Hospital-acquired infections are a significant health-care problem, affecting 5%–10% of hospitalized patients in the United States and resulting in more than 75,000 annual deaths and $28–$33 billion in annual health-care costs . As part of the Hospital Acquired Condition Reduction Program established by the Patient Protection and Affordable Care Act, the Centers for Medicare and Medicaid Services publically reports hospital-acquired infection rates and penalizes hospitals with the highest rates of infection . Although much has been written about the implementation of standardized infection control and prevention practices in the medical community, less research has focused on infection control in diagnostic imaging. Patients visiting the radiology department may be exposed to infectious agents in a variety of locations, including waiting and holding areas, examination rooms, and imaging suites, and through exposure to pieces of equipment such as fluoroscopy tables and computed tomography (CT) and magnetic resonance imaging (MRI) scanners . Additionally, patients are at risk of cross contamination given that many different types of patients are often evaluated on the same pieces of equipment .
Most of the research regarding infection control in imaging has largely focused on interventional radiology. A 2006–2007 survey of more than 1000 interventional radiologists revealed a wide variety of infection control practices that were not in accordance with established guidelines . For instance, only 44% reported that they had received or participated in infection control training prior to the start of practice; only 50% consistently used protective barriers such as eyewear, face masks, or face shields during procedures; and only 71% of needlestick injuries were reported to employee health services. It was noted that interventional radiologists were most likely to alter their infection control practices if required to do so by the hospitals with which they were affiliated or by a professional organization. Although most of the instruments used during interventional or radiologic procedures are disposable, the equipment employed in the imaging of patients in diagnostic radiology is typically considered reusable. Thus, proper decontamination of this equipment is critical to prevent the transmission of infections between patients. Reusable devices are classified as critical, semicritical, or noncritical based on the Spaulding classification used by the Centers for Disease Control (CDC) and the U.S. Food and Drug Administration, and many devices and environmental surfaces encountered in diagnostic radiology are considered noncritical, such as the gantry, table, and other surfaces associated with CT and MRI scanners . It is recommended that decontamination of noncritical items be performed after every use and include either washing with soap and water or disinfecting with an intermediate- or low-level product . The CDC has issued recommendations regarding the use of sterilants and disinfectants, and guidance regarding the decontamination of specific equipment is often available from commercial manufacturers .
Several studies have investigated the contamination rate of equipment used for obtaining chest radiographs. For instance, Kim et al. showed that portable chest radiography cassettes had a 16% contamination rate with methicillin-resistant Staphylococcus aureus , and Levin et al. reported a 26% contamination rate for cassettes with antibiotic-resistant organisms . However, no research regarding potential contamination of CT scanners has previously been performed. In “Bacterial Contamination of CT Equipment: Use of ATP Detection and Culture Results to Target Quality Improvement,” Dr. Childress and colleagues present their investigation into the use of an adenosine triphosphate (ATP) monitoring system to minimize surface contamination on two inpatient CT scanners at a hospital of a quaternary care academic medical center. Bacterial cultures are typically used for the monitoring of hospital surfaces for contamination with pathogenic bacteria; however, there are significant limitations of this technique, including the cost, time, and labor involved, as well as the inability to isolate organisms such as Clostridium difficile . In response to such limitations of cultures, an ATP detection device has been developed by the food industry that quantitatively measures emitted light (measured in relative light units or RLUs) which is proportional to the amount of detected ATP. ATP detection systems have been studied previously in the health-care environment and, in contrast to bacterial cultures, are faster, less expensive, and quantitative . However, as the authors note, there are several limitations associated with these devices, including the fact that they have not been rigorously validated in the health-care setting. Nevertheless, the CDC suggests these devices as an acceptable method of monitoring surface contamination .
In their study, Childress and colleagues evaluated several components of two CT scanners, including the bore, table, and wrap, for contamination with bacterial cultures and an ATP detection system. Iterative plan-do-check-act (PDCA) cycles were performed and included data gathering, monitoring, and analysis, followed by specific interventions. The interventions were developed collaboratively by the study team, CT technologists, and CT technologist leadership. Six PDCA cycles were performed, all of which included ATP measurements; however, bacterial cultures were discontinued after the third cycle due to futility and low statistical power. The Velcro-based wrap was the most contaminated piece of CT scanner equipment, followed by the table and bore. Following the initial data collection, several strategies were devised, including the replacement of existing wraps, the maintenance of duplicate wraps, development and implementation of specific cleaning protocols for CT scanner equipment, the maintenance of daily cleaning logs, and implementation of barrier sheets for all inpatients. Institution of the new cleaning protocols resulted in a significant decrease in contamination based on the data collected during cycle 2; however, there was a significant increase in contamination measured during cycle 3. Team discussions with the CT technologists revealed several issues including waning enthusiasm for the project, the lack of cleaning logs, and abandonment of the cleaning process. Iterative meetings and leadership reinforcement were used to correct these issues, and improvement in equipment contamination was documented in the remaining three cycles with median RLU values well below the level designated as “contaminated” by the manufacturer (>350 RLUs).
This investigation demonstrates the potential usefulness of an ATP detection system in evaluating pieces of equipment associated with CT scanners, and suggests that specific standardized processes may be necessary in order to ensure adequate cleaning and decontamination of these items, especially when scanners are used to image a variety of patients (eg, inpatients and outpatients). Compared to bacterial cultures, these devices are faster, less expensive, more feasible, and provide quantitative data, and the results presented indicate that ATP detection systems can serve as a rough surrogate for bacterial contamination of imaging equipment.
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