Real-time multislice MR-thermometry of the prostate: Assessment of feasibility, accuracy and sources of biases in patients.

Purpose: The primary purpose of this study was to evaluate the accuracy of an MR-thermometry sequence for monitoring prostate temperature. The secondary purposes were to analyze clinical and technical factors that may affect accuracy and testing the method in a realistic setting, with MR-guided Laser ablation on an ex vivo muscle sample.

Materials And Methods: An ex vivo muscle sample was subjected to Laser ablation while using a two-dimensional multislice segmented echo planar imaging sequence for MR thermometry.

Evaluation of a deformable image registration algorithm for image-guided thermal ablation of liver tumors on clinically acquired MR-temperature maps.

Background: Quantitative real-time MRI-based temperature mapping techniques are hampered by abdominal motion. Intrascan motion can be reduced by rapid acquisition sequences such as 2D echo planar imaging (EPI), and inter-scan organ displacement can be compensated by image processing such as optical flow (OF) algorithms. However, motion field estimation can be seriously affected by local variation of signal intensity on magnitude images inherent to tissue heating, potentially leading to erroneous temperature estimates.

Automatic volumetric temperature regulation during in vivo MRI-guided laser-induced thermotherapy (MRg-LITT) with multiple laser probes.

Background: Clinical Laser-Induced Thermotherapy (LITT) currently lacks precise control of tissue temperature increase during the procedure. This study presents a new method to automatically regulate the maximum temperature increase in vivo at different positions by adjusting LITT power delivered by multiple laser probes using real-time volumetric MR-thermometry.

Methods: The regulation algorithm was evaluated in vivo on a pig leg muscle.

Accuracy of 3D real-time MRI temperature mapping in gel phantoms during microwave heating.

Background: Interventional magnetic resonance imaging (MRI) can provide a comprehensive setting for microwave ablation of tumors with real-time monitoring of the energy delivery using MRI-based temperature mapping. The purpose of this study was to quantify the accuracy of three-dimensional (3D) real-time MRI temperature mapping during microwave heating in vitro by comparing MRI thermometry data to reference data measured by fiber-optical thermometry.

Methods: Nine phantom experiments were evaluated in agar-based gel phantoms using an in-room MR-conditional microwave system and MRI thermometry.

Real-time automatic temperature regulation during in vivo MRI-guided laser-induced thermotherapy (MR-LITT).

Precise control of tissue temperature during Laser-Induced Thermotherapy (LITT) procedures has the potential to improve the clinical efficiency and safety of such minimally invasive therapies. We present a method to automatically regulate in vivo the temperature increase during LITT using real-time rapid volumetric Magnetic Resonance thermometry (8 slices acquired every second, with an in-plane resolution of 1.4 mmx1.

2D multislice MP2RAGE sequence for fast T mapping at 7 T: Application to mouse imaging and MR thermometry.

Purpose: To develop a 2D radial multislice MP2RAGE sequence for fast and reliable T mapping at 7 T in mice and for MR thermometry.

Methods: The 2D-MP2RAGE sequence was performed with the following parameters: TI -TI -MP2RAGE = 1000-3000-9000 ms. The multiple dead times within the sequence were used for interleaved multislice acquisition, enabling one to acquire six slices in 9 seconds.

Radial MP2RAGE sequence for rapid 3D T mapping of mouse abdomen: application to hepatic metastases.

Objectives: The T longitudinal recovery time is regarded as a biomarker of cancer treatment efficiency. In this scope, the Magnetization Prepared 2 RApid Gradient Echo (MP2RAGE) sequence relevantly complies with fast 3D T mapping. Nevertheless, with its Cartesian encoding scheme, it is very sensitive to respiratory motion.

Compressed-Sensing MP2RAGE sequence: Application to the detection of brain metastases in mice at 7T.

Purpose: To develop a Compressed Sensing (CS)-MP2RAGE sequence to drastically shorten acquisition duration and then detect and measure the T of brain metastases in mice at 7 T.

Methods: The encoding trajectory of the standard Cartesian MP2RAGE sequence has been modified (1) to obtain a variable density Poisson disk under-sampling distribution along the k -k plane, and (2) to sample the central part of the k-space exactly at TI and TI inversion times. In a prospective study, the accuracy of the T measurements was evaluated on phantoms containing increasing concentrations of gadolinium.