Understanding the Relationship Between Real-Time Thermal Imaging and Thermal Damage Estimate During Magnetic Resonance–Guided Laser Interstitial Thermal Therapy

Abstract BACKGROUND Magnetic resonance-guided laser interstitial thermal therapy is a minimally invasive procedure that produces real-time thermal damage estimates of ablation (TDE). Orthogonal TDE-MRI slices provides an opportunity to mathematically estimate ablation volume. OBJECTIVE To mathematically model TDE volumes and validate with post-24 hours MRI ablation volumes. METHODS Ablations were performed with the Visualase Laser Ablation System (Medtronic). Using ellipsoidal parameters determined for dual-TDEs from orthogonal MRI planes, TDE volumes were calculated by two definite integral methods (A and B) implemented in Matlab (MathWorks). Post 24-hours MRI ablative volumes were measured in OsiriX (Pixmeo) by two-blinded raters and compared to TDE volumes via paired t-tests and Pearson’s correlations. RESULTS Twenty-two ablations for 20 patients with various intracranial pathologies were included. Average TDE volumes calculated with Method A was 3.44 ± 1.96 cm3 and with Method B was 4.83 ± 1.53 cm3. Method A TDE volumes were significantly different than post-24 hours volumes (P < 0.001). Method B TDE volumes were not significantly different than post-24 hours volumes (P = 0.39) and strongly correlated with each other (r = 0.85, R2 = 0.72, P < 0.0001). A total of 8/22 (36%) method A versus 17/22 (77%) method B TDE volumes were within 25% of the post 24-hours ablative volume. CONCLUSION We present the first iteration of a viable mathematical method that integrates dual-plane TDEs to calculate volumes resembling 24 hours post-operative volumes. Future iterations of our algorithm will need to determine additional calculated variables that improve the performance of volumetric calculations.

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A Novel Computational Approach in MATLAB to Characterize Thermal Damage Estimate in Magnetic Resonance-Guided Laser Interstitial Thermal Therapy

Neurosurgery ◽

10.1093/neuros/nyz310_212 ◽

2019 ◽

Vol 66 (Supplement_1) ◽

Author(s):

Allison Liang ◽

Sean Munier ◽

Shabbar F Danish

Keyword(s):

Magnetic Resonance ◽

Thermal Damage ◽

Invasive Procedure ◽

Thermal Therapy ◽

Value Differences ◽

Laser Interstitial Thermal Therapy ◽

Large Sets ◽

The Mean ◽

Mean Differences ◽

Student’S T

Abstract INTRODUCTION Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive procedure that produces real-time thermal damage estimate (TDE) of the ablative area. Measurements of TDE by hand across a full ablation can be time-consuming, and currently, no reliable image analysis exists for measuring TDE dimensions efficiently. METHODS Ablations were performed with the Visualase MRI-Guided Laser Ablation System (Medtronic). Selection criteria included single-laser catheter use and available ablation data in 2 planes. Central TDE lengths and widths postsingle ablation dose were calculated using our developed MATLAB algorithm and compared to manual measurements by 2 raters. The Bland-Altman model and Student's t-tests were used to characterize value differences between the 2 methods. RESULTS A total of 42 TDE images across 21 patients were included. The mean differences in TDE length for rater 1 vs algorithm, rater 2 vs algorithm, and rater 1 vs rater 2 were −0.12 mm (SEM = 0.18), −0.54 mm (SEM = 0.17), and 0.42 mm (SEM = 0.17), respectively. The mean difference in TDE width for rater 1 vs algorithm, rater 2 vs algorithm, and rater 1 vs rater 2 were 0.45 mm (SEM = 0.16), −0.46 mm (SEM = 0.16), and 0.91 mm (SEM = 0.12), respectively. For both lengths and widths, student's t-tests show no significance differences across rater 1 and rater 2 vs algorithm (P > .1) and between raters (P > .05). CONCLUSION Our iterative algorithm provides a reliable method for calculating TDE dimensions. Compared to manual measurements, the differences in TDE length and width are negligible. This computational tool allows for measurement of TDE for large sets of MRgLITT data within minutes.

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Characterization of Magnetic Resonance Thermal Imaging Signal Artifact During Magnetic Resonance Guided Laser-Induced Thermal Therapy

Operative Neurosurgery ◽

10.1093/ons/opaa229 ◽

2020 ◽

Vol 19 (5) ◽

pp. 619-624

Author(s):

Sean M Munier ◽

Allison S Liang ◽

Akshay N Desai ◽

Jose K James ◽

Shabbar F Danish

Keyword(s):

Magnetic Resonance ◽

Patient Outcomes ◽

Thermal Imaging ◽

Thermal Damage ◽

Invasive Procedure ◽

Thermal Therapy ◽

Surgical Indications ◽

Ablation Procedure ◽

Future Studies

Abstract BACKGROUND Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive procedure that utilizes intraoperative magnetic resonance thermal imaging (MRTI) to generate a thermal damage estimate (TDE) of the ablative area. In select cases, the MRTI contains a signal artifact or defect that distorts the ablative region. No study has attempted to characterize this artifact. OBJECTIVE To characterize MRTI signal the artifact in select cases to better understand its potential relevance and impact on the ablation procedure. METHODS All ablations were performed using the Visualase magnetic resonance imaging-guided laser ablation system (Medtronic). Patients were included if the MRTI contained signal artifact that distorted the ablative region during the first thermal dose delivered. Ablation artifact was quantified using MATLAB version R2018a (Mathworks Inc, Natick, Massachusetts). RESULTS A total of 116 patients undergoing MRgLITT for various surgical indications were examined. MRTI artifact was observed in 37.0% of cases overall. Incidence of artifact was greater at higher powers (P < .001) and with longer ablation times (P = .024), though artifact size did not correlate with laser power or ablation duration. CONCLUSION MRTI signal artifact is common during LITT. Higher powers and longer ablation times result in greater incidence of ablation artifact, though artifact size is not correlated with power or duration. Future studies should aim to evaluate effects of artifact on postoperative imaging and, most notably, patient outcomes.

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Effects of Intraoperative Magnetic Resonance Thermal Imaging Signal Artifact During Laser Interstitial Thermal Therapy on Thermal Damage Estimate and Postoperative Magnetic Resonance Imaging Ablative Area Concordance

Operative Neurosurgery ◽

10.1093/ons/opz182 ◽

2019 ◽

Vol 18 (5) ◽

pp. 524-530 ◽

Cited By ~ 1

Author(s):

Sean M Munier ◽

Akshay N Desai ◽

Nitesh V Patel ◽

Shabbar F Danish

Keyword(s):

Magnetic Resonance ◽

Thermal Imaging ◽

Thermal Damage ◽

Cross Sectional Area ◽

Thermal Therapy ◽

Sectional Area ◽

Resonance Imaging ◽

Cross Sectional ◽

Postoperative Magnetic Resonance Imaging ◽

Postoperative Mri

Abstract BACKGROUND Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive procedure that utilizes intraoperative magnetic resonance thermal imaging (MRTI) to generate a thermal damage estimate (TDE) of the ablative area. In select cases, the MRTI contains a signal artifact or defect that distorts the ablative region. No study has considered the impact of this artifact on TDE accuracy. OBJECTIVE To determine the effect of intraoperative MRTI signal artifact on postoperative magnetic resonance imaging (MRI)-predicted ablative area. METHODS All ablations were performed using the Visualase MRI-Guided Laser Ablation System (Medtronic). Patients were grouped based on whether the intraoperative MRTI contained signal artifact that distorted the ablative region. Cross-sectional area of the ablative lesion from the MRI image was measured, and the difference between intraoperative TDE and postoperative MRI cross-sectional area was calculated and compared between groups with and without intraoperative MRTI artifact. RESULTS A total of 91 patients undergoing MRgLITT for various surgical indications were examined. MRTI artifact was observed in 43.9% of cases overall. The mean absolute difference between TDE and the postoperative MRI cross-sectional area was 94.8 mm2 (SEM = 11.6) in the group with intraoperative MRTI artifact and 54.4 mm2 (SEM = 5.5) in the nonartifact group. CONCLUSION MRTI signal artifact is common during LITT. The presence of signal artifact during intraoperative MRTI results in higher variation between intraoperative TDE and postoperative MRI cross-sectional ablative area. In cases in which intraoperative MRTI artifact is observed, there may be a larger degree of variation between observed intraoperative TDE and measured postoperative MRTI ablative area.

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Non-robotized frameless stereotactic magnetic resonance guided laser interstitial thermal therapy for hypothalamic hamartoma: preliminary results of 2 cases and review of the literature

Journal of Neurosurgical Sciences ◽

10.23736/s0390-5616.21.05442-4 ◽

2021 ◽

Author(s):

Giuseppe DI PERNA ◽

Mattia PACETTI ◽

Domenico TORTORA ◽

Lino NOBILI ◽

Armando CAMA ◽

...

Keyword(s):

Magnetic Resonance ◽

Thermal Therapy ◽

Hypothalamic Hamartoma ◽

Review Of The Literature ◽

Preliminary Results ◽

Laser Interstitial Thermal Therapy

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Does the Modified Arrhenius Model Reliably Predict Area of Tissue Ablation After Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Pediatric Lesional Epilepsy?

Operative Neurosurgery ◽

10.1093/ons/opab225 ◽

2021 ◽

Author(s):

Kelsey D Cobourn ◽

Imazul Qadir ◽

Islam Fayed ◽

Hepzibha Alexander ◽

Chima O Oluigbo

Keyword(s):

Magnetic Resonance ◽

Linear Regression ◽

Magnetic Resonance Images ◽

Thermal Therapy ◽

Invasive Technique ◽

Hypothalamic Hamartoma ◽

Arrhenius Model ◽

Laser Interstitial Thermal Therapy ◽

Accuracy And Precision

Abstract BACKGROUND Commercial magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) systems utilize a generalized Arrhenius model to estimate the area of tissue damage based on the power and time of ablation. However, the reliability of these estimates in Vivo remains unclear. OBJECTIVE To determine the accuracy and precision of the thermal damage estimate (TDE) calculated by commercially available MRgLITT systems using the generalized Arrhenius model. METHODS A single-center retrospective review of pediatric patients undergoing MRgLITT for lesional epilepsy was performed. The area of each lesion was measured on both TDE and intraoperative postablation, postcontrast T1 magnetic resonance images using ImageJ. Lesions requiring multiple ablations were excluded. The strength of the correlation between TDE and postlesioning measurements was assessed via linear regression. RESULTS A total of 32 lesions were identified in 19 patients. After exclusion, 13 pairs were available for analysis. Linear regression demonstrated a strong correlation between estimated and actual ablation areas (R2 = .97, P < .00001). The TDE underestimated the area of ablation by an average of 3.92% overall (standard error (SE) = 4.57%), but this varied depending on the type of pathologic tissue involved. TDE accuracy and precision were highest in tubers (n = 3), with average underestimation of 2.33% (SE = 0.33%). TDE underestimated the lesioning of the single hypothalamic hamartoma in our series by 52%. In periventricular nodular heterotopias, TDE overestimated ablation areas by an average of 13% (n = 2). CONCLUSION TDE reliability is variably consistent across tissue types, particularly in smaller or periventricular lesions. Further investigation is needed to understand the accuracy of this emerging minimally invasive technique.

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