Comparing phase- and amplitude-gated volumetric modulated arc therapy for stereotactic body radiation therapy using 3D printed lung phantom.

To compare the dosimetric impact and treatment delivery efficacy of phase-gated volumetric modulated arc therapy (VMAT) vs amplitude-gated VMAT for stereotactic body radiation therapy (SBRT) for lung cancer by using realistic three-dimensional-printed phantoms. Four patient-specific moving lung phantoms that closely simulate the heterogeneity of lung tissue and breathing patterns were fabricated with four planning computed tomography (CT) images for lung SBRT cases. The phantoms were designed to be bisected for the measurement of two-dimensional dose distributions by using EBT3 dosimetry film. The dosimetric accuracy of treatment under respiratory motion was analyzed with the gamma index (2%/1 mm) between the plan dose and film dose measured under phase- and amplitude-gated VMAT. For the validation of the direct usage of the real-time position management (RPM) data for respiratory motion, the relationship between the RPM signal and the diaphragm position was measured by four-dimensional CT. By using data recorded during the beam delivery of both phase- and amplitude-gated VMAT, the total time intervals were compared for each treatment mode. Film dosimetry showed a 5.2 ± 4.2% difference of gamma passing rate (2%/1 mm) on average between the phase- vs amplitude-gated VMAT [77.7% (72.7%-85.9%) for the phase mode and 82.9% (81.4%-86.2%) for the amplitude mode]. For delivery efficiency, frequent interruptions were observed during the phase-gated VMAT, which stopped the beam delivery and required a certain amount of time before resuming the beam. This abnormality in phase-gated VMAT caused a prolonged treatment delivery time of 366 s compared with 183 s for amplitude-gated VMAT. Considering the dosimetric accuracy and delivery efficacy between the gating methods, amplitude mode is superior to phase mode for gated VMAT treatment.

Lee M ，Yoon K ，Cho B ，Kim SS ，Song SY ，Choi EK ，Ahn S ，Lee SW ，Kwak J ... -  《Journal of Applied Clinical Medical Physics》

Simulation of dosimetry impact of 4DCT uncertainty in 4D dose calculation for lung SBRT.

Liu G ，Hu F ，Ding X ，Li X ，Shao Q ，Wang Y ，Yang J ，Quan H ... -  《Radiation Oncology》

Dosimetric evaluation of respiratory gated volumetric modulated arc therapy for lung stereotactic body radiation therapy using 3D printing technology.

Yoon K ，Jeong C ，Kim SW ，Cho B ，Kwak J ，Kim SS ，Song SY ，Choi EK ，Ahn S ，Lee SW ... -  《PLoS One》

4D VMAT planning and verification technique for dynamic tracking using a direct aperture deformation (DAD) method.

We developed a four-dimensional volumetric modulated arc therapy (4D VMAT) planning technique for moving targets using a direct aperture deformation (DAD) method and investigated its feasibility for clinical use. A 3D VMAT plan was generated on a reference phase of a 4D CT dataset. The plan was composed of a set of control points including the beam angle, MLC apertures and weights. To generate the 4D VMAT plan, these control points were assigned to the closest respiratory phases using the temporal information of the gantry angle and respiratory curve. Then, a DAD algorithm was used to deform the beam apertures at each control point to the corresponding phase to compensate for the tumor motion and shape changes. Plans for a phantom and five lung cases were included in this study to evaluate the proposed technique. Dosimetric comparisons were performed between 4D and 3D VMAT plans. Plan verification was implemented by delivering the 4D VMAT plans on a moving QUASAR™ phantom driven with patient-specific respiratory curves. The phantom study showed that the 4D VMAT plan generated with the DAD method was comparable to the ideal 3D VMAT plan. DVH comparisons indicated that the planning target volume (PTV) coverages and minimum doses were nearly invariant, and no significant difference in lung dosimetry was observed. Patient studies revealed that the GTV coverage was nearly the same; although the PTV coverage dropped from 98.8% to 94.7%, and the mean dose decreased from 64.3 to 63.8 Gy on average. For the verification measurements, the average gamma index pass rate was 98.6% and 96.5% for phantom 3D and 4D VMAT plans with 3%/3 mm criteria. For patient plans, the average gamma pass rate was 96.5% (range 94.5-98.5%) and 95.2% (range 94.1-96.1%) for 3D and 4D VMAT plans. The proposed 4D VMAT planning technique using the DAD method is feasible to incorporate the intra-fraction organ motion and shape change into a 4D VMAT planning. It has great potential to provide high plan quality and delivery efficiency for moving targets.

Zhang Y ，Yang Y ，Fu W ，Li X ，Li T ，Heron DE ，Huq MS ... -  《Journal of Applied Clinical Medical Physics》

4D VMAT, gated VMAT, and 3D VMAT for stereotactic body radiation therapy in lung.

Chin E ，Loewen SK ，Nichol A ，Otto K ... -  《-》