CN103901265B - Measuring method for microwave ablation antenna pointed end power - Google Patents

Abstract

The invention relates to a measuring method for microwave ablation antenna pointed end power. Based on a physical platform formed by a microwave generator, a temperature measurement needle, an operating platform, a data acquisition instrument and a computer, the method includes the steps of setting a temperature measurement point distribution area, opening the microwave generator, obtaining temperature values of all temperature measurement points within n seconds before heating, solving the derivative of the temperature on each temperature measurement point to time, determining a cylindrical half shaft section, calculating the power value Qr of each temperature measurement point on the unit volume (cm3) in the cylindrical half shaft section, and integrating the power values of the temperature measurement points on the unit volumes in a microwave generator effective temperature field to obtain the microwave ablation antenna pointed end power, wherein the microwave generator effective temperature field refers to a cylinder formed in the mode that the cylindrical half shaft section winds an ablation antenna, any Qr passing a half section of a center shaft is the same as the Qr of a corresponding point on the cylindrical half shaft section in the microwave generator effective temperature field, and the microwave ablation antenna pointed end power is full net power eliminating loss power in output power.

Description

The measuring method of microwave ablation antenna pointed end power

Technical field

The present invention relates to the measuring method field of medical supplies, particularly to the measurement side of microwave ablation antenna pointed end power Method.

Background technology

In current biomedical treatment, heating ablation art has become as indispensable effectively treatment handss in clinical practice Section, especially for the treatment of liver neoplasm, more has significant curative effect.

Ablation minimally invasive, quick, effective the advantages of be to lead to wide variety of main cause in clinical practice, and in order to Technique is avoided excessively to rely on the experience of clinician, the qualitative reference of scientific and standard is that formulation surgery planning is indispensable Committed step.We, by substantial amounts of in vitro and zoopery, enhance quantitative criterion, and have PRELIMINARY RESULTS at present, Clinical practice is served with certain effect.But later data process and analysis during find, in equivalent environment, identical set Under standby and the same terms, same output can produce ablation areas area of different sizes, concludes therefrom that identical defeated Going out under power condition, power attenuation is different, leading to really be applied to structural power difference, thus producing ablation areas area Different phenomenons.If always using this data as the quantitative criterion in clinical practice, ablation can be produced not thoroughly, or damage normal The harm of tissue, causes error medically or accident.Thus it is proposed that measurement microwave ablation antenna pointed end power method, Reduce Medical error and harm, provide more accurate data for surgery planning.

Content of the invention

It is an object of the invention to provide a kind of measuring method, for improving the accuracy of ablation quantitation, it is surgery planning More accurate data is provided.

The present invention proposes with microwave ablation antenna pointed end power as reference quantity, measures its performance number, again quantitative, specification number According to standard.Microwave ablation antenna pointed end power refers to remove the complete net power of the loss power in output, is wherein lost Power includes the loss power of transmission line and the loss power of antenna itself.In measuring method, we make use of and are sent out by microwave In the n second before the physical platform that raw device, thermometric needle, operating platform, data collecting instrument and computer form, and then acquisition heating Temperature value on all points for measuring temperature, further according to performance number q in each point for measuring temperature unit volume of equations_r, due to this unit Performance number in volume is discrete point, it is integrated solve, finally gives microwave ablation antenna pointed end power.

The problem that this invention can be explained explanation equivalent environment, identical device and produces different ablation results under the same terms. Thus on the basis of considering power dissipation concerns, propose the problem of microwave ablation antenna loss power itself, and thus propose The concept of microwave ablation antenna pointed end power, the method proposing its measurement, thus improving the quantitative accuracy of ablation, have one Determine the reference frame of science.

Heretofore described microwave ablation antenna pointed end power is really to put on structural authentic and valid power, that is, Remove the complete net power of the loss power in output, wherein loss power includes connecting outfan and microwave ablation sky The loss of the transmission line of line and the microwave ablation antenna loss power of itself, remaining power is then referred to as microwave ablation antenna Most advanced and sophisticated power.

Concrete technical scheme is as follows:

The measuring method of microwave ablation antenna pointed end power, based on by microwave generator, thermometric needle, operating platform, data Acquisition Instrument and the physical platform of computer composition, comprise the following steps:

(1). set point for measuring temperature distributed areas, described point for measuring temperature distributed areas are to be with the ablation antenna of microwave generator The rectangular area on one side, in this region, each point for measuring temperature is uniformly distributed by row, column, and string point for measuring temperature is distributed in ablation antenna On；

(2). open microwave generator, obtain the temperature value on all points for measuring temperature in the n second before heating, because heating first 10 seconds The change of interior temperature only thinks relevant with energy transmitting, and the impact of negligible other factors, therefore n generally take 10；

(3). by the temperature value obtaining, try to achieve the linear relationship to time t for temperature t on each point for measuring temperature, thus trying to achieve The rate of change to the time for the temperature on each point for measuring temperature, i.e. slope value in linear relationship, that is,

(4). determine cylinder half shaft section, described cylinder half shaft section refers in point for measuring temperature distributed areas, for disappearing Melt antenna, in addition on three sides, the slope value of the temperature data of point for measuring temperature and time is exactly 0 rectangle；

Because ablation antenna is cylinder, it is four surface launchings when emitted energy, cause the Energy distribution applying It is cylinder it is possible to regard microwave generator effective temperature field as an equivalent general power cylinder.Cylinder has The countless sections crossing cylinder axis, the half divided equally along cylinder axis, as cylinder half shaft section, microwave generator effective temperature field In any one q on the half section of central shaft_rQ with corresponding point on cylinder half shaft section_rAll identical.Equivalent general power Cylinder can regard the cylinder that cylinder half shaft section is formed around ablation antenna as, therefore can be cut by determining cylinder semiaxis The border in face obtains equivalent general power cylinder, then can get microwave by integration in the range of equivalent general power cylinder and disappears Melt antenna pointed end power.

Measure one and half shaft sections on temperature when, effective range to be determined, otherwise cannot determine ablation antenna Energy distribution border, concrete grammar is, one is to require the thermometric needle the most nearby apart from antenna need to open from the place of ablation antenna Begin to measure, can not have distance with antenna, so both can ensure comprehensive verity of data, also ensure that effective standard of later stage calculating Really property.Two are to ensure that thermometric needle on other three sides of cylinder half shaft section just at optimum position, the particularity of this position It is that the temperature data that it collects is exactly 0, that is, with the slope value of timeOnly choose the slope value to the time for the temperature It is not 0 point for measuring temperature, remaining point for measuring temperature is considered Null Spot it is not necessary to be analyzed.After border determines, just melted The cylindrical concrete scope of equivalent general power that antenna produces, next calculates in each point for measuring temperature unit volume according to formula Performance number q_r, then in the cylindrical concrete scope of equivalent general power to q_rIntegration, you can to obtain microwave ablation antenna pointed end work( Rate.

(5). calculate performance number q in each point for measuring temperature unit volume in cylinder half shaft section_r, computing formula is as follows:Wherein ρ is tested tissue density, and c is tested tissue specific heat；

Performance number q_rComputing formula be according to classical bioheat equation, that is, pennes equation abbreviation obtains, Shown in pennes equation such as equation (1):

$\mathrm{\ρ}c\frac{\∂t}{\∂t}=\▿\·k\▿t+w_b{c}_b(t_a-t)+q_m+q_r---\left(1\right)$

In formula, ρ is tested tissue density (kg/m³), c is tested tissue specific heat (j/ (kg DEG C)), and k leads for tested tissue Heating rate (j/ (s DEG C of m)), t is tested tissue temperature (DEG C), and t is the time (s), c_bIt is blood specific heat (j/ (kg DEG C)), w_b It is hemoperfusion rate (kg/ (m³S)), t_aFor entering the blood heat (DEG C) of the thermal treatment zone, q_mRepresent the metabolic heat production of biological tissue (j/(m³S)), q_rRepresent external heat source heating load.

According to the feature of thermotherapy ablation, it is in 10s in the persistent period of energy transmitting, only thinks emitted energy Apply just to cause the change of temperature, and the impact to temperature change for the thermal diffusion between organizing can be considered minimum, and conduction of heat and right Stream just can affect on Temperature Distribution after 10s, therefore in the front 10s of energy transmitting, you can ignore conduction of heat and convection current Impact, only consider energy launch this unique influence factor to tissue impact, then conduction of heat can be considered zero (k t ≈ 0).Meanwhile, the present invention is carried out based on imitated NDVI, does not have the metabolism in biological heat heat transfer equation and blood to fill Note, so q in equation (1)_mAnd w_bIt is zero, is therefore based on above-mentioned theory, equation (1) abbreviation can be equation (2):

$\mathrm{\ρ}c\frac{dt}{dt}=q_r---\left(2\right)$

Wherein ρ and c is all known；

(6). in microwave generator effective temperature field to step (5) in obtain in each point for measuring temperature unit volume power Value q_rIntegration, obtain microwave ablation antenna pointed end power, described microwave generator effective temperature field refer to cylinder half shaft section around The cylinder that ablation antenna is formed, wherein in microwave generator effective temperature field, any one is on the half section of central shaft q_rQ with corresponding point on cylinder half shaft section_rAll identical, described microwave ablation antenna pointed end power is to remove in output Loss power complete net power.

Understood according to the equation (2) in step (5), ρ and c is all it is known that then existValue known case under can solve calculating Obtain q_rValue, whereinThe size of value is to heat the change of temperature rise curve that is, slope value in initial 10 seconds.Gather and process energy Amount launches the temperature value information in first 10 seconds, is understood according to equation (1), q_rThe heat providing for external heat source.But according to temperature The change of degree solves q_rIn the case of value, q_rIt is then the performance number in the unit volume of each point for measuring temperature, rather than microwave ablation sky The most advanced and sophisticated performance number of line.The data of final temperature of the present invention is the temperature value of each point for measuring temperature, is measured by thermocouple temperature measurement pin Arrive, and collected according to data collecting instrument, therefore in the problem solving microwave ablation antenna pointed end performance number, need to utilize The principle of integration is carried out, and wherein can be realized using matlab software, but be not limited to matlab program, also apply be applicable to other Software in carry out mathematic integral calculating.

Integration method described in step (6) is as follows:

I. in cylinder half shaft section, every string point for measuring temperature is equivalent to a row power points, calculates all row power points Row power, wherein row power be equal to each point for measuring temperature unit volume on performance number q_rDiscrete integration in permutation；

Ii. microwave generator effective temperature field is equivalent to the equivalent circumference of multiple different radiis, described equivalent circumference Refer to melt antenna as the center of circle, row power points rounds the circle obtaining；The equivalent circumference of multiple different radiis is equivalent to position Multiple energy points in a line, calculate the equivalent circumference power of each energy point, and wherein equivalent circumference power is equal to equivalent circular The row power of all corresponding row power points and the product of this equivalent circumference circle；

Iii., on energy point direction, discrete integration is carried out to the equivalent circumference power of all energy points, that is, obtains microwave Ablation antenna pointed end power.

Beneficial effect

Present invention firstly provides the concept of microwave ablation antenna pointed end power, and disclose a kind of measurement microwave ablation sky Line tip power method, more scientific according to the data that the present invention obtains, more rationally, can reduce because quantitative criterion not science and The error producing, can be preferably clinical practice service.

Brief description

Fig. 1 (a) is q before interpolation_rScattergram spatially,

Fig. 1 (b) is q after interpolation_rScattergram spatially,

Fig. 2 (a) is discrete q_rIntegration schematic diagram in a column direction,

Fig. 2 (b) is q_rEquivalent circulation integral schematic diagram after column direction integration,

Fig. 2 (c) is the integration schematic diagram on the direction being expert at after equivalent circulation integral.

Wherein, 1., equivalent general power place cylinder, 2., cylinder half shaft section.

Specific embodiment

The present embodiment is placed in sufficiently large imitated NDVI carrying out microwave ablation experiment, and the present invention uses axle pair The microwave antenna claiming, do so can ensure that space temperature field is poised for battle along microwave antenna axle.

This measurement process is to provide ablation energy based on microwave generator, thus be delivered to microwave by transmission line disappearing Melt on antenna, and put in tissue.The microwave generator that this measurement is selected is to adopt Nanjing Qinghai Microwave Electronics Inst. Produce mtc-3 type microwave generator, the producible microwave of this microwave generator be 2450 ± 50mhz, output can Power Regulation Rate is 0-100w, and antenna is using gap transmitting, slit width 1.5mm, 13mm from the front end.This microwave system is furnished with low-loss same Shaft cable transmission line, is connected with hard microwave active antenna.The surface of microwave antenna (a diameter of 1.9mm, long 150mm) has painting Layer, for preventing itself and tissue adhesion.

Use the change of thermometric needle collecting temperature in experimentation, experimental subject is put into operating platform.Operation Platform is made up of upper and lower two-layer flat board, up and down distance about 2cm, and has enough jacks on upper and lower two-layer horizontal plate, each The distance of jack difference is 0.5cm, and these jacks are used to fixing thermometric needle.The inserted mode of thermometric needle is by jack It is inserted vertically in tissue, and so that thermometric needle and microwave ablation antenna is in same level, wherein microwave ablation antenna is water Plug flat enters in experimental subject, is in plumbness with thermometric needle.

For collecting temperature, we used data acquisition instrument, this instrument is to be designed by Agilent company (agilent) And produce, model 34972a.Agilent34972a has 6.5 (22 bit) resolution, 0.0044% basic direct currents Voltage accuracy and extremely low reading noise, the sweep speed of up to 250 passages/second, can measure by thermocouple, thermal resistance and temperature-sensitive Direct current and alternating voltage that resistance provides.Compared with agilent34970a before, many two connectivity ports of this instrument, It is respectively network interface and usb interface.The interpolation of network interface is more beneficial for transmission and the connection of data, in collection and transmission more Fast.Using in agilent bench link data logger software process, by data collecting instrument, that is, Agilent34972a, highly effective gathering data, and real-time monitoring and analytical data, the later stage can be derived data file, be facilitated the later stage Analyzing and processing.Containing 3 module slots and 8 switches and control module inside agilent34972a, each draw-in groove can put into one Data collecting card, and data collecting card is to be connected with thermometric needle by wire.Used in this experiment, data collecting card is 34901a, is applicable to the transducer of General Multiplex typically scanning, and it is high density, the multi-functional scanning with 60 passages/second Speed is combined together, and adapts to diversified data acquisition application.

Because this experiment only needs to heat the temperature data change information of front 10s, therefore can be after heating one minute, can Close energy transmitter, stop experiment, then experiment can complete.After the completion of data acquisition, can from the temperature change file derived Check the temperature change of each point for measuring temperature, before choosing, the data of 10s carries out preliminary treatment and analysis, with heat time heating time simultaneously Increase, the temperature collecting also can gradually rise, and in the range of 1-10s, can form the linear relationship of a time and temperature, and This is carried out with linear fit, the slope value that thus can obtain heating front 10s isValue.The slope value now obtaining is each The slope value of individual point for measuring temperature, is Discrete Distribution, and is calculated according to above-mentioned equation (2) again, can obtain each thermometric Performance number in the unit volume of point, wherein unit are w/cm³.By discrete point, can get power in whole volume The power that the transmitting of value, as microwave ablation antenna applies.

Then we intend specifically showing our algorithm by once specifically testing data processing procedure.

First, by agilent data collecting instrument derive each point for measuring temperature heating 10 seconds in temperature information.According to These information, carry out linear fit to the temperature of each point for measuring temperature, thus the temperature obtaining each point for measuring temperature changes over time Slope valueCan get table 1 below.The position of laterally layouting of 0,1,2,3,4,5 expression points for measuring temperature of the first row in table 1, Unit is cm, and what wherein 0cm represented is the on position of microwave ablation antenna；Numerical value in the first row of the leftmost side represents longitudinally The position layouted, unit is cm, and wherein coordinate is the most advanced position of antenna for (0,0) point.

Our purpose is intended to each q putting that this cylinder half shaft section is recorded_rIn entirely cylindrical space Inside it is integrated, finally give equivalent general power p.In order to reach the accurate purpose of data, we are when arranging point for measuring temperature Can be more dense, also can be more comprehensively.The temperature spot of therefore measurement is to start to arrange at microwave ablation antenna, that is, the temperature measuring Including the temperature information of microwave ablation antenna, do so can more meet true experiment, also ensured the accuracy of data simultaneously.

The slope value that the temperature of each point for measuring temperature of table 1 changes over time

Further according to above-mentioned equation (2)Thus obtaining the q of each point for measuring temperature corresponding_r, it is as shown in table 2 below, Its unit is w/cm².

The q of each point for measuring temperature of table 2_r

In experiment, the temperature change of collection is the change of each point for measuring temperature temperature, can regard discrete point as, but this is discrete Point is the performance number obtaining under unit volume, is therefore split as twice for the integration of discrete point: the first step is to import q_r's Distribution, row interpolation of going forward side by side；Second step is q on the cylinder of whole space_rTriple discrete integration are carried out, the result finally obtaining It is the performance number under whole volume, that is, be applied to structural antenna pointed end performance number.

We use the mode that discrete point obtains the equivalent power of the total space, so the density degree of discrete point Just directly have impact on the accuracy of integral result, therefore arrange a large amount of and densely distributed thermometric needle in an experiment, every The spacing very little of thermometric needle is so that increment is infinitely small, more accurately processes and analytical data.Additionally can pass through Import q_rDistribution, row interpolation of going forward side by side, obtain new finer and closely woven q_rDistribution, the purpose of do so be can obtain more accurate Discrete integration result, the main code realizing this part is as follows:

Before and after interpolation, q_rDistribution spatially have some change, specifically can it is seen from figure 1 that, wherein Fig. 1 A () is interpolation before, after Fig. 1 (b) is interpolation.

Q after obtaining difference_rDistribution Value in the case of, we are on the cylinder of whole space to q_rCarry out three Weight discrete integration, thus having obtained equivalent general power, that is, the most advanced and sophisticated performance number of microwave ablation antenna, the premise of this algorithm Assume that the q of the corresponding point of any one cylinder semiaxis cutting plane of space_rThis all measured with us semiaxis of numerical value Section is identical, because the present invention uses axisymmetric microwave antenna, and also is placed in sufficiently large imitated NDVI Carry out microwave ablation experiment, do so can ensure that space temperature field along microwave antenna axial symmetry, it is therefore assumed that being rational. Specific algorithm is as follows:

After checking is assumed rationally, we are integrated to whole discrete data successively.

Fig. 2 (a)-(c) illustrates the process of whole discrete integration, and the in figure direction of arrow is our integration direction, Fig. 2 A, in (), we are the discrete q to string every in cylinder half shaft section_rValue is integrated, and that is, the numerical value of each point is multiplied by each point and accounts for The length of infinitesimal add again and.During Practical Calculation, row power is equal to performance number q in each point for measuring temperature unit volume in permutation_rWith Adjacent thermometric dot spacing from product adduction；We carry out such discrete integration to every string, thus obtaining as Fig. 2 B the disk shown in (), that the point in plane represents is corresponding row q_rIntegrate the total value obtaining, that is, all row power points are in list The row power that plane amasss.Then we carry out circumference calculating to each total value, that is, calculate to melt antenna as round dot, to scheme Point in 2 (b) to the center of circle distance be radius circle girth, then this girth again with corresponding to this point shown in Fig. 2 (b) Row q_rIntegrate the total value obtaining to be multiplied, obtain the total value of every layer of circumference.This total value is the point in Fig. 2 (c).Then to Fig. 2 C in (), these values proceed discrete integration, that is, the value of each point be multiplied by the representative infinitesimal length of each point add again and, finally Obtain equivalent power, that is, the most advanced and sophisticated performance number of microwave ablation antenna, during Practical Calculation, the equivalent circumferential work of each energy point Then all energy points are carried out cumulative summation and are equivalent work(by the product of distance between rate and this energy point and adjacent energy point Rate.

This whole algorithm part is realized by matlab, and this is only an EXPERIMENTAL EXEMPLIFICATIONThe part, this algorithm It is not limited to matlab program, also apply be applicable to carry out mathematical calculation in other softwares.

The equivalent power that finally we can be calculated under 60w input power is 46.3407w, so the efficiency of this system is 77.24%.

Claims (3)

1. the measuring method of microwave ablation antenna pointed end power, adopts based on by microwave generator, thermometric needle, operating platform, data The physical platform of collection instrument and computer composition is it is characterised in that comprise the following steps:

(1). set point for measuring temperature distributed areas, described point for measuring temperature distributed areas be with the ablation antenna of microwave generator for Rectangular area, in this region, each point for measuring temperature is uniformly distributed by row, column, and string point for measuring temperature be distributed in ablation antenna on；

(2). open microwave generator, obtain the temperature value on all points for measuring temperature in the n second before heating, n is less than or equal to 10；

(3). by the temperature value obtaining, try to achieve the linear relationship to time t for temperature t on each point for measuring temperature, thus trying to achieve each The rate of change to the time for the temperature on point for measuring temperature, i.e. slope value in linear relationship, that is,

(4). determine cylinder half shaft section, described cylinder half shaft section refers in point for measuring temperature distributed areas, for melting sky Line, the slope value that in addition on three sides, the temperature data of point for measuring temperature changes over time is exactly 0 rectangle；

(5). calculate each point for measuring temperature unit volume (cm in cylinder half shaft section³) on performance number q_r；

(6). in microwave generator effective temperature field to step (5) in obtain in each point for measuring temperature unit volume performance number q_r It is integrated, obtains microwave ablation antenna pointed end power using integration method, described microwave generator effective temperature field refers to justify The cylinder that post half shaft section is formed around ablation antenna, wherein in microwave generator effective temperature field, any one is through central shaft Half section on q_rQ with corresponding point on cylinder half shaft section_rAll identical, described microwave ablation antenna pointed end power is to remove Go the complete net power of the loss power in output.

2. microwave ablation antenna pointed end power according to claim 1 measuring method it is characterised in that: in step (6) Described integration method is as follows:

I., in cylinder half shaft section, every string point for measuring temperature is equivalent to a row power points, calculate all row power points Unit area (cm²) on row power, wherein unit area (cm²) on row power be equal to each point for measuring temperature unit volume (cm³) On performance number q_rDiscrete integration in permutation；

Ii. microwave generator effective temperature field is equivalent to the equivalent circumference of multiple different radiis, described equivalent circumference refer to Ablation antenna is the center of circle, and row power points rounds the circle obtaining；The equivalent circumference of multiple different radiis is equivalent to positioned at one Multiple energy points on row, calculate the equivalent circumference power of each energy point, and wherein equivalent circumference power is equal to equivalent circumference pair The row power of the row power points answered and the product of this equivalent circumference circle；

Iii., on energy point direction, discrete integration is carried out to the equivalent circumference power of all energy points, that is, obtains microwave ablation Antenna pointed end power.

3. microwave ablation antenna pointed end power according to claim 1 measuring method it is characterised in that: each thermometric Point unit volume (cm³) on performance number q_rComputing formula as follows:Wherein ρ is tested tissue density, c be by Survey tissue specific heat.