Chair for Computer Aided Medical Procedures & Augmented Reality
Lehrstuhl für Informatikanwendungen in der Medizin & Augmented Reality

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T. Wendler, J. Traub, S. I. Ziegler, N. Navab
Validation of navigated beta-probe imaging with PET/CT-generated activity surfaces. New approach in radio-guided resection for FDG-positive tumors
Proceedings of Annual Meeting of Society of Nuclear Medicine (SNM 2007), Washington D.C., USA, June 2007; Meeting Abstracts 48: 46P-b. (bib)

In a previous work, we introduced a surface imaging system based on beta-probes and spatial localization systems. There we proved in phantoms that such a system gave instinctive feedback to the surgeons in the control of resection borders of FDG-positive tumors. Here, we develop an approach and generate data to validate the thus acquired images by comparing them with beta-emission surfaces created from a preoperative PET/CT. Methods: We implemented a system that acquires the position and the reading of a beta-probe using an optical spatial localization system. Such a system was used to obtain - in 4 experiments of 2-3min (sampling time 0.1s) - the shape and surface distribution of radioactivity on an ad-hoc designed phantom. The phantom was injected in 2 different spots with an aqueous solution of FDG (each 0.5MBq) and then scanned with a PET/CT. With a specially developed model of positron-dispersion together with the PET data we calculated the expected beta-flow at each probe position. In a second step, we extracted the surface of the phantom from the CT and used the model and the PET data to generate the beta-activity at each point of the extracted surface. Finally, the acquired readings and the calculated ones were compared. Results: Both PET and PET/CT generated activities and the acquired probe readings qualitatively agreed well, showing the spots at the expected positions in all experiments. Furthermore, the normalized cross-correlation between beta-probe and PET surfaces was found to be 0.51±0.11. Longer scans (more points) yielded better results due to the increase in counts. Conclusions: The qualitative and quantitative match of the activity surfaces validates the navigated beta-probe imaging system. Moreover, the PET/CT-generated surfaces present a promising visualization for surgical planning. This novel approach is thus introduced as an intuitive intraoperative visualization toward a less invasive and more accurate radio-guided cancer resection. Research Support: The beta-probe was kindly provided by Dr. Farhad Daghighian from IntraMedical? Imaging LLC (Los Angeles, California).
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