Pediatric PET Imaging (eBook)

Foreword I 7
Foreword II 9
Preface 11
Contents 15
Contributors 19
Section 1 Basic Science and Practical Issues 25
1 The Nuclear Imaging Technologist and the Pediatric Patient 26
2 Sedation of the Pediatric Patient 44
3 The Biologic Effects of Low-Level Radiation 53
4 Dosage of Radiopharmaceuticals and Internal Dosimetry 60
5 Pediatric PET Research Regulations 70
6 Issues in the Institutional Review Board Review of PET Scan Protocols 82
7 Ethics of PET Research in Children 95
8 Physics and Instrumentation in PET 115
9 How to Image a Child by PET–Computed Tomography 144
10 Coincidence Imaging 158
Section 2 Oncology 195
11 Brain Tumors 196
12 Lymphoma 241
13 Neuroblastoma 264
14 Wilms’ Tumor 277
15 Primary Bone Tumors 288
16 Soft Tissue Sarcomas 323
17 Other Tumors 333
Section 3 Neurology and Psychiatry 342
18 The Developing Brain 343
19 Neurodevelopmental and Neuropsychiatric Disorders 354
20 Epilepsy 381
21 Neurotransmitter Imaging 405
22 Cardiovascular Applications 425
Section 4 Other Applications 424
23 Fever of Unknown Origin 446
24 Infection and In.ammation 466
25 In.ammatory Bowel Disease 479
26A Hyperinsulinism of Infancy: Noninvasive Differential Diagnosis 490
26B Hyperinsulinism of Infancy: Localization of Focal Forms 497
27 Multimodal Imaging Using PET and MRI 503
28 Current Research Efforts 520
Section 5 Imaging Atlas 543
29 PET–Computed Tomography Atlas 544
30 Common Artifacts on PET Imaging 560
Index 582

13 Neuroblastoma (p. 243-244)

Barry L. Shulkin

Neuroblastoma is the most common extracranial solid tumor of childhood. It comprises 8% to 10% of all childhood neoplasms. Neuroblastoma is derived from primordial neural crest cells that normally differentiate into the sympathetic nervous system. The prevalence is about 1 case per 7000 newborns. There are about 600 new cases in the United States per year, and over 90% occur in children less than 6 years old. The median age is 22 months. Most primary tumors occur within the abdomen, especially the adrenal gland, although they may arise from any site along the course of the sympathetic nervous system. Other common sites are paraspinal ganglia of the posterior mediastinum and abdomen. About 60% of patients have widely metastatic osseous disease at presentation.

Related to their origin from precursor cells of the sympathetic nervous system, most of these tumors are associated with high urinary levels of catecholamine metabolites, such as vanillylmandelic acid formed from norepinephrine, homovanillic acid formed from dopamine, or dopamine. Occasionally the tumor may cause hypertension (1). The prognosis of patients with neuroblastoma depends on the histopathologic system developed by Shimada et al. (2). This incorporates the patient’s age, the presence or absence of Schwann cell stroma, the degree of differentiation, and the mitosis-karyorrhexis index (number of mitoses and ruptured cell nuclei).

Staging is based on the International Neuroblastoma Staging System (INSS) (3). In general, stage 1 is a localized tumor without regional lymph node involvement, stage 2 is a unilateral tumor with either incomplete gross resection or ipsilateral nodal involvement, stage 3 is tumor that crosses the midline or has contralateral nodal involvement, and stage 4 is tumor disseminated to distant nodes, bone, bone marrow, liver, etc. Stage 4s is a special category of infants less than 1 year of age with a localized primary tumor and dissemination only to liver, skin, or bone marrow.

Meta-Iodobenzylguanidine (mIBG)

Any discussion of functional imaging of neuroblastoma is incomplete without reference to meta-iodobenzylguanidine (mIBG). This is the conventional agent for functional imaging of neuroblastoma. This agent was originally applied to the localization of pheochromocytoma. Sisson and colleagues (4) demonstrated its utility in the management of patients with pheochromocytoma. Its use in neuroblastoma followed shortly (5,6). This agent requires the presence of a functional type 1 catecholamine uptake system. Within the sympathetic nervous system, type 1 catecholamine uptake transports the neurotransmitter norepinephrine from the synaptic cleft back into the presynaptic nerve terminal. This serves to terminate neurotransmission until norepinephrine is once again released into the synaptic cleft. Functional imaging with mIBG takes advantage of the adrenergic origin of neuroblastoma. mIBG is taken up by and concentrated within most neuroblastomas both in vivo and in vitro. mIBG exists within both the cytoplasm and specialized norepinephrine storage granules. Most of the agents we will discuss also depend on type 1 catecholamine uptake for transport into neuroblastoma cells. mIBG can be labeled with the various isotopes of iodine. Iodine-131 (131I) mIBG was the .rst agent developed by Wieland and colleagues (7). Its use in the imaging of pheochromocytoma was reported by Sisson. mIBG was soon labeled with 123I. For many years, only I mIBG was available commercially in the United States although 123I mIBG was available in Europe. However, many pediatric centers in the United States used I mIBG, which was synthesized on site for local use only. Now 123I mIBG is available widely within the United States, and it is expected that it will soon be approved by the Food and Drug Administration (FDA) for use in children.

High-quality images can be obtained using 131I mIBG with careful attention to detail (8). Serial images are usually obtained 24, 48, and sometimes 72 hours after injection of 0.5 to 1mCi reduced by child weight or body surface area. Images of the entire body are recommended at 20 minutes per bed position using a high-energy collimator. The dose of 131I mIBG is limited due to the relatively long half-life of the 131I label (8 days), the presence of the beta particle that adds to the radiation dose but does not contribute to imaging, and the highenergy photon. Higher doses of 123I mIBG can be given for the same radiation exposure, resulting in much higher quality images (Fig. 13.1). About 10 times as many counts are obtained using 123I mIBG as with 131I mIBG. 123I mIBG has advantages of shorter half-life (13 hours), ideal energy of the photon imaged (159keV), and lack of beta particle. The sensitivity of mIBG in the detection of neuroblastoma is about 90% and speci.city nearly 100%.