WO1999035474A1

WO1999035474A1 - Thermometer and thermometer reader

Info

Publication number: WO1999035474A1
Application number: PCT/US1998/027316
Authority: WO
Inventors: Leonard Reiffel
Original assignee: Leonard Reiffel
Priority date: 1998-01-05
Filing date: 1998-12-21
Publication date: 1999-07-15
Also published as: AU2091399A; EP1046024A1

Abstract

An expanding fluid thermometer is located in a body from where the thermometer is not visible and is read by imagers such as X-ray imagers and acoustic imagers.

Description

TITLE OF THE INVENTION

Thermometer and Thermometer Reader

CROSS REFERENCES TO RELATED APPLICATIONS This application claims benefit of U S Provisional Application No 60/070,399 filed January 5, 1998

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

BACKGROUND OF THE INVENTION

The invention is a thermometer which is located in a body from where the thermometer is not visible and a reader which reads the thermometer using imagers such as x-ray imagers and acoustic imagers There are occasions when it is necessary to measure the temperature in a body and existing temperature sensors such as thermocouples and resistance thermometers are not adequate For example, when a cancerous tumor is treated by hyperthermia or cryotherapy it is very important to control the temperature in the tumor as well as the temperature in healthy tissue, but existing temperature sensors are not adequate to the task Thus, workers have long been seeking new ways to measure the temperature for such cases Prior art shows some interesting attempts at solving this problem

An implanted reflector which reflects a microwave signal as a function of temperature is shown by Nowogrodzki in U S Patent 4, 138,998 An implanted element which has temperature dependent nuclear magnetic resonance properties is shown by Taicher in U S Patent 5, 109.853 Both of these solutions to the problem require rather complicated apparatus to read the implanted elements with temperature dependent properties

The invention shown here is based on the discovery that a small uncomplicated expanding fluid thermometer can be made such that when it is located in a body it can be read by using uncomplicated x-ray sources and x-ray imagers which are commonly used by manufacturers for inspecting parts and are readily available and easily used This solution is not suggested in any prior art nor any combinations of prior art

SUMMARY OF THE INVENTION Objects of this invention comprise requirements listed in the following imperatives. Make a thermometer which can be located in a body from where the thermometer is not visible and a reader which can read the thermometer using imagers such as x-ray imagers and acoustic imagers. Make the thermometer enclose a column terminated at one end by a bulb, with the bulb and the column containing a fluid which expands along the column to a fluid length which is a function of the temperature of the bulb, the fluid providing contrast for the reader

Objects of alternative forms of the invention comprise requirements listed in the following imperatives Provide means for moving the reader to read a plurality of thermometers. Provide markers on the thermometers so that they can be distinguished one from another by the reader Feed a component of a reader output signal to a control system to control a process in the body. Make the reader an x-ray reader which images x-radiation from through the fluid to produce an output signal which is a function of the fluid length and thus a function of the temperature of the bulb. Make the x-ray reader from an x-ray source and an x-ray imager which produces a visual signal which can be read directly to determine the temperature of the bulb Give the x-ray imager a large field stage used to locate the image of the bulb and a high resolution stage which produces a high resolution image of the fluid in the column. Make an x-ray reader from an x-ray source and an x-ray imager which are moved to image the fluid from two different angles and produce two output signals from which a data processor calculates the temperature of the bulb. Make an x-ray reader from two x-ray sources and two x-ray imagers which image the column from two different angles and produce two output signals from which a data processor calculates the temperature of the bulb. Modulate the x-radiation by oscillation of filters made of materials which have different x-radiation absorption edges so that modulated x-radiation used to image the fluid can be distinguished from any other x-radiation present. Make the thermometer of materials which are biodegradable and alternatively are bio-compatible.

Other objects will be comprehended in the drawings and detailed description, which will make additional objects obvious hereafter to persons skilled in the art.

In summary one embodiment of this invention has a thermometer which encloses a column terminated at one end by a bulb, the bulb and the column containing a fluid which expands along the column to a fluid length which is a function of a temperature of the bulb, the thermometer being located in a body from where the thermometer is not visible, and has a reader which images the fluid and produces an output signal which is a function of the fluid length and thus is a function of the temperature of the bulb. Other equivalent embodiments will be comprehended in the drawings and detailed description, which will make additional equivalent embodiments obvious hereafter to persons skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross section of the thermometer. FIG 2 shows the thermometer in a body and shows an x-ray reader

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The thermometer 15 is shown in FIG 2 located in a body 91 from where the thermometer is not visible. A cross section 10 of the thermometer 15 is shown in FIG. 1. The thermometer 15 encloses a column 11 and a bulb 12 The bulb terminates the column at one end. The bulb and the column contain a fluid 13 which expands along the column to a fluid length 14 which is a function of the temperature of the bulb The fluid length 14 extends along a long axis 16 of the thermometer. The fluid is chosen to provide contrast for a reader described below

A set of markers 71 is shown attached to the thermometer at the bulb end of the thermometer and at the end away from the bulb Sets of markers comprising various combinations of markers can be used as identifying sets of markers in order to distinguish one thermometer from a sequent thermometer. A marker in a set can also be used as a gauge marker to calibrate an image of a thermometer as described below The markers shown are depicted as knobs but various other marking means can be used such as enclosing markers in the thermometer The markers in a set of markers are chosen to provide contrast for a reader described below The bulb 12 can be given various shapes which can be distinguished by a reader and this can comprise a set of markers which can take the place of the set shown 71

Dimensions of an example thermometer which can be implanted in living tissue, for example by using standard biopsy techniques, are length of thermometer 20 mm, column inside diameter 50 microns, bulb length 5 mm, bulb inside diameter 0 75 mm, bulb outside diameter 1 25 mm. thermometer outside diameter away from bulb 90 microns A suitable fluid in a thermometer with these dimensions will expand along the column at about 1 mm per degree Celsius. Thus, for example, if an accuracy of OJ Celsius degrees is required, then the fluid length must be measured to an accuracy of OJ mm. This sensitivity is that sought in hyperthermia treatments of cancerous tumors. Smaller and larger thermometers can be made as needed for specific applications with more or less stringent requirements for size and sensitivity

When the thermometer 15 is located in the body 91 the thermometer is not visible. The statement "the thermometer is not visible" means that the fluid length can not be measured, to an accuracy required by an application such as that described above, using visible light. Thus, the thermometer must be read by a reader which does not use visible light, such as an x-ray reader shown and an acoustic reader not shown. For these readers the principles of operation are parallel: a beam (x-radiation or acoustic energy) enters the body and interacts with the fluid and after interaction (by reflection or transmission for the acoustic case and by transmission in the x-ray case) the beam is read by an imager which produces an output signal which is a function of the fluid length and thus a function of the temperature of the bulb.

An x-ray reader is preferred because sufficient resolution can be obtained using easily available and easily used equipment. Only embodiments of an x-ray reader are described. Other readers such as acoustic readers and readers using other wavelengths of electromagnetic radiation have features parallel to features of the various forms of x-ray readers described below. Thus these other readers with parallel features can be substituted in cases where they are appropriate.

One form of an x-ray reader comprises a first x-ray source 21 and a first x-ray imager 41 shown in FIG. 2. The first x-ray source 21 produces a first beam of x- radiation indicated by a vector 22 along the first beam left edge, a vector 23 along the first beam right edge, and a vector 24 along the central ray of the first beam. The central ray vector 24 crosses the column 11 at a first angle 25 relative to the long axis 16 of the thermometer.

The preferred form of the first x-ray imager is a high resolution imager, such as a microchannel plate detector, which feeds a transducer, such as a CCD video camera, which produces a first imager output signal 42 which is input 61 to a data processor 62 which then produces a reader output signal 63. The reader output signal is functionally related to the fluid length and thus functionally related to the temperature of the bulb. The reader output signal can indicate the temperature of the bulb in various ways for example by a graphic display of an image of the thermometer with temperature indices along the image of the column. The reader output signal 64 can have various visual, audible, and even tactile components chosen to match the conditions of use. The reader output signal can also have a component 64 which is a feed back signal for a control system (not shown) in order to control a process in the body. The output of a microchannel imager, for example, can be viewed directly in which case this is the reader output signal. Other x-radiation detectors can be used including detectors which produce a digital output directly.

The image of the fluid in the column which is formed by the x-ray detector is functionally related to the fluid length 14 in the column and the first angle 25. Because the first x-ray beam diverges from a very small spot (9 microns for example) the projection of the column at the x-ray detector is magnified by a factor depending on the distances between the source 21 and the column 11 and between the column and the x- ray imager 41. In a typical set up there can be a magnification factor which produces a fluid length image which is five times as long as the fluid length. At this magnification a one Celsius degree change in temperature of the bulb of the example thermometer described above will produce a change in the fluid length image of about 5 mm, if the first angle is 90 degrees.

The image of the fluid length at the x-ray imager 41 is reduced because of the first angle 25. The fluid length 14 in the column can be determined from the image of the fluid length by determining a calibration length. This is done by measuring a gauge length between the bulb and a gauge marker on the thermometer and measuring a calibration length between the bulb and the gauge marker on the image of the thermometer. From this and the magnification factor, determined as described above, the fluid length can be determined.. The gauge marker can be one of a set of markers like 71. Alternatively, the length of the bulb can be the gauge length and the length of the image of the bulb can be the calibration length. A series of gauge markers can be provided at measured gauge lengths along the column so that if only a portion of the thermometer is imaged, then the distance between two gauge markers can be used to make this calibration. This series of gauge markers can also be used to determine the part of the thermometer being imaged and can be used as temperature indices.

The fluid length 14 is functionally related to the temperature of the bulb and this temperature-length function can be determined by calibrating the thermometer using standard temperature calibration procedures. Thus the temperature of the bulb can be determined from the x-ray reader output signal 42 by using the gauge length, the calibration length, the geometrical magnification factor, and the temperature-length function. A nomograph can be constructed so that when the x-ray detector is viewed directly by an observer, then the temperature of the bulb can be determined using the nomograph.

Various positioning techniques can be used to position an x-ray imager so that it intercepts the x-ray beam from through the fluid. When the position of a thermometer in the body is known relative to markers on the exterior of the body or to an external coordinate system, then this position and the position of the x-ray source can be used to position the x-ray imager. When the position of a thermometer is not known to sufficient accuracy in this way, then the x-ray imager can be positioned by first finding the position of the bulb image by using a large field x-ray imager and then moving a high resolution x-ray imager to this location. The large field imager can take various forms such as a pre-exposed x-ray film 81 located in front of the high resolution x-ray imager 41 so that when the high resolution x-ray imager is positioned behind the image of the bulb on the film, then the high resolution x-ray imager will intercept the x-ray beam from through the thermometer column 11. An x-ray imager can be moved close to the body to view a large field and locate a thermometer, or a portion of a thermometer, and can then be moved away from the body to provide a magnification factor to more accurately image the thermometer or thermometer portion. These positioning techniques can be used to move the x-ray imager to image only a part of the thermometer and to image each of several thermometers located in the body.

Image enhancement techniques can be used to increase the sensitivity of the imaging. Materials can be used in the x-ray detector which are especially sensitive to the energy of an x-radiation absorption edge of the fluid. The x-ray source and the fluid in the thermometer can be chosen so that there is a peak in the x-ray intensity at the energy of an x-radiation absorption edge of the fluid. A filter with an x-radiation absorption edge at an energy near an x-ray absorption edge of the fluid can be used to do this. Images made with and without this filter can be compared by the data processor in order to enhance the image of the fluid.

The x-radiation can be modulated by being alternatively passing through a first filter 26 having a first x-radiation absorption edge at an energy just below an x-radiation absorption edge of the fluid and a second filter 27 having a second x-radiation absorption edge at an energy just above the x-radiation absorption edge of the fluid. This can be done, for example, by rotating the filters 27 and 28 about a modulator axis 28 in front of the first x-ray source. Then, areas in a series of images which have maximum change in intensity from one image to the next image - which are the images of the column - can be compared to compensate for motion between images and can be contrast enhanced.

A no-filter component can be combined with the filters 27 and 28. Then image areas in a series of images which have the greatest change in contrast as the no filter component alternates with the other filters will be images of the markers. These images can also be compared to compensate for motions of the thermometer. Various other imaging enhancement techniques can also be used and various combinations of imaging enhancement techniques can be used.

Another form of an x-ray reader comprises the first x-ray source 21 and the first x-ray imager 41 paired with a second x-ray source 31 and a second x-ray imager 51 shown in FIG. 2. The second x-ray source 31 produces a second beam of x-radiation indicated by a vector 32 along the second beam left edge, a vector 33 along the second beam right edge, and a vector 34 along the central ray of the second beam. The central ray vector 34 crosses the column at a second angle 35 relative to the long axis 16 of the thermometer.

The preferred form of the second x-ray imager is also a high resolution imager, such as a microchannel plate detector, which feeds a transducer, such as a CCD video camera, producing a second imager output signal 52 which along with the output signal from the first x-ray imager 45 is input 61 to the data processor 62 which produces a reader output signal 63. The reader output signal is functionally related to the fluid length and thus functionally related to the temperature of the bulb. The reader output signal can indicate the temperature of the bulb in various ways for example by a graphic display of an image of the thermometer with temperature indices along the image of the column. For this x-ray reader the reader output signal 63 can also have various visual, audible, and even tactile components chosen to match the conditions of use. In this case the data processor can calculate the temperature from the first angle, the second angle, the magnification factor, and the temperature-length function. Again other x-radiation detectors can be used for the second x-ray imager, including detectors which produce a digital output directly. The reader output signal here can also have a component 64 which is a feed back signal for a control system (not shown) in order to control a process in the body.

The calibration techniques, the positioning techniques, and the image enhancement techniques described above can be used for this x-ray reader as well. A third filter 36, a fourth filter 37, and a second modulator axis 38 are shown in front of the second x-ray source. Filters and modulation rates used with the second x-ray source can be the same as filters used with the first x-ray source and alternatively can be different form filters and modulation rates used with the first x-ray source thus providing a large number if images to be data processed to enhance the sensitivity and reliability of the reader. An x-ray reader equivalent to the form with two sources and two imagers can be achieved using only the first x-ray source 21 and the first x-ray imager 31 by moving the first x-ray reader to a second position such as the position shown for the second x-ray source 41 and moving the first x-ray imager to a corresponding second position such as the position of the second x-ray imager. The calibration techniques, positioning techniques, and image enhancement techniques described above can also be used with this x-ray reader

More than one thermometer can be located in the body and read by the reader That is. along with the thermometer at least one sequent thermometer can be located in the body from where the sequent thermometer is not visible A sequent thermometer encloses a sequent thermometer column like 11 which is terminated at one end by a sequent thermometer bulb like 12 The sequent thermometer bulb and the sequent thermometer column contain a sequent thermometer fluid like 13 which expands along the sequent thermometer column to a sequent fluid length 14 which is a function of a sequent temperature of the sequent thermometer bulb The sequent thermometer fluid is also chosen to provide contrast for the reader A sequent thermometer can have the same sensitivity as the thermometer and can have different sensitivity from the thermometer A sequent thermometer can be sensitive over the same temperature range as the thermometer and can be sensitive over a different temperature range from the thermometer

Each of several thermometers can be distinguished from the others by its spatial position relative to the others Also each of several thermometers can be identified by a set of identifying markers To do this a sequent thermometer set of identifying markers, like the set 71 but in a pattern which is distinguished by a reader from the pattern of the set 71, is attached to a sequent thermometer

An alternative multi-component thermometer, not shown, has all the features of the thermometer 15 and also encloses at least one sequent bulb and sequent column containing a sequent fluid A sequent bulb being like 12, a sequent column being like 11, and a sequent fluid being like 13 and expanding along the sequent column to a fluid length like 14 functionally related to a sequent temperature of the sequent bulb When the multi-component thermometer is located in the body the reader can image the several fluid lengths and determine the several temperatures of the bulbs

A thermometer, including sequent thermometers and sequent components in the multi-component thermometer, can have a column with a varying diameter along the column (not shown) so that the sensitivity of the thermometer varies accordingly along the column Thus, this thermometer could have maximum sensitivity around a critical value of temperature and have less sensitivity at other temperatures This would allow a reduction in length of this thermometer relative to a thermometer with high sensitivity all along the column and would also ease the reading of the thermometer The example thermometer described above and the x-ray imagers described above are especially well adapted to the case where thermometers are implanted in living tissue Imaging enhancement techniques can increase the sensitivity of the imaging so that even smaller thermometers can be used The invention is also adapted to cases where thermometers are located in bodies which are not living tissue In these cases thermometers can be larger and readers using other wavelengths of electromagnetic radiation and acoustic imagers can be used

Several forms of a reader for thermometers which are located in a body from where the thermometers are not visible have been described using an x-ray source and an x-ray imager, moving this x-ray source and x-ray imager to get two subsequent images from which a data processor can calculate the temperature, and using two x-ray sources and two x-ray imagers to get two simultaneous images from which a data processor can calculate the temperature Also calibration techniques, positioning techniques, and image enhancement techniques which can be used with various readers for the thermometers have been described Parallel forms for a reader, with imagers using other wavelengths of electromagnetic radiation and using acoustic imagers to image the thermometer can be substituted in appropriate conditions, and parallel forms for the calibration techniques, positioning techniques, and image enhancement techniques can be used with these parallel forms for a reader.

Other equivalent forms for the thermometers, for readers which can image the thermometers to determine temperatures in the body, for calibration techniques for readers, for positioning techniques for readers, for image enhancement techniques for readers, and for using reader output signals as feed back signals for controlling a processes in the body will be obvious hereafter to persons skilled in the art. Therefore this invention is not limited to the particular examples shown and described here.

Claims

I claim:

1. A thermometer system comprising: a thermometer, the thermometer enclosing a column and a bulb, the column being terminated by the bulb at one end, the column and the bulb containing a fluid, the fluid expanding along the column to a fluid length which is functionally related to a temperature of the bulb, the thermometer being located in a body from where the thermometer is not visible; and a reader which images the fluid length in the column and produces a reader output signal which is functionally related to the fluid length in the column.

2. The device of claim 1 wherein the thermometer has a gauge marker located at a gauge length from the bulb, the bulb and the gauge marker being imaged by the reader to provide a calibration length measurement which is used with the gauge length to determine the temperature of the bulb.

3. The device of claim 1 further comprising a sequent thermometer, the sequent thermometer enclosing a sequent thermometer column and a sequent thermometer bulb, the sequent thermometer column being terminated at one end by the bulb, the sequent thermometer bulb and the sequent thermometer column containing a sequent thermometer fluid, the sequent thermometer fluid expanding along the sequent thermometer column to a sequent thermometer fluid length which is functionally related to a sequent temperature of the sequent thermometer bulb, the sequent thermometer being located in the body from where the sequent thermometer is not visible, and wherein the reader images the sequent thermometer fluid length in the sequent thermometer column and produces a sequent reader output signal which is functionally related to the sequent thermometer fluid length in the sequent thermometer column

4 The device of claim 3 wherein a set of identifying markers is attached to the thermometer and a sequent set of identifying markers is attached to the sequent thermometer, the set of identifying markers and the sequent set of identifying markers being imaged by the reader

5. The device of claim 1 wherein the reader output signal also has a component which is a feedback signal for a control system to control a process in the body

6. The device of claim 1 wherein the reader is an x-ray reader which images the fluid length in the column by imaging x-radiation from through the column

7 The device of claim 6 wherein the x-ray reader comprises- an x-ray source which sends an x-ray beam through the body and through the column, an x-ray imager, the x-ray imager being positioned to intercept the x-ray beam from through the body and through the column and produce the reader output signal

8 The device of claim 7 wherein the x-ray imager comprises a large field x-ray imager, the large field x-ray imager being positioned to intercept the x-ray beam from through the body and through the thermometer, a large field signal produced by the large field imager, the large field signal locating the bulb, and a narrow field x-ray imager, the narrow field x-ray imager being positioned with use of the large field signal to intercept the x-ray beam from through the column and produce the reader output signal 9 The device of claim 6 wherein the x-ray reader further comprises: an x-ray source which is located at a first source position and sends a first x-ray beam through the body and through the column, the first x-ray beam having a first central ray which makes a first angle relative to the fluid length , the x-ray source being moved to a second source location to send a second x-ray beam through the body and through the column, the second x-ray beam having a second central ray which makes a second angle relative to the fluid length; an x-ray imager, the x-ray imager being at a first imager position where it intercepts the first x-ray beam from through the body and through the column, the x-ray imager being moved to a second imager position to intercept the second x-ray beam from through the body and through the column; a first imager output signal which is functionally related to the fluid length and the first angle, the first imager output signal being produced by the first x- ray imager at the first imager position, a second imager output signal which is functionally related to the fluid length and the second angle, the second imager output signal being produced by the x-ray imager at the second imager position, and a data processor which receives the first imager output signal and the second imager output signal and produces the reader output signal 10 The device of claim 6 wherein the x-ray reader comprises a first x-ray source which sends a first x-ray beam through the body, and through the column, the first x-ray beam having a first central ray which makes a first angle relative to the fluid length, a first x-ray imager, the first x-ray imager being positioned to intercept the first x-ray beam from through the body and through the column, a first imager output signal which is functionally related to the fluid length and the first angle, the first imager output signal being produced by the first x- ray imager, a second x-ray source which sends a second x-ray beam through the body and through the column, the second x-ray beam having a second central ray which makes a second angle relative to the fluid length; a second x-ray imager, the second x-ray imager being positioned to intercept the second x-ray beam from through the body and through the column; a second imager output signal which is functionally related to the fluid length and the second angle, the second imager output signal being produced by the second x-ray imager; and a data processor which receives the first imager output signal and the second imager output signal and produces the reader output signal.

11. The device of claim 6 where the x-radiation has a peak intensity at an energy which matches an energy of an x-ray absoφtion edge of the fluid

12. The device of claim 11 wherein the x-radiation is modulated

13. The device of claim 6 wherein the x-radiation is modulated by alternatively passing through a first filter having a first x-radiation absoφtion edge and a second filter having a second x-radiation absoφtion edge.

14 The device of claim 6 wherein the x-radiation is modulated by alternatively passing through no filter, a first filter having a first x-radiation absoφtion edge, and a second filter having a second x-radiation absoφtion edge 15 The device of claim 1 wherein the reader is an acoustic imager

16. The device of claim 1 wherein the thermometer encloses a sequent column and a sequent bulb, the sequent column being terminated by the sequent bulb at one end, the sequent bulb and the sequent column containing a sequent fluid, the sequent fluid expanding along the sequent column to a sequent fluid length which is functionally related to a sequent temperature of the sequent bulb.

17. The device of claim 1 wherein the column has a varying diameter along the column.