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Keywords:
Artifacts, Radiation safety, Computer Applications-Detection, diagnosis, CT, Radioprotection / Radiation dose, Musculoskeletal system, Musculoskeletal bone
Authors:
L. Filograna1, M. la Torre1, N. Magarelli1, A. Leone1, R. D'Amico2, C. De Waure1, G. Calabrò1, M. Thali3, L. Bonomo1; 1Rome/IT, 2Roma (RM)/IT, 3Zurich/CH
DOI:
10.1594/ecr2016/C-0046
Aims and objectives
Background
CT is undoubtedly the most widely-used technique for investigating the skeleton,
basically due to the short scan times and the possibility of 2D and 3D reconstructions.
Nevertheless,
CT diagnostic capabilities are drammatically reduced when a metallic orthopedic implant is present in the field of view [1].
Such metal objects originate artifacts from quantum noise,
beam hardening and scattered radiation [2-4] that markedly reduce the tissue contrast and impair the proper visualization of the implant itself,
of the implant–bone interface and of the surrounding soft tissue.
Nevertheless,
in pre- and post-operative imaging,
an optimal display of these structures is crucial for the detection of complications following metallic device placements (e.
g.
implant fracture,
faults,
loosening and infections) [3-5].
Until a few years ago,
few methods had been proposed for reducing metal artifacts and improving the image quality in CT examinations,
and these were based mainly on adjustments of CT acquisition (higher milliampere/second and peak kilovoltage) or of the post-processing [1,
6-16]. In recent years,
dual-energy CT (DECT) has been shown to be a viable method for reducing metal artifacts [17].
In DECT scans,
the acquisition of two CT datasets with different x-ray spectra provides the possibility in the post-processing to extrapolate monoenergetic image reconstructions at a specific energy level [17].
Some clinical and post-mortem studies have demonstrated the superiority of DECT in reducing metallic artifacts in comparison with single-energy CT (SECT) [18-22].
Nevertheless,the exposure of patients to ionizing radiation common to all CT technologies can prove a burden in the setting of serial examinations before and after surgery.
On the other hand,
decreasing CT radiation dose by reducing tube voltages causes a consistent increase of the image noise.
For this reason,
low-dose CT scans have been used for body regions with a high intrinsic physical contrast,
such as the lungs.
Few studies in the literature reported on the outcomes of low-dose DECT,
particularly in evaluating urinary calculi [23-24] and in detecting bone bruises [25],
with exellent results.
Purpose
Considering the promising results reported in the literature about the superiority of DECT in reducing metal artifact against SECT [18-22],
the aim of this ex-vivo study was to determine if this advantage offered by DECT techniques is maintained also with low dose scans in comparison with dose-neutral DECT,
dose-neutral SECT,
and dose-reduced SECT.