WO2014049521A1

WO2014049521A1 - Temperature controlled calibration for optical shape sensing

Info

Publication number: WO2014049521A1
Application number: PCT/IB2013/058812
Authority: WO
Inventors: Bharat RAMACHANDRAN; David Paul Noonan; Molly Lara FLEXMAN
Original assignee: Koninklijke Philips N.V.
Priority date: 2012-09-28
Filing date: 2013-09-24
Publication date: 2014-04-03

Abstract

A calibration system for optical fiber shape sensing includes a temperature control fixture (140) including a plurality of segments(142), each segment being independently temperature controlled using one or more temperature control devices(144). A processor (114) and memory (116) coupled to the processor are included. An optical shape sensing module (115) is configured to interrogate and receive feedback from an optical shape sensing (OSS) instrument (104) wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions such that the OSS data is employed as calibration data for use during operation of the OSS instrument to reduce instability and jitter.

Description

TEMPERATURE CONTROLLED CALIBRATION

FOR OPTICAL SHAPE SENSING

BACKGROUND:

Technical Field

This disclosure relates to medical instruments and more particularly to shape optical fibers with temperature controlled calibration for medical applications. Description of the Related Art

Shape sensing based on fiber optics exploits the inherent backscatter in a conventional optical fiber. The principle involved makes use of distributed strain measurement in the optical fiber using characteristic Rayleigh backscatter patterns. The physical length and index of refraction of a fiber are intrinsically sensitive to environmental parameters, temperature and strain and, to a much lesser extent, pressure, humidity, electromagnetic fields, chemical exposure, etc. The wavelength shift, Δλ or frequency shift, Δν, of the backscatter pattern due to a temperature change, ΔΤ, or strain along the fiber axis, ε, is:

Δλ/ λ = -Δν /ν = K_T AT + Κ_εε , where ^{1 ^} The temperature coefficient K_T is a sum of the thermal expansion coefficient a and the thermo- optic coefficient ξ , with typical values of 0.55x10-6 °C^_1 and 6.1x10-6 °C^_1, respectively, for Germania-doped silica core fibers. The strain coefficient Κε is a function of group index n; the components of the strain-optic tensor, pij and Poisson's ratio, μ. Typical values given for n, pi2, pii and μ for germanium-doped silica yield a value for Κε of 0.787. Thus, a shift in temperature or strain is merely a linear scaling (for moderate temperature and strain ranges) of the spectral frequency shift, Δν. Naturally, this simple linear model would not apply if strains approaching the elastic limit of the fiber, or temperatures approaching the glass transition temperature of the fiber were encountered.

With a four or more core fiber system where one core is located in the center of the cross-section, strain due to bending and temperature effects can be separated out if no axial strain (tension) is applied, or if the tension is known and controllable (or can be calibrated out). Combined shape and temperature sensing is feasible. However, when calibration is performed at certain temperatures and the OSS tethers used at different temperatures, higher order effects result in increases in error and jitter. For this reason, calibration at temperatures in which the device will be used is desirable.

SUMMARY

In accordance with the present principles, a calibration system for optical fiber shape sensing includes a temperature control fixture including a plurality of segments; each segment being independently temperature controlled using one or more temperature control devices. A processor and memory coupled to the processor are included. An optical shape sensing module is configured to interrogate and receive feedback from an optical shape sensing (OSS) instrument wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions such that the OSS data is employed as calibration data for use during operation of the OSS instrument to reduce instability and jitter.

A system for temperature compensating an optical fiber shape sensing instrument includes a processor and a memory coupled to the processor. An optical shape sensing module is stored in memory and configured to interrogate and receive feedback from an optical shape sensing (OSS) instrument wherein OSS data is collected by deploying the OSS instrument to gather OSS data when a length of the OSS instrument is under a plurality of different temperature conditions. A data structure is stored in memory and is configured to correlate temperature conditions with calibration data such that best fit calibration data is employed to adjust the OSS data to improve accuracy and reduce instability and jitter.

A method for calibrating an optical fiber shape sensing device includes controlling a temperature for a plurality of segments of a temperature control fixture, each segment being independently temperature controlled using one or more temperature control devices;

collecting optical shape sensing (OSS) data from an OSS instrument wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions; and employing the OSS data as calibration data for use during an operation to adjust measured OSS data in accordance with the calibration data to reduce instability and jitter.

These and other objects, features and advantages of the present disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

This disclosure will present in detail the following description of preferred

embodiments with reference to the following figures wherein:

FIG. 1 is a block/flow diagram showing a shape sensing calibration system for temperature calibration in accordance with one embodiment;

FIG. 2 is a diagram showing a shape sensing calibration system with geometric orientation and tensioning mechanisms for decoupling temperature effects from axial strains in accordance with one embodiment;

FIG. 3 is a block/flow diagram showing a shape sensing system configured to provide temperature calibration during a procedure in accordance with another embodiment; FIG. 4 is a diagram showing different temperature regimes of a shape sensing system relative to a patient in accordance with the present principles;

FIG. 5 is a diagram showing a launch fixture with a temperature reference in accordance with one embodiment;

FIG. 6 is a diagram showing a shape sensing system with temperature control for regulating temperature during use in accordance with one embodiment; and

FIG. 7 is a flow diagram showing a method for shape sensing calibration of an optical shape sensing instrument in accordance with an illustrative embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

In accordance with the present principles, a system and method for calibration, in a temperature controlled manner, of an optical shape sensing (OSS) fiber or an OSS-enabled device are provided. In some embodiments, all of the OSS tether may be calibrated at different temperatures, parts of the OSS tether may be at different temperatures, a transition zone between two or more temperature zones may be sharp or gradual and a length of sections at different temperatures can be varied dynamically and/or be adjustable.

Heat may be provided or removed using conduction, convection or radiation.

Examples of heat transfer fixtures may include a straight fixture path on a metal plate that is heated (conduction), a spiral fixture through which a fluid (with known heat capacity) at known temperature is circulated (convection), a chamber where warm gas is used to maintain temperature around 37 degrees C (for example), while a launch section is kept at room temperature of 22 degrees C (for example) using an electric heating mat and a distal tip is sprayed with freon (very low temperature) to mimic cryoablation, etc. Calibration of OSS tethers or OSS-enabled instruments may be performed using similar fixtures or systems in a temperature controlled manner. In another embodiment, the OSS calibration is performed in a temperature controlled manner post-integration into an interventional device. The interventional device may be placed in proper shapes (spiral, straight, typical and so on) and be activated upon reaching the proper temperature. An example of this may include a catheter that can change its stiffness properties at 37 degrees C (due to its Nitinol structure activating at that temperature). In another embodiment, multiple sets of calibration are performed pre- and post-integration for varying segment lengths at different temperatures, effectively creating a look-up table of calibration data. These values are updated in real-time during a procedure so as to produce optimal performance of the interventional device.

Increased or reduced temperature of OSS devices often results in greater errors and jitter. Therefore, temperature controlled calibration is employed to reduce these and improve the performance of OSS devices. Often calibration of OSS devices is performed at a single temperature. However, during use, the OSS tether or OSS enabled device experiences at least two temperatures, e.g., room temperature at the proximal portion and body temperature at the distal portion. There is also the possibility of localized temperature changes, e.g., at a distal tip of the OSS device due to a procedure, such as ablation. Calibration of the tether or device for operation at two or more different temperatures will improve accuracy and stability, while reducing standard deviation.

It should be understood that the present invention will be described in terms of medical instruments; however, the teachings of the present invention are much broader and are applicable to any fiber optic instruments and calibration devices thereof. In some

embodiments, the present principles are employed in tracking or analyzing complex biological or mechanical systems. In particular, the present principles are applicable to internal tracking procedures of biological systems, procedures in all areas of the body such as the lungs, gastro- intestinal tract, excretory organs, blood vessels, etc. The elements depicted in the FIGS, may be implemented in various combinations of hardware and software and provide functions which may be combined in a single element or multiple elements.

The functions of the various elements shown in the FIGS, can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions can be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which can be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and can implicitly include, without limitation, digital signal processor ("DSP") hardware, read-only memory ("ROM") for storing software, random access memory

("RAM"), non-volatile storage, etc.

Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure). Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative system components and/or circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams and the like represent various processes which may be substantially represented in computer readable storage media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Furthermore, embodiments of the present invention can take the form of a computer program product accessible from a computer-usable or computer-readable storage medium providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, a computer-usable or computer readable storage medium can be any apparatus that may include, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The medium can be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. Examples of a computer-readable medium include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk and an optical disk. Current examples of optical disks include compact disk - read only memory (CD-ROM), compact disk - read/write (CD-R/W), Blu-Ray™ and DVD.

Referring now to the drawings in which like numerals represent the same or similar elements and initially to FIG. 1, a system 100 for temperature controlled calibration of shape sensing enabled devices is illustratively shown in accordance with one embodiment. System 100 may include a workstation or console 112 from which a procedure is supervised and/or managed. Workstation 112 preferably includes one or more processors 114 and memory 116 for storing programs and applications. Memory 116 may store an optical sensing module 115 configured to interpret optical feedback signals from a shape sensing device or system 104. Optical sensing module 115 is configured to use the optical signal feedback (and any other feedback, e.g., electromagnetic (EM) tracking) to reconstruct deformations, deflections and other changes associated with a medical device or instrument 102 and/or its surrounding region. The medical device 102 may include a catheter, a guidewire, a probe, an endoscope, a robot, an electrode, a filter device, a balloon device, or other medical component, etc.

The shape sensing system 104 on device 102 includes one or more optical fibers 122 which are coupled to the device 102 in a set pattern or patterns. The optical fibers 122 connect to the workstation 112 through cabling 127. The cabling 127 may include fiber optics, electrical connections, other instrumentation, etc., as needed.

Shape sensing system 104 with fiber optics may be based on fiber optic Bragg grating sensors. A fiber optic Bragg grating (FBG) is a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by adding a periodic variation of the refractive index in the fiber core, which generates a wavelength-specific dielectric mirror. A fiber Bragg grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector.

A fundamental principle behind the operation of a fiber Bragg grating is Fresnel reflection at each of the interfaces where the refractive index is changing. For some wavelengths, the reflected light of the various periods is in phase so that constructive interference exists for reflection and, consequently, destructive interference for transmission.

The Bragg wavelength is sensitive to strain as well as to temperature. This means that Bragg gratings can be used as sensing elements in fiber optical sensors. In an FBG sensor, the measurand (e.g., strain) causes a shift in the Bragg wavelength.

One advantage of this technique is that various sensor elements can be distributed over the length of a fiber. Incorporating three or more cores with various sensors (gauges) along the length of a fiber that is embedded in a structure permits a three dimensional form of such a structure to be precisely determined, typically with better than 1 mm accuracy. Along the length of the fiber, at various positions, a multitude of FBG sensors can be located (e.g., 3 or more fiber sensing cores). From the strain measurement of each FBG, the curvature of the structure can be inferred at that position. From the multitude of measured positions, the total three-dimensional form is determined.

As an alternative to fiber-optic Bragg gratings, the inherent backscatter in

conventional optical fiber can be exploited. One such approach is to use Rayleigh scatter in standard single-mode communications fiber. Rayleigh scatter occurs as a result of random fluctuations of the index of refraction in the fiber core. These random fluctuations can be modeled as a Bragg grating with a random variation of amplitude and phase along the grating length. By using this effect in three or more cores running within a single length of multi-core fiber, the 3D shape and dynamics of the surface of interest can be followed.

In one embodiment, calibration of OSS tethers or OSS enabled instruments 102 in a temperature controlled way includes altering portions of the instrument 102 to be at different temperatures in a controlled way. For example, a proximal portion may be at 22 degrees C and a distal portion may be at 37 degrees C during calibration. Techniques to perform temperature controlled calibration of OSS tethers apply to all the different methods of calibration for OSS fibers. Methods for using temperature-adjusted calibrations to improve accuracy in a clinical setting are also presented.

Workstation 1 12 includes a display 1 18 for viewing images of a subject (e.g., a patient) or temperature control programs. Display 1 18 may also permit a user to interact with the workstation 1 12 and its components and functions, or any other element within the system 100. This is further facilitated by an interface 120 which may include a keyboard, mouse, a joystick, a haptic device, or any other peripheral or control to permit user feedback from and interaction with the workstation 1 12.

The system 100 for calibration of OSS fibers in a temperature controlled manner includes one or more forms which support or encapsulate the instruments 102 having the shape sensing optical fiber device 104 integrated therein. Calibration of OSS tethers may be performed at room temperature and may result in their optimal performance at the same state, but when operating at different temperatures inaccuracy and jitter reduce performance.

Methods for calibration of OSS tethers in a temperature controlled manner are hence important for optimal use of OSS at body temperatures during interventional procedures.

FIG. 1 shows a temperature controlled fixture 140 having a plurality of segments 142, each having a same or different geometric configuration, and each having a temperature control device 144 for changing and regulating the temperature of the segment 142. It should be understood that the geometric configuration, types of temperature control and the testing scenarios may include different configurations in accordance with the present principles. For example, FIG. 1 depicts the temperature control fixture 140 along a single dimension or in a single plane; however, in other embodiments the temperature controlled fixture 140 is disposed in 2 or 3 dimensions or planes. Such a configuration can account for any preferential error associated with OSS (say, if the measurement is more accurate in 1 direction than the other 2), wherein the error may be either due to reconstruction or specific to temperature.

The calibration of OSS tethers may include optical fiber sensing devices 104 or optical fiber sensing devices 104 integrated into an instrument 102. In one embodiment, the fixture 140 may be configured to calibrate an individual OSS tether by having the entire tether at an elevated temperature. This elevated temperature may be body temperature or other selected temperature. In another embodiment, calibration of tethers may be performed over a range of temperatures, e.g., from -10 degrees C to 100 degrees C in small intervals or more realistically from 10 degrees C to 50 degrees C, using shapes for segments 142 such as a straight line, a spiral, a helix, an anatomical shape, etc. that are needed to output calibration parameters, such as, e.g., twist rate and variation in refractive index of individual OSS cores. These parameters may be stored for appropriate use, such as, e.g., for comparison against measured calibration data or to be calibration data.

In another embodiment, the calibration fixture 140 may be programmed using a control module 124 such that a portion of the tether is at higher or lower temperature. This may include programming the temperature control devices 144 of different segments 142 to provide the desired temperature differences. The temperature control devices 144 are preferably controlled by a controller 146, which may include a hardware, software or combination device. The controller 146 may include the ability to not only control the segment temperatures but to control transition temperatures between segments 142. For example, different portions of the tether at different temperatures may include a smooth transition zone for temperature as well as one with a sharp transition, non-linear transition, a stepped transition, etc. The control module 124 orchestrates that temperature profile and collects measured OSS data which is stored as calibration data for given temperature and geometry conditions. The calibration data are stored in sets and correlated with the conditions in a data structure 126, which can be employed later during operational procedures. The data structure 126 may include temperature models employed to understand changes in data due to temperature variations.

The temperature control devices 144 may include cooling or heating elements. The elements may include solids, liquids or gases, and mechanisms for conduction, convection and/or radiation, for performing calibration of OSS during the control of temperature.

Dynamic heating schemes may include fluid baths for each segment 142 (e.g., a water bath with a pump that supplies fluid over all or a portion of the tether and maintains temperature in that region while calibration is performed). Air flow may also be employed for temperature control devices 144, or a combination of liquid and air baths may be employed for controlling the temperature of different segments 142. In other embodiments, the temperature control devices 144 may include a feedback sensor 147 (e.g., for measuring actual temperature) and electrically controlled heaters/coolers (144) inserted into a conductive mandrel (fixture 140). The mandrel 140 may be configured to receive and shape the OSS tether. Other temperature control devices 144 may include heat lamps, refrigerated baths, etc.

By controlling the temperature of the segments 142 (e.g., heating or cooling) different lengths of OSS tether may be subjected to different temperatures. Calibration parameters may be recorded for each temperature or other conditions and each length combination. Hence, based on detected length, the calibration parameters may be dynamically updated (for example, the dynamic update may be carried out using updates to a ni or .text file) during the calibration procedure. The calibration data is collected in a data structure 126 or model and employed to make adjustments to measured data during actual measurements under varying conditions (e.g., different temperatures, different geometries, etc.).

Referring to FIG. 2, in some embodiments, tensioning mechanisms 150 or torqueing or twisting mechanisms 152 may be employed to impart tensile or torsional strain to the OSS tether. Since effects of tension and axial strain are coupled, parameters to decouple these two parameters can be determined by maintaining a constant temperature or pattern of temperature and inducing axial tension in a known systematic manner to better correct for temperature effects in a central core, either for the entire OSS tether or subsections (segments 142) thereof.

While bare OSS fibers or integrated devices may be calibrated, it may be advantageous to calibrate a particular shape of an integrated device depending on its use. For example, a catheter in a pre-formed shape may be calibrated or adjusted to perform at a higher temperature in its distal portion since the distal portion is inserted in a patient and is most likely operated at a higher temperature, since certain devices activate and change properties at elevated temperatures. The Cobra™ catheter, for example, reduces stiffness at 37 degrees C. This property may be exploited by heating only the length of OSS in the preformed portion (portion to be inserted in a patient) of the Cobra™ to 37 degrees C, update the calibration, get the shape of the device and compensate for errors or jitter.

Referring to FIG. 3, once the device 104 or integrated instrument 102 is calibrated, the integrated instrument 102 may be employed in a procedure. The procedure may include scenarios where the integrated instrument 102 experiences multiple temperature domains. In such instances, the calibration data collected by the calibration system 100 may be employed for proper and accurate shape sensing of the integrated instrument 102. The same system employed for calibration (system 100) may be adapted for use during an interventional procedure or the like.

In one embodiment, immediately prior to use, a tip 202 of the instrument 104 can optionally be placed into a fixture 204 that maintains a specific temperature, or range of temperatures, to improve the configuration process (to select and load of the earlier gathered calibration profiles). The tip 202 could alternatively be partially inserted into the patient to provide a sample of the expected temperature for the given experiment. The fixture 204 may include one or more segments 142, temperature controller devices 144, etc., as described above.

Memory 116 includes data structure(s) 210 stored therein that include a host of temperature combinations per fiber or independent of fiber and their associated calibration data. In this way, OSS tethers subjected to temperature gradients can be compared under similar conditions to account for the temperature differences and yield more accurate shape sensing results. For example, if a laboratory is at 18 degrees C as opposed to 23 degrees C (approximately room temperature) the temperature difference effect can be corrected by having a sensor 212, such as a thermometer, thermistor or thermocouple or any other means to sense ambient temperature, and load the appropriate calibration as determined from the data structure 210.

In one embodiment, the sensor 212 may be deployed on a body 160 of a patient. The body temperature can be sensed instead of the ambient temperature, and the calibration parameters can be loaded accordingly in accordance with the data structure 210, e.g., a look up table, a graph or other model or indexed structure. In one embodiment, a combination of ambient temperature, body temperature and/or other temperature readings may be employed as input criteria to the data structure 210. From the data structure 210, appropriate calibration data is determined to analyze the shape sensing data to minimize jitter and error and to optimize performance. Temperature sensors may be disposed on or integrated into the shape sensing system to be able to track temperature profiles and match the profiles with the best calibration data stored in memory 1 16 (e.g., using the data structure 210 to correlate the data). In another embodiment, an adaptive search algorithm 216 may be stored in memory 1 16 and employed to search through a range of calibration data or options (for various

temperatures or conditions) and select the option/data set that minimizes jitter and instability and improves accuracy. The data structure 210 (from data structure 126) is configured to correlate temperature conditions with calibration data such that best fit calibration data is employed to adjust the OSS data to improve accuracy and reduce instability and jitter.

Referring to FIG. 4 with continued reference to FIG. 3, an illustrative diagram 302 shows a human form with a shape sensing enabled instrument 102 disposed partially inside and partially outside of a body 304. A corresponding graph 306 shows temperature (in degrees C) across the instrument 102 versus position (in cm). A transition region 308 into the body 304 is also shown. The transition region 308 may be defined using calibration data in accordance with the present principles. The user of the system may be permitted to specify or measure a launch temperature and a distal temperature(s) for use in the procedure. The OSS data returned is then compared to distinguish regimes, and calibration data is correlated to resolve different temperature regions. In another embodiment, since calibration data is available for different temperatures and/or temperature ranges, data 310 for inside the body 304 and data 312 for outside the body 304 can be compared to the calibration data to decipher the transition region 308. In this way, the calibration data may be employed to track the transition region 308 during a procedure.

Other techniques may be employed to back up the determination of the transition region. For example, a known registration shape may be employed at the position of entry, e.g., a known shape of at an introducer, to identify when the device has entered the body 304. In another embodiment, a single fluoroscopy (or other modality) image may be taken during the procedure to identify how much of the device is inside of the body 304.

Referring to FIG. 5, in another embodiment, temperature stability may be employed by providing a temperature reference 402 in a launch unit 404 and/or in an OSS enabled instrument 406. In one embodiment, a mechanism 408 for controlling temperature is provided within the launch unit 404. The mechanism 408 provides a known stable temperature such that the mechanism 408 acts as a reference (based on prior calibration), and can be used to pick and throw out the effects of variation. The temperature of the launch unit 404 may be varied pre-operatively or intra-operatively to achieve or find an optimal calibration with respect to temperature of a proximal portion of the instrument 406.

Referring to FIG. 6, in another embodiment, temperature control of the instrument 406 can also be performed to stabilize the OSS data. This can be achieved by including a temperature control device 405 in the instrument 406, e.g., by running a heated liquid or gas along a lumen 410 of a fiber or fibers within the instrument 406, via electrical conduction along a metal lumen 410, or other methods, etc.

Temperature variation across an OSS device can result in inaccuracy, jitter and instability of shape sensing. Using OSS calibration data will reduce these parameters. The present principles calibrate out effects of minor or extreme temperature fluctuation, such as fever (e.g., body temperature rising to 39 or 40 degrees C versus normal) radiofrequency ablations, microwave ablations, cryoablations, etc. and can be employed to detect the fluctuations as well. The present OSS system is able to determine portions of the device residing at different temperatures, i.e., inside versus outside the human body and show different spatially resolved OSS signals. Referring to FIG. 7, a method for calibrating an optical fiber shape sensing device is shown in accordance with the present principles. In block 502, a temperature for a plurality of segments is controlled using a temperature control fixture. Each segment is independently temperature controlled using one or more temperature control devices. The plurality of segments may each include a sensor, and the one or more temperature control devices may be controlled to provide a temperature for a respective segment. The segments may be configured to generate a temperature transition between them. The temperature transition may include one or more of a linear transition, a nonlinear transition, and a sharp transition.

In block 504, optical shape sensing (OSS) data is collected from an OSS instrument wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions. In block 506, the OSS data is employed as calibration data for use during an operation, etc. to reduce instability and jitter.

In block 508, a data structure, configured to store calibration data in memory, is created and can be consulted for adjusting measured data. The data structure is indexed with conditions such that the calibration data can be determined based on the conditions. In block 510, mechanical strain may be imparted by one or more tensioning mechanisms or

torqueing/twisting mechanisms to decouple axial strain from temperature strain. In block 512, measured OSS data is adjusted with or by calibrated OSS data to account for temperature differences.

In interpreting the appended claims, it should be understood that:

a) the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim;

b) the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; c) any reference signs in the claims do not limit their scope;

d) several "means" may be represented by the same item or hardware or software implemented structure or function; and

e) no specific sequence of acts is intended to be required unless specifically indicated.

Having described preferred embodiments for temperature controlled calibration for optical shape sensing (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the disclosure disclosed which are within the scope of the embodiments disclosed herein as outlined by the appended claims. Having thus described the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.

Claims

CLAIMS:

1. A calibration system for optical fiber shape sensing, comprising:

a temperature control fixture (140) including a plurality of segments (142), each segment being independently temperature controlled using one or more temperature control devices (144);

a processor (114);

memory (1 16) coupled to the processor; and

an optical shape sensing module (115) configured to interrogate and receive feedback from an optical shape sensing (OSS) instrument wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions such that the OSS data is employed as calibration data for use during operation of the OSS instrument to reduce instability and improve accuracy and jitter.

2. The system as recited in claim 1 , wherein the plurality of segments each includes a sensor (147), and the one or more temperature control devices (144) are controlled to provide a temperature for a respective segment.

3. The system as recited in claim 1, wherein the one or more temperature control devices (144) include a forced fluid or a heater/cooler.

4. The system as recited in claim 1, wherein the segments (142) include a form configured to hold the OSS instrument in a known shape.

5. The system as recited in claim 1, wherein the segments (142) are configured to generate a temperature transition therebetween, the temperature transition including one or more of a linear transition, a nonlinear transition, and a sharp transition.

6. The system as recited in claim 1, further comprising a data structure (126) configured to store calibration data in memory and being indexed with conditions such that the calibration data can be determined based on the conditions.

7. The system as recited in claim 1 , further comprising one or more tensioning mechanisms (150) or torqueing/twisting mechanisms (152) to impart tensile or torsional strain to the OSS instrument to decouple axial strain from temperature strain.

8. A system for temperature compensating an optical fiber shape sensing instrument, comprising:

a processor (114);

memory (1 16) coupled to the processor;

an optical shape sensing module (115) stored in memory and configured to interrogate and receive feedback from an optical shape sensing (OSS) instrument (104) wherein OSS data is collected by deploying the OSS instrument to gather OSS data when a length of the OSS instrument is under a plurality of different temperature conditions; and

a data structure (210) stored in memory and being configured to correlate temperature conditions with calibration data such that best fit calibration data is employed to adjust the OSS data to improve accuracy and reduce instability and jitter.

9. The system as recited in claim 8, wherein the OSS instrument (104) is deployed in a body having a temperature different from ambient and the calibration data being employed to determine a transition region into the body.

10. The system as recited in claim 8, wherein the OSS instrument (104) includes a temperature sensor (212) and calibration data associated with a measured temperature of the temperature sensor is employed in evaluating the OSS data.

11. The system as recited in claim 8, further comprising an ambient temperature sensor (212) and calibration data associated with a measured temperature of the ambient temperature sensor is employed in evaluating the OSS data.

12. The system as recited in claim 8, further comprising a launch unit (404) for the OSS instrument, the launch unit including a temperature reference (402) to maintain a temperature on the OSS instrument and employed to select a calibration data set to be employed for temperature variation correction.

13. The system as recited in claim 8, wherein the OSS instrument includes a temperature control device (405) configured to control a temperature across the OSS instrument.

14. The system as recited in claim 8, wherein the calibration data is employed to determine different temperature regimes for portions of the OSS instrument.

15. The system as recited in claim 8, further comprising a distal end portion temperature adjustment device (204) configured to maintain a temperature of the distal end portion of the OSS instrument to determine a calibration data set.

16. A method for calibrating an optical fiber shape sensing device, comprising: controlling (502) a temperature for a plurality of segments of a temperature control fixture, each segment being independently temperature controlled using one or more temperature control devices;

collecting (504) optical shape sensing (OSS) data from an OSS instrument wherein OSS data is collected by deploying the OSS instrument in or on the temperature control fixture to gather OSS data in accordance with a plurality of temperature conditions; and

employing (506) the OSS data as calibration data for use during an operation to adjust measured OSS data in accordance with the calibration data to reduce instability and jitter.

17. The method as recited in claim 16, wherein the plurality of segments each includes a sensor, and the one or more temperature control devices are controlled to provide a temperature for a respective segment.

18. The method as recited in claim 16, wherein the segments are configured to generate a temperature transition therebetween, the temperature transition including one or more of a linear transition, a nonlinear transition, and a sharp transition.

19. The method as recited in claim 16, further comprising consulting a data structure (210) configured to store calibration data in memory and the data structure being indexed with conditions such that the calibration data can be determined based on the conditions.

The method as recited in claim 16, further comprising imparting (510) mechanical strain by one or more tensioning mechanisms or torqueing/twisting mechanisms to decouple axial strain from temperature strain.

21. The method as recited in claim 16, further comprising adjusting (512) measured OSS data with calibrated OSS data to account for temperature differences.