Patrick Cheng

OpenIGTLink: an open network protocol for image-guided therapy environment

With increasing research on system integration for image‐guided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status.

The Image-Guided Surgery Toolkit IGSTK: An Open Source C++ Software Toolkit

This paper presents an overview of the image-guided surgery toolkit (IGSTK). IGSTK is an open source C++ software library that provides the basic components needed to develop image-guided surgery applications. It is intended for fast prototyping and development of image-guided surgery applications. The toolkit was developed through a collaboration between academic and industry partners. Because IGSTK was designed for safety-critical applications, the development team has adopted lightweight software processes that emphasizes safety and robustness while, at the same time, supporting geographically separated developers. A software process that is philosophically similar to agile software methods was adopted emphasizing iterative, incremental, and test-driven development principles. The guiding principle in the architecture design of IGSTK is patient safety. The IGSTK team implemented a component-based architecture and used state machine software design methodologies to improve the reliability and safety of the components. Every IGSTK component has a well-defined set of features that are governed by state machines. The state machine ensures that the component is always in a valid state and that all state transitions are valid and meaningful. Realizing that the continued success and viability of an open source toolkit depends on a strong user community, the IGSTK team is following several key strategies to build an active user community. These include maintaining a users and developers’ mailing list, providing documentation (application programming interface reference document and book), presenting demonstration applications, and delivering tutorial sessions at relevant scientific conferences.

Needle-Based Interventions With the Image-Guided Surgery Toolkit (IGSTK): From Phantoms to Clinical Trials

We present three image-guided navigation systems developed for needle-based interventional radiology procedures, using the open source image-guided surgery toolkit (IGSTK). The clinical procedures we address are vertebroplasty, RF ablation of large lung tumors, and lung biopsy. In vertebroplasty, our system replaces the use of fluoroscopy, reducing radiation exposure to patient and physician. We evaluate this system using a custom phantom and compare the results obtained by a medical student, an interventional radiology fellow, and an attending physician. In RF ablation of large lung tumors, our system provides an automated interventional plan that minimizes damage to healthy tissue and avoids critical structures, in addition to accurate guidance of multiple electrode insertions. We evaluate the systems performance using an animal model. Finally, in the lung biopsy procedure, our system replaces the use of computed tomographic (CT) fluoroscopy, reducing radiation exposure to patient and physician, while at the same time enabling oblique trajectories which are considered challenging under CT fluoroscopy. This system is currently being used in an ongoing clinical trial at Georgetown University Hospital and was used in three cases.

Agile methods for open source safety-critical software

The introduction of software technology in a life‐dependent environment requires the development team to execute a process that ensures a high level of software reliability and correctness. Despite their popularity, agile methods are generally assumed to be inappropriate as a process family in these environments due to their lack of emphasis on documentation, traceability, and other formal techniques. Agile methods, notably Scrum, favor empirical process control, or small constant adjustments in a tight feedback loop. This paper challenges the assumption that agile methods are inappropriate for safety‐critical software development. Agile methods are flexible enough to encourage the right amount of ceremony; therefore if safety‐critical systems require greater emphasis on activities, such as formal specification and requirements management, then an agile process will include these as necessary activities. Furthermore, agile methods focus more on continuous process management and code‐level quality than classic software engineering process models. We present our experiences on the image‐guided surgical toolkit (IGSTK) project as a backdrop. IGSTK is an open source software project employing agile practices since 2004. We started with the assumption that a lighter process is better, focused on evolving code, and only adding process elements as the need arose. IGSTK has been adopted by teaching hospitals and research labs, and used for clinical trials. Agile methods have matured since the academic community suggested almost a decade ago that they were not suitable for safety‐critical systems; we present our experiences as a case study for renewing the discussion. Copyright

Radiofrequency ablation of lung tumors in swine assisted by a navigation device with preprocedural volumetric planning.

PURPOSE To develop an image guidance system that incorporates volumetric planning of spherical ablations and electromagnetic tracking of radiofrequency (RF) electrodes during insertion. MATERIALS AND METHODS Simulated tumors were created in three live swine by percutaneously injecting agar nodules into the lung. A treatment plan was devised for each tumor with optimization software to solve the planning problem. The desired output was the minimum number of overlapping ablation spheres necessary to ablate each tumor and the margin. The insertion plan was executed with use of the electromagnetic tracking system that guided the insertion of the probe into precomputed locations. After a 72-hour survival period, animals were killed and histopathologic sections of the tissue were examined for cell viability and burn pattern analysis. RESULTS A planning algorithm to spherically cover the tumors and the margin was computed. Electromagnetic tracking allowed successful insertion of the instrument, and impedance roll-off was reached in all ablations. Depending on their size, the tumors and the tumor margins were successfully covered with two to four ablation spheres. The image registration error was 1.0 mm +/- 0.64. The overall error of probe insertion was 9.4 mm +/- 3.0 (N = 8). Analysis of histopathologic sections confirmed successful ablations of the tissue. CONCLUSIONS Computer-assisted RF ablation planning and electromagnetically tracked probe insertion were successful in three swine, validating the feasibility of electromagnetic tracking-assisted tumor targeting. Image misregistration caused by respiratory motion and tissue deformation contributed to the overall error of probe insertion.

Designing tracking software for image-guided surgery applications: IGSTK experience

ObjectiveMany image-guided surgery applications require tracking devices as part of their core functionality. The Image-Guided Surgery Toolkit (IGSTK) was designed and developed to interface tracking devices with software applications incorporating medical images.MethodsIGSTK was designed as an open source C++ library that provides the basic components needed for fast prototyping and development of image-guided surgery applications. This library follows a component-based architecture with several components designed for specific sets of image-guided surgery functions. At the core of the toolkit is the tracker component that handles communication between a control computer and navigation device to gather pose measurements of surgical instruments present in the surgical scene. The representations of the tracked instruments are superimposed on anatomical images to provide visual feedback to the clinician during surgical procedures.ResultsThe initial version of the IGSTK toolkit has been released in the public domain and several trackers are supported. The toolkit and related information are available at http://www.igstk.org.ConclusionWith the increased popularity of minimally invasive procedures in health care, several tracking devices have been developed for medical applications. Designing and implementing high-quality and safe software to handle these different types of trackers in a common framework is a challenging task. It requires establishing key software design principles that emphasize abstraction, extensibility, reusability, fault-tolerance, and portability. IGSTK is an open source library that satisfies these needs for the image-guided surgery community.

Interfacing proprietary hardware with the image-guided surgery toolkit (IGSTK): a case for the OpenIGTLink protocol

One of the key technical challenges in developing an extensible image-guided navigation system is that of interfacing with external proprietary hardware. The technical challenges arise from the constraints placed on the navigation systems hardware and software. Extending a navigation systems functionality by interfacing with an external hardware device may require modifications to internal hardware components. In some cases, it would also require porting the complete code to a different operating system that is compatible with the manufacturer supplied application programming interface libraries and drivers. In this paper we describe our experience extending a multi-platform navigation system, implemented using the image-guided surgery toolkit IGSTK, to support real-time acquisition of 2-D ultrasound (US) images acquired with the Terason portable US system. We describe the required hardware and software modifications imposed by the proposed extension and how the OpenIGTLink network communication protocol enabled us to minimize the changes to the systems hardware and software. The resulting navigation system retains its platform independence with the added capability for real-time image acquisition independent of the image source.

Accuracy Analysis of an Image-Guided System for Vertebroplasty Spinal Therapy based on Electromagnetic Tracking of Instruments

Vertebroplasty is a minimally invasive procedure in which bone cement is pumped into a fractured vertebral body that has been weakened by osteoporosis, long-term steroid use, or cancer. In this therapy, a trocar (large bore hollow needle) is inserted through the pedicle of the vertebral body which is a narrow passage and requires great skill on the part of the physician to avoid going outside of the pathway. In clinical practice, this procedure is typically done using 2D X-ray fluoroscopy. To investigate the feasibility of providing 3D image guidance, we developed an image-guided system based on electromagnetic tracking and our open source software platform the Image-Guided Surgery Toolkit (IGSTK). The system includes path planning, interactive 3D navigation, and dynamic referencing. This paper will describe the system and our initial evaluation.

Integration of a real-time video grabber component with the open source image-guided surgery toolkit IGSTK

The image-guided surgery toolkit (IGSTK) is an open source C++ library that provides the basic components required for developing image-guided surgery applications. While the initial version of the toolkit has been released, some additional functionalities are required for certain applications. With increasing demand for real-time intraoperative image data in image-guided surgery systems, we are adding a video grabber component to IGSTK to access intraoperative imaging data such as video streams. Intraoperative data could be acquired from real-time imaging modalities such as ultrasound or endoscopic cameras. The acquired image could be displayed as a single slice in a 2D window or integrated in a 3D scene. For accurate display of the intraoperative image relative to the patients preoperative image, proper interaction and synchronization with IGSTKs tracker and other components is necessary. Several issues must be considered during the design phase: 1) Functions of the video grabber component 2) Interaction of the video grabber component with existing and future IGSTK components; and 3) Layout of the state machine in the video grabber component. This paper describes the video grabber component design and presents example applications using the video grabber component.

A Lightweight App Distribution Strategy to Generate Interest in Complex Commercial Apps: Case Study of an Automated Wound Measurement System

Tablet-based healthcare technologies automating clinical triage procedures hold exciting promise for increased precision and expediency. These point-ofcare (POC) solutions are often complex, and their introduction to the marketplace may encounter cost and usability barriers. One example triage procedure is wound measurement. This paper demonstrates an innovative approach to POC wound measurement by introducing a free “light” version of a wound measurement mobile app that serves as a teaser for a full-featured commercial offering. We first describe the commercial offering; a 3D wound assessment tablet application. Then we present the smartphone app that inherits features from the tablet app. The smartphone app adopts a simple scaling algorithm to address the lack of a highly advanced computer vision system for the automated wound measurement task that exists in the tablet app. This paper describes the design process for developing this smartphone app, provides a detailed exposition of the scaling algorithm, and discusses the significance of this approach to app development and distribution.