Hybrid MR-PET Imaging by Shah N. Jon;

Author:Shah, N. Jon;
Language: eng
Format: epub
ISBN: 9781788016834
Publisher: Book Network Int'l Limited trading as NBN International (NBNi)
Published: 2018-03-16T16:00:00+00:00

Part B Hybrid MR-PET Imaging: technical overview

Section I Hardware

CHAPTER 9

Introduction and Historical Overview

H. Herzog*a and N. J. Shaha, b, c

a Forschungszentrum Jülich, Institute of Neuroscience and Medicine – 4, Wilhelm-Johnen-Straße 1, 52428 Jülich, Germany

b JARA - BRAIN - Translational Medicine, Aachen, Germany

c Department of Neurology, RWTH Aachen University, Aachen, Germany

*E-mail: [email protected]

9.1 Introduction

Comprehensive structural and functional insights into the body can be obtained by using different tomographic methods available in clinical diagnostics and medical research. Whereas computed tomography (CT) and magnetic resonance imaging (MRI) primarily produce images of anatomical details with high-resolution, single photon emission computed tomography (SPECT) and positron emission tomography (PET) are able to observe a great variety of functional, i.e. physiological and biochemical, processes. For many years, the complementary diagnostic information available from the different procedures could only be obtained by using dedicated imaging devices separately. This situation changed with the combination of PET and CT into one single instrument capable of delivering corresponding functional and structural information in one examination.1,2 In PET/CT the two modalities are positioned one after the other and have a common patient bed. Although first ideas around PET/CT aimed at simultaneous imaging, the ideas lacked feasibility and only scanners capable of sequential measurements were produced. With the development of spiral CT, with more and more slices, the acquisition time of the CT measurement could be shortened to just a couple of seconds so that the subsequent PET study became the time-limiting factor. If the patient does not move, the detailed anatomical information afforded by the CT supports the evaluation of the PET images—beyond the diagnostic value of the CT itself. Often the images obtained by PET and CT deliver complementary data, which improves both the sensitivity and specificity of the diagnostic outcome. In particular, oncology has benefited from the successful combination of CT with PET, especially when using [18F]-fluorodeoxyglucose (FDG)3,6 as a radiopharmaceutical, and, as a consequence, all major manufactures now only produce PET/CT scanners instead of PET-only scanners. In addition, SPECT/CT, originally proposed by Hasegawa et al.7 and currently offered by the majority of manufacturers, is becoming more and more popular. More details comparing PET/CT vs. SPECT/CT have been reported by Delbeke et al.,8 Bockisch et al.9 and Hicks et al.10

In the 1970s, MRI was introduced as another imaging tool and was primarily used to show structural details of the body. Nowadays, it is available in clinical departments and practices. Since its beginnings, MRI has demonstrated a steady increase in resolution and in versatility so that anatomical details can be revealed in many different ways. Furthermore, MR methods, such as functional MRI (fMRI), diffusion-weighted imaging (DWI) and chemical shift imaging (CSI) provide functional and metabolic information beyond anatomy. When compared to CT, MRI provides much better contrast in soft tissues such as liver and brain. Moreover, unlike the imaging procedures mentioned above, MRI does not involve ionising radiation making it suitable for repeated scanning or, in particular, in the paediatric population.

Having the advantages of MRI in mind and being aware of the success of PET/CT, the idea of combining MRI with PET in one device is obvious.

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