What is PET attenuation correction?

This loss of detection of true coincidence events is called attenuation. It is lower in the body surface than deep in the body, low in lungs, and especially high in dense tissues such as bones, leading to severe artifacts in PET image, unless it is corrected during image reconstruction.

What is attenuation correction?

Attenuation correction is a mechanism that removes soft tissue artifacts from SPECT images. The size of the patient and the amount of tissue between the heart and the detector lead to attenuation artifacts that adversely affect the image of the heart.

What is CT attenuation value?

Terminology. The CT attenuation value is defined as the radiodensity of each material and is expressed in HUs, in which the radiodensity of distilled water at the standard pressure and temperature was defined as 0 HU, whereas that of air was defined as -1000 HU.

What is beam attenuation in CT scan?

The gray levels in a CT slice image correspond to X-ray attenuation, which reflects the proportion of X-rays scattered or absorbed as they pass through each voxel. X-ray attenuation is primarily a function of X-ray energy and the density and composition of the material being imaged.

What are the methods of attenuation in PET imaging?

In combined PET/CT systems, a CT scan is used to provide the PET attenuation correction information6. The attenuation of x-rays transmitted through a patient is the source of CT contrast, and also directly related to electron density.

What does attenuation mean in MRI?

Attenuation. Reduction of power, e.g., due to passage through a medium or electrical component. Attenuation in electrical systems is commonly expressed in dB.

Why do we need attenuation correction?

The use of accurate attenuation correction can provide valuable information in making the correct diagnostic interpretation. However slight misalignments of the transmission and emission scans, often due to patient motion, can result in artifacts in the attenuation-corrected images.

What does attenuation mean in medical terms?

Medical Definition of attenuation : a decrease in the pathogenicity or vitality of a microorganism or in the severity of a disease. attenuation.

How will an images on a PET scanner can be acquired?

PET scanners typically consist of multiple detector rings (see Chapter 18, Section B). However, PET scanners also can acquire projection data at oblique angles between detector rings (see Chapter 18, Section C and Fig. 18-24).

Can a CT scanner do a pet attenuation correction?

The goal of this work is to determine if we can perform attenuation correction of the PET emission data using accurately aligned CT attenuation information. We discuss possible methods of calculating the PET attenuation map at 511 keV based on CT transmission information acquired from 40 keV through 140 keV.

How is attenuation correction used in a 3D scanner?

This method of attenuation correction is intended for use in a single scanner that combines volume-imaging (3D) PET with x-ray computed tomography (CT) for the purpose of providing accurately registered anatomical localization of structures seen in the PET image.

Why do we use CT in a PET scan?

• Attenuation is the largest correction we apply to the PET data • Artifacts in the CT image propagate into the PET image, since the CT is used for attenuation correction of the PET data • Difference in CT and PET respiratory patterns Can lead to artifacts near the dome of the liver unless motion compensation methods are used • Contrast agents,

What causes an attenuation artifact in a PET image?

Metal translates to high attenuation coefficient (even higher than bone) High density materials, such as metal, cause increases in attenuation of the CT x-rays. In turn, excessive amount of photons are added to the PET image From a CT standpoint usually a streaking artifacts is seen.