Abstract
The Gamma Knife Icon comes with an integrated cone‐beam CT (CBCT) for image‐guided stereotactic treatment deliveries. The CBCT can be used for defining the Leksell stereotactic space using imaging without the need for the traditional invasive frame system, and this allows also for frameless thermoplastic mask stereotactic treatments (single or fractionated) with the Gamma Knife unit. In this study, we used an in‐house built marker tool to evaluate the stability of the CBCT‐based stereotactic space and its agreement with the standard frame‐based stereotactic space. We imaged the tool with a CT indicator box using our CT‐simulator at the beginning, middle, and end of the study period (6 weeks) for determining the frame‐based stereotactic space. The tool was also scanned with the Icon's CBCT on a daily basis throughout the study period, and the CBCT images were used for determining the CBCT‐based stereotactic space. The coordinates of each marker were determined in each CT and CBCT scan using the Leksell GammaPlan treatment planning software. The magnitudes of vector difference between the means of each marker in frame‐based and CBCT‐based stereotactic space ranged from 0.21 to 0.33 mm, indicating good agreement of CBCT‐based and frame‐based stereotactic space definition. Scanning 4‐month later showed good prolonged stability of the CBCT‐based stereotactic space definition.
Highlights
Stereotactic radiosurgery (SRS) delivers a high dose of radiation to a target while sparing healthy structures, and this mandates precise localization
This study focused on the stability of the CBCTbased stereotactic space definition and its agreement with the standard frame-based stereotactic space definition, as one element in the
There was no statistical significant difference (P-value > 0.05 using t-test) in determining the marker positions in cone-beam CT (CBCT) images taken using the two different scanning preset settings (CTDI 6.3 mGy vs CTDI 2.5 mGy). This is expected in our case as the ballbearings are identified in either scanning preset because of their high contrast with the surrounding air, and as the CBCT to Leksell coordinates calibration is independent of scanning preset used
Summary
Stereotactic radiosurgery (SRS) delivers a high dose of radiation to a target while sparing healthy structures, and this mandates precise localization. Gamma Knife SRS treats intracranial lesions and involves localizing the target coordinates based on an invasive frame fixed to the patient skull.[1] With the advances in image-guided radiotherapy, the possibility of localizing targets using images allows for noninvasive frameless stereotactic radiosurgery, as well as for fractionated stereotactic radiotherapy. The new Gamma Knife model, Leksell Gamma Knifeâ IconTM, has been recently introduced and includes a cone-beam CT (CBCT) which can be used to define the 3D stereotactic coordinate space without the need for an invasive frame system. The CBCT can be used to define the stereotactic space coordinates for either G-frame treatments or the new frameless thermoplastic mask system. This study focused on the stability of the CBCTbased stereotactic space definition and its agreement with the standard frame-based stereotactic space definition, as one element in the
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