Volumetric-modulated arc therapy with RapidArc: An evaluation of treatment delivery efficiency

Abstract

Aim/background

To evaluate how the use of volumetric-modulated arc therapy (VMAT) with RapidArc^® can improve treatment delivery efficiency based on the analysis of the beam-on times and monitor units (MU) needed to deliver therapy for multiple clinical applications in a large patient population.

Materials and methods

A total of 898 treatment courses were delivered in 745 patients treated from October 2008 to March 2013 using RapidArc® treatment plans generated in Eclipse™ TPS. All patients were treated with curative or palliative intent using different techniques including conventional fractionation (83%) and radiosurgery or SBRT (17%), depending on the clinical indications. Treatment delivery was evaluated based on measured beam-on time and recorded MU values delivered on a Varian Trilogy™ linear accelerator.

Results

For conventional fractionation treatments using RapidArc®, the delivery times ranged from 38[[ce:hsp sp="0.25"/]]s to 4[[ce:hsp sp="0.25"/]]min and 40[[ce:hsp sp="0.25"/]]s (average 2[[ce:hsp sp="0.25"/]]min and 6[[ce:hsp sp="0.25"/]]s). For radiosurgical treatments the delivery times ranged from 1[[ce:hsp sp="0.25"/]]min and 42[[ce:hsp sp="0.25"/]]s to 9[[ce:hsp sp="0.25"/]]min and 22[[ce:hsp sp="0.25"/]]s (average 4[[ce:hsp sp="0.25"/]]min and 4[[ce:hsp sp="0.25"/]]s). The average number of MU per Gy was 301 for the entire group, with 285 for the conventional group and 317 for the radiosurgical group.

Conclusions

In this study with a large heterogeneous population, treatments using RapidArc® were delivered with substantially less beam-on time and fewer MUs than conventional fractionation. This was highly advantageous, increasing flexibility of the scheduling allowing treatment of radiosurgery patients during the regular daily work schedule. Additionally, reduction of leakage radiation dose was achieved.