Effects of variable power on tissue ablation dynamics during magnetic resonance-guided laser-induced thermal therapy with the Visualase system

Munier, Sean M; Hargreaves, Eric L.; Patel, Nitesh V; Danish, Shabbar F.

doi:10.1080/02656736.2017.1376355

Cited by 15 publications

(14 citation statements)

References 25 publications

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“…The mean energy used for ablation was 2.59 kJ for tubers and 1.70 kJ for FCD. Limited reports have sought to elucidate the thermodynamics of brain tissue in response to the varied energy of ablation, 26,28,29,35 but there is no normative data on the required amount of energy to ablate tissues, so surgeons must instead rely on the thermal damage estimate (TDE) on the Visualase workstation. 8,17,23 Our ablation procedures averaged 222.75 minutes (range 179-252 minutes).…”

Section: Discussionmentioning

confidence: 99%

Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

Cobourn¹,

Fayed²,

Keating³

et al. 2018

Neurosurgical Focus

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OBJECTIVEStereoelectroencephalography (sEEG) and MR-guided laser interstitial thermal therapy (MRgLITT) have both emerged as minimally invasive alternatives to open surgery for the localization and treatment of medically refractory lesional epilepsy. Although some data are available about the use of these procedures individually, reports are almost nonexistent on their use in conjunction. The authors’ aim was to report early outcomes regarding efficacy and safety of sEEG followed by MRgLITT for localization and ablation of seizure foci in the pediatric population with medically refractory lesional epilepsy.METHODSA single-center retrospective review of pediatric patients who underwent sEEG followed by MRgLITT procedures was performed. Demographic, intraoperative, and outcome data were compiled and analyzed.RESULTSFour pediatric patients with 9 total lesions underwent sEEG followed by MRgLITT procedures between January and September 2017. The mean age at surgery was 10.75 (range 2–21) years. Two patients had tuberous sclerosis and 2 had focal cortical dysplasia. Methods of stereotaxy consisted of BrainLab VarioGuide and ROSA robotic guidance, with successful localization of seizure foci in all cases. The sEEG procedure length averaged 153 (range 67–235) minutes, with a mean of 6 (range 4–8) electrodes and 56 (range 18–84) contacts per patient. The MRgLITT procedure length averaged 223 (range 179–252) minutes. The mean duration of monitoring was 6 (range 4–8) days, and the mean total hospital stay was 8 (range 5–11) days. Over a mean follow-up duration of 9.3 (range 5.1–16) months, 3 patients were seizure free (Engel class I, 75%), and 1 patient saw significant improvement in seizure frequency (Engel class II, 25%). There were no complications.CONCLUSIONSThese early data demonstrate that sEEG followed by MRgLITT can be used safely and effectively to localize and ablate epileptogenic foci in a minimally invasive paradigm for treatment of medically refractory lesional epilepsy in pediatric populations. Continued collection of data with extended follow-up is needed.

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Section: Discussionmentioning

confidence: 99%

Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

Cobourn¹,

Fayed²,

Keating³

et al. 2018

Neurosurgical Focus

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“…Intraoperatively, there are two options at the surgeon's disposal for expansion of the ablative area, increasing laser power and retraction of the laser catheter along the applicator insertion trajectory. 21 The laser catheter utilized by the Visualase system disperses heat in all directions in an ellipsoidal fashion. 19 Previous studies have shown that in cases in which a second thermal dose at higher power is applied to a target without repositioning the laser following an initial lower power dose, the TDE expands to a larger area with an increased ablation rate.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies have shown that laser power (watts) contributes to the overall ablation rate. 21 Although laser power was held constant for successive ablations within each case, it varied between cases. It was further hypothesized that a higher percentage of area overlap between ablations may have slowed subsequent ablations.…”

Section: Fig 2 Example Of a Patient With A Left Temporal Metastaticmentioning

confidence: 99%

“…30 Previously, the temporal profile of neural tissue damage via laser energy has been characterized through assessment of the relationship between thermal damage estimate (TDE) and ablation duration (t max ), finding that expansion of the ablation area can follow either logistic or negative exponential growth as it approaches a finite maximum (TDE max ). 21,30 A second study investigated the effects of variable laser power on ablation duration and ablation area, finding that the degree of power can both hasten and enlarge a given ablation. 21 However, it is critical to note that most treatment sessions require the delivery of multiple thermal doses from the laser catheter to achieve full target ablation, and little is known about the ablation dynamics when additional doses are applied to previously heat-damaged tissue.…”

mentioning

confidence: 99%

“…21,30 A second study investigated the effects of variable laser power on ablation duration and ablation area, finding that the degree of power can both hasten and enlarge a given ablation. 21 However, it is critical to note that most treatment sessions require the delivery of multiple thermal doses from the laser catheter to achieve full target ablation, and little is known about the ablation dynamics when additional doses are applied to previously heat-damaged tissue. In cases with large or irregularly shaped targets, the operator can retract the laser catheter along the longitudinal axis of the lesion between ablations and apply a second thermal dose to expand the ablation area.…”

mentioning

confidence: 99%

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

Munier¹,

Hargreaves²,

Patel³

et al. 2019

Journal of Neurosurgery

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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.

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Proton Resonance Frequency Shift Thermometry: A Review of Modern Clinical Practices

Blackwell

Kraśny

O’Brien

et al. 2020

Magnetic Resonance Imaging

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Magnetic resonance imaging (MRI) has become a popular modality in guiding minimally invasive thermal therapies, due to its advanced, nonionizing, imaging capabilities and its ability to record changes in temperature. A variety of MR thermometry techniques have been developed over the years, and proton resonance frequency (PRF) shift thermometry is the current clinical gold standard to treat a variety of cancers. It is used extensively to guide hyperthermic thermal ablation techniques such as high-intensity focused ultrasound (HIFU) and laser-induced thermal therapy (LITT). Essential attributes of PRF shift thermometry include excellent linearity with temperature, good sensitivity, and independence from tissue type. This noninvasive temperature mapping method gives accurate quantitative measures of the temperature evolution inside biological tissues. In this review, the current status and new developments in the fields of MR-guided HIFU and LITT are presented with an emphasis on breast, prostate, bone, uterine, and brain treatments. Level of Evidence: 5 Technical Efficacy Stage: 3

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Effects of variable power on tissue ablation dynamics during magnetic resonance-guided laser-induced thermal therapy with the Visualase system

Abstract: Increased power results in a larger TDE and an increased ablation rate. In cases where an initial thermal dose does not fully ablate the target lesion, a second ablation at higher power can increase the area of ablation with an increased ablation rate.

Cited by 15 publications

References 25 publications

Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

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

Proton Resonance Frequency Shift Thermometry: A Review of Modern Clinical Practices

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