The Bioimpedance Technique in Respiratory - and Dual - Gated Positron Emission Tomography Imaging

Respiratory and cardiac motion artefacts degrade image quality in positron emission tomography (PET) imaging and may significantly affect the qualitative and quantitative evaluation of images. At worst, misguided interpretation may lead to wrong diagnosis and inadequate or unnecessary treatment. The aim of this thesis was to study the feasibility of the bioimpedancebased measurement technique for respiratory and cardiac motion compensation in PET imaging. An optimized bioimpedance measurement configuration for simultaneous measurement of respiratory and cardiac gating signals was first determined based on computational modelling. The configuration was further validated against reference methods for monitoring respiration and cardiac contractions. The feasibility of bioimpedance techniques for gating in clinical settings was evaluated in oncologic and cardiac PET studies. Respiratory and cardiac bioimpedance measurements were found to have a high degree of correlation and good agreement with reference methods in monitoring respiration and cardiac contractions. In oncologic PET studies, bioimpedance-based respiratory gating resulted in a significant increase of the observed metabolic activity of lesions and a decrease of their volume. In cardiac PET studies, dual gating was found to show a significant narrowing effect on the observed myocardial wall thickness compared to plain cardiac gating. This thesis shows that bioimpedance techniques can be effectively utilized for respiratory motion compensation by respiratory and dual gating of PET imaging. Further development of bioimpedance-based respiratory motion compensation should be mainly directed to enhancing the sensitivity and linearity of the measurement configuration. National Library of Medicine Classification: QT 36, WF 141, WG 141.5.T6, WN 180, WN 206 Medical Subject Headings: Diagnostic Imaging/methods; Electric Impedance; Sensitivity and Specificity; Image Enhancement; Artifacts; Positron-Emission Tomography; Respiratory System; Respiratory-Gated Imaging Techniques; Heart; Cardiac-Gated Imaging Techniques; Neoplasms Yleinen suomalainen asiasanasto: kuvantaminen; positroniemissiotomografia; bioimpedanssi; artefaktit; liikkeet; kompensointi; kuvanlaatu; hengityselimet; sydän; kasvaimet