Constrained model-predictive thermal dose control for MRI-guided ultrasound thermal treatments (Invited Paper)

2005 ◽  
Author(s):  
Dhiraj Arora ◽  
Trent Perry ◽  
Daniel Cooley ◽  
Junyu Guo ◽  
Rock Hadley ◽  
...  
Keyword(s):  
Thermal Treatments ◽  
Thermal Dose ◽  
Dose Control ◽  
Mri Guided ◽  
Constrained Model

scholarly journals Minimum-Time Thermal Dose Control of Thermal Therapies

2005 ◽  
Vol 52 (2) ◽  
pp. 191-200 ◽  
Author(s):  
D. Arora ◽  
M. Skliar ◽  
R.B. Roemer
Keyword(s):  
Minimum Time ◽  
Thermal Dose ◽  
Thermal Therapies ◽  
Dose Control

scholarly journals Direct thermal dose control of constrained focused ultrasound treatments: phantom andin vivoevaluation

2005 ◽  
Vol 50 (8) ◽  
pp. 1919-1935 ◽  
Author(s):  
Dhiraj Arora ◽  
Daniel Cooley ◽  
Trent Perry ◽  
Mikhail Skliar ◽  
Robert B Roemer
Keyword(s):  
Focused Ultrasound ◽  
Thermal Dose ◽  
Dose Control

scholarly journals Ablation dynamics of subsequent thermal doses delivered to previously heat-damaged tissue during magnetic resonance–guided laser-induced thermal therapy

2019 ◽  
Vol 131 (6) ◽  
pp. 1958-1965 ◽  
Author(s):  
Sean M. Munier ◽  
Eric L. Hargreaves ◽  
Nitesh V. Patel ◽  
Shabbar F. Danish
Keyword(s):  
Magnetic Resonance ◽  
Thermal Damage ◽  
Total Duration ◽  
Ablation Rate ◽  
Thermal Therapy ◽  
Similar Amount ◽  
Thermal Dose ◽  
Surgical Indications ◽  
Maximum Area ◽  
Mri Guided

OBJECTIVEIntraoperative dynamics of magnetic resonance–guided laser-induced thermal therapy (MRgLITT) have been previously characterized for ablations of naive tissue. However, most treatment sessions require the delivery of multiple doses, and little is known about the ablation dynamics when additional doses are applied to heat-damaged tissue. This study investigated the differences in ablation dynamics between naive versus damaged tissue.METHODSThe authors examined 168 ablations from 60 patients across various surgical indications. All ablations were performed using the Visualase MRI-guided laser ablation system (Medtronic), which employs a 980-nm diffusing tip diode laser. Cases with multiple topographically overlapping doses with constant power were selected for this study. Single-dose intraoperative thermal damage was used to calculate ablation rate based on the thermal damage estimate (TDE) of the maximum area of ablation achieved (TDEmax) and the total duration of ablation (tmax). We compared ablation rates of naive undamaged tissue and damaged tissue exposed to subsequent thermal doses following an initial ablation.RESULTSTDEmax was significantly decreased in subsequent ablations compared to the preceding ablation (initial ablation 227.8 ± 17.7 mm2, second ablation 164.1 ± 21.5 mm2, third ablation 124.3 ± 11.2 mm2; p = < 0.001). The ablation rate of subsequent thermal doses delivered to previously damaged tissue was significantly decreased compared to the ablation rate of naive tissue (initial ablation 2.703 mm2/sec; second ablation 1.559 mm2/sec; third ablation 1.237 mm2/sec; fourth ablation 1.076 mm/sec; p = < 0.001). A negative correlation was found between TDEmax and percentage of overlap in a subsequent ablation with previously damaged tissue (r = −0.164; p < 0.02).CONCLUSIONSAblation of previously ablated tissue results in a reduced ablation rate and reduced TDEmax. Additionally, each successive thermal dose in a series of sequential ablations results in a decreased ablation rate relative to that of the preceding ablation. In the absence of a change in power, operators should anticipate a possible reduction in TDE when ablating partially damaged tissue for a similar amount of time compared to the preceding ablation.

scholarly journals Modeling Focused Ultrasound Exposure for the Optimal Control of Thermal Dose Distribution

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
E. Sassaroli ◽  
K. C. P. Li ◽  
B. E. O'Neill
Keyword(s):  
Optimal Control ◽  
Focused Ultrasound ◽  
Thermal Damage ◽  
Average Energy ◽  
Focal Region ◽  
Target Area ◽  
Thermal Treatments ◽  
Thermal Dose ◽  
Delivery Methods ◽  
Ultrasound Exposure

Preclinical studies indicate that focused ultrasound at exposure conditions close to the threshold for thermal damage can increase drug delivery at the focal region. Although these results are promising, the optimal control of temperature still remains a challenge. To address this issue, computer-simulated ultrasound treatments have been performed. When the treatments are delivered without taking into account the cooling effect exerted by the blood flow, the resulting thermal dose is highly variable with regions of thermal damage, regions of underdosage close to the vessels, and areas in between these two extremes. When the power deposition is adjusted so that the peak thermal dose remains close to the threshold for thermal damage, the thermal dose is more uniformly distributed but under-dosage is still visible around the thermally significant vessels. The results of these simulations suggest that, for focused ultrasound, as for other delivery methods, the only way to control temperature is to adjust the average energy deposition to compensate for the presence of thermally significant vessels in the target area. By doing this, we have shown that it is possible to reduce the temperature heterogeneity observed in focused ultrasound thermal treatments.

scholarly journals A thermal dose controller for laser interstitial thermal therapy

2021 ◽  
Author(s):  
Madhu Jain
Keyword(s):  
Target Location ◽  
Treatment Time ◽  
Thermal Therapy ◽  
Invasive Technique ◽  
Thermal Dose ◽  
Laser Interstitial Thermal Therapy ◽  
Cascade Structure ◽  
Dose Control ◽  
Surrounding Healthy Tissue ◽  
Tissue Models

Laser interstitial thermal therapy (LITT) is a minimally invasive technique for destroying localized solid tumors by heating with light. An obstacle to widespread adoption of LITT is the lack of adequate control of heating of surrounding healthy tissue and prevention of tissue and fiber-tip charring. An LITT thermal dose controller was developed to address these issues. The goal of the controller is to deliver prescribed thermal dose at a target location in tissue in a present treatment time. The developed feedback controller has a cascade structure with primary thermal dose control loop continuously generating the reference temperature for the secondary, constrained, model predictive temperature controller. The performance of controller was evaluated in simulated linear and non-linear tissue models and in albumen phantoms. The control system demonstrated the ability to achieve treatment goals across all evaluation models by delivering 240 eq. min dose at 5 mm in various preset treatment times.

scholarly journals Accumulated thermal dose in MRI-guided focused ultrasound for essential tremor: repeated sonications with low focal temperatures

2020 ◽  
Vol 132 (6) ◽  
pp. 1802-1809 ◽  
Author(s):  
Ryan M. Jones ◽  
Shona Kamps ◽  
Yuexi Huang ◽  
Nadia Scantlebury ◽  
Nir Lipsman ◽  
...  
Keyword(s):  
Essential Tremor ◽  
Focused Ultrasound ◽  
Rating Scale ◽  
Lesion Size ◽  
Thermal Dose ◽  
Mr Thermometry ◽  
Dose Accumulation ◽  
Regression Slope ◽  
Tremor Suppression ◽  
Mri Guided

OBJECTIVEThe object of this study was to correlate lesion size with accumulated thermal dose (ATD) in transcranial MRI-guided focused ultrasound (MRgFUS) treatments of essential tremor with focal temperatures limited to 50°C–54°C.METHODSSeventy-five patients with medically refractory essential tremor underwent MRgFUS thalamotomy at the authors’ institution. Intraoperative MR thermometry was performed to measure the induced temperature and thermal dose distributions (proton resonance frequency shift coefficient = −0.00909 ppm/°C). In 19 patients, it was not possible to raise the focal temperature above 54°C because of unfavorable skull characteristics and/or the pain associated with cranial heating. In this patient subset, sonications with focal temperatures between 50°C and 54°C were repeated (5.1 ± 1.5, mean ± standard deviation) to accumulate a sufficient thermal dose for lesion formation. The ATD profile sizes (17, 40, 100, 200, and 240 cumulative equivalent minutes at 43°C [CEM43]) calculated by combining axial MR thermometry data from individual sonications were correlated with the corresponding lesion sizes measured on axial T1-weighted (T1w) and T2-weighted (T2w) MR images acquired 1 day posttreatment. Manual corrections were applied to the MR thermometry data prior to thermal dose accumulation to compensate for off-resonance–induced spatial-shifting artifacts.RESULTSMean lesion sizes measured on T2w MRI (5.0 ± 1.4 mm) were, on average, 28% larger than those measured on T1w MRI (3.9 ± 1.4 mm). The ATD thresholds found to provide the best correlation with lesion sizes measured on T2w and T1w MRI were 100 CEM43 (regression slope = 0.97, R2 = 0.66) and 200 CEM43 (regression slope = 0.98, R2 = 0.89), respectively, consistent with data from a previous study of MRgFUS thalamotomy via repeated sonications at higher focal temperatures (≥ 55°C). Two-way linear mixed-effects analysis revealed that dominant tremor subscores on the Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (CRST) were statistically different from baseline at 3 months and 1 year posttreatment in both low-temperature (50°C–54°C) and high-temperature (≥ 55°C) patient cohorts. No significant fixed effect on the dominant tremor scores was found for the temperature cohort factor.CONCLUSIONSIn transcranial MRgFUS thalamotomy for essential tremor, repeated sonications with focal temperatures between 50°C and 54°C can accumulate a sufficient thermal dose to generate lesions for clinically relevant tremor suppression up to 1 year posttreatment, and the ATD can be used to predict the size of the resulting ablation zones measured on MRI. These data will serve to guide future clinical MRgFUS brain procedures, particularly those in which focal temperatures are limited to below 55°C.

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