CT Dose Reporting in California

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John BooneMany of the accidents that spurred press coverage of CT overdoses in recent years occurred in California. This led to enactment of the state’s SB 1237 (and subsequent cleanup legislation), which will take effect on July 1, 2012. The law’s basic provisions are that the so-called CT dose—the volumetric CT dose index and the dose–length product—must be recorded in the interpreting physician’s report and that the volumetric CT dose index reported on the CT scanner console needs to be within 20% of the volumetric CT dose index measured by a medical physicist each year (for a few of the most common CT protocols). Additional provisions apply to radiation therapy. The state is to be notified if:

  • a fetal dose event of over 50 mSv occurs, if the patient was known to be pregnant and if the procedure was not approved in advance by a physician;
  • except in the case of patient motion, a repeated CT procedure occurs that was not ordered by a physician and that results in an effective dose of more than 50 mSv (to the whole body) or 500 mSv (to an organ/tissue or to the skin);
  • an exposure occurs to the wrong body part and an effective dose of more than 50 mSv (to the whole body) or 500 mSv (to an organ/tissue or to the skin) is reached; or
  • CT exposures occur that result in unanticipated epilation/erythema or permanent damage to organ function.

The California Scramble Since this law was signed, many radiology departments in California have been scrambling to try to meet its requirements. The meat of the legislation is not what has spurred the most effort. In order to know whether a patient has had so-called doses that exceed the reporting limits, the provider has to record and keep track of the so-called doses. I use the term so-called dose because the law states that for each patient undergoing a CT scan, the volumetric CT dose index and dose–length product must be recorded. These are not doses; they are dose indices—which, in many cases, are not accurate measures of patient dose.1 While many patients have a single CT scan, with or without contrast (with one dose–length product and one volumetric CT dose index), some patients have chest, abdomen, and pelvis CT scans—some with and some without contrast. A three-phase liver CT exam, for example, requires numerous individual scans, each generating its own volumetric CT dose index and dose–length product. For contrast CT studies, there are also bolus-monitoring procedures that qualify as an individual CT scan series. In some cases, the sum of the volumetric CT dose index and dose–length product are being recorded; while that might meet the letter of the law, in many cases, it leaves significant ambiguity in the recorded data, should a medical physicist have to estimate patient dose for those procedures. I strongly advocate recording a series-by-series breakdown of volumetric CT dose index and dose–length product. At many institutions, it has been anticipated that the radiologist would simply dictate the volumetric CT dose index and dose–length product into the report, but such an approach is inefficient and can lead to inaccurate, inconsistent reporting. Many radiologists would be likely to resist such an approach. Many institutions are moving toward an IT solution that will both let them comply with the law and eventually add efficiency to report generation. The law mandates that the volumetric CT dose index and dose–length product be passed from the PACS to the radiology report—but once this channel of communication has been established, why stop there? The technical information associated with the CT scan (such as protocol parameters and, in some cases, contrast-injection parameters) is available. These data could and should be automatically communicated between PACS and RIS. This data transfer could then be extended to structured reports for MRI exams and other imaging procedures as well. Fissures Revealed The recent focus on CT dose reporting has revealed a number of issues that should be addressed in radiology facilities. For example, in many facilities, the name used for a given CT protocol differs between scanners. This makes it difficult for a facility (or dose registry) to get a handle on CT doses between CT scanners, and some work is then required to rename protocols consistently or to remap them in software so that they are tallied uniformly. The California CT dose legislation has created a market for software companies working at the IT level in radiology, and several companies