Molecular imaging of tumor-associated angiogenesis using a novel magnetic resonance imaging contrast agent targeting αvβ 3 integrin.

Background: The recent introduction of biological anticancer therapy has renewed the interest in functional imaging of tumor-associated angiogenesis (TAA) as a tool to monitor early therapy response. The present study evaluated imaging of TAA using P1227, a novel, small molecular magnetic resonance imaging (MRI) probe targeting αvβ3 integrin.

Methods: HT29 human colorectal cancers were grown in athymic mice.

P-glycoprotein at the blood-brain barrier: kinetic modeling of 11C-desmethylloperamide in mice using a 18F-FDG μPET scan to determine the input function.

Purpose: The objective of this study is the implementation of a kinetic model for 11C-desmethylloperamide (11C-dLop) and the determination of a typical parameter for P-glycoprotein (P-gp) functionality in mice. Since arterial blood sampling in mice is difficult, an alternative method to obtain the arterial plasma input curve used in the kinetic model is proposed.

Methods: Wild-type (WT) mice (pre-injected with saline or cyclosporine) and P-gp knock-out (KO) mice were injected with 20 MBq of 11C-dLop, and a dynamic μPET scan was initiated.

First order correction for T2*-relaxation in determining contrast agent concentration from spoiled gradient echo pulse sequence signal intensity.

Purpose: To investigate the accuracy of a method neglecting T(2)*-relaxation, for the conversion of spoiled gradient echo pulse sequence signal intensity to contrast agent (CA) concentration, in dynamic contrast enhanced MRI studies. In addition a new closed form conversion expression is proposed that accounts for a first order approximation of T(2)*-relaxation.

Materials And Methods: The accuracy of both conversion methods is compared theoretically by means of simulations for four pulse sequences from literature.

Precision analysis of kinetic modelling estimates in dynamic contrast enhanced MRI.

Object: Dynamic contrast enhanced MRI and pharmacokinetic modelling provide a powerful tool for tumour diagnosis and treatment evaluation. However, several studies show low reproducibility of the technique and poor precision of the transendothelial transfer constant K (trans). This work proposes a theoretical framework describing how finite signal-noise-ratio (SNR) in the MR images is propagated throughout the measurement protocol to uncertainty on the kinetic parameter estimates.