Plan Quality Comparison Between Hippocampus-Sparing Whole-Brain Radiotherapy Treated With Halcyon and Tomotherapy Intensity-Modulated Radiotherapy

Abstract

Objective: Hippocampus-sparing whole-brain radiotherapy using Halcyon, an instrument dedicated to volumetric modulated arc therapy, has not been studied till date; hence, we aimed to examine whether it can meet the RTOG0933 criteria. Based on this, we compared Halcyon to Tomotherapy, which also uses an O-ring-type linear accelerator. Methods: This exploratory, experimental, and retrospective study used 5 sets of computed tomography images in the head area to investigate the planning target volume, hippocampal doses, and irradiation time. Calculations were performed from 1 to 4 arcs to determine the optimal number of arcs in the Halcyon plan, which were compared to those of Tomotherapy. Results: The Radiation Therapy Oncology Group 0933 criteria could not be satisfied in Halcyon with 1 arc. With 2 arcs, the condition Dmax<16 Gy was not satisfied for 1 case in the hippocampus. Since there were no significant differences between 3 and 4 arcs, including the irradiation time, 3 arcs were considered the best. We compared Halcyon at 3 arcs with tomotherapy and found that tomotherapy was inferior to Halcyon at D98%; however, it was superior to Halcyon in other dose parameters. In contrast, the irradiation time in Halcyon was overwhelmingly superior, with the irradiation time for Halcyon being 1/ninth the time for Tomotherapy. Conclusion: Halcyon was effective in handling hippocampus-sparing whole-brain radiotherapy. We believe that 3-arc radiation is best suited for this procedure. Although Halcyon was inferior to Tomotherapy in terms of dose distribution excluding D98%, it was overwhelmingly superior in terms of irradiation time.

Dosimetric performance evaluation of the Halcyon treatment platform for stereotactic radiotherapy: A pooled study

“…[32] Hence, the Halcyon linear accelerator cannot provide non-coplanar fields, which may lead to limitations in SRT implementations. [37,38] However, lateral head flexion can overcome the inability to design non-coplanar SRS plans and considerably increase beam entrance angles. It thus improves plan conformity and normal tissue sparing.…”

Dosimetric comparison of helical tomotherapy and volumetric modulated arc therapy in hippocampal avoidance whole‐brain radiotherapy

“…who compared the hippocampal avoidance effects of WBRT and PCI between HT plan and VMAT plan. However, the HT plan used small pitch and great MF in plan design, and the design time and overall implementation time were longer than those of the VMAT plan, which may bring some influences to the treatment of patients 37 …”

Treatment plan comparison for irradiation of multiple brain metastases with hippocampal avoidance whole brain radiotherapy and simultaneous integrated boost using the Varian Halcyon and the Elekta Synergy platforms

“…To date, there is no other study reporting on Halcyon`s performance for the treatment of HA-SIB+WBRT. In general there is only limited data and only two scientific papers reporting on the application of cerebral radiotherapy with the new linac accelerator [ 24 , 25 ]. Of particular note is the impressive efficiency of irradiation of HA-WBRT with the Halcyon demonstrated by Yokohama et al with a reduction in irradiation time of 1/9 compared to treatment with tomotherapy [ 25 ].…”

“…Beside the VMAT approach used in the underlying study other techniques exist for HA-WBRT, most notably IMRT and tomotherapy [ 9 ]. In general arc based delivery (VMAT) is faster than conventional IMRT and tomotherapy [ 25 , 27 ].…”