The value of computed tomography (CT) scanning is unquestionable. A clear CT scan provides physicians with the detailed information they need to diagnose conditions, plan surgical intervention or monitor treatment. One area of increasing demand for CT imaging is in pediatrics, for children who have chronic diseases such as cystic fibrosis or congenital heart disease.
There has always been a trade-off with regard to CT image quality. A higher radiation dose in a CT examination results in a clearer image, but a higher dose also increases the patient’s long-term health risk. In pediatric medicine, attention to dose is doubly important. Children have smaller bodies, and their tissues are more sensitive to radiation than an adult’s. Moreover, as children are in the early stages of life, they are more likely to need additional scans in the future, which means a higher cumulative exposure during their lifetime. So pediatric radiologists need to be vigilant in keeping the dose as low as possible, while assuring that the acquired image gives physicians the level of detail they need to understand what is happening inside the body.
The tug-of-war between dose and image quality is changing, however. New advanced reconstruction technologies are able to produce far better images from CT scans that are acquired using a lower dose, and GE Healthcare is leading the way in bringing these tools to hospitals around the world.
At the International Paediatric Radiology (IPR) Congress held at the end of May in London, thousands of radiologists gathered to learn about the latest techniques and product advances. The issue of dose reduction was omnipresent.
“Dose reduction has been a hot issue for a long time, but right now things are moving,” says Dr Caroline Ernst, head of pediatric radiology at UZ Brussel in Brussels, Belgium. “Until recently, we had reached the limits of dose reduction with the existing technology, but now we’re seeing some real evolution with the introduction of iterative reconstruction technologies.”
The Evolution of CT Dose Reduction
GE Healthcare has introduced several ground-breaking approaches to dose reduction in recent years, some of which were showcased at the 2011 IPR Congress.
Adaptive statistical iterative reconstruction (ASiR)* is an image reconstruction technique that reduces noise and improves image quality. GE Healthcare was the first company to introduce this kind of technology in CT, using an iterative statistical image reconstruction algorithm to generate equal or better images from lower-dose CT scans. Introduced in 2008, ASiR was the first big step in terms of dose reduction and image quality improvement. ASiR models the noise in the raw CT data and, through multiple iterations, filters it out for a clearer final image.
Dr Fahad Al-Habshan is a consultant in pediatric cardiology and cardiac imaging at King Abdulaziz Cardiac Centre, a tertiary care cardiac centre in Riyadh, Saudi Arabia, that conducts approximately 400 open heart procedures on children every year.
“Open heart surgery in a small baby requires an accurate and precise diagnosis, and the surgeon needs to plan what he is going to do,” Al-Habshan says. “It is not good to have a surprise in the operating room and find something new, because every additional minute of surgery can increase the complications for very young patients.”
Before upgrading their CT systems with ASiR in 2009, Al-Habshan’s team tried to lower the imaging dose, but ended up with images that were noisy and hazy. “With ASiR, we were able to get the same quality of images but with a much lower dose because ASiR filters out the noise, and produces much more crisp images than using a lower dose without ASiR,” he says. “Almost all of our children nowadays are imaged with less than 1 mSv of radiation dose, while before they used to get 3–5 mSv or even up to 10 mSv in older children who underwent retrospectively gated CT angiography.”
More than 1,000 sites are using ASiR today, but GE Healthcare has not rested on its laurels. The company has set the bar again for innovations in image reconstruction with a product called Veo**. Available today in Europe, Japan and Canada, Veo is the world’s first model-based iterative reconstruction product for CT, offering less noise and higher resolution within a single image, and offers additional capability for cases where the highest image quality at the lowest dose is required.
One of the first adopters of Veo was the pediatric imaging department at UZ Brussel, earlier this year. The facility sees up to 300 children with cystic fibrosis each year, among many others, and this patient group typically undergoes a CT exam every other year, with a chest X-ray on alternate years.
“Children are two to ten times more sensitive to radiation dose than adults, depending on their age,” Ernst says. “So what Veo gives us, in pediatric imaging, is a diagnostic-quality image from a significantly lower-dose acquisition.”
Veo is enabling UZ Brussel to offer CT imaging of the chest with an estimated effective dose of 0.04 mSv, which is just slightly higher than the average chest X-ray dose of 0.03 mSv, according to Ernst.
“With such a dose, Veo could potentially replace the conventional chest X-ray in certain indications, although further investigation and validation is needed. We are currently trying to make sure all of our pediatric patients benifit from this new CT technology.”
Although Veo has only recently become available in a limited number of countries, Olivier Adda, product manager for the Discovery CT750 at GE Healthcare, is bullish.
“Consider that no one knew what ASiR was when we first introduced it only a few years ago, and now it is becoming a standard,” Adda says. “Veo is the ultimate advance in image reconstruction, and it is beginning to rewrite the rules of CT.”
*ASiR is available on Discovery, Optima, BrigthSpeed and LightSpeed CT products.
**Introduced on Discovery CT750 HD. Veo is 510(k) pending at FDA. Not available for sale in the USA.