed in it the object of investigation.