WE‐E‐204B‐05: MR Relaxation Properties for Fe‐Containing MWCNTs and Potential for Combined MR Imaging and Tumor Ablation Therapy

Abstract

Purpose: Investigate MR relaxation and laser heating properties of Fe‐containing Multi‐Walled Carbon Nanotubes (MWCNTs), to determine their potential uses as Magnetic Resonance Imaging (MRI) Contrast Agents (CAs) and Laser Absorbing Agents (LAAs) for laser‐induced thermal therapy (LITT) for cancer. Methods and Materials: MRI relaxation properties of 3 different Fe‐containing MWCNT solution (600mg, 200mg 60mg Fe) were determined in a 1.5T MR scanner using a multi‐echo pulse sequence. To study in vivo MR properties for LITT of cancer, two breast tumor bearing mice were intratumorly injected with 600mg Fe MWCNTs and N‐Doped MWCNTs which contains very few iron articles as a comparison, followed by Near Infared (NIR) LITT (3W/cm2, 30seconds). 7T MR T2 maps of the mouse tumors with instilled MWCNTs were acquired at 5 time points during and after LITT. Additionally, LITT using 600mg Fe‐containing MWCNTs was evaluated using a larger group of mice (n=4). Results: MWCNT R2 (or 1/T2) measurements, shows that the 600mg Fe MWCNTs' R2 is about 5 times higher than R2 for a commercial MR CAs (Feridex I.V.® (ferumoxides)). Thus, Fe‐containing MWCNTs may perform very well as T2‐weighted MR CAs. Futhermore, the in vivo MR study shows that 600mg Fe MWCNTs CAs effectively change the tumor T2 relaxation from 61ms to 22ms and creates a void signal in the implanted target area, enabling tumor localization for MR‐guided LITT. After one week post‐LITT, Fe‐containing MWCNTs were still located in the implanted target region, indicating minimum migration/ diffusion, and T2 relaxation properties were stable. The in vivo study also showed that 600mg Fe‐containing MWCNTs + LITT show potential as a new cancer therapy. Conclusion: Fe‐containing MWCNTs have favorable MR relaxation values and biological stability, and show great potential as a dual‐modality agent for T2 MR Contrast imaging and NIR laser absorption for MR‐guided LITT.