CurrentAetnaPolicy 0781

Interstitial Laser Therapy

Aetna's clinical policy bulletin on the medical necessity and experimental/investigational indications for interstitial laser therapy (ILT), including covered CPT/ICD codes and background evidence; applies to Aetna members and providers.

Policy Summary

PayerAetna

PolicyInterstitial Laser Therapy

Policy CodePolicy 0781

Change TypeNo material changes

Effective Date04/10/2009

Next Review Date08/22/2024

Key ActionDocument indication, prior therapies, lesion characteristics, and multidisciplinary rationale when submitting prior authorization.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

0781Aetna clinical policy identifier

1 dayTypical LOS after SLAH

75.8%Local control (Rao et al)

>20Experimental indications

61735/61736/61737Covered CPT codes

Class I

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FDA recall classification (NeuroBlate)

Coverage Criteria and Indications

Medically Necessary Indications

Aetna considers interstitial laser therapy medically necessary when one of the following is met:

Medically necessary indications: 1) Refractory epilepsy when criteria per CPB 0394 - Epilepsy Surgery are met; OR 2) Persons with recurrent brain metastases, recurrent glioblastoma, or radiation necrosis who are poor surgical candidates for craniotomy and resection (open surgery presents prohibitive surgical risk or lesion is surgically inaccessible).

Follow related CPB 0394 for epilepsy surgery criteria.

Experimental and Investigational

Aetna considers ILT experimental and investigational for the following (partial list) because of insufficient evidence of effectiveness:

Experimental/Investigational indications: Adrenal metastases; brain tumors (including astrocytoma, intra‑cranial meningiomas, pineal region glioma, posterior fossa tumors, thalamic tumors) excluding recurrent glioblastoma or recurrent brain tumors in poor surgical candidates; breast tumors (benign or malignant); cerebral cavernous malformation; chronic intractable non‑malignant pain; cutaneous melanoma; epileptogenic periventricular nodular heterotopia; extra‑axial meningiomas; fetal hydrops; fetal sacro‑coccygeal teratomas; insular tumors (not including recurrent glioblastoma in poor surgical candidates); liver metastases; lung cancer and lung metastases; pancreatic cancer; placental chorioangiomas; prostate cancer; spinal cord compression and spinal instability; spinal metastasis; thyroid nodules; tremor disorders.

List is not exhaustive; see full policy for additional excluded indications.

Coverage considerations for LITT

Coverage considerations described in the evidence summarize that LITT may be considered for select patients when:

Eligibility features from reported series: Patient has symptomatic recurrent intracranial metastatic lesion or biopsy‑confirmed radiation necrosis after prior stereotactic radiosurgery, or is not a candidate for open resection; lesion is amenable to stereotactic probe placement; documented prior therapies and functional status (e.g., KPS ≥70 in some series).

Derived from Rao et al, Torres‑Reveron, Rahmathulla, Hawasli series

Potential expected benefits: Reported benefits include improved local control, reduction in edema and steroid dependence, short hospital stay (often 24–48 hours), and symptomatic relief; spinal LITT reports decreased epidural compression and improvement in pain/QOL.

Outcomes are preliminary from small case series and single‑arm studies

Evidence and documentation requirements: Documentation should demonstrate why standard therapies are not suitable or have failed; include imaging and biopsy results when performed; plan for MR thermometry monitoring and follow‑up MRI to assess local control; counsel patient that evidence is limited and long‑term outcomes uncertain.

General coverage criteria for MRgLITT / sLITT

Covered when ALL of the following are met (evidence‑based candidate features summarized from cited series):

Primary criteria: 1) Indication is one of: compressive spinal metastasis (particularly thoracic), intracranial tumor/radiation necrosis, or well‑localized drug‑resistant focal epilepsy (e.g., mesial temporal lobe epilepsy) with concordant pre‑surgical evaluation; 2) Patient has been evaluated by an appropriate multidisciplinary team and is deemed a candidate for minimally invasive ablation (not a candidate for or declines open surgery); 3) Imaging demonstrates lesion size and location amenable to safe probe trajectory and ablation (expert series cite smaller lesions and depth/location considerations for candidacy); 4) Plan includes real‑time MR thermometry monitoring and post‑procedure follow‑up and adjuvant therapy as indicated (e.g., SSRS after sLITT).

Derived from clinical series and systematic reviews; evidence limited to case series and small cohorts.

Epilepsy (MTLE) indications and evidence

Evidence‑based scenarios where LITT has been reported to be used:

Epilepsy - mesial temporal lobe (MTLE): MRgLITT/SLAH has been used for medically refractory MTLE with mesial temporal sclerosis (MTS) or SEEG‑confirmed mesial temporal onset. Seizure‑freedom has been reported in a portion of patients (rates vary by series and MTS status), with shorter hospital stays and lower invasiveness compared with open resection. Outcomes and neuropsychological effects vary; efficacy appears greater in patients with MTS in several series.clinical selection based on imaging/SEEG

Consider individualized assessment and discussion of trade‑offs between invasiveness and expected seizure outcomes.

Focal cortical dysplasia

Focal cortical dysplasia: LITT may enable stereotactic ablation of deep or surgically inaccessible focal cortical dysplasias; complete ablation may not be feasible in all cases and staged LITT followed by open resection has been described.case‑by‑case surgical feasibility

Clinical utility requires further study.

Tumors, metastases, and radiation necrosis

Intracranial tumors and radiation necrosis

Recurrent high‑grade glioma / difficult‑to‑access tumors: LITT has been used as salvage or adjunct therapy for recurrent high‑grade gliomas and difficult‑to‑access malignant tumors; some series report permanent neurologic deficits and vascular injuries. Evidence is insufficient to define a standard role and patient selection is critical.selected patients with unresectable or recurrent disease

Outcomes variable; further studies needed.

Radiation necrosis and recurrent metastases: LITT has been used to manage radiosurgery‑resistant metastases and symptomatic radiation necrosis, with series reporting potential effectiveness including steroid weaning and radiographic improvement, though randomized evidence is lacking.case selection by multidisciplinary team

Prospective randomized trials needed.

Adjunctive BBB disruption

Peri‑tumoral blood‑brain barrier (BBB) modulation

BBB disruption window: Pilot data indicate MRgLITT induces transient peri‑tumoral BBB disruption with peak permeability within 1–2 weeks after ablation and resolution by 4–6 weeks, potentially creating a therapeutic window for enhanced delivery of systemically administered agents.timing window 1–6 weeks post‑ablation

Preliminary pilot data; clinical benefit unproven.

Described clinical indications, selection factors, and evidence limitations

Indications and considerations described in the literature excerpts:

Situations where LITT is described as an option: LITT may be considered when conventional surgery or radiation is not feasible or has been exhausted, including radiosurgery‑resistant brain metastases, radiation necrosis, surgically inaccessible or deep‑seated gliomas (e.g., thalamic tumors), select meningiomas with regrowth, and to transiently enhance peri‑tumoral BBB permeability for drug delivery.

Descriptive summaries from narrative and registry data; not a payer coverage determination.

Factors associated with better selection or outcomes: Smaller pre‑treatment tumor volume, more complete ablation (greater TDT‑line coverage), lesions generally ≤ approximately 6 cc in some analyses, and receipt of systemic therapy after LITT have been associated with longer local control in retrospective studies.

Derived from retrospective analyses.

Evidence limitations: Available evidence consists mainly of retrospective series, single‑center studies, and registries with heterogeneous inclusion criteria and risk of bias; randomized controlled trials and long‑term comparative data are lacking.

Reported clinical applications

Indications and contexts reported in literature and guidelines:

Reported clinical applications: Recurrent or deep‑seated gliomas and brain metastases (especially after prior irradiation), radiation necrosis, symptomatic peri‑tumoral edema after radiosurgery, select meningiomas with regrowth when surgery/radiation are exhausted, hypothalamic hamartoma–related epilepsy, and spinal epidural metastatic compression (sLITT).

Descriptive; NCCN notes LITT may be considered for patients not surgical candidates (Category 2B).

Outcomes and safety

Reported outcomes and safety signals

Reported outcomes and safety: Series report short hospital length‑of‑stay, variable perioperative morbidity and complication rates, occasional permanent neurologic deficits and vascular injuries, and generally favorable short‑term symptomatic responses; pooled analyses report substantial heterogeneity with pooled adverse event rates reported in systematic reviews. Randomized trial data are lacking.

Prospective randomized trials are needed per authors.

Evidence-based coverage considerations

Evidence and indication summaries from observational studies and systematic reviews

General evidence characterization: Evidence consists primarily of small case series, retrospective cohorts, and systematic reviews/meta‑analyses with heterogeneous inclusion criteria and substantial risk of bias; randomized controlled trial data comparing LITT to standard of care (e.g., SRS or craniotomy) are lacking.

Quality of evidence generally low; authors call for larger prospective, randomized or well‑designed comparative studies.

Reported applications in reviews: Applications reported across reviews include: MRI‑guided LITT for spinal metastases and spinal cord compression (feasibility/navigation), LITT for brain metastases including radiation necrosis/PEIR, salvage therapy for recurrent tumors after radiosurgery, newly diagnosed and recurrent glioblastoma (evidence limited), extra‑axial meningiomas, posterior fossa tumors, and palliative or difficult‑to‑access lesions.

Indications derived from observational literature and systematic reviews; not definitive coverage endorsements.

Safety and efficacy uncertainty: Systematic reviews report pooled procedure‑related adverse event rates and neurologic deficit rates with wide variability; for many indications (e.g., newly diagnosed GBM, comparison to SRS for metastases), evidence is insufficient to draw firm conclusions about comparative effectiveness.

The policy lists specific procedure and diagnosis codes relevant to coverage determinations. Covered CPT codes when selection criteria are met include 61735, 61736, and 61737. A CPT code explicitly noted as not covered for CPB‑listed indications is 0673T. Relevant ICD‑10 diagnosis codes covered if selection criteria are met include cerebral primary tumor codes C71.0–C71.3–C71.9 (with exceptions for insular and pineal region tumors as noted), secondary malignant neoplasm of brain C79.31, focal intractable epilepsy codes (for example, ranges beginning with G40.011–G40.019), and radiation‑related codes such as T66.XXX+. Several ICD‑10 categories (e.g., malignant neoplasms of pancreas C25.0–C25.9, lung C34.00–C34.92, cutaneous melanoma C43.0–C43.8, and breast C50.011–C50.929) are listed as not covered for the indications specified in the CPB.

The policy identifies use of ILT for many non‑brain tumor sites and other indications as experimental/investigational due to insufficient evidence. Examples called out include breast tumors, liver metastases, lung cancer and lung metastases, pancreatic cancer, thyroid nodules, and various pediatric and other tumor indications; the brief and source emphasize that effectiveness for these non‑brain tumor sites is not established.

The document cautions that LITT should not be adopted routinely as a replacement for established open resection when comparative evidence is lacking. Assessments noted the absence of controlled comparative data versus craniotomy and the unclear efficacy of LITT as a routine substitute for open surgical resection.

Multiple systematic reviews and series characterize the evidence as limited and heterogeneous; therefore there is insufficient high‑quality evidence to broadly recommend LITT as standard therapy across many tumor types. Authors report variable progression and survival outcomes and call for larger prospective, randomized or well‑designed comparative studies before expanding routine use.

Within the cited excerpts there are no explicit patient‑level absolute exclusion criteria or contraindications specified. Reviews and technology assessments instead emphasize that patient selection should be individualized and guided by available evidence, multidisciplinary evaluation, and procedural feasibility.

The literature frames LITT largely as a salvage or alternative option after standard interventions are exhausted or when patients are poor candidates for open surgery. The policy highlights use for recurrent brain metastases, recurrent glioblastoma, or radiation necrosis in patients who are poor surgical candidates, and notes case series where LITT was applied after prior stereotactic radiosurgery or when craniotomy presented prohibitive risk.

No procedural exclusions are explicitly listed in these excerpts. Guideline sources cited (for example, NCCN and UpToDate reviews referenced in the background) generally do not list LITT as a standard therapeutic option for many CNS indications, reflecting that LITT is investigational or evolving rather than an explicitly excluded procedure.

Clinical guideline reviews for cutaneous melanoma and other non‑CNS malignancy management do not include LITT as a standard treatment option. The policy and cited UpToDate/NCCN sources note that LITT is not mentioned as a management or therapeutic option for cutaneous melanoma in current guideline summaries.

The CPB states that ILT used for the listed experimental and investigational indications is considered not medically necessary because evidence of clinical effectiveness is insufficient. The policy identifies a broad, non‑exhaustive list of conditions (e.g., many non‑brain tumors, specific pediatric and rare indications) for which ILT is regarded as investigational and therefore not medically necessary.

Technology assessments and systematic reviews summarized in the policy describe the available evidence as small, heterogeneous, and of low quality; authors characterize the evidence base as unknown or emerging. These assessments form the rationale for caution in expanding coverage beyond select, well‑documented indications.

The policy emphasizes that several indications reported in the literature lack documentation of precise lesion localization, biopsy confirmation, prior standard therapies, or multidisciplinary rationale. Such missing documentation reduces the ability to determine appropriateness and supports case‑by‑case review or designation as investigational when these elements are absent.

Use of LITT for newly diagnosed unresectable glioblastoma and certain intracranial tumor indications is described in the literature but remains investigational. Systematic reviews and series report limited, heterogeneous data with substantial bias; authors conclude it is premature to recommend routine LITT for newly diagnosed GBM outside research settings.

The provided excerpts do not declare specific conditions explicitly as not medically necessary beyond the investigational lists; rather, the document focuses on evidence limitations and indicates that routine replacement of standard treatments without comparative data is not supported.

There is no single statement in the cited excerpts that universally declares LITT as not medically necessary; instead, multiple authors and assessments emphasize the absence of randomized controlled trials and call for further research, supporting restrictive coverage for indications lacking robust evidence.

Authors of systematic reviews on newly diagnosed glioblastoma concluded that the overall quality of evidence is very low (GRADE assessment) and that available studies suffered serious or critical risk of bias, supporting the conclusion that it is too early to recommend LITT for nGBM in routine practice.

Across indications the policy and cited literature describe outcomes as preliminary. Many series are small, retrospective, and single‑center; authors consistently call for larger studies with longer follow‑up to confirm initial findings before broader adoption.

Coding and Billing

Covered CPT CodesCPTCovered

61735	Creation of lesion by stereotactic method, including burr hole(s) and localizing and recording techniques, single or multiple stages; subcortical structure(s) other than globus pallidus or thalamus.
61736	Laser interstitial thermal therapy (LITT) of lesion, intracranial, including burr hole(s), with magnetic resonance imaging guidance, when performed; single trajectory for 1 simple lesion.
61737	multiple trajectories for multiple or complex lesion(s).

CPT Codes not covered for indications listedCPTNot Covered

0673T

Ablation, benign thyroid nodule(s), percutaneous, laser, including imaging guidance.

ICD-10 codes covered if selection criteria are metICD-10Covered

C71.0	Malignant neoplasm of cerebrum, except lobes and ventricles [not covered for insular tumors and pineal region glioma]
C71.1	Malignant neoplasm of frontal lobe [not covered for insular tumors and pineal region glioma]
C71.2	Malignant neoplasm of temporal lobe [not covered for insular tumors]
C71.3-C71.9	Malignant neoplasm of brain [not covered for insular tumors and pineal region glioma]
C79.31	Secondary malignant neoplasm of brain [Glioblastoma]
G40.011-G40.019	Localization-related (focal) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, intractable.
T66.XXX+	Radiation sickness, unspecified [radiation necrosis]

ICD-10 codes not covered for indications listedICD-10Not Covered

C25.0-C25.9	Malignant neoplasm of pancreas
C34.00-C34.92	Malignant neoplasm of bronchus and lung
C43.0-C43.8	Malignant melanoma of skin
C50.011-C50.929	Malignant neoplasm of female and male breast

Codes cited in cost-analysis study (ICD-9-CM)ICD-9

17.61	ICD-9-CM procedure code (used for LITT in cited retrospective study)
01.59	ICD-9-CM procedure code (open craniotomy comparison in cited study)
191.0-191.9	ICD-9-CM diagnosis codes for primary brain cancer (used for subgrouping)
198.3	ICD-9-CM diagnosis code for metastatic brain cancer (used for subgrouping)
348.5	ICD-9-CM code for brain edema (exclusion in cited study)

Prior Authorization, Documentation, and Provider Guidance

Billing Rule

Prior authorization / coverage coding note

CPT/HCPCS codes for interstitial laser therapy (ILT) are covered only when the policy selection criteria are satisfied; billing must use appropriate diagnosis and procedure codes that correspond to a covered indication.

Covered CPT codes apply only if selection criteria are met. Document diagnosis codes when billing.

Prior Authorization

Prior authorization: document prior therapies and lesion/functional status

Prior authorization is recommended — when requesting authorization, include a concise stepwise treatment history documenting prior therapies (e.g., stereotactic radiosurgery, prior open resection, prolonged high‑dose corticosteroids, bevacizumab) or reasons these standard therapies were contraindicated or infeasible. For focal epilepsy, document prior anti-seizure medication trials and any prior resective epilepsy surgery.

Background and Evidence Summary

Interstitial laser therapy (ILT) is a minimally invasive, image‑guided technique in which a laser fiber or needle probe is stereotactically placed into a target lesion and laser energy is applied to generate thermal coagulative necrosis under real‑time imaging guidance. Variants include MRI‑guided LITT (MRgLITT) and spinal LITT (sLITT); MR thermometry and thermal‑damage‑threshold (TDT) contours are commonly used to monitor and quantify ablation coverage.

Definitions and Terms

inv-70: Interstitial laser therapy (ILT) — image-guided needle probe delivers laser energy to heat/destroy tumor cells

DefinitionImage-guided needle probe delivers laser energy to heat and destroy tumor cells.

PurposeMinimally invasive alternative to open resection for small or surgically inaccessible lesions, aiming to reduce bleeding, scarring and recovery time.

Typical settingsUsed in outpatient or short-stay settings with image guidance (MRI or CT) to monitor ablation.

inv-71: Novilase — Novilase system FDA 510(k) clearance for breast fibroadenomas ≤2 cm

Device / SystemNovilase Interstitial Laser Therapy system (Novian Health, Inc.).

Regulatory statusReceived U.S. FDA 510(k) marketing clearance in 2007.

Policy Summary

PayerAetna

PolicyInterstitial Laser Therapy

Policy CodePolicy 0781

Change TypeNo material changes

Effective Date04/10/2009

Next Review Date08/22/2024

Key ActionDocument indication, prior therapies, lesion characteristics, and multidisciplinary rationale when submitting prior authorization.

SourceLink

On This Page

Clinical judgment required given limited evidence

Consider case‑by‑case review given evidence gaps.

Authors recommend further high‑quality prospective research.

Document prior stereotactic radiosurgery or open surgery and reasons for infeasibility.
List prior medical therapies (steroids, bevacizumab) and duration/response.
For epilepsy, list anti-seizure medication trials and prior epilepsy surgery if any.

Prior Authorization

Prior authorization recommended

For certain indications (spinal metastasis, intracranial tumor recurrence/radiation necrosis, drug‑resistant focal epilepsy), prior authorization is recommended to ensure appropriate case selection. Include indication, prior therapies, performance status (e.g., KPS), and lesion characteristics.

Indication: spinal metastasis, intracranial tumor (recurrent glioblastoma/metastasis) with prior radiosurgery, radiation necrosis, or drug‑resistant focal epilepsy.
Functional status: Karnofsky Performance Status (KPS) or equivalent.
Lesion characteristics: size, location, number of lesions, proximity to eloquent cortex or spinal cord.

Prior Authorization

Prior auth for epilepsy indications

For epilepsy indications, prior authorization should confirm medically refractory epilepsy and objective localization of seizure focus. Provide documentation of failed medication trials, invasive or noninvasive localization (e.g., SEEG, MRI evidence of MTS), and neuropsychological testing when available.

Evidence of medically refractory epilepsy (failed appropriate anti-seizure drugs).
Localization evidence: SEEG, scalp EEG, MRI findings (e.g., mesial temporal sclerosis).
Pre‑ and post‑operative neuropsychological assessments when available.

Documentation Required

Prior authorization for NeuroBlate/Device safety discussion

Providers should disclose device‑specific safety concerns when using recalled or recalled-classified systems (e.g., NeuroBlate). Prior authorization and informed consent should reflect known device risks and alternative options.

Document discussion of NeuroBlate/Class I recall safety concerns and rationale if device will be used.
Consider alternative devices/procedures if manufacturer mitigation is incomplete.
If proceeding with a recalled device, document that patient was informed and alternatives considered.

Note

Prior authorization not specified in this section

No explicit payer prior authorization code list or mandated PA process is specified in the excerpts; verify current Aetna prior authorization requirements and local plan rules.

This section does not list a PA form/code list.
Check Aetna provider portal or member plan documents for any PA requirements.

Denial Risk

Insufficient evidence may lead to noncoverage

Insufficient or low‑quality evidence for many indications (small case series, lack of randomized controlled trials) may lead to noncoverage or denial for experimental/investigational uses. Be prepared to supply robust clinical rationale and supporting literature for off‑label or uncommon indications.

Experimental/investigational indications (see policy list) are at higher risk for denial.
Provide clinical justification and available literature when requesting coverage for less‑established uses.

Denial Risk

Evidence gaps may trigger denial

Evidence gaps and heterogeneity in the LITT literature (device types, patient selection, outcomes) may trigger coverage denial, particularly when LITT is proposed as a substitute for established standard‑of‑care treatments without clear comparative data.

Absence of randomized comparative data versus craniotomy or standard surgical resection.
Heterogeneous outcomes and small series may be insufficient to justify replacement of SOC.

Note

No explicit coverage authorization or denial triggers provided

Some segments of the source do not specify explicit authorization, step‑therapy, or denial triggers; where none are stated, follow general plan PA and medical‑necessity processes and submit full supporting documentation.

When the policy text is silent, use standard prior authorization channels.
Include clinical notes, imaging, biopsy results, and prior therapy history to support the request.

Documentation Required

Expected clinical documentation

Expected clinical documentation to support a coverage determination includes demographics, indication, lesion volumes and characteristics, prior treatment history, operative reports, pre/post imaging, biopsy results when performed, KPS, and complication history.

Demographics and comorbidities (age, KPS).
Lesion details: size, number, location, imaging.
Operative documentation: device used, trajectories, intra-op MRI images/screenshots, and deviations.
Pathology/biopsy results if used to distinguish tumor recurrence vs radiation necrosis.
Pre/post functional and seizure assessments (for epilepsy).

Note

Studies and registries report demographic and outcome elements

Studies and registries commonly report demographics, procedural details, adverse events, quality of life, hospitalization length, and survival metrics; include these data elements in requests when available to strengthen the clinical case.

Registry elements: demographics, intra‑procedural data, AEs, QOL, hospitalizations, survival.
Provide follow‑up imaging and outcome measures (PFS, OS, seizure freedom rates).

Documentation Required

Clinical documentation and biopsy

When LITT is used to treat suspected post‑radiation treatment effect or radionecrosis, document biopsy confirmation when available; many series required stereotactic biopsy confirmation prior to ablation.

Include stereotactic biopsy pathology when performed to confirm radiation necrosis vs tumor recurrence.
Provide pre‑procedure imaging and biopsy reports.

Step Therapy

No step‑therapy requirements detailed

No specific step‑therapy requirements, prior authorization code lists, or explicit step‑therapy processes are detailed in these excerpts; there are no plan-mandated step therapy sequences described here.

No step‑therapy sequencing (e.g., mandatory prior craniotomy or SRS) is specified in the source excerpts.
Document prior standard therapies attempted or contraindicated; do not assume a required formal step‑therapy authorization unless plan documents state otherwise.

Denial Risk

Device safety / recall risk

If proceeding despite device recall concerns (e.g., NeuroBlate Class I recall), document that alternatives were considered and that the patient was informed of risks; consider using alternative devices or approaches when feasible.

FDA Class I recall for Monteris NeuroBlate probe due to unintended heating and potential patient injury.
If no viable alternative exists, document extreme caution and informed consent.

Indication clearedTreatment of breast fibroadenomas that are 2 cm or less in size.

Other uses describedAlso used for general soft tissue incision, excision, coagulative necrosis and interstitial laser coagulation in general surgery contexts.

inv-72: LITT / MRgLITT — MR-thermometry-guided LITT description and real-time monitoring

TechniqueLaser interstitial thermal therapy (LITT) uses a percutaneously placed laser probe with real-time MR thermometry to coagulate target tissue.

MonitoringReal-time MRI thermometry provides intra-procedural feedback on thermal dose and tissue heating to control ablation extent.

Applications notedUsed for gliomas, radiosurgery-resistant metastases, radiation necrosis, and ablation of epileptogenic foci in reported series.

inv-73: sLITT — spinal LITT application for spinal metastases/epidural compression

DefinitionSpinal LITT (sLITT) is application of LITT to spinal metastases to reduce epidural compression as an alternative to open surgery prior to stereotactic radiosurgery.

Procedure elementsA laser probe is percutaneously placed in the epidural space and real-time thermal MRI is used to monitor tissue damage; typically followed by SSRS.

Reported outcomesSeries reported decreased epidural tumor thickness, reduced pain (VAS) and improved QOL in early cohorts.

inv-74: MRgLITT / sLITT — stereotactic insertion of laser probes with MR guidance

DescriptionStereotactic insertion of laser probes with MRI guidance (MRgLITT/sLITT) enables precise probe placement and thermal monitoring for intracranial or spinal targets.

Key componentsStereotactic targeting hardware, MRI thermography for real-time feedback, and controlled laser probe positioning (rotation/depth).

Intended benefitAllows ablation of deep or surgically inaccessible lesions while minimizing open-surgery morbidity.

inv-75: Engel classification — scale for post-surgical seizure outcomes (Engel I = seizure freedom)

PurposeScale to categorize post-surgical seizure outcomes after epilepsy surgery or ablation.

Engel ISeizure freedom or only auras (sustained freedom from disabling seizures).

Use in literatureReported in MRgLITT/SLAH epilepsy series to describe outcomes and compare to open resections.

inv-76: Laser interstitial thermal therapy (LITT) — stereotactic probe placed into brain target to ablate tissue

ProcedureStereotactic probe is placed into a brain target and laser energy is applied under MRI thermography to heat and ablate tissue.

ControlsReal-time thermometry and software-guided thermal dose prediction are used to tailor coagulation and limit collateral damage.

Indications describedUsed for deep-seated gliomas, radiosurgery-resistant metastases, radiation necrosis and epileptogenic foci in reported cohorts.

inv-77: Stereotactic laser amygdalo-hippocampectomy (SLAH) — MRgLITT targeting amygdala-hippocampal complex for MTLE

Procedure nameStereotactic laser amygdalo-hippocampectomy (SLAH) — MRgLITT targeting the amygdala‑hippocampal complex.

IndicationUsed for medically refractory mesial temporal lobe epilepsy (MTLE), often evaluated with SEEG or imaging for focality/MTS.

OutcomesSeries report variable seizure‑freedom rates; outcomes often better in patients with mesial temporal sclerosis (MTS).

inv-78: LITT (Laser interstitial thermal therapy) — image-guided technique generating high temperatures to ablate pathological brain tissue

DefinitionImage-guided technique that generates high temperatures via a laser fiber to ablate pathological brain tissue using MRI thermometry.

Ablation mechanismThermal coagulation resulting in treatment-related necrosis visible on post-procedure MRI studies.

Clinical contextsApplied to radiosurgery-resistant metastases, radiation necrosis, gliomas and epileptogenic foci in case series and reviews.

inv-79: TDT-line — thermal-damage-threshold lines used to quantify ablation coverage

DefinitionThermal‑damage‑threshold (TDT) lines are MR thermography dose‑equivalent contours used to quantify ablation coverage.

ExamplesYellow TDT line = dose equivalent of 43°C for 2 minutes; Blue TDT line = dose equivalent of 43°C for 10 minutes.

UsePercent of tumor within TDT contours is reported to indicate completeness of ablation and is associated with local control in studies.

inv-80: MRgLITT / LITT — MR-guided laser interstitial thermal therapy description

DefinitionMR‑guided LITT (MRgLITT) uses MRI thermometry to provide real‑time feedback during laser ablation of intracranial lesions.

Procedure settingPerformed in MRI suites with stereotactic targeting and thermography to control ablation extent and monitor surrounding tissue.

Clinical roleDescribed as minimally invasive option for patients who are poor candidates for craniotomy, including recurrent metastases and radiation necrosis (NCCN Category 2B).

inv-81: SLITT — spinal laser interstitial thermotherapy adaptation for epidural spinal metastases

TermSLITT — spinal laser interstitial thermotherapy; adaptation of LITT for epidural spinal metastases/spinal cord compression.

TechniquePercutaneous epidural placement of laser probe with MR thermometry monitoring; often followed by stereotactic radiosurgery for local control.

Reported outcomesStudies reported pain reduction, improved QOL and radiographic decompression with low permanent neurologic injury in small series.

inv-82: LITT / SLA — alternative naming for laser interstitial thermal therapy / stereotactic laser ablation

SynonymsLITT is also referred to as stereotactic laser ablation (SLA) or stereotactic laser therapy in the literature.

Core conceptMRI‑guided delivery of laser energy to ablate intracranial targets with stereotactic precision and thermography feedback.

ReportingStudies commonly report TDT coverage, lesion volume, and clinical outcomes when using these terms interchangeably.

inv-83: Thermal Damage Threshold (TDT) lines — MR thermography dose-equivalent contours explained

DefinitionMR thermography dose‑equivalent contours (TDT lines) represent thermal dose thresholds used to quantify percent of tumor treated.

Dose examplesYellow = 43°C for 2 minutes; Blue = 43°C for 10 minutes.

Clinical usePercent tumor within TDT contours (e.g., yellow/blue lines) is reported to evaluate ablation completeness and correlate with outcomes.

inv-84: Indications described — reported indications in literature including drug-resistant seizures, unacceptable surgical risk, recurrent hemorrhage

Reported indicationsDrug‑resistant seizures, unacceptable surgical risk lesions, recurrent hemorrhage, lesion recurrence after radiosurgery, and deep/eloquent-area lesions not amenable to open resection.

Evidence statusThese indications are reported in the literature but high‑quality randomized comparative data are generally lacking.

Research usesInvestigated as a method to transiently disrupt the peri‑tumoral BBB to potentially enhance delivery of systemic therapies in pilot studies.