MRAC capable phantom fluids : A study of hybrid phantom fluids for attenuation correction in PET/MRI and PET/CT
Year: 2021
Type: dissertation
Abstract: Background. Classification based PET/MRI attenuation correction methods utilize a PET/CT derived method of identifying tissues and assigning them attenuation values. Phantoms for PET/MRI generally use theoretical attenuation maps.Aim. This paper investigates the creation of fluids that can be used in phantoms for PET, CT, and MRI. The focus lies on creating properties that result in the attenuation to be correctly estimated with CT and MRI systems. This is a step toward the development of hybrid phantoms with tissue equivalency in all modalities.Method. Attenuation and fat fraction is altered in water to produce a fluid that generates correct attenuation values when measured with both CT and MRI. The fat fraction influences what type of tissue the fluid is classified as in the PET/MRI system used. In turn, the tissue type has an attenuation value associated with it. An emulsion of vegetable oil and water is investigated for the manipulation of fat fractions. The CT attenuation measurement in Hounsfield is modified by altering the density of the fluid. The concentration of sodium chloride is used to modify the Hounsfield value. In the end, the phantom of oil, water, salt solution, and emulsion is validated by adding PET-isotopes. The measured attenuation-corrected radioactivity concentration in PET/CT and PET/MRI are compared.Results. The results show that modification of salt concentration is an effective and easily applicable method of altering the Hounsfield attenuation value of a liquid. The use of emulsions results in expected classification based on fat fraction. Long- and short-term stability of the emulsions may be improved. Analysis of radioactivity concentration shows comparable values between PET/CT and PET/MRI proving that the concept works.
Author: Nygren, Dag
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7030264614