Highlights
- •An overall improvement in image quality was obtained for the 70 keV PMR.
- •iMAR method provided best reduction of metal artefacts observed on CT.
- •Combining the 70 keV PMR with the iMAR bring benefits for CT use in RT.
Abstract
Purpose
To evaluate the use of pseudo-monoenergetic reconstructions (PMR) from dual-energy
computed tomography, combined with the iterative metal artefact reduction (iMAR) method.
Methods
Pseudo-monoenergetic CT images were obtained using the dual-energy mode on the Siemens
Somatom Definition AS scanner. A range of PMR combinations (70–130 keV) were used
with and without iMAR. A Virtual Water™ phantom was used for quantitative assessment
of error in the presence of high density materials: titanium, alloys 330 and 600.
The absolute values of CT number differences (AD) and normalised standard deviations
(NSD) were calculated for different phantom positions. Image quality was assessed
using an anthropomorphic pelvic phantom with an embedded hip prosthesis. Image quality
was scored blindly by five observers.
Results
AD and NSD values revealed differences in CT number errors between tested sets. AD
and NSD were reduced in the vicinity of metal for images with iMAR (p < 0.001 for
AD/NSD). For ROIs away from metal, with and without iMAR, 70 keV PMR and pCT AD values
were lower than for the other reconstructions (p = 0.039). Similarly, iMAR NSD values
measured away from metal were lower for 130 keV and 70 keV PMR (p = 0.002). Image
quality scores were higher for 70 keV and 130 keV PMR with iMAR (p = 0.034).
Conclusion
The use of 70 keV PMR with iMAR allows for significant metal artefact reduction and
low CT number errors observed in the vicinity of dense materials. It is therefore
an attractive alternative to high keV imaging when imaging patients with metallic
implants, especially in the context of radiotherapy planning.
Keywords
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Article info
Publication history
Published online: August 17, 2020
Accepted:
August 7,
2020
Received in revised form:
July 23,
2020
Received:
May 7,
2020
Identification
Copyright
© 2020 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
