title: SPECT-CT for topographic mapping of sentinel lymph nodes prior to gamma probe-guided biopsy in head and neck squamous cell carcinoma.
abstract: BACKGROUND
  Lymphoscintigraphic planar imaging is a common procedure for sentinel lymph node imaging prior to lymph node biopsy, but fails to elucidate the specific lymphatic drainage. Composite functional/anatomical imaging (SPECT-CT) has the potential to enhance topographic orientation and diagnostic sensitivity of sentinel lymph node imaging, but has not yet been applied in the head and neck region.
  
  
  METHODS
  A total of 30 patients were investigated. Planar imaging was 5 min, 265 x 265, right and left lateral; 500 kilocounts (Kcts) and SPECT (GE Millenium VG Hawk Eye 6 degrees/30s. step, 128 x 128, slice thickness 4.42 mm). Scans were performed 60 min after intra-mucodermal injection of 0.1 ml of 20 MBq 99mTc nanocolloid in patients with squamous cell cancer of the head and neck. SPECT studies were analysed by filtered back projection (FBP: Hann (0.7) prefiltering, Butterworth (0.5) postfiltering) and reconstruction (OSEM: Post Filter Hamming (0.85), 2 Iterations) and independently viewed with the co-registered CT image (eNTEGRA Functional Anatomical Fusion Vers 2.0216). The results were validated by comparing the results of each method employed in all 30 cases and intraoperative gamma probe-guided sentinel lymph node biopsy with histological examination in 13 of these patients.
  
  
  RESULTS
  The majority of patients had more than one sentinel node (mean 1.63, min. 0, max. 4). Seven out of the 30 studies demonstrated lymphatic flow to the contralateral side of the neck. Forty-nine sentinel nodes were identified by iteratively reconstructed SPECT-CT. Thirty-eight out of these 49 could be located in lymphoscintigraphic planar imaging, whereas only 24/49 were detected in filtered back projection, respectively. In 11 of the 30 cases, a clinically unpredictable pattern of lymphatic drainage was observed. No correlation was found between T stage or tumour location and the number of sentinel nodes detected. In one out of the 13 cases, in whom imaging was followed by intraoperative gamma probe-guided biopsy, no sentinel node could be detected with the probe in the proximity of the primary tumour, although the node was clearly discernible in the reconstructed SPECT-CT.
  
  
  CONCLUSIONS
  Composite functional/anatomical imaging (SPECT-CT) is feasible for sentinel lymph node detection. It enhances topographic orientation and diagnostic sensitivity with more sentinel nodes being detectable than by planar lymphoscintigraphy alone. Planar imaging should be accompanied by iterative reconstructed SPECT-CT to identify lymph nodes adjacent to the primary lesion. Such nodes are easily overlooked by planar lymphoscintigraphy and intraoperative gamma probes, as the high activity at the injection site can obscure their detection.
authors.affiliation: University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical School, University of Vienna, Austria. arne.wagner@univie.ac.at
authors.forename: Arne
authors.initials: A
authors.lastname: Wagner
authors.forename: Kurt
authors.initials: K
authors.lastname: Schicho
authors.forename: Christoph
authors.initials: C
authors.lastname: Glaser
authors.forename: Georg
authors.initials: G
authors.lastname: Zettinig
authors.forename: Kaan
authors.initials: K
authors.lastname: Yerit
authors.forename: Susanne
authors.initials: S
authors.lastname: Lang
authors.forename: Clemens
authors.initials: C
authors.lastname: Klug
authors.forename: Thomas
authors.initials: T
authors.lastname: Leitha
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D015902:Gamma Cameras; D006258:Head and Neck Neoplasms / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000473:pathology / Q000601:surgery; D009367:Neoplasm Staging; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000601:surgery; D019275:Radiopharmaceuticals; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D013668:Technetium Tc 99m Aggregated Albumin; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin; C083602:technetium Tc 99m nanocolloid