THERMOGRAPHIC APPARATUS

Abstract: Thermographic apparatus intended in particular for diagnosing disturbances in circulation in the extremities of a patient, by recording the temperature distribution along a selected line extending from the ankle of a patient up to the thigh on both legs of the patient, whereafter any asymmetry in the two registered temperature profiles is used for the basis of a diagnosis. The apparatus comprises a temperature transducer (4), preferably an IR-detector, which is carried on one end of an extendable and retractable arm (6), so that the transducer can be moved manually along a selected line on the leg (2) of the patient. Coupled to the arm (6) is a position transducer (11) for generating an electric signal representative of the distance moved by the temperature transducer. The apparatus also includes a recorder (10) to which both the temperature signal and the position signal are transmitted and which is arranged to record the measured temperature profile simultaneously. This sequence can be repeated on the other leg of the patient, so that the recorder records both temperature profiles. The apparatus also includes a signal-processing unit (14a, 14b) in which the analogue temperature signals and position signals are converted to digital form and stored so that they can later be processed in a calculator part (14c) which calculates the difference between the temperatures in mutually corresponding locations on the two legs of the patient, whereby a temperature difference-position-relationship is obtained, which after being converted to analogue form can be transmitted to the recorder (10) and recorded thereby.

Description: THERMOGRAPHIC APPARATUS The present invention relates to apparatus for use in medical thermography for diagnostic purposes, i.e. for determining and registering the temperature of the sur¬ face of the skin of a patient, and in particular for detecting disturbances in the circulation in the limbs of a patient, such as the occurrence of deep venous thrombosis or arterial embolisms. It is well known that disturbances in the blood circulation in limbs causes the temperature of the skin to deviate from normal values. This fact has been utilized in diagnosing the aforementioned disorders in circulation, IR-scanning cameras being used to this end. Such cameras, however, are expensive and are relatively complicated in use, and hence a more comprehensive use of IR-scanning cameras for detecting and diagnosing disturbances in circulation by thermography is hardly conceivable. The object of the present invention is therefore to provide an apparatus for thermographic diagnosis which is simpler, less expensive and more easily used than those apparatus used hitherto, and which is especially suited for the aforedescribed purpose. The main characterizing features of the apparatus according to the invention are disclosed in the accompany¬ ing claim 1. Further developments and emobodiments of the apparatus according to the invention have the characteriz¬ ing features disclosed in claims 2-7. The invention is based on a novel method of detecting and diagnosing disturbances in the circulation in a patient's leg, by measuring the temperature of the skin OMPI ^ along a suitable line on each of the two legs of the patient and then comparing the two temperature curves th obtained, any deviations or asymmetri between the two temperature curves indicating the presence of irregulari ties in the circulation in one or the other of said legs Tests carried out in patients have shown that this therm graphic method provides for the reliable diagnosis of th - aforedescribed kind of disturbances in blood circulation The ther ographic apparatus according to the inven- tion is primarily constructed and intended for making thermographic examinations of the aforedesc-ribed kind, although it can also be used for other thermographic exa minations, as will be made clear hereinafter. An exemplary embodiment of the invention will now b described with reference to the accompanying drawings, i which Figure 1 is a schematic illustration in perspective of an apparatus according to the invention, while being used to thermographically examine the leg of a patient; Figure 2 is a diagram illustrating by way of exampl temperature curves of the kind which can be obtained by means of an apparatus according ~ "to -the invention when carrying out a thermographic examination of the afore- described kind; and Figure 3 is a simplified block diagram of the con- struciton of the signal-processing part of an apparatus according to the invention. Figure 1 illustrates schematically a thermographic apparatus according to the invention, generally referenc 1, said apparatus in the illustrated embodiment compris¬ ing a roller table mounted on lockable rollers or wheels The apparatus is illustrated in conjunction with examini the legs of a patient thermographically, in order to detect any irregularities of the circulation in the legs For the sake of simplicity, only the left leg 2 of the patient is shown, said patient lying on an examination bed 3 or the like. OMPI Λ. WIPO The apparatus according to the invention also includes a temperature transducer or sensor 4 of suitable kind arranged to sense the temperature of a closely adjacent surface, such as the surface of the skin of a part of a body, and to produce a corresponding electrical. output signal. The temperature transducer 4 may, to advantage, be an infrared detector which when sensing the temperature of the surface of said skin need not be in direct contact therewith, but measures the temperature by detecting heat radiation transmitted from the surface of said skin within a given area. Infrared detectors which have variable focusing are known to the art, so that it is possible to vary the size of the area from which heat radiation is received and in which the temperature is thus measured. The temperature transducer 4 is, in the illustrated embodi¬ ment, suitably provided with a distance finger 5 or the like which may be held in contact with the surface of the skin during a temperature-measuring operation, such that the distance between said skin surface and the radiation detector in the temperature transducer 4 is hereby set to the correct value and remains constant . The temperature transducer 4 is carried on one end of a knuckle arm 6 , the other end of which is pivotally mounted on a holder 7, which is adjustable on a post 8 arranged on the table 1. The knuckle arm 6 is so arranged that the temperature transducer 4 can be moved along a desired line on the leg 2 of the patient, during which movement the transducer 4 delivers an electric temperature signal representative of the temperature of the skin along said line. Connected to the knuckle arm 6 is an electric position transducer (not illustrated), such as a linear potentiometer, said position transducer being connected in a manner to produce an electric output signal representa¬ tive of the linear distance betwee_n__the temperature trans- ducer 4 and the opposite end 7 of said knuckle arm. Thus, this signal represents the extent to which the arm 6 has been extended, and therewith the relevant position of the temperature transducer 4 during its movement along the OMPI « Λ O w c conver s e ana ogue s gna s rece ve o correspon ¬ ing digital signals; a memory store 14b for storing the digital signals; a processor or calculator 14c in which the signal data stored in the memory can be processed and subjected to mathematical calculations; and a D/A-unit 14d for converting the quantities calculated in the processor ' unit 14c to analogue signals which can be supplied to the recorder 10 for presentation. The aforedescribed thermographic appratus for thermo- graphically examining the leg of a patient to ascertain whether there are irregularities in circulation, is used in the following manner: The table 1 is positioned at the foot of the bed 3, on which the patient is placed in a substantially horizon- tal position, and the carriage 9 is positioned so that the post 8 , and therewith the arm 6 and the temperature transducer 4, are located substantially opposite the line on one leg of the patient, along which the temperature of the skin is to be measured. The carriage 9 is locked in this position and the holder 7 is adjusted to a suitable height on the post 8. The temperature transducer 4 is positioned in a given location e.g. on the patient's ankle and is ' then moved manually along said line up the patient's leg to the upper regions of the thigh, while simultaneously depressing a suitable switch on the tempe¬ rature transducer 4 so that the temperature signal T generated by the temperature transducer is passed to the apparatus table 1.- At the same time, the position trans¬ ducer 11 connected to the arm 6 generates an electric posi- tion signal X, which represents the distance through which the temperature transducer 4 has been moved along the leg. The temperature signal T generated by the temperature trans¬ ducer 4, and the position signal X generated by the posi¬ tion transducer 11 are passed, through the switching element 13, to the recorder 10, which records the corre¬ sponding analogue temperature-position curve, e.g. the curve A in the diagram shown in Figure 2. The analogue signals from said temperature transducer 4 and the posi- tion transducer 11 are also transmitted, through the switching element 13, to the signal-processing unit 14, in which the analogue signals are converted to digital signals in the D/A converter 14a, and the resultant digi tal signals are stored in the memory store 14b. The carriage 9 is then moved on the table 1 to a position such that the arm 6 with the temperature trans¬ ducer 4 is located opposite the corresponding sensing li on the other-- leg of the patient, whereafter a similar temperature-registering operation is carried out along said other leg. As a result hereof there is obtained a further temperature curve, such as the temperature curve referenced B in Figure 2. The temperature signal from th transducer 4 and the position signal from the transducer 11 are also transmitted, through the switching unit 13, to the signal-processing unit 14, where the signals are converted to digital form and stored in the store 14b. Thus, subsequent to measuring the skin temperature of the patient's legs in the aforedescribed manner, the two temperature profiles are stored in digital form in t memory store 14b of the apparatus . The processing unit 1 of the apparatus can now be initiated, to process said store data in a manner such that the temperature diffe¬ rence between corresponding locations on the two legs of the patient are determined as a function of position, i. the distance from the starting point at the ankles of the patient. This calculated temperature difference - position - relationship is converted in the D/A- convert 14d to corresponding analogue signals, which can be tran mitted to the recorder 10, which then draws the curve € illustrated in the diagram in Figure 2, said curve C ind cating the temperature difference between the two legs of the patient as a function of the distance from the starting point, e.g. the ankles of the patient. On the basis of this temperature-difference curve it is possibl to assess the occurrence and the position of any circula tory disturbances in the leg of the patient, e.g. distur bances in the form av venous thrombosis. OMPI &u the apparatus according to the invention, no signal was used from the position transducer 12 , which senses the position of the carriage 9 , This position transducer 12 can be used, however, when it is desired to study the temperature distribution over a surface area, over a burn or leg ulcer for example. I ' this case, the temperature transducer 4 is moved by means of the arm 6 over the area of the skin in question, along a plurality of substantially mutually parallel spaced apart lines, the carriage 9 between each such linear scan being moved a distance which corresponds substantially to the distance between two adjacent scan lines. The signals obtained from the temperature transducer 4 and the two position trans- ducers 11 and 12 are transmitted, through the switching unit 13, to a module 15 for analogue xyz-presentation, by means of which the recorder 10 is caused to simultaneously draw a family of curves which includes a temperature pro¬ file curve for each scan line, in a manner such as to obtain a "temperature topography" of the area scanned. Depending upon the capacity of the memory store and the design of the processor in the signal-processing unit 14, greater or lesser parts of the measuring data obtained when making such a scan of said surface can, of course, be stored and processed in a suitable, desired manner, e.g. for digital write-out or presentation by means of the recorder 10. A device according to the invention may also be pro¬ vided, to advantage, with a timer 16, which can be actuated to send to the switching means 13 an output signal repre¬ sentative of the time which has lapsed. In this way it is possible, by means of the apparatus according to the in¬ vention, to also register a temperature variation which is dependent on time, said temperature transducer 4 being held stationary at a given location on the area of the body whose temperature is to be studied as a function of time, and the temperature-time-sequence can be presented sim ltaneously in curve-form by means of the recorder 10 and also converted to digital form and stored in the un 14 for further processing or evaluation. The registrati of temperature as a function' of time may be of interest various provocation tests, e.g. cold-provocation when studying the circulation of hands and feet, and the in¬ fluence on the circulation of different forms of nerve blockers. By suitably designing the memory capacity and calc lation routines of the signal-processing unit 14, an apparatus according to the invention can be constructed so as to enable it to be also used for other kinds of e minations than thermographic examinations, such as in p ticular occlusion plethysmography, which is a diagnosti method for deep venous thrombosis and which can be appli together with and complementary to the thermographic method described above. For the purpose of carrying out such occlusion plethysmographic operations, the apparat according to the invention may be provided with two volume- or pressure sensors, which are applied at suita locations on the extremity in question and the output signals of which are transmitted, through the switching means 13, to the signal-processing unit 14, together wi a time signal from the timer 16, wherewith the processo 14c can be designed to calculate on the basis of this d such magnitudes as initial flow, the venous reserve vol and the emptying rate. Although the -illustrated and described embodiment the apparatus according to the invention has only one temperature transducer with associated position transdu it will be understood that said apparatus is not limite hereto, but may be provided with two or more temperatu transducers with associated position transducers, so th a plurality of temperatures profiles can be registered simultaneously. The illustrated and described exemplary embodiment of the apparatus can also be modified in other respects within the scope of the invention. Thus, the knuckle ar can be replaced with another suitable kind of extendabl and retractable arm for carrying the temperature trans¬ ducer 4, such as a telescopic arm. Also other devices for determining the position ' of the temperature transducer and for generating a corresponding signal may be used, of course. Thus, the temperature transducer may e.g. be freely movable held only in the hand of the operator and connected to the end of a line or wire which can be pulled out from a winding device in the apparatus table, the position transducer consisting e.g. of a suitable revolution counter coupled to the winding device. The temperature transducer could also be completely free and its momentary position be determined optically or by means responsive to the movement of the transducer relative to the skin sur¬ face. p •- -- C ,1.1

Claims: CLAIMS : 1. An apparatus for determining and registering the tem¬ perature of the surface of a part of the body of a patien particularly for detecting disturbances in circulation in the extremities of the patient, comprising at least one temperature transducer movable over the surface of the bo and capable of sensing the temperature of the momentarily adjacent portion of the body surface and generating an electric signal (I) corresponding thereto and recording means (10) to which said temperature signal can be applie characterized by means (11) responsive to the. movements the temperature transducer (4) for generating an electric signal (x) representing the position of the temperature transducer along its path of movement, said recording mea (10) being supplied also with said position signal (x) an capable of recording the temperature being sensed as a function of the position of the temperature transducer, a signal processing means (14) supplied with said temperatu and position signals and including storage (14b) for stori associated values of the temperature and positions signals from at least two, different, measured temperature- position-relations and means (14c) for comparing the temp rature values as function of the positions for said two temperature-position-relations stored in said storage mea (14b) and for producing signals representing the temperat difference as function of the position for said two tempe rature-position-relations, the last mentioned signals bei supplied to said recording means (10) for the recording o said on position dependent temperature difference. 2. An apparatus according to claim 1, characterized in that it comprises an extendable and retractable arm (6) supported at one end from a frame structure (1) and carryi at its other end said temperature transducer (4) in a man such that the transducer can be moved linearly over the body surface by extending or retracting said arm, and tha said signal generating means responsive to the movements - -- - - C'ΛΕi !&?- of the temperature transducer comprise a position trans¬ ducer (11) coupled to said arm for generating an electric signal (X) representing the linear, distance between the two said ends of the arm. 3. An apparatus according to claim 1 or 2 , characterized in that said signal-processing means (14) include means (14a) for converting the analogue temperature signals and position signals from the temperature and position trans¬ ducers (4, 11) to corresponding digital signals; storage means (14b) for storing said digital signals for.at least two, differing, measured temperature-position-relations; a calculating means (14c) for calculating on the basis of the data stored in said storage means concerning two tem¬ perature-position-relations, the difference in temperature as a function of position and generating corresponding digital signals; and means (14d) for converting the digital signals generated by said calculating means to corresponding analogue signals , which can be supplied to said recording means (10) for recording the calculated temperature difference as a function of position. 4. An apparatus according to claim 2, characterized in that the first said end (7) of the extendable and retract¬ able arm (6) is carried by a carriage (9), which is arranged for movement on the frame structure (1) in a direction substantially perpendicular to the direction in which the arm is extendable and provided with means for locking the carriage in a selectable position, second position transducer (12) being coupled to said carriage for generating a second electric position signal representative of the position of the carriage in its direction of dis-- placement, said second position signal also being supplied to the recording means (10) , which is designed to be capable of recording the sensed temperature as a function of both the extent to which the arm (6) is extended and the position of said carriage (9). 5. An apparatus according to claim 2 or 4, characterize in that said first end of the arm (6) can be adjusted ver tically along a substantially vertical post (8) mounted o the frame structure (1) . 6. An apparatus according to any one of claims 2, 4 and 5, characterized in that said first end (7) of the arm (6 is displaceable on the frame structure (1) in the directi in which the arm (6) is extendable. 7. An apparatus according to any one of claims 1 % to 6 , characterized in that it includes a timer (16) for gene¬ rating an analogue electric time signal, which can be supplied to said recording means (10) instead of said position signal, so that the said recording means can record the measured temperature as a function of time.

Inventors: NILSSON E, ZETTERQUIST S
Applicants: NILSSON E, ZETTERQUIST S
Application year: 1980
Main classification: G01K1
IPC codes: A61B5, G01D9, G01K1