September 9, 2013 — The U.S. Food and Drug Administration (FDA) has granted 510(k) market clearance for Siemens’ Symbia Intevo, the first system to completely integrate high sensitivity of single-photon emission computed tomography (SPECT) with the high specificity of computed tomography (CT) into a single modality, rather than imaging as separate overlay images. Siemens is calling the combined imaging modality technology xSPECT.
It completely integrates data from both modalities. Symbia Intevo generates high resolution and, for the first time, quantitative images. In traditional SPECT/CT imaging, the SPECT image has always been reconstructed at a low-resolution matrix — much lower than the CT portion of the exam. As a result, the CT resolution must be downgraded dramatically to the level of SPECT to enable mechanical fusion of the two modalities. xSPECT combines the images into a new, completely integrated single dataset for vastly higher resolution and quantitative images.
Aimed at the oncology market to start, an example of the imaging display at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) in June showed a traditional SPECT/CT spinal image with hot spots, but the low resolution makes it unclear if the areas of enhancement are tumors or inflammation. The combined xSPECT image greatly enhanced resolution to show the hot spots were actually inflammation caused by clearly defined spinal compression fractures. The clear, fused image also eliminates the alignment artifacts common with hybrid imaging, where the SPECT and CT images do not exactly match anatomical boundaries. The vendor said centers using the system in trials are reading the xSPECT image rather than going back and forth between the usual collage of three images showing the SPECT, CT and combined overlay image.
SPECT has traditionally been dubbed “unclear” instead of “nuclear” imaging due to its low image quality, said Mike Rittman, senior manager, product marketing, Siemens molecular imaging. He explained xSPECT offers a way to greatly clarify the image with CT-like quality. Instead of an incremental technology advance, Rittman said this is a major step forward for SPECT, involving 10 years of development and 32 pounds worth of paperwork submitted to the FDA for the approval process.
Higher Resolution Frame of Reference?
In conventional SPECT/CT imaging
, the SPECT image has always been reconstructed using SPECT's low-fidelity frame of reference. For this reason, the CT resolution has been downgraded dramatically to the level of SPECT to enable the mechanical fusion of both datasets. Siemens’ new xSPECT modality reconstructs both the SPECT and CT portions of the image using the high CT frame of reference for precise, accurate alignment that facilitates the extraction and deep integration of medically relevant information. This ability is also the basis for differentiating between tissue boundaries in bone imaging. With the xSPECT Bone feature, physicians can provide additional support for detection and distinguishing between cancerous lesions and degenerative disorders.
Symbia Intevo’s precise alignment of SPECT and CT provides physicians with essential volumetric information from the CT scan, enabling accurate, consistent and reproducible quantification, a numerical indication of a tumor’s level of metabolic activity. With the xSPECT Quant feature, the physician can apply quantitative information to aid in the assessment whether a patient's course of treatment has regressed, stabilized or grown, an assessment that is difficult to make with a purely visual assessment of the tumor.
Reduced CT Dose?
While Symbia Intevo uses more CT data than previous system, Siemens is still able to limit patient dose by offering combined applications to reduce exposure (CARE). Unique to Siemens, these applications include the CARE Dose4D technique, which can reduce patient CT radiation dose by up to 68 percent.
Increased Productivity, Throughput?
Symbia Intevo also offers applications to improve productivity and patient throughput. For example, Siemens’ Autoform collimator captures up to 26 percent more counts, or photons, that are generated from radiotracer activity as compared to conventional collimators. This increased number of counts potentially reduces image acquisition time for increased patient throughput.
Symbia Intevo and xSPECT are not commercially available in all countries. Due to regulatory reasons, their future availability cannot be guaranteed. Please contact your local Siemens organization for further details.