Analysis of dose heterogeneity using a subvolume-DVH.

Area of Science:

• Medical Physics
• Radiation Oncology
• Image Analysis

Background:

• The dose-volume histogram (DVH) is a standard tool in radiation therapy for summarizing dose distributions.
• A key limitation of DVHs is the loss of spatial information, hindering the assessment of dose heterogeneity.
• Understanding spatial dose distribution is crucial for optimizing treatment efficacy and minimizing toxicity.

Purpose of the Study:

• To introduce novel methods for overcoming the spatial fragmentation inherent in standard DVHs.
• To present the large cold spot metric (LCS) and subvolume-DVH (sDVH) as tools to evaluate dose heterogeneity.
• To demonstrate how these methods provide insights beyond traditional DVH analysis.

Main Methods:

• Utilized the gray-level size zone matrix, a 2D histogram, to analyze connected regions of similar dose intensities.
• Developed the large cold spot metric (LCS) to quantify large contiguous regions receiving suboptimal doses.
• Extended the standard DVH to create the subvolume-DVH (sDVH) for qualitative assessment of dose heterogeneity.

Main Results:

• The LCS metric quantifies both the size and dose deviation of cold spots, offering a quantitative homogeneity index.
• The sDVH integrates spatial information onto the standard DVH, allowing for simultaneous qualitative evaluation of heterogeneity.
• Both LCS and sDVH effectively reveal dose heterogeneity not apparent from standard DVHs.

Conclusions:

• The LCS and sDVH offer valuable complementary information to standard DVHs in radiation therapy.
• These methods enhance the understanding of spatial dose distributions, aiding in treatment plan evaluation.
• The sDVH provides an intuitive visualization, while the LCS offers a quantitative measure of dose inhomogeneity.