Abstract
Purpose: To find methods for optimal usage of XVI (X-ray volume imaging) system in Elekta synergy linear accelerator with different field of views for same lesion in order to minimize patient dose due to imaging. Methods: 20 scans of 2 individual patients with ca sigmoid colon and ca lung were used in this study. Kilo voltage collimators with medium field of view were used as per the preset information. Images were reconstructed for another collimator with small field of view. The set up errors were evaluated with XVI software. Shift results of both methods were compared. Results: Variation in treatment set up errors with M20 and S20 collimators were ≤ 0.2 mm in translational and 0.3 0 in rotational shifts. Results showed almost equal translational and rotational shifts in both medium and small field of views with different collimators in all the scans. Visualization of target and surrounding structures were good enough and sufficient for XVI auto matching. Conclusion: Imaging with small field of view results less patient dose compared with medium or large field of views. It is Suggestible to use collimators with small field of view wherever possible. In this study, collimators with small field of view were sufficient for both patients though the preset information indicated medium field of view. But, it always depends on the area required for matching purpose. So, individual selection is important than preset information in the XVI system.
Highlights
One of the main requirements for the tumor control in radiotherapy is, reproducible positioning of the patient in the treatment room as per the prior plan
Linear accelerator consists of an extendable X-ray tube fitted to the drum of it at orthogonal to MV treatment source and a motorized amorphous-Silicon flat imager panel opposite to it, is capable for this type of volumetric comparison
The X-ray Volumetric Imaging system (XVI) is sharing a common axis of rotation with the MV treatment source
Summary
One of the main requirements for the tumor control in radiotherapy is, reproducible positioning of the patient in the treatment room as per the prior plan This can be checked and corrected with the imaging systems integrated with the treatment delivery system.[1] Cone beam computerised tomography (CBCT) integrated with linear accelerator for patient position verification is one of the prime methods in image guidance.[2]. Linear accelerator consists of an extendable X-ray tube fitted to the drum of it at orthogonal to MV treatment source and a motorized amorphous-Silicon flat imager panel opposite to it, is capable for this type of volumetric comparison. This kV imaging system is called X-ray Volumetric Imaging system (XVI). To handle raw cone-beam data, the most widely used algorithm for image reconstruction is a Feldkamp-type algorithm 3, 4 which is the case for the XVI system
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