MRI-GUIDED HIFU
MRGFUS PRECISION
MRgFUS combines focused ultrasound with real-time MRI temperature mapping — confirming at every millimetre of the treatment volume that the target tissue has reached the ablation threshold and adjacent critical structures remain thermally safe.
analyticsAt a Glance
- check_circleMR thermometry maps temperature in real time during treatment — not inferred from tissue changes but directly measured
- check_circleCloses the treatment loop: if temperature is insufficient at a focal point, the system increases exposure automatically
- check_circleApproved indications: uterine fibroids (FDA/CE), bone metastasis pain (FDA), essential tremor (FDA/CE), prostate cancer (CE)
- check_circleThe InSightec ExAblate platform is the dominant clinical MRgFUS system globally
What Is MRgFUS and How Does It Differ from Ultrasound-Guided HIFU?
All HIFU systems use focused acoustic energy to destroy tissue — the guidance platform is what distinguishes them. Ultrasound-guided HIFU (USgHIFU) uses diagnostic ultrasound to visualise the treatment zone, inferring thermal effect from tissue echogenicity changes. MRgFUS replaces that inference with measurement: real-time MRI thermometry directly quantifies the temperature at every point in the treatment volume during the procedure.
“USgHIFU sees where the beam goes. MRgFUS measures what the beam does — a fundamentally different level of treatment control.”
MR Thermometry: What It Measures and How
MR thermometry uses the proton resonance frequency (PRF) shift principle: the resonance frequency of water protons changes predictably and linearly with temperature. By measuring this shift across the treatment volume in real time, the MRI system produces temperature maps accurate to ±1–2°C at each voxel — updated every 3–5 seconds throughout the treatment session.
Closed-Loop Treatment Control
MRgFUS systems use these temperature maps to close the feedback loop: if a focal point has not reached the target temperature (typically 56–65°C), the system automatically delivers additional exposure. If the temperature at the focal point or in adjacent tissue approaches a safety threshold, the system pauses. This automated safety-efficacy balance is not available in any ultrasound-guided system.
MRgFUS vs USgHIFU: A Direct Comparison
The choice between MRgFUS and USgHIFU is not a quality hierarchy — it is a clinical tool selection based on indication, anatomy, and required precision.
| Feature | MRgFUS (ExAblate) | USgHIFU (HAIFU / JC system) |
|---|---|---|
| Temperature monitoring | Direct MR thermometry — temperature measured at each voxel in real time | Indirect — tissue echogenicity changes used as proxy; no quantitative temperature data |
| Safety margin precision | Automated thermal safety zones protect adjacent structures with ±1–2°C accuracy | Operator-dependent; relies on experience and tissue change assessment |
| Closed-loop feedback | Yes — system adjusts exposure based on real-time temperature response | No — manual parameter adjustment only |
| Imaging during treatment | Full MRI capability — anatomy, perfusion, and temperature simultaneously | Ultrasound only — limited soft tissue contrast; no perfusion imaging |
| Indications (approved) | Uterine fibroids, bone metastasis pain, essential tremor, prostate (CE), brain | Uterine fibroids, liver, pancreas, kidney, bone, soft tissue tumours |
| Patient positioning | Supine or prone inside MRI bore — 60–90 min; claustrophobia a limitation | Water bath — prone or lateral; more flexible positioning; no claustrophobia |
| Session duration | 90–240 min (fibroid); 60–90 min (bone mets) | 45–120 min (indication-specific) |
| Equipment availability | Selected major centres globally; ~800 installed systems worldwide | 200+ centres in China alone; more widely distributed globally |
| Relative cost | Higher — MRI scanner integration required | Lower — standalone system without MRI dependency |
| Best for | Fibroids (precision ablation), brain (essential tremor), bone mets near spinal cord | Liver, pancreas, kidney, soft tissue oncology; high-volume fibroid centres |
How an MRgFUS Session Works: Step by Step
The MRgFUS procedure integrates a HIFU transducer into the MRI table — allowing simultaneous treatment and imaging inside the same system.
- 1
Patient Preparation and Positioning
Skin at the acoustic entry zone is prepared (depilated, degassed gel applied). For fibroid MRgFUS, the patient lies prone with the lower abdomen coupled to the transducer via a water-filled membrane built into the table. For brain MRgFUS, the patient is supine with a water-cooled helmet transducer fitted.
- 2
Diagnostic MRI Acquisition
High-resolution T2-weighted and contrast-enhanced MRI sequences map the target lesion, adjacent anatomy, and planned treatment volume before any HIFU energy is delivered. Exclusion zones are delineated around critical structures.
- 3
Low-Energy Test Sonications
Before full treatment power is used, low-energy test pulses confirm transducer alignment and verify that the focal point lands precisely on the planned target location. Temperature maps confirm the test focal point position.
- 4
Full Treatment Sonications
Treatment proceeds in sequential sonications across the planned volume. Each sonication is 15–20 seconds. The MR thermometry display shows the temperature rise in real time — the operator sees both the target zone reaching 56–65°C and the safety margins around critical structures staying below 42°C.
- 5
Real-Time Safety Checks
The system continuously monitors temperature at the focal point and in exclusion zones. If any exclusion zone approaches its safety threshold, the sonication is automatically paused. The operator can resume with modified parameters or re-plan the zone layout.
- 6
Post-Treatment Contrast MRI
Gadolinium contrast is injected and a perfusion MRI series confirms the non-perfused volume — the proportion of the target that no longer enhances. This immediate post-treatment MRI provides the same-day efficacy assessment that determines whether the treatment goal has been achieved.
Where MRgFUS Has the Strongest Evidence and Regulatory Approval
MRgFUS has regulatory approval for specific indications where its temperature monitoring precision provides a meaningful clinical advantage over USgHIFU.
Uterine Fibroids — FDA and CE Approved (ExAblate)
MRgFUS (ExAblate) is FDA-approved for symptomatic uterine fibroids and CE-marked in Europe. The largest randomised evidence base for focused ultrasound fibroid treatment uses the ExAblate platform. MR thermometry allows precise ablation of fibroid tissue while protecting the endometrium and adjacent bowel — particularly valuable for posterior fibroids close to the rectosigmoid.
Bone Metastasis Pain — FDA Approved (ExAblate 2100 Bone)
FDA-approved for pain palliation from bone metastases. The ExAblate 2100 system uses a focused transducer against a water-cooled coupling on the skin overlying the bone lesion. MR thermometry confirms cortical and periosteal heating while protecting adjacent spinal cord, nerve roots, and vascular structures — a precision requirement that makes MRgFUS specifically advantageous over USgHIFU for vertebral and pelvic bone metastases.
Essential Tremor and Brain — FDA / CE Approved (ExAblate Neuro)
Transcranial MRgFUS using the ExAblate Neuro system is FDA-approved for essential tremor and CE-marked for additional neurological indications. The skull correction algorithms compensate for skull-induced beam distortion to precisely target deep brain structures (VIM nucleus of the thalamus). MR thermometry is the only way to confirm focal temperature inside the skull without an electrode — making MRgFUS the only non-invasive option for deep brain ablation.
MRgFUS: Key Numbers
Technical and clinical reference figures for the MRgFUS platform.
- ±1–2°CMR thermometry accuracy at focal pointProton resonance frequency shift thermometry achieves 1–2°C spatial accuracy — sufficient to confirm ablation threshold and monitor safety margins simultaneously.
- ~800ExAblate systems installed globallyInSightec ExAblate installations across all system variants (Body, Neuro, Bone) — concentrated at major academic medical centres in the US, Europe, Israel, Japan, and China.
- 56°CMinimum temperature for irreversible ablationMR thermometry confirms that every treated voxel has reached the 56°C protein denaturation threshold — the objective criterion for technical success that USgHIFU cannot directly confirm.
- 3–5 secMR thermometry map update rateTemperature maps are refreshed every 3–5 seconds throughout the treatment — providing near real-time feedback on thermal evolution across the full treatment volume.
More from the HIFU Therapy Resource Library
Continue exploring HIFU — from technology platforms to cost comparisons and the full patient experience.
- HIFU Therapy — Complete Treatment Guide
- HIFU Technology Platforms: HAIFU, JC, and MRI-Guided Systems
- HIFU Physics: How Acoustic Focusing Destroys Tissue
- HIFU for Uterine Fibroids: MRgFUS Complete Guide
- Transcranial MRgFUS for Brain Tumours and Neurological Conditions
- HIFU Cost: China vs India vs Western Countries
Frequently Asked Questions
Common questions about MRI-guided HIFU from patients comparing guidance platforms.
About MRgFUS
Is MRgFUS better than USgHIFU for uterine fibroid treatment?
MRgFUS offers superior real-time temperature monitoring — confirming that each focal point in the fibroid reaches the ablation threshold and that the endometrium and adjacent bowel stay below safety limits. For fibroids near the endometrium, the sacrum, or the bowel, this precision advantage translates directly into clinical safety. For straightforward anterior intramural fibroids away from sensitive structures, high-volume USgHIFU centres achieve equivalent NPV and symptom relief outcomes — and at substantially lower cost. The choice should be driven by your fibroid's location and the specific safety requirement, not a general preference for one platform over the other.
I am claustrophobic — can I still have MRgFUS?
Claustrophobia is a genuine practical limitation for MRgFUS, which requires 90–240 minutes inside an MRI scanner bore. Pre-procedure anxiolytic medication (oral lorazepam or similar) allows many claustrophobic patients to tolerate the session. Open-bore MRI systems are being integrated into some newer ExAblate configurations, and sedation can be offered for patients who cannot tolerate standard closed-bore MRI. If your claustrophobia is severe, USgHIFU — which takes place in an open water bath with no confined space — is a practical alternative that should be discussed with your treating team. CancerFax can advise on which approach is available and appropriate for your specific indication and symptoms.
How CancerFax Helps
CancerFax is a specialist cancer access and patient-navigation platform. We help patients and families understand their options, organise medical records, coordinate hospital communication, and support cross-border treatment planning where appropriate.
We help collect and organise reports, scans, pathology, biomarker results, and treatment history for structured case review.
We communicate with hospitals or trial teams to assess whether a case may be suitable for further screening.
We support appointment coordination, document submission, translation, and direct communication with international departments.
For international patients, we help with practical coordination — travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
From inquiry through to follow-up, our coordinators provide a single point of contact for the family.
CancerFax does not guarantee treatment access, eligibility, or clinical outcome. Our role is to help patients access accurate information, structured review, and appropriate specialist pathways.
Interested in MRI-Guided HIFU?
CancerFax can advise on whether MRgFUS is the appropriate HIFU platform for your indication — and connect you with ExAblate-equipped centres in China, India, or Europe depending on your location and clinical needs.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified oncologist before making treatment decisions.