Insertable surgical imaging device with pan, tilt, zoom, and lighting

Tie Hu, Peter K. Allen, Nancy J. Hogle and Dennis L. Fowler

Abstract—This paper describes work we have done in de­veloping an insertable surgical imaging device with multiple degrees-of-freedom for minimally invasive surgery. The device is fully insertable into the abdomen using standard 12mm trocars. It consists of a modular camera and lens system which has pan and tilt capability provided by 2 small DC servo motors. It also has its own integrated lighting system that is part of the camera assembly. Once the camera is inserted into the abdomen, the insertion port is available for additional tooling, motivating the idea of single port surgery. A third zoom axis has been designed for the camera as well, allowing close-up and far-away imaging of surgical sites with a single camera unit.

In animal tests with the device we have performed surgical procedures including cholecystectomy, appendectomy, running (measuring) the bowel, suturing, and nephrectomy. The tests show that the new device is:

Easier and more intuitive to use than a standard laparoscope.

Joystick operation requires no specialized operator train­ing.

Field of view and access to relevant regions of the body were superior to a standard laparoscope using a single port.

Time to perform procedures was better or equivalent to a standard laparoscope.

We believe these insertable platforms will be an integral part of future surgical systems. The platforms can be used with tooling as well as imaging systems, allowing many surgical procedures to be done using such a platform.

I. Introduction

Minimally Invasive Surgery (MIS) encompasses la-paroscopy, thoracoscopy, arthroscopy, intraluminal en-doscopy, endovascular techniques, catheter-based cardiac techniques, and interventional radiology[2], and has grown rapidly over the last two decades. In 1992, 70% of all cholecystectomies (gall bladder removal) in the United States, Europe, and Japan were performed using laparoscopic techniques [1]. In laparoscopic surgery, the surgeon first cuts several small incisions in the abdomen, and inserts trocars (small tubes) through the incisions. Carbon dioxide gas is pumped into the abdomen to create a larger volume of space for the operation and visualization. By viewing the image from the laparoscope which is inserted into the body through the trocar, the surgeon operates the laparoscopic tools to perform surgery. Laparoscopic surgery has many benefits, such as small incisions, less pain and trauma to the patients, faster recovery time, and lower health care cost. However, this technique drastically increases the complexity of a surgeons' task because of the rigid, sticklike instruments, impaired depth perception, loss of sense of touch (haptics) and the difficulty in varying the perspective view of the operative field[1].

Robotic surgery is considered as the future of surgery[13]. Robots for MIS could greatly increase the dexterity and fine motion capabilities of a surgeon during an operation, decrease the tremor of a surgeon's hand, and enable re­mote operation[12], [18], [11], [9], [7]. Robotic surgery still comprises only a very small portion of all minimally invasive surgery. Current surgical robots tend to be extremely expensive with the price of a da Vinci robot (Intuitive Surgical) being typically over a million dollars. In addition, the size of many current surgical robots is extremely large, tending to occupy a large portion of the sterile field of an operating room.

There is a definite need to develop a surgical robot which is more compact and less expensive than existing systems. Our goal is to enhance and improve surgical procedures by placing small, mobile, multi-function platforms inside the body that can begin to assume some of the tasks associated with surgery. We want to create a feedback loop between new, insertable sensor technology and effectors we are devel­oping, with both surgeons and computers in the information-processing/control loop. We envision surgery in the future as radically different from today. This is clearly a trend that has been well-established as minimal-access surgical procedures continue to expand. Accompanying this expansion have been new thrusts in computer and robotic technologies that make automated surgery, if not feasible, an approachable goal. It is not difficult to foresee teams of insertable robots perform­ing surgical tasks inside the body under both surgeon and computer control. The benefits of such an approach are well documented: greater precision, less trauma to the patient, and improved outcomes. One factor limiting this expansion is that the laparoscopic paradigm of pushing long sticks into small openings is still the state-of-the-art, even among surgical robots such as DaVinci. While this paradigm has been enormously successful, and has spurred development of new methods and devices, it is ultimately limiting in what it can achieve. Our intent is to go beyond this paradigm, and remotize sensors and effectors into the body cavity where they can perform surgical and imaging tasks unfettered by traditional endoscopic instrument design.

[Some details are omitted]

We have been focusing on developing an inexpensive, insertable endoscopic camera with multiple degrees-of-freedoms (DOFs). In this paper, we describe our insertable Pan/Tilt endoscope with integrated light source that we have built and and tested in five in vivo animal tests. Surgeons have used this device to perform laparoscopic appendectomy, cholecystectomy, running (measuring) the bowel, suturing, and nephrectomy. The results show that the device is easier to use and control than a standard laparoscope. Our imaging device only requires a single access port and has more flexibility, as it is inside the body cavity and can obtain images from a number of controllable directions. There is no need for extensive training with this device as with a standard laparoscope since it is operated by a simple joystick. Standard laparoscopes have counter-intuitive motions due to the pivoting about the insertion point (e.g. to move the laparoscope to the right, the external part of the unit is moved to the left, pivoting on the insertion point). This can cause confusion for untrained operators. Our device can image a larger field of view than traditional laparoscopes, allowing the surgeon greater flexibility in seeing the inside of the abdominal cavity. Our tests have also shown that zooming capabilities are desirable for such a device, and we also present a design for a zooming capability that will add an extra DOF to our device, extending its utility during surgery.

II. Prototype Device

A. New Prototype Imaging Device

Our initial work [24] in designing such an imaging system created a device with 2 cameras and 5-DOF (independent pan and translation axes for each of two cameras plus a common tilt axis). A single camera, 3-DOF version was successfully tested with surgical fellows in a laparoscopic trainer mockup. These quantitative tests using the MISTELS (McGill Inanimate System for the Training and Evaluation of Laparoscopic Skill) tasks [28] showed the device was able to carry out typical minimally invasive surgical tasks equivalent to using a standard laparoscope, with no loss of function[25]. Based upon this design, we have designed a second generation device that improves upon the design of our initial device described above. Our design goals for the new prototype included reducing the device size (from 22mm to 11mm in diameter) and the inclusion of an integrated light source. To reduce the device size to allow it to be inserted through a 12mm trocar, we removed 1 camera and the translation axis. We have also added an LED light source to the device[14]. The total length of the device is about 110mm, and the diameter is about 1 1mm and can be inserted into a standard 12mm trocar.

We make use of modular design to make the device components interchangeable and extendable. The current system includes a user-friendly interface, making it easier to control the camera's DOF using natural motions. It consists of a Pan/Tilt motorized CCD camera with illumination com­ponents, control interface driver, PC, and Joystick controller. After the surgeon anchors the camera onto the abdomen wall, he can use the Joystick to position the camera to the desired surgical viewpoint using the Pan and Tilt motions. The intensity of illumination can be adjusted manually through the control panel. Figure 1 shows images of the implemented prototype device, with integrated lighting and pan/tilt axes.

[Some details are omitted]

B. Zoom Mechanism

[Some details are omitted]

Our zoom mechanism is designed to manipulate the cam­era forward and backward. A rack and pinion mechanism was chosen as the basic mechanical structure for zooming to achieve a compact size (Side View of Figure 3). A 4.5mm miniature stepper motor (0.08mNm maximum torque) is used as the actuator to drive the pinion. The zooming distance is 20mm. The entire zoom package is 12 mm in diameter and 56mm in length. Figure 3 shows the CAD model of the zoom mechanism. It is constructed of a camera module, zoom components and an external shell. To maximize the output torque, 3 sets of gears are used in the design. The 1st gear is a spur gear with 120 Diametral Pitch and 40 teeth. It rotates on a rack, which is mounted on a support which is attached to the external shell. When the motor rotates, the pinion gear travels along the rack, moving the camera module forward and backward along the external shell. A pinion with 120 Diametral Pitch and 12 teeth is matched with 1st gear. 2nd gear(120 Diametral Pitch, 30 teeth) is mounted on the same shaft with this pinion. A pinion with 120 Diametral Pitch and 12 teeth is mounted on the same shaft as the worm. This pinion is matched with 2nd gear. The worm is mounted on the shaft of motor. The ratio of worm gear is 16:1. Finally, we get a total speed reduction of 133:1 with this design, which we are currently testing in animal trials.