Abstract
In recent years different metal artifact reduction (MAR) methods have been developed for computed tomography (CT). These methods have only recently been introduced for positron emission tomography/computed tomography (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. Methods The phantom consisted of two types of hip prostheses in a solution of 18F-flurodeoxyglucose (18F-FDG) and water. 18F-FDG PET/CT scans of 14 patients with metal implants (either dental implants, hip prostheses, shoulder prostheses or pedicle screws) and 68Ga-labeled prostate-specific membrane antigen (68Ga-PSMA) PET/CT scans of 7 patients with hip prostheses were scored by two 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 an mCT PET/CT scanner (Siemens Healthcare). The standard low-dose CTs were processed with the iMAR algorithm. The PET data were reconstructed using attenuation correction provided by both standard CT and iMAR-processed CT. Results For the phantom scans cold artifacts were visible on the PET image. There was a 30% deficit in 18F-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 standardized uptake value (SUV) increase or decrease depended on the type of metal artifact. The mean difference in absolute values of SUVmean of the lesions was 3.5±3.3%. Conclusion 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.
- Copyright © 2017 by the Society of Nuclear Medicine and Molecular Imaging, Inc.