Purpose: To judge how alterations in the measured small field output factors modify the doses in intensity-modulated treatment planning. Methods: IMRT plans were produced using Philips Pinnacle treatment planning system. The plans were enhanced to deal with a round target 2 cm across and a pair of cm long. Output factors for just two Multiplication-Sign 2 and three Multiplication-Sign 3 cm field sizes were altered by 5%, 10%, and 20% increments in the baseline measurements and joined in to the planning system. The therapy units were recommissioned within the treatment planning system after each modification from the output factors and treatment methods were reoptimized. All plans were sent to a good water phantom and dose measurements were created utilizing an ion technology chamber. The proportion variations between measured and computed doses were calculated. An Elekta Synergy along with a Varian 2300CD straight line accelerator were individually evaluated. Results: For that Elekta unit, reducing the output factors led to greater measured than computed doses by .8% for -5%, 3.6% for -10%, and eight.7% for -20% steps. Growing the output factors led to lower doses by 2.9% for &#435%, 5.4% for &#4310%, and eight.3% for &#4320% steps. For that Varian unit no changes were observed for eithermore elevated or decreased output factors. Conclusions: The measurement precision of small field output factors have importance particularly when your skin therapy plan includes small segments as with IMRT. The technique suggested here could be employed to verify the precision from the measured small field output factors for several straight line accelerators in addition to test the beam model. The Head treatment planning system model uses output factors like a purpose of jaw setting.

Consequently, plans while using Elekta unit, which conforms the jaws towards the segments, are responsive to small field measurement precision. However, for that Varian unit, jaws are fixed and segments are modeled as blocked fields hence, the outcome of small field output factors on IMRT monitor unit calculation isn’t evaluable with this method. less

1. Department of Therapeutic Radiology-Radiation Oncology, College of Minnesota, Minneapolis, Minnesota 55455 (U . s . States)

Publication Date: 2012-08-15 OSTI Identifier: 22098939 Resource Type: Journal Source For This Article Relation: Journal Name: Medical Physics Journal Volume: 39 Journal Issue: 8 Additional Information: (c) 2012 American Association of Physicists in Medicine Country of input: Worldwide Atomic Energy Agency (IAEA) Country of Publication: U . s . States Language: British Subject: 62 RADIOLOGY AND NUCLEAR MEDICINE 61 RADIATION PROTECTION AND DOSIMETRY Precision DOSIMETRY Ion technology CHAMBERS JAW Straight line ACCELERATORS PHANTOMS PLANNING RADIATION DOSES RADIOTHERAPY

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