Abstract
PurposeTo compare and combine dual-energy based and iterative metal artefact reduction on hip prosthesis and dental implants in CT.Material and MethodsA total of 46 patients (women:50%,mean age:63±15years) with dental implants or hip prostheses (n = 30/20) were included and examined with a second-generation Dual Source Scanner. 120kV equivalent mixed-images were derived from reconstructions of the 100/Sn140kV source images using no metal artefact reduction (NOMAR) and iterative metal artefact reduction (IMAR). We then generated monoenergetic extrapolations at 130keV from source images without IMAR (DEMAR) or from source images with IMAR, (IMAR+DEMAR). The degree of metal artefact was quantified for NOMAR, IMAR, DEMAR and IMAR+DEMAR using a Fourier-based method and subjectively rated on a five point Likert scale by two independent readers.ResultsIn subjects with hip prosthesis, DEMAR and IMAR resulted in significantly reduced artefacts compared to standard reconstructions (33% vs. 56%; for DEMAR and IMAR; respectively, p<0.005), but the degree of artefact reduction was significantly higher for IMAR (all p<0.005). In contrast, in subjects with dental implants only IMAR showed a significant reduction of artefacts whereas DEMAR did not (71%, vs. 8% p<0.01 and p = 0.1; respectively). Furthermore, the combination of IMAR with DEMAR resulted in additionally reduced artefacts (Hip prosthesis: 47%, dental implants 18%; both p<0.0001).ConclusionIMAR allows for significantly higher reduction of metal artefacts caused by hip prostheses and dental implants, compared to a dual energy based method. The combination of DE-source images with IMAR and subsequent monoenergetic extrapolation provides an incremental benefit compared to both single methods.
Highlights
Since the beginning of the development of computed tomography (CT), metallic implants, such as dental hardware, joint prostheses and osteosynthetic material have resulted in substantial artefacts with subsequent limited ability to evaluate adjacent anatomic structures [1]
In subjects with hip prosthesis, DEMAR and iterative metal artefact reduction (IMAR) resulted in significantly reduced artefacts compared to standard reconstructions (33% vs. 56%; for DEMAR and IMAR; respectively, p
In subjects with dental implants only IMAR showed a significant reduction of artefacts whereas DEMAR did not (71%, vs. 8% p
Summary
Since the beginning of the development of computed tomography (CT), metallic implants, such as dental hardware, joint prostheses and osteosynthetic material have resulted in substantial artefacts with subsequent limited ability to evaluate adjacent anatomic structures [1]. This diagnostic challenge is relevant as the demographic development is associated with an increasing prevalence of joint replacements and other implants [2]. In patients with metallic implants it is desirable to enable sufficient evaluation of the prosthesis itself, the interface between implant and bone and the surrounding soft tissue, regarding clinical questions such as fractures, implant loosening, hematoma, inflammation and malignancies [3]. Beam hardening provokes insufficient soft tissue contrast in terms of dark bands [4]
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