title: Surface markers for guiding cylindrical diffuser fiber insertion in interstitial photodynamic therapy of head and neck cancer.
abstract: Image-based treatment planning can be used to compute the delivered light dose during interstitial photodynamic therapy (I-PDT) of locally advanced head and neck squamous cell carcinoma (LA-HNSCC). The objectives of this work were to evaluate the use of surface fiducial markers and flexible adhesive grids in guiding interstitial placement of laser fibers, and to quantify the impact of discrepancies in fiber location on the expected light dose volume histograms (DVHs).
  
  
  
  Seven gel-based phantoms were made to mimic geometries of LA-HNSCC. Clinical flexible grids and fiducial markers were used to guide the insertion of optically transparent catheters, which are used to place cylindrical diffuser fibers within the phantoms. A computed tomography (CT) was used to image the markers and phantoms before and after catheter insertion and to determine the difference between the planned and actual location of the catheters. A finite element method was utilized to compute the light DVHs. Statistical analysis was employed to evaluate the accuracy of fiber placement and to investigate the correlation between the location of the fibers and the calculated DVHs.
  
  
  
  There was a statistically significant difference (P = 0.018) between all seven phantoms in terms of the mean displacement. There was also statistically significant correlation between DVHs and depth of insertion (P = 0.0027), but not with the lateral displacement (P = 0.3043). The maximum difference between actual and planned DVH was related to the number of fibers (P = 0.0025) and the treatment time.
  
  
  
  Surface markers and a flexible grid can be used to assist in the administration of a prescribed DVH within 15% of the target dose provided that the treatment fibers are placed within 1.3 cm of the planned depth of insertion in anatomies mimicking LA-HNSCC. The results suggest that the number of cylindrical diffuser fibers and treatment time can impact the delivered DVHs. Lasers Surg. Med. 49:599-608, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Photodynamic Therapy Center, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: Emily
authors.initials: E
authors.lastname: Oakley
authors.affiliation: Photodynamic Therapy Center, Roswell Park Cancer Institute (RPCI), Buffalo, New York.|Department of Cell Stress Biology, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: David A
authors.initials: DA
authors.lastname: Bellnier
authors.affiliation: Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: Alan
authors.initials: A
authors.lastname: Hutson
authors.affiliation: Photodynamic Therapy Center, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: Brian
authors.initials: B
authors.lastname: Wrazen
authors.affiliation: Photodynamic Therapy Center, Roswell Park Cancer Institute (RPCI), Buffalo, New York.|Department of Head and Neck Surgery, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: Hassan
authors.initials: H
authors.lastname: Arshad
authors.affiliation: Department of Radiation Oncology and Molecular Radiation Sciences, Department of Otorhinolaryngology-Head and Neck Surgery, Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Harry
authors.initials: H
authors.lastname: Quon
authors.affiliation: Photodynamic Therapy Center, Roswell Park Cancer Institute (RPCI), Buffalo, New York.|Department of Cell Stress Biology, Roswell Park Cancer Institute (RPCI), Buffalo, New York.|Department of Head and Neck Surgery, Roswell Park Cancer Institute (RPCI), Buffalo, New York.
authors.forename: Gal
authors.initials: G
authors.lastname: Shafirstein
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000188:drug therapy*; D002404:Catheterization / Q000379:methods*; D057918:Fiducial Markers; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy*; D006801:Humans; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D000077195:Squamous Cell Carcinoma of Head and Neck; D014057:Tomography, X-Ray Computed
chemical_list: D000970:Antineoplastic Agents; D017319:Photosensitizing Agents
keywords: and neck cancer; fiducial markers; finite element; head; interstitial photodynamic therapy