Top Line: How does plan quality compare among the latest SRS treatment platforms?
The Study: In 2016, the UK NHS conducted a benchmarking study for intracranial SRS. This study provides an updated evaluation of the latest technology. The SRS platforms included: GammaKnife with Lightning inverse planning, CyberKnife S7 with M6 MLC, Elekta Versa HD with Brainlab Elements, Varian TrueBeam with Brainlab Elements, and Varian Edge with HyperArc and Zap-X. Six benchmark cases from the 2016 study were used and a 7th case with 14 targets was added. These included a range of scenarios including brain metastasis, vestibular schwannoma, meningioma, and pituitary adenoma. Plan parameters and goals were pre-specified including the prescription dose, target coverage, OAR constraints, and gradient objectives. A 1mm PTV margin was used only when treating metastases with a C-arm LINAC but not in any other cases. All the platforms had adequate target coverage. Paddick conformity indices ranged from 0.700 to 0.896 (CyberKnife). Gradient indices (GI) ranged from 3.66 (GK) to 5.27 (HyperArc using 10X). The efficiency index ranged from ~42%-55% for 3 targets, 48%-60% for 7 targets, and 35% to 50% for 14 targets. The efficiency index is a newer measure of conformity, gradient, and mean target dose. It is calculated as the ratio of integral dose in the target (mean dose x volume) and integral dose to the 50% isodose volume. When it came to gradient index, beam energy appeared to have the greatest influence with lower energy platforms having the lowest GIs and vice versa for high beam energy. Another takeaway was that VMAT typically resulted in better conformity at the slight expense of higher gradient compared to platforms that used dynamic conformal arcs. 3 centers participated in both benchmark studies. Between 2016 and 2022, the CK platform had a 14% increase in PCI and an 11% reduction in GI. EV PCI increased 16% and GI decreased 8%. Changes in GK plans were more variable.
TBL: In this SRS benchmarking study, SRS plan quality has improved since 2016 and was more consistent across platforms and centers. The metrics provided in the study provide a great benchmark to evaluate SRS plan quality against. | Paddick, Pract Radiat Oncol 2023
The Study: In 2016, the UK NHS conducted a benchmarking study for intracranial SRS. This study provides an updated evaluation of the latest technology. The SRS platforms included: GammaKnife with Lightning inverse planning, CyberKnife S7 with M6 MLC, Elekta Versa HD with Brainlab Elements, Varian TrueBeam with Brainlab Elements, and Varian Edge with HyperArc and Zap-X. Six benchmark cases from the 2016 study were used and a 7th case with 14 targets was added. These included a range of scenarios including brain metastasis, vestibular schwannoma, meningioma, and pituitary adenoma. Plan parameters and goals were pre-specified including the prescription dose, target coverage, OAR constraints, and gradient objectives. A 1mm PTV margin was used only when treating metastases with a C-arm LINAC but not in any other cases. All the platforms had adequate target coverage. Paddick conformity indices ranged from 0.700 to 0.896 (CyberKnife). Gradient indices (GI) ranged from 3.66 (GK) to 5.27 (HyperArc using 10X). The efficiency index ranged from ~42%-55% for 3 targets, 48%-60% for 7 targets, and 35% to 50% for 14 targets. The efficiency index is a newer measure of conformity, gradient, and mean target dose. It is calculated as the ratio of integral dose in the target (mean dose x volume) and integral dose to the 50% isodose volume. When it came to gradient index, beam energy appeared to have the greatest influence with lower energy platforms having the lowest GIs and vice versa for high beam energy. Another takeaway was that VMAT typically resulted in better conformity at the slight expense of higher gradient compared to platforms that used dynamic conformal arcs. 3 centers participated in both benchmark studies. Between 2016 and 2022, the CK platform had a 14% increase in PCI and an 11% reduction in GI. EV PCI increased 16% and GI decreased 8%. Changes in GK plans were more variable.
TBL: In this SRS benchmarking study, SRS plan quality has improved since 2016 and was more consistent across platforms and centers. The metrics provided in the study provide a great benchmark to evaluate SRS plan quality against. | Paddick, Pract Radiat Oncol 2023