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. 2019 Aug;29(8):4276-4285.
doi: 10.1007/s00330-018-5942-9. Epub 2019 Jan 11.

Dynamic [18F]FET-PET/MRI using standard MRI-based attenuation correction methods

Ivo Rausch  1 , Andreas Zitterl  2 , Neydher Berroterán-Infante  1 , Lucas Rischka  3 , Daniela Prayer  4 , Matthias Fenchel  5 , Reza A Sareshgi  2   6 , Alexander R Haug  2 , Marcus Hacker  2 , Thomas Beyer  1 , Tatjana Traub-Weidinger  7
Affiliations

Dynamic [18F]FET-PET/MRI using standard MRI-based attenuation correction methods

Ivo Rausch et al. Eur Radiol. 2019 Aug.

Abstract

Aim: To assess if tumour grading based on dynamic [18F]FET positron emission tomography/magnetic resonance imaging (PET/MRI) studies is affected by different MRI-based attenuation correction (AC) methods.

Methods: Twenty-four patients with suspected brain tumours underwent dynamic [18F]FET-PET/MRI examinations and subsequent low-dose computed tomography (CT) scans of the head. The dynamic PET data was reconstructed using the following AC methods: standard Dixon-based AC and ultra-short echo time MRI-based AC (MR-AC) and a model-based AC approach. All data were reconstructed also using CT-based AC (reference). For all lesions and reconstructions, time-activity curves (TACs) and time to peak (TTP) were extracted using different region-of-interest (ROI) and volume-of-interest (VOI) definitions. According to the most common evaluation approaches, TACs were categorised into two or three distinct curve patterns. Changes in TTP and TAC patterns compared to PET using CT-based AC were reported.

Results: In the majority of cases, TAC patterns did not change. However, TAC pattern changes as well as changes in TTP were observed in up to 8% and 17% of the cases when using different MR-AC methods and ROI/VOI definitions, respectively. However, these changes in TTP and TAC pattern were attributed to different delineations of the ROIs/VOIs in PET corrected with different AC methods.

Conclusion: PET/MRI using different MR-AC methods can be used for the assessment of TAC patterns in dynamic [18F]FET studies, as long as a meaningful delineation of the area of interest within the tumour is ensured.

Key points: • PET/MRI using different MR-AC methods can be used for dynamic [18F]FET studies. • A meaningful segmentation of the area of interest needs to be ensured, mandating a visual validation of the delineation by an experienced reader.

Keywords: Brain neoplasms; Magnet resonance imaging; Positron emission tomography; Radionuclide imaging.

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Conflict of interest statement

Matthias Fenchel is an employee of Siemens Healthcare GmbH.

Figures

Fig. 1
Fig. 1
Example of the used MR-AC methods compared to CT-AC. a CT-AC. b Dixon-AC. c Model-based AC. d UTE AC. Image shows the same sagittal and axial slices of one patient
Fig. 2
Fig. 2
a ROI90 and ROITBR delineated on the summed (20–40 min) PET images following three MR-AC and the CT-AC methods. In the CT-AC and UTE-AC PET, the ROITBR included physiological [18F]FET uptake in the scalp. Further, in the UTE-AC PET, the ROITBR segmentation resulted in an extended ROI when compared to ROITBR in the Dixon-AC and model-based AC PET. b TAC extracted from ROI90 and ROITBR in PET images corrected using the different AC methods
Fig. 3
Fig. 3
a T1-weighted MRI with a contrast-enhancing lesion (cyan arrow) and the arteria carotis interna (orange arrow). b ROITBR delineation of a tumour in the PET image after AC using the model-based approach. In this case, the ROITBR additionally includes parts of the arteria carotis interna. c TACs extracted from ROITBR (red) and from two manually drawn ROIs in the tumour (ROITumour, cyan) and the arteria carotis interna (ROIVessel, orange). The TAC extracted from ROITBR is a mixture of the TAC extracted from ROITumour and ROIVessel
Fig. 4
Fig. 4
Relative difference of TBRs using the three MR-based AC methods in comparison to the TBRs extracted from PET after CT-AC
Fig. 5
Fig. 5
Relative difference of the PET-based ROI and VOI for the three MR-AC methods in comparison to the ROI and VOI following CT-AC
See this image and copyright information in PMC

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