Dynamic chemical shift imaging for image-guided thermal therapy: Analysis of feasibility and potential

Abstract

A fast chemical shift imaging (CSI) technique based on a multiple gradient-recalled acquisition using a small number of echoes with intentional aliasing of the reference lipid peak is studied to determine its feasibility for temperature monitoring. Simulations were implemented to find parameters where the lipid and water peaks can be measured using a Fourier-based peak fitting approach as well as using an innovative autoregressive moving average technique. A phantom consisting of 50% mayonnaise/50% lemon juice was calibrated to temperature and compared to literature values. A porcine kidney was treated ex vivo with an external laser and imaged with the CSI technique with comparisons to temperature readings from a fluoroptic monitoring system and complex phase difference (CPD) calculations. To demonstrate the technique in vivo, a Balb/c mouse with a CT26 xenograft in the subcutaneous lower back was treated using gold-coated, silica-core nanoshells heated with an 808 nm interstitial laser. Compared to standard CPD techniques using a two-dimensional fast spoiled gradient recalled echo, this technique maintains spatiotemporal resolution, has high signal-to-noise ratio and accuracy over a wide range of T2* tissue values, can separate water and lipid signals, and additionally can use the lipid peak, when present, as an internal reference.

Analytical solution to heat equation with magnetic resonance experimental verification for nanoshell enhanced thermal therapy

“…To perform such calculations for in vivo data would require special attention especially to the boundary conditions as they would be nonuniform. This is where laser thermal therapy would be of great advantage; it can produce rapid temperature rises in a confined space in a short time, 158C in 85 seconds [9] and so confining the treatment to a small region of an organ. To treat an entire organ such as the prostate multiple laser treatments would be required.…”

Hepatic glycosphingolipid deficiency and liver function in mice

“…To calculate the coefficients α k and β k , a set of overdetermined equations need to be solved. We used an approach based on Prony's method (25) and the iterative Steiglitz–McBride (SM) algorithm (30), as done in an ARMA‐based approach for MR temperature imaging (31). Both algorithms are used in applications such as digital filter design and communications (25).…”

Effects of Near-infrared Laser Irradiation of Biodegradable Microspheres Containing Hollow Gold Nanospheres and Paclitaxel Administered Intraarterially in a Rabbit Liver Tumor Model

“…Magnetic resonance temperature imaging was performed in a 1.5T clinical scanner (Excite HD, GE Healthcare Technologies, Waukesha, WI) using a quadrature transmit and receive knee coil. A multi-echo gradient-recalled echo sequence using a 12 echo train with 3.4-ms spacing was used for fast high-resolution chemical shift imaging in order to measure temperature-dependent changes in the proton resonance frequency shift (9). Acquisition parameters were as follows: repetition time (TR) = 40 ms, echo time (TE) = 2 ms, flip angle = 30°, acquisition matrix = 128 × 128 (zero padded to 256 × 256), field of view = 180 mm, slice thickness = 4 mm, and receiver bandwidth = 244 Hz/pixel.…”

“…Acquisition parameters were as follows: repetition time (TR) = 40 ms, echo time (TE) = 2 ms, flip angle = 30°, acquisition matrix = 128 × 128 (zero padded to 256 × 256), field of view = 180 mm, slice thickness = 4 mm, and receiver bandwidth = 244 Hz/pixel. Temperature changes were estimated from the 12-echo chemical shift imaging acquisition by using an iterative autoregressive moving average algorithm (9). A temperature sensitivity coefficient of –0.01 ppm/°C was used.…”