SU-E-J-147: Quantitative Analysis of 2.5 MV Portal Imaging Performance Compared to KV and 6MV Portal Imaging On the Novel Edge LINAC

Authors


Abstract

Purpose:

To quantitatively evaluate the performance of 2.5 MV imaging compared to traditional kV and 6MV imaging on the new Edge LINAC (Varian

Methods:

The high and low contrast resolution and contrast-tonoise ratios of kV, 2.5MV, and 6MV portal imaging were evaluated using Las Vegas, Leeds, CIRS torso, Rando torso, and BrainLab pelvis phantoms. Different thicknesses of solid water were added at both sides of phantom to simulate and assess the imaging characteristics associated with increased scatter in larger patients. The contrast-to-noise ratios of bone-to-soft tissue were obtained from aforementioned phantoms.

Results:

The 2.5 MV portal imaging resolved all objects in the Las Vegas phantom except the smallest object. 6 MV imaging couldn' t image three smallest objects. From the Leeds phantom, kV, 2.5 MV, and 6 MV imaging achieve 2.24, 1.4, and 1.25 LP/mm with no additional slabs, respectively. With 10 cm slabs added, resolutions deteriorate to 1.6, 1.25, and 0.7 LP/mm. In low contrast detectability, kV, 2.5 MV, and 6 MV imaging visualize 18, 18, and 15 different-contrast objects in total. With 10cm slab added, they imaged 12, 15, and 8 objects. CIRS phantom CNRs of bone-to-soft tissue were 10, 27, and 17 for KV, 2.5 MV, and 6 MV, respectively with no slab added. Rando phantom CNRs were 11, 8, and 7 and similarly CNRs from the BrainLab pelvis phantom were 9, 13, and 11. With additional slab, KV imaging CNRs degraded much more than those of 2.5 MV and 6 MV imaging.

Conclusion:

In this study, we evaluated kV, 2.5 MV and 6 MV imaging using various phantoms. The 2.5 MV imaging shows better imaging performance at large phantom configurations in terms of high and low contrast resolutions and CNRs. We believe that the 2.5 MV portal imaging will be the next trend in portal imaging, especially for SRS/SBRT patient localization.

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