Dose monitoring requires multi-pronged approach

Due to public concerns and regulatory scrutiny, medical imaging practices must be familiar with current radiation dose monitoring techniques and best practices, according to an article published online May 28 in the Journal of the American College of Radiology.

“A meaningful dose-monitoring strategy includes dose capture, effective dose conversion, patient-specific storage, institutional dose reporting, dose communication, and data export,” wrote Ronak K. Talati, MD, and colleagues from Stony Brook University Medical Center, Stony Brook, N.Y.

The authors broke down these six components, beginning with dose capture.

They explained that since most scanners burn dose data into PACS images, this image formatting information must be parsed by optical character recognition (OCR) algorithms. Alternately, dose-length product (DLP) and CT dose index (CTDIvol) calculation could be gathered by collecting DICOM headers per slice—tube voltage and tube current-time product—and accounting for pitch. Also, DLP values could be calculated by using tube voltage and tube current data and a lookup table for CTDIvol, explained Talati and colleagues.

“When fully supported, DICOM header messages under the [DICOM structured reporting] protocol provide an ideal method for dose capture from CT because DLP and CTDIvol values will be in numeric format in public DICOM header fields,” wrote the authors. “However, because a majority of CT scanners do not send DICOM-SR messages, doing so would require either new equipment or a costly infrastructure upgrade.”

Effective dose can be converted to millisievert values by multiplying DLP by a conversion factor, or k factor, which requires patient age and habitus, as well as exam type. Organ-specific values can be calculated using Monte Carlo simulation and phantom anatomic modeling, according to the authors.

With regard to storing exam information, Talati and colleagues said the best management system utilizes a distributed relation database that allows query-based reporting, and integrated with internal EMR systems through HL7 protocols. “Dose information should have internal references to identifying patient information such as medical record number or identifier, in a HIPAA-compliant manner.”

Real-time graphical displays of dose data and automatic flagging of scans with certain millisievert values can help optimize doses and identify problems, according to the authors.

Finally, an effective dose monitoring strategy must communicate dose information. At the referring physician level, this can be achieved through patient health records, radiology reports or direct communication with a referring physician. “Importantly, dose monitoring empowers radiologists and imaging centers to serve as ‘dose consultants’ by being able to query dose data for given patients. This is a value-added benefit to hospitals and referring physicians.”

On a wider scale, Talati and colleagues noted that a dose registry, such as the American College of Radiology’s Dose Index Registry, could provide multicenter, geographic dose data for the purpose of creating benchmarks for participating institutions.

“CT-related ionizing radiation exposure has been cited as the largest and fastest growing source of population-wide iatrogenic ionizing radiation exposure,” wrote the authors. “Upcoming federal regulations require imaging centers to familiarize themselves with available dose-monitoring techniques and implement comprehensive strategies to track patient dose, with particular emphasis on CT.”