Focus on Diagnosis: Figure.

Abstract

1. Jennifer S. Linebarger, MD* 2. Michelle L. Roy, MD† 1. *Fellow, Adolescent Medicine, University of Rochester Medical Center, Rochester, NY 2. †Attending physician, Newborn Service, UCSD, San Diego, Calif After completing this article, readers should be able to: 1. Describe the basic principles of the field of nuclear medicine. 2. Discuss the most common pediatric nuclear medicine studies. 3. Recognize when a nuclear medicine study is appropriate for patients. Nuclear medicine is a useful and expanding field. Unlike the more standard anatomic radiographic studies, nuclear medicine incorporates physiology and biochemistry into image creation. The most common pediatric nuclear medicine studies image bone, kidneys, intestines, biliary tract, and thyroid. It is important for general pediatricians to have a practical understanding of these studies because more than 75% are ordered in the outpatient setting. All of these studies rely on the decay of radiopharmaceuticals (most commonly, technetium-99m). As decay occurs, photons are emitted and captured by a gamma camera, which turns the signal into an image. This process is known as scintigraphy. This article describes the indications, study mechanics, benefits, and alternatives to six common pediatric nuclear medicine scans: bone and renal scintigraphy; Meckel diverticulum imaging; and gastroesophageal, hepatobiliary, and thyroid scintigraphy. Bone scintigraphy (bone scan) is used to identify and monitor bony lesions such as osteomyelitis, minor fractures (eg, stress fractures), bone cancers, and bony metastasis. The radiopharmaceutical, usually technetium-labeled polyphosphate, is injected intravenously and distributes in bones proportional to blood flow. Three sets of images are obtained: flow, early blood pool, and whole body. The entire process takes about 3 hours, but each scan is obtained quickly. Comparison images from the contralateral side always are obtained. Potential lesions are identified based on the degree of radiotracer uptake as compared with normal tissues. Bone scintigraphy is more appealing than standard radiographs in certain circumstances. For diagnosing trauma, bone scintigraphy is 25% to 50% more sensitive than plain films (Figure⇓). Osteomyelitis can be detected within 24 to 72 hours by using a bone …