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

J. Traub, K. Herrmann, T. Wendler, T. Lasser, M. Schwaiger, N. Navab, S. I. Ziegler, A. K. Buck
First clinical results of freehand SPECT for lymphatic mapping in breast cancer
Proceedings of the Molekulare Bildgebung (MOBI), Berlin, Germany, Jun. 2009 (bib)

Objectives
Evaluate the feasibility of the recently introduced freehand SPECT imaging technology for 3D lymphatic mapping of breast cancer patients. Methods: The position and orientation of a gamma probe is acquired simultaneously with its read-out using an optical positioning system. After obtaining synchronized readings from a freehand scan containing the region of interest, the information is used to reconstruct 3D tomographic nuclear images (equivalent to SPECT) using ad hoc models and iterative reconstruction algorithms. In addition, imaging with a standard planar scintigraphy camera and a SPECT/CT device were performed. Both, SPECT data and freehand SPECT were registered within the same coordinate system for comparison. For evaluation a quality value was calculated for every freehand SPECT acquisition; the scans were divided in groups with good, intermediate and poor predicted reconstruction behavior. Results: A group of 47 pts (age 29-87) with suspected T1 or T2 invasive breast cancer and no clinical evidence of nodal involvement underwent lymphatic mapping (Tc-99m nanocol, 35-79 MBq). In 44 pts with at least one visible SLN, SPECT/CT and a freehand SPECT scan were generated (3.1±0.7 min). SLNs were mapped using freehand SPECT in 21 patients (25 nodes). Assuming that the SPECT/CT result is correct, freehand SPECT presented no false positive and 41 false negative axillary nodes (23 patients). False negative findings can be explained mostly by insufficient scan time, insufficient coverage of axillary region and low tracer uptake (measured range 0.01-20.18%, average 1.74%). For good quality scans the sensitivity was 77.8% (9 nodes), while for intermediate and poor quality scans it was calculated to be 29.7% and 21.9% (37 and 20 nodes respectively). Conclusions: In this pilot study, we could demonstrate that the novel freehand SPECT technology is capable of localizing hot spots at the same 3D position compared to that of conventional SPECT. In order to guarantee a quality of scan the here detected parameters have to be applied. In case of lymphatic mapping in breast cancer, this approach has a potential to allow guided biopsy and further standardization of SLN dissection, thus opening new paths of Nuclear Medicine in the OR.
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