Feature | June 22, 2006

Slicing its Way to Rapid CT Expansion

What are some of the noteworthy growth areas for computed tomography (CT) applications today and why are they so popular? The greatest CT growth areas are currently in cardiovascular imaging and functional studies. The ongoing evolution of cardiac CT angiography has increased the ability to visualize noncalcified lesions.

Toshiba’s Aquilion 32- and 64-slice CT scanners have the industry’s best low contrast resolution, which is a prerequisite for accurate lesion visualization. This combined with advanced software analysis, such as Toshiba’s SUREPlaque software and cardiac functional analysis, helps clinicians in determining the best treatment plan.

The emergence of multislice CT effectively muscled aside the single-slice scanner, which was the standard back in the 1990s. In this new era of four-, eight-, 16-, 32-, 64- and dual-source CT, where can, should and do single-slice models still function and why?

We have seen a major market shift to the benefits of multislice technology in the U.S., Europe and Japan. There is still a limited market for single-slice scanners in some parts of the world, but all systems being ordered in the U.S. are currently four-slice CT or higher.

In your opinion, for which functional uses does four-, eight-, 16-, 32-, 64- and dual-source CT each make the most sense and why?

Due to the unique design of the Aquilion series, we can ensure that the image quality from the four-, eight-, 16-, 32- and 64-slice scanners is the same. This has been achieved by ensuring that all systems can acquire our thinnest slice width at 0.5mm while achieving the industry’s best low contrast resolution, 0.35mm isotropic spatial resolution at the lowest dose. Given this, the functional use of the various systems is primarily determined by thin slice coverage, clinical need and throughput.

Typically, a four-slice scanner is used for routine applications as well as CT-angiography of the aorta, renal, carotids and pulmonary arteries. Four-slice CT systems also are routinely used for coronary calcium score exams. They also are usually located as a backup system for either a 16-slice CT or higher main scanner in hospitals or imaging centers that have more than one CT.

The eight- and 16-slice scanners are capable of the same clinical work as mentioned earlier but have the additional benefit of the enhanced coverage in either 1mm or 0.5mm slices for peripheral run-offs. Typically there is some increase in the ability to scan neurology exams with thinner slices also. The 32- and 64-slice systems are primarily being used for all the benefits of the 16-slice system with the additional capability of performing routine coronary CTA and cardiac functional studies for the imaging of noncalcified plaque.

Because Toshiba has the ability to deliver the same image quality on the entire Aquilion series, we typically look at the clinical need for a CT system to help determine which system is best for the customer. For example, if a customer is able to utilize a 16-slice system for routine work in preference to a high-end 64-slice CT, they save the additional expense and are able to apply those resources to other imaging modalities that may be required such as ultrasound or X-ray.

Toshiba’s future vision of CT is to perform routine scans at lower doses than can be achieved today. To achieve this vision it is essential that we build CT systems that have detectors wide enough to provide the ability to image entire organs as a dynamic scan in a single rotation.

For the last two years at RSNA’s annual conference, Toshiba wowed the crowd with its works-in-progress 256-slice CT demonstrations.

Besides the buzz it generates, why is it needed? What are the detection and diagnostic benefits of 256-slice CT, if any? Where (in terms of applications, as well as locations) do such high-end models make the most sense in daily practice? Why would a freestanding outpatient care facility invest in one?

It is essential that we continue to develop technologies that reduce the dose for medical diagnostic procedures. We have seen tremendous improvements in the last 10 years in the ability to modulate the tube current in CT, which has benefited patients tremendously, particularly in pediatric settings. However, the greatest advancement can still be made by removing the requirement for helical scanning.

The market introduction of a wide area detector will provide major reductions in the X-ray dose required for coronary CTA and both cardiac and other perfusion studies. This major clinical benefit is also supported by the benefit that will come in enhanced image quality from the 256-slice system. The ability to perform routine coronary CTA exams in the 2-3mSv range, as opposed to the current 10-12mSv range, will be the major drive for adoption of this technology.

How do you differentiate the benefits between dual-source CT and the 256-slice technology anticipated in 2007 or 2008? Dual-source technology has the promise to produce faster temporal resolution at lower heart rates. The current implementation is a relatively expensive solution when compared to advanced adaptive multisegment algorithms being used by other vendors. We believe the greatest limitation of this technology is the lack of Z-Axis coverage and hence the requirement that a helical exam is used to scan the patient. This limitation may hinder the ability of this system to reduce the dose to the levels that we are trying to achieve with the next generation of CT at Toshiba.

The current papers published on the 256-slice scanners from Toshiba support the vision to perform coronary exams in a single rotation at low dose rates. When this is achieved it also becomes viable to perform advanced perfusion studies at much lower dose rates than being used in research today. Toshiba’s 256-detector CT scanner is a quantum leap forward from 64-slice CT for the delivery of low-dose, high-resolution coronary exams in the range of previous electron beam technology.

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