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Updated: Aug 30, 2026

Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition
Published on: March 11, 2021
Technical note: the effect of the 4-mm-collimator output factor on gamma knife dose distributions
John P Gibbons1, Dimitris Mihailidis, Curtis Worthington
1Gamma Knife Center of the Carolinas, Columbia, South Carolina 29203, USA. john.gibbons@palmettohealth.org
Abstract:
We present results of investigations of the clinical significance of variations in the value of the 4-mm-collimator output factor, OF(4/18). Changes in treatment volume, dose-volume histograms (DVHs), and isodose distributions were studied, by varying OF(4/18) up to 20%. The variations were performed on a sample of clinical patient treatment plans for which the 4 mm collimator was used. Although smaller effects are noted for the prescription isodose line, greater dosimetric changes occur for higher dose regions within the target.

