Metal artifact reduction by monoenergetic extrapolation of dual-energy CT in patients with metallic implants

Lee, Ka Yin Gregory; Cheng, Hei Man Joyce; Chu, Chi Yeung; Tam, Chi Wai Annie; Kan, WK

doi:10.1177/2309499019851176

Cited by 19 publications

(17 citation statements)

References 20 publications

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“…Mild impairment was observed in ND as well as in Sn LD protocols because of restrictions due to metal artifacts that were similarly displayed in ND and Sn LD protocols. The potential of tin filter-based protocols without dose reduction to reduce metal artifacts has already been described by Hackenbroch et al 18 Other effective metal artifact reduction techniques described in the literature, [30][31][32][33][34][35] such as DE, virtual monoenergetic CT images (VMI), and postprocessing with iterative metal artifact reduction (IMAR) software, showed disadvantages compared with the tin filter technique. 18 The most common described disadvantages of CT images postprocessed with IMAR and VMI were the generation of novel artifacts by IMAR 33,[36][37][38] and the "blurring" of osseous structures in VMI.…”

Section: †Anovamentioning

confidence: 99%

Low-Dose CT Imaging of the Pelvis in Follow-up Examinations—Significant Dose Reduction and Impact of Tin Filtration

et al. 2022

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Objectives: Low-dose (LD) computed tomography (CT) is still rarely used in musculoskeletal (MSK) radiology. This study evaluates the potentials of LD CT for follow-up pelvic imaging with special focus on tin filtration (Sn) technology for normal and obese patients with and without metal implants. Materials and Methods: In a phantom study, 5 different LD and normal-dose (ND) CT protocols with and without tin filtration were tested using a normal and an obese phantom. Iterative reconstruction (IR) and filtered back projection (FBP) were used for CT image reconstruction. In a subsequent retrospective patient study, ND CT images of 45 patients were compared with follow-up tin-filtered LD CT images with a 90% dose reduction. Sixty-four percent of patients contained metal implants at the follow-up examination. Computed tomography images were objectively (image noise, contrast-to-noise ratio [CNR], dose-normalized contrast-to-noise ratio [CNRD]) and subjectively, using a 6-point Likert score, evaluated. In addition, the figure of merit was calculated. For group comparisons, paired t tests, Wilcoxon signed rank test, analysis of variance, or Kruskal-Wallis tests were used, where applicable. Results: The LD Sn protocol with 67% dose reduction resulted in equal values in qualitative (Likert score) and quantitative image analysis (image noise) compared with the ND protocol in the phantom study. For follow-up examinations, dose could be reduced up to 90% by using Sn LD CT scans without impairment in the clinical study. However, metal implants resulted in a mild impairment of Sn LD as well as ND CT images. Cancellous bone (P < 0.001) was assessed worse and cortical bone ( P = 0.063) equally in Sn LD CT images compared with ND CT images. Figure of merit values were significant ( P ≤ 0.02) lower and hence better in Sn LD as in ND protocols. Obese patients benefited in particular from tin filtration in LD MSK imaging in terms of image noise and CNR ( P ≤ 0.05). Conclusions: Low-dose CT scans with tin filtration allow maximum dose reduction while maintaining high image quality for certain clinical purposes, for example, follow-up examinations, especially metal implant position, material loosening, and consolidation controls. Overweight patients benefit particularly from tin filter technology. Although metal implants decrease image quality in ND as well as in Sn LD CT images, this is not a relevant limitation for assessability.

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Section: †Anovamentioning

confidence: 99%

Low-Dose CT Imaging of the Pelvis in Follow-up Examinations—Significant Dose Reduction and Impact of Tin Filtration

et al. 2022

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“…71 Dual-energy and megavoltage CT can also be helpful in this regard. [73][74][75][76][77] The contour and override solutions are the most commonly used methods. A structure of the high-density object is created with the TPS with an assigned HU.…”

Section: C High-atomic Number Materials In Proton Beamsmentioning

confidence: 99%

“…Solutions proposed to correct these artifacts and minimize the resulting uncertainties include contour and override suppression algorithms, 72 and the incorporation of megavoltage CT for imaging 71 . Dual‐energy and megavoltage CT can also be helpful in this regard 73–77 . The contour and override solutions are the most commonly used methods.…”

Section: Ancillary Devices and Materialsmentioning

confidence: 99%

Clinical commissioning of intensity‐modulated proton therapy systems: Report of AAPM Task Group 185

Farr¹,

Moyers²,

Allgower

et al. 2020

Medical Physics

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Proton therapy is an expanding radiotherapy modality in the United States and worldwide. With the number of proton therapy centers treating patients increasing, so does the need for consistent, high-quality clinical commissioning practices. Clinical commissioning encompasses the entire proton therapy system's multiple components, including the treatment delivery system, the patient positioning system, and the image-guided radiotherapy components. Also included in the commissioning process are the x-ray computed tomography scanner calibration for proton stopping power, the radiotherapy treatment planning system, and corresponding portions of the treatment management system. This commissioning report focuses exclusively on intensitymodulated scanning systems, presenting details of how to perform the commissioning of the proton therapy and ancillary systems, including the required proton beam measurements, treatment planning system dose modeling, and the equipment needed.

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“…Because varying material composition alters energy-dependent attenuation of X-rays beams, the two datasets will display different attenuations profiles. The VMS image can be reconstructed and calculated with different photon energy levels between the spectrum from 40 to 190 keV with the help of monoenergetic extrapolation 12,13 . The VMS images have the potential to reduce beam hardening artefacts and ascertain the narrow energy range of radiation produced by the X-ray sourcemeasured in kiloelectron volts (keV) 6 .…”

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confidence: 99%

Metal artefact reduction of different alloys with dual energy computed tomography (DECT)

Vellarackal

Kaim

2021

Sci Rep

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To evaluate the influence of dual-energy CT (DECT) and Virtual monochromatic spectral (VMS) imaging on: (1) the artefact size of geometrically identical orthopaedic implants consisting of three different compositions and (2) the image quality of the surrounding bone, three similar phantoms—each featuring one femoral stem composed of either titanium, chrome-cobalt or stainless steel surrounded by five calcium pellets (200 mg hydroxyapatite/calcium carbonate) to simulate bony tissue and one reference pellet located away from the femoral stem—were built. DECT with two sequential scans (80 kVp and 140 kVp; scan-to-scan technique) was performed, and VMS images were calculated between 40 and 190 keV. The artefact sizes were measured volumetrically by semiautomatic selection of regions of interest (ROIs), considering the VMS energies and the polychromatic spectres. Moreover, density and image noise within the pellets were measured. All three phantoms exhibit artefact size reduction as energy increases from 40 to 190 keV. Titanium exhibited a stronger reduction than chrome-cobalt and stainless steel. The artefacts were dependent on the diameter of the stem. Image quality increases with higher energies on VMS with a better depiction of surrounding structures. Monoenergetic energies 70 keV and 140 keV demonstrate superior image quality to those produced by spectral energies 80 kVp and 140 kVp.

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Metal artifact reduction by monoenergetic extrapolation of dual-energy CT in patients with metallic implants

Cited by 19 publications

References 20 publications

Low-Dose CT Imaging of the Pelvis in Follow-up Examinations—Significant Dose Reduction and Impact of Tin Filtration

Low-Dose CT Imaging of the Pelvis in Follow-up Examinations—Significant Dose Reduction and Impact of Tin Filtration

Clinical commissioning of intensity‐modulated proton therapy systems: Report of AAPM Task Group 185

Metal artefact reduction of different alloys with dual energy computed tomography (DECT)

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