REVIEW published: 18 May 2018 doi: 10.3389/fphy.2018.00047 Frontiers in Physics | www.frontiersin.org 1 May 2018 | Volume 6 | Article 47 Edited by: Claudia Kuntner, Austrian Institute of Technology, Austria Reviewed by: Jose M. Perez, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Spain Marc Huisman, Medical Center, VU University Amsterdam, Netherlands *Correspondence: Jacobo Cal-Gonzalez jacobo.calgonzalez@meduniwien.ac.at Specialty section: This article was submitted to Biomedical Physics, a section of the journal Frontiers in Physics Received: 28 December 2017 Accepted: 30 April 2018 Published: 18 May 2018 Citation: Cal-Gonzalez J, Rausch I, Shiyam Sundar LK, Lassen ML, Muzik O, Moser E, Papp L and Beyer T (2018) Hybrid Imaging: Instrumentation and Data Processing. Front. Phys. 6:47. doi: 10.3389/fphy.2018.00047 Hybrid Imaging: Instrumentation and Data Processing Jacobo Cal-Gonzalez 1 *, Ivo Rausch 1 , Lalith K. Shiyam Sundar 1 , Martin L. Lassen 1 , Otto Muzik 2 , Ewald Moser 1,3 , Laszlo Papp 1 and Thomas Beyer 1 1 QIMP Team, Center for Medical Physics and Biomedical Engineering, Medical University Vienna, Vienna, Austria, 2 Department of Radiology, Children’s Hospital of Michigan, The Detroit Medical Center, Wayne State University School of Medicine, Detroit, MI, United States, 3 MR Center of Excellence, Medical University of Vienna, Vienna, Austria State-of-the-art patient management frequently requires the use of non-invasive imaging methods to assess the anatomy, function or molecular-biological conditions of patients or study subjects. Such imaging methods can be singular, providing either anatomical or molecular information, or they can be combined, thus, providing “anato-metabolic” information. Hybrid imaging denotes image acquisitions on systems that physically combine complementary imaging modalities for an improved diagnostic accuracy and confidence as well as for increased patient comfort. The physical combination of formerly independent imaging modalities was driven by leading innovators in the field of clinical research and benefited from technological advances that permitted the operation of PET and MR in close physical proximity, for example. This review covers milestones of the development of various hybrid imaging systems for use in clinical practice and small-animal research. Special attention is given to technological advances that helped the adoption of hybrid imaging, as well as to introducing methodological concepts that benefit from the availability of complementary anatomical and biological information, such as new types of image reconstruction and data correction schemes. The ultimate goal of hybrid imaging is to provide useful, complementary and quantitative information during patient work-up. Hybrid imaging also opens the door to multi-parametric assessment of diseases, which will help us better understand the causes of various diseases that currently contribute to a large fraction of healthcare costs. Keywords: hybrid imaging, combined imaging, instrumentation, nuclear medicine, data processing, data corrections INTRODUCTION Since the discovery of X-rays by Wilhelm Conrad Roentgen in 1895 [1], non-invasive medical imaging has become a standard tool for the diagnosis and staging of numerous diseases. X-ray Computed Tomography (CT) and Magnetic Resonance (MR), first introduced in the early [1] and late 1970s [2, 3], respectively, are the most widely used tomographic imaging techniques for depicting morphological changes of the human anatomy [4–6]. Metabolic or functional changes, which may occur without a corresponding change of anatomy, can be depicted by functional imaging, which has proven to provide essential information for the diagnosis and staging of many diseases. The first tomographic functional imaging modality was Single Photon Emission Tomography (SPECT), introduced in the early 1960s [7], followed be the first Positron Emission Tomography (PET) system in 1972 [8] and the first MR system in 1977 [3].