Dual energy ct
From Human Oncology
DHO Looks to Dual-Energy CT to Improve Tumor Imaging
Precision radiation therapy depends on high-quality imaging; however, conventional CT cannot always clearly show the edges of a tumor. Last year, the Department of Human Oncology at the University of Wisconsin School of Medicine and Public Health invested in a new dual-energy CT scanner to improve imaging and, ultimately, outcomes for patients with cancer.
Conventional CT uses a single spectrum X-ray for each scan. Each X-ray spectrum has its advantages and disadvantages. Low-energy scans often provide greater contrast, which is good for distinguishing tumor from healthy tissue, but these do not penetrate the body as well as high-energy X-rays. This makes it difficult to obtain a single low-energy scan with adequate image quality. In addition, the optimal X-ray energy may vary from patient-to-patient and among disease sites.
The DHO’s Siemens SOMATOM Definition Edge CT Scanner uses two filter packs that separate a single X-ray source into low- and high-energy portions delivered in a single scan. This provides the benefit of multi-spectra imaging without exposing patients to any more radiation than they would receive from a conventional CT scan.
“With the two images acquired through this single scan, we can reconstruct a variety of images of a patient for the doctors, depending on what anatomical region they would like enhanced,” says Dr. Jessica Miller, DHO assistant professor.
The low- and high-energy images can be looked at separately, combined into a single image to reconstruct what a single-energy CT would have captured or viewed at any energy level between 40 keV and 190 keV.
Miller is leading a project to study the use of dual-energy CT in the liver and pancreas, two disease sites that are particularly difficult to image. With $40,000 in funding from Siemens, Miller, Dr. John Bayouth, DHO professor, Dr. Michael Bassetti, DHO assistant professor, and Dr. Jessie Huang-Vredevoogd, DHO physics resident, will compare physicians’ contouring of tumors of the liver and pancreas using dual-energy vs. non-dual-energy scans.
The study will compare contouring of liver tumors using dual-energy CT images and single-energy CT images with MRIs taken before treatment to determine if any benefit is gained by using dual-energy CT.
Because patients with cancer of the pancreas don’t always have MRIs done, several physicians will contour these tumors using dual-energy scans and non-dual-energy scans, which will then be compared to determine the degree of variation. More variation would indicate less clearly defined tumors in the images.
Miller expects the study to show that the dual-energy CT scans enable physicians to better define and contour tumors than with conventional CT scans.
“Dual-energy is used extensively in radiology departments, but its use in radiation oncology has been underexplored,” Miller says. “We’re very excited about this. We’re the first radiation oncology department in the world to use this equipment. We’ve invested a lot of money, time and effort into this CT scanner because we see imaging as an area where we can really benefit cancer patients.”
Application of this new imaging system extends beyond the liver and pancreas. Miller is also working with Dr. Zac Labby, DHO assistant professor, on using dual-energy imaging for stereotactic radiosurgery, a single high dose of radiation to treat small primary or metastatic brain tumors.
“If we can show there is improvement statistically in these treatment sites, then I think the applications for dual-energy CT in radiation therapy will be great,” Miller says.