Saturday, January 1, 2011

Technique, Technology Aid in Driving Down Dose

As Low As Reasonably Achievable, or ALARA, has always been the mantra of technologists and radiologists when it comes to the amount of radiation to which a patient is exposed during a diagnostic imaging exam. However, due to new technology, human error, or miscommunication there have been a clutch of high-profile incidents of patient overexposure in the past few years that have received widespread press attention. These cases have served to invigorate the commitment of imaging professionals to keep the dose as low as it can go, especially for the pediatric patient.

Dose management was a hot topic at the 2010 RSNA, with several presentations offering attendees the tools and techniques to deliver low-dose exams. Physicians shared their efforts to reduce the dose to a level that provides images that are clinically acceptable, while coping with added noise and reduced resolution. 

Manufacturers of digital radiography equipment, which has suffered from a tendency of technologists to increase dose (the "dose creep" phenomena), have implemented processing technologies to improve image quality and logging tools that allow administrators to catch and coach against dose creep in their facilities. 

High-volume, multi-slice CT has also come under scrutiny, with clinicians re-examining their protocols in light of these new, powerful technologies. Proper collimation and using techniques appropriate for different areas of the body—such as varying dose from head to chest to abdomen to pelvis during a whole-body scan—are proving helpful in achieving ALARA. In addition, new solutions for dose recording and registration are rapidly being implemented in the new devices. 

The most important factors for dose reduction are the definition of policies and procedure, technique charts, training and education, as well as awareness. Healthcare IT can assist here, because an electronic health record could be used to record radiation dose events. This would allow it to be programmed to alert a physician before they order another CT scan or conventional X-ray. 

Dose reporting is critical to allow for benchmarking against yet-to-be defined national standards and good practices. The ACR is setting up several trial centers that will perform dose recording in order to establish a database from which to base to create standards. The IHE has defined the Radiation Exposure Monitoring profile that defines use cases and DICOM transactions to implement dose recording, which was demonstrated in its booth at the 2010 RSNA. 

The IHE profile uses a Dose Structured Report, which is defined by the DICOM standard and has a template for both X-ray and CT radiation dose. These templates contain information about the observer/system, date/time, and start and end of the event; the number of events that are recorded; and dose information. It also includes the method used to calculate and record the radiation event. This information can be sent to a PACS, RIS, or dose registry station, depending on the capabilities and architecture of the radiology imaging system. Dose reports can be sent, after anonymization, to an external registry. 

There are other short-term solutions to record the dose, none of which are optimal, but might provide an interim approach. One could, for example, capture a screen with the dose information, which can later be processed by an optical character recognition software package to extract the information. 

Other solutions could be the use of the DICOM MPPS dose information, which might not be as detailed and exact as the Structured Report (SR), but is better than nothing if the device does not yet support SR. Another solution, which is used by digital mammography, is to get this information from the DICOM image header. 

Both state and federal governments are taking dose management seriously—via legislation (notably in California), hearings, and FDA rule making. The MITA organization, representing imaging vendors, is also actively involved by defining guidelines and standards for dose reporting and registration. 

In conclusion, there is no question that because of regulatory and consumer pressure, X-ray radiation devices will be required to be modified, upgraded, and equipped with the capability to exchange dose information is a standard manner. Institutions will also have to store radiation events and dose details, most likely in the RIS, but also possibly in a PACS or separate application. Eventually, these events will become part of an electronic or personal health record. Imaging facilities are strongly urged to use standards for the implementation of dose management, in particular, the IHE Radiation Exposure Monitoring profile.