Systems from left: Toshiba’s T.cam cardioE fixed 90-degree camera; Siemens’ E.cam duet. Background images from Siemens E.cam duet.

Single photon emission computed tomography (SPECT) nuclear medicine studies have been around since the early 1960s. Improvements in SPECT systems since then have propelled this technique into diagnostic and treatment applications across an array of clinical settings with cardiology and oncology capturing center stage.

The current buzz about this imaging modality highlights fusion imaging, refinements and redesign in SPECT cameras and overall systems, exciting developments in radiopharmaceuticals used for diagnosis and treatment through molecular imaging, with OEMs increasing their product portfolios for this specialized functional imaging market. With more than 20 million nuclear medicine studies performed each year, it is no wonder advances are proceeding at breakneck speed.

The Society of Nuclear Medicine Annual meeting this month is scheduled to serve as a launch site for major manufacturers to introduce their latest offerings.

Hybrid SPECT-CT
Infinia is the new system to be unveiled by GE Medical Systems (GEMS of Waukesha, Wis.) at SNM that combines the imaging modalities of SPECT and CT on a single gantry.

“The camera is a totally new platform,” explains Jeff Kao, general manager of global nuclear medicine for GEMS. “We’ve designed it with articulating heads and the detector is different.”

New radioactive tracers that are used in high-energy imaging exhibit multiple energy peaks. This detector is designed to calibrate not only to major peak, but also to adjust for linearity and uniformity correction for each of the peaks. For example, an energy map for Gallium contains three peaks and by calibrating appropriately, image quality improves.

The addition of CT provides accurate anatomic data that is inherently registered with the SPECT study and can be readily fused to other scan results.

“At the same time we’re introducing a new workstation,” continues Kao. “It allows us to fuse any data sets: MR/CT, MR/nuclear medicine, or any two data sets.”

GE’s primary work in this field was accomplished with their hybrid PET/CT system, and it has now been expanded to include this application. All of the software has been optimized to run on a standard Microsoft Windows NT system. Kao explains that because they developed the camera and the Xeleris workstation simultaneously, they have been able to improve the workflow for procedures. This has decreased the number of “mouse clicks” required to acquire, process and display or store images, and automates the entire workflow procedure based on predetermined protocols.

CT-based attenuation correction is another benefit reaped by combining the two technologies into a single hybrid system.

Accuracy in attenuation correction can make or break the quality of a SPECT study. These nuclear medicine scans are accomplished by injecting a radioactive tracer into the blood stream of a patient, and a photon detector array is tracked around the patient’s body to acquire data from several different angles. This technique allows analysis of the position and concentration of radionuclide distributions. In order for photons to exit and be captured on the detectors, they must first pass through organs and tissue. Without mathematical reconstruction algorithms to increase resolution that take those variables into account, inaccurate readings may result.

Ora Israel, M.D., director of nuclear medicine at the Rambam Medical Center in Haifa, Israel, works with the first installed Infinia system. She considers this approach a revolutionary development in nuclear medicine imaging.

“One of the things that happens with Infinia is that the new SPECT/CT is much more user friendly in terms of the technologists and doctors, because of the workstation,” Israel says. “I assume it will make it more appealing to the nuclear medicine community.”

Israel and her colleagues use the system on a daily basis for all types of procedures from oncology to cardiology, orthopedics to emergency nuclear medicine. She relates that their technologists readily turn to this system for imaging studies because they appreciate its features. The combined imaging capabilities add valuable information to their diagnostic and treatment decision-making processes.

Robert Hellman, M.D., associate professor of radiology at the Medical College of Wisconsin (Milwaukee), works with the first U.S. installed Infinia system at Froedert Hospital (Milwaukee) and is pleased with the refinements to the camera and the processing side of this system. They use the CT portion of the system for attenuation correction and for localizing abnormalities.

Hellman describes other technical differences that are quite important to the technologists. The first improves efficiency by means of a secondary viewing screen configured as a ‘slave’ to the primary screen. This feature permits a technologist to review a study in progress without being required to turn back to the acquisition station’s primary monitor.

Another refinement involves the capability of the persistence scope that is important for patient positioning, and Hellman says his technologists appreciate those enhancements as well.

Finally, he relates that when the proper parameters are set, the completion of a study on the Infinia starts the processing protocol with one step rather than two separate steps and that expedites the overall process.

“There isn’t an area in nuclear medicine where we use our dual-head cameras where we wouldn’t use this,” concludes Hellman.

Flexibility defined
Philips Medical Systems North America (Bothell, Wash.) offers their uniquely configured Skylight system for the nuclear medical community.

Detectors suspended on arms from the ceiling allow the Philips Medical Systems’ Skylight to move freely in 3D space.

Instead of having detectors fixed to a gantry, they are suspended on arms from the ceiling, and therefore the individual detectors are free to move in any configuration in three-dimensional space.

David Rollo, M.D., Ph.D., chief medical officer at Philips explains that when SPECT imaging is accomplished, Skylight uses the equivalent of a Global Positioning System to have the detectors communicate about their relationship to the center of rotation. The computer controls movement of the detectors around the patient focused to an accuracy of within approximately a millimeter of the center of rotation. This configuration permits scans to be performed if a patient is standing, sitting, or reclining.

Rollo continues that of even greater significance are the refinements to the acquisition station. With traditional cameras, a single data set is collected. This system is capable of acquiring 16 separate data sets simultaneously. This feature gains importance when considering the use of some of the new radioisotopes with multiple energy peaks, or combined studies that review myocardial perfusion with and without gating techniques plus wall motion plus ejection fraction studies performed concurrently.

“When these studies are performed simultaneously, they are an accurate reflection of what is happening with the patient because they are captured at the same time,” concludes Rollo.

Advancements in molecular imaging are designed not only to target lesions in the diagnostic process, but also to use radioactive markers to deliver treatment directly to tumors in the case of oncology applications. The Skylight system was specifically designed for use with molecular imaging techniques.

“If the target picks up the molecular probe, you can re-deliver that probe with therapy, and it will attack that specific target,” explains Rollo. “The theory of molecular imaging and treatment is that you only treat the tumor, not surrounding tissues.” At this point, these techniques have been applied successfully to some patients with non-Hodgkin’s Lymphoma whose tumors were resistant to standard treatment.

Richard Myers, M.D., medical director of nuclear medicine for the Radiological Associates (Sacramento, Calif.), has used Skylight through its beta-testing phase for the past four years. Now the practice has two clinical units in outpatient offices and plans to purchase systems for a couple of hospital labs as well.

The system has proven valuable for a wide array of clinical applications, with cardiac studies the most frequent, followed by complicated bone studies where complex anatomy is involved (such as the spine), brain studies and liver studies where another imaging modality such as CT has identified a lesion.

“Most of the dual-headed systems are fixed in a circular orbit around a bed where the patient lies,” explains Myers. “This system can do that as a starter, but then the heads can do just about anything after that. They are controlled by intricate robotics to move up, down, sideways and they can do that independently.”

The benefits to that level of flexibility include increased efficiency without compromising image quality.

Myers describes that the heads are as efficient as anything on the market, but imaging times are decreased as a result of flexibility of positioning and the ability to do different protocols. In some studies, they are able to accomplish the task twice as fast because they can acquire two views with the two different cameras simultaneously. Because each head can be placed independently in three dimensional space, the flexibility of the system permits scans that would be impossible on a traditional fixed head system.

Philips’ Rollo explains that they are pursuing the DICOM fusion option to combine CT and SPECT images to take advantage of the capabilities of the 16 or 32 multislice CT systems on the market. Especially in the case of cardiac studies, he asserts that the anatomical detail of cardiac vessels provided by the multislice CT enhances the results of the subsequent SPECT study.

“You could do a multislice cardiac study to identify the vessels, and then DICOM that information into the SPECT study and fuse the images,” explains Rollo. “You can see the narrowing of the vessel, and also look at perfusion, wall motion and ejection fraction as the functional information that applies significance to the narrowing.”

Enhanced products
Siemens Medical Solutions’ Nuclear Medicine Group (Hoffman Estates, Ill.) has introduced the latest generation of their nuclear medicine products called the e.cam Signature series. The line has seven models of the camera, which share the same detectors, gantry and computer platforms to facilitate use and reduce the need for additional training.

Raffi Kayayan, Ph.D., product marketing manager for Siemens Nuclear Medicine Group, explains that integrated components yield a number of benefits for the user.

The more than 40 Siemens imaging products run on syngo platforms and can be connected through a network to the e.soft workstation. Images are stored based on DICOM standards to facilitate ease of use. They began this integration process several years ago to provide a level of connectivity between imaging modalities and all electronic patient records, laboratory results and other clinical data that would prove beneficial in the management of patient care. Their goal is to streamline functions while providing all necessary data for decision-making.

“Our nuclear medicine users are one click away from accessing any patient images that are done in other modalities,” says Kayayan. “They may have CT, MR, angio, etc., and the nuclear medicine person sitting at the e.soft workstation can view the nuclear studies, and then if the workstation is networked with the other systems, he can access the images from the other modalities and view them side by side.”

In addition to that capability, they also offer PET (positron emission tomography) processing and viewing software on their SPECT e.soft workstation which allows them to view the PET studies on the same platform. Their reconstruction algorithms provide improved resolution, image contrast and lesion detectibility. Using 3D OSEM (ordered subset expectation maximization) algorithm, they are able to offer three-dimensional images.

One of the other features now offered as an option is called e.media that replaces the original persistence scope (p-scope) with a color monitor to enable the viewing of DVDs or videotapes. The new addition can be used to provide educational information about the scan, or purely for entertainment to reduce the boredom of a SPECT study for the patient.

Helen Nadel, M.D., FRCPC, pediatric radiologist and nuclear medicine physician and head of the division of nuclear medicine at the Children’s and Women’s Health Centre (Vancouver, British Columbia, Canada), uses SPECT studies for a variety of clinical applications, primarily in a pediatric setting. She says that when they inject radioactive markers into a child, they want to make sure that they will obtain the image data they need to manage the child’s problem.

“We do not sedate children in our department as a general rule,” Nadel explains. “We would use sedation for brain imaging for children with seizure disorders or mental impairments.”

Children may be anxious given the size of the machine and the uncertainty of what they will experience.

With e.media, they have found that their patients, watching a video or DVD of their choosing, are distracted sufficiently to enable them to lie still which means the quality of the images is improved.

“We’ve had it since the end of September and it has taken the pain out of the study for all ages,” says Nadel. In fact, because the scans usually take less time than the movie they’re watching, children sometimes do not want to leave the table.

Considering that many of their patients have chronic conditions requiring a number of scans over the years, making the experience more pleasant is a result they are happy to be able to provide.

Toshiba America Medical Systems Inc. (Tustin, Calif.) is announcing a broadening of its product line to three new camera configurations. Adel Girgis, national product manager for Toshiba, describes the three camera configurations they offer. Image fusion software is available for all systems.

The first is a large field of view single-head system that is capable of completing all SPECT studies, and general planar scans. It is a full-featured system with a large field of view rectangular detector for a price-conscious practice.

The second is a fixed 90-degree camera, the T.cam CardioE that is designed to meet the needs of a busy cardiologists’ office and to accomplish most cardiac studies.

The third camera system is a large field of view variable angle dual head camera that is capable of being deployed in any configuration: 180 degrees, 90 degrees, 102 degrees, or one detector can be used while the other is silent. In their SPECT version of this camera configuration, they offer the customer either thin or thick crystal for their oncology studies.

“Our intention is to offer a product line that gives all of the features our customers need, but helps them in driving down their operating costs,” Girgis explains.

Conclusion
SPECT imaging has proven valuable for a number of different patient conditions. While cardiology represents about half of the nuclear scans in the U.S., oncology, orthopedics, and neurology applications are equally valuable. With advances that are currently underway in the development of new radiopharmaceuticals, many industry leaders anticipate a growth in this imaging modality in years to come. As computer power escalates, processing of images is facilitated and image data sets are enhanced. Combining functional imaging data from SPECT with anatomical detail offered by CT points to increased confidence in diagnosis and disease management.