A software platform controlling an MRI guided focused ultrasound system

A software platform written in MATLAB has been developed in order to control an MRI guided Focused ultrasound system. The software serves 7 main tasks: a) MRI imaging, b) transducer movement (the user may move the robot manually or automatically by specifying the pattern, the step and the number of steps), c) messaging (starting time, treatment time left etc), d) Camera control, e) Patient data (age, weight, etc), f) Controlling the parameters and activation of a signal generator and g) Temperature measurement. The motors are activated using a 24 V DC supply which is incorporate in an enclosure that includes the drivers of the motors. The motors are interfaced using a USB card (National instruments NI-6251). Feedback is provided using a timer card. The software controls a positioning device which can be used to treat patients with brain, liver, kidney, thyroid, pancreas and prostate cancer. © 2012 IEEE

Treatment of brain cancer and ischaemic stroke utilising High Intensity Focus Ultrasound (HIFU) guide with MRI

In this thesis high intensity focused ultrasound (HIFU) is utilized for cancer treatment (thermal mode) and treatment of ischaemic stroke (mechanical mode). These two applications were investigated in vitro and in vivo models. MRI was utilized to monitor the lesions created by HIFU either in thermal or cavitation mode in freshly excised lamb brain tissue in vitro, and in rabbit brain in vivo. Additionally, MRI was used to monitor lesions deep in tissue for both in vitro and in vivo exposures. All three MRI sequences used (T1-W FSE, T2-W FSE and FLAIR) were able to detect lesions. Both thermal and bubbly lesions were best monitored using T1-W FSE with excellent contrast, proving the potential of HIFU to treat reliably tumours in the brain. A HIFU system was also used to assist thrombolysis in cooperation with a thrombolytic drug such as recombinant tissue plasminogen activator (rt-PA) in vitro and in vivo. It was shown that higher intensity results to higher volume of dissolved clot, but there is a limit of the intensity to be used in order to avoid heating of the clot and the surrounding tissue. The goal in this study was to achieve temperature elevation not exceeding 1ºC (called safe temperature). It was found that the larger the beam area the larger the dissolved clot volume. Also, the lower the frequency, the larger the volume of the dissolved clot. The results reported herein point to the use of frequency around 0.5 MHz and pulsing to optimize thrombolysis and skull penetration and at the same time avoiding unwanted heating. Finally, an Acrylonitrile Butadiene Styrene (ABS) phantom skull model was developed in order to evaluate the propagation of ultrasound using a single element transducer. The skull model was appropriately designed so that it has the same attenuation as a human skull. It was demonstrated that using a frequency of 0.5 MHz versus 1 MHz, ultrasound propagation through the phantom skull was higher. Therefore, higher frequency has poor skull penetration and a small beam size at the focus, while low frequencies have better skull penetration but with the risk of reaching the unpredictable effect of cavitation. The developed system has proven to successfully create large lesions in the brain and at the same time, these lesions are successfully monitored with excellent contrast using MRI (T1-W FSE) enabling the accurate determination of the margins of these lesions. The results reported in this study point to the use of frequency around 0.5 MHz and pulsing to optimize thrombolysis and skull penetration and at the same time avoiding unwanted heating. For treating tumours located deep in the brain and for dissolving thrombus causing an acute ischaemic stroke, further extensive clinical studies will be needed before this technology is applied to humans

Design of a 2D MRI compatible robot for performing prostate cancer treatment using therapeutic ultrasound

Therapeutic ultrasound is a promising treatment method for many common cancers, including prostate cancer. Magnetic resonance image (MRI) guidance of therapeutic ultrasound permits targeting and monitoring of therapy. In this thesis a prototype MRI compatible positioning device for the treatment of prostate cancer using therapeutic ultrasound is presented. The accuracy, MRI compatibility and functionality of the positioning device was evaluated in in vitro experiments (using gel phantoms and in vitro). The MRI was used as the imaging guidance technique. The proposed device incorporates a portable electronic system and operates in two PC controlled stages, linear and angular (X - Θ) and one manual driven stage Z (height of the probe). The device is small and portable and can be placed on the patient’s table to any commercial MRI scanner. The proposed device was tested on two clinical MRI scanners of different manufacturers. Additionally, in this thesis a software that controls an MRI guided focus ultrasound system is presented. The software was written in C sharp and consists of the following options: a) connection with DAQ device, b) tab that controls 2D device, c) tab that controls 3D device, d) tab that controls ultrasound protocol and e) operation command history list, g) MRI compatible camera, h) open and control the DICOM images captured from the MRI scanner during the therapy, i) temperature reading of the HIFU focal point. The proposed positioning device offers approximately 20μm accuracy on linear and angular stages. It incorporates MRI compatible optical encoders as mechanical motion feedback. The accuracy measurements were taken using a digital calibre. The positioning device has range of 111mm in linear stage, ±90o on angular stage and 50mm on Z stage. The design was based on measurements that were taken by a 100 patients. The MRI compatibility and motion accuracy images were taken by scanning gel phantoms using T2W FSE on 1.5T and 3T MRI scanner