Metal Artifact Reduction of CT Scans to Improve PET/CT

Abstract

In recent years, different metal artifact reduction methods have been developed for CT. These methods have only recently been introduced for PET/CT even though they could be beneficial for interpretation, segmentation, and quantification of the PET/CT images. In this study, phantom and patient scans were analyzed visually and quantitatively to measure the effect on PET images of iterative metal artifact reduction (iMAR) of CT data. The phantom consisted of 2 types of hip prostheses in a solution ofF-FDG and water. F-FDG PET/CT scans of 14 patients with metal implants (either dental implants, hip prostheses, shoulder prostheses, or pedicle screws) andGa-labeled prostate-specific membrane antigen (Ga-PSMA) PET/CT scans of 7 patients with hip prostheses were scored by 2 experienced nuclear medicine physicians to analyze clinical relevance. For all patients, a lesion was located in the field of view of the metal implant. Phantom and patients were scanned in a PET/CT scanner. The standard low-dose CT scans were processed with the iMAR algorithm. The PET data were reconstructed using attenuation correction provided by both standard CT and iMAR-processed CT. For the phantom scans, cold artifacts were visible on the PET image. There was a 30% deficit inF-FDG concentration, which was restored by iMAR processing, indicating that metal artifacts on CT images induce quantification errors in PET data. The iMAR algorithm was useful for most patients. When iMAR was used, the confidence in interpretation increased or stayed the same, with an average improvement of 28% ± 20% (scored on a scale of 0%-100% confidence). The SUV increase or decrease depended on the type of metal artifact. The mean difference in absolute values of SUV of the lesions was 3.5% ± 3.3%. The iMAR algorithm increases the confidence of the interpretation of the PET/CT scan and influences the SUV. The added value of iMAR depends on the indication for the PET/CT scan, location and size/type of the prosthesis, and location and extent of the disease.

18F-FDG PET for Diagnosing Infections in Prosthetic Joints

“…29 CT-based PET attenuation correction is susceptible to errors where artifacts occur, particularly in the vicinity of metal implants. 30,31 This can result in underestimation and overestimation of 18 F-FDG uptake. 30,31 There has been recent interest in the use of iterative metal artifact reduction of CT data, which improves PET image quality around prostheses.…”

“…30,31 This can result in underestimation and overestimation of 18 F-FDG uptake. 30,31 There has been recent interest in the use of iterative metal artifact reduction of CT data, which improves PET image quality around prostheses. 30,31…”

“…30,31 There has been recent interest in the use of iterative metal artifact reduction of CT data, which improves PET image quality around prostheses. 30,31…”

Breathing and metal artefact reduction in combined PET/CT imaging

“…The iMAR CT has an important impact on PET attenuation correction, which not only resulted in a more accurate quantification of radiopharmaceutical uptake in lesions located near the metal implant, but also in an increase of confidence in the interpretation of the PET/CT images by the physicians. In conclusion, the iMAR algorithm benefits image reconstruction in different types of metal implants, tracers and for different indications [28]. This can have important effects on clinical management of patients, including diagnosis and staging, radiotherapy planning, and response monitoring.…”

“…Resolution modelling or PSF modelling takes into account these effects during image reconstruction [6]. However, PSF modelling can also be applied as a post-reconstruction deconvolution [28]. The first method has been implemented by Siemens (HD) and GE (SharpIR), while the second method is used by Philips, as can be seen in Table 2.1.…”