Single photon emission computed tomography (SPECT)

Last revised by Raymond Chieng on 14 Mar 2023

Single photon emission computed tomography (SPECT) is a three-dimensional nuclear medicine imaging technique combining the information gained from scintigraphy with that of computed tomography. This allows the distribution of the radionuclide to be displayed in a three-dimensional manner offering better detail, contrast and spatial information than planar nuclear imaging alone.

SPECT machines combine an array of gamma cameras (ranging from one to four cameras) which rotate around the patient on a gantry. SPECT may be also combined with a separate CT machine in a form of hybrid imaging; single photon emission computed tomography-computerized tomography (SPECT-CT) mainly for the purposes of attenuation correction and anatomical localization 1.

Gamma cameras rotate around the patient providing spatial information on the distribution of the radionuclide within tissues. The use of multiple gamma cameras increases detector efficiency and spatial resolution. The projection data obtained from the cameras are then reconstructed into three-dimensional images usually in axial slices 1-3. When SPECT-CT is used, attenuation correction and higher resolution anatomical localization can be achieved 1.

Upon installation of the SPECT system, tests should be performed to ensure the system functions properly in a proper and stable environment. The sets of tests that should be performed are as below 4:

  • physical and mechanical inspection of the system

  • determine the absolute size of a pixel

  • determine the tomographic uniformity

  • determine the tomographic resolution in air

  • determine the tomographic resolution with scatter

  • determine the offset for center of rotation and alignment of axes

  • determine slice thickness at the central slice

  • determine the variations of uniformity and sensitivity with rotation of the system

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Cases and figures

  • Case 1: breast cancer lytic metastasis
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  • Case 2: vertebral compression fracture
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  • Case 3: osteomyelitis
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  • Case 4: osteomyelitis
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  • Case 5: prostate cancer skeletal metatases
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  • Case 6: Alzheimer disease
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  • Case 7: osteomyelitis - Tc99m MDP SPECT/CT
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  • Case 8: normal brain perfusion SPECT
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  • Case 9: localization of chyle leak with Tc-99m colloid (SPECT/CT)
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  • Case 10: vertebral hemangioma (Tc-99m RBC labeled SPECT/CT)
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  • Case 11: dacryocystocele with obstructed nasolacrimal duct (dacryoscintigraphy and SPECT/CT)
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  • Case 12: Tc-99m sestamibi parathyroid scan - parathyroid adenoma
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