Abstract:
Expanding fluid thermometers are implanted in a body—for example in and adjacent to a cancerous tumor—and are read by x-ray imaging.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of U.S. patent application Ser. No. 09/218,792 filed Dec. 21, 1998, now abandoned, which claims benefit of U.S. Provisional Application No. 60/070,399 filed Jan. 5, 1998. 
    
    
     DETAILED DESCRIPTION 
     The invention—especially useful in cancer therapy—comprises implanted thermometers having a fluid moving from a bulb along a channel to a fluid length, the fluid length—thus the temperature of the bulb—being determined by x-ray imaging. 
     The invention provides progress over prior art as shown for example in U.S. Pat. Nos. 1,199,121 by Siebert, 3,548,308 by Seabury, 3,893,111 by Cotter, 4,138,998 by Nowogrodzki, 4,561,054 by Andrews, 4,613,757 by Deserno, 4,947,247 by Farver, 5,109,853 by Taicher, 5,983,123 by Shmulewitz, and in Japanese patent documents 58-17326 by Konishi and 58-169040 by Nakada. 
    
    
     FIG. 1 shows a thermometer cross section. 
     FIG. 2 shows a thermometer in a body imaged by x-radiation. 
     FIG. 3 shows a second thermometer cross section. 
     FIG. 4 shows two thermometers connected. 
     FIG. 5 shows a thermometer with two fluid components. 
    
    
     The product comprises an imager  41  which images x-radiation, a source  21  which provides an x-radiation beam which overlaps the imager, and a plurality of thermometers implanted in a body  91  from where they can not be imaged by visible light. 
     Any first thermometer  15  from the plurality of thermometers comprises a first channel  11  and a first bulb  12  terminating the first channel. The first channel and the first bulb enclose a first fluid  13  . The first fluid moves along the first channel to a first fluid length  14  which is functionally related to a first bulb temperature. 
     A first fluid image length of the first fluid length is projected outside the body by the beam and is imaged by the imager. 
     Fixed first markers  71  are fixed relative to the first channel. A first markers image is projected outside the body by the beam and imaged by the imager. The first markers provide a first calibration length. A first calibration image length of the first calibration length is projected outside the body by the beam and imaged by the imager. A first ratio of the first fluid image length to the first calibration image length is functionally related to the first bulb temperature. 
     Any second thermometer  15 A from the plurality of thermometers comprises a second channel  11 A and a second bulb  12 A terminating the second channel. The second channel and the second bulb enclose a second fluid  13 A . The second fluid moves along the second channel to a second fluid length  14 A which is functionally related to a second bulb temperature. 
     The second thermometer has fixed second markers  71 A fixed relative to the second channel. A second markers image projected outside the body by the beam and imaged by the imager is distinct from the first markers image independently of the relative positions and orientations of the first thermometer and the second thermometer. 
     The second markers provide a second calibration length. A second calibration image length of the second calibration length is projected outside the body by the beam and imaged by the imager. A second ratio of the second fluid image length to the second calibration image length is functionally related to the second bulb temperature. 
     Markers can take various forms—such as imbedded grains and bands encircling the channel—other than the protrusions depicted. For any thermometer from the plurality of thermometers at least some markers can be provided by bulb dimensions and shapes. 
     The imager can comprise a first imager component  41  and a second imager component  51 . Here the source comprises a first source component  21  and a second source component  31 . The first source component provides a first beam component—bounded by vectors  22  and  23 —which overlaps the first imager component. The second source component provides a second beam component—bounded by vectors  32 ,  33 —which overlaps the second imager component. 
     A first central ray  24  of the first beam component makes a non-zero angle  25  with the long axis  16  of the first thermometer. A second central ray  34  of the second beam component makes a non-zero angle  35  with the long axis. The first central ray of the first beam component makes a non-zero angle  123  with a second central ray of the second beam component. 
     Here the fluid image length comprises a first fluid image length component imaged by the first imager component, paired with a second fluid image length component imaged by the second imager component. The calibration image length comprises a first calibration image length component imaged by the first imager component paired with a second calibration image length component, imaged by the second imager component. The paired image components can be used to determine the location and orientation of a thermometer relative to three orthogonal space coordinates. 
     Paired source, beam, imager, and image components can be obtained using only the first source  21  and the first imager  41  as shown to obtain first members of paired image components and then moving the first source to a second position, such as the position shown for the second source  31 , and moving the first imager to a corresponding second position such as the position of the second imager  51  to obtain second members of the paired image components. 
     The imager can comprise a large field imager  81 , a large field image of the first bulb imaged by the large field imager, and a narrow field x-ray imager  41 . The narrow field x-ray imager is positioned with use of the large field image to image the first fluid length. 
     A first thermometer from the plurality of thermometers— 15 C in FIG.  4 —can be connected to a second thermometer from the plurality of thermometers  15 D end-to-end with the second bulb distal the first bulb. A string of many thermometers from the plurality can be connected end-to-end. 
     A thermometer— 15 M—in FIG.  5 —can have a first fluid component  12 M and a second fluid component  12 N, with the second fluid component moving the first fluid component along the channel  11 M and with the first component providing higher x-radiation attenuation than the second component. 
     The x-radiation can have a peak intensity at an energy which matches an x-radiation absorption edge energy of the fluid. Materials can be used in the imager which are especially sensitive to the energy of an x-radiation absorption edge of the fluid The source and the fluid can be chosen so that there is a peak in the x-ray intensity at an x-radiation absorption edge of the fluid. A filter with an x-radiation absorption edge near an x-ray absorption edge of the fluid can be used, and images made with and without this filter can be compared to enhance the image of the fluid. The x-radiation can be modulated. 
     The x-radiation can be modulated by alternately passing through a first filter  26 ,  36  having a first x-radiation absorption edge just below an x-radiation absorption edge of the fluid and a second filter  27 ,  37  having a second x-radiation absorption edge just above the x-radiation absorption edge of the fluid. This can be done, for example, by rotating the filters  26 ,  36  and  27 ,  37  about a modulator axis  28 ,  38  in front of the source. Then, areas in a series of images which have maximum change in intensity from one image to the next image are images of a fluid length which can be compared to compensate for motion between images and can be contrast enhanced. 
     Filters and modulation rates used with the second source can be the same as filters used with the first source and alternatively can be different from filters and modulation rates used with the first source thus providing a large number of images to be data processed to enhance the sensitivity and reliability of the reader. A no-filter component can be added to the first beam modulation, to the second beam modulation, and to both. 
     Dimensions of an example thermometer which can be implanted in a living body by biopsy techniques, are: length of thermometer 20 mm; channel 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 channel at about 1 mm per degree Celsius. Thus, for example, if an accuracy of 0.3 Celsius degrees is required, then the fluid length must be measured to an accuracy of 0.3 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. 
     The preferred form of the imager is a high resolution imager, such as a microchannel plate detector, which feeds a transducer, such as a CCD video camera, which produces an imager output signal  42 ,  52  which is input  61  to a data processor  62  which then produces an output signal  63 . 
     The output signal can indicate the temperature of the bulb using various visual, audible, and tactile means. The output signal can also have a component  64  which controls a process in the body. 
     The output, of a microchannel imager for example, can be viewed directly, in which case this is the output signal. Other x-radiation detectors can be used including detectors which produce a digital output directly. 
     Any first thermometer from the plurality of thermometers has a first thermal calibration which relates the first fluid length to the first temperature of the first bulb and has a first calibration length provided by the first markers. Any second thermometer from the plurality of thermometers has a second thermal calibration which relates the second fluid length to the second temperature of the second bulb and has a second calibration length provided by the second markers. 
     Because the first markers image is distinct from the second markers image independently of positions and orientations of thermometers in the beam, the first thermal calibration and the first calibration length can be associated with the first fluid image length and first calibration image length and the second thermal calibration and the second calibration length can be associated with the second fluid image length and second calibration image length. 
     The position of the first thermometer along the beam can be determined from paired image components and by comparing the first bulb diameter with the first bulb image diameter. The orientation of the first thermometer relative to the beam can be determined from paired image components and by comparing the first calibration length with the first calibration image length. 
     Geometric factors—the distance from the source to the imager, and the position and orientation of the first thermometer along the beam—are then used to determine the fluid length from the fluid image length. From this the first thermal calibration is used to determine the temperature of the bulb. 
     A thermometer can have a channel with a varying diameter along the channel so that the sensitivity of the thermometer varies accordingly along the channel to have maximum sensitivity around a critical temperature. 
     While the specific examples of thermometer, source, and imager described above are especially well adapted for thermometers implanted in living tissue, these and other examples consistent with the principles of the invention can be used in various bodies. Parallel imaging arrangements using other wavelengths of electromagnetic radiation and using acoustic radiation can be substituted in appropriate conditions. Parallel forms for the calibration techniques, positioning techniques, and image enhancement techniques can be used with these parallel imaging arrangements.