The Promise of Hybrid PET\/MRI: Technical advances and clinical applications

During the last few decades, positron emission tomography (PET)-based molecular imaging has advanced elegantly and steadily gained importance in the clinical and research arenas. However, the lack of structural information provided by this imaging modality motivated its correlation with structural imaging techniques such as X-ray computed tomography (CT) or magnetic resonance imaging (MRI), which are well established in the clinical setting. The additional capability of simultaneous acquisition of PET and MRI data bridges the gap between molecular and morphologic diagnoses. Since diagnostic imaging methods evolve from the anatomical to the molecular level, the mission of multimodal and multiparametric imaging increasingly becomes more essential. Since 2010, whole-body hybrid PET/MRI has been investigated in the clinical setting for clinical diagnosis and staging, treatment response monitoring, and radiation therapy treatment planning of a wide range of malignancies. However, quantitative PET/MRI is still challenged by the lack of accurate and robust attenuation and motion compensation strategies to enable the production of artifact-free and quantitative PET images. This article briefly summarizes the historical development of PET/MRI and gives an overview of the state of the art and recent advances in the design and construction of clinical systems. Progress in quantitative imaging, including MRI-guided image reconstruction and correction, and potential clinical applications of this novel technology are also discussed.