Seminars in nuclear medicine
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In nuclear oncology, despite the fast-growing diffusion of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET), single-photon emission computed tomography (SPECT) studies can still play an useful clinical role in several applications. The main limitation of SPECT imaging with tumor-seeking agents is the lack of the structural delineation of the pathologic processes they detect; this drawback sometimes renders SPECT interpretation difficult and can diminish its diagnostic accuracy. Fusion with morphological studies can overcome this limitation by giving an anatomical map to scintigraphic data. ⋯ The first reports indicate that SPECT/CT is very useful in cancer imaging because it is able to provide further information of clinical value in several cases. In SPECT, studies of lung cancer and malignant lymphomas using different radiopharmaceutical, hybrid images are of value in providing the correct localization of tumor sites, with a precise detection of the involved organs, and the definition of their functional status, and in allowing the exclusion of disease in sites of physiologic tracer uptake. Therefore, in lung cancer and lymphomas, hybrid SPECT/CT can play a role in the diagnosis of the primary tumor, in the staging of the disease, in the follow-up, in the monitoring of therapy, in the detection of recurrence, and in dosimetric estimations for target radionuclide therapy.
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Radiological (plain radiographs, computed tomography [CT], magnetic resonance imaging [MRI]) and nuclear medicine methods (bone scan, leukocyte scan) both provide unique information about the status of the skeleton. Both have typical strengths and weaknesses, which often lead to the sequential use of different procedures in daily routine. This use causes the unnecessary loss of time and sometimes money, if redundant information is obtained without establishing a final diagnosis. ⋯ Therefore, SPECT/CT should be applied whenever equivocal findings of planar bone imaging occur. It also helps to improve accuracy of leukocyte scanning to detect/exclude osteomyelitis and to define sites of inflammation. We therefore regard SPECT/CT as a valuable tool to optimize bone imaging, which might become even more important if new radiopharmaceuticals become available to image specific cell functions.
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Correlation of the anatomical and functional information presented by single-photon emission computed tomography (SPECT) and computed tomography (CT) can aid in the decision-making process by enabling better localization and definition of organs and lesions and improving the precision of surgical biopsies. Technical developments over the past 20 years have led to the development of better software techniques for image fusion and, more recently, to the development of modern SPECT/CT systems. While image fusion techniques have been in clinical use for many years, the first commercial SPECT/CT system was only developed in 1999. ⋯ Motion artifacts should be less prevalent with the faster acquisition times of modern scanners, but are still problematic in the thorax and have not yet been fully resolved as they pertain to the use of CT data for cardiac attenuation correction. As this technology matures, we can expect to see a range of SPECT/CT devices available on the market that range from low-dose 1-4 slice inexpensive CT upgrades of conventional SPECT systems, to SPECT systems incorporating 64 or 128 slices CT scanners. The cost of the high-end CT scanners will exceed the cost of the SPECT scanner and hence the justification for such devices will be heavily dependent on clear demonstration of their value in clinical practice.