CT and robots join forces in the surgical suite

Gary Boas

Dr. J. Fritz Angle and colleagues at the University of Virginia Health System in Charlottesville already had devoted considerable energy to combining traditional interventional techniques performed under a fluoroscope with CT guidance when they began exploring ways to fuse the techniques.

CT provides useful information when one is delivering intra-arterial chemotherapy to the liver during a procedure called chemoembolization. However, typically the patient must be moved from the procedure suite for CT imaging, a process that disrupts the procedure and that requires the patient to be under anesthesia for still longer.

Using a new system that provides large-volume CT scans via a multiaxis C-arm incorporating robotic technology, surgeons can visualize the whole abdomen during chemoembolization without having to move the patient for CT scanning. Shown here are a CT image using the new system (left), a multiplanar re-format image (center) and an angiogram (right) in a patient with a liver tumor.

The clinicians installed a Siemens Artis zeego system, which enables large-volume CT scans by way of a multiaxis C-arm incorporating robotic technology. As reported in a study released at the Society of Interventional Radiology’s annual meeting, held in March in Washington, the system allowed the interventionists to visualize the whole abdomen during chemoembolization by providing a reliable assessment of lipidol uptake after the procedures. The university is one of the first two institutions in North America to receive the system.

The robotic technology used in the system can help to improve procedures considerably. “We’ve always looked at the possibility of increasing the flexibility of interventional imaging systems,” said Brian Porras of Siemens, “and we ended up looking to evolve beyond traditional C-arm-based technology.” By incorporating advanced robotics, the new system offers largely unrestricted C-arm positioning. Also, the clinician can adjust the position of the imaging isocenter according to the physician’s height — this is especially beneficial given the duration of certain interventional radiology/cardiology procedures and given the generally poor ergonomics of traditional systems, which require the clinician to hunch over the patient.

Flat detector

A key feature of the system is syngo DynaCT, which the company developed and introduced in 2004. This technology, based on CT principles, allows soft-tissue imaging by using the interventional x-ray system and rotating the x-ray tube in tandem with the company’s flat detector technology — a process sometimes referred to as “cone-beam CT.” With flat detector technology, the received energy is converted into light at the detector; this light is then converted into an electric signal, which then is translated into an image. “You get a much better signal-to-noise ratio with flat detectors,” Porras said.

The feature has been available on the company’s Artis family of systems, but the adjustable isocenter of the present system offers unique support for “large-volume syngo DynaCT” by enabling two nonconcentric rotations around the patient.

The cone-beam CT concept is still relatively new, Angle said, “and this machine provides a much larger field of view than the first generation; it is much more encompassing.” The one disadvantage, he noted, is that, as with any cone-beam CT system, it does not offer the contrast resolution that they would like to have. The clinicians are sidestepping this issue for now by choosing applications where relatively high contrast already is present — with inter-arterial injections of contrast, with kidney stones and with any kind of bone lesions, for example.

Angle added that the system provides opportunity for continued growth and development. Software improvements will further enhance the capabilities already available to us, he said.

Contact: Dr. J. Fritz Angle, University of Virginia Health System; e-mail: jfa3h@virginia.edu; Brian Porras, Siemens Medical Solutions; e-mail: brian.porras@siemens.com.