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Characterization and Short-Term Stability of Dose and Image Quality Parameters of the Gamma Knife Iconâ„¢ KV-CBCT Imaging System

D Wieczorek*, V Mishra , R Kotecha , M Hall , A Gutierrez , Miami Cancer Institute, Miami, FL


(Tuesday, 7/31/2018) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 5

Purpose: The purpose of this study was to characterize image quality parameters and the computed tomography dose index (CTDI) of the Gamma Knife Icon kV-CBCT and quantify the short-term stability of these parameters.

Methods: Baseline dose and image quality parameters were acquired during the commissioning of the Gamma Knife Icon. Commissioning and acceptance tests were performed following recommended protocols. Measurements were taken using: Gammex CTDI head phantom, RaySafe Xi CT Detector, and CatPhan 503 phantom. Spatial resolution, Contrast to Noise Ratio (CNR), and Uniformity were measured using the CatPhan 503 phantom and following Elekta’s protocol. CTDI was measured using the head phantom and a calibrated 10cm pencil chamber placed on a custom head rest on top of the Gamma Knife mask adapter. CTDI and imaging measurements were acquired periodically to determine the stability of the system

Results: Results for the CTDI measurements listed in Table 1 show a mean CTDI value of 2.70±0.01 mGy and 6.70±0.02 mGy for the 2.5mGy CTDI and 6.3mGy CTDI settings, respectively—leading to a 7.5% and 7.8% difference between the measured and nominal values. Spatial resolution, CNR, and uniformity parameters are within expected values. Stability of the system over time is shown to be within 1% for the measured CTDI, as shown in Figure 1. The CBCT system was found to be operating within 10% of the mean value for all image quality parameters.

Conclusion: A validation study was performed for the image quality and dose parameters of the Gamma Knife Icon kV-CBCT. CTDI values were found to be within 8% of the nominal values and consistent to within 1% over 130 days. Image quality parameters were within 10% of mean value for the same time period.


Not Applicable / None Entered.


IM- Cone Beam CT: General (Most aspects)

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