Towards patient connected imaging with ACROBEAT: Adaptive CaRdiac cOne BEAm computed Tomography

Abstract

Robotic C-arm Cone Beam Computed Tomography (CBCT) systems are playing an increasingly pivotal 6 role in interventional cardiac procedures and high precision radiotherapy treatments. One of the main 7 challenges in any form of cardiac imaging is mitigating the intrinsic motion of the heart, which causes 8 blurring and artefacts in the 3D reconstructed image. Most conventional 3D cardiac CBCT acquisition 9 techniques attempt to combat heart motion through retrospective gating techniques, whereby acquired 10 projections are sorted into the desired cardiac phase after the completion of the scan. However, this 11 results in streaking artefacts and unnecessary radiation exposure to the patient. Here, we present our 12 Adaptive CaRdiac cOne BEAm computed Tomography (ACROBEAT) acquisition protocol that uses 13 the patient's electrocardiogram (ECG) signal to adaptively regulate the gantry velocity and projection 14 time interval in real-time. It enables prospectively gated patient connected imaging in a single sweep of 15 the gantry. The XCAT digital software phantom was used to complete a simulation study to compare 16 ACROBEAT to a conventional multi-sweep retrospective ECG gated acquisition, under a variety of 17 different acquisition conditions. The effect of location and length of the acquisition window and total 18 number of projections acquired on image quality and total scan time were examined. Overall, 19 ACROBEAT enables up to a 5 times average improvement in the contrast-to-noise ratio, a 40% 20 reduction in edge response width and an 80% reduction in total projections acquired compared to 21 conventional multi-sweep retrospective ECG gated acquisition.

Dual cardiac and respiratory gated thoracic imaging via adaptive gantry velocity and projection rate modulation on a linear accelerator: A Proof‐of‐Concept Simulation Study

“…However, in our previous work developing and testing cardiac‐ and respiratory‐ only motion guided CBCT imaging protocols separately we investigated and characterized the performance of each protocol's ability to handle variations and irregularities in the patient's physiological signal being considered. That is, for cardiac‐only motion guided CBCT imaging we considered the effect of arrhythmias on image quality and scan time, while for respiratory‐only motion guided CBCT imaging we looked to encompass irregular breathing by examining 112 breathing traces from 24 lung cancer patients …”

“…. The details of the algorithms that will be used to determine the cardiac and respiratory acquisition windows for future experimental implementation, including how they are able to cope with variations and irregularities in the patient's physiological signals can be found in our previous studies …”

“…The details of the algorithms that will be used to determine the cardiac and respiratory acquisition windows for future experimental implementation, including how they are able to cope with variations and irregularities in the patient's physiological signals can be found in our previous studies. 13,14,17 Due to the weight and bulk of a conventional linac system, the maximum gantry rotation velocity is strictly limited and specified by the IEC standard 60601-2-1 of a maximum gantry velocity of 7°/s. Therefore, for the simulation scans completed it is assumed that the gantry is capable of rotating at a maximum acceleration of 9°/s 2 and velocity of 6°/s o remain within the maximum gantry rotation velocity limit, and acquires projections at a fixed framerate of 5.5 Hz.…”

“…Importantly, these methods have already been implemented on an Elekta Synergy linear accelerator (linac) for respiratory motion guided imaging, displaying significant improvements in the image quality for the same dose as well as enabling up to a 70% reduction in imaging dose for the same original image quality . Extending this concept to conduct cardiac motion guided imaging we have developed a gated CBCT imaging protocol, which regulates the gantry velocity and projection time interval in accordance with the patient's real‐time electrocardiogram (ECG), under breath hold conditions . Here, we look to combine these techniques to allow dual cardiac and respiratory gated thoracic CBCT imaging without breath hold, Fig.…”

“…16 Extending this concept to conduct cardiac motion guided imaging we have developed a gated CBCT imaging protocol, which regulates the gantry velocity and projection time interval in accordance with the patient's realtime electrocardiogram (ECG), under breath hold conditions. 17 Here, we look to combine these techniques to allow dual cardiac and respiratory gated thoracic CBCT imaging without breath hold, Fig. 1.…”