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SU‐E‐T‐530: Projection Image Correction for 4D VMAT‐CT
Author(s) -
Saotome N,
Kida S,
Onoe T,
Sasaki K,
Imae T,
Tanaka K,
Sakumi A,
Masutani Y,
Haga A,
Nakagawa K
Publication year - 2011
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 - 10.1118/1.3612492
Subject(s) - collimator , image quality , imaging phantom , nuclear medicine , multileaf collimator , projection (relational algebra) , maximum intensity projection , iterative reconstruction , physics , computer science , linear particle accelerator , beam (structure) , optics , medicine , artificial intelligence , image (mathematics) , radiology , algorithm , angiography
Purpose: A Volumetric Modulated Arc Therapy (VMAT) provides a reconstruction images from MV portal imaging, named as “VMAT‐CT”. The purpose of this presentation is to improve the image quality of four‐ dimensional (4D) VMAT CT by considering beam intensity and field‐size (output) factor. Methods: Sequential MV‐portal images during VMAT delivery were acquired using the iView software (Elekta). The gantry angle information was obtained by connecting the multi‐leaf collimator (MLC) shape derived from a portal image with that described in treatment log data via Elekta software protocol, iCom. After background correction and masking with a specific threshold value, a beam‐intensity correction was performed using the log data. Further, we introduced output‐factor correction in order to correct the intensity depending on the size of field of view (FOV). A respiratory signal was derived from simultaneous kV‐portal imaging orthogonal to MV imaging by using image‐based phase recognition technique. Synchronizing with kV ones, then, MV‐portal images were classified to corresponding breathing‐phase bins. Consequently, both 4D VMAT‐CT and 4D kV cone‐beam CT (CBCT) were reconstructed independently with conventional filtered‐back projection algorithm. Results: The beam‐intensity and field‐size corrections were reasonably applied in the 4D VMAT‐CT reconstruction. It was observed that the image quality of 4D VMAT‐CT was improved both in phantom study and clinical cases. Conclusions: The image quality of 4D VMAT‐CT was improved by considering the beam intensity and output factor. It is expected that the VMAT‐CT superimposed into the planning CT, pre‐, or in‐treatment kV CBCT provides a guarantee of irradiated region in actual treatment. This work was supported by JSPS, KAKENHI22791176.