title: IMRT clinical implementation: prostate and pelvic node irradiation using Helios and a 120-leaf multileaf collimator.
abstract: Dynamic intensity modulated radiation therapy (IMRT) to treat prostate and pelvic nodes using the Varian 120-leaf Millennium multileaf collimator (MLC) has been implemented in our clinic. This paper describes the procedures that have been undertaken to achieve this, including some of the commissioning aspects of Helios, verification of the dynamic dose delivery, and quality assurance (QA) of the dose delivered to the patient. Commissioning of Helios included measurements of transmission through the 120-leaf MLC, which were found to be 1.7% for 6 mV and 1.8% for 10 MV. The rounded leaf edge effect, known as the dosimetric separation, was also determined using two independent methods. Values of 1.05 and 1.65 mm were obtained for 6 and 10 MV beams. Five test patients were planned for prostate and pelvic node irradiation to 70 and 50 Gy, respectively. Dose and fluence verification were carried out on specially designed phantoms and dose points in the prostate were measured to be within 2.0% (mean 0.9%, s.d. 0.6%) of the calculated dose and in the nodes within 3.0% (mean 1.6%, s.d. 1.1%). Following the results of this commissioning and implementation study, we have started to treat men with a target Volume including the prostate and pelvic nodes using Helios optimized dynamic IMRT delivery in a dose escalation protocol.
authors.affiliation: Joint Department of Physics, The Royal Marsden NHS Trust, Fulham Road, London SW3 6JJ, United Kingdom. catharine.clark@icr.ac.uk
authors.forename: C H
authors.initials: CH
authors.lastname: Clark
authors.forename: C D
authors.initials: CD
authors.lastname: Mubata
authors.forename: C A
authors.initials: CA
authors.lastname: Meehan
authors.forename: A M
authors.initials: AM
authors.lastname: Bidmead
authors.forename: J
authors.initials: J
authors.lastname: Staffurth
authors.forename: M E
authors.initials: ME
authors.lastname: Humphreys
authors.forename: D P
authors.initials: DP
authors.lastname: Dearnaley
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects; D008297:Male; D010388:Pelvis / Q000528:radiation effects*; D019047:Phantoms, Imaging; D011467:Prostate / Q000528:radiation effects*; D011785:Quality Assurance, Health Care; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods; D013997:Time Factors