title: Attenuation measurements show that the presence of a TachoSil surgical patch will not compromise target irradiation in intra-operative electron radiation therapy or high-dose-rate brachytherapy.
abstract: BACKGROUND
  Surgery of locally advanced and/or recurrent rectal cancer can be complemented with intra-operative electron radiation therapy (IOERT) to deliver a single dose of radiation directly to the unresectable margins, while sparing nearby sensitive organs/structures. Haemorrhages may occur and can affect the dose distribution, leading to an incorrect target irradiation. The TachoSil (TS) surgical patch, when activated, creates a fibrin clot at the surgical site to achieve haemostasis. The aim of this work was to determine the effect of TS on the dose distribution, and ascertain whether it could be used in combination with IOERT. This characterization was extended to include high dose rate (HDR) intraoperative brachytherapy, which is sometimes used at other institutions instead of IOERT.
  
  
  METHODS
  CT images of the TS patch were acquired for initial characterization. Dosimetric measurements were performed in a water tank phantom, using a conventional LINAC with a hard-docking system of cylindrical applicators. Percentage Depth Dose (PDD) curves were obtained, and measurements made at the depth of dose maximum for the three clinically used electron energies (6, 9 and 12MeV), first without any attenuator and then with the activated patch of TS completely covering the tip of the IOERT applicator. For HDR brachytherapy, a measurement setup was improvised using a solid water phantom and a Farmer ionization chamber.
  
  
  RESULTS
  Our measurements show that the attenuation of a TachoSil patch is negligible, both for high energy electron beams (6 to 12MeV), and for a HDR (192)Ir brachytherapy source. Our results cannot be extrapolated to lower beam energies such as 50 kVp X-rays, which are sometimes used for breast IORT.
  
  
  CONCLUSIONS
  The TachoSil surgical patch can be used in IORT procedures using 6MeV electron energies or higher, or HDR (192)Ir brachytherapy.
authors.affiliation: Medical Physics Department, Portuguese Institute of Oncology, Porto, Portugal. ssarment@gmail.com.|Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. ssarment@gmail.com.
authors.forename: Sandra
authors.initials: S
authors.lastname: Sarmento
authors.affiliation: Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. filipa.apbcosta@gmail.com.
authors.forename: Filipa
authors.initials: F
authors.lastname: Costa
authors.affiliation: Medical Physics Department, Portuguese Institute of Oncology, Porto, Portugal. alex.mendes.pereira@gmail.com.|Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. alex.mendes.pereira@gmail.com.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Pereira
authors.affiliation: Medical Physics Department, Portuguese Institute of Oncology, Porto, Portugal. joana.lencart@gmail.com.|Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. joana.lencart@gmail.com.
authors.forename: Joana
authors.initials: J
authors.lastname: Lencart
authors.affiliation: Medical Physics Department, Portuguese Institute of Oncology, Porto, Portugal. adias4@gmail.com.|Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. adias4@gmail.com.
authors.forename: Anabela
authors.initials: A
authors.lastname: Dias
authors.affiliation: Medical Physics Department, Portuguese Institute of Oncology, Porto, Portugal. luisptcunha@gmail.com.|Medical Physics, Radiobiology and Radiation Protection Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. luisptcunha@gmail.com.
authors.forename: Luís
authors.initials: L
authors.lastname: Cunha
authors.affiliation: Radiation Oncology Department, Portuguese Institute of Oncology, Porto, Portugal. olgatspinto@gmail.com.
authors.forename: Olga
authors.initials: O
authors.lastname: Sousa
authors.affiliation: Surgical Oncology Department, Portuguese Institute of Oncology, Porto, Portugal. jpmsilva72@gmail.com.
authors.forename: José Pedro
authors.initials: JP
authors.lastname: Silva
authors.affiliation: Surgical Oncology Department, Portuguese Institute of Oncology, Porto, Portugal. llarasantos@gmail.com.|Experimental Pathology and Therapeutics Group, Research Centre, Portuguese Institute of Oncology, Porto, Portugal. llarasantos@gmail.com.
authors.forename: Lúcio
authors.initials: L
authors.lastname: Santos
mesh_terms: D001918:Brachytherapy; D004338:Drug Combinations; D004583:Electrons / Q000627:therapeutic use*; D005340:Fibrinogen / Q000008:administration & dosage*; D006801:Humans; D007430:Intraoperative Care; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D009369:Neoplasms / Q000532:radiotherapy*; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D011882:Radiotherapy, High-Energy; D015503:Surgical Sponges; D013917:Thrombin / Q000008:administration & dosage*; D014057:Tomography, X-Ray Computed
chemical_list: D004338:Drug Combinations; D007496:Iridium Radioisotopes; C518955:TachoSil; D005340:Fibrinogen; D013917:Thrombin