Dual-Modality Imaging with
AMRITA VISWA VIDYAPEETHAM
2. INSTRUMENTATION FOR SPECT/CT.
3. MATERIALS AND METHODS.
4. SPECT/CT IMAGING.
I. IMAGE ACQUISITION.
II. IMAGE REGISTRATION AND IMAGE FUSION.
5. SPECT/CT DUAL MODALITY IMAGING.
6. CHALLENGES FOR SPECT/CT IMAGING.
7. ADVANTAGES OF SPECT/CT
8. APPLICATIONS OF SPECT/CT
Dual-modality imaging is an in vivo diagnostic technique that obtains structural and functional information directly from patient studies in a way that cannot be achieved with separate imaging systems alone. Dual-modality imaging systems are configured by combining Computed tomography (CT) with radionuclide imaging (using single-photon emission computed tomography (SPECT)) on a single gantry which allows both functional and structural imaging to be performed during a single imaging session without having the patient leave the imaging system. SPECT is a tomographic scintigraphic technique in which a computer-generated image of local radioactive tracer distribution in tissues is produced through the detection of single-photon emissions from radionuclides introduced into the body. CT is a tomographic imaging technique that uses an external x-ray source to produce 3-dimensional anatomic image data. Combined SPECT/CT devices provide both the functional information from SPECT and the anatomic information from CT in a single examination. Some studies have demonstrated that the information obtained by SPECT/CT is more accurate in evaluating patients than that obtained from either SPECT or CT alone. To facilitate the process of correlating structural and functional information, investigators at UCSF, have developed a new class of diagnostic instrumentation that combines x-ray CT and radionuclide imaging with SPECT.
2. Instrumentation for SPECT/CT
The “dual-modality” systems use separate detectors for x-ray and radionuclide imaging, with the detectors integrated on a common gantry to simplify patient handling, data acquisition, and coregistration of the CT and radionuclide image data. A SPECT/CT scanner is an integrated device containing both a CT scanner and a SPECT g-camera with a single patient table and therefore capable of obtaining a CT scan, a SPECT scan, or both. If the patient does not move on the bed between the scans, the reconstructed SPECT and CT images will be spatially registered. CT and radionuclide scans are acquired by translating the patient from one detector to the other while the patient remains on the patient table. This allows the CT and radionuclide images to be acquired with a consistent scanner geometry and body habitus, and with minimal delay between the two acquisitions.
3. Materials and Methods
The radionuclide image is obtained using a GE 600 XR/T scintillation camera with a large rectangular field of view (approximately 400 mm ×500 mm). SPECT images are acquired as 128 × 128 image matrices. The SPECT images are reconstructed with a filtered back projection algorithm. CT images are obtained with a GE 9800 Quick CT scanner using a standard technique (140 kVp, 120 mA). Images acquired with a 512 × 512 matrix with field of view (FOV) of 400–450 mm and are reconstructed using filtered-backprojection. Patients were instructed to breathe normally and the intention was to acquire the CT during tidal breathing. Total imaging time for most studies was approximately 35 minutes,...
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