Pilot study of freehand SPECT for lymphatic mapping in melanoma in upper body

Objectives: 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.     «

Objectives: 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 sys...     »