Impact of different metal artifact reduction techniques on attenuation correction in 18F-FDG PET/CT examinations

Abstract

Objective: To evaluate the impact of different metal artifact reduction (MAR) algorithms on Hounsfield unit (HU) and standardized uptake values (SUV) in a phantom setting and verify these results in patients with metallic implants undergoing oncological PET/CT examinations. Methods and materials: In this prospective study, PET-CT examinations of 28 oncological patients (14 female, 14 male, mean age 69.5 ± 15.2y) with 38 different metal implants were included. CT datasets were reconstructed using standard weighted filtered back projection (WFBP) without MAR, MAR in image space (MARIS) and iterative MAR (iMAR, hip algorithm). The three datasets were used for PET attenuation correction. SUV and HU measurements were performed at the site of the most prominent bright and dark band artifacts. Differences between HU and SUV values across the different reconstructions were compared using paired t-tests. Bonferroni correction was used to prevent alpha-error accumulation (p < 0.017). Results: For bright band artifacts, MARIS led to a non-significant mean decrease of 12.0% (345 ± 315 HU) in comparison with WFBP (391 ± 293 HU), whereas iMAR led to a significant decrease of 68.3% (125 ± 185 HU, p < 0.017). For SUVmean, MARIS showed no significant effect in comparison with WFBP (WFBP: 0.99 ± 0.40, MARIS: 0.96 ± 0.39), while iMAR led to a significant decrease of 11.1% (0.88 ± 0.35, p < 0.017). Similar results were observed for dark band artifacts. Conclusion: iMAR significantly reduces artifacts caused by metal implants in CT and thus leads to a significant change of SUV measurements in bright and dark band artifacts compared with WFBP and MARIS, thus probably improving PET quantification. Advances in knowledge: The present work indicates that MAR algorithms such as iMAR algorithm in integrated PET/CT scanners are useful to improve CT image quality as well as PET quantification in the evaluation of tracer uptake adjacent to large metal implants. A detailed analysis of oncological patients with various large metal implants using different MAR algorithms in PET/CT has not been conducted yet.

Quantitative Effect of Metal Artefact Reduction on CT-Based Attenuation Correction in FDG PET/CT in Patients With Hip Prosthesis

“…It reduced the relative errors on the measurements to less than 5% of the reference activity. Our results con rm the better quantitative accuracy obtained with MAR in several phantom studies with hip replacements [7,9,11], a cardiac pacemaker [8], or dental metalwork [10]. The relative recovery by MAR of underestimated activity in our experiment was similar to that reported in underestimated areas [8,11].…”

“…Our results con rm the better quantitative accuracy obtained with MAR in several phantom studies with hip replacements [7,9,11], a cardiac pacemaker [8], or dental metalwork [10]. The relative recovery by MAR of underestimated activity in our experiment was similar to that reported in underestimated areas [8,11]. Some of the previous studies used custom made software [7][8][9], whereas others used iMAR [10,11], which is available commercially; to our knowledge no results have been published with Smart MAR.…”

“…That the predominant effect of MAR was to increase SUV in the areas surrounding the prostheses, does not contradict the possibility of overestimation of activity in particular areas around the prosthesis, such as have been reported clinically [5,8,11,14]. However, overestimation seems con ned to small regions, and would typically only be picked up by small (10 to 15 mm diameter) regions of interest as used in [8,11,14] and speci cally directed to bright streak artefacts. In the larger regions that we used, it is prevailed upon by underestimation.…”

“…Although these Metal Artefact Reduction (MAR) techniques have found widespread application in stand-alone CT, their use in PET/CT is still limited, in spite of evidence from phantom studies that they may improve quantitative accuracy [7][8][9][10]. This nding was extended to patients with a hip prosthesis: 30 patients reported in [8] and a further 16 belonging to a series of 28 oncological patients and not reported in isolation in [11]. Studying patients with dental implants, Nahmias at al.…”

The Link between Cytogenetics/Genomics and Imaging Patterns of Relapse and Progression in Patients with Relapsed/Refractory Multiple Myeloma: A Pilot Study Utilizing 18F-FDG PET/CT

“…The current pilot study had several limitations: (1) In our study, we selected 18F-FDG PET/CT scans as a candidate parameter to elucidate the link between cytogenetics/genomics and imaging patterns in RRMM. While 18F-FDG clearly is the standard of reference tracer in nuclear imaging of MM, scan results might be influenced by different factors, such as expression levels of hexokinase-2 and glucose transporter, as well as hyperglycemia, and false-positive results due to infection, chronic inflammation, metallic implants, surgery, and fracture healing can occur [ 2 , 19 , 20 , 21 , 22 ]. In this context, the hexokinase-2 expression is increased in the HY and PR molecular subgroup [ 19 ].…”