JP2002542839A - Skin blood flow measurement - Google Patents

Abstract

(57) [Summary] A skin blood flow measurement device (10) imparts a predetermined temperature gradient to a part of the skin, thereby changing the temperature at that location from a first temperature to a second temperature. Operating a device (12), a single temperature sensing member (14) for measuring a temperature at a selected position near a part of the skin, and a device (12) for applying the predetermined temperature gradient; A control device (20) for operating a detection member (14) in first and second operation modes, wherein in the first mode, the temperature detection member (14) sets a first reference temperature at the selected position. Measuring, in the second mode, the temperature sensing member (14) is operable to measure a second temperature at the selected position, and the control device (20) comprises: Between the first and second temperatures A control device (20) for operating the device (12) for applying the predetermined temperature gradient so as to maintain the predetermined gradient, and a processing device (47) related to the temperature detection member (14). And a processor (47) for evaluating a skin blood flow corresponding to the measured first and second temperatures and a steady-state power required to maintain the predetermined temperature gradient.

Description

DETAILED DESCRIPTION OF THE INVENTION

 FIELD OF THE INVENTION The present invention relates to non-invasive techniques and devices for measuring skin blood flow.

BACKGROUND OF THE INVENTION In various medical applications, for example, to obtain information about skin function, to treat skin burns and skin ulcers, to perform skin transplantation, and to evaluate peripheral hemodynamics In this case, measurement and / or monitoring of skin blood flow is important.

[0002] Methods for non-invasively measuring skin blood flow by locally heating an area of skin and measuring the temperature difference at the skin surface are known in the art. The heated area is cooled by various heat transfer mechanisms, among other things, conduction by the skin and convection by the skin blood flow. Known or estimated or measured variables include input heating or cooling power, temperature differences, and heat transfer factors that take into account the various heat transfer mechanisms described above. The unknown or estimated blood flow is calculated by substituting these known or estimated or measured variables into the well-known heat conduction equation.

[0003] Performing the above procedure using a disk-shaped sensor is well known in the art. The disc includes two main members: a centrally located heated measurement member and a peripherally located reference measurement member. The temperature difference between the central heating member and the peripheral reference member is measured and monitored.

One type of disk sensor measures the temperature difference while keeping the thermal power input constant. Such a configuration is described, for example, in A. V. J. Challoner
Accurate measurement of skin blood
flow by a thermal conductance method
d ", Medical and Biological Engineeri
ng, 1975, 13: 196-201; Thalaya
singam and D.S. T. Delpy's "Thermal cleara
nce blood flow sensor-sensitivity,
linearity and flow depth discrimina
Tion ", Medical and Biological Engineering
ering & Computing, 1989, 27: 394-398.

Another type of disk sensor measures the thermal power input while keeping the temperature difference constant. Such a configuration is described, for example, in A. Dittmar's "Skin T
Thermal Conductivity ", edited by JC Leveque," Cutaneous Investigation In Health. "
And Disease ", New York, Marcel Dekke
r, 1989, 323-335; M. Greenhal
gh, J.A. R. Jones and J.M. S. Yudkin's "The
57 mm thermal clearance probe: a non
-Invasive tool for measuring subcuta
neous blood flow ", Clinical Science,
1989, 77: 121-127.

Other publications describing skin blood flow measurements include Amost Fro
Nek's "Noninvasive evaluation of the c"
utaneous circulation ", Chapter 27, p
p. 269-279, "Vascular Diagnostics", E.I.
F. Bernstein, Mosby Publishing, Pierre G. Ag
Ache and Anne-Sophie Dupond's "Recent Ad"
vences in Non-invasive Assessment of
Human Skin Blood Flow ", Acta Derm V
enereol, 1994, Suppl. 185: 47-51; N
Itzan et al.'s "Theoretical Analysis of the
Transient Thermal Clearance Method f
or Regional Blood Flow Measurement ",
Medical and Biological Engineering
& Computing, 1986, 24: 597-601; Nit
Zan et al.'s “Faster Procedure for Deriving”
Regional Blood Flow by the Noninvasi
ve Transient Thermal Clearance Metho
d ", Annals of Biomedical Eng., 1993,
21: 259-262; Delhomme, W.C. H. Newma
n, B. Roussel, M .; Jouvet, M.A. F. Bowm
and A. Dittmar's "Thermal Diffusion P
probe and Instrument System for Tissue
e Blood Flow Measurements: Validatio
n in Phantoms and in Vivo Organs ", I
EEE Transactions on Biomedical Engineering
eering, Vol. 41, No. 7, July 1994, and F.E. Arnaud, G .; Delhomme, A .; Dittma
r, p. Gird, L.A. Netchiporook, C .; Ma
rtlet, R.L. Cespuglio and W.C. H. Newman ’s
A Microthermal Diffusion Sensor for
Non-invasive Skin Characterization ",
Sensors and Actors A, 41-42 (199
4). In the latter document, a transient heating method is used.

[0007] FR8 of CNRS (National Science Research Center) in Lyon, France
5-15-932 describes a constant temperature difference sensor and was used in the Dittmar study above. This disk sensor has several disadvantages. First, the principle of measuring the thermal power input while maintaining a constant temperature difference is based on the reference temperature (
This is true, for example, when the temperature of the blood flowing under the skin at the point where the sensor is attached (temperature of the blood) is constant. However, in the case of this disk sensor, the reference temperature is the temperature around the disk. This ambient temperature is not constant and rises during measurement due to heat conducted from the central heater to the periphery of the disk. Second, the sensor has multiple thermocouples located between the center and the periphery of the disc, but keeping the heat away from the skin adversely affects the accuracy of the measurement. Third, the sensor is very expensive to manufacture because it has more than 20 members made from six different materials.

[0008] Dittmar et al., FR 9011773, describes a sensor similar to that described in FR 85-15-932, supra. Dittmar's sensor
Although improved with more advanced materials and techniques, they have essentially the same problems as previous sensors.

Japanese Patent Application Laid-Open No. 6-217952 describes a skin blood flow sensor having an inner disk for measuring temperature, an outer ring, and a heating or cooling member. FR85-15-9
This sensor, which has a configuration similar to that of F.32 and FR9011173, also suffers from similar disadvantages.

(Summary of the Invention) An object of the present invention is to provide an apparatus and a method for measuring skin blood flow.
The present invention derives blood flow based on a predetermined temperature difference between a first reference temperature and a second temperature and a controlled steady-state thermal power input. Using a single temperature sensor,
Measure both the first temperature and the second temperature. This means that before applying a positive predetermined temperature gradient (due to heating) or a negative predetermined temperature gradient (due to cooling) to the skin,
Is measured by storing the first temperature in a memory. Unlike the prior art, the same temperature sensor is used to measure both the first temperature and the second elevated temperature, thereby further reducing the power supplied to maintain the second temperature level. Direct measurement becomes easy.

Therefore, according to a preferred embodiment of the present invention, the skin blood flow measuring device applies a predetermined temperature gradient to a part of the skin, whereby the temperature at the location is increased from the first temperature to the first temperature. 2, a single temperature detecting member for measuring a temperature at a selected position near a part of the skin, and a device for applying the predetermined temperature gradient, and the temperature detecting member In a first and a second operation mode, wherein the temperature detecting member measures a first reference temperature at the selected position in the first mode, and the temperature in the second mode. The sensing member is operable to measure a second temperature at the selected position, and the controller maintains the predetermined gradient between the first and second temperatures in the second mode. like Operating a device for applying the predetermined temperature gradient, a control device, a processing device associated with the temperature sensing member, skin blood flow corresponding to the measured first and second temperatures, A processing device for evaluating the steady-state power required to maintain the predetermined temperature gradient, and a skin blood flow measuring device.

Further, according to a preferred embodiment of the present invention, there is provided a memory associated with the temperature detecting member, wherein the memory stores the reference temperature.

Further, according to a preferred embodiment of the present invention, there is provided a visual display associated with the processing device, the visual display displaying at least the ascending skin blood flow.

Further, according to a preferred embodiment of the present invention, a device for imparting the predetermined temperature gradient and a heat insulating portion for insulating the temperature detecting member from the surrounding environment are provided.

According to an embodiment of the present invention, the device for applying the predetermined temperature gradient includes an electric heating device.

Further, according to a preferred embodiment of the present invention, the temperature detecting member is a silicon diode, and can be used as an electric heating device.

Further, according to a preferred embodiment of the present invention, each of the electric heating device and the temperature detecting member is a silicon diode, and the silicon diodes are
Are arranged in one diode array.

According to another embodiment of the present invention, there is provided a method of measuring skin blood flow in a portion of skin, comprising activating a temperature sensor in contact with the portion of skin, whereby Measuring a first reference temperature; storing the value of the first temperature; and applying a predetermined temperature gradient to a part of the skin, whereby the temperature at that location is reduced to the first temperature. To a second temperature, and stabilizing the skin temperature at the second temperature; determining the power required to maintain the predetermined temperature gradient; skin blood flow; Assessing blood flow associated with the portion of the skin according to a predetermined relationship between a steady-state power required to maintain a temperature gradient and the predetermined temperature gradient. You.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, taken in conjunction with the drawings, provides a more thorough understanding of the present invention.

Reference is now made to FIG. 1, which shows a skin blood flow measurement device 10 constructed in accordance with a preferred embodiment of the present invention and operable in accordance with the same embodiment.

Preferably, the device 10 includes a device for giving a predetermined change to the temperature of the skin (illustrated as the heater 12 in the present embodiment), and a temperature sensor 14. The heater 12 is a micro heater or a foil type heater (foil type).
The preferred type of heater is a silicon diode, although it can be any conventional heater, such as a resistance heater. Temperature sensor 14
Can be any conventional temperature sensor such as a thermocouple or a thermistor, but the preferred type of sensor is a silicon diode. The heater 12 and the temperature sensor 14 can be integrated, preferably as a miniaturized silicon diode array.

Preferably, the heater 12 and the temperature sensor 14 are coupled inside a thermal insulator 16 that insulates them from the surrounding environment. Insulator 16 may be made of any suitable material with low thermal conductivity, such as plastic, and may be painted or coated with a material that reduces radiative heat transfer losses. The temperature sensor 14 is a thermal adhesive (therm)
The heater 12 may be attached to the heater 12 by a thermal bonding material such as al adhesive. Instead of or in addition to the above configuration, the internal space of the insulator 16 is
It may be filled with an insulating or sealing material such as TV.

The temperature sensor 14 and the heater 12 are preferably in communication with a control and display unit 20 that processes data received from the temperature sensor 14 and the heater 12. The control and display unit 20 preferably includes one or more function keys 22 and a display 24 showing a visual output of the measured blood flow. Unit 20 may be configured to provide additional information, such as a measured temperature, as needed.

Reference is now made to FIGS. 2A and 2B, which are simplified block diagrams showing the device 10 in the first and second modes of operation. Those skilled in the art will appreciate that the circuitry shown in FIG. 2 that constitutes the control and display unit 20 is merely exemplary. Thus, in the present invention, other circuits and / or devices, such as suitable integrated circuit devices, configured to perform similar control and data processing functions may be used instead of those shown.

Preferably, the heater 12 and the temperature sensor 14 are both grounded.
In the embodiment shown, it can be seen that the heater 12 is connected to the input of the differential amplifier 30 and the output of the switch 32 via a resistor 31 in the figure.
Temperature sensor 14 is preferably connected to the input of amplifier 34 and to the non-inverting input of differential amplifier 36. Preferably, the output of amplifier 34 is connected to the input of a switch 38 whose output is connected to memory member 39. In the illustrated embodiment, the memory member 39 includes a capacitor 40 and an amplifier 4 as shown.
2 inclusive. The output of switch 38 is connected to capacitor 40 and amplifier 4 as shown.
Connected to both inputs. Preferably, the output of amplifier 42 is connected to the inverting input of differential amplifier 36 and to a first input 43 of switch 44. Preferably, the output of differential amplifier 36 is connected to the input of switch 32 via power amplifier 46. Preferably, the output of differential amplifier 30 is connected to a second input 45 of switch 44.
And from there to the display 24 via a suitable processing circuit 47. Preferably, the control inputs of switches 32, 38 and 44 are connected to corresponding inputs of synchronizer 50. Preferably, the input of synchronizer 50 is connected to timer 52. Timer 52 provides an impulse to synchronizer 50 to control the state of switches 32, 38 and 44.

Here, the control and display unit 20 according to the preferred embodiment of the present invention
Will be described.

Referring now to FIG. 2A, in the first mode of operation, switch 32 is open, switch 38 is closed, and switch 44 is set to input 43. Therefore, in the initial state, power is not supplied to the heater 12, and the temperature sensor 14 detects the first temperature, i.e., "
Measure the "reference" temperature. The first temperature may be measured directly on the heater 12 as shown in the figure, or may be measured at a position below the heater 12. This first temperature is passed through the amplifier 34, the switch 38, the amplifier 42, and the switch 44,
Preferably, it is further provided to the display 24 via a processing circuit 47. Further, the first temperature is stored in the memory member 39. As described above, the memory member 39 can be composed of the capacitor 40 and the amplifier 42.

In the second mode of operation shown in FIG. 2B, switch 32 is closed, switch 38 is open, and switch 44 is set to input 45.
A reference voltage corresponding to the first reference temperature is provided to the input of differential amplifier. The output signal from differential amplifier 36 is provided to heater 12 via power amplifier 46 and switch 32, thereby providing a thermal feedback signal to stabilize the temperature of heater 12 at a second temperature. In the case of this embodiment for heating the skin, the second temperature is
The temperature is higher than the first temperature. Neither the first temperature nor the second temperature is predetermined, but the difference between the two, ie, the “temperature gradient”, is predetermined. Thus, since the first temperature is substantially constant and the temperature difference between the first and second temperatures is predetermined, the second temperature regulated by the voltage / current output of power amplifier 46 is also substantially constant. Is maintained at the level of.

The magnitude of the steady power required to maintain this temperature gradient is proportional to the heater current from power amplifier 46. Thus, the following equation: V = kIU / (dT), where V = skin blood flow k = coefficients which depend, inter alia, on the thermal conductance of the skin and the thermal properties of the blood I = stationary heating current U = heater voltage dT = stationary The temperature gradient in the condition can determine the skin blood flow.

Thus, since the heater voltage is constant and the temperature gradient (dT) is constant, it can be seen that the skin blood flow is directly proportional to the heater current (I). The heater current is controlled by the resistor 3
1 through the differential amplifier 30 and the switch 44
As input. The processing circuit 47, which may be, for example, a simple amplifier, is operable to calculate the skin blood flow (V) according to the above equation,
The display 24 is operated to show the visual output of V).

One of the features of the present invention is to measure the reference temperature and the second temperature with a single temperature sensor.

In another embodiment of the present invention, the silicon diode described above as suitable for forming the temperature sensor 14 may be used as a heater if a current sufficient for self-heat is applied. Can also be used. In this self-heating mode, the silicon diode is operable not only to heat the skin, but also to measure the first and second temperatures. Therefore, in the present embodiment, the separate heater 12 shown and described above becomes unnecessary, and the functional configuration shown in FIGS. 2A and 2B is changed accordingly.

Referring now briefly to FIG. 3, FIG. 3 shows skin blood, generally designated 10 ′, constructed and operable in accordance with another embodiment of the present invention. A flow measurement device is shown. The configuration of the device 10 ′ is the same as that of the device 10 (FIGS. 1 and 2).
A and FIG. 2B), the present apparatus 10 ′ and the apparatus 10 ′ are used here.
Details other than those that differ between the above will not be described in detail.

The heater 12 ′ and the temperature sensor 14 ′ are both silicon diodes, which are configured as a diode array in a thermally insulated housing 16 ′ that is substantially similar to the insulator 16 shown and described in FIG. You can see that it is done. The apparatus also includes a control and display unit, labeled 20 ', similar to the units shown and described in FIGS. 2A and 2B.

In particular, the case where a positive thermal gradient is applied to the skin has been described as an example. However, it is understood by those skilled in the art that the present invention can be implemented by applying a negative thermal gradient, that is, cooling.

Those skilled in the art will also understand that the present invention is not limited to what has been particularly shown and described in the foregoing description. Rather, the scope of the present invention is defined solely by the appended claims.

[Brief description of the drawings]

FIG. 1 is a simplified cut-away view showing a skin blood flow measurement device constructed in accordance with a preferred embodiment of the present invention and operable in accordance with the same embodiment.

FIG. 2A is a simplified block diagram showing a skin blood flow measurement device configured according to the preferred embodiment of the invention shown in FIG. 1 and operable according to the first embodiment in a first mode of operation.

FIG. 2B is a simplified block diagram showing a skin blood flow measurement device configured in accordance with the preferred embodiment of the present invention shown in FIG. 1 and operable in accordance with the second embodiment in a second mode of operation.

FIG. 3 is a schematic block diagram showing a skin blood flow measuring device constructed according to the present invention and operable according to the present invention, wherein both the temperature detecting device and the heating device are composed of silicon diodes.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (GH, KE, LS, MW, SD, SZ, UG, ZW) , EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, HU, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT , LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, TJ, TM, TR, TT, UA, UG, US, UZ, VN [Continuation of summary] 7).

Claims (11)

[Claims] 1. A skin blood flow measuring device, comprising: means for imparting a predetermined temperature gradient to a part of the skin, thereby changing the temperature at that location from a first temperature to a second temperature. A single temperature sensing member for measuring a temperature at a selected position near a part of the skin, and a means for applying the predetermined temperature gradient, and operating the temperature sensing member in first and second operation modes In the first mode, the temperature detecting member measures a first reference temperature at the selected position, and in the second mode, the temperature detecting member measures a second reference temperature at the selected position. Operable to measure the temperature of the first temperature gradient in the second mode to maintain the predetermined temperature gradient between the first and second temperatures. Controlling means for operating the applying means; Processing means associated with the temperature detecting member for evaluating skin blood flow corresponding to the measured first and second temperatures and steady-state power required to maintain the predetermined temperature gradient Means for measuring skin blood flow, comprising: 2. The apparatus according to claim 1, further comprising memory means associated with said temperature sensing member, wherein said memory means stores said reference temperature. 3. The apparatus of claim 1, further comprising visual display means associated with said processing means, wherein said visual display means displays at least said evaluated skin blood flow. 4. The apparatus according to claim 1, further comprising: means for applying said predetermined temperature gradient and heat insulating means for insulating said temperature detecting member from an ambient environment. 5. The apparatus according to claim 1, wherein the means for applying the predetermined temperature gradient includes an electric heating means. 6. The temperature detection member includes a silicon diode.
An apparatus according to claim 1. 7. The apparatus of claim 6, wherein said silicon diode is operable to also function as said electric heating means. 8. The apparatus according to claim 5, wherein said electric heating means and said temperature sensing member each comprise a silicon diode, said silicon diodes being arranged in one diode array. 9. A method for measuring skin blood flow at a portion of the skin, comprising: activating a temperature sensor in contact with the portion of the skin, thereby measuring a first reference temperature at the location. Storing the value of the first temperature, and applying a predetermined temperature gradient to a part of the skin, thereby changing the temperature at the location from the first temperature to the second temperature. Stabilizing the skin temperature at the second temperature, determining the power required to maintain the predetermined temperature gradient, skin blood flow, and the steady state required to maintain the predetermined temperature gradient. Assessing blood flow associated with the portion of the skin according to a predetermined relationship between power and the predetermined temperature gradient. 10. The evaluation step is performed by the following equation: V = kIU / (dT) where: V = skin blood flow k = predetermined coefficient I = steady current U required to maintain the predetermined temperature gradient U The method according to claim 9, wherein = the voltage required to maintain the predetermined temperature gradient dT = the predetermined temperature gradient. 11. The step of applying a predetermined temperature gradient to a portion of the skin electrically heats a portion of the skin, thereby increasing a temperature at the location from the first temperature. 10. The method according to claim 9, comprising raising the temperature to a temperature of 2.