Method
Results
Conclusions
With the development of UWGSP7, the University of Washington Image Computing Systems Laboratory (UW ICSL) has a real-time optical imaging workstation for continuous-wave (CW) optical reflectance imaging. The system has been developed to provide researchers with a high-performance, versatile tool for use in optical imaging experiments. The eventual goal is to bring this technology into the surgical suite, providing real-time information to assist decision making during the course of surgery.
Method
Results
Conclusions
CW optical imaging consists of illumination of a target with a band-limited source and monitoring of the light transmitted by or reflected from the target. One of several major applications of CW optical reflectance imaging is tumor imaging which uses a light-absorbing agent that sequesters in tumor tissue. This property could be used in locating tumors and identifying tumor margins intraoperatively. While continuously illuminating the target, a control image is captured and stored. An agent is injected into the subject while a sequence of data images is captured and processed. The data images are aligned with the control image and then subtracted to obtain a signal representing the change in optical reflectance over time. This signal can be enhanced by digital image processing and displayed with a pseudo color mapping. Visualization may include showing large changes with a bright color and small changes with a dark color. This type of emerging imaging technique requires a computer system which is versatile and adaptable. During Phase 1 of the project, a real-time optical imaging workstation has been designed and implemented. The UWGSP7 utilizes a VESA Local Bus PC as a host computer running the Windows NT operating system and includes UW-developed add-on boards for image acquisition and processing. The image acquisition board is used to digitize and format the analog signal from the input device into frames, and to average the frames. To accommodate different input devices, the camera interface circuitry is designed in a small mezzanine card. The image acquisition board is connected to the image processing board using a direct connect port which provides a 66 Mbytes/s channel independent of the system bus. The image processing board utilizes a Texas Instruments TMS320C80 Multimedia Video Processor (MVP) chip. The MVP is capable of 2 billion operations per second, providing the UWGSP7 with the ability to perform image processing functions such as median filtering, convolution and histogram stretching in real time. UWGSP7 can also perform interactive processing and analysis of experiments in contrast with previous methods using off-line processing and analysis. The user can choose various image processing algorithms to process and visualize the data. During Phase 2 of the project, the UWGSP7 is being used to visualize tumors and tumor margins in nude mice implanted with human renal cell carcinoma xenografts. A CCD camera is utilized as an input device to the UWGSP7. The image acquisition is started and then the mouse is injected with a light-absorbing agent. The image acquisition is continued for up to 10 minutes. After image acquisition, the results of the experiment can be observed. Different regions of interest (tumor tissue and non-tumor tissue) are selected and the average illumination of each region is calculated. The change in optical reflectance over time is graphed, showing that the tumor tissue exhibits a sequestering of the dye over time compared to non-tumor tissue.
During Phase 1, we successfully designed and implemented a versatile and adaptable system for real-time optical imaging. We have completed system integration and designed a flexible user interface. Currently we are conducting more tests in Phase 2, utilizing human renal cell carcinoma xenografts in nude mice.
The UWGSP7 has been developed as a programmable high-performance platform for real-time optical imaging. Due to its flexibility and programmability, the UWGSP7 can be adapted into various research needs in intraoperative optical imaging of tumors and other applications.
Key Words: Optical imaging, Tumor visualization, Image capture and analysis, Image processing, Workstation