Hybrid Imaging (SPECT/CT and PET/CT)—Improving the Diagnostic Accuracy of Functional/Metabolic and Anatomic Imaging

https://doi.org/10.1053/j.semnuclmed.2009.03.004Get rights and content

In-line combined systems, single-photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT, allow an instant generation of fused images of scintigraphy and CT data. The accumulated clinical data on the use of these systems in various clinical scenarios indicate that this hybrid technology improves the diagnostic accuracy as compared to scintigraphy and CT alone and even to side-by-side interpretation of scintigraphy and CT, which were acquired separately. The improved diagnostic accuracy is reflected by improving image quality of SPECT and PET, detection of more clinically relevant lesions, better localization of disease and differentiation between physiologic and pathologic uptake, characterization of disease by its functional and morphologic appearance before and after therapy and accurate delineation of disease, optimizing biopsy and therapy planning.

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Hybrid Imaging Improving Scintigraphic Image Quality Using CT-Maps for Attenuation Correction

A primary cause for poor image quality of SPECT images is attenuation, which reduces the number of photons received by the gamma camera from the organ of interest. SPECT/CT facilitates attenuation correction using an x-ray–based patient-specific attenuation map that can be obtained rapidly and with higher accuracy than maps generated with external radionuclide sources.1, 2 Other benefits of using CT for attenuation correction include less noise, no influence of the SPECT on CT data, and no need

Hybrid Imaging for Accurate Localization of Scintigraphic Lesions and Separation Between Physiologic and Pathologic Uptake

The ability to identify disease sites based on the functional alteration induced by the disease process regardless of morphologic changes is a major advantage of nuclear medicine. The limited anatomical landmarks of scintigraphic data are, however, a drawback. Sites of increased uptake may represent disease but may also be normal physiologic findings. When scintigraphic lesion appears to represent a true disease site, it is of great importance to accurately localize it and provide the clinician

Hybrid Imaging Detecting More Lesions, Differentiating Benign From Malignant Sites, and Reaching Diagnosis by Combined Functional-Anatomical Characterization

Investigating the clinical performance of FDG-PET/CT in evaluation of cancer, Bar-Shalom et al have shown that combined PET/CT imaging led to retrospective detection of malignant lesions previously missed on diagnostic stand-alone CT or on the independent reading of the PET and CT components of the PET/CT study.89 In this study, 63 of 586 sites (11%) were detected on diagnostic CT and on the CT component of PET/CT, only after being identified on the fused images.89 In a study by Israel et al

Hybrid Imaging for Better Delineation of Tumor Boundaries: Optimizing Biopsy, Surgery, and Radiotherapy

Physicians interpreting PET/CT studies are familiar with the heterogenic tracer uptake in different locations within tumor masses and the possible discrepancy in tumor boundaries between CT and PET. Accurate definition of the boundaries of active disease may be of clinical relevance in guiding biopsy site and in planning surgery and radiotherapy fields.

Sampling error can be caused by the presence of necrotic areas within the tumor mass or because of the heterogeneity in tumor aggressiveness in

Hybrid Imaging for Assessment of Disease Activity in the Presence Residual Morphologic Abnormalities After Therapy

Assessment of disease activity after therapy is a major task of functional imaging in variable oncologic and nononcologic clinical scenarios as no infrequent structural abnormalities may remain after an eventually successful therapy. The degree of confidence in detecting or excluding active disease can be improved by fused imaging, which specifically determines the location of tracer within residual abnormalities detected on CT. This is beneficial if normal anatomy is distorted or when the

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