Published in UAB Insight, Winter 2008

Getting a Better Picture: Volumetric Scans Hold a Thousand Details

Diagnostic modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) have been used for years to capture three-dimensional (3-D) images of the body. A new 3-D ultrasound modality — volumetric imaging — now offers many advantages of CT and MRI without the high cost, radiation, or bulky equipment. UAB’s Department of Radiology operates three volumetric imaging scanners, which radiologists use in abdominal and vascular imaging and other clinical applications.

CT and MRI scans acquire a series of parallel slices from the anatomic area of interest that are reconstructed into a volume image that radiologists can manipulate for diagnostic purposes. According to UAB’s Chief of Body Imaging, Franklin N. Tessler, MD, CM, radiologists and sonographers have mentally created 3-D images from 2-D ultrasounds for years. “Like CT and MRI, 3-D ultrasound generates volumetric scans, not just planar representations,” he says.

In traditional ultrasound exams, a sonographer collects a series of static images and real-time video clips to evaluate regions of interest. This method does not allow generation of 3-D images or postanalytic examination of anatomic structures in planes not directly imaged during ultrasound scanning.

“3-D ultrasound produces images in any plane needed for additional analysis,” he says, “and with expected advances in ultrasound transducer technology, reconstructed images will be as detailed as those obtained by direct scanning.”

With the body’s fluids providing the contrast medium, radiologists have used 3-D sonography to acquire previously unseen images of the urinary bladder.

“Radiologists can observe the inner topography of the normal bladder, and for the first time, see bladder tumors in 3-D, and evaluate their relationship to adjacent anatomic structures,” he says. “This gives physicians new perspective and information to guide treatment.”

In vascular imaging, blood provides the contrast needed to observe vessels from multiple perspectives, displaying relationships and details that are difficult or impossible to appreciate using traditional techniques.

The diagnostic capabilities of this new technology reach beyond the familiar 3-D ultrasound pictures displayed for parents of the developing fetus in the womb. “Development of future medical applications is very much a work in progress and multiple clinical uses are being investigated,” Tessler says. “Nonobstetric gynecological applications, for example, permit observation of uterine malformations and endometrial anatomy not previously seen during pelvic sonography.” Investigators are assessing 3-D uterine sonography for volumetric evaluation of fibroids and other pelvic masses (J Women’s Imaging. 2003;5[2]:52-59).

3-D ultrasound also may change workflow by letting sonographers rapidly acquire volumes that radiologists can analyze after patients leave. “Although this approach probably will not work in all areas, it may boost efficiency and help radiologists cope with an ever-increasing workload,” he says. Radiologists are investigating streamlined procedures at UAB and other centers.

As the technology matures, clinicians will suggest additional avenues of exploration for 3-D sonography, says Tessler, who compares it to a new hammer and notes “everything on the horizon looks like a potential nail.”

For more information:
Dr. Franklin Tessler
1.800.UAB.MIST
mist@uabmc.edu