Delineation of Noise Signals From MRI Measured Temperature Rise During HIFU Ablation Procedure

2011 ◽  
Author(s):  
Subhashish Dasgupta ◽  
Seyed Ahmed Dibaji ◽  
Janaka Wansapura ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Temperature Rise ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Heat Equations ◽  
Intensity Level ◽  
Measured Temperature ◽  
Mr Thermometry ◽  
Porcine Liver ◽  
Heating Phase ◽  
Set Up

A relatively recent and non invasive method for characterizing thermal fields generated by high intensity focused ultrasound (HIFU) transducers is Magnetic Resonance (MR) Thermometry method. However, noise signals generated by external RF sources infiltrate the scanner orifice and limit its ability to measure temperature rise during the heating or ablation phase. In this study, MRI monitored HIFU ablations are performed on freshly excised porcine liver samples, at varying sonication times, 20, 30 and 40 s at a constant acoustic intensity level of 1244 W/cm2. Temperature rise during the procedure is measured using Proton Resonant Frequency MR thermometry. Preliminary experiments without an adequate noise filter, failed to record temperature rise during the heating phase. A low pass R-C filter circuit is subsequently incorporated into the experimental set up to prevent infiltration of noise signals in the MRI orifice. This modified RC filter enables measurement of temperature rise during the heating phase followed by temperature decay during cooling. The measured data is within 12% agreement with the temperature rise computed by solving the acoustic and heat equations.

Reduction of Noise From MR Thermometry Measurements During HIFU Characterization Procedures

2011 ◽  
Vol 2 (2) ◽  
Author(s):  
Subhashish Dasgupta ◽  
Prasenjeet Das ◽  
Janaka Wansapura ◽  
Prasanna Hariharan ◽  
Ron Pratt ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Temperature Rise ◽  
Slow Rate ◽  
High Intensity Focused Ultrasound ◽  
Heat Equations ◽  
Intensity Level ◽  
Mr Thermometry ◽  
Porcine Liver ◽  
Temperature Decay ◽  
Heating Phase

Magnetic resonance (MR) thermometry is a valuable method for characterizing thermal fields generated by high intensity focused ultrasound (HIFU) transducers in tissue phantoms and excised tissues. However, infiltration of noise signals generated by external rf sources into the scanner orifice limits the ability of the scanner to measure temperature rise during the heating or ablation phase. In this study, magnetic resonance interferometry (MRI) monitored HIFU ablations are performed on freshly excised porcine liver samples, at varying sonication times, 20 s, 30 s, and 40 s at a constant acoustic intensity level of 1244 W/cm2. Temperature throughout the procedure was measured using proton resonant frequency MR thermometry. Without filtering, reliable temperature measurements during the heating phase could not be obtained since temperature maps appeared blurred and analysis was impossible. Also, measurements acquired during the cooling phase decayed manifested an unrealistically slow rate of temperature decay. This abnormally slow rate was confirmed with computational results. A low-pass RC filter circuit was subsequently incorporated into the experimental setup to prevent infiltration of noise signals in the MRI orifice. This modified RC filter circuit allowed noninvasive measurement of the HIFU induced temperature rise during the heating phase followed by temperature decay during cooling. The measured data were within 13% agreement with the temperature rise computed by solving the acoustic and heat equations.

Reduction in Beam Positioning Error During HIFU Ablation Studies in Tissue Phantoms

2010 ◽  
Author(s):  
Subhashish Dasgupta ◽  
Prasanna Hariharan ◽  
Matthew R. Myers ◽  
Rupak K. Banerjee
Keyword(s):  
Blood Flow ◽  
Iterative Method ◽  
Temperature Rise ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Measured Temperature ◽  
Positioning Error ◽  
Tissue Phantoms ◽  
Order Of Magnitude ◽  
Source Of Error

Measurements of high intensity focused ultrasound (HIFU) induced temperature rise using thermocouples in tissue phantoms are subject to several types of error which must be accounted for in order to accurately assess the thermal field and predict the outcome of clinical procedures. Thermocouple artifacts due to viscous heating is one source of error. A second source of error involves displacement of the beam relative to the targeted thermocouple junction, due to the difficulty in precisely positioning the very narrow beam. This paper presents an iterative method for removing inaccuracies due to positioning error from the measured temperature data. The refined data is used to quantify the effect of blood flow through large vessels on the efficacy of HIFU procedures. It was determined that blood flow cooling effect causes an order of magnitude decrease in thermal dose at the target within 2 mm of the blood vessel, potentially resulting in incomplete ablation of the tumor. The technique also reveals that thermocouple artifacts exist in significant proportions from about 0.5 to 2.2 times the computed temperature rise in the initial few seconds. The iterative method can aid in clinical procedure planning, especially in predicting the proper HIFU intensity and duration for complete destruction of tumors.

Robotic Platform for High-Intensity Focused Ultrasound Surgery Under Ultrasound Tracking: The FUTURA Platform

2017 ◽  
Vol 02 (03) ◽  
pp. 1740010 ◽  
Author(s):  
Selene Tognarelli ◽  
Gastone Ciuti ◽  
Alessandro Diodato ◽  
Andrea Cafarelli ◽  
Arianna Menciassi
Keyword(s):  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Ultrasound Surgery ◽  
Ultrasound Monitoring ◽  
Focused Ultrasound Surgery ◽  
Set Up ◽  
Framework Programme Project ◽  
Static Conditions ◽  
Ultrasound Tracking

Focused Ultrasound Therapy Using Robotic Approaches (FUTURA) is a European seventh research framework programme project aimed at creating an innovative platform for Focused Ultrasound Surgery (FUS). Merging robotics together with noninvasive ultrasound monitoring and therapy has the goal to improve flexibility, precision and accuracy of the intervention, thus enabling a large use of FUS for the treatment of different pathologies. The FUTURA platform, based on FUS therapy under US tracking, has been set up with the first clinical target of kidney cancer treatment. Experiments for assessing the accuracy of the FUS delivery with the FUTURA platform have been carried out under in vitro static conditions and presented here as preliminary outcomes of this study.

scholarly journals Predicting final lesion characteristics during MR-guided focused ultrasound pallidotomy for treatment of Parkinson’s disease

2020 ◽  
pp. 1-8 ◽  
Author(s):  
Timothy R. Miller ◽  
Sijia Guo ◽  
Elias R. Melhem ◽  
Howard M. Eisenberg ◽  
Jiachen Zhuo ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Temperature Rise ◽  
Focused Ultrasound ◽  
Threshold Model ◽  
Average Energy ◽  
Lesion Size ◽  
Temperature Threshold ◽  
Treatment Efficiency ◽  
Mr Thermometry

OBJECTIVEMagnetic resonance–guided focused ultrasound (MRgFUS) ablation of the globus pallidus interna (GPi) is being investigated for the treatment of advanced Parkinson’s disease symptoms. However, GPi lesioning presents unique challenges due to the off-midline location of the target. Furthermore, it remains uncertain whether intraprocedural MR thermometry data can predict final lesion characteristics.METHODSThe authors first performed temperature simulations of GPi pallidotomy and compared the results with those of actual cases and the results of ventral intermediate nucleus (VIM) thalamotomy performed for essential tremor treatment. Next, thermometry data from 13 MRgFUS pallidotomy procedures performed at their institution were analyzed using 46°C, 48°C, 50°C, and 52°C temperature thresholds. The resulting thermal models were compared with resulting GPi lesions noted on postprocedure days 1 and 30. Finally, the treatment efficiency (energy per temperature rise) of pallidotomy was evaluated.RESULTSThe authors’ modeled acoustic intensity maps correctly demonstrate the elongated, ellipsoid lesions noted during GPi pallidotomy. In treated patients, the 48°C temperature threshold maps most accurately predicted postprocedure day 1 lesion size, while no correlation was found for day 30 lesions. The average energy/temperature rise of pallidotomy was higher (612 J/°C) than what had been noted for VIM thalamotomy and varied with the patients’ skull density ratios (SDRs).CONCLUSIONSThe authors’ acoustic simulations accurately depicted the characteristics of thermal lesions encountered following MRgFUS pallidotomy. MR thermometry data can predict postprocedure day 1 GPi lesion characteristics using a 48°C threshold model. Finally, the lower treatment efficiency of pallidotomy may make GPi lesioning challenging in patients with a low SDR.

scholarly journals A fast MR-thermometry method for quantitative assessment of temperature increase near an implanted wire

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0250636
Author(s):  
Marylène Delcey ◽  
Pierre Bour ◽  
Valéry Ozenne ◽  
Wadie Ben Hassen ◽  
Bruno Quesson
Keyword(s):  
Human Brain ◽  
Temperature Rise ◽  
Temperature Increase ◽  
Fiber Optic ◽  
Calibration Data ◽  
Measured Temperature ◽  
Pacemaker Lead ◽  
Mr Thermometry ◽  
Data Set ◽  
Calibration Data Set

Purpose To propose a MR-thermometry method and associated data processing technique to predict the maximal RF-induced temperature increase near an implanted wire for any other MRI sequence. Methods A dynamic single shot echo planar imaging sequence was implemented that interleaves acquisition of several slices every second and an energy deposition module with adjustable parameters. Temperature images were processed in real time and compared to invasive fiber-optic measurements to assess accuracy of the method. The standard deviation of temperature was measured in gel and in vivo in the human brain of a volunteer. Temperature increases were measured for different RF exposure levels in a phantom containing an inserted wire and then a MR-conditional pacemaker lead. These calibration data set were fitted to a semi-empirical model allowing estimation of temperature increase of other acquisition sequences. Results The precision of the measurement obtained after filtering with a 1.6x1.6 mm2 in plane resolution was 0.2°C in gel, as well as in the human brain. A high correspondence was observed with invasive temperature measurements during RF-induced heating (0.5°C RMSE for a 11.5°C temperature increase). Temperature rises of 32.4°C and 6.5°C were reached at the tip of a wire and of a pacemaker lead, respectively. After successful fitting of temperature curves of the calibration data set, temperature rise predicted by the model was in good agreement (around 5% difference) with measured temperature by a fiber optic probe, for three other MRI sequences. Conclusion This method proposes a rapid and reliable quantification of the temperature rise near an implanted wire. Calibration data set and resulting fitting coefficients can be used to estimate temperature increase for any MRI sequence as function of its power and duration.

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