Qualitative and Quantitative Comparison of PET/CT and PET/MR Imaging in Clinical Practice

Abstract

The aim of this study was to prospectively compare whole-body PET/MR imaging and PET/CT, qualitatively and quantitatively, in oncologic patients and assess the confidence and degree of inter-and intraobserver agreement in anatomic lesion localization. Methods: Fifty patients referred for staging with known cancers underwent PET/CT with low-dose CT for attenuation correction immediately followed by PET/MR imaging with 2-point Dixon attenuation correction. PET/CT scans were obtained according to standard protocols (56 6 20 min after injection of an average 367 MBq of 18 F-FDG, 150 MBq of 68 Ga-DOTATATE, or 333.8 MBq of 18 F-fluoro-ethyl-choline; 2.5 min/bed position). PET/MR was performed with 5 min/bed position. Three dual-accredited nuclear medicine physicians/radiologists identified the lesions and assigned each to an exact anatomic location. The image quality, alignment, and confidence in anatomic localization of lesions were scored on a scale of 1-3 for PET/CT and PET/MR imaging. Quantitative analysis was performed by comparing the standardized uptake values. Intraclass correlation coefficients and the Wilcoxon signed-rank test were used to assess intra-and interobserver agreement in image quality, alignment, and confidence in lesion localization for the 2 modalities. Results: Two hundred twenty-seven tracer-avid lesions were identified in 50 patients. Of these, 225 were correctly identified on PET/CT and 227 on PET/MR imaging by all 3 observers. The confidence in anatomic localization improved by 5.1% when using PET/MR imaging, compared with PET/CT. The mean percentage interobserver agreement was 96% for PET/CT and 99% for PET/MR imaging, and intraobserver agreement in lesion localization across the 2 modalities was 93%. There was 10% (5/50 patients) improvement in local staging with PET/MR imaging, compared with PET/CT. Conclusion: In this first study, we show the effectiveness of whole-body PET/MR imaging in oncology. There is no statistically significant difference between PET/MR imaging and PET/CT in respect of confidence and degree of inter-and intraobserver agreement in anatomic lesion localization. The PET data on both modalities were similar; however, the observed superior soft-tissue resolution of MR imaging in head and neck, pelvis, and colorectal cancers and of CT in lung and mediastinal nodal disease points to future tailored use in these locations.

PET/MRI: Reliability/Reproducibility of SUV Measurements

“…In most of these studies, a same-day protocol with a single injection was performed. The majority had a significant difference in uptake time between PET/ CT (commonly injected 60 min after injection) and the secondary PET/MR scan (with uptake times from 135 min [46] up to 180 min [47]). Table 6.1 summarizes results of studies comparing SUVs estimated on PET/CT and PET/MR images.…”

FDG Whole-Body PET/MRI in Oncology: a Systematic Review

“…Careful interpretation is needed for direct comparison of quantitative PET/MR and PET/CT results [86,87].…”

PET/MRI and PET/CT: is there room for both at the top of the food chain?

“…Of these, roughly 22 are original articles comparing the diagnostic performance of these two hybrid imaging modalities in oncology. Six report data from mixed groups of patients [2][3][4][5][6][7], with five finding an equivalence of diagnostic performance of the two hybrid imaging technologies and one a slight superiority of PET/MRI over PET/CT with regard to influence on further clinical management. None deals with thyroid cancer directly, allowing us to consider the new publication under discussion by Vrachimis et al the first to study this neoplastic entity specifically.…”