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DJR 46-2B: Methods to Optimize Conformal Dynamic Arcs in Radiation Therapy Treatment Planning

Course Details

MDCB Credits: 2.50

ARRT Credits: 2.50

Available Until: 6/30/2022

Non-Member Price: $87.50

Member Price: $50.00

Member PLUS Price: $50.00

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Authors: Caroline Kendra, RTT∗, Lon Marsh, CMD, MBA, FAAMD1, Elaine Bogner, CMD, RTT1, Benjamin Gielda, MD1

Department of Radiation Oncology, Spectrum Health Lakeland, Saint Joseph, MI

Abstract
Conformal Dynamic Arcs (CDA) can provide a useful alternative in certain clinical situations which require a higher level of 3-dimensional (3D) conformation than shaped static fields but for which modulated fields (fixed or arc) are inappropriate. Due to lack of modulation, the quality of the dose distribution produced by a CDA is highly dependent on the specific patient geometry. The ideal geometry for a CDA, in terms of achievable conformation and uniformity, is a spherical target perfectly centered in a cylindrical medium or body and utilizing a full 360 degree of rotation. This manuscript will provide or review several methods a treatment planner may employ to improve dose distributions produced by CDA as the patient and/or target geometry or degrees of arc rotation vary from the ideal. These include:

  1. Weighting arc segments to improve homogeneity.
  2. Defining asymmetric margins for fitting leaves.
  3. Hybrid static/CDA compensating for CDA with limited degrees of rotations.
  4. Improving conformation in irregular target via use of pseudo-PTV.
  5. Creating concave features via the use of avoidance structures.
  6. Editing CDA multi-leaf collimator (MLC) to remove irregular hot spots.