SAN FRANCISCO - Is the California law requiring imaging facilities to report radiation dose to patients really working? Yes, but perhaps not in the way the legislation's authors had intended, according to a series of talks at the International Symposium on Multidetector-Row CT (MDCT).
A number of speakers in a Monday afternoon session agreed that the implementation of the California Radiation Protection Act (SB 1237) has been difficult for California imaging centers and hospitals, and, ultimately, the information patients are getting may not be very useful due to confusion over how to measure radiation and uncertainty about the health risks of radiation doses at the low levels used in medical imaging.
But MDCT 2014 speakers agreed that even if the law isn't working exactly as first intended, it has led to much-increased awareness of radiation dose in the state -- and that's a good thing.
Origins of the law
The California law was designed to prevent the type of shocking events that occurred in the state five years ago, including a 2009 case where more than 250 patients received too much radiation due to faulty CT protocols used at Cedars-Sinai Medical Center. There was also a 2008 incident at Mad River Community Hospital in Northern California in which a 2-year-old boy received the equivalent of 151 CT scans in just over an hour.
The California law is designed to address such incidents by informing patients of the dose they received from CT scans, so they will know if they were overexposed, presumably before symptoms appear. This information, specifically CT dose index volume (CTDIvol) and dose-length product (DLP), must be included in the radiology report.
The problem is that even radiology experts aren't sure exactly how dose should be recorded and reported, and there is nothing in the law to guide them. What's more, patients and even referring physicians don't know what CTDIvol and DLP values mean, according to Dr. Dominik Fleischmann of Stanford University.
"The referring physicians aren't really that happy with the information, and they don't know what to do with it," Fleischmann said. "One of our community physicians came up to me and said, 'Why do you dump all this information on us? Because I don't know what to do with it.' "
Imaging facilities also face uncertainty in how to report dose information, which by law must be included in the radiology report. But should dose information be dictated manually by the reporting radiologist -- a decidedly low-tech approach? Or should automated software be acquired -- a technically challenging endeavor?
Stanford eventually developed a template for dose reporting that is simple but also complies with the law. Radiologists there report CTDIvol for each diagnostic acquisition of given anatomy and total DLP. The university also performs an automated check of CT radiology reports for the presence of dose information (the university is 100% compliant) and checks the accuracy of reported dose values (it has achieved 95% accuracy, a number it hopes to improve upon).
"The good thing is that it really forces everybody to look at dose, and I think that's the most -- if not the only -- positive aspect of dose reporting," Fleischmann said.
Plastic patients?
Another problem is that the data derived from CTDIvol and DLP often don't reflect the true radiation dose that is delivered to patients, in particular for children, according to Dr. Richard Barth of Stanford. This is because most dose estimates are based on plastic phantoms that represent an idealized patient that rarely exists in real life.
"The only time these doses are accurate is if the patient you're scanning is made out of plastic and is the same shape as the phantom," Barth said.
Stanford researchers, in conjunction with the California Radiological Society, conducted a survey in September 2013 that assessed the understanding and attitude of radiologists toward the dose reporting law. The group received responses from 137 centers, of which 115 (84%) were private practices and 22 (16%) were academic.
Some 45% of facilities said that dose reporting as required by the law raised their awareness of appropriate dose ranges, while 22% said they had made a change in CT protocols, such as mAs or kVp. In addition, 21% said they had modified their CT protocols based on a patient's age or weight.
In all, 19% said they were using an automated system to incorporate dose levels into their radiology reports, 37% said they relied on transcription, and 44% were using templates to report dose. Finally, 30% of respondents said the law's requirements had resulted in delays in reporting dose, most likely related to dictation.
"California radiologists are largely aware of the legal requirements; the survey indicates that the law has increased awareness amongst radiologists on dose issues, and some practices have attributed [to it] modification of protocols in both children and adults," Barth said. "I do think it has had a positive impact, not doing necessarily what it was intended to do, in terms of avoiding overdoses on occasion, but it definitively has raised awareness."
The UC Dose Project
Indeed, the law was the impetus for a major project at the University of California to better understand and control radiation dose in the university's healthcare system, according to Robert Gould, ScD, of the University of California, San Francisco (UCSF).
Shortly after the law was passed in 2010, the university system created the UC Dose Project, headed by Dr. Rebecca Smith-Bindman and involving all five UC medical schools. Its goals are as follows:
- Develop consensus on the best way to assess and report dose information to comply with the law
- Benchmark CT doses in UC medical centers
- Establish standardized CT protocols
- Educate UC staff and the wider community about CT radiation dose reduction
The project published a guidance document on dose reporting, automated its dose reporting using commercially available software (Radimetrics, Bayer HealthCare), and held a virtual meeting in May 2013. It is also in the process of standardizing its CT scanning protocols, which Gould acknowledged is a "daunting task" given the wide variety of scanners in use at the five academic centers.
All UC centers are feeding their scan results into a centralized, anonymized database, which now has more than 20,000 CT studies stored. The database has enabled the identification of trends such as variations in DLP levels: At the low end, one UC site has an average DLP of 582 mGy-cm, while at the other end of the scale, one site has reported an average DLP of 1,277 mGy-cm.
In the end, did the law succeed in increasing patient safety? Gould agrees with Barth: It has, but not for the reasons initially stated.
"It really helped focus attention on CT dose, it led to a better understanding of CT dose parameters, but it had very little direct impact," Gould concluded.
