Which imaging modality uses single photon emission to create tomographic images?

Which imaging modality uses single photon emission to create tomographic images?

• A. X-ray
• B. MRI
• C. Ultrasound
• D. SPECT

Answer: (D)

Single photon emission to create tomographic images is a hallmark of SPECT. In this modality, a patient is given a radiotracer that emits gamma photons. Detectors arranged around the body pick up these photons from multiple angles as they rotate, and computer reconstruction builds cross-sectional, 3D images showing where the tracer concentrates. This provides functional information about tissues, such as blood flow or metabolic activity, not just anatomy. X-ray imaging uses external X-ray beams to measure attenuation and forms 2D images or CT images from attenuation data, not from spontaneous photon emission inside the body. MRI relies on magnetic fields and radiofrequency signals to image hydrogen nuclei, and ultrasound uses reflected sound waves. None of these detect single-photon emissions from a radiotracer like SPECT does.

Single photon emission to create tomographic images is a hallmark of SPECT. In this modality, a patient is given a radiotracer that emits gamma photons. Detectors arranged around the body pick up these photons from multiple angles as they rotate, and computer reconstruction builds cross-sectional, 3D images showing where the tracer concentrates. This provides functional information about tissues, such as blood flow or metabolic activity, not just anatomy.

X-ray imaging uses external X-ray beams to measure attenuation and forms 2D images or CT images from attenuation data, not from spontaneous photon emission inside the body. MRI relies on magnetic fields and radiofrequency signals to image hydrogen nuclei, and ultrasound uses reflected sound waves. None of these detect single-photon emissions from a radiotracer like SPECT does.