Affiliations: Radiation Oncology, Oklahoma University Health
Sciences Center, Oklahoma City, OK 73104, USA. Radiation Oncology, University
of Massachusetts Memorial Medical Center Worcester, MA 01655, USA
Note: [] Corresponding author: George Mardirossian, Ph.D., Oklahoma
University Health Sciences Center, Department of Radiological Sciences, 1200 N.
Everett Dr., Room B603, Oklahoma City, OK 73104, USA. Tel.: +1 405 271 6453;
Fax: +1 405 271 8297; E-mail: George-Mardirossian@ouhsc.edu
Abstract: Commissioning of a Radionics miniature multi-leaf collimator (MMLC)
for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) is
reported. With single isocenter and multi static fields, the MMLC can provide
better conformity of dose distributions to the target and/or irregularly shaped
target volumes than standard arc (circular) field beams with multiple
isocenters. Advantages offered by the MMLC over traditional LINAC based SRS and
SRT includes greatly improved dose homogeneity to the target, reduced patient
positioning time and reduced treatment time. In this work, the MMLC is attached
to a Varian 2300 C/D with Varian 80-leaf multi-leaf collimator. The MMLC has 62
leaves, each measured to a width of 3.53 mm at isocenter, with fields range
from 1 × 1 cm to less than 10 × 12 cm. Beam parameters
required by the Radionics treatment planning system (XPlan version 2) for
evaluating the dose include tissue maximum ratio (TMR), scatter factors (SF),
off-axis ratios (OAR), output factors, penumbra function (P) and transmission
factors (TF) are performed in this work. Beam data are acquired with a small
stereotactic diode, standard ion chambers and radiographic films. Measured
profiles of dose distribution are compared to those calculated by the software
and absolute dosimetry is performed.
