Imaging

The dawning of a new era

The incredibly fast 64-slice Computed Tomography scanner is being hailed for initiating a new age of medical imaging. This incredible piece of technology is revolutionising diagnosis in cardiology, oncology, neurology and may other areas. Middle East Health looks at four of these scanners.

The 64-slice Computed Tomography (CT) scanner, the latest generation in a line of CT scanners stretching back about 15 years, is revolutionising non-invasive diagnosis. These machines, as if in a world of science fiction, can scan the whole body in seconds and provide incredibly sharp 3D images of any organ.

The new 64-slice scanner is changing the face of diagnosis. The scanner’s ability to quickly and non-invasively spot small tumours, in a check on the lungs for example, or plaque in the case of cardio-vascular disease, is making it the preferred option for diagnosis by an increasing number of physicians, rather than the invasive, time-consuming and more risky diagnostic procedures that have been used traditionally.

The invention of computed tomography is considered to be the greatest innovation in the field of radiology since the discovery of x-rays. This cross-sectional imaging technique provided diagnostic radiology with better insight into the pathogenesis of the body, thereby increasing the chances of recovery. In 1979, GN Hounsfield and AM Cormack were awarded the Nobel Prize in medicine for the invention of CT.

CT is now one of the most important methods of radiological diagnosis. It delivers non-superimposed, cross-sectional images of the body, which can show smaller contrast differences than conventional x-ray images. This allows better visualisation of specific differently structured soft-tissue regions, for example, which could otherwise not be visualised satisfactorily.

Since the introduction of spiral, or volume CT, in the 1990s, computed tomography has seen a constant succession of innovations. The development of slipring technology allowed for a continuously rotating gantry – the prerequisite for spiral CT.

The first multi-slice CT scanners were in operation by the early 1990s. The original Elscint-Twin scanner, introduced in 1994, allowed acquisition of two images simultaneously through a dual detector array. The four slice scanner was introduced in 1998. With the introduction of the 16-slice scanner, taking a scan of the heart, for example, would take 20 to 25 seconds to collect all the data. However, these images were still subject to motion artifacts, reducing their diagnostic clarity, due to the patient having to breathe during the scan period. But with the introduction of the 64-slice scanner nearly all patients can be scanned with very high resolution in just a few seconds. Scan times are generally between only five and thirteen seconds. This means that even patients with severe pulmonary disease and congestive heart failure can hold their breath for the length of the scan period which results in minimal or no motion artifacts in the image.

The multi-detector scanners can be packed less than a millimeter apart and take less than half a second to circle the body. So, a 16-slice scanner can cover 8mm to 12mm in one pass or about 2.5 centimetres a second. A 40-slice scanner collects images covering 20mm to 32mm in a single pass and a tightly packed 64-slice device can cover about 40mm at a pass, which takes 0.4 seconds.

At that rate, a 64-slice scanner can gather a high resolution image of a heart, brain or a pair of lungs in about five seconds. A scan of the whole body, (in search of a blood clot, for example, that has become a source of emboli) takes about 30 seconds.

The beating heart

The technology has been particularly exciting for studying the beating heart, providing the first clear non-invasive images of the heart and its major vessels. The scans can be timed to use only images gathered between contractions, so that the heart and its vessels can be seen without the blurring caused by motion.

The scanners are also beginning to have an impact on cancer diagnosis and treatment. Nearly 60% of CT scans at the University of Chicago Hospitals in the United States are done for cancer. The hospital was the first in the US to install Philips’ Brilliance 64-slice CT scanner earlier this year. The speed and precision of these new scanners not only improves the image quality, but also "lets us look at dynamic processes", Michael Vannier, MD, professor of radiology at the University of Chicago said.

"Instead of just monitoring changes in tumour size, we can watch the perfusion of a contrast agent as it moves toward, around and through a tumour," he said. "This can provide an early view of how a patient is responding to therapy. It helps us predict, rather than simply describe responses to treatment."

In fact, according to a University of Chicago Hospitals spokesperson these scanners have already provoked "turf" battles between radiologists and cardiologists who perform diagnostic angiograms – until now the gold standard for assessing the coronary arteries. The best multidetector CT scans can rival angiography for detail and are quicker, more convenient, less expensive and safer than an angiogram, as well as exposing the patient to less radiation.

"We've already switched from catheter-based to CTbased imaging in the brain," said Dianna Bardo, MD, assistant professor of radiology at the University of Chicago. "The heart may come next."

Other promising indications for multi-slice scanners include evaluation of plaque within the carotid arteries (five to eight seconds), searching for pulmonary emboli (five seconds, less than an easy breath hold), coronary artery imaging (10 seconds, including distal segments and multiple arterial branches).

Radiation dose

The website medcompare.com points out that despite the promise of 64-slice CT in non-invasive cardiac diagnostics, some cardiologists have expressed concern in their widespread use. Is the dose of x-ray radiation safe to use on everyone, in other words as a screening test, they ask? Multi-scan CT delivers increased levels of focused radiation compared with single slice CT and although these slightly increased doses are justified for patients with existing or symptomatic disease, they may not be appropriate for everyone, they warn.

Nonetheless, the technology is a major advance and continues to be refined. Prototypes for 128-slice and even 256-slice scanners are under development. Clinical use of multi-slice CT is increasing and the 64- slice cardiac CT heralds a new age of non-invasive cardiac imaging.

Toshiba’s Aquilion 64-slice CT scanner

The Aquilion 64 is built on Toshiba's unique 64-row Quantum detector, volumetric imaging capabilities and advanced software applications.

At the heart of the Aquilion 64 is its superior multi-detector design, that produces high-speed, high resolution imaging with the best low contrast resolution at the lowest dose. The Quantum detector enables the Aquilion CT scanner to acquire 64 simultaneous slices of 0.5 mm with each 400- millisecond gantry revolution. The result is precise isotropic imaging of any region of the body during a breath-hold under 10 seconds.
Toshiba's CT technology offers true isotropic voxels, which greatly enhance most clinical studies, including examinations of the lungs, joints, extremities and CT angiography.

Isotropic data sets also markedly improve the quality of MPR and 3D reconstructions, which aid the radiologist not only in diagnosis, but also in managing the huge amount of information generated by multi-slice scanners.

Toshiba has succeeded in developing isotropic imaging based on the standards of 0.5mm slices for the head and one millimetre slices for the abdomen. Applications for 0.5mm slice scanning are studies of the cerebral circulation, lungs, spine, joints and extremities.

The 64-detector scanners naturally make more efficient use of the x-ray beam, however with the corresponding increase in CT scans from multi-detector CT comes a concern about minimising dose for every examination. Aquilion systems are designed with tubes that reduce off-focal xrays and detectors that provide excellent image quality at low dose.

To further enhance patient safety, Aquilion 64 incorporates several additional features to assure dose effective imaging.

Shaped filters modify the beam profile to automatically reduce dose based on exam type. This is particularly beneficial for paediatric and cardiac patients.

Quantum denoising software lets users balance the trade-off between dose level and image quality. Operators can either lower the dose by as much as 50% and maintain image quality, or keep the standard dose and improve image quality.

Toshiba’s ‘Sure Exposure’ ensures optimum image quality at minimum patient dose, by adjusting the tube current during scanning. Often reducing total dose by up to 40% per patient, it is especially valuable in paediatric examinations to ensure children receive the lowest acceptable dose, every time.

Raster Artifact Suppression Protocol (RASP) reduces streak artifacts from high-absorption areas like the shoulders and pelvis, and minimises the need to increase dose to compensate for absorption.

For more information visit: www.medical.toshiba.com

Siemens’ Somatom Sensation

Siemens Somatom Sensation 64 was first introduced at the Radiological Society of North America (RSNA) 2003. Sensation 64 offers clinicians the peak of clinical performance. Empowered by the Siemens unique Straton tube and z- Sharp Technology, the Somatom Sensation 64 enables the user to routinely achieve unprecedented diagnostic detail with the industry’s highest isotropic resolution of below 0.4mm and fastest rotation time of up to 0.33 seconds. By utilising the most powerful advanced applications, the user can image the smallest pathology and finest anatomical structures in just a few seconds.

The Somatom Sensation also utilises the newly developed Speed4D technology which has changed CT tube design, dose optimisation and workflow management to enable the automation of complex imaging processes while providing consistent, high quality results in a minimum amount of time. Siemens’ ‘CARE Dose4D’ automatically adjusts the tube current in real-time to reduce dose up to 66% while maintaining optimal image quality. ‘WorkStream4D’ directly generates diagnostic images in any desired plane, thus eliminating time consuming, manual reconstruction steps.

Siemens Navigator is designed to give the clinician intelligent, reliable workflow for data acquisition, image reconstruction and routine post-processing at the CT scanner. Built on Siemens’ unique ‘syngo’ platform, the Navigator is intuitive and user friendly. With the integrative WorkStream4D concept, the Navigator provides unmatched speed and efficiency, facilitating simultaneous acquisition and reconstruction at a single workplace. With access to a comprehensive portfolio of syngo clinical applications, the Navigator helps the clinician achieve seamless integration of their diagnostic workflow.

Siemens Medical Solutions says it has the world's largest installed base of 64-slice CT technology in clinical routine worldwide. Two hundred 64-slice CT systems have been installed, 80 of which include the Somatom Sensation Cardiac 64 in hospitals' cardiovascular departments or institutions specialised in the diagnosis and treatment of cardiovascular disease.

The Somatom Sensation Cardiac 64 is Siemens’ latest contribution to CT technology. Siemens says: “With the world's fastest gantry rotation speed of 0.33 seconds, the Somatom Sensation Cardiac 64 routinely achieves a temporal resolution of 83 milliseconds, and thus facilitates scanning of patients even with higher heart rates, virtually freezing the heart's motion. Utilising Siemens' unique ‘z-Sharp’ technology, the scanner delivers optimal image quality with a routine isotropic resolution of below 0.4mm. This unique temporal and isotropic spatial resolution, available in all routine and cardiac modes, allows for optimal evaluation of peripheral segments of the coronary arteries, including plaque evaluation, and improves follow-up assessment of stent patency with high confidence.

“The combination of the fast rotation speed with 64- slice acquisition also enables an electrocardiography (ECG) gated coverage of the entire chest in a short 15- second breath hold. For the first time, this CT performance allows for the evaluation of the most common causes of acute chest pain with a single scan. A routine scan of the coronary arteries only takes about eight seconds.”

For more information visit: www.medical.siemens.com
 

GE’s Lightspeed VCT

The LightSpeed VCT is GE’s latest innovation in CT technology. VCT means "Volume CT".

The hallmark of this noninvasive imaging system is GE’s new ‘V-Res’ detector with its ability to deliver wide anatomical coverage and high resolution, simultaneously.

This unprecedented coverage speed allows clinicians to capture whole organs in a second, the heart in five beats, or go head to toe in under 10 seconds.

In a single rotation, the system creates 64 credit card-thin images, totalling 40mm of anatomical coverage and producing a hi-resolution 3D view of the patient’s anatomy.

“This is clearly the beginning of a new imaging era,” said W Dennis Foley, MD, chief of Digital Imaging at Froedtert Hospital and professor of radiology at the Medical College of Wisconsin, US. “This system provides unprecedented image quality almost instantaneously, which should provide significant impact in cardiovascular medicine and trauma. Though its impact may be most significant in trauma and cardiovascular medicine, the LightSpeed VCT also should improve imaging in neurology, oncology and other fields.”

With breakthroughs in technology, comes the opportunity for new and dynamically enhanced procedures, such as:

5-Beat Cardiac – Heart motion has historically made CT cardiovascular scans challenging and prone to motion artifacts. The LightSpeed VCT will enable physicians to secure extremely high-quality images of coronaries at submillimetre resolution in only five beats of the heart. This capability will potentially make diagnostic evaluation of arterial stenosis faster and less invasive than catheter angiography.

Triple RuleOut – Patients exhibiting acute chest pain in the emergency room may be able to be diagnostically scanned quickly and noninvasively, using the LightSpeed VCT, for evidence of heart attack, pulmonary embolism or aortic dissection, the three most life-threatening causes of chest pain, all in a single scan. A doctor’s ability to identify the cause of acute chest pain and eliminate unnecessary hospital stays and missed diagnoses is invaluable.

Stroke WorkUp – Once a stroke occurs, it is commonly believed that treatment must be delivered within an hour or less to ensure the best outcome for the patient. Current diagnostic imaging procedures are complex. LightSpeed VCT offers the speed and resolution required for rapid examination of blood vessels in the brain (perfusion studies), enabling doctors to make a quick diagnosis of stroke and extent of damage, and may help make this complex procedure easier and more routine.

Specifically, the LightSpeed VCT covers 4cm of patient anatomy per rotation, gathering 64 slices at 0.625mm (about the thickness of a credit card). Gantry rotation speed is less than 375 milliseconds or approximately 2.5 to 3 rotations per second.

It comes complete with GE’s Xtream FX. Xtream FX is the second generation of GE’s Xtream workflow technology, which provides imaging departments the ability to keep pace with the large volume of data generated by MDCT systems. A tool such as Direct Multi-Planar Reformat (DMPR) allows customers to improve interpretation efficiency, and provides views that are more familiar to referring physicians and surgeons. Xtream FX adds more “effects” to GE’s scalable Xtream reconstruction engine, which revolutionized workflow design with increased speed, image quality, and workflow flexibility.

In addition to its capabilities as a stand-alone technology, GE designed the LightSpeed VCT to easily integrate with its positron emission tomography (PET) technology. This fusion will marry the highspeed, high-resolution capabilities of GE’s volumetric CT with the metabolic and physiologic capabilities of its industry leading PET.

For more information visit: www.gehealthcare.com

Philips’ Brilliance 64 CT

Philips introduced the new Brilliance CT 64-channel scanner at RSNA 2004. This new scanner delivers large coverage, thin-slice acquisition capabilities to the full 40mm width of the Brilliance CT detector by increasing the number of simultaneously acquired data acquisition channels to 64.

With the Philips Brilliance 64-channel system, clinicians can easily capture rich visual details, cover a large area of the body, in less time, all with high levels of patient comfort. All Philips Brilliance CT systems are designed to improve the patient experience as well as that of the operator; all aspects of the system are optimised for ease-of-use, low dose and feature new visualisation methods and Philips’ ‘Guided Flow’ concepts supporting diagnostic confidence. The 64- channel configuration also provides advanced pulmonary imaging, multiorgan trauma evaluation and low-dose paediatric applications as well as in the areas of cardiovascular CT and virtual colonoscopy.

Philips says the its Brilliance 64 CT is designed for leading edge and research-oriented institutions that want to conduct the most advanced multislice CT studies. The company says the new scanner will expand clinical boundaries through applications, such as extended coverage brain perfusion, that will position CT as a modality of choice in stroke evaluations. Philips Medical’s ‘DoseWise’ design delivers optimal dose efficiency without compromising image quality.

Following extensive collaboration with their customers Philips developed the Brilliance CT family – 6, 10, 16, 40 and 64 channel. In addition Philips developed two specialty systems: one designed specifically for oncology marking, acquisition and scanning and the other for non-invasive cardiovascular assessment.

Philips’ user environment is called the Brilliance Workspace.
Brilliance Workspace is:

- designed to maximise the ability of advanced CT systems without compromising their usability.

- specifically developed to manage the enormous datasets generated by largevolume CT acquisitions.

- rich in clinical applications that boast time-saving features designed to eliminate the traditional constraints which hamper workflow and quality of care.

For more information visit: www.medical.philips.com