Ureteral Stones: Reduced-Dose CT Protocol in the Emergency Department

This recent article from Radiology reports the use of an 80% reduced dose CT protocol for assessing moderate to high risk patients for ureteral stones in an ED environment.

Reduced dose CT was correct for stone versus no stone in 100% of 108 patients. Dose reduction was achieved by lowering both the mAs and the kVp and adding iterative reconstruction.

CT colonography

Using model-based iterative reconstruction, CT colonography can be a very low radiation dose method of screening. This article applauds the United States Preventive Services Task Force (USPSTF) approval, cited as a “big win for patients.”

RSNA 2011 Relections

RSNA (Radiological Society of North America) is the largest annual trade show in the world, with about 55,000 people in attendance for the 6 day event in Chicago, Illinois. The expo includes a large number of presentations and courses on science and modern radiology.

RSNA 2011’s two main themes were lower radiation dose in diagnostic radiology imaging (especially CT) and new technology. For lower dose, there was much material on tailoring a CT scan exactly to an individual patient – based on their body size, their cardiac output, their disease process, or the type of diagnostic challenge. Additionally, a lot about new iterative reconstructions in CT – both statistical and model based, was presented. Either method lowers dose a lot, but model based results in lowered radiation exposure by up to 80%.

New technology presentations and courses covered a range of topics including dual energy CT for better tissue characterization, and the combination of imaging modalities in one platform – like SPECT/CT, or PET/MR. These combined modalities may provide a better combination of disease identification plus precise localization.

In all, RSNA 2011 offered great insights and interesting presentations. Did you attend? Share your thoughts below!

RSNA 2011: Don’t Miss Out!

The RSNA 2011 conference marks the 97th Scientific Assembly and Annual Meeting. This event, the world’s premier medical meeting for radiologic professionals, is being held on November 27 through December 2 at the McCormick Place in Chicago. The annual conference includes unparalleled education and professional development, networking opportunities, and a cutting- edge technical exhibition.

I will be involved in a number of events, both as a presenter and an author. The presentations that I will be involved in include:

• Presenter- Hot Topics: Dual- Energy CT on Tuesday, November 29 from 7:15 am to 8:15 am.

• Presenter- Refresher: Mind Your Own Business! Required Business Skills for Your First Job on Thursday, December 1 from 4:30 pm- 6:00 pm.

• Author/ Participant- Gastrointestinal Series: Scientific Formal Presentation (Dual-Energy CT of Hypervascular Liver Lesions: Evaluation of Lesion Contrast-to-Noise with Different Monochromatic keV Reconstructed Images) on Monday, November 28 from 9:50 am to 10:00 am.

• Author/ Participant- ISP- Health Services, Policy, and Research- Scientific Formal Presentation (Patient Knowledge and Perceptions about Radiation from Diagnostic Imaging) on Monday, November 28 from 3:30 pm to 3:40 pm.

• Author/ Participant- Neuroradiology Series: Stroke Imaging- Scientific Formal Presentation (Changes in the Measured Size of Atherosclerotic Plaque Calcifications in Dual-Energy CT of ex Vivo Carotid Endarterectomy Specimens: The Affect of Different Monochromatic keV Image Reconstructions) on Wednesday, November 30 from 11:00 am to 11:10 am.

For more information about RSNA 2011 and the presentations that I’ll be involved in, please see the meeting program.

Do Patients Understand CT Scan Risks?

An article that was published after RSNA talks about a study that found that CT scan radiation risk in patients may be overblown. However, at the close of the article, it says that longer-term, more in-depth study is needed. Until then, physicians and patients still need to weigh the risks and benefits of CT.

For patients to both be informed and to understand (comprehend) risk related to radiation is very challenging. This is because there are few comparables in normal daily life which can clearly quantify extremely small risks. The one I like the most is: 10 mSv give you a risk of dying from an induced cancer of about 1 in 4000. Driving a car in the USA for 80,000 miles over 3 years also gives you a risk of about 1 in 4000 of dying in a car accident.

Now, both a CT scan with 10 mSv and 80,000 miles of use of a car bring certain benefits. But they carry a risk of dying of 1 in 4000. What do you think of that risk/benefit ratio? Would that ratio make you stop driving a car?

Year’s Biggest Advancement in CT Technology?

I recently came across this video from RSNA. About halfway in, they ask the question, “What is the biggest advancement in CT technology this year?”

I would agree with Dr. Siegel that iterative reconstruction has stimulated thinking and conversation among radiologists about how to substantially lower CT dose without compromising the benefits of CT. Based on our 18 months of experience, we know the reduction is at least 40 percent with the current version of iterative reconstruction. And we suspect much greater reductions are coming. Some of the issues centers around radiologists’ “preferences” for how a CT images looks. But preferences can change, even dramatically, when driven by the hope of much lower patient dose.

What do you think – what do you view as the biggest advancement in CT?

Obligation to Patients: Minimize Risk and Maximize Benefit

One of the most exciting – and talked about – sessions at RSNA was called “Radiation Dose: Can It Be Too Low?” The expert panel had a healthy debate on radiation dose and risk, and finally reached an agreement that CT scans should be limited to “justified and optimized studies.” (HealthImaging.com has a good recap of the panel’s discussion.)

The debate about risk can go on, but when practicing medicine (radiology) with real patients, the obligation is to both minimize risk AND maximize benefit.

So the challenge for radiologists is to lower dose as much as possible without compromising the amazing diagnostic power of CT. How to accomplish this is both science and art. But we have discovered at UW that with a combination of low dose technique and low dose CT technology, you can take out up to 40 percent of the radiation dose to the patient (compared to 3 years ago) without having any negative impact on diagnosis. So that number certainly is achievable at most sites.

Could we go even further in dose reduction?

Stay tuned…