Dynamic Volume Imaging Reduces Radiation
Arizona locations only
The Aquilion ONE’s detector coverage is more than five times greater than that of a 64-slice scanner.
The Aquilion One 320-slice scanner's detector coverage is more than five times greater than that of a 64-slice device, and it can capture slices as wide as 16 cm in less than 1 second. "Full cardiac coverage with 320 detectors allows for the lowering of the radiation dose and improved temporal resolution, but there are several other advantages," explained Richard George, MD, assistant professor of medicine in Johns Hopkins' cardiology division. "The ability to image the heart over one heartbeat or less eliminates the need to reconstruct images over multiple heartbeats into a full cardiac volume. This eliminates step artifacts often seen with other scanners. Shorter scan times require lower contrast doses and fewer opportunities for motion artifacts secondary to patient movement."
"The 320 system is a striking improvement over the 256 prototype systems," said George. "While 256 detectors will cover most patients' hearts, the extension of the detector array from 256 to 320 detectors ensures that every patient will have their entire heart covered by the detector array. We're also very impressed with the improvements in processing time." George says the team at Johns Hopkins have also significantly reduced dosage, thanks to the scanner's improved resolution and imaging time: most CT angiograms require less than 5 mSv, depending on heart rate. Because it can safely image the whole brain, there are exciting implications for imaging of patients exhibiting stroke symptoms. The Aquilion ONE can rapidly acquire complete functional data with less radiation and contrast, speeding diagnosis. And patients with atrial fibrillation or frequent premature ventricular beats can now have a noninvasive angiogram using the system. "It is expected that the 320-slice CT scanner will be more accurate and applicable to a more diverse and complicated patient population than 64-detector technology," said George.
According to Dr. Tony DeFrance, Medical Director of CVCTA Education in San Francisco:
"We need to get the word out to the centers and I think education, ongoing dialogue, even site visits for people are important to optimize their radiation reduction strategies. Step one is measuring their doses. What we’ve done, and what's really changed our practice, is measuring the dose on every patient and recording it. That's the first step to awareness: knowing how much dose you're delivering. Then getting educated about the different dose reduction strategies, from dose modulation to prospective-gated imaging.
About a year-and-a-half ago, we were getting an average of 16 mSv. Since we've instituted our dose reduction strategy our average dose now is 6.8. It's just a matter of doing prospective imaging as much as possible, using dose modulation and really optimizing the scanner technology and parameters to do it. I think a lot of centers aren't using them -- they're just using retrospective on everyone. So the key is teaching these people that you can halve the dose or even decrease it by 80%.
Dr. DeFrance and CVCTA Education use the acronym LOWDOSE to summarize what CT centers need to think about:
- Length of scan minimized
- Optimized X-ray parameters and gating technique to the individual
- Working with vendors to optimize the system
- Dose Modulation
- Operator Training (CT Technologist and physician)
- Scrutinize the effective dose on each case
- Evaluate dose at regular intervals and implement changes to minimize it
What does that mean for patients?
- Less time on the CT table
- Exposure to less radiation and contrast dye
- Doctors can see every angle of the organ, along with blood flow and function
- Significant drop in the time needed to diagnosis and treat problems
Using a conventional CT scanner, such as 64-slice or 128-slice scanner, doctors may need to perform a series of tests to confirm a heart attack or stroke. Test results can take hours or even days. But in 20 minutes, the Aquilion ONE is able to diagnose a heart attack or stroke and can also gauge how badly tissue has been damaged so doctors can determine the proper treatment. The Aquilion ONE not only saves time, but it also helps reduce or eliminate the risks of unnecessary invasive procedures.
A conventional CT scanner has a viewing window of just a couple centimeters. To view the heart, the machine's sensors take a series of images that are built into a single, often distorted image. Think of it like trying to snap a panorama of the Grand Canyon on your camera phone, then stitching the pictures together. The Aquilion ONE can scan an entire organ in one rotation.
Faster is better: conventional CTs vs. Aquilion ONE CT
|Conventional CT||Aquilion ONE CT|
|Heart||7—10 rotations||1 rotation|
|Brain||7 rotations||1 rotation|
Aquilion ONE's high-speed scanning enables doctors to view crucial information such as blood flow and function in the heart, brain, joints and other parts of the body. These dynamic images are similar to real-time video of the organs, an incredibly helpful diagnosis tool that was previously unavailable. Aquilion ONE's dynamic images can:
- Show how a widely-spread cancer is responding to a drug, allowing patients to create tailored treatments based on a patient's response
- Provide a real-time image of a heart beat to identify blockage within the organ
- Monitor blood flow and oxygen levels in the brain to determine the risk of stroke
Diagnosing a heart condition can take hours and even days. Typically, patients undergo a multitude of tests to identify the problem, including EKGs, calcium studies, nuclear tests and catheterizations. Tests of this nature can take days to complete and expose the patient to significant radiation doses. With the Aquilion ONE, one exam gives doctors all the information they need to diagnose and treat the patient, with less exposure to radiation and contrast dye.
According to Radiology Today, an article published Nov 17, 2008-Dynamic Volume CT offers substantial advantages over multi-slice CT for both cardiac and cerebrovascular applications. For example, for a patient with a suspected stroke, a conventional 64 slice system involves acquiring a helical, non- contrast, static image of the brain followed by a static helical CT angiography with a total effective dose at 6 millisiieverts. Dynamic Volume CT allows full volumetric brain acquisition with a total effective dose of about 3 millisieverts. Dynamic imaging has the power to reduce the amount of radiation to which a patient is exposed. Another example is a patient who presents with chest pain is likely to be scheduled to complete a stress test, a CT angiography and a catheterization procedure, totaling approximately 42 millisieverts(i.e. absorbed dose equivalent) A cardiac image acquired with the Aquilion ONE has the potential to replace all three of these steps, saving the patient time and reducing the amount of exposure to less than 15 millisieverts.