**1. Introduction**

Minimally invasive and non-invasive image guided therapy can reduce surgical traumas and improve outcome for patients suffering from a wide variety of diseases. It may also reduce hospital stays and costs. Ultrasound is an important intraoperative imaging modality for guidance and monitoring of these therapeutic methods. Ultrasound has emerged as one of the main modalities for medical imaging in healthcare, the main reason being its ability to image soft tissue, blood flow, organ function and physiology with considerably improved image quality. Furthermore, ultrasound has the unique advantages of real time imaging, equipment portability, safety, and low costs. Ultrasound is now facing a paradigm shift in technology and clinical usability over the coming 10 years. The future potential will be released through exploration in knowledge and innovation deliveries in transducer arrays, ultrasound elec‐ tronics, software beam forming, parallel imaging and compressed sensing, minimum diffrac‐ tive wave imaging, model powered acquisition and new technology for a wide range of methods related to physiology, tissue properties and organ function in real time and on site. High-frequency ultrasound imaging makes it possible to obtain significantly improved spatial resolution, however, with limitations related to how deep into the tissue the imaging can be performed. In many image-guided surgery and therapy applications, ultrasound is performed with probes placed directly on the tissue and organ of interest (e.g. intravascular ultrasound, open chest cardiac surgery, esophagus probes for cardiac imaging, probes dedicated to surgery of pituitary gland). These applications limit the size of the ultrasound probe head and thus also the quality of the images. However, with miniaturization based on nanomaterials and

© 2013 Lindseth et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Lindseth et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

nanoelectronics technology, significant improvements in image quality may be obtained. Furthermore, new ultrasound technology can greatly enhance the detection of contrast agents and drug carriers in the tissue. Integration of imaging with navigation technologies will ease image interpretation and further improve precision and accuracy of the therapeutic procedure. Ultrasound technology may also be used for therapeutic purposes. High intensity focused ultrasound (HIFU) for ablation of tumor tissue is already a commercial product. It has also been shown that ultrasound may improve the delivery and distribution of nanoparticles and local drug delivery by enhancing the local release, improving the penetration across the capillary wall and through the extracellular matrix as well as enhance the cellular uptake. The underlying mechanisms are cavitation, radiation force and heating. The ultrasound induced transient increase in porosity and permeability of cell membranes can potentially enhance drug uptake through tissue barriers (also the blood-brain barrier) and improve local drug delivery.

ultrasound needs to be integrated with tracking technology in order to make a navigation system with intraoperative imaging capabilities. In addition, such a system might be able to use preoperative CT/MR data, update these data to match the current patient anatomy using intraoperative ultrasound, extract important structures from the different datasets, present the available multimodal information to the surgeon in an optimal way and be able to track all the surgical tools. Last but not least we need to make sure that the navigation system is highly accurate so that we know that the navigation scene presented to the surgeon on the computer

Ultrasound-Based Guidance and Therapy http://dx.doi.org/10.5772/55884 29

**Figure 1.** Ultrasound-based guidance: A) Freehand guidance: challenge to have the long axis of the instrument in the 2D ultrasound plane. B) Needle guides: an adapter mounted on the probe makes sure that the instrument is within the 2D ultrasound plane. C) Navigation: tracking technology and 3D data from modalities like CT, MR and ultrasound is used to guide relevant surgical instruments in place. Here an ultrasound probe is guided by MR during a freehand

**Figure 2.** A) Workflow: Important steps in image-guided surgery. B) Ultrasound-based navigation example from neu‐ rosurgery: Plan using preoperative MR. Acquire intraoperative 3D ultrasound. Navigation and resection control based

on updated ultrasound images. Acquire additional ultrasound data when needed.

3D ultrasound aquistion

screen is a realistic representation of what's really going on inside the patient.

Therapeutic use of ultrasound will be addressed at the end of this chapter, which is mainly about guiding instruments into the body in a safe way using ultrasound, as well as the technological solutions involved to augment ultrasound in combination with other modalities and techniques. Ultrasound has been used to guide interventional instruments into the body for a long time. Different approaches have been used. From freehand 2D guidance, via "needle" guides mounted on conventional ultrasound probes to ultrasound-based navigation using tracking technology and 3D ultrasound (see figure 1). Surgical navigation will be the focus of this chapter and the analogy to GPS-navigation in a car is clear; instead of plotting the position of the car onto electronic maps of the terrain using satellites and GPS-receivers the position of important surgical instruments are shown on medical images of the patient using highly accurate tracking systems. Systems for image-guided surgery are now well established within many clinical disciplines. Surgical tools may be tracked by positioning systems and the surgeon may accurately navigate the tools into the patient with high precision based on image infor‐ mation only. Intraoperative imaging has shown to be important for obtaining improved tumor resection and increased survival for cancer patients undergoing surgery. Integration of intraoperative imaging with navigation technology, providing the surgeon with *updated* image information, is important to deal with tissue shifts and deformations that occur during surgery. MR, CT and ultrasound have been presented as alternative intraoperative imaging modalities showing complementary information and having different benefits and drawbacks. These intraoperative imaging modalities are reported to be useful for accurate navigation of surgical instruments, monitoring the progression of surgery and solving the shift problem. Intraoper‐ ative imaging has been used for updating preoperative images, which may be important for accurate guidance. In recent years ultrasound has gained increased attention as a useful intraoperative imaging modality (see figure 2), due to improved image quality and relatively low price. In addition, more integrated solutions, that makes the technology user friendly and flexible has been presented. In the evolution of the next generation of ultrasound-based multimodal navigation systems, advances in ultrasound imaging, registration algorithms, visualization and display techniques and navigation accuracy are important ingredients. We will therefore start by looking into the technology that is needed in order to make ultrasoundbased navigation a reality and then show key applications of the navigation technology. Recent advances in ultrasound imaging will be useful also for intraoperative imaging. Furthermore, ultrasound needs to be integrated with tracking technology in order to make a navigation system with intraoperative imaging capabilities. In addition, such a system might be able to use preoperative CT/MR data, update these data to match the current patient anatomy using intraoperative ultrasound, extract important structures from the different datasets, present the available multimodal information to the surgeon in an optimal way and be able to track all the surgical tools. Last but not least we need to make sure that the navigation system is highly accurate so that we know that the navigation scene presented to the surgeon on the computer screen is a realistic representation of what's really going on inside the patient.

nanoelectronics technology, significant improvements in image quality may be obtained. Furthermore, new ultrasound technology can greatly enhance the detection of contrast agents and drug carriers in the tissue. Integration of imaging with navigation technologies will ease image interpretation and further improve precision and accuracy of the therapeutic procedure. Ultrasound technology may also be used for therapeutic purposes. High intensity focused ultrasound (HIFU) for ablation of tumor tissue is already a commercial product. It has also been shown that ultrasound may improve the delivery and distribution of nanoparticles and local drug delivery by enhancing the local release, improving the penetration across the capillary wall and through the extracellular matrix as well as enhance the cellular uptake. The underlying mechanisms are cavitation, radiation force and heating. The ultrasound induced transient increase in porosity and permeability of cell membranes can potentially enhance drug uptake through tissue barriers (also the blood-brain barrier) and improve local drug delivery.

28 Advancements and Breakthroughs in Ultrasound Imaging

Therapeutic use of ultrasound will be addressed at the end of this chapter, which is mainly about guiding instruments into the body in a safe way using ultrasound, as well as the technological solutions involved to augment ultrasound in combination with other modalities and techniques. Ultrasound has been used to guide interventional instruments into the body for a long time. Different approaches have been used. From freehand 2D guidance, via "needle" guides mounted on conventional ultrasound probes to ultrasound-based navigation using tracking technology and 3D ultrasound (see figure 1). Surgical navigation will be the focus of this chapter and the analogy to GPS-navigation in a car is clear; instead of plotting the position of the car onto electronic maps of the terrain using satellites and GPS-receivers the position of important surgical instruments are shown on medical images of the patient using highly accurate tracking systems. Systems for image-guided surgery are now well established within many clinical disciplines. Surgical tools may be tracked by positioning systems and the surgeon may accurately navigate the tools into the patient with high precision based on image infor‐ mation only. Intraoperative imaging has shown to be important for obtaining improved tumor resection and increased survival for cancer patients undergoing surgery. Integration of intraoperative imaging with navigation technology, providing the surgeon with *updated* image information, is important to deal with tissue shifts and deformations that occur during surgery. MR, CT and ultrasound have been presented as alternative intraoperative imaging modalities showing complementary information and having different benefits and drawbacks. These intraoperative imaging modalities are reported to be useful for accurate navigation of surgical instruments, monitoring the progression of surgery and solving the shift problem. Intraoper‐ ative imaging has been used for updating preoperative images, which may be important for accurate guidance. In recent years ultrasound has gained increased attention as a useful intraoperative imaging modality (see figure 2), due to improved image quality and relatively low price. In addition, more integrated solutions, that makes the technology user friendly and flexible has been presented. In the evolution of the next generation of ultrasound-based multimodal navigation systems, advances in ultrasound imaging, registration algorithms, visualization and display techniques and navigation accuracy are important ingredients. We will therefore start by looking into the technology that is needed in order to make ultrasoundbased navigation a reality and then show key applications of the navigation technology. Recent advances in ultrasound imaging will be useful also for intraoperative imaging. Furthermore,

**Figure 1.** Ultrasound-based guidance: A) Freehand guidance: challenge to have the long axis of the instrument in the 2D ultrasound plane. B) Needle guides: an adapter mounted on the probe makes sure that the instrument is within the 2D ultrasound plane. C) Navigation: tracking technology and 3D data from modalities like CT, MR and ultrasound is used to guide relevant surgical instruments in place. Here an ultrasound probe is guided by MR during a freehand 3D ultrasound aquistion

**Figure 2.** A) Workflow: Important steps in image-guided surgery. B) Ultrasound-based navigation example from neu‐ rosurgery: Plan using preoperative MR. Acquire intraoperative 3D ultrasound. Navigation and resection control based on updated ultrasound images. Acquire additional ultrasound data when needed.
