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Single Photon Emission Computed Tomography (SPECT) is used for imaging organ function, and in oncology, for detection of a specific types of tumors. SPECT images provide specific pathological uptake information, however it is sometimes difficult to determine the position of the uptake with respect to the patient anatomy. The use of co-registered SPECT and CT images provides a tool to overcome this ambiguity, and thus increase the diagnostic accuracy of the examinations. Another important application of the CT is its use to make a relatively reliable attenuation correction of the SPECT-study, an attribute that is significant in  nuclear cardiology.

Important principles

CT equipment can have capabilities to acquire lower dose images to be used for anatomical localization and attenuation correction, as well as higher resolution images to be used for diagnostic applications.  If using (higher dose) diagnostic CT imaging, additional structural shielding may be required in accordance with national regulations. SPECT/CT equipment is usually placed in a nuclear medicine department which means that the NM-staff must be fully trained to run both the SPECT and the CT machines, including training in radiation protection issues. Cooperation of the NM department with a radiological department is necessary. If diagnostic CT-studies are acquired with SPECT images they should be analyzed by a qualified radiologist together with a nuclear medicine specialist. All imaging and diagnostic assessment should be made following recommendations from professional organizations.  A quality control programme should be in place and should include not only the individual types of equipment but also parameters important for the combined image registration.

Introduction to references

The IAEA has published a document regarding the clinical use of SPECT/CT, which include a section on training. Structural shielding of a CT-installation is discussed on the IAEA website Radiation Protection of the Patient. The basic physics of SPECT/CT is presented in the IAEA Handbook of Nuclear Medicine Physics. The reference to AAPM CRCPD Annual Meeting contains several relevant lectures that were recorded live. For a detailed description of SPECT and CT separately, as well as quality control issues, the reader is referred to other sections of this website.