Percutaneous Catheter System and Method for Rapid Diagnosis of Lung Disease

Abstract

A percutaneously delivered medical device and its method of use includes a catheter, at least two electromagnetic sensing coils located within the distal tip of the catheter, and at least one within the proximal handle, and a multi-element planar ultrasound transducer array located within the distal tip of the catheter and configured to transmit and receive ultrasonic energy in at least two imaging modes. The device also includes an imaging system coupled to the ultrasound transducer and is used for creating an image of tissue in a first target plane that extends orthogonally from the catheter body. The medical device also includes a backscatter evaluation system for use in receiving and evaluating the acoustic spectral characteristics of tissues within a second target area within the first target plane.

Claims

1. A medical device for operation by a physician user, in a patient's lung tissue having a suspected tumor, the medical device comprising: a) a catheter having an elongate catheter body terminating in a proximal handle and extending along an axis to a distal tip, said elongate catheter body adapted for delivery to lung tissue by insertion through a percutaneous needle; b) at least one first electromagnetic sensing coil, located within said distal tip; c) at least one second electromagnetic sensing coil in said proximal handle; said first electromagnetic sensing coil and said second electromagnetic sensing coil operating together to permit navigation through lung tissue and for reporting the location of said catheter distal tip in said lung tissue; d) an ultrasound transducer array located within said distal tip for transmitting and receiving ultrasonic energy, said ultrasound transducer array operating in a first imaging mode to acquire an image of a first target area located in a first target plane and to define a second target area located in said first target plane comprising a reduced second target area smaller than said first target area; e) said ultrasound transducer array operating in a second backscatter mode; f) a module in communication with the ultrasound transducer array and configured to evaluate the spectral characteristics of acoustic energy reflected from said second target area forming a quantitative ultrasound data set; and g) a navigation system/us display to present navigation, location and ultrasound data to said physician user.

2. The medical device of claim 1, wherein the ultrasound transducer array comprises a plurality of transducer pairs, each transducer pair comprises a first transducer functioning as a transmitter and a second transducer functioning as a receiver.

3. The medical device of claim 2, wherein a first transducer pair of the ultrasound transducer array operating at a first frequency in the first imaging mode and a second transducer pair of the ultrasound transducer array operating at a second frequency in the second imaging mode.

4. The medical device of claim 2, wherein the plurality of transducer pairs are located along the length of the distal tip.

5. The medical device of claim 3, wherein the first transducer pair and the second transducer pair operate at the same time.

6. The medical device claim 1, wherein the reduced second target area is selected to be free of anatomic detail displayed in the first target plane.

7. The medical device of claim 2, wherein a compensation profile is generated for each transducer in the ultrasound transducer array over the entire operating range of the transducer.

8. The medical device of claim 7, wherein each compensation profile is stored in a computer readable memory located in the catheter.

9. The medical device of claim 2, further comprising at least one independent transducer functioning as a sensor and located at a point along the length of the distal tip.

10. The medical device of claim 9 wherein the independent transducer is configured to receive ultrasonic energy produced in the first imaging mode and the second imaging mode.

11. The medical device of claim 10, wherein the at least one independent transducer is a plurality of independent transducers, the plurality of independent transducers located along the length of the distal tip.

12. The medical device of claim 11, wherein the plurality of independent transducers are operated at the same time.

13. The medical device of claim 10, wherein the plurality of independent transducers are operated separately.

14. A method of diagnosing a region of interest within lung tissue of a patient comprising the steps of: a) passing a catheter through a percutaneous needle to access said lung tissue, the catheter comprising: i) an elongate catheter body including a longitudinal axis and a distal tip and a proximal handle, ii) at least two distal electromagnetic sensing coils located within said distal tip, iii) at least one proximal electromagnetic sensing coil located in the proximal handle, and iv) a multi-element ultrasound transducer array located within said distal tip, the ultrasound transducer array positioned parallel to the longitudinal axis of said catheter body; b) navigating said distal tip of the catheter to a first location proximal to the region of interest using a navigation system that interacts with the distal and proximal electromagnetic sensing coils; c) in a first imaging mode, transmitting from the ultrasound transducer array first ultrasound energy into the region of interest in a first target plane; d) receiving the first ultrasound energy from the transducer array at an imaging system; e) at the imaging system, creating an image of the region of interest along the first target plane, the image showing an anatomic structure, said anatomic structure selected from a set of structures comprising airways and blood vessels; f) identifying a second target area within the first target plane comprising a reduced second target area smaller than said first target area; g) in a second imaging mode transmitting second ultrasound energy from the transducer array into the reduced second target area; h) receiving the second ultrasound energy from the transducer array at a backscatter evaluation system; i) at the backscatter evaluation system, evaluating the acoustic spectra of the received second ultrasound energy to form a quantitative ultrasound data set.

15. A medical system, comprising: a catheter terminating in a proximal handle and extending along an axis to a distal tip, the catheter adapted for delivery to lung tissue by insertion through a percutaneous needle; an ultrasound transducer array located within said distal tip for transmitting and receiving ultrasonic energy, wherein the ultrasound transducer array comprises: a first transducer having first geometric properties corresponding to a first resonant frequency, and a second transducer having second geometric properties corresponding to a second resonant frequency that is higher than the first resonant frequency; and a module that is operably coupled to the ultrasound transducer array and configured to cause: the first transducer to operate at the first resonant frequency in an imaging mode for generating ultrasound images of a target tissue, and the second transducer to operate at the second resonant frequency in a quantitative ultrasound mode for generating spectral parameters associated with the target tissue, wherein the spectral parameters are usable for characterizing the target tissue via an in situ acoustic biopsy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a perspective view of the catheter located in a percutaneous access needle;

[0029] FIG. 2 is a cross section view of an alternative handle for the proximal end of the catheter;

[0030] FIG. 3 is a perspective view of the distal tip portion of the catheter system;

[0031] FIG. 4 is a cross section of the distal tip of the catheter;

[0032] FIG. 5 is a schematic block diagram of the electronic portioning of the systems;

[0033] FIG. 6 is a schematic view showing the first target image plane

[0034] FIG. 7 is a schematic view showing the reduced second target image plane;

[0035] FIG. 8 is a spectral diagram showing illustrative acoustic parameters for QUS.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

[0036] FIG. 1 is a perspective view of the catheter assembly 14 located in a percutaneous access needle 10. The elongate catheter body 18 extends from the distal tip 16 seen best in FIG. 3 to the proximal handle 12 seen best in FIG. 1. An alternative handle 9 with an axial cable 7 is seen in FIG. 2 in contrast to the lateral cable 15 route of handle 12. Typically, the physician will advance the distal tip 16 out of the needle 10 by pushing the handle 12 relative to the needle base member 11. The trocar end of the distal tip seen at 19 may then be used to take a sample of tissue such as that of a lymph node, lung tissue, etc.

[0037] FIG. 2 which shows an alternate handle 9 construction with the cable 7 aligned with the long axis 21 of the catheter body 18. The handle 9 in FIG. 2 shows an elongate sensor coil 37 located in the handle proximal end along axis 47. This sensor coil 37 is orthogonal to at least one sensor in the distal tip 16 shown in superposition in FIG. 2 at reference numeral 39. At least one more sensor is located in the tip as well illustrated by the superposition of coil elements 33 and/or 39. In use and in combination with the distal coils 33, 35 and/or 39 the navigation system can report and display the angular relationship of the catheter body to the physician. That is the display will show the orientation and direction of travel for the catheter system 14 in real time.

[0038] FIG. 3 is a perspective view of the distal tip in isolation showing the cylindrical orientation of the ultrasonic array 30 just proximal of the trocar end 19.

[0039] FIG. 4 is a schematic cross-section of the distal tip 16 showing a planar array wrapped around a shell 17 thus forming the cylindrical array 30. The gap 31 shows the seam of the array 30. The array 30 includes multiple transducer elements of which two are shown as elements 41 and 43. The EM coils (e.g. coils 33, 35 and 39 shown in FIG. 2) are placed behind or proximal of the array 30 and cannot be seen in this cross section view. A lumen 38 is centrally positioned to receive a guidewire therethrough.

[0040] FIG. 5 is a partitioning of the electronic componentry in an illustrative but not limiting version of the system.

[0041] The electronic package 34 will contain among other things a programmable chip to configure the array 30. A multiplexer will format and transmit data from the catheter system to the patient interface module PIM 42, which will be hung bedside on the gurney with the patient. The PIM 42 includes electrical isolation to protect the patient and also contain power supplies for the catheter itself, A/D conversion and various buffering processes are accomplished in the PIM to improve noise performance of the catheter. In this implementation a separate “pizza box” enclosure 44 carries dedicated hardware for the synthetic aperture beam forming and control as well as the spectral analysis of the backscattered signals for the QUS processes. The enclosure is coupled to the workstation based navigation and display cart. It is expected that the content of the pizza box enclosure 44 will be incorporated into the workstation 46 itself in further iterations of the product.

[0042] The catheter body 18 has a matrix of individually addressable piezoelectric transducers elements, of which two are depicted in FIG. 4 as elements 41 and 41, which are fabricated into an array 30 using micromachining technology. Each element of the array can be powered to emit ultrasonic energy as a spherical wave emanating from the specific transducer location, and each element in the array can function as a receiver transducing the mechanical energy of backscattered sound into a an electrical signal. Once a wave is launched from a given element, such as element 41, a companion transducer, such as element 43, can detect the backscattered energy reflected off of biologic tissues. In the synthetic aperture scenario only one transducer is listening to the transmitting transducer element at a time.

[0043] In general pairs of elements will be activated with one element 41 functioning as a transmitter of acoustic energy and the companion element 43 functioning as a receiver. Since the elements are arrayed in space several viewpoints are present in the array. This provides much improved lateral resolution when compared to prior art approaches.

[0044] With that data stored, a next transducer in the array is activated to transmit acoustic energy and its complimentary transducer receives the backscattered return signal. With many, for example 64 transducers, at various locations, the composite of all the returned energy from all the locations can be used to form though computation an image plane orthogonal to the plane of the transducer. It is possible to have more than one transducer pair active at a time and in the exemplary embodiment 4 channels of data are collected synchronously. The limitations are based on complexity and power dissipation and bandwidth of the data paths. Consequently other configurations are possible and anticipated within the scope of the claims. The mathematics to pull an image in a plane from the time sequenced multiplex data that is transmitted and received at various points in space is complicated but well known and understood in the field. In general the displayed image plane is synthesized from data taken at many locations in space taken at different times, that are collectively convolved into a single image plane hence the term synthetic aperture. If one moves the catheter along a path the synthetic aperture image plane sweeps out a volume. This is a relatively low resolution image of a volume of tissue but can help to resolve the extent of anatomy to supplement the detection of anatomic structures such as airways, blood vessels, and the like in the 2-D first image plane area. In this regard the methodology of the invention may rely on a first target image area in a plane or rely on a 3-D volume called the first target image volume. In this later case catheter movement is used to define the first 3-D volume of target tissue.

[0045] In use there are two modes of operation for the ultrasound transducer array. In a first mode, the amplitude and envelope information from the backscattered acoustic energy is used to form an image presented to the clinician. This may be a first 2-D slice of target tissue or a 3-D volume of target tissue. In a second mode the transmitted power is reduced to select a smaller target plane or volume within the first image plane or image volume. This reduced view is called the second reduced area or slice in the event of a 2-D slice or a second reduced volume in the event of a 3-D volume. In each case the reduced view is selected to be free of anatomic detail observed in the first view. The exclusion of gross anatomic structure selects a homogenous sample for quantitative analysis. The spectra of the backscattered energy from the reduced area slice or volume is evaluated quantitatively and automatically rather than used to form an image. The image free quantitative information is used to determine if the reduced area of tissue exhibits the acoustic characteristics of cancerous tissue. The precise characteristics or the acoustics of cancer is a topic of study at the present time.

[0046] FIG. 6 shows a portion of the catheter assembly 14 without the access needle to facilitates discussion of operation of the device. The catheter body 18 is shown in situ in a patients lung, with the distal tip located at position “1” marked 60 in the figure. The first target plane 62 show in light hatch is an image plane intersecting a suspected tumor mass 64 that lies near an airway 66 and is crossed by a blood vessel labeled 68 twice in the figure. This image mode ultrasound data is used to find the suspect tumor mass and to verify and note its location.

[0047] FIG. 7 shows the catheter body 18 repositioned or moved slightly so that the backscatter associated with reduced target plane 72 does not intersect the blood vessel or airway. This is the reduced second image plane used for backscatter evaluation for QUS.

[0048] FIG. 8 shows a spectral graph of normalized reflected acoustic power on the Y-axis and the corresponding frequency on the X-axis. Squares typified by square 100 depict the amplitude of reflected power at the corresponding frequency. One can draw a “best fit” line 102 through the various data typified by data point 100. The slope of this line is a useful parameter and is identified on the figure at 104. The point where the best fit line 102 crosses the y axis is the Y-intercept 88. If one excludes both high and low frequencies defining a mid-band the arithmetic average of the remaining values' forms the mid band fit value 86 shown on the figure.

Calibration and Alternative Embodiments

[0049] In general the ultrasound spectra will be normalized to perform the QUS parameters. However the absolute energy in the reflected signal has diagnostic value alone and it is expected that the not normalized spectra will be used clinically as well. For this reason among others it will be important to calibrate individual catheter sensors. The ultrasound transducer technology as well as fabrication methodology results in widely varying sensitivity and other acoustic properties. It is anticipated that each sensor will be characterized during the manufacturing process to generate a compensation profile for the sensor over its entire operating range. This unique calibration table will be stored onboard the catheter is an appropriate read on memory.

[0050] It is generally preferred to have a radial US transducer to carry out the inventive steps, however as an alternative the sensor could be a linear structure forming a pie shape field of view. Also this pie shaped field of view ay be stepped around a circle either mechanically or electronically.

[0051] An additional EM sensor may be paced in the handle and this proximal EM sensor system may be used with the EM sensor array in the distal tip to translate physician motion which affects the sensors to provide information and feedback to the physician about the orientation of the catheter system. In this version the relative motion or position of the two EM sensors along with the known geometry of the catheter allow for the computation of the location of the tip or another attribute of the catheter.

[0052] Note that there are several independent US transducers along the length of the distal tip of the catheter. Each US transducer forms a separate station. In this configuration the catheter need not be moved to survey an extended volume of tissue. In use each US station may form an image plane that is relatively small. The sensor transducer stations may be adjacent to each other or spaced apart. Acoustic energy backscattered from this image plane is interpreted as both an image as well as subjected to QUS interpretation for tissue characteristics. By engaging all transducer at the same time or engaging them separately the operator can get an estimate of the size of the lesion of interest.

[0053] The single plane configuration of the percutaneous US needle will create a single image plane using a single 16 to 64 element ultrasound transducer ring around the needle. Additionally multiple similar rings can be added to the needle to produce a 3D ultrasound image volume from multiple image planes. The device can be sequenced in numerous patterns to create image, the most basic being send on one element and listen on multiple adjacent elements on the same ring. It is also possible to send on one ring and listen on multiple rings on the same side of the needle.

[0054] The rings could either be side by side or spaced apart to create different sampling and imaging capabilities. In an acoustic biopsy application, the ability to collect backscatter RF energy from multiple angles simultaneously about a single location in the tissue is advantageous. This enables the ability to have correlated QUS data instantaneously at a location in the tissue. Having two rings 5-10 mm apart creates significantly different RF signatures for the single tissue location on each ring due to differentiated tissue and anatomy in the acoustic path.

[0055] The available transducers of a multi-element array will also allow the transmit and receive functions to be carried out at differing locations. It is expected that this will increased the quality of analysis.

[0056] It should be noted that the backscattered radiation may be normalized with respect to the acoustic energy delivered to the tissue or the actual absolute value of the radiation may be evaluated. There is evidence that the total absorption of acoustic radiation of tissue has diagnostic value.

[0057] In general the analog nature of the transducer technology as well and the relatively long signal paths can be addressed by a calibration process during transducer manufacture. It is expected that each catheter will be calibrated and calibration information stored along with unit ID in a read only memory integrated in to the catheter product.

[0058] Although described with regard to representative embodiments various departures and additions may be made without departing from the scope of the invention as expressed in the claims. At least one embodiment of the present percutaneously delivered catheter system and its method of use may be described as follows:

[0059] A catheter assembly 14 is shown in FIG. 1 that is operated by a physician user (not shown) who percutaneously advances the catheter assembly into a patient's lung tissue having a suspected tumor (via needle 10). The assembly comprises a catheter body 18 terminating in a proximal handle 12 and extending along an axis to a distal tip 16. At the distal tip 16, a plurality of distal electromagnetic sensing coils 33, 35 and/or 39 are positioned. At least one other electromagnetic sensing coil 37 is positioned in the proximal handle 12. The sensing coils operate together to permit navigation through lung tissue and for reporting the location of said catheter distal tip 16 in said lung tissue. A cylindrical ultrasound transducer array 30 is also located within the distal tip 16 and is configure for transmitting and receiving ultrasonic energy such as in the manner described above and shown in FIGS. 4, 6 and 7.

[0060] The cylindrical ultrasound transducer array 30 operates in a first imaging mode to acquire an image of a first target area located in a first target plane, and for defining a second target area located in said first target plane comprising a reduced second target area smaller than said first target area, such as is shown in FIG. 6 and described in greater detail above. The cylindrical ultrasound transducer array 30 also operates in a second, backscatter mode, to evaluate the spectral characteristics of acoustic energy reflected from said second target area such as in the manner shown in FIG. 7 and forming a quantitative ultrasound data set.

[0061] The catheter assembly is part of a system, such as is illustrated in FIG. 5, that also includes a navigation system/ultrasound display to present navigation, location and ultrasound data to said physician user.

[0062] The many features and advantages of the invention are apparent from the above description. Numerous modifications and variations will readily occur to those skilled in the art. Since such modifications are possible, the invention is not to be limited to the exact construction and operation illustrated and described. Rather, the present invention should be limited only by the following claims.