When children are sick or injured, imaging can play an important role in defining the problem and guiding subsequent management decisions. Children can be imaged with the same modalities as adults, which include digital radiography, or the plain “x-ray”; ultrasound (US); computed tomography, or “cat-scan” (CT); fluoroscopy; nuclear medicine (NM); and magnetic resonance imaging (MRI). The primary care provider makes the initial choice or selection of the type of study needed with consultation from the radiologist, when needed.
Digital radiography, or the plain x-ray
Digital radiography, or the plain x-ray is still the workhorse modality of pediatric imaging. Plain x-rays are widely available and quickly obtained, with a very low dose of radiation involved. Properly ordered, performed and interpreted, plain films are often the best first step in the evaluation of many common pediatric problems, including chest films for the child with fever, cough and suspected pneumonia; bone films for the child with trauma and suspected fracture; abdominal films for the child with abdominal pain and/or constipation; and spine films for the child with scoliosis or spinal curvature.
Ultrasound is perhaps the ideal modality for imaging children, in that it is widely available, rapidly performed and does not involve any radiation. US is limited by its inability to see through bowel gas, which can be significant, as the crying child can swallow a lot of air. US is commonly performed to evaluate the vomiting infant, the child with abdominal pain, the child with urinary tract infections and the baby at risk for hip dysplasia.
CT scans, or cat-scans
CT scans, or cat-scans, are a specialized form of x-ray that is widely available, rapidly performed and highly accurate. Cats and other animals are wonderful companions, but not allowed in the imaging department. As CT scans involve the delivery of higher doses of radiation, they must be appropriately ordered and performed. CT has its greatest utility in the evaluation of children with closed head injury, appendicitis, blunt abdominal trauma and sinus disease.
Fluoroscopic studies in children are relatively less frequently performed, but also employ higher doses of radiation and therefore must be carefully ordered and performed. These procedures are often more stressful for both parent and child. Common fluoroscopic procedures include the upper GI series for the vomiting child, the voiding cystourethrogram for the child with urinary tract infections, and the contrast enema for the child with intractable constipation or the newborn with bowel obstruction.
Nuclear medicine studies
Nuclear medicine studies involve the injection of a radioactive substance or radiopharmaceutical into the body and imaging the biodistribution of that substance with special cameras. Although that sounds a bit like Spiderman, to my knowledge, no children have gained superpowers from a NM scan. NM studies also involve higher doses of radiation and must be carefully chosen and performed. Common NM studies include the bone scan to evaluate adolescent back pain and fractures not detectable by plain x-rays, and scans of the urinary tract to evaluate children with recurrent infections or urinary tract obstructions.
MRI scans are kid-friendly, in that they do not deliver radiation, but kid-not-so-friendly, in that they require holding still for longer periods of time. MRI scans are excellent for evaluating the central nervous system, i.e., brain and spinal cord in children with neurological symptoms, and also for evaluating the musculoskeletal system of the adolescent athlete or pediatric weekend warrior. MRI technology continues to evolve at a rapid pace, with investigators developing new ways to use this technology and US to perhaps become less dependent on traditional radiation-based modalities.
In conclusion, imaging children is both a challenge and a privilege. Fortunately, pediatric imagers have many tools in their toolboxes and are well aware that your child is your most important asset. Pediatric imaging can be a delicate balance of risk and reward, as imagers try to minimize radiation exposure and maximize diagnostic benefit for the sick or injured child.
By Sam T. Auringer, MD (Pediatric Radiologist, Triad Radiology Associates)