Importance of measurement repeatability of semi-quantitative imaging through PET-CT and PET-MR imaging in oncology

Positron emission tomography (PET)/computed tomography (CT), magnetic resonance (MR) imaging, and the hybrid PET/MR scanner of recent introduction have seen rapid expansion in both research and clinical application (1-3). At present, they are increasingly used in clinical practice, especially in the oncologic setting for tumour detection and diagnosis, for histological subtype correlation and stratification of disease, for staging, for predicting and monitoring treatment response during chemotherapy and at the end of treatments, for prognosis on disease-free and overall survival, and for follow-up of tumours, in different organs and compartments (2-7).