Vallabhajosula S. Molecular Imaging: Radiopharmaceuticals for PET and SPECT. Springer 2009, 372 pages, 221 illustrations, $179.
The field of molecular imaging has been rapidly expanding in the past several years. The ability to gain insights into molecular events non-invasively certainly has profound implications on improving our understanding of different disease processes. It is not surprising that molecular imaging has become a major research area. Numerous probes for PET and SPECT imaging have been developed. Therefore, an overview of the currently available imaging probes will be extremely helpful for researchers as well as clinicians who are interested in the field of molecular imaging. This book, authored by Dr. Shankar Vallabhajosula, is thus timely and provides probably the most up-to-date review on a variety of topics focusing on radiopharmaceuticals for PET and SPECT imaging. Dr. Vallabhajosula should be applauded for providing such a comprehensive overview on almost all relevant components of nuclear medicine imaging — from basic nuclear physics to imaging instrumentation and from radiochemistry to cellular and molecular biology.
There are a total of 20 chapters covering a variety of topics related to molecular imaging using PET and SPECT imaging technologies. Specifically, five major topics are introduced and discussed: (1) the history of atomism, the fundamental principles of nuclear physics, and the physical designs of PET and SPECT scanners (Chapter 2-6); (2) an overview of chemistry and cell biology (Chapter 7-8); (3) the production of major radiopharmaceuticals (Chapter 9-13); (4) pharmacokinetic analysis and image quantification methods (Chapter 14); and finally (5) imaging applications in four pathophysiological conditions (Chapter 15-18). The author also introduces radiation dosimetry (Chapter 19) and federal regulations on the development and manufacture of radiopharmaceuticals (Chapter 20). Overall, this book is well organized, well laid out, and the topics are logically followed. A brief overview of the contents of each chapter is provided below.
This book starts with an introduction on nuclear medicine, which sets the tone for this book to specifically emphasize PET and SPECT for molecular imaging. While PET and SPECT are indeed the two most commonly employed radiographic imaging approaches for probing in vivo molecular events, due to its high sensitivity and quantification accuracy, several other imaging modalities are also capable of providing molecular information non-invasively, including MR, optical imaging, and ultrasound. The overview of other imaging modalities is rather brief, which may not be sufficient to provide a broad view of molecular imaging as a whole.
Chapter 2 reviews the history of the science of atomism. It is remarkable that the author is able to convey the main science discoveries in the field of atomism in such a smooth and effortless manner, ranging from the discovery of the atom to the foundation of quantum physics. With his broad knowledge and enthusiasm for science, the author has successfully conveyed such appreciation and insights of history to readers.
Chapters 3-5 introduce the basic concepts of nuclear physics and production of radionuclides. Although each component is only briefly discussed, it does cover most of the essential physical components of radionuclides. Several different production techniques of radionuclides are introduced, including linear accelerator, cyclotron, reactor-based activation, and generator based production. Production principles of major PET and SPECT radionuclides, including [18]F, [11]C, and [99m]Tc, are concisely described. Although additional reading and references are provided for readers who are interested in gaining more insights into this direction, it would be nice if more information on the general work flow and the preparation of target materials for some of the popular radionuclides could be provided. For example, [18]F with high specific activity is essential for the production of many F-18 labeled PET radiopharmaceuticals. Discussing the factors to improve specific activity could be of interest to general readers.
Chapter 6 provides a brief overview of the underlying physical concepts for the design as well as the instrumentation of PET and SPECT scanners. Although it is again rather brief, most of the fundamental principles of PET and SPECT scanners, especially the detectors, are well described.
Chapters 7 and 8 focus on the basic concepts of chemistry, biochemistry, and cell biology. The information provided in these two chapters is somewhat indirectly associated with molecular imaging. Chapter 7 covers some of the background information for materials to be introduced in Chapter 9, such as stereospecificity. Materials covered in Chapter 8 appear to distract from the overall focus of this book. Nevertheless, Chapter 8 could potentially provide fundamental biological information for readers who are more specialized in physics and/or hardware.
The productions of various radiopharmaceuticals are introduced and reviewed in Chapters 9-13. The author makes a distinction between radiopharmaceuticals and radiochemicals where the former represent radionuclides meeting criteria for human uses, while the latter include all remaining radionuclides. Although there have been numerous radiochemicals developed in recent years, only a handful of them have received FDA clearance for human uses. Table 9.1 on page 135 summarizes the current FDA-approved radiopharmaceuticals. The author points out several important factors guiding the design of radiolabeled compounds, including the size, the position of radiolabel, sterospecificity, lipophilicity, plasma protein binding, metabolism, and specific activity of the target compounds . Explanation of these factors should greatly facilitate the understanding of the production and chemistry of major radiopharmaceuticals. The chemistry of various radiopharmaceuticals is also comprehensively discussed in Chapters 10-13. Each chapter introduces the production of radioisotopes, the reaction between precursor and the radioisotope, and production examples of specific radiopharmaceuticals. These major radiopharmaceuticals are organized according to the following three categories: radiohalogens (F, Br, and I); organic radionuclides (C, N, O); and metal radionuclides (Rb, Ga, In. Y, Cu, and Tc), making it easier for readers to follow. These materials are up-to-date, and cover almost all of the popular radiopharmaceuticals for PET and SPECT imaging.
Image quantification methods such as SUV calculation, compartment modeling, and graphical analysis methods are briefly introduced in Chapter 14. These are not the main topics of this book, but they could be helpful for readers to grasp some ideas of image quantification methods.
From Chapter 15 until Chapter 18, the potential clinical applications are provided, including oncology (Chapter 15), neurology (Chapter 16), cardiology (Chapter 17), and gene expression/cell trafficking (Chapter 18). Unlike several currently available books focusing on the topic of PET/SPECT imaging in clinical applications where clinical diagnostic procedures, staging, or monitoring using molecular imaging methods are the primary focuses, the author puts more emphasis on the biological mechanisms of the imaging probes. In each chapter, the author provides fairly sufficient biological background information of diseases and clinical problems as well as the underlying biological mechanisms regarding how the probe works in context of a biological system prior to introducing imaging agents. The cartoon diagrams on the molecular pathways of a specific pathophysiological condition should help readers to understand the complicated biological systems. More importantly, Chapter 18 focusing on gene expression and cell trafficking is rather unique and demonstrates the newest development of PET/SPECT imaging along these directions. Although only a handful of probes have been tested, such as [124I]FIAU, [18F]FHBG, and [124I]MIBG, it has been demonstrated that PET imaging with radiolabeled reporter genes will become valuable tools in assisting gene therapy and/or basic genetic researches.
The final two chapters (Chapters 19-20) introduce radiation dosimetry and federal regulations on radiopharmaceuticals. These are essential components for researchers as well as clinicians working with radiopharmaceuticals. In great contrast to the lengthy and obscure descriptions of regulations provided in federal documents, the author has done an excellent job extracting the most important components from the federal documents, making it much easier for readers to understand and follow.
Overall, this book offers an up-to-date review on the radiopharmaceuticals for PET and SPECT imaging. It is very informative, well written, and the image quality is excellent. Its broad coverage, clear and concise descriptions, and easily understandable writing are clearly the strengths of this book. Although materials on neurologically related topics are not the main focus of this book, it certainly serves as an excellent reference book for molecular imaging. This book, as it stands, may not serve as a textbook for students owing to its lack of depth. However, it certainly can be an important reference book for many researchers and/or clinicians in the field of nuclear medicine and molecular imaging.
