Wednesday, November 24, 2010

Dose Matters at RSNA 2010

Summary: Look for vendors offering the NEMA X-25 Dose Check feature and DICOM Radiation Dose SR (RDSR) (IHE REM profile) output from their CT modalities, and products able to store and process RDSRs for dose monitoring, alerting and registry submission. Bring along a list of your installed base of CT, PACS and RIS model and version numbers, and ask your vendors when Dose Check and RDSR capability will be supported. Don't forget to ask your PACS, CD burning and importing, cloud/Internet storage and distribution, Modality Worklist (MWL), reporting system, ordering and decision support vendors about this too. Visit the RSNA dose demo at Booth 2852, Exhibit Hall A, South Building.

Long Version:

In my last blog entry, I discussed the need for tools for monitoring and controlling radiation dose from CT, and with RSNA's Annual Scientific Pilgrimage to Chicago coming up next week, I thought I would consider the progress in the last six months, and what attendees might want to focus on. Undoubtedly the CT vendors will be heavily focused on what new dose-reduction technology they can deliver in new products, but do not lose sight of the importance of evaluating the monitoring and management technology as well.

One notable event was the release in November of a public letter from the FDA to MITA (NEMA), the vendors' trade organization, summarizing their investigation of the brain perfusion incidents.

In October, NEMA released the X-25 Computed Tomography Dose Check standard, which you can download from here. This feature, which the vendors had already committed at the FDA Public Meeting to develop and implement, is intended to "notify and alert the operating personnel ... that prepare and set the scan parameters — prior to starting a scan — whether the estimated dose index is above the value defined and set by the ... institution ... to warrant notification to the operator". Clearly this requires two things, 1) the implementation of the feature in the scanner, and 2) suitable values to be configured by the institution. No doubt the vendors will promulgate default levels, and organizations like AAPM or ACR might provide them, or the local medical physicists may decide for themselves. Eventually the X-25 feature will get folded into the CT manufacturer's safety bible, IEC 60601-2-44.

The RSNA meeting will be an opportunity for you to ask the CT sales people and application specialists about the Dose Check feature, and particularly how and when they plan to retrofit the scanners you already have installed to support it and how much it will cost (if anything). A commitment to the FDA is one thing, but there is nothing like evidence of demand from the customers to motivate product managers to deliver.

X-25 distinguishes between "notifications" for "protocol elements" prior to scanning, and alerts for the "examination" that accumulate what has been done so far. There is also an alert prior to saving (not just attempting to perform) a protocol that exceeds limits, which specifically helps to address a concern that arose in the Cedars-Sinai perfusion incident. Proceeding despite a notification or alert requires the recording of who, what, when and why in an audit trail. DICOM is working on additional information to be included in the Radiation Dose Structured Report (RDSR) to record the X-25 parameters and audit trail information (see CP 1047). You might also want to ask the modality vendors at RSNA when they plan to implement CP 1047, which should be made final text at the Jan 2011 WG 6 meeting. If you are looking for dose monitoring systems that can process RDSRs, you might also want to ask them about when they plan to be able to provide you with a human-readable report of CP 1047 X-25 events.

On the subject of RDSR, one vendor, GE, has already provided a list of which models and versions of scanner support RDSR, and which earlier models produce dose screen secondary capture images; you can find the list here. Hopefully other vendors, perhaps at RSNA, will provide a similar list, and I will tabulate them on the Radiation Dose Informatics web site on the Software and Devices page. In lieu of information supplied by the vendors, I will also tabulate information based on what scanners and models that I encounter RDSR objects from, so feel free to submit samples to me if you encounter them.

When shopping for new CT scanners or upgrades next week, asking the vendors for RDSR support is something obvious that you should do, but even if you are not buying new equipment, it is reasonable to ask about upgrading your installed base. If I were you, I would bring along a complete list of all the equipment that I was responsible for including models and versions, and ask very specifically of the sales people, which of those on my list can be upgraded, and when, and which of those will never be upgraded. Not only will this serve to alert the product managers to your concern about this issue, but the answers will help you plan your own dose monitoring strategy. If you don't get the answer that you want to hear (all your scanners will soon support RDSR), then you are going to need to develop a strategy that perhaps involves a third-party solution that can either OCR the dose screens if the scanners produce them, or provides a means for operator data entry and transcription of the information displayed on the console.

As for "dose monitoring systems", or whatever the name the industry is going to converge on for monitoring and reporting CT scanner dose output, the upcoming RSNA is an opportunity to look around for vendors of those systems too. It remains to be seen whether this feature becomes routinely embedded in the PACS or the RIS, or whether for the time being or indefinitely, it will be the province of dedicated third-party systems (I will maintain a list of the latter at the Software and Devices page, which is, so far, depressingly short).

In the IHE REM profile, the modality can send RDSRs either to the Image Manager/Image Archive (IM/IA) (usually the PACS) or directly to a Dose Information Reporter (DIR), which might be the RIS or a third-party system, or such a system may query the PACS. The REM design assumes that since RDSRs are DICOM objects, the PACS is the logical actor to persist and distribute them.

However, RDSR output from the modality is not going to be of much immediate use to you if a) your PACS won't accept and store them, and b) you don't have something that will display their content and, more importantly, produce management reports of dose output, if not alerts and notifications when limits are exceeded. At the very worst, you can start storing these RDSRs in the PACS now, so that when you do settle on a dose management solution, you will be able to use your historical data, as both a benchmark for your local historical practice, as well as for individual patient dose management decisions (recognizing the limitations of using dose output as a surrogate for effective dose to the patient).

Accordingly, not only do you need to be asking your CT vendor for RDSR output, but you need to be asking your PACS vendor if they will accept, store and faithfully regurgitate RDSRs, even if they do not yet have plans to render and collate the contents.

This also includes recording RDSRs on CDs, since referring physicians want to know about dose too, as does the next facility in the chain that is going to import these CDs. So your third-party CD burning and import and viewer vendors are also candidates for interrogation next week about RDSR support. You also need to ask any Internet distribution and storage vendors offering "CD substitutes" in the "cloud" about this too.

Your RIS vendor doesn't escape either. Though they may not be planning on offering RDSR management, they will still be providing Modality Worklists (MWL) to the CT scanners. It turns out that it is really important to convey the age, sex, height and weight information, as well as anatomic and procedure codes, if downstream one is to make size-appropriate use of the dose output information (which after all is based on standard sized phantoms and needs adjustment for kids and for particularly small or large people). The CT scanner vendors are well aware of these issues, and hopefully can reliably copy the information from the worklist into the RDSR (another question to ask your scanner vendor if you want to get into that much detail with them).

Finally, when generating the radiology report, it is good practice if not required by regulation (such as in Germany or now California with SB 1237), to include information about the radiation dose, and a creative reporting system vendor could automatically copy information directly from the RDSR for the study into the report template being populated by the radiologist. Now is the time to get the reporting system vendors thinking about this, particularly since some of them already offer features for doing the same sort of thing from other types of structured report "input", notably for ultrasound and echocardiography. Even the ordering and decision support system vendors should not be immune to your questions, since they too can take advantage of patient-specific historical information acquired from RDSRs.

In conclusion, next week you have the opportunity to put penetrating questions about radiation dose to everyone you meet with a product that is involved in any part of the imaging chain, from ordering all the way through to reporting.

If you want to get a more detailed briefing, perhaps prior to visiting the vendors' booths, and see some of the components of the IHE REM profile in action, feel free to come and visit the RSNA Image Sharing and Radiation Dose Monitoring demonstration. A group of CT modality, PACS and dose reporting vendors, together with some academic groups, the ACR and myself will be participating. Strangely enough this will actually be held in the Technical Exhibits area, rather than in the Lakeside Learning Center, specifically Booth 2852, Exhibit Hall A, South Building. Email me if you can't find the demo or have any questions about it.


PS. By the way, while I am thinking of it, if you use lossy compression in your archive, make sure it is turned off for series that contain dose screens (or indeed any secondary captures containing text and graphics like perfusion curves), since not only will it make them look like crap but will also reduce the performance, if not entirely cripple, any OCR that you might later apply.

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