Clinical Applications of SPECT–CT

CLINICAL APPLICATIONS

OF SPECT–CT

IAEA HUMAN HEALTH SERIES No. 41

CLINICAL APPLICATIONS

OF SPECT–CT

INTERNATIONAL ATOMIC ENERGY AGENCY

VIENNA, 2023

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STI/PUB/1971

IAEA Library Cataloguing in Publication Data

Names: International Atomic Energy Agency.

Title: Clinical applications of SPECT–CT / International Atomic Energy Agency.

Description: Vienna : International Atomic Energy Agency, 2023. | Series: IAEA human health series, ISSN 2075–3772 ; no. 41 | Includes bibliographical references.

Identifiers: IAEAL 22-01494 | ISBN 978–92–0–111522–5 (paperback : alk. paper) | ISBN 978–92–0–111722–9 (pdf) | ISBN 978–92–0–111622–2 (epub)

Subjects: LCSH: Single-photon emission computed tomography. | Diagnostic imaging. | Tomography. | Nuclear medicine.

Classification: UDC 616-073 | STI/PUB/1971

FOREWORD

More than two decades after the advent of positron emission tomography–computed tomography (PET–CT), a new era of revived interest in conventional nuclear medicine imaging is being witnessed. So-called ‘hybrid imaging’ refers not only to PET–CT (or PET combined with magnetic resonance imaging (MRI)), but also to the combination of single photon emission computed tomography (SPECT) with CT. SPECT–CT shares with PET–CT the possibility of accurate anatomical localization of areas of increased uptake, as well as — more importantly — the benefits and advantages deriving from the ability to directly translate molecular or metabolic information into an immediate clinical impact on the widest possible range of diseases. Indeed, SPECT–CT has demonstrated significant improvements for patient management in a variety of clinical indications, including both oncologic and non-oncologic diseases. Of course, this changing scenario has also raised new issues and continuing debate on the optimal modalities of managing the wealth of clinical information that can be retrieved by hybrid imaging.

In 2008, the IAEA published a technical document on the clinical advantages of SPECT–CT toward improved staging, prognosis and treatment monitoring for a wide variety of conditions, at a time when the technique was just coming out of its infancy. Since then, tremendous advances in technology have taken place; furthermore, the amount of clinical evidence that has accumulated worldwide is impressive. An up-to-date review of the current uses of SPECT–CT has therefore been undertaken in this publication, addressing its application both as a problem-solving approach (for which it was often initially used after its introduction into clinical practice) and as, above all, a systematic clinical practice that is fully integrated into the routine diagnostic approach to a series of disease conditions.

In this review, the complex technological and radiochemistry issues involved in the application of SPECT–CT imaging, such as gamma camera hardware, image acquisition protocols (including specific cardiac aspects and whole body SPECT–CT), quantitation and dosimetry, radiation exposure, novel single photon emitting radiopharmaceuticals, artefacts and pitfalls were deliberately not addressed. This matter is worthy of a separate initiative, which will be undertaken in the near future.

The IAEA wishes to thank the contributors to the drafting and review of this book for contributing their knowledge, time and effort. The IAEA officers responsible for this publication were F. Giammarile and D. Paez of the Division of Human Health.

EDITORIAL NOTE

Although great care has been taken to maintain the accuracy of information contained in this publication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use.

This publication does not address questions of responsibility, legal or otherwise, for acts or omissions on the part of any person.

Guidance provided here, describing good practices, represents expert opinion but does not constitute recommendations made on the basis of a consensus of Member States.

The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries.

The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA.

The IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this book and does not guarantee that any content on such web sites is, or will remain, accurate or appropriate.

The authoritative versions of the publications are the hard copies issued and available as PDFs on www.iaea.org/publications.To create the versions for e-readers, certain changes have been made, including the movement of some figures and tables.

CONTENTS

1. INTRODUCTION

1.1. Background

1.2. Scope

1.3. Objective

1.4. Structure

2. GENERAL PRINCIPLES

2.1. Appropriateness of imaging procedures based on the use of ionizing radiation

2.2. Education/training of the imaging specialist

2.3. Radiation dosimetry for hybrid SPECT–CT imaging

References to Section 2

3. CLINICAL APPLICATIONS

3.1. SPECT–CT in neurology

3.2. SPECT–CT in endocrinology

3.3. SPECT–CT in cardiology

3.4. SPECT–CT in pneumology

3.5. SPECT–CT in orthopaedics

3.6. SPECT–CT in inflammation

3.7. SPECT–CT in oncology

3.8. Gastroenterology

3.9. Paediatrics

References to Section 3

4. INCIDENTAL FINDINGS ON CT

References to Section 4

ABBREVIATIONS

CONTRIBUTORS TO DRAFTING AND REVIEW

1. INTRODUCTION

1.1. Background

Nuclear medicine techniques create images of functional processes by using radioactive tracers and photon detectors. Tomographic imaging with radionuclides began in the 1960s and pre-dates computed tomography (CT). Single photon emission computed tomography (SPECT) is a mainstay in nuclear medicine and has been used in routine diagnostic applications and research since the 1980s. In 1996, the first model of a combined SPECT–CT design, which comprised a clinical SPECT gamma camera in tandem with a clinical single slice CT, was produced. Since then, SPECT–CT has advanced rapidly, and several commercial systems are available today employing various designs of CT and dual head SPECT configurations. There are numerous advantages of an integrated, functional and morphological imaging device, including the following:

(a) A single examination can provide comprehensive functional and anatomical information on the state of a disease;

(b) Patients can be scheduled for only one instead of two or multiple examinations;

(c) Experts in radiology and nuclear medicine can review the complementary image sets together and integrate their interpretation into a single report.

Similarly to positron emission tomography (PET)–CT, the ability of SPECT–CT to provide, in a single image session, detailed anatomical and functional or metabolic information — a synergistic effect greater than the sum of the information from the two individual techniques — has established SPECT–CT as an indispensable imaging procedure for an increasing number of pathologies. In addition, it has a significant advantage over PET–CT, namely the use of a radiotracer widely available in all nuclear medicine departments: 99m-technetium (⁹⁹mTc). As a result, an increasing number of SPECT–CT systems are being installed by Member States, thus making it essential that capacities are built and strengthened in SPECT–CT for many nuclear medicine and imaging departments, particularly in countries that are just embarking on this imaging modality.

1.2. Scope

Hybrid imaging, including SPECT–CT, has experienced significant developments and improvements that have had positive impacts in recent years, and it now has an important place in several procedural guidelines. The technology has matured and more data are available to appraise its clinical role.

This publication was thus developed to emphasize classical indications in SPECT–CT imaging and highlight new fields in which SPECT–CT is being adopted while providing relevant information with regard to patient management.

1.3. Objective

This publication is intended to support nuclear medicine physicians, radiologists and clinical practitioners in their clinical decision making process when allocating resources dedicated to the health care system. This is a critical issue that is especially important for the development of nuclear medicine in developing countries.

Medical imaging is an integral part of patient management; the objective of this publication is to provide a list of the most common indications of SPECT–CT in clinical practice. The IAEA hopes that this publication will be of help for medical professionals and staff working with SPECT–CT for personal learning, training, and teaching purposes. Guidance provided here, describing good practices, represents expert opinion but does not constitute recommendations made on the basis of a consensus of Member States.

1.4. Structure

The structure of this publication is adapted to the applications of SPECT–CT in nine different clinical scenarios, namely neurology; endocrinology; cardiology; orthopaedics; oncology; respiratory, infectious and gastrointestinal diseases; and paediatrics. A final chapter describes the clinical impact of incidental findings observed in the CT component of the scan.

2. GENERAL PRINCIPLES

There are several tokens by which one can identify the events or discoveries that have revolutionized the practice of medicine throughout history. No consensus exists on what to consider the most important of ‘modern’ medicine’s achievements, some of which have induced dramatic paradigm shifts in patient management [2.1]. Candidates vary widely [2.2] and include tools specifically related to therapy (e.g. vaccines, the hypodermic needle, antibiotics and antiviral drugs, germ theory and antisepsis, anaesthesia, haemodialysis, prosthetic implants, cardiac pacemakers, organ transplantation and the cardiac defibrillator) and diagnostic methods (e.g. the stethoscope, the thermometer, X rays and medical imaging in general, and the electrocardiogram), as well as procedures that aim to have a more general impact on medical science (e.g. controlled clinical trials and artificial intelligence) [2.3].

For investigators and clinicians working in the field — and increasingly for the whole medical community — nuclear medicine represents a crucial turning point because it provides an interface or bridge between physiology and clinical medicine. This intrinsic feature of both diagnostic and therapeutic nuclear medicine has led to the coining of the term ‘molecular imaging’ or, more appropriately, ‘molecular targeting’. Molecular targeting may be defined as the specific concentration of a diagnostic tracer or therapeutic agent by virtue of its interaction with a molecular species that is distinctly present or absent in a disease state [2.4]. Although intrinsic to nuclear medicine since its earliest inception, this feature has been heightened by the development of PET imaging (and especially hybrid PET–CT, or, more recently, PET combined with magnetic resonance imaging (MRI)), which has revolutionized diagnostic nuclear medicine and revived its long standing position as a crucial approach to theranostics [2.5–2.15].

The excitement and expectation that the advent of PET–CT raised in the nuclear medicine community and in the diagnostic imaging community at large led to speculation in 2008 that, the availability of a complete armamentarium of PET radiopharmaceuticals would eventually replace virtually all single photon agents [2.16]. This would therefore result in the impending