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

M. C. Kreissl, A. Okur, T. Chen, A. Bartel, T. Wendler, K. Scheidhauer
Pilot study of freehand SPECT for lymphatic mapping in melanoma in upper body
Proceedings of the Annual Meeting of the Society of Nuclear Medicine (SNM), Salt Lake City, Utah, USA, June 2010 (bib)

Freehand SPECT (fhSPECT) was introduced lately as a 3D imaging modality capable of mapping sentinel lymph nodes (SLNs) in breast cancer. Due to its compact and flexible nature there is potential to introduce it to the OR for image-guided SLN biopsies (SLNBs). Here we present the first application of it for melanoma patients in anatomies where a guided biopsy could increase safety and the overall output of SLNB. Methods: A fhSPECT system based on a gamma probe and a positioning system was used to scan 20 patients (aged 25-76, average 55.0) with confirmed malignant melanoma in the upper body (1 eye lid, 4 shoulders, 2 sternum, 3 back, 5 lower arm, 5 upper arm). Patients had previously undergone indicated planar scintigraphy (2 min, 2 planes, peritumoral injection of 41-88MBq Tc99m-nanocoll, average 67.9MBq). fhSPECT acquisitions took 173-700s (average 374.0s). Images were reconstructed (MLEM 20i) in grids centered in the region of interest with resolution 5x5x5 mm3. Results: In all patients at least one SLN was mapped in planar scintigraphy and fhSPECT. The all SLNs were located axillar, but 3 submandibular for eye lid and 1 supraclavicular for back. Planar scintigraphy mapped 40 nodes, while fhSPECT mapped 39 nodes. fhSPECT could not resolve close 2 neighboring nodes in 5 pts, and missed completely 1 node in 1 shoulder pt. fhSPECT could resolve 1 further node in 1 pt and 2 further nodes in 2 pts. Sensitivity and positive predictive value of fhSPECT assuming planar scintigraphy as ground truth were 85% (34/40) and 87% (34/39) respectively. In all but 1 shoulder pt, fhSPECT images where considered essentially equivalent as planar scintigraphy. Discussion: Freehand SPECT succeeded to map fairly SLNs in all analyzed anatomies in 19 of 20 pts. Neighboring SLNs not resolved by fhSPECT were not considered to play a major role, due to the fact that close nodes are resected anyhow in practice. This preliminary data supports the introduction of freehand SPECT in a pilot study setup for intraoperative localization of SLNs in melanoma towards image-guided SLNB.
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