|This carotid CTA image was acquired on Siemens Medical’s Somatom Sensation 64 with z-Sharp technology. The resolution of less than 0.4 mm allows delineation of severe stenosis caused by plaque in the artery.|
After the breakneck pace of advances in multi-slice CT, development has paused to take a breath. But just one?new advances lie on the horizon, most aiming to solve the same clinical and technical challenges. But the solution might not simply be more slices. Some advocate more coverage; others are focused on refining today’s workflow.
“Ultimately, it will depend on which technologies will solve problems. There could be multiple solutions that work,” says Brian Duchinsky, general manager of the CT business for GE Healthcare (Waukesha, Wis). “It’s murky whether this is the end of the slice wars.”
Do We Need More Slices?
Looking at a future that includes functional imaging, Jill Blackburn, RT(R)(CT), a CT technologist at St Joseph’s Hospital and Medical Center (Phoenix), believes that more than 64 slices will bring improvements that will help diagnose neurological disorders.
CT: Comparing Technologies
The industry might be looking ahead to the next big thing in CT, but many institutions have not yet upgraded to 64 slices. From single-slice to 64-slice, CT scanners are available to fit every need and budget.For a quick comparison chart to help sort out all of your options, visit: www.medicalimagingmag.com/CTchart (PDF)
Vijay M. Rao, MD, professor of radiology and department chair at Thomas Jefferson University Hospital (TJU of Philadelphia), agrees that improvements are needed; however, she says they might not necessarily come from more detectors. Rao cites the need to optimize images of the heart as a primary driver for development. “The heart is tricky because of its motion, so we need optimal temporal and spatial resolutions,” she says. “And we also want to highlight soft plaque.”
Duchinsky adds, “In particular, coronary artery imaging and plaque characterization are a big focus, but it’s premature to say how much past 64 slices is needed since that technology is still new to the market.”
|This image was acquired using Siemens Medical’s Somatom Definition dual-source CT system. A patient known with chronic obstructive pulmonary disease and contraindication for beta blockers was scanned to diagnose the reason for a sudden onset of acute atypical chest pain. The patient’s shortness of breath made a scan time below 10 seconds necessary, and a temporal resolution of constant 83 milliseconds allowed motion-free imaging of a varying heart rate from 85 to 93 beats per minute.|
He also suggests that other solutions might incorporate dual-energy schemes or bring improvements in areas other than the temporal and spatial. “We want to get larger coverage so that a perfusion study can be done on a whole organ,” Duchinsky says.
Siemens Medical Solutions (Malvern, Pa) recently launched the Somatom Definition, which uses two X-ray sources and two detectors simultaneously. The result is double temporal resolution, speed, and power?with less dose.
Philips Medical Systems (Andover, Mass) has two similar innovations in the works. The Simultaneous Multi-Energy detector, currently undergoing clinical trials in Jerusalem, is designed with layers to detect both low-energy and high-energy X-rays. The simultaneous imaging is expected to improve tissue characterization?for instance, soft versus hard plaque?in less time, with less exposure.
The company’s Nano-Panel detectors are based on smaller-sized tiles that are better able to curve and allow each chip to point directly at the X-ray tube. Data is better reconstructed without artifacts, and greater coverage is permitted. More coverage means that the heart or head can be imaged in a single rotation. “We no longer see a slice barrier driven by technology,” says John Steidley, VP of marketing for CT at Philips Medical.
With this barrier removed, the company is working on a higher-slice version of the Nano-Panel detectors. Steidley shares that the 256-slice CT provides 16 cm of coverage. “You can image the entire head,” he says.
Toshiba America Medical Systems (TAMS of Tustin, Calif) has been pursuing more slices for some time and expects to bring its 256-slice CT to market within 2 to 3 years, according to Joe Cooper, senior manager for radiology at TAMS. Challenges to surmount have included issues with the cone beam itself and data management, among others.
“With the current 64-slice scanner, there is 32-millimeter volume coverage in one rotation,” Cooper says. “With 256 slices, there is 120-millimeter volume coverage, which is a challenge.”
Improvements to the cone beam algorithm contributed to the solution. The scanner is able to acquire the heart in one rotation and, for some procedures, with less radiation than 64-slice CT. Cooper adds, “Our engineers have designed the new technology not just for more slices but also with a focus on bringing significant clinical benefit to patients.”
Keeping It Reasonable
|This congenital aneurism was found with a scan of GE Healthcare’s LightSpeed VCT.|
As companies surmount the technological challenges in the way of better imaging, cost becomes more of an issue. “Assuming reimbursements will continue to decrease, we don’t want to increase costs significantly,” Duchinsky says. “We need to find the right combination of technologies so that we see a substantial improvement in clinical efficacy without an outrageous cost.”
Case in point: Philips Medical’s work developing the 256-slice Nano-Panel technology is restricted by economic concerns. “We could offer a 256-detector panel today, but it would cost $5 million. That’s not really affordable,” Steidley says. “But over time, we will solve the problems with lower-cost technology, making it more affordable and decreasing the cost of healthcare in the process.”
The standard pace of the development for CT technology typically has been a quadrupling of detectors every 2 to 3 years. The next jump is expected to follow suit.
Taming the Data Beast
|CT enables brain-perfusion studies both with and without color. This image was captured with Philips Medical’s Brilliance CT scanner.|
It’s not news that the industry needs to handle the CT’s data overload?before the equipment becomes capable of acquiring even more. Too much information is a primary challenge cited by many in the industry, and it impacts both postprocessing and storage.
“If you ask radiologists what will make their lives better, without leading them, you find that it’s not about slices but image overload, productivity, and workflow,” Duchinsky says. “Radiologists are being asked to read more.”
TJU’s Rao concurs, adding, “It’s impossible to look at 4,000 images, which one could potentially acquire. We need efficient postprocessing and trained technologists to extract answers, because now it’s very time-intensive for physicians. It can take up to 45 minutes to complete the postprocessing.”
Rao would like to see more efficient software, and companies would like to give it to her. TAMS’ Cooper notes that the company has worked with partner Vital Images Inc (Minnetonka, Minn) to provide an automated software solution that interprets volumes of data, rather than slices, for easier and faster postprocessing.
And according to Duchinsky, GE Healthcare’s vision is to advance the technology so that the moment the X-ray or scanner is turned off, a report is ready to be read anytime, anywhere, within 10 minutes. “The end result is not a stack of slices or films, but postprocessed data,” he says. “This should not require highly paid physician assistants or modelers. The system automatically takes over and drives the output.”
Yet even with an easier postprocessing system, storage is still an issue. How and where do institutions store the vast amounts of data generated by these exams while remaining compliant with HIPAA?
“The only way to function with this volume is a dedicated PACS solution,” suggests St Joseph’s Blackburn. Indeed, many institutions rely on a PACS; in fact, studies have shown US market penetration at 80% or more for larger hospitals.
Thomas Jefferson University Hospital, a 925-bed acute care institution, currently uses a first-generation PACS to manage its data. “But the first-generation can’t handle it all. We need to replace it,” Rao says.
Philips Medical’s Steidley notes that most early PACS solutions have this problem. “No one originally envisioned this amount of data,” he says. “It has outpaced the infrastructure, and systems need to upgrade.”
Some institutions have more data than can be stored on their PACS, which means that other solutions must be sought and kept in compliance with HIPAA. Additional storage hardware might be needed, whether on-site or off-site. St Joseph’s, for instance, uses a jukebox for indefinite storage.
Philips Medical offers a solution that stores images on a fee-per-scan basis, intended to eliminate the economic burden of maintaining capacity, Steidley says. Capacity is key, because the data will continue to grow as the use of CT expands into more applications. Its use has already skyrocketed.
|When it comes to cardiac imaging, CT is making huge strides. This image of the heart (top) was produced with Philips Medical’s Comprehensive Cardiac Analysis system.
With 64-slice CT, clinicians are provided with multi-phasic acquisitions to assess the blood supply to these areas that have helped diagnosis and stage early hepatic, renal, and pancreatic cancers and associated metastatic lesions in the abdomen. This image (bottom) was captured with Toshiba’s Aquilion 64.
Much of the recent attention on CT has been focused on cardiac applications. “With 64-slice technology, we can image the heart and its vessels,” Blackburn says. “We could see it before, but we couldn’t get a good idea about what was happening. The images are clearer now, because the acquisition is faster.”
With CT angiography (CTA), emergency-department patients complaining of chest pain can have four questions answered with one exam. “We can check for pulmonary emboli, scan the lung tissue and cardiac vessels, and measure the ejection fraction,” Blackburn says. The procedure is noninvasive and fast.
According to Rao, “Up to 30 percent of patients who undergo cardiac cath are negative. Other patients refuse the procedure. For these patients, CTA may exclude coronary disease without the invasiveness.”
She suggests that as CTA becomes routine, the medical community might need to ask at what level an intervention is necessary. “If we begin to use CTA as a screening study, will we do more unindicated interventions?” Rao asks.
We Think CT
In stroke management, intercranial CTA often is paired with CT perfusion (CTP), which enables providers to determine which areas of the brain are still viable and can be saved.
“The advances in neurological imaging are huge,” says Blackburn, whose institution specializes in neurology patients. She cites functional imaging, brain perfusion, the ability to view potential areas of changing tissue, and vascular imaging in the brain as areas where the improvements have been rapid and valuable.
“Time is brain,” Steidley adds. “The sooner a diagnosis is made, the sooner more brain can be saved.”
TAMS’ Cooper expects the application to grow even more with the next advances in CT. “CTP for the brain was expanded by the 64-slice scanner and 32 millimeters of coverage,” he says. “More slices will grow the coverage and enable whole-organ perfusion.”
We Breathe CT
CT’s use in the pulmonary region is not restricted to pulmonary emboli. It is also an advanced lung-analysis tool used in the diagnosis and treatment of chronic obstructive pulmonary disease (COPD) and lung cancer.
“For COPD, CT can do precise, volumetric measurement as well as determine the specific architecture of the lung,” says Sholom Ackelsberg, GE Healthcare’s general manager for molecular imaging and CT research.
Adds Steidley, “CT is valuable in all areas of cancer diagnosis and staging: assessing lung nodules, diagnosing and measuring the pulmonary lesions, and determining the efficacy of treatment.”
We See CT
CT also has proven valuable in viewing the colon, though its use as a screening tool for colon cancer has not been completely adopted. “[At Thomas Jefferson,] we do perform virtual colonography, but not as a screening study. Rather, it’s used with patients who have failed colonoscopies,” Rao says. Because it still requires prep, Rao believes that traditional colonoscopy, which allows immediate treatment, is probably more efficient.
Blackburn notes that virtual colonography is not frequently performed at St Joseph’s, either. “It was used early on, but due to a lack of training, the radiologists were not comfortable reading the exams, and its use has tapered off,” she says, suggesting that the procedure would be better suited to an institution that performs frequent CT colonoscopies.
“Virtual colonography has historically been tedious, but with new advanced application algorithms, the review time has been shortened from hours to minutes,” Steidley says, citing flattening technology as one of these advances.
Training, equipment, and accuracy are common issues that impede the technology’s widespread acceptance. But proponents aim to increase its use, with developments looking at less prep and greater proof of efficacy. More clinical trials comparing virtual colonography to traditional methods are necessary.
“Even if virtual colonoscopy is not as accurate as traditional methods, with greater screening compliance, proponents believe the overall health benefit would still be greater,” Ackelsberg says.
Plays Nicely With Others
CT offers huge benefits when combined with other modalities. This is seen most frequently in nuclear medicine with PET and SPECT. Ackelsberg estimates that 95% of these applications are performed in oncology. “We can track the motion of lesions in the body in real time, which is good for pre-op and radiation therapy planning,” he says.
According to Akelsberg, CT is assuming a bigger role in the operating suite. He recalls how 25% of a recent focus group was devoted to CT in the surgical unit. CT fluoroscopy already allows physicians to perform biopsies more accurately and much faster.
Adds Steidley, “The use of interventional CT is increasing. The estimate on CT-guided procedures is five percent of total CT use in North America.”
Research also is being done with other modalities, though none have yet caught on like nuclear medicine. Some expect that CT and MRI will increasingly be used together over the next 10 years. But Rao asks where it might end. “There are advantages to having modalities within the same instrument, but fusion software does a good job. Do we need an instrument for every fused application?” she asks.
And when it comes to the third dimension, Blackburn asks if we need 3-D imaging for every application. “When it first came out, every case had a 3-D rendering. It was the ooh-aah factor. Over time, we discovered that it was good for some things, but for others, it was just fluff,” she says. Now, 3-D imaging is usually used in orthopedics or brain imaging.
“Three-dimensional imaging is really more of a benefit to nonradiologists,” Cooper says. “Radiologists are used to the axial axis but use 3-D imaging to summarize the diagnosis for referring physicians.”
CT in the Future
Manufacturers are coming out with wider-bore machines that provide more room for interventional therapies as well as larger patients, which have been a growing challenge?literally. Even without big-breakthrough technology, manufacturers are making constant improvements to enhance performance.
Portability, safety, and education are all areas where development is under way. The completion of clinical trials will contribute to the modality’s credibility and could lead to greater reimbursement and use.
“CT has always been cool because it reinvents itself and pushes the envelope in new clinical areas,” Duchinsky says. That push could mean that the slice wars aren’t over but are only heating up.
Wren Davis is a contributing writer for Medical Imaging.