title: First experiences of photoacoustic imaging for detection of melanoma metastases in resected human lymph nodes.
abstract: OBJECTIVE
  Excision and histological assessment of the first draining node (sentinel lymph node) is a frequently used method to assess metastatic lymph node involvement related to cutaneous melanoma. Due to the time required for accurate histological assessment, nodal status is not immediately available to the surgeon. Hence, in case histological examination shows metastases, the patient has to be recalled to perform additional lymphadenectomy. To overcome these drawbacks we studied the applicability of photoacoustic tomographic imaging as an intra-operative modality for examining the status of resected lymph nodes.
  
  
  METHODS
  In melanoma patients undergoing lymphadectomy for metastatic disease, six suspect lymph nodes were photoacoustically (PA) imaged using multiple wavelengths. Histopathologal examination showed three nodes without tumor cells (benign nodes) and three nodes with melanoma cells (malignant nodes). PA images were compared with histology and anatomical features were analyzed. In addition, PA spectral analysis was performed on areas of increased signal intensity.
  
  
  RESULTS
  After correlation with histopathology, multiple areas containing melanoma cells could be identified in the PA images due to their increased response. Malignant nodes showed a higher PA response and responded differently to an increase in excitation wavelength than benign nodes. In addition, differences in anatomical features between the two groups were detected.
  
  
  CONCLUSIONS
  Photoacoustic detection of melanoma metastases based on their melanin content proves to be possible in resected human lymph nodes. The amount of PA signal and several specific anatomical features seem to provide additional characteristics for nodal analysis. However, it is as yet preliminary to designate a highly accurate parameter to distinguish between malignant and benign nodes. We expect to improve the specificity of the technique with a future implementation of an adjusted illumination scheme and depth correction for photon fluence.
authors.affiliation: Faculty of Science and Technology, Biomedical Photonic Imaging Group, MIRA Institute for Biomedical Technology, Technical Medicine, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands. d.j.grootendorst@utwente.nl
authors.forename: D J
authors.initials: DJ
authors.lastname: Grootendorst
authors.forename: J
authors.initials: J
authors.lastname: Jose
authors.forename: M W
authors.initials: MW
authors.lastname: Wouters
authors.forename: H
authors.initials: H
authors.lastname: van Boven
authors.forename: J
authors.initials: J
authors.lastname: Van der Hage
authors.forename: T G
authors.initials: TG
authors.lastname: Van Leeuwen
authors.forename: W
authors.initials: W
authors.lastname: Steenbergen
authors.forename: S
authors.initials: S
authors.lastname: Manohar
authors.forename: T J M
authors.initials: TJ
authors.lastname: Ruers
mesh_terms: D001365:Axilla; D014408:Biomarkers, Tumor / Q000378:metabolism; D006801:Humans; D007264:Inguinal Canal; D007430:Intraoperative Care / Q000379:methods*; D053844:Lasers, Solid-State; D008197:Lymph Node Excision; D008207:Lymphatic Metastasis / Q000175:diagnosis*; D008543:Melanins / Q000378:metabolism; D008545:Melanoma / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D061088:Photoacoustic Techniques / Q000379:methods*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D014054:Tomography
chemical_list: D014408:Biomarkers, Tumor; D008543:Melanins