As if it isn’t incredible enough that we can look inside the human body without breaking the skin, GE’s latest computed tomography scanner, the Revolution CT, achieves revolutionary clarity of internal imaging at radiation doses up to 82% lower than were previously required to achieve images half as clear. It captures its images within fractions of a second, enabling a diagnostic view inside previously unscannable patients: those with rapid or irregular heartbeats, for example.
The potential for saving time, unnecessary trauma, money, hospital resources and lives is both measurable and movingly anecdotal. The Revolution CT has this year been installed in five locations across Australia and New Zealand. The earliest adopter, interventional radiologist Glen Schlaphoff and his team at Spectrum Medical Imaging in Liverpool, NSW, are using it to do ground-breaking work in cardiac imaging.
We’re going in!
The patient has an extremely irregular heartbeat—it jumps between 53 to 126 beats per minute. “In the past,” says Kevin Waldon, an experienced radiographer at Spectrum, “We would have seen this guy and thought, ‘There’s no way…’ I would have called Glen and asked whether we should even be attempting it, and he would have called the referring cardiologist…” Instead, given the Revolution’s capabilities, Waldon confidently administers the routine injection of “contrast” or iodine, which is used to highlight the blood vessels in the heart for the resulting image.
The patient lies on the narrow cushioned bed as it slides into the magic circle: the pale, softly glowing iced doughnut of the scanner. The Revolution’s expanded bore, at 80cm, is a mighty big doughnut which means there’s less likelihood that the patient will feel claustrophobic. The machine whirrs—considering that inside the doughnut more than a tonne of machinery is doing one complete turn around the patient every 0.28 seconds, it is amazingly quiet.
It has been virtually impossible to capture a clear diagnostic image of the heart in patients whose heart rate is extremely irregular. This vividly clear image, taken on GE’s Revolution CT scanner by Spectrum Medical Imaging in Liverpool, NSW, shows the condition of a heart (and its blood vessels) that was beating at between 53 bpm and 126 bpm at the time of scanning. The Revolution CT successfully judged its fraction-of-a-second opportunity.
The Revolution registers the wildly varying contractions between the patient’s heartbeats. Says Schlaphoff, “The thing is spinning, spinning, spinning, just watching, and it starts getting an idea that there’s a gap coming up, then phwataaa! That’s the shot!”
The resulting image of this patient’s heart is the same quality as the Revolution would capture of an organ beating steadily, predictably at 60 bpm. It is so stunningly clear that it could be an anatomical drawing, glowing, showing in this case no coronary disease.
It’s as if nothing much has happened…
But, this patient, who had suspected coronary disease has, within 10 to 30 trauma-free minutes of preparation, 0.14 seconds of imaging and another 10 minutes or so of image construction, been cleared of the need for further coronary investigation.
The Revolution’s expanded bore, at 80cm, is a mighty big doughnut which means there’s less likelihood that the patient will feel claustrophobic.
In the past, any CT scan of his heart would have been compromised by his uncontrollable heartbeat. The image may have been unreadable, inconclusive. He may have endured weeks or months of uncertainty, being sent instead for less conclusive ultrasound or magnetic resonance imaging (MRI). More likely, having been deemed unsuitable for CT, he would have had to undergo invasive coronary angiography—in which a catheter is inserted through an incision in the groin or elbow and manoeuvred up an artery until it reaches the heart, where it injects a dye directly into the coronary arteries in preparation for an x-ray image to be taken to show the condition of heart and vessels.
Studies carried out in the US indicate that about 15% of patients who would benefit from coronary computed tomography angiography (CCTA) to assess their condition are too challenging or simply unsuitable for the procedure as was available on the previous generation of scanners. Other courses of investigation used to assess possible heart disease require correlation of various tests that can never be as clear CT imaging.
“It’s a significant reduction of the burden on healthcare when you can put these patients onto the right path immediately,” says Samantha Barr, GE’s product marketing leader for Premium CT in the Asia Pacific region.
An erratic heartbeat is just one of the contraindications for using CCTA. Other conditions that can render a patient unsuitable include rapid heartbeat and atrial fibrillation—a disturbance of the heart’s electrical system that causes the upper chambers of the heart to quiver rather than pump normally. People—most frequently young children—who can’t hold their breath for the 5 to 15 seconds required by most scanners to capture a clear picture have also been near impossible to scan.
Breathing, or quivering or fast heart rates that cause constant movement of vessels result in images similar to what happens when you use a camera on slow shutter speed to take a photo of a friend doing star jumps.
The majority of CT scanners in use can only capture compromised images of the hearts of such patients. “With the older generation of machines, if someone has a faster heart rate, it would be done over three to four heartbeats and then you’d piece the image back together,” explains Waldon. This, he adds can result in “misregistration artefacts—if there is a variation in the heartbeat, it doesn’t line up and you get blurring of the vessels”.
He says Spectrum’s team of radiographers, “Almost cried when we realised how much time it [the Revolution CT] would save us, and that we could scan everyone.”
Schlaphoff and Waldon say the Revolution CT offers several advantages over older models of scanner. The speed of the scanner—that 0.28-second rotation—is one thing, but the temporal resolution is also supported by Snapshot Freeze, GE’s intelligent motion-correction software, which allows the machine to easily be programmed to respond to different patient conditions. Importantly, the size of the Rev CT’s image detector, at 16 centimetres, is four times the size of most other CT detectors, which means it can capture an image of the whole heart in one revolution and in one heartbeat—rather than taking four image strips that later need to be assembled. This also reduces the ionising radiation (the part of the electromagnetic spectrum with sufficient energy to pass through matter) required to achieve an image—it’s achieved during one pass of the detector rather than four.
Radiation dose has long been a barrier to the use of CT, particularly for young people who have a greater chance of developing cancer due to radiation within their lifetime, and for young women with heart problems, whose breast tissue would have been put at risk by canning of the chest with previous CT machines.
“This young woman was only 21,” says Waldon, showing a vividly clear 3D image of a heart and turning it through 360 degrees. She’s got this minor heart defect, it’s like a fistula, an abnormal communication between two of the vessels in the chest and we were able to show it with really low-dose imaging.”
In adjusting the settings of the Revolution CT, the Spectrum team has found it can achieve extremely high quality images with radiation doses as low as a single x-ray—that, says Schlaphoff, equates to the same radiation you’d receive on a flight from Australia to the US.
“It’s satisfying to know, when people leave, that we’ve done no harm to them,” says Waldon. “You’re able to keep the doses low, but still answer the question that the doctor was asking, even in the most challenging of patients.”