Pediatric CT: Growing Pains
Growing up is a tough business. Safety is constantly on the radar; questions seem incessant; solutions can be elusive; and consistency appears improbable. But after 18 or so years, the end result more than justifies the inputs. The similarities between shepherding a toddler to teen years and beyond and managing an imaging modality from near universal utility to safe, targeted use are striking.

Indeed, there are echoes of the turbulent teen years in the spate of headlines questioning the role of pediatric CT. In June, the situation may have reached its apex (or nadir) when a study published in The Lancet linked childhood CT scans with slight increases in risks for leukemia and brain cancer. The researchers preached caution, emphasizing the small, but absolute risk of developing cancer after a CT study.

This study and others have fueled a shift in pediatric CT imaging patterns, particularly in academic medical centers and children’s hospitals. As some sites have sprinted ahead, others are taking baby steps. Lower pediatric patient volumes, less favorable radiologist and technologist staffing ratios and variable levels of technologist expertise present formidable challenges as mainstream radiology practices attempt to keep up with academic medical centers and children’s hospitals.

CT vs. US – A Diagnostic Dilemma
CT vs. US - 163.91 Kb
Left image: Four serial images from a lower dose CT scan for appendicitis. This demonstrates (yellow arrow) an appendicolith blocking the orifice of the appendix. The rest of the appendix (blue arrow) is dilated and there is increased vascularity to the appendix with periappendiceal inflammatory change. Right image: Ultrasound shows a blind ending tubular structure that represents the inflamed appendix. The tip of the appendix (yellow arrow) measures 10 mm. A normal appendix should measure 6 mm or less.
Source: Marilyn J. Goske, MD, Cincinnati Children’s Hospital Medical Center

The curious case of the appendicitis algorithm

Suspected appendicitis may best illustrate the challenges of substituting an alternative imaging modality for CT among pediatric patients. Research supports ultrasound as the initial imaging tool in the evaluation of pediatric patients with suspected appendicitis. However, translating research into practice is a gradual process.

Use of CT in children presenting to emergency departments with nontraumatic abdominal pain increased from 2 percent in 1999 to 16 percent in 2007, according to a study published online April 24 in Radiology. The study mined data from the National Hospital Ambulatory Medical Care Survey for 16.9 million pediatric emergency department visits. The researchers reported one anomaly. Patients at pediatric EDs were more than 25 percent less likely to undergo CT even after adjustment for other characteristics.

Take, for example, Cincinnati Children’s Hospital Medical Center (CCHMC). The center has switched its imaging algorithm for patients with suspected appendicitis, says Marilyn J. Goske, MD, staff radiologist and chair of Alliance for Radiation Safety in Pediatric Imaging. Patients are referred to ultrasound as the initial imaging exam, and proceed to CT, if indicated. CT may be ordered for children with perforations or atypical findings.

The shift from CT to ultrasound was challenging, says Goske. CCHMC has many advantages, including 24/7 coverage of pediatric sonographers. “There is a learning curve when a department tries to switch from CT to ultrasound. There has to be a commitment on the part of surgeons and other clinicians that we may need to perform both studies for a period of time [as sonographers develop skills].”

While children’s facilities are able to overcome such hurdles, general radiology practices may be unable to initiate the change.

1, 2, 3 Tips to Support Dose Reduction
1. Look for online, just-in-time learning modules from CT vendors and professional societies. Options may include live chat, social networking and quick tip sheets embedded into the CT console.

2. Create a structure to support collaboration between technologists, physicists, radiologists and other specialists. Protocol modification can yield significant reductions in radiation exposure by substituting single phase studies for multiple phase scans, reducing the extent of coverage or lowering dose. Lower quality images may suffice for certain indications; however, technologists need to understand parameters and expectations. “Make sure technologists are adhering to Image Gently and inserting new recommendations, such as dropping the kV for a kidney stone exam, into protocols,” says William T. Thorwarth, MD, a radiologist with Catawba Radiological Associates in Hickory, N.C.

3. Don’t sacrifice training in the rush to deploy new systems. “Allow the vendor to complete the entire educational process as designed before go-live,” says Greg Morrison, COO of the American Society of Radiologic Technologists.
Take, for example, Catawba Radiological Associates in Hickory, N.C., a fairly typical U.S. practice comprised of 18 radiologists who serve three hospitals and two outpatient imaging centers. Like every radiology provider, the practice is acutely aware of the need to reduce children’s radiation exposure.

But some factors take precedence over radiation exposure. Referring physicians need to trust the study results, says William T. Thorwarth, MD, a radiologist with Catawba Radiological Associates.

The practice has not been able to substitute ultrasound for CT in most cases of suspected appendicitis among children, an indication which requires a very high negative predictive value. “There is not a high level of confidence among our surgeons that we can provide them with an answer they can act on in these cases.” Surgeons often voice a common question: If the appendix is not visible on ultrasound, does that rule out appendicitis? Thorwarth and his colleagues have to respond with a “no.”

Why? Sonographer experience with the exam is variable. The practice handles approximately 15 cases of pediatric appendicitis each month among its three hospitals; the relatively low volume makes it challenging to build a knowledge base among sonographers and develop surgical confidence in the model. Although some experienced sonographers are quite adept with the exam, it is difficult to perform. If a less experienced sonographer performs the exam, the radiologist may need to repeat it to resolve remaining questions. This potential quality issue instigates a logistical challenge.

The practice staffs radiologists at each hospital during regular business hours, so a physician could be on hand to complete the study. But nights and weekends are a different story. On-call radiologists read images from a central reading center connected to the three hospitals by fiber optics. One hospital is located 22 miles from the reading center, and it’s problematic for the physician to travel that distance to confirm whether or not a patient’s appendix is inflamed. In addition, if ultrasound were provided during the day but not evenings or weekends, it might expose the practice to medico-legal risk, because it would mean delivering two standards of care depending on the time of day.

CT for suspected pediatric appendicitis is considerably less problematic. It’s standardized, and answers surgeons’ questions with reasonable certainty, says Thorwarth.

Smart strategies

Catawba Radiological Associates has been able to trim CT utilization in some cases. “We try to make clinicians aware of repeat patients.” Young adolescent females may present with recurrent abdominal pain that mimics appendicitis. “We try to encourage emergency physicians to consider pelvic ultrasound first in that population.”

If a patient visits the same hospital more than once, the physician may be able to use the patient’s history in the EMR to resolve the pain. However, the N.C. region lacks a common EMR, so when patients shift between emergency rooms, physicians lose access to the patient’s chart. Thorwarth envisions that this hurdle may be overcome if local providers join the RSNA Image Share project, which would provide the capability to access imaging records from any participating site.

There are other ways to address some barriers to radiation exposure among pediatric patients. Training allowances, particularly for CT technologists and sonographers, often seem like an easy target for budget cuts. “Technologists play a critical role. They are the last person who can make an impact on radiation exposure,” says Greg Morrison, COO of the American Society of Radiologic Technologists.  

Radiology practices may have less control over other solutions. Take, for example, iterative reconstruction, which can deliver a 40 percent dose reduction while maintaining diagnostic quality. When compared with filtered back projection, iterative reconstruction dropped dose from an average 6.9 mGy to 3.7 mGy for chest CT exams, and 8.1 mGy to 5.0 mGy for abdominal CT studies, according to a study published in the May issue of Radiology.

However, reductions in technical component reimbursement have tied facilities’ hands, says Thorwarth. “Hospitals don’t have the capital to make upgrades or purchase new scanners that would allow these new technologies to be [more widely deployed].” Instead, the practice stresses ongoing communication between radiologists and technologists to maintain focus on radiation safety.

Best practices: The Image Gently model

Image Gently, a global campaign to child-size radiation exposure, is the poster child for reduced radiation exposure and parent communication.

In the wake of the study published in The Lancet in June, Image Gently responded with an online letter to parents, outlining the roles of parents, physicians and regulatory agencies and attempting to put concerns in context.

The effort exemplifies the approach the organization has taken. Image Gently tries to reduce barriers to communication between providers and parents, allowing access to free pamphlets and imaging record cards for hospitals and imaging practices. “There is no need to re-invent the wheel at every hospital,” says Goske. Radiology providers can access and print all of the campaign’s materials from its website.

Catawba Radiological Associates provides printed educational materials from Image Gently for parents and shares a link to its website, so parents can review the information as they schedule elective exams for their children. Most importantly, radiologists make themselves available to answer parents’ concerns if needed.  

“Sharing information with parents prior to the exam, and offering them an opportunity to ask questions reduces their anxiety,” says Goske, who recommends straightforward communication that avoids scientific terminology.

In many cases, technologists can answer general questions about precautions and pediatric protocols; creating a script to empower technologists to answer standard questions can save time and help ensure consistency. However, they should know that radiologists, physicists or the radiation safety officer is available to answer questions when needed, says Morrison.

CT will continue to evolve. Technical developments will drop exposure to the sub mSv level. “The goal is to reduce dose to the same level as an abdominal x-ray,” says Goske. However, as CT develops, the cure for growing pains remains constant: A comprehensive commitment to patient safety, parent communication and diagnostic confidence.