TITLE: NEEDLE POSITIONING APPARATUS AND METHOD
FIELD OF THE INVENTION
The present invention relates to a needle guide positioner. In particular, the present invention relates to an apparatus and a method for accurately positioning a needle guide with respect to a target within a patient body to facilitate different clinical procedures involving needle insertion into the patient body.
BACKGROUND
Biopsy is a medical procedure in which cells or tissues are removed from the body for examination. The procedure involves removing specimens of a tissue from part of a lesion. These specimens are then examined under the microscope to determine the problem.
In a typical biopsy procedure, the affected part of the patient body is scanned to pinpoint the location of the lesion. In order to extract samples from the lesion, a needle is inserted to touch the lesion. The needle is inserted such that it does not puncture any other vital organ or structure in the patient body. Currently, the biopsy incisions are usually made by hand. The practitioner determines the point of insertion of the biopsy needle by external measurements. For example, the point of insertion can be determined by placing a cotton pellet mixed with contrast or iodine. It can also be done by drawing lines on the patient or by marking the area of entry by a marker. The position and angle of the insertion may not be accurate resulting in repeated insertions in the patient's body.
Image guided interventional procedures are preferred by practitioners. Such procedure shows the path taken by the needle during insertion, thereby reducing the risk to the patients and increasing the accuracy. Also, image guidance helps to avoid unwanted injury to vital organs and blood vessels. Commonly used imaging systems are Ultrasound, X-Rays, C-Arms, Computed Tomography Scanners, Magnetic Resonance Imaging etc.
Information relevant to attempts to address these problems can be found in US patents US6785572, and US6246898; US patent applications US2004152970A1 , US2005177054A1 , and US2006020279A1 ; European patent EP1524626, and WIPO patent application WO03091839A2. However, each one of these references suffers from one or more of the following disadvantages. Firstly, these devices require real time imaging and tracking of the needle. Therefore, the radiation exposure time to the patient and practitioner is high. Secondly, the cost of such devices as well as the preparation time for setting up these devices is high. Thirdly, existing procedures require repeated punctures in the patient body for accurate positioning of the needle.
In light of the drawbacks of the existing art, there exists a need for an apparatus and a method for accurate positioning of a biopsy needle. Further, there exists a need for an apparatus and a method for accurate positioning of a needle guide such that the practitioner does not need to do repeated insertions to reach the lesion of interest. Additionally, there is a need for an apparatus and a method that can allow biopsy insertions to be performed with minimal exposure to radiation.
SUMMARY
An object of the present invention is to provide a device for accurate positioning of a needle guide.
Another object of the invention is to reduce the number of punctures made on the body during biopsy procedure, thereby reducing the time of the procedure and the discomfort to the patient.
Yet another object of the invention is to provide an apparatus and a method that allows for needle positioning in an offline mode by using the images acquired during CT scan, without constant exposure to scanning radiations.
In accordance with the abovementioned objectives, an apparatus for accurate positioning of a needle guide is disclosed. The apparatus provides a means for taking as input the position vector of a point of insertion of the needle into the body. This point of insertion can be selected from images produced by a Computer Tomography system. Similarly, the apparatus has a means for taking as input a point of target. A controller determines the direction vector between the point of insertion and the point of target. A guide manipulator accurately positions the needle guide in line with the direction vector, such that the needle can easily be inserted through the guide to the point of target. A plurality of motors facilitates the positioning of the guide manipulator in accordance with the direction vector.
In an embodiment of the invention, the apparatus is a multi-axis needle manipulator. The apparatus has a clamp capable of linear movement along at least one axis. Attached to the clamp is a positioning element including first and second member. The first and the second members are capable of rotating along mutually perpendicular axes. A means for determining position vectors obtains position information for the point of insertion and the point of target. A controller determines the spatial orientation of the positioning element and the clamp based on the position vectors of the point of insertion and the point of target. The needle guide is aligned to the spatial orientation through the help of a plurality of motors.
In an embodiment of the invention, positioning of guide manipulator can be achieved by combined motion of the platform on which the patient is placed and the multi-axis needle manipulator.
In an embodiment of the invention, the apparatus consists of a multi-axis needle manipulator and the platform on which the patient is placed. The multi-axis needle manipulator is fixed on the ground. The multi-axis needle manipulator has a clamp capable of linear movement along one axis. Attached to the clamp is a positioning element including first and second member. The first and the second members are capable of rotating along mutually perpendicular axes. The platform is capable of moving along two mutually perpendicular axes. A means for determining position vectors obtains position information for the point of insertion and the point of target. A controller determines the spatial orientation of the positioning element, the clamp and the platform based on the position vectors of the point of insertion and the point of target. The needle guide and the platform are aligned to the spatial orientation through the help of a plurality of motors.
BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which:
FIG 1 shows the environment in which the apparatus of the present invention works;
FIGs 2A and 2B are a schematic representing the insertion of a needle to a point of target in accordance with an embodiment of the invention;
FIG 3 illustrates an embodiment of the needle positioner in accordance with an embodiment of the present invention;
FIG 4 is an orthogonal view of the guide manipulator in accordance with an embodiment of the invention;
FIG 5 depicts an orthogonal view of the positioning element in accordance with an embodiment of the invention; FIG 6 is a schematic of the controller in accordance with an embodiment of the "invention;
FIG 7 is a schematic of the data input means in accordance with an embodiment of the invention;
FIGs 8A, 8B, 8C, and 8D illustrate the computation of the direction vector for aligning the needle guide;
FIG 9A, 9B are flowcharts illustrating , the method to position a needle guide in accordance with an embodiment of the invention; and
FIG 10 illustrates a skin level sensor for providing correction to the spatial orientation of the needle guide, in accordance with an alternative embodiment of the invention;
DETAILED DESCRIPTION
An apparatus and a method for accurate positioning of a needle guide are disclosed. The apparatus accurately positions a needle guide with respect to a point of target within a patient body. The needle guide has a split-bush to facilitate guiding of the needle through the slot provided. Such needle positioning is useful for various clinical procedures including, but not limited to, targeted medicine delivery, biopsy, bone marrow extraction, fluid biopsy, liposuction, orthopedic procedures and the like.
Accurate placement of a needle within the body'can dramatically change patient management. It can help to avoid invasive surgeries and minimize morbidity and mortality. Examples of use of needle insertion includes: percutaneous biopsies (acquiring of tissue for pathological analysis which gives accurate diagnosis), drainage procedures (aspiration of unwanted toxic fluids from within the body), focal injection of medications (treatment of cancers and pain management), ablation of tumors (in treatment of tumors by radio frequency, cryo and laser energy), vertebral facetal injections, focused irradiation of tissues.
The apparatus, in accordance with an embodiment of the invention, provides a multi-axis manipulator, which takes scanned images of the affected portion of the body as input. The precise points of insertion and target are determined from these images. This can be done manually by an expert or it can be device-assisted, through image analyzing technology. The manipulator aligns the needle guide for facilitating the easy and accurate insertion of the needle with respect to the point of target. FIG 1 shows the environment in which the apparatus of the present invention works. Apparatus 102 works in conjunction with an imaging system, such as a Computer Tomography (CT) system 104.
The following description is an embodiment of the invention, where the imaging system is a CT system. However, it would be apparent to a person skilled in the art that the system and the description is true for any other imaging system such as a MR (Magnetic Resonance) imaging system, a PET (Positron emission tomography) imaging system or any other imaging system. According to an embodiment CT system 104 has a movable platform. From now on the movable platform would be referred as cradle 106. A patient's body 108 is placed on cradle 106 and slid into a gantry 110 for CT imaging. Inside gantry 110, images of the affected area in the patient's body 108 are taken. These images are slices of the affected area, i.e., a series of cross-section views of the affected area in the patient's body 108. For example, the images could be CT scan images of the patient's brain. CT system generates a three-dimensional image of the internals of the affected area of the patient's body 108 from a large series of two-dimensional X-ray images taken around a single axis of rotation. These series of images are also referred to as image slices. While the system of the present invention has been discussed in conjunction with a CT imaging system it will be apparent to one skilled in the art that the CT system is used for exemplary purposes only. Other systems for obtaining an image of the affected area of the patient's body 108 can be used without deviating from the scope of the invention. In different embodiments, different imaging systems including an MR (Magnetic Resonance) system, a PET (Positron emission tomography) system are used in conjunction with apparatus 102.
According to the one embodiment of the invention, apparatus 102 is docked rigidly onto the floor.
The docking process comprises fixing a docking plate on the floor at the time of installation of apparatus 102. The docking plate acts as a platform to dock apparatus 102 on which apparatus 102 can be fixed. At the time of installation apparatus 102 is calibrated using a phantom wherein the precise location coordinates of apparatus 102 are determined with respect to the gantry center. The location coordinates are stored in the processor memory. This docks apparatus 102 with reference to the gantry center. The location coordinates are stored in the processor memory. The installation of docking plate on the floor fixes apparatus 102 at a constant distance from gantry center of the imaging system. The gantry center here has been defined as center of gantry 110 of the imaging system.
Apparatus 102 takes imaging data from the CT system in the form of DICOM images. Digital Imaging and Communications in Medicine (DICOM) is a comprehensive set of standards for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. DICOM files can be exchanged between two systems that are capable of receiving image and patient data in DICOM format. The DICOM images from the CT system are received by apparatus 102. Apparatus 102 facilitates the marking of the points of insertion and target on the DICOM images. The coordinates of the needle guide are calculated and fed into a processor in apparatus 102. The details of obtaining the points of insertion and target, and computing the coordinates are discussed in conjunction with FIG 5 and FIG 6.
FIGs 2A and 2B are schematics representing the procedure of needle insertion useful for clinical procedures such as biopsy in accordance with an embodiment of the present invention. FIG 2A is Superior Inferior (Sl) plane view, while FIG 2B is a horizontal section view of the affected portion of the patient's body 108. The needle is required to enter the patient's body 108 at point of insertion 202 and is required to touch target 204 at point of target 206. In one embodiment of the invention, target 204 is a lesion in the patient's body 108. In an alternate embodiment, target is a particular organ in the patient's body 108 for targeted delivery of medicine.
Point of insertion 202 and point of target 206 can be manually identified by a medical specialist. In an alternative embodiment of the invention, point of insertion 202 and point of target 206 can also be automatically identified through image recognition techniques. Details regarding the identification of point of insertion 202 and point of target 206 are discussed in conjunction with FIG 5. Point of insertion 202 and point of target 206 are identified such that the needle can directly reach the point of target 206 without damaging internal body parts 208 and 210 that may lie in between the point of insertion 202 and point of target 206.
In the embodiment of the invention the center of the face of the CT gantry 110 is chosen as gantry zero(origin: x=0, y=0, z=0) of the coordinate system as shown in FIG. 1. It is typically the center of the entry face (a circle) of the gantry (the cylinder). Z-axis of the coordinate system is aligned along the movement of cradle. The direction of Z- axis is as shown in FIG.1. Y-axis of the coordinate system is aligned perpendicular to cradle 106, as shown in FIG. 1. The direction of Y-axis is as shown in FIG. 1. X-axis of the coordinate system is aligned perpendicular to Y-Z plane. The direction of X-axis is as shown in FIG. 1. As depicted in FIGs 2A and 2B, the needle needs to be inserted along a direction vector 212 which is at angles α and β from x and z axis respectively to ensure that it reaches point of target 206 seamlessly without affecting any organ internal body parts 208 and 210. The direction vector 212 is difference between the position vector of point of target 206 and the position vector of point of insertion 202.
FIG 3 illustrates the needle positioner in accordance with an embodiment of the present invention. Apparatus 102 has a guide manipulator 302, a data input means 304, and a controller 306. Data input means 304 obtains data related to the coordinates of point of insertion 202 and point of target 206. Data input means 304 has been discussed in detail in conjunction with FIG 7. Controller 306 uses the abovementioned data related to the coordinates of point of insertion 202 and point of target 206 for determining the direction vector 212 from point of insertion 202 to point of target 206. Controller 306 further computes the spatial orientation for the needle guide to facilitate the entry of the needle into the patient's body 108 at the point of target 206. Controller 306 manipulates guide manipulator 302 to precisely align the needle guide with respect to the patient's body 108. The needle guide is positioned such that it facilitates easy insertion of the needle from point of insertion 202 to point of target 206. Guide manipulator 302 is discussed in detail in conjunction with FIG 4. Controller 306 is discussed in detail in conjunction with FIG 6.
FIG 4 is an orthogonal view of guide manipulator 302 in accordance with an embodiment of the invention. According to an embodiment of the invention, guide manipulator 302 is capable of motion in three linear directions that allows guide manipulator 302 to position the needle guide to the point of interest. Further, guide manipulator 302 has angular motion in two directions that facilitates the angular entry of the needle into the patient's body 108. Guide manipulator 302 has a clamp 402 and a positioning element 404. Clamp 402 in guide manipulator 302 provides linear motion along three mutually perpendicular axes while positioning element 404 provides two angular degrees of freedom. Apparatus 102 is able to accurately position itself with respect to patient's body 108 by using the movement in these five axes.
Clamp 402 is mounted on a mobile platform 405. Mobile platform 405 is mounted on wheels 407. Mobile platform 405 is also capable of being docked on the docking plate. In one embodiment, wheels 407 can be of castor type which means that the"wheels are mounted with an offset steering pivot such that the wheels will automatically swivel to align themselves in the direction where they are pushed. Mobile platform 405 can be positioned near cradle 106 and can be locked in the desired position using a magnetic lock as well and not limiting only to grounded locking system as discussed herein. Wheels 407 allow easy movement of guide manipulator 302. Mobile platform 405 can be moved manually or can be computer controlled. In the present embodiment, guide manipulator 302 is fixed to a docking plate at a fixed distance from the gantry center.
In an embodiment of the invention, clamp 404 has arms 408, 410 and 412 for movement along each of the three perpendicular axes. Arm 408 provides movement along the x-axis, arm 410 provides movement along the y-axis, and arm 412 provides movement along the z-axis.
Arm 410 provides the height movement. This vertical distance is effected by ball screw- spline and stepper motors. Ball screw spline mechanism is used to provide the combination of rotation and translation on a single compact design. The ball screw mechanism can achieve three modes of motion (rotational, linear and spiral) on a single shaft by rotating and stopping the ball-screw and spline nuts through the motion coordination of two motors. The ball spline has an angular-contact structure that causes no backlash in the rotational direction, enabling precise positioning of the needle guide. Moreover as the ball-screw is based on the end-mechanism, smooth movement can be achieved with low noise. Such a mechanism is suited in providing precision to the vertical movement of the horizontal frame and hence accurate y-direction motion. Further, for applications where precise measuring of a motors' rotor position is critical, a stepper motor is usually the best choice. Stepper motors operate differently from other motors; rather than voltage being applied and the rotor spinning smoothly, stepper motors turn on a series of electrical pulses to the motor's windings. Each pulse rotates the rotor by an exact degree. These pulses are called "steps", hence the name "stepper motor". Stepper motors are traditionally used in various motion control applications. Stepper motors are quite easy to wire and control. Stepper systems are economical to implement, intuitive to control, and have good low speed torque, making them ideal for many low power, computer-controlled applications. They can be for example interfaced to computer using few transistors and made to rotate using software. This provides further precise control over the vertical movement of the. horizontal bar arms 408 and 412 by the controller 306. An encoder is used to provide information on the position of the needle guide. Encoders measure the rotation of the motors to a precise degree. The encoder provides feedback to the controller 306 to precisely control the movement of the motors to an accuracy of less than 0.1 degrees.
The horizontal bar frame_consists of two bar frames arm 408 and 412. The bar lrame arms are attached in an L-shape such that they can slide perpendicular to the each other. The horizontal bar system provide motion in x and z direction. The end of the horizontal bar system has a positioning element 404. Positioning element has been illustrated in detail in FIG 5.
According to an embodiment of the invention, guide manipulator 302 is docked firmly to the docking plate on the floor at a distance Z=Zm. This fixes the z- distance (horizontal distance) of the needle guide and positioning element 404 from the gantry center at Z=Zm. Arm 410 provides the movement along y-axis. Arm 408 provides the movement of the needle guide along the x-axis. Arm 402 provides the movement of the needle guide along the z-axis if required. Further, positioning element 404 provides two angular degrees of freedom that facilitates the positioning of needle guide along the desired angular orientation at the point of insertion on the patient's body 108. Arms 408 and 410 provide movement along the x-axis as well as the y-axis while movable cradle 106 moves along z -axis. In an alternative embodiment of the invention the vertical y movement is also provide by the y motion of cradle 106. The vertical movement of cradle 106 adjusts the patient's body to the appropriate level. In the present embodiment of the invention, the x and y movements of the needle guide is actuated by the horizontal and vertical movements of arms 408 and 410 respectively by the computed distances. Thereafter, positioning element 404 provides the precise angular orientation by combination of two rotations. The rotation and positioning elements have been discussed in conjunction with FIGs. 5A and 5B.
The docking mechanism at Z=Zm docks guide manipulator 302 accurately with respect to gantry 110. The docking station also ensures parallel alignment of guide manipulator 302 with respect to the platform. Apparatus 102 is connected to a controller 306 that controls the motion of guide manipulator 302 and clamp 402. Details of controller 306 are discussed in conjunction with FIG 5.
FIGs 5A and 5B depict two orthogonal views of the positioning element 404. Positioning element 404 provides angular movement of a needle guide 502. Positioning element 404 comprises two components - a first member 504, capable of rotating about a first axis 506, and a second member 508 capable of rotating about a second axis 510. ^\xes 506 and 510 are mutually perpendicular. FIGs 5A and 5B show two different orientations of member 508. Needle guide 502 is attached to second member 508. Needle guide 502 holds the needle firmly in slot 512 of a split-bush. Needle guide 502 also has a needle release knob. After the needle has been inserted into the patient's body 108, the needle release knob is actuated to release the needle. This can be done manually. FIGs 5A and 5B show needle guide 502 in closed (gripped) and release positions respectively. As the needle release knob is actuated, it releases the needle from the guide manipulator 302.
The rotational motion about axes 506 and 510 helps in orienting needle guide 502 along the computed direction vector 212. This enables the surgeon to precisely insert the needle through second member 508 along the computed position vector to reach the point of target. This obviates the need for repeated incision in the patient's body 108 to reach the target.
FIG 6 is a schematic of the controller 306 in accordance with an embodiment of the invention. Controller 306 has a directional vector computer 602 and a means for actuating 604. Directional vector computer 602 determines the linear position of clamp 402, and the angular position of positioning element 404. Directional vector computer 602 computes the spatial orientation of needle guide 502 from point of target 206 and point of insertion 202. In particular, directional vector computer 602 determines the linear position (x, y, z) and the angular position (α, β) for apparatus 102. Details of the algorithm used in directional vector computer 602 are discussed in conjunction with FIG 7. Means for actuating 604 actuates motors 606-614. Motors 606-614 move the arms of guide manipulator 302 to align them in accordance with computed spatial orientation of guide manipulator 302 with help of the encoders 616 - 624. Encoders provide feedback to controller 306 on the precise degree of movement of clamp 402 and positioning element 404. In particular, motors 606-614 provide the linear movement of clamp 402 in the x, y and z axis, and the angular movement of positioning element 404 along the two rotational axes. It must be apparent to one skilled in the art that although five motors have been shown in FIG. 6, there can be fewer than or more than five motors to execute the apparatus without deviating from the scope of the invention.
According to an embodiment of the invention, motors 606-610 move the arms of guide manipulator 302. The movement of cradle 106 on which the patient is placed, is controlled manually on the CT-machine. The precise distances required for the cradle movement are provided by controller 306. The resulting motion of cradle 106 and arms of guide manipulator causes needle guide to be aligned in accordance with spatial orientation computed with help of encoders 616 - 624. Encoders provide feedback to controller 306 on the precise degree of movement of clamp 402 and positioning element 404. In particular, motors 606-612 provide the linear movement of clamp 402 in the x- axis and y-axis, and also angular movement of positioning element 404 along the two rotational axes. According to present embodiment of the invention, the system includes the cradle movement for only Z-axis. However, it would be apparent to a person skilled in the art that cradle 106 is also capable of movement in Y-axis, It must be apparent to one skilled in the art that although three motors have been described in the present embodiment of the invention, there may be fewer than or more than five motors in the apparatus without deviating from the scope of the invention.
FIG 7 is a schematic of Data input means 304 in accordance with an embodiment of the invention. Data input means 304 has a User Interface 702, and an image receiver 704. User Interface (Ul) 702 provides for input of various movement coordinates for apparatus 102. Ul 702 also displays the current position of each axis after positioning using feedback mechanism. Image receiver 704 acquires DICOM images from CT system 104. Ul 702 displays the received DICOM images. Ul 702 also allows for input of point of target 206 and point of insertion 202 on the DICOM images. Such input can be done by a radiologist, or other medical practitioners. Alternatively, point of target 206 and point of insertion 202 can be determined automatically through the use of advanced image recognition technology. It will be apparent to a person skilled in the art that the point of target 206 and point of insertion 202 may be determined using any other approach without deviating from the scope of the invention.
FIGs 8A, 8B, 8C and 8D are a series of illustrations depicting the computation of direction vector 212 for aligning needle guide 502. In accordance with an embodiment of the invention, the coordinate system used is the Cartesian system. The center of the face of the CT gantry 110 is chosen as gantry zero 808 (origin: x=0, y=0, 2=0) of the coordinate system as shown in FIG. 1. Z-axis of the coordinate system is aligned along the movement of cradle. The direction of Z-axis is as shown in FIG.1. Y-axis of the coordinate system is aligned perpendicular to cradle 106, as shown in FIG. 1. The direction of Y-axis is as shown in FIG. 1. X-axis of the coordinate system is aligned perpendicular to Y-Z plane. The direction of X-axis is as shown in FIG. 1. The coordinates of point of insertion 202 are (x2, y2, z2) and point of target 206 are (x1 , y1 , z1) with respect to gantry zero 808. Fig 8A depicts the initial position of the system. 3antry zero 808 is essentially the x=0, y=0 and z=0 level 802. The CT scan provides ■mage slices of the body at different vertical sections. From the series of image slices, the image slice for point of target 804 (z = z1) and the image slice for point of insertion 806 (z = z2) are identified. Axis 804 is a vertical section of the body at point of target 202 denoted as (x2, y2, z2). Axis 806 is a vertical section of the body at point of insertion 206 denoted as (x1 , y1 , z1 ).
Fig 8B shows the image slices of different sections of the body. A lateral scout view, with the planes of each CT slice indicated, is included in the scanned image. It indicates the z- distance (z-coordi nates) for the frames. It shows the front view of the slices at 804 (z=z1) and 806 (z=z2). Coordinates (x1 , y1 , z1) and (x2, y2, z2) are coordinates seen on the image slices. The spatial coordinates of needle guide 502 is 814 (x3, y3, and z3). This position is offset from the surface of the body of the patient by a dead space 812. A corresponding spatial orientation in the actual patient's body 108 is determined by the following formula:
X value in mm = ((Graphical X - XOffset)/ZoomValue)* pixel-spacing
Y value in mm = ((Graphical Y - YOffset)/Zoom Value)* pixel-spacing
Z value in mm = slice-location from DICOM header. This distance is further adjusted with respect to Gantry zero.
Where,
Graphical X = x1 , or x2, or x3
Graphical Y = y1 , or y2, or y3
Graphical Z =z1 , or z2, or z3
In the above formula, XOffset and YOffset are the offsets introduced in x and y values due to the rectangular nature of the user interface. Zoom value indicates the magnification value. It is the ratio of the size of the image displayed on the screen to the actual size of the image.
Pixel spacing is the spacing between the pixels on the Ul. The pixel spacing depends upon the size of the screen and the number of pixels that are present on the screen area.
After computing the coordinates for point of insertion 202 and point of target 206 in real environment, the distance between the two points is determined using the distance formula d = V ( ΔX2 +ΔY2 +ΔZ2) where ΔX, ΔY and ΔZ are the differences in X, Y and Z coordinates of point of target 206 and point of insertion 202, i.e., ΔX = X1 - X2
ΔY = y1 - y2
ΔZ = z1 - z2
Further the orbital angles alpha and beta are determined by alpha = atan (ydiff/xdiff) beta = atan (zdiff/ydiff) where the angles alpha and beta are as shown in FIG 8C.
These angles determine the rotational values by which member 504 and member508 must be rotated so as to align needle guide 502 along direction vector 212.
Needle slot 512 is positioned at 814 with coordinates (x3, y3, z3). This can be either offset value given or can also be the full needle length so as to facilitate the complete insertion of the needle touches the target point. The guide manipulator 302 which is docked to the docking system is thus at a known distance from the gantry zero 808. The needle pointer is placed at a distance equal to dead space 812 from point of insertion 202 determined. Hence the coordinates are adjusted for the dead space 812 using x3, y3 = x2, y2+ Dead space 812
Further, the movement of the platform along the z-axis is computed using the z- coordinate of point of insertion 202 (Z=Z1) and the position of the docking platform Z=Zm. The movement of the platform is the distance required by the platform to align needle guide 502 to the z-coordinate of the point of insertion. It is precisely equal to Z1+Zm.
This distance is calculated by controller 306 and is communicated to cradle 106 as discussed in conjunction with FIGs 9A and 9B.
In an embodiment of the invention, guide manipulator 302 positions itself in such a way that the only a pre-determined portion of the needle is inserted into the body. This is done by determining the length of the needle to be used and the distance between point of target 206 and point of insertion 202. The doctor then chooses the dead space 812, which is communicated, to controller 306. Controller 306 computes coordinates 814 (x3, y3, z3) and hence the three coordinates, viz. point of insertion 202, point of target 206 and the location of the needle guide 502, are determined.
Although the above description of the computation of the direction vector 212 is shown in Cartesian coordinates system, it must be apparent to a person skilled in the art that any other coordinate system can be used without deviating from the scope of the invention. For example, point of insertion 202 and point of target 206 can be determined"and expressed in coordinate systems like Cartesian, Polar, Spherical, curvilinear and the like or in a combination of one or more of these coordinate systems.
FIGs 9A and 9B illustrates a flowchart for the method of positioning a needle guide 502 in accordance with an embodiment of the invention. According to the embodiment of the invention, guide manipulator 302 is firmly docked to the docking plate on the floor surface. The location coordinates of guide manipulator 302 with respect to the gantry center along with the needle guide are stored in the processor memory at the time of installation of apparatus 102. At step 902, the coordinates of the cradle 106 are set to zero. Cradle coordinates or the coordinates of the cradle are the coordinates of a reference point on the cradle with respect to the gantry center. This is done by moving the region of interest of the patient into gantry 110. The region of interest is the area around which the lesion is expected to be present. At step 904, a scout view of the region of interest is taken. At step 906 a skin level sensor is clipped on the cradle at the identified region away from the scan range. Details of the skin level sensor are discussed in conjunction with FIG 10. The skin surface position at the time of the scan is marked through the use of the breath level sensor at step 908. This is done by asking the patient to hold breath during the time of the scan. At step 910, the point of insertion 202 and the point of target 206 are identified. This is done by acquiring the CT image slices into the system using a DICOM interface. In an embodiment of the invention, the points of insertion and the point of target are identified manually through a User Interface (Ul) console by a medical practitioner, such as a doctor, radiologist and the like. Alternatively, the point of insertion and the point of target can be determined automatically through the use of image recognition technology. It must be apparent to a person skilled in the art that any other method can be used to determine the point of insertion and the point of target, without deviating from the scope of the invention.
At step 912, the linear and angular displacement values for guide manipulator 302 and cradle 106 are computed. Thus, the precise coordinates for the motion of cradle 106 in z direction is determined. The coordinates x, y and z, and the angles α and β are computed by controller 306. At step 914, the X, Y, α and β coordinates are communicated to guide manipulator 302. In an embodiment of the invention, this communication is achieved through an RS 232 or any other data communication interface. At step 916, the precise motion details are fed manually on the CT-machine which causes cradle 106 to move along the computed and z distances. It would be apparent to a person skilled in the art that y-motion is also possible by the cradle -movement. At step 918, guide manipulator 302 moves along the computed x and y distance and needle guide 502 rotates by computed angles (α, β). The motions of cradle 106 and guide manipulator 302 in conjunction with the rotations of needle guide 502 by angles α and β positions the needle guide at the desired orientation.
Once needle guide 502 has been positioned, it can be used for conducting a biopsy procedure. A first set of co-ordinates are communicated to position the guide manipulator 302 at a predefined height and to point a laser light to make an incision on the patient's body 108 at the needle entry point. The doctor makes an incision at the point of laser light. After this, a 'position for Biopsy' button is pressed in the guide manipulator 302. Thereafter, the next set of coordinates is communicated to position needle guide 502 close to the patient's body 108. Skin surface position of the patient's body is monitored in the breath sensor console and the patient is asked to hold breath at that position. The doctor inserts the needle to the depth indicated in the Ul console or to the full length based on the option selected when analyzing the image slice for marking the points of insertion 202 and the point of target 206. The needle release knob is actuated and the needle is made free from the guide manipulator 302. A check scan is performed to confirm the position of the needle. In an embodiment of the invention controller 306 allows the practitioner to visualize the needle trajectory in the images. The Check scan data from the CT system is acquired and the simulated versus actual position of needle and the line of the needle is shown. Thereafter the doctor checks to confirm the position of the needle tip. If the position is found to be correct, then the biopsy procedure is performed.
FIG 10 illustrates a skin level sensor for providing correction to the spatial orientation of needle guide 502, in accordance with another embodiment of the invention. The skin level sensor can be a breath sensor. A breath sensor 1002 is placed on abdomen 1004 of the patient. Breath sensor 1002 is attached to cradle 1008 of CT table 1010 through cradle clip 1012. A breath level indicator 1014 is attached to breath sensor 1002. Breath level indicator 1012 has a freeze key 1016 for capturing the position of abdomen 1004 at the point of the CT imaging.
The patient is asked to hold breath just before the initial target identification scan. Breath level indicator 1012 shows a bar graph and the doctor freezes the position of the skin level at the time of taking the scan. This freeze point is indicated as graph 1018. The patient scan is taken and then the patient is allowed to breathe normally. After positioning the needle guide, and just before the needle is inserted into the patient, the^patient is asked to hold the breath again. Breath level indicator 1014 indicates the level of the skin in graph 1020. The needle insertion procedure is conducted as long as graph 1020 remains in the tolerance zone of graph 1018. If before needle insertion, the patient releases the breath hold such that graph 1020 moves outside of the tolerance zone, there is an audio alert and the patient is asked to hold the breath again.
In an embodiment of the present invention, a plane level indicator is provided at the base of guide manipulator 302 to account for any non-planar nature of the surface of mounting of the guide manipulator 302.
Controller 306 and data input means 304, as described in the current invention or any of its components, may be embodied in the form of a processing machine. Typical examples of a processing machine include a computer, a programmed microprocessor, an integrated circuit, and other devices or arrangements of devices that are capable of implementing the steps of the method of the current invention.
The processing machine executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also hold data or other information as desired. The storage element may be in the form of an information destination or a physical memory element present in the processing machine.
The, set of instructions may include various commands that instruct the processing machine to perform specific tasks such as the steps that constitute the method of the present invention. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software might be in the form of a collection of separate programs, a program module with a larger program or a portion of a program module. The software might also include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing or in response to a request made by another processing machine.
A person skilled in the art can appreciate that the various processing machines and/or storage elements may not be physically located in the same geographical location. The processing machines and/or storage elements may be located in geographically distinct locations and connected to each other to enable communication. Various communication technologies may be used to enable communication between the processing machines and/or storage elements. Such technologies include session of the processing machines and/or storage elements, in the form of a network. The network can be an intranet, an extranet, the Internet or any client server models that enable communication. Such communication technologies may use various protocols such as TCP/IP, UDP, ATM or OSI.
While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the claim.