Real-time ultrasound virtual navigation in 3D PET/CT volumes for superficial lymph node evaluation: an innovative fusion examination

Objective: To evaluate the feasibility and clinical applications of Fusion Virtual Navigation of 18 F-FDG PET/CT (PET/CT) and ultrasound images in assessing superficial lymph nodes in breast and gynecological cancer patients.Methods: This is a single-center pilot study. Consecutive patients with breast or gynecological cancer with abnormal uptake of axillary or groin lymph nodes on PET/CT scan, also submitted to ultrasound assessment, were enrolled between January 2017 and May 2019. Fusion was performed acquiring PET/CT DICOM images on the ultrasound machine and synchronizing them with real time ultrasound scanning performed on the lymph node site. The abnormal lymph node was previously marked on PET/CT and retrieved during ultrasound navigation. In a first phase, we assessed the feasibility of Fusion in a series of 10 patients with suspicious lymph nodes on both PET/CT and ultrasound with full correspondence in terms of size, shape and morphology (group A). In a second phase, we included patients with un-corresponding findings between PET/CT and ultrasound: patients with a suspicious lymph node uptake on PET/CT scan and a negative ultrasound assessment (group B), and patients with suspected lymph nodes at both PET/CT and ultrasound but with no correspondence in terms of number of lymph nodes between the two techniques (group C).Results: 30 patients were selected and Fusion was performed in 30 lymph node sites (22/30 inguinal, 8/30 axillary nodes). In the first phase, we evaluated 10 lymph node sites (group A) and Fusion technique was feasible in all of them. In the second phase, we selected 20 lymph node sites: 10 in group B, and 10 in group C. Fusion was successfully completed in 9/10 cases of group B and in all 10 cases of group C. In both groups Fusion was able to identify the target lymph node, guiding the examiner to perform a core needle biopsy or to inject radiotracer for selective surgical nodal excision, according to radio-guided occult lesion localization (ROLL) technique.Conclusion: Fusion virtual navigation using PET/CT and ultrasound images is feasible and able to detect target lymph nodes when inconsistent results between PET/CT and ultrasound are present. Fusion technique can also guide the examiner to perform a core needle biopsy, avoiding further surgical diagnostic procedures, or a more sparing selective surgery. This innovative technique opens up to multiple diagnostic and therapeutic opportunities in breast and gynecological oncology.