B. Frisch, M. Eiber, J. Gardiazabal, P. Matthies, T. Maurer, A. Okur, T. Lasser, N. Navab Challenges for Intra-Operative SPECT IEEE Nuclear Science Symposium and Medical Imaging Conference, Seattle, USA, November 2014 (bib)
	Classical intra-operative imaging is limited to anatomical modalities like X-Ray and ultrasound, without the possibility of acquiring metabolic information. The intra-operative use of single-channel gamma probes allows detecting radioactive tracers, but does not o ffer the possibility of 3D imaging. This limitation is overcome with the freehand SPECT approach, where a gamma probe is spatially tracked, in order to reconstruct a three-dimensional image that augments the live camera image of the patient. We improve this technique by using a 16x16 channel CZT crystal gamma camera held by a light-weight robotic arm, a system that can be brought into any operating room for the relevant phases of the surgery. The positions of the camera can either be determined by the robotic arm itself or with an optical tracking system. The robotic path can either be predefined or be based on pre-interventional or interventional anatomical patient data. While the multi-channel gamma camera improves the system sensitivity, the robotic approach reduces the need for the surgeon to hold this device and improves repeatability. A method to model the detector and to calibrate the camera with respect to the robotic arm are presented. Images are reconstructed with an iterative MLEM algorithm. We con firm the validity of this approach with a spherical source phantom study that shows the accuracy of the system and a liver vessel study that con firms the possibility of imaging complex structures. Finally, an overview of current clinical cases confi rms the necessity of developments a the crossing points of medicine, detector technology and informatics.
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