|Contrast is injected and monitored during a cardiac computed tomography angiography procedure using Toshiba America Medical System’s 64-slice Aquilion CT at Steinberg Diagnostic Medical Imaging Centers in Las Vegas.|
Thanks to new, more intelligent interfacing capabilities based on new open software protocols, next-generation contrast injectors support more complex injection protocols and integrate with information systems, while keeping pace with increasing CT scanner speeds.
Not just a ‘power injector’
With more precise timing of contrast delivery, extravasation detection, and a more robust connection between injectors and scanners, next-generation contrast delivery systems are no longer just power injectors. “Contrast injectors are getting better, safer, and more programmable,” says Joel Platt, MD, head of the abdominal radiology division at the University of Michigan School of Medicine. “We want a power injector to be safe, reliable, and smart.”
Safety has improved with the ability to deliver only the contrast required. In the rare, but serious event of extravasation, a sensing system can detect a mild pooling of the blood before the extravasation becomes moderate or severe. Medrad just announced a new extravasation system that uses RF (radio frequency) to detect minor pooling of blood, stop injection, and notify the user. More precise timing also provides the ability to deliver only the needed amount of contrast, reducing the risk of contrast nephropathy in certain patients, and makes the CT procedure more comfortable with reduced scanning times. “Safety and reliability improve as contrast injectors get smarter and we get smarter about how to use them,” Platt says.
Dean Langwiser, CT technologist in the cardiac cath lab at University of California, Irvine, a show site for Medrad, will be one of the first to use Medrad’s new XDS extravasation detector. “We’re injecting 4ccs a second and we have a 10-second window from the start of the injection until we start scanning,” he explains. Halfway through the scan, the patient starts getting saline instead of contrast. “It’s a very different viscosity so it often builds up back pressure which prevents the patients from getting about 50ccs of saline.” That results in a lot of pain and the potential for compartment syndrome. Although that doesn’t happen as much as it used to, Langwiser says, it still occurs in about one in 50 patients. “To me, that’s a substantial number. It affects the scan. The discomfort causes the patient to move and it also prevents full washout of the right side of the heart.”
Langwiser says the new technology shouldn’t affect workflow at all. “It’s just a matter of putting a patch over the injection site. This is something I’ve always been hoping they’d come up with.”
Reliability has continued to improve with the better image quality that comes with consistent contrast medium delivery. In addition to the steady improvements in image quality provided by automated injection, better and faster scanners are reducing the window between contrast injection and the start of imaging, driving the need for faster, more precise contrast injection timing. Software-driven injection is particularly key for time-critical CT angiography (CTA) procedures.
In CT, injectors can manage the simultaneous injection of saline and contrast and help manage contrast attenuation to optimize visualization of the right and left heart. Injectors now provide multi-phase protocols that allow consistent opacification of the heart without causing artifacts that make it difficult to read the coronary arteries. The Stellant Dual Flow system from Medrad delivers contrast in three phases: first a contrast bolus, then a mixture of contrast and saline, and finally, an injection of 100 percent saline. Adding the middle phase reduces the contrast attenuation, providing matching opacification on both the right and left sides.
Robin Brothers, CT technologist at the Medical University of South Carolina in Charleston, uses Medrad’s CT interface device for Stellant CT Injection Systems (formerly known as iFlow) that, with the push of a button, starts both the scanner and the injector at the same time. Before the interface, one person had to be in the control room to start the scanner and someone else had to be in the room with the patient watching the IV. So, this helps improve throughput. Because multislice scanners capture images so quickly, having optimal contrast in the area of interest at