A motion-compensated cone-beam CT using electrical impedance tomography imaging

Abstract

Cone-beam CT (CBCT) is an imaging technique used in conjunction with radiation therapy. For example CBCT is used to verify the position of lung cancer tumours just prior to radiation treatment. The accuracy of the radiation treatment of thoracic and upper abdominal structures is heavily affected by respiratory movement. Such movement typically blurs the CBCT reconstruction and ideally should be removed. Hence motion-compensated CBCT has recently been researched for correcting image artefacts due to breathing motion. This paper presents a new dual-modality approach where CBCT is aided by using electrical impedance tomography (EIT) for motion compensation. EIT can generate images of contrasts in electrical properties. The main advantage of using EIT is its high temporal resolution. In this paper motion information is extracted from EIT images and incorporated directly in the CBCT reconstruction. In this study synthetic moving data are generated using simulated and experimental phantoms. The paper demonstrates that image blur, created as a result of motion, can be reduced through motion compensation with EIT.

Motion-compensated cone beam computed tomography using a conjugate gradient least-squares algorithm and electrical impedance tomography imaging motion data

“…Our 16 electrode EIT system in a LabVIEW environment based on National Instruments (NI) cards was used in this study [18]. Figure 2 shows the imaging capability of the EIT system used in this study; δ = 0.001 is a suitable choice for the regularization parameter here.…”

“…This can be achieved by updating the residual r into the problem iteratively. For motion-compensated CGLS, a motion compensation technique based on our previous report [18] was used. The weight matrix A is partitioned into sub-matrices to be shifted; its column appropriately applied according to a motion model to each measured projection.…”

“…Considering limited spatial resolution in EIT imaging the 'approximated motion compensation' is closer to EIT motion data. This has been investigated in previous study [18], where images with 10% error in motion data could sufficiently compensate for motion artefacts in CBCT images. For 'approximated motion compensation', matrix A was shifted by the motion signals extracted from EIT images for the relative projection.…”

“…the algebraic reconstruction technique (ART), simultaneous algebraic reconstruction technique (SART) and ordered-subset SART (OS-SART) are the methods of choice [13][14][15][16]. Furthermore, motion compensation has been combined with ART and SART [17,18].…”

“…In this paper, motion-compensated CGLS was developed and tested for the improvement of CBCT image reconstruction using one-fourth projection data. The motion-compensated CGLS was applied to the dual modality EIT-CBCT [18] by using the motion estimated from EIT images. A better performance of motion-compensated CBCT can be seen here due to the possibility of regularization terms that can be included in the CGLS scheme.…”