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Comparative Study
. 2019 Mar;66(1):44-53.
doi: 10.1002/jmrs.311. Epub 2018 Nov 2.

The role of volumetric modulated arc therapy (VMAT) in gynaecological radiation therapy: A dosimetric comparison of intensity modulated radiation therapy versus VMAT

Penelope Knapp  1 , Belinda Eva  1 , Gemma Reseigh  1 , Adrian Gibbs  1 , Lucy Sim  1 , Tiffany Daly  1 , Judith Cox  1 , Anne Bernard  2
Affiliations
Comparative Study

The role of volumetric modulated arc therapy (VMAT) in gynaecological radiation therapy: A dosimetric comparison of intensity modulated radiation therapy versus VMAT

Penelope Knapp et al. J Med Radiat Sci. 2019 Mar.

Abstract

Introduction: For gynaecological cancers, volumetric modulated arc therapy (VMAT) offers comparable plan quality with shorter treatment delivery times when compared to intensity modulated radiation therapy (IMRT).

Methods: The clinical IMRT plans of twenty gynaecological cancer patients were compared with a retrospectively generated VMAT plan. Planning target volume (PTV) metrics compared were D95 > 99%, homogeneity index, and conformity index. Organs at risk (OAR) doses compared were bladder V45 < 35%, bowel V40 < 30%, femoral head and neck (FHN) V30 < 50%, V44 < 35% and V44 < 5%. Plan quality was also assessed by comparing the monitor units (MU), treatment time and the patient-specific quality assurance results.

Results: VMAT and IMRT resulted in comparable PTV coverage with D95 values of 98.92% ± 0.69% and 98.91% ± 1.43% respectively, and homogeneity index values of 0.08 ± 0.02 (VMAT) and 0.08 ± 0.03 (IMRT). The conformity index for VMAT was 0.93 ± 0.04 and IMRT 0.85 ± 0.06 (P < 0.001). For the bowel tolerance (40 Gy < 30%) VMAT resulted in 22.39% ± 12.5% compared to 28.8% ± 16.78% for IMRT, with bladder and FHN VMAT doses also lower. VMAT MU were 694.35 ± 126.56 compared to 606.8 ± 96.16 for IMRT (P < 0.01). Treatment times of 6.6 ± 0.82 min and 2.47 ± 0.35 min were achieved for IMRT and VMAT respectively.

Conclusion: VMAT showed improvements in sparing OAR compared to IMRT. Target volume coverage with VMAT was equivalent or better than that of IMRT. These results in conjunction with the confirmed shorter treatment delivery time, have led to the development and implementation of a clinical protocol.

Keywords: Dosimetry; gynaecological cancer; intensity modulated radiation therapy; volumetric arc therapy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Dose distribution in a typical transverse and sagittal slice for VMAT compared to IMRT. (A) IMRT (B) VMAT PTV45 is shown by the light blue shaded area; the 95% isodose curve is shown by the thick orange line. The purple and red lines represent 100% of the reference dose and Dmax dose respectively. Dmax, maximum dose.
Figure 2
Figure 2
Mean bladder DVH comparison between IMRT and VMAT.
Figure 3
Figure 3
Mean bowel DVH comparison between IMRT and VMAT.
Figure 4
Figure 4
Mean left femoral head and neck DVH comparison between IMRT and VMAT.
Figure 5
Figure 5
Mean right femoral head and neck DVH comparison between IMRT and VMAT.
Figure 6
Figure 6
Mean rectal wall DVH comparison between IMRT and VMAT.
Figure 7
Figure 7
Mean PTVs (50.4 Gy and 45 Gy) DVH comparison between IMRT and VMAT.
See this image and copyright information in PMC

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