Since the first commercial spectral computed tomography (CT) scanners made their debut more than 20 years ago, their many benefits have become widely recognized, making a compelling case for adding them to a well-equipped imaging center. As with any significant acquisition, however, it pays for facilities to perform a cost-benefit analysis to ensure such an investment makes sense, from both financial and clinical perspectives.
Among the most beneficial components of spectral CT scanners over conventional CT scanners is the availability of an iodine decomposition map, said Aran Toshav, MD, adjunct clinical associate professor of radiology at Louisiana State University in New Orleans.
“The most important thing is the iodine decomposition map because it tells me where iodine is displayed using the two energy points,” Dr. Toshav explained, citing the example of a patient with renal cancer being treated with an inhibitor. Whereas a spectral CT iodine decomposition map will reveal the lack of enhancement in portions of the renal mass, conventional CT images will not.
“There’s some iodine still going to this mass, so there's still parts of this tumor that are viable,” he said. “But I'm able to show that there is treatment response, which is something I wouldn't be able to do on a conventional CT,” said Dr. Toshav.
Spectral CT also enables radiologists to choose different energy points for viewing images. At a low keV of 45, the conspicuity of iodine within images can be increased, helping them to easily identify liver lesions and view differential enhancement of the pancreas.
Conversely, a higher energy point allows for reductions in noise and artifacts. In addition, spectral CT’s Z-effective – the atomic energy display – color codes lesions for ready visualization.
Valuable as these benefits may be to radiologists, spectral CT also comes with some important costs that must be weighed against its usefulness for any given imaging center. First, dual-energy spectral CT can require more time to protocol patients versus single-energy CT. There’s also more time associated with reviewing dual-energy imaging data, as there are more data sets with spectral CT than there are with conventional CT.
Patient selection can also be challenging. For example, most spectral CT systems can’t image patients weighing more than 270 pounds or with a BMI of 30 or higher, due to the amount of energy that must be delivered with the lower energy source. Historically, a higher radiation burden is required to make low-dose sequence possible on larger patients. Dr. Toshav said these challenges can be largely mitigated with Philips’ new Spectral CT 7500, which provides spectral information for every patient without compromising image quality, dose, or workflow. The fast, always-on spectral detector delivers rich results in a single scan and requires no special protocols.
“The synthetic monoenergetic images created from the low- and high-energy detector-based imaging are actually better than the conventional imaging. There’s less noise, partly because of how Philips does dual energy. There's anti-correlating noise suppression, and because there's perfect co-registration with the detector-based imaging, Philips can lower the noise in these images,” said Dr. Toshav.
The single-source, dual-detector has expanded accessibility of spectral CT to obese patient populations previously considered inappropriate for dual-energy scanners. The dual-energy monoenergetic images provide excellent contrast and signal-to-noise ratio in these patients, and the scanners’ iodine maps are of diagnostic quality.
“We saw all of this without a dose penalty on the Spectral CT 7500. This is one of the ‘costs’ that was automatically reduced because dual-energy imaging was appropriate for the entire patient population, that the dual energy imaging is always there,” he said.
Spectral detector CT helps salvage sub-optimal injection scans without requiring patients to be re-scanned, which shortens time to diagnosis. The Spectral CT 7500 was designed for first-time-right diagnosis; in a recent analysis, the technology reduced time to diagnosis by 34%, repeat scans by 25%, and follow-up scans by 30%.1
To fully understand the impact of these issues, Dr. Toshav led a cost-benefit analysis through a single-center, retrospective review of patients receiving contrasted abdominal and pelvic CT imaging. They started with follow-up recommendations in three categories of exams: single-energy CT, dual-energy CT without the iodine map, and dual-energy CT with the iodine map. They found that follow-up imaging was significantly lower after studies that used an iodine map. Combined, follow-up MRI and PET/CT exams dropped from 13% to 9.6%.
“We found that incomplete diagnosis was significantly higher in the conventional CT reports than in the iodine-mapped CT, dual-energy images,” he said. Based on these findings, Dr. Toshav believes facilities using the Medicare reimbursement schedule for physician fees could realize significant cost savings with iodine-mapped, dual-energy CT versus conventional CT. “We felt there was a strong potential for cost savings and multiple results suggesting improved radiologists’ diagnostic certainty with the dual-energy data sets,” concluded Dr. Toshav.
1Analysis by CARTI Cancer Center in Little Rock Arkansas and University Hospitals of Cleveland. Results from case studies are not predictive of results in other cases, which may vary.Back To Top
Spectral CT: It Pays to Weigh the Costs and Benefits. Appl Radiol.
McKenna Bryant is a freelance healthcare writer based in Nashotah, WI.