Purpose: To Share useful clinical experiences with Gamma Knife and non-Gamma Knife users alike
Methods: Clinical data from models B, 4C, PERFEXTION and ICON Gamma Knife units at Northwestern Memorial Hospital were used to extract the number of patients and fractions treated with each model. For ICON unit, the data were also separated into frame-based and frameless (mask)-based cases to illustrate the current practice.
Results: Northwestern Memorial installed the Model B Gamma Knife unit in 1998, which was then successively upgraded to 4C, PERFEXION and to ICON in 2019. Approximately 4,000 patients were treated in the past 20 years. The data show an appreciable increase of caseloads/year by +40.0% and treatment fractions/year by as much as +116.2% in the first 15 months of ICON uses, as compared to the most recent model PERFEXION unit. These increases are ascribed to the capability of ICON units to provide mask-based fractionated treatments. Currently, slightly more patients are treated with mask-base system (56.4%) with most patients being treated with 1, 3 or 5 fractions, averaging 2.0 fractions per patient. The patient disease site distribution was also tabulated. On the other hand, due to the gating nature of the mask-based treatments, the treatment time per treatment could increase as much as +75% and highly depends on patient’s conditions. Discussions were also presented on new hardware and treatment planning software features associated with ICON upgrade.
Conclusion: Introduction of optional frameless treatment with on-board CBCT and Infrared gating system, ICON unit enables many more intracranial patients to be treated and thus leads to significant higher patient caseload albeit at the expense of possible longer treatment time.
Gamma Knife, Stereotactic Radiosurgery, Gating