A Gem of an Idea

A CT scanner that tells you more

In addition to enhancing a ring or a king’s crown – and serving as this month’s birthstone – the garnet acts as the basis for Gemstone Spectral Imaging, one of Waukesha, Wis.-based GE Healthcare’s latest innovations in improving CT imaging for patients and physicians. Bob Beckett, global product manager of CT for GE Healthcare, explains how this and other techniques continue to strengthen the potentials of CT.


Q   rt image: We had a chance to see the Discovery CT750 HD at RSNA earlier this month. Tell me a little about the product, specifically its advantages to technologists, radiologists, and patients.
 
A   Bob Beckett: Our messaging for the Discovery CT750 HD is, “See more, know more, less dose.” If you break that down, “see more” means better image quality, which reflects value to the radiologist reading the exam. It also offers the patients a more accurate diagnosis. If I were a patient, I’d want the clearest image in front of the radiologist’s eyes so that my exam is read with confidence and accuracy. Clearly, there is a benefit for both the radiologist and the patient.

As far as time and workflow, the technologist should benefit by avoiding repeats. In addition, if a clinician can read images and cases with clarity, the time spent equivocating is lessened. Saving time to image and diagnose saves money and thus improves productivity of the department.

The “know more” is offered by two new innovative functionalities available on the scanner. One is the Gemstone Spectral Imaging (GSI), which is our dual energy technology, and the other is Volume Helical Shuttle. These two features offer more functional information to the radiologist to help problem solve. If they see a small lesion, for example, and they’re not sure if it’s enhancing or non-enhancing, this additional information would help them problem solve what it might be – otherwise, it may be called indeterminate, and thus lead to further testing.

The last component is lower dose. The CT750 HD scanner offers an innovative algorithm, Adaptive Statistical Iterative Reconstruction (ASiR). This algorithm, coupled with the machine, allows the system to deliver 50 percent less dose versus non-ASiR protocols. Reducing dose is all about the patient. ASiR helps with patient safety, which leads to better health care.
 
Q   image: The slogan is “Clarity without Compromise.” What does that mean?
 
A   Beckett: Again, improved clarity allows clinicians to see more information, and with the Discovery CT750 HD this benefit is offered without compromise. Clarity is about seeing anatomy, pathology, and findings with better visualization. If you think about what interferes with the clarity today, or in our previous CT system, it’s things like low-contrast resolution, artifacts, noise, and
resolution in general. So the scanner was designed to improve these four components of image quality to help with the diagnoses and to make problem solving easier.

Q   image: What are the benefits of Gemstone Spectral Imaging?
 
A   Beckett: We’re very excited about what Gemstone Spectral Imaging (GSI) brings to CT imaging. The major value of GSI is the incremental information it offers to help problem solve
pathological findings. There are five key clinical examples to help make this point.

• When a lesion is revealed, clinicians want to know if it’s enhancing or non-enhancing with IV contrast, and that answer will help dictate the treatment pathway for the patient. GSI has the ability to separate iodine from water, which can help characterize these small lesions.
• GSI can help reduce metal artifacts. If patients have any metal within their body – for example, teeth fillings or prosthetic devices – the metal will interfere with X-rays and cause a lot of scatter artifact in the image. GSI minimizes these artifacts so one can see the anatomy adjacent to the metal that they otherwise would not be able to appreciate.
• Thirdly, GSI has the ability to create virtual non-contrast-like images from a with-IV contrast exam. If IV contrast was used, and a clinician needs to separate the iodine from the
• anatomy for an interpretation reason, GSI has this capability.
• A fourth value is with beam-hardening artifact suppression. When performing CT neuroimaging, it’s common to see beam-hardening artifacts within the base of the brain caused by the bone. This common artifact interferes with seeing critical anatomy. GSI can minimize these artifacts to bring clarity to doctors’ read.
• And, just as important is the ability to advance CT angiography by separating iodine from calcium within a vessel. A lot of times, the calcium will cause blooming artifacts because of its dense components, making it appear larger than it actually is. Therefore, if you could separate the calcium from the vessel, one could see the true extent of the lumen patency, or the percentage of the opening of the vessel.

All of this is done uniquely with our Gemstone Spectral Imaging. Of course, there are other applications that will benefit as well, but these give you a good appreciation for how incremental information can favorably improve CT imaging.
 
Q   image: The gemstone itself isn’t something you can find in jewelry, but it was developed specifically for imaging, right?
 
A   Beckett: Right. Gemstone is referring to a garnet gemstone. What’s unique about a garnet is that the molecular structure is very advantageous for light properties – amplification of light, light reflectivity, light efficiency. The garnet is probably the best molecular structure to enhance these properties. The GE gemstone material is made from rare earth elements and a recipe that’s patented and proprietary, but the molecular structure of our gemstone detector is very similar to the garnet gemstone.
 
Q   image: Dose reduction is always on people’s minds. How does ASiR technology work to allow for lower doses?
 
A   Beckett: ASiR enables a reduction in image noise without compromising image quality such that we can lower dose to a patient by up to 50 percent. ASiR is a retro-recon algorithm. In other words, we apply the mathematics to the raw data, and then we make an image. Mathematically, ASiR uses a matrix algebra approach whereby the image components called pixels are measured, compared, and adjusted through the recon process, making a more accurate representation of the object being imaged.

Q   image: The trend at RSNA seemed to be lower-dose CT scanners that move patients through quickly and still get superior image quality. What comes next for CT?
 
A   Beckett: As the product manager of the Discovery CT750 HD, I’m proud to see other CT vendors following our leadership with lowering dose and focusing on advanced reconstruction algorithms like ASiR. We launched ASiR three years ago, and now I’m seeing other vendors following our innovations. The direction we’re taking is all about improving image quality and lowering dose and adding information to help doctors problem solve, leading to better diagnosis for patients as well as better patient care. We’re going to continue down that path, prioritizing these three areas.

There’s a lot more we can still do to improve image quality, evolving hardware is just one approach. We can also further advance reconstruction algorithms. Model Based Iterative Reconstruction (MBIR) is an exciting, very powerful algorithm we are currently working on that will extend the capability of ASiR, which will bring further dose reduction to the scanner. It also offers an image quality improvement, specifically to spatial resolution. It’s a very exciting time for CT imaging.

– Stephanie Twining