By Andinet Enquobahrie

Image-guided intervention research focuses on the development of innovative technologies that replace traditional surgery and invasive procedures with minimally invasive techniques that incorporate medical imaging to guide the intervention. Patients prefer these procedures to open surgeries because they typically cause less trauma to the body and result in faster recovery times. Technological advancements in medical imaging, registration algorithms, visualization technologies and tracking systems are the driving forces behind increasing adoption of these procedures by physicians.

Software is an integral part of image-guided intervention systems. Whether for interfacing with a tracking device to collect position information from surgical instruments, registering intra-operative with pre-operative images, or generating a 3D visualization to provide visual feedback to the clinician, software plays a critical role. Historically, open source software has enjoyed great success in conventional low-risk applications. In recent years, open source software has made the transition into mission-critical applications, such as image-guided intervention systems.

Why open source reigns

Having an open platform in image-guided intervention systems increases the pace of research and discovery by promoting collaboration between clinicians, biomedical engineers and software developers. One highly successful open-source system is the Image-Guided Surgery Toolkit (IGSTK) ^[1][2]. IGSTK is an open-source platform for developing image-guided therapy systems written in C++. It is free for commercial and non-commercial use. It has been adopted for liver lesion ablation, lung tumor biopsy, and other procedures. The toolkit is an ongoing, collaborative effort between Kitware, an open source research company in Clifton Park, N.Y., and Dr. Kevin Cleary, director of the ISIS Laboratory at Georgetown University. IGSTK is the product of a series of STTR and R01 grants from the NIH that have spanned the past seven years. The toolkit is a powerful set of software components for rapid prototyping and developing image-guided surgery applications.

The development team has adopted lightweight software processes that emphasize safety and robustness while supporting geographically separated developers. These software processes are philosophically similar to agile software methods, with an emphasis on iterative, incremental and test-driven development principles. However, the guiding principle in the software processes and the software architecture of IGSTK is patient safety. For example, IGSTK uses a component-based architecture and state machine software design methodologies to improve the reliability and safety of the components. Furthermore, rigorous software registration testing processes are used to ensure the stability and interoperability of those components.

IGSTK-based applications

An IGSTK-based application which employs electromagnetic field (EM) technology to track biopsy needles is currently in a clinical trial at Georgetown University. IGSTK provides support for needle tracking using a variety of tracking options including EMF and optical cameras. In this EMF-based needle tracking application, the patient is positioned on the CT table, a CT image is acquired and the location of the pathological tissue is identified on the images. During the biopsy procedure, a computer generated representation of the surgical scene is displayed for the physician and continuously updated with the current position and orientation of the biopsy needle based on measures from an EMF sensor attached to the needle. As part of an ongoing clinical trial at Georgetown, the usefulness of IGSTK for precision biopsy of suspicious lung lesions is being quantified. Other applications developed using IGSTK include radiofrequency ablation of liver tumors ^[3], robot-assisted needle placement ^[4], vertebroplasty ^[5], and integrated system for guidance of head and neck surgery ^[6].

The Future

In the future, IGSTK will focus on three main challenging research areas in image-guided therapy, in cooperation with our many partners:

1. Registration algorithms for intraoperative real-time feedback;
2. Ultrasound focused therapy applications;
3. Image-guided drug delivery.

The challenges in developing registration algorithms for image-guided applications are related to tissue deformation and organ motion during minimally invasive procedures. Continued research focuses on fast and robust deformable registration algorithms that take advantage of the recent advances in computing technologies such as the graphics processors on video card ("GPUs").

Ultrasound devices are receiving increased use in therapeutic applications. Focused ultrasound is currently being used to treat uterine fibroids, and to disrupt the blood-brain barrier in order to help cancer drugs reach their targets. Ultrasound-specific, quantitative workstations that interface with ultrasound devices and process ultrasound images during minimally invasive procedures will continue to be the focus of much research as these procedures become more common.

Image-guided drug delivery is the other hot research area. The objective of drug delivery is to increase the concentration of a therapeutic agent in the target tumor while limiting systemic exposure. Increasing the concentration of drugs in the tumor relative to normal tissues results in improved tumor control and reduced toxic side effects. Image guidance can be used in targeting the tumor and in releasing and monitoring the drug to improve the effectiveness of the procedure. In summary, open source software will continue to play a major role in tackling these types of new challenges and advancing the image-guided intervention field by promoting collaborations between clinicians, biomedical engineers, and software developers.

References:

1. "IGSTK: An Open Source C++ Software Library, Second Edition", Cleary K, Cheng P, Enquobahrie A, Yaniv Z. Signature Book Printing, Gaithersburg, Maryland
2. The Image-Guided Surgery Toolkit IGSTK: An Open Source C++ Software Toolkit", A. Enquobahrie and P. Cheng and K. Gary and L. Ibanez and D. Gobbi and F. Lindseth and Z. Yaniv and S. Aylward and J. Jomier and K. Cleary, Journal of Digital Imaging, Vol. 20(Suppl. 1), pp. 21–33, 2007.
3. "Radiofrequency Ablation of Lung Tumors in Swine Assisted by a Navigation Device with Preprocedural Volumetric Planning", Filip Banovac, Patrick Cheng, Enrique Campos-Nanez, Bhaskar Kallakury, Teo Popa, Emmanuel Wilson, Hernan Abeledo, Kevin ClearyJournal of vascular and interventional radiology, JVIR 1 January 2010 (volume 21 issue), pp.122-129
4. "Robot Assisted Needle Placement: Developed Using Image Guided Surgery Toolkit (IGSTK)", P. Cheng, A. Enquobahrie, R. Stenzel, R. Lin, H. Zhang, Z. Yaniv, H. Kim, K. Cleary, Open Source Workshop MICCAI 2006.
5. "Accuracy Analysis of an Image-Guided System for Vertebroplasty therapy based on Electromagnetic Tracking of Instruments", J. Ding, N. Khan, P. Cheng, E. Wilson, V. Watson, K. Cleary, Z. Yaniv, SPIE Medical Imaging: Visualization, Image-Guided Procedures, and Display, 2008
6. "High-Performance Intraoperative Cone-Beam CT on a Mobile C-Arm: An Integrated System for Guidance of Head and Neck Surgery", J. H. Siewerdsen, M. J. Daly, H. Chan, S. Nithiananthan, N. Hamming, K. K. Brock, and J. C. Irishe. Medical Imaging 2009: Visualization, Image-Guided Procedures, and Modeling, edited by Michael I. Miga, Kenneth H. Wong, Proc. of SPIE Vol. 7261.

Andinet Enquobahrie is a research and development engineer at Kitware. He is involved in the development of image visualization and analysis tools for medical applications. He is one of the main developers of the Image Guided Surgery Application (IGSTK) toolkit, a cross platform open source C++ software library that provides basic components needed to prototype image-guided surgery applications.