Evaluation of the contrast between tissues and thermal lesions in rabbit in vivo produced by high intensity focused ultrasound using fast spin echo MRI sequences

Venediktos Hadjisavvas,Michalis Komodromos,Nikos Mylonas,Christakis Damianou,Kleanthis Ioannides

doi:10.4236/jbise.2011.41007

Venediktos Hadjisavvas, Michalis Komodromos + Show 3 more

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https://doi.org/10.4236/jbise.2011.41007

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Abstract

In this paper the goal was to measure the contrast to noise ratio (CNR) of fast spin echo (FSE) magnetic resonance imaging (MRI) sequences in detecting thermal lesions created by high intensity focused ul-trasound (HIFU) in rabbit kidney, liver, heart, and brain and lamb pancreas. A spherically focused transducer was used which is navigated inside MRI by a custom made positioning device. A simple simu-lation model was developed which predicts the CNR for the two FSE MRI sequences. The maximum con-trast measured with T1-W FSE ranges from 10 to 25. For all 5 tissues of interest if one uses TR between 400 and 500 ms the contrast is maximized. The T1 and T2 value of lesion depends strongly on the host tissue and is always lower than the host tissue. The greater the difference in T1 value, the greater the CNR. The simulated model for predicting the CNR was proven successful. The CNR measured with T2-W FSE varies between 12 and 15 for all 5 tissues. With T2-W FSE if one uses TE between 40 and 50 ms, the contrast is maximized.

Highlights

In this paper the goal was to measure the contrast to noise ratio (CNR) of fast spin echo (FSE) magnetic resonance imaging (MRI) sequences in detecting thermal lesions created by high intensity focused ultrasound (HIFU) in rabbit kidney, liver, heart, and brain and lamb pancreas
The transducer used for the kidney, liver, heart and pancreas ablation operates with frequency of 4 MHz, and the transducer for brain ablation operates at 1 MHz
In this paper the goal was to measure the CNR of FSE MRI sequences in detecting thermal lesions created by HIFU in kidney, liver, heart, and brain of rabbit

Summary

Introduction

In this paper the goal was to measure the contrast to noise ratio (CNR) between thermal lesions created by high intensity focused ultrasound (HIFU) and tissues in. We have chosen to explore kidney, liver, heart, brain and pancreas because there is currently a lot of ongoing research either in animal models or in humans for these 5 tissues. There is a lot of work done so far in the area of kidney ablation with HIFU. For example Watkin et al 1997 [1] developed a large animal model and proved the feasibility of HIFU to create thermal lesion. Roberts et al have performed ablations in the normal rabbit kidneys and suggested that the mechanical effects of ultrasound can be used to homogenize tissue [2]

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