More With Less
By Keith Loria
Vol. 19 No. 9 P. 18
Advanced software reduces dose without sacrificing image quality.
Although the direct health risk of medical diagnostic scanning is not unequivocally clear, it is important for patients as well as health care professionals to mitigate the risks of radiation dose. While most of the concern regarding overexposure and cumulative dose has historically been focused on CT, which generally delivers much higher dose levels to patients than standard X-rays, the issue has raised awareness of a patient's cumulative lifetime dose across all modalities that use ionizing radiation—CT, radiography, and angiography.
Most original equipment manufacturers have a strategy centered on improving the quality and safety of patient care through a commitment to lower radiation across a suite of medical imaging products. The challenge is doing so without sacrificing quality images or impacting care.
Less Dose, Same Quality
An example is Samsung's GC85A premium fully digital X-ray system, which provides the same image quality with one-half the radiation. Deborah Chung, marketing manager of health care at Samsung Electronics America, says Samsung's image postprocessing engine, S-Vue3.02, provides spatially adaptive multiscale processing and advanced denoising technology.
"The new system delivers the same image quality as the predicate device but with half the radiation exposure," Chung says. "The key is Samsung's cutting-edge denoising processing, adopted for the new engine, which reduces noise from the noisy low-dose data while preserving the details of the object being imaged."
The dose reduction in digital chest radiography is based on limited phantom and clinical study results for Samsung's GC85A and GM85 systems. Hetal Patel, MD, a radiologist at Alamance Hospital in Burlington, North Carolina, says the low-dose image quality on the GC85A equipment is excellent.
"The retro cardiac region is well visualized with excellent penetration, and the rest of the anatomical structures are clearly demarcated," Patel says. "Also, bony structures were well delineated. Low-dose imaging has a similar or better image quality than regular-dose images."
EOS Imaging develops and markets the EOS system, an X-ray-based modality for musculoskeletal imaging that captures simultaneous anteroposterior/lateral (AP/LAT) full-body images of patients in functional positions at significantly reduced radiation doses.
"The value of the EOS system is multiple: value in patient safety through a dose reduction that can be two-fold to 10-fold, compared with DR and CT; value in efficiency through a much faster exam—up to 75% savings in exam time; and value from a better-informed treatment thanks to our unique weight-bearing 3D data," says Marie Meynadier, CEO of EOS imaging.
As a result, an EOS exam provides high-quality, full-body, low-dose AP/LAT radiographs, a 3D model of the skeleton, and a comprehensive report of automatically calculated clinical parameters in 2D and 3D in less exam time.
"Reducing health care-related radiation exposure is a metaphorical cornerstone in medical ethics and the standards exhibited in the Hippocratic Oath," says Christopher J. Smith, CNMT, RT(N), administrative director of radiology and imaging at the Hospital for Special Surgery (HSS) in New York. "While incidental exposure from X-rays has minimal to no patient risk, there are patient populations, such as adolescent idiopathic scoliosis patients, that may receive serial X-rays for many years."
Moreover, the aggregation of these exposures is yet to be fully evaluated and can be anxiety inducing. Smith utilizes the EOS imaging system, which he notes offers significant dose reduction for the imaging life of the patient.
"At HSS, we see dose reductions equal to approximately 50% of comparable digital X-rays," Smith says. "EOS also offers a microdose feature that can further reduce patient exposure to near-background levels, which HSS will be exploring to offer for some patient cohorts."
Two key factors that allow EOS to provide a reduced dose and clinical image quality are an innovative gas detector and a collimated X-ray beam to reduce scatter and unnecessary X-rays. The EOS detector has extremely high sensitivity and a very high gain, which is automatically adjusted for each exposure. This preserves contrast from the denser parts of the anatomy, such as bones, to the less dense parts, such as soft tissues and lungs.
"The outcome is an X-ray image with good resolution, sharpness, and 65,000 gray values," Smith says. "This means that the X-ray images can be windowed similar to the way radiologists do for specific body parts in CT. Next, the X-ray beam is collimated just after the X-ray tube and passes through a shielded horizontal slot that is 500 microns high. The resultant fan-shaped X-ray beam limits the volume of the body exposed at each moment and, thus, drastically limits the total number of aberrant X-rays, the 'scatter,' exiting the patient and entering the gas detector, where it would degrade the image sharpness."
Steven Eisner, senior product manager for Konica Minolta Healthcare Americas, Inc, says the company's AeroDR family of digital flat panel detectors—AeroDR HD, AeroDR XE, and AeroDR LT—utilize a combination of high detective quantum efficiency, high spatial resolution, and REALISM image processing software to contribute to improved dose efficiency.
"REALISM is our next-generation advanced image processing software that provides superior visualization of structures within soft tissue and bone within the same image," Eisner says. "It delivers a new level of clarity and detail in X-ray imaging that improves the sharpness of fine details, enhances visibility of hard-to-penetrate structures, and delivers excellent visibility of high-contrast images. This translates to the ability to generate more information with fewer exposures per exam as well as avoid the need to retake images due to poor image quality."
At Cuero Regional Hospital in Cuero, Texas, Tyler Lemke, director of radiology, has been using REALISM and AeroDR.
"In the wrist, where there are many small bones, I immediately noticed the fine details and sharper images allowing me to see the fine details of each bone," Lemke says. "The images were so crisp the bones just popped [off the image] and the edges and trabeculae of every bone were very clear."
Lemke also tracks repeat exposures. He had previously noticed that technologists were performing repeat exposures because they were not optimizing exposure levels. In the first month after installing REALISM and AeroDR, Lemke worked with this staff to ensure a higher attention to detail with the new DR system; as a result, repeat exposures have dropped by 20%.
"Department managers are concerned with dose, and AeroRemote Insights provides the analytics, via interactive dashboards, they need to manage their AeroDR assets and deliver a better experience for patients," Eisner says. "Over the last decade, with the increase in system connectivity and the more recent emergence of [the Internet of Things], we've tapped into our experience and expertise to be the first to deliver analytics in DR to our customers."
A new preclinical scanner from 4Dx Limited, a Melbourne, Australia-based medical technology company, focuses on lung disease and reductions in radiation dose. Andreas Fouras, PhD, a mechanical engineer, is the inventor of the tech. He was working at a university doing wind tunnel imaging and developing algorithms to measure and quantify movement when he thought this capability could be used to measure motion in the lungs.
"The first layer is we measure in fine detail how the lungs move as the subject breathes, and then, once we have that information as to how the lung tissue is moving, it's actually a relatively simple step to then calculate what the air flow is that creates that lung tissue motion," he says. "So, we can create high-resolution maps of airflow, of ventilation in the lungs. We think of this as a brand-new modality, but we just use older X-ray equipment so we can do low-dose X-rays and apply the algorithm and generate this new, rich data."
The whole procedure has a dose cost of about 0.2 milligrays—about two chest X-rays worth of dose—but it provides highly detailed data at no capital cost and no upfront cost to a site, a doctor, or a radiologist.
"We create a 3D image of this lung tissue motion," Fouras says. "The old sort of CT way works by taking hundreds of images around the outside of a patient to reconstruct the 3D CT image. We're actually able to do that with as few as three views. The closest sort of competing technology in this space would be a 40-slice CT, which is going to be substantially more dose than two chest films."
Waseem Bhatti, MD, medical director of imaging at Summit Medical Group MD Anderson Cancer Center in Florham Park, New Jersey, says by utilizing a combination of clinical decision tools, hardware, and software technology innovations, along with purposeful scanning, the industry can optimize medical imaging for patients.
"Reducing dose for our patients begins before the scan. Software and the 'cloud' are increasingly playing a role in limiting the number of unnecessary scans and repeated scans within a short time interval," Bhatti says. "From what we know about Moore's law—the observation that the number of transistors in a computer chip double about every two years—we have seen dramatic improvements in CT scanners."
In the early 2000s, most CT scanners used a single slice to scan. At Summit Medical Group MD Anderson Cancer Center, most of its current scanners use at least 160 slices.
"Customization of radiation dose using automated exposure control software on our CT scanners helps decrease unnecessary dose," Bhatti says. "The patient's size and shape is measured and calculated for the specified scan protocol, and the dose delivered through the 360 degrees of the scan may be modulated depending on soft tissue thickness at a given slice level."
A large part of the dose depends on the clinical question posed by the referring physician. For example, a contrast-enhanced pancreatic protocol CT scan will require a higher dose than a noncontrast scan for detecting kidney stones.
"Unfortunately, the more we decrease the dose, the more noise or blurriness we encounter," Bhatti says. "To deal with noise, postscan reconstruction software is used to produce diagnostic quality images by improving spatial resolution."
The center's Canon Aquilion CT scanners select the dose based on patient size, exposure settings, and type of scan being performed. Iterative reconstruction software on these scanners optimizes the images.
"When a patient undergoes a CT scan, they deserve to have the highest-quality scan using the lowest dose possible. The ALARA principle of responsible dose management guides our approach," Bhatti says. "We also fully participate in the Image Gently campaign to reduce pediatric CT dose. Our equipment helps us adhere to these principles by giving us the tools necessary to limit dose while producing high-quality images."
— Keith Loria is a freelance writer based in Oakton, Virginia.