title: Real-time in vivo rectal wall dosimetry using MOSkin detectors during linac based stereotactic radiotherapy with rectal displacement.
abstract: BACKGROUND
  MOSFET dosimetry is a method that has been used to measure in-vivo doses during brachytherapy treatments and during linac based radiotherapy treatment. Rectal displacement devices (RDDs) allow for safe dose escalation for prostate cancer treatment. This study used dual MOSkin detectors to assess real-time in vivo rectal wall dose in patients with an RDD in place during a high dose prostate stereotactic body radiation therapy (SBRT) boost trial.
  
  
  METHODS
  The PROMETHEUS study commenced in 2014 and provides a prostate SBRT boost dose with a RDD in place. Twelve patients received two boost fractions of 9.5-10 Gy each delivered to the prostate with a dual arc volumetric modulated arc therapy (VMAT) technique. Two MOSkins in a face-to-face arrangement (dual MOSkin) were used to decrease angular dependence. A dual MOSkin was attached to the anterior surface of the Rectafix and read out at 1 Hz during each treatment. The planned dose at each measurement point was exported from the planning system and compared with the measured dose. The root mean square error normalised to the total planned dose was calculated for each measurement point and treatment arc for the entire course of treatment.
  
  
  RESULTS
  The average difference between the measured and planned doses over the whole course of treatment for all arcs measured was 9.7% with a standard deviation of 3.6%. The cumulative MOSkin reading was lower than the total planned dose for 64% of the arcs measured. The average difference between the final measured and final planned doses for all arcs measured was 3.4% of the final planned dose, with a standard deviation of 10.3%.
  
  
  CONCLUSIONS
  MOSkin detectors were an effective tool for measuring dose delivered to the anterior rectal wall in real time during prostate SBRT boost treatments for the purpose of both ensuring the rectal doses remain within acceptable limits during the treatment and for the verification of final rectal doses.
authors.affiliation: University of Newcastle, University Drive, Callaghan, 2308, NSW, Australia. Kimberley.Legge@uon.edu.au.
authors.forename: Kimberley
authors.identifier: http://orcid.org/0000-0002-2262-2025
authors.initials: K
authors.lastname: Legge
authors.affiliation: University of Newcastle, University Drive, Callaghan, 2308, NSW, Australia.|Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Greer
authors.affiliation: University of Newcastle, University Drive, Callaghan, 2308, NSW, Australia.
authors.forename: Daryl J
authors.initials: DJ
authors.lastname: O'Connor
authors.affiliation: Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Lee
authors.initials: L
authors.lastname: Wilton
authors.affiliation: Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Richardson
authors.affiliation: Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Perry
authors.initials: P
authors.lastname: Hunter
authors.affiliation: Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Alex
authors.initials: A
authors.lastname: Wilfert
authors.affiliation: Calvary Mater Newcastle, Cnr Edith and Platt Streets, Waratah, 2298, NSW, Australia.
authors.forename: Jarad
authors.initials: J
authors.lastname: Martin
authors.affiliation: University of Wollongong, Wollongong, 2522, NSW, Australia.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Rosenfeld
authors.affiliation: University of Wollongong, Wollongong, 2522, NSW, Australia.
authors.forename: Dean
authors.initials: D
authors.lastname: Cutajar
mesh_terms: D004867:Equipment Design; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000601:surgery*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects*
keywords: In vivo dosimetry; MOSFET detector; Prostate cancer; Stereotactic radiation therapy