Ray A. Lathrop

Minimally Invasive Holographic Surface Scanning for Soft-Tissue Image Registration

Recent advances in registration have extended intrasurgical image guidance from its origins in bone-based procedures to new applications in soft tissues, thus enabling visualization of spatial relationships between surgical instruments and subsurface structures before incisions begin. Preoperative images are generally registered to soft tissues through aligning segmented volumetric image data with an intraoperatively sensed cloud of organ surface points. However, there is currently no viable noncontact minimally invasive scanning technology that can collect these points through a single laparoscopic port, which limits wider adoption of soft-tissue image guidance. In this paper, we describe a system based on conoscopic holography that is capable of minimally invasive surface scanning. We present the results of several validation experiments scanning ex vivo biological and phantom tissues with a system consisting of a tracked, off-the-shelf, relatively inexpensive conoscopic holography unit. These experiments indicate that conoscopic holography is suitable for use with biological tissues, and can provide surface scans of comparable quality to existing clinically used laser range scanning systems that require open surgery. We demonstrate experimentally that conoscopic holography can be used to guide a surgical needle to desired subsurface targets with an average tip error of less than 3 mm.

A study on the theoretical and practical accuracy of conoscopic holography-based surface measurements: toward image registration in minimally invasive surgery.

Registered medical images can assist with surgical navigation and enable image‐guided therapy delivery. In soft tissues, surface‐based registration is often used and can be facilitated by laser surface scanning. Tracked conoscopic holography (which provides distance measurements) has been recently proposed as a minimally invasive way to obtain surface scans. Moving this technique from concept to clinical use requires a rigorous accuracy evaluation, which is the purpose of our paper.

Guidance of a steerable cannula robot in soft tissue using preoperative imaging and conoscopic surface contour sensing

Intraoperative surface contour sensing can enable the registration of high-resolution three-dimensional preoperative images for precise guidance of surgical robots. This is particularly useful for guiding steerable needles in soft tissues. In this paper we combine a new minimally invasive surface scanning technique based on conoscopic holography with a steerable active cannula robot. We experimentally demonstrate cannula tip placement to multiple physical points inside phantom tissue, which correspond to points specified in preoperative images - the input an eventual clinical system would obtain from the physician. While the image-guided steerable system we propose is broadly applicable to many kinds of surgery, one particular application of interest is in ablating large liver tumors, where it is beneficial for the ablator to be repositioned to multiple locations without being withdrawn from the organ.

Minimally-invasive intracerebral hemorrhage removal using an active cannula

The high incidence of intracerebral hemorrhages, together with a 40% mortality rate, provide strong motivation for enhancements in the treatment methods available to physicians. To minimize the disruption to healthy brain tissue associated with gaining access to the surgical site that is imposed by traditional open or endoscopic surgical intervention, we propose a new minimally-invasive, image-guided, robotic approach that provides articulation within the lesion at the tip of a needle. In this paper we present a biocompatible and sterilizable robot, together with an image-guidance approach designed to deliver the tip of the needle accurately to the blood clot and to move it within the clot, to aspirate it. An experimental evaluation demonstrates removal of 92% of the target clot tissue in a proof-of-concept phantom study.

Robot-assisted intracerebral hemorrhage evacuation: an experimental evaluation

We present a novel robotic approach for the rapid, minimally invasive treatment of Intracerebral Hemorrhage (ICH), in which a hematoma or blood clot arises in the brain parenchyma. We present a custom image-guided robot system that delivers a steerable cannula into the lesion and aspirates it from the inside. The steerable cannula consists of an initial straight tube delivered in a manner similar to image-guided biopsy (and which uses a commercial image guidance system), followed by the sequential deployment of multiple individual precurved elastic tubes. Rather than deploying the tubes simultaneously, as has been done in nearly all prior studies, we deploy the tubes one at a time, using a compilation of their individual workspaces to reach desired points inside the lesion. This represents a new paradigm in active cannula research, defining a novel procedure-planning problem. A design that solves this problem can potentially save many lives by enabling brain decompression both more rapidly and less invasively than is possible through the traditional open surgery approach. Experimental results include a comparison of the simulated and actual workspaces of the prototype robot, and an accuracy evaluation of the system.

Design of a Stiff Steerable Grasper for Sinus Surgery

With the advent of endoscopic sinus surgery in the late 1980’s [1], a completely new surgical field was born. The endoscope, passed through the natural orifice of the nose, allowed for much more precise visualization of the operative field and enabled a new understanding of the function of the sinuses. Today, functional endoscopic sinus surgery (FESS) is commonly used to improve the sinuses’ natural drainage pathways in patients with chronic sinusitis, to remove pathologies such as nasal polyps and tumors, and even to access the skull base to remove brain tumors. Commonly used angled endoscopes allow for visualization of nearly every portion of the sinus cavities and skull base. However, traditional tools have not enabled adequate surgical access to all of these areas. This is because the current surgical method requires a nearly direct line of access from the opening of the nose to the surgical target. Due to anatomical obstacles, not all areas visible to the endoscope can be directly accessed in this way. As a result, procedures have been developed to remove anatomical structures in order to clear a direct line of access to hard-to-reach targets. However, removal of these structures comes at a cost, with complications including vascular, nerve and soft tissue damage that can result in pain or numbness in the mouth and face. Current technique requires one hand to hold the surgical instrument, while the other hand is typically occupied holding the endoscope, as shown in Figure 1. Generally these tools are supported entirely by the surgeon’s hands, in contrast with other types of laparoscopic surgery in which a trocar provides additional support. As a result, tools must be lightweight and comfortable to hold. These tools have traditionally been designed to be rigid (so as to be easily controlled with one hand), though not necessarily straight. In an attempt to reach around corners and avoid obstacles in the anatomy, some devices incorporate curved tool shafts. However, these are limited in their maneuverability, since the curved shape is fixed during surgery. These rigid tools have been adequate for the majority of surgeries, but as techniques have advanced, surgeons have reached the limits of what they can accomplish with these tools. In order to avoid the need to remove tissue in order to access hard-to-reach sites, new tools must be developed which are capable of navigating through angled pathways in the nasal cavities. A new approach to this problem involving a stiff yet elastic steerable tool tip is presented in this paper. This approach uses a continuum structure. For a review of prior uses of continuum structures in robotic tools, see [2]. Figure 1: Placement of an endoscope and a traditional rigid grasper tool during endonasal surgery. One hand (not pictured) holds the endoscope, while the other (pictured) holds the rigid grasper.

Design of an Endonasal Graft Placement Tool for Repair of Skull Base Defects

Poor tools lead to dropped gra7s, decreased surgeon confidence, increased opera<ng <me Forceps: • cannot reliably open and close in 6ght spaces • good grip • poor force applica6on Blunt Tools: • good force applica6on • poor grip • difficulty handling varying gra: size, shape, rigidity Endonasal Approach • Minimally invasive • Limited tool manipulability • Gra: placement can add up to 30 minutes Inadequate Gra7 Placement Complica<ons • CSF leaks that lead to meningi6s, brain hemorrhage, neurological deficits, or death1

Conoscopic holography for image registration: a feasibility study

Preoperative image data can facilitate intrasurgical guidance by revealing interior features of opaque tissues, provided image data can be accurately registered to the physical patient. Registration is challenging in organs that are deformable and lack features suitable for use as alignment fiducials (e.g. liver, kidneys, etc.). However, provided intraoperative sensing of surface contours can be accomplished, a variety of rigid and deformable 3D surface registration techniques become applicable. In this paper, we evaluate the feasibility of conoscopic holography as a new method to sense organ surface shape. We also describe potential advantages of conoscopic holography, including the promise of replacing open surgery with a laparoscopic approach. Our feasibility study investigated use of a tracked off-the-shelf conoscopic holography unit to perform a surface scans on several types of biological and synthetic phantom tissues. After first exploring baseline accuracy and repeatability of distance measurements, we performed a number of surface scan experiments on the phantom and ex vivo tissues with a variety of surface properties and shapes. These indicate that conoscopic holography is capable of generating surface point clouds of at least comparable (and perhaps eventually improved) accuracy in comparison to published experimental laser triangulation-based surface scanning results.

Comparing a Mechanical Analogue With the Da Vinci User Interface: Suturing at Challenging Angles

The da Vinci Surgical System offers a natural user interface and wrist articulation, which enable suturing and other complex surgical actions in confined spaces. However, both the one-time cost of the system and the recurring cost of the limited-use instruments remain high. This has motivated the development of several hand-held alternatives-some partially motorized, some fully mechanical-in recent years. While a few of these have been commercialized, none have yet met with broad commercial success comparable to the da Vinci robot. In this letter, we suggest a user interface-based explanation for this, and describe a new mechanical instrument that provides wrist articulation with a novel user interface. We provide results of a single-user pilot study with an experienced laparoscopic surgeon to compare the new device with a traditional wristless laparoscopic tool, a prior commercial wristed mechanical tool (the RealHand), and the da Vinci robot, in the context of suturing at challenging angles. We observe better targeting of desired suture needle entry and exit points with the new device in comparison to prior wristed and wristless mechanical instruments, with the da Vinci only slightly outperforming the new tool.

Design of a Safer Tracheostomy Tube

During a tracheotomy, the surgeon makes an incision through the front of the patient’s neck (the incision is known as a tracheostomy) to access the trachea and insert a tracheostomy tube (see Figure 1), which serves as an alternative airway to the mouth or nose. After insertion, a balloon is inflated to the diameter of the trachea, which fixes the tracheotomy tube in place, allows for positive pressure ventilation, and creates a seal to the walls of the trachea.