Prog Med Phys.  2018 Dec;29(4):157-163. 10.14316/pmp.2018.29.4.157.

Dosimetric Evaluation of Plans Converted with the DVH-Based Plan Converter

• Chun M
• Choi CH
• Kim JI
• Yoon J
• Lee SY
• Kwon O
• Son J
• An HJ
• Kang SH
• Park JM

• KMID: 2434650
• DOI: http://doi.org/10.14316/pmp.2018.29.4.157

Abstract

Plans converted using dose-volume-histogram-based plan conversion (DPC) were evaluated by comparing them to the original plans. Changes in the dose volumetric (DV) parameters of five volumetric modulated arc therapy (VMAT) plans for head and neck (HN) cancer and five VMAT plans for prostate cancer were analyzed. For the HN plans, the homogeneity indices (HIs) of the three planning target volumes (PTV) increased by 0.03, 0.02, and 0.03, respectively, after DPC. The maximum doses to the PTVs increased by 1.20, 1.87, and 0.92 Gy, respectively, after DPC. The maximum doses to the optic chiasm, optic nerves, spinal cord, brain stem, lenses, and parotid glands increased after DPC by approximately 4.39, 3.62, 7.55, 7.96, 1.77, and 6.40 Gy, respectively. For the prostate plans after DPC, the HIs for the primary and boost PTVs increased by 0.05 and 0.03, respectively, and the maximum doses to each PTV increased by 1.84 and 0.19 Gy, respectively. After DPC, the mean doses to the rectum and femoral heads increased by approximately 6.19 and 2.79 Gy, respectively, and those to the bladder decreased by 0.20 Gy when summing the primary and boost plans. Because clinically unacceptable changes were sometimes observed after DPC, plans converted by DPC should be carefully reviewed before actual patient treatment.

Keyword

DVH-based plan converter; Volumetric modulated arc therapy; Step-and-shoot IMRT; Dose-volumetric parameters; Plan quality

MeSH Terms

Brain Stem
Head
Humans
Neck
Optic Chiasm
Optic Nerve
Parotid Gland
Prostate
Prostatic Neoplasms
Radiotherapy, Intensity-Modulated
Rectum
Spinal Cord
Urinary Bladder

Figure

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  Fig. 1 A representative patient's dose distributions for the head and neck case are presented before (upper row) and after (lower row) dose volume histogram based plan conversion. Doses are shown in color wash from 40% of the prescription dose to the maximum dose. Axial (a and d), coronal (b and e), and sagittal (c and f) planes are shown.

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  Fig. 2 A representative patient's dose volume histograms (DVHs) for the head and neck case are shown. DVHs from the original plan are plotted with solid lines, while those from the converted plan using the dose volume histogram based plan conversion are plotted with dashed lines.

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  Fig. 3 A representative patient's dose distributions for the prostate case is presented before (upper row) and after (lower row) dose volume histogram based plan conversion. Doses are shown in color wash from 30% of the prescription dose to the maximum dose. Axial (a and d), coronal (b and e), and sagittal (c and f) planes are shown.

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  Fig. 4 A representative patient's dose volume histograms (DVHs) for the prostate case are shown. DVHs from the original plan are plotted with solid lines, while those from the converted plan using the dose volume histogram based plan conversion are plotted with dashed lines.

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