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Commissioning of the Leksell Gamma Knife ® Icon™
Author(s) -
Zeverino Michele,
Jaccard Maud,
Patin David,
Ryckx Nick,
Marguet Maud,
Tuleasca Constantin,
Schiappacasse Luis,
Bourhis Jean,
Levivier Marc,
Bochud Francois O.,
Moeckli Raphaël
Publication year - 2017
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.12052
Subject(s) - isocenter , nuclear medicine , dosimetry , image quality , ionization chamber , materials science , cone beam computed tomography , physics , optics , imaging phantom , medicine , computed tomography , ionization , computer science , radiology , artificial intelligence , ion , quantum mechanics , image (mathematics)
Purpose The Leksell Gamma Knife ( LGK ) Icon has been recently introduced to provide Gamma Knife technology with frameless stereotactic treatments which use an additional cone‐beam CT ( CBCT ) imaging system and a motion tracking system ( IFMM , Intra‐Fraction Motion Management). The system was commissioned for the treatment unit itself as well as the imaging system. Methods The LGK Icon was calibrated using an A1 SL ionization chamber. EBT 3 radiochromic films were employed to independently check the machine calibration, to measure the relative output factors ( ROFs ) and to collect dose distributions. Coincidence between CBCT isocenter and radiological focus was evaluated by means of EBT 3 films. CBCT image quality was investigated in terms of spatial resolution, contrast‐to‐noise ratio ( CNR ), and uniformity for the two presets available (low dose and high dose). Computed Tomography Dose Index ( CTDI ) was also measured for both presets. Results The absolute dose rate of the LGK Icon was 3.86 ± 0.09 Gy/min. This result was confirmed by EBT 3 readings. ROF were found to be 0.887 ± 0.035 and 0.797 ± 0.032 for the 8 mm and 4 mm collimators, respectively, which are within 2% of the Monte Carlo‐derived ROF values. Excellent agreement was found between calculated and measured dose distribution with the gamma pass rate >95% of points for the nine dose distributions analyzed with 3%/1 mm criteria. CBCT isocenter was found to be within 0.2 mm with respect to radiological focus. Image quality parameters were found to be well within the manufacturer's specifications with the high‐dose preset being superior in terms of CNR and uniformity. CTDI values were 2.41 mG y and 6.32 mG y, i.e. −3.6% and 0.3% different from the nominal values for the low‐dose and high‐dose presets, respectively. Conclusions The LGK Icon was successfully commissioned for clinical use. The use of the EBT 3 to characterize the treatment unit was demonstrated to be feasible. The CBCT imaging system operates well within the manufacturer's specifications and provides good geometrical accuracy.