The AAPM/RSNA physics tutorial for residents. Introduction to emission CT

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiological Sciences

Background:

• Emission computed tomography (CT) provides crucial insights into internal radioactivity distributions within three-dimensional objects.
• This technique enhances anatomical localization and improves image contrast for diagnostic purposes.
• Understanding the fundamental principles of emission CT is vital for accurate image interpretation.

Purpose of the Study:

• To elucidate the core principles of emission computed tomography (CT) using a nonmathematical explanation.
• To describe the essential components and processes involved in generating tomographic images.
• To identify common artifacts and factors affecting the quality of reconstructed emission CT images.

Main Methods:

• Emission CT involves collecting numerous measurements (projections) at various angles around a patient.
• Projection data are organized into a sinogram, which is then processed using reconstruction filters.
• Filtered projections are backprojected to reconstruct transverse tomographic images.

Main Results:

• Successful tomographic imaging relies on stable radionuclide distribution, uniform detector response, accurate center of rotation, and complete projections.
• Image quality is influenced by reconstruction filters and adherence to underlying assumptions about projection data.
• Deviations from assumptions can lead to artifacts such as motion, uniformity, and attenuation errors.

Conclusions:

• Emission CT is a powerful tool for visualizing internal radioactivity, aiding in anatomical localization and contrast enhancement.
• Achieving high-quality tomographic images necessitates careful attention to system calibration, data acquisition, and reconstruction parameters.
• Awareness of potential artifacts is critical for accurate diagnosis and image interpretation in emission CT.