Table 1.
Patient Demographics and Imaging Parameters of the 46 subjects included in the analysis.
Data is given ± standard deviation.
Fig 1.
Qualitative image analysis is based on 5 point Likert scales taking into account the degree of artefact as well as diagnostic impact on adjacent and distant tissue for both hip prosthesis (A to D) and dental implants (E to H).
A and E) massive artefacts (4 points), B and F) pronounced streaks (3 points), C and G) intermediate streaks (2 points), D and H) minimal streaks (1 point).
Fig 2.
Applied method for quantitative image analysis with A) polygon placement around metallic implant to extract circular pixel information and B) results of discrete Fourier transform.
Analysing amplitudes of low frequencies (red box) permits information on the degree of metal artefacts.
Table 2.
Cohens kappa show interrater reliability of MAR methods stratified by hip prosthesis and dental implants.
NOMAR = no metal artefact reduction, DEMAR = Dual-energy metal artefact reduction, IMAR = iterative metal artefact reduction, IMAR+DEMAR = combination of IMAR and DEMAR.
Fig 3.
Examples of hip prosthesis in bone window (A-D) and dental implants in abdominal window (E-H).
Incremental effect of DEMAR in combination with IMAR inverts remaining high contrast artefacts of IMAR and allows a better evaluation of the prosthesis (red circles in C and D). In terms of contrast enhanced images, DEMAR results in contrast attenuation (red circles in F and G). NOMAR = no metal artefact reduction, DEMAR = Dual-energy metal artefact reduction, IMAR = iterative metal artefact reduction, IMAR+DEMAR = combination of IMAR and DEMAR.
Fig 4.
Bar-graphs demonstrating qualitative assessment of impact on metal artefacts of the different MAR approaches applied A) hip prosthesis and B) dental implants based on 5 point Likert scales.
NOMAR = no metal artefact reduction, DEMAR = Dual-energy metal artefact reduction, IMAR = iterative metal artefact reduction, IMAR+DEMAR = combination of IMAR and DEMAR.
Table 3.
Comparison of the means of qualitative (Likert scale) and quantitative (fourier coefficients) image evaluation of NOMAR, DEMAR, IMAR and IMAR+DEMAR at hip prosthesis.
NOMAR = no metal artifact reduction, DEMAR = Dual-energy metal artifact reduction, IMAR = iterative metal artifact reduction, IMAR+DEMAR = combination of IMAR and DEMAR, p = p value, n.s. = non-significant.
Table 4.
Comparison of the means of qualitative (Likert scale) and quantitative (fourier coefficients) image evaluation of NOMAR, DEMAR, IMAR and IMAR+DEMAR at dental implants.
NOMAR = no metal artifact reduction, DEMAR = Dual-energy metal artifact reduction, IMAR = iterative metal artifact reduction, IMAR+DEMAR = combination of IMAR and DEMAR, p = p value, n.s. = non-significant.
Fig 5.
Bar-graphs demonstrating the association between the different MAR approaches applied and quantitative reduction of metal artefacts (averaged sums of amplitudes of the lower frequencies) representing streaking artefacts from hip prosthesis and metallic dental implants.
NOMAR = no metal artefact reduction, DEMAR = dual-energy metal artefact reduction, IMAR = iterative metal artefact reduction, IMAR+DEMAR = sequential combination of iterative and dual-energy metal artefact reduction.