*Objective* This study proves the feasibility of using innovative freehand SPECT (fhSPECT, CSS300 SurgicEye GmbH) for axillary lymphatic mapping in breast cancer patients and defines the border conditions for large scale comparison studies. *Materials-Methods* To date, 14 patients undergoing sentinel lymph node (SLN) biopsy were recruited and scanned intraoperatively using fhSPECT before excision of SLNs. The localization of SLNs with fhSPECT was compared to the position of SLNs detected using gamma probe and blue dye. *Results* Preoperatively, 22 primary and 4 secondary SLNs were mapped with conventional scintigraphy. In the pre-excision scan (performed in 13 of 14 patients) fhSPECT managed to map all but 2 SLNs in the identical position as compared to node location at planar scintigrams (23/25). Gamma probe failed to detect any SLN in 2 patients and mapped in total 17 of 26 nodes. 18 SLNs were resected and confirmed to be radioactive. FhSPECT detected 8 remaining lymph nodes in 8 patients after removal of the SLN. In 3 cases additionally detected nodes were resected and confirmed to be radioactive, while in 5 cases no additional lymph nodes were removed as radioactive uptake was low. Pre-excision fhSPECT acquisitions took approx. 3.3min (SD, 1.3min) while post-excision scans took 3.2min (SD, 1.0min). The surgical procedure was extended by 12min (6min before incision and 6min after excision of SLNs). *Conclusion* Preliminary experience indicates that intraoperative imaging with fhSPECT for lymphatic mapping in breast cancer patients is feasible. Alteration of the surgical workflow can be considered minimal given potential clinical advantages, like intraoperative 3D imaging, documentation of complete resection and minimized invasivity. Due to the promising results fhSPECT will be further evaluated in ongoing studies. *Acknowledgement* This research was partly funded by the DFG's SFB-824 and %NOP%SurgicEye %NOP%GmbH.     «

*Objective* This study proves the feasibility of using innovative freehand SPECT (fhSPECT, CSS300 SurgicEye GmbH) for axillary lymphatic mapping in breast cancer patients and defines the border conditions for large scale comparison studies. *Materials-Methods* To date, 14 patients undergoing sentinel lymph node (SLN) biopsy were recruited and scanned intraoperatively using fhSPECT before excision of SLNs. The localization of SLNs with fhSPECT was compared to the position of SLNs detecte...     »