Abstract
AimTo 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.MethodsTwenty-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.ResultsIn 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.ConclusionPET/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.
Highlights
Positron emission tomography (PET) is a well-established tool for tumour imaging in neuro-oncology
For ROI90, ROITBR and VOITBR changes in time-activity curves (TACs) pattern categorisations were observed in up to 4%, 8% and 6% of the examinations when using different MR-attenuation correction (AC) methods, respectively
time to peak (TTP) changes were found for all ROI/VOI definitions in a varying percentage of cases depending on the used MRI-based AC (MR-AC) method (Table 3)
Summary
Positron emission tomography (PET) is a well-established tool for tumour imaging in neuro-oncology. PET imaging using amino acid tracers has been demonstrated to be of particular value for the diagnosis, prognosis and therapy response assessment of glioma patients [1,2,3]. Amino acid PET is used for target definition in radiation therapy and for guided surgical biopsy [4, 5]. Several studies have shown the value of [18F]FET for the assessment of gliomas [1, 6,7,8,9]. Its clinical adoption has been recently recommended by the Response Assessment in Neuro-Oncology Working Group together with the European Association for NeuroOncology [2]. The observed [18F]FET uptake behaviour within a brain tumour lesion over the time evaluated by different PET techniques enables a better understanding for brain tumour grading with the possibility to detect anaplastic foci and treatment response [10,11,12,13]
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