Magnetic resonance guided focused ultrasound is a technique used to treat symptomatic uterine fibroids in a non-invasive manner.
This treatment does not require surgery and patients can be treated as outpatients.
The procedure consists in the deposition of very high-intensity ultrasound energy focused on to the exact location of the fibroids. This leads to the heating of the target area. At over 56deg C cellular protein denaturation takes place and the cell dies in a process known as coagulative necrosis.
The temperature of the target area is monitored during the procedure through magnetic resonance (MR) images.
MR is sensitive to heat alterations in tissue, thus allowing real-time thermal imaging throughout the process.
The procedure is carried out with the patient lying prone within the MRI scanner on a modified bed which contains the ultrasound transducer.
A vein is canulated and a catheter is passed to control the exact position of the bladder and to control its filling.
The MRI-guided focused ultrasound is then directed for two and a half hours, during which time the patient receives IV sedation and analgesia.
This type of guided, focused ultrasound treatment is non-invasive and achieves effective symptomatic improvement in patients with fibroids, with a moderate amount of fibroid shrinkage of between 30-40 per cent at one year.
Most patients will only require one session, while about 20 per cent will have two sessions.
The uterus remains in place, leaving the woman with the potential for fertility.
However, it is unknown if fertility in women is actually boosted after treatment.
So far the procedure has proved very accurate and safe, and has significantly reduced the symptoms in 80 per cent of patients. Symptom improvement includes abdominal pain, excessive menstrual pain and blood loss and related bladder symptoms.
Patients with fibroids up to 20cm in diameter can be treated. Patients with larger fibroids, or in patients where the bowel is in the way so that a proper acoustic window to reach the fibroid cannot be achieved are not suitable for treatment.
Mid-line scars also cause problems, and if the scar is over-lying the acoustic window that allows treatment of the fibroid, this prevents the procedure being carried out.
Patients with contraindications for magnetic resonance imaging, such as those fitted with a pacemaker, are not suitable for the procedure.
Complications of the treatment are very low.
The main risks are very occasional minor skin burns.
Very mild nerve irritation might occur, which might persist for a day or two afterwards.
Liver and bone tumours
The guided ultrasound technique is currently being tested on liver tumour ablation.
Patients suffering from liver tumours that cannot be removed by surgery and which are less than 5cm in diameter might be suitable for therapy.
However, it is not suitable for patients with tumours near the rib cage.
Trials are also taking place on the effect of focused ultrasound on breast cancers and bone secondaries.
Metastatic bone tumour patients, whose tumours are clearly visible by MRI and accessible by focused ultrasound, might be suitable for therapy.
However this type of treatment is not suitable for tumours in the spine.
Researchers anticipate that there will be further developments in the treatment of prostate malignancies and in the brain, and probably also in renal tumours within the next two years.
While MR-guided focused ultrasound for the treatment of fibroid symptoms has been approved by US authorities, it has not yet been approved by NICE in the UK. However, the technique is available privately.
Despite the success of the technique so far, the acceptance of this procedure within the NHS will take some time.
Research into the technique is ongoing and health economic analyses are being carried out in partnership with the London School of Hygiene and Tropical Medicine. This has just started and will take between six and nine months to complete.
However, the non-invasive nature of the treatment, minimal post-treatment care, lack of substantial side-effects and the rapid return of the patient to work could mean that it is a very cost-effective procedure. Patients can return to work within one day of the procedure, compared to three to six months recuperation time following a hysterectomy.
- Professor Gedroyc is professor of radiology at Imperial College London and St Mary's Hospital, London.
- Magnetic resonance guided focused ultrasound can be used to treat symptomatic uterine fibroids.
- The technique is non-invasive and patients are treated as outpatients.
- It involves the deposition of high-intensity ultrasound energy focused exactly on to the fibroids.
- Effective symptomatic improvement can be reached, with a moderate amount of fibroid shrinkage of between 30 and 40 per cent at one year.
- The main risks are very occasional minor skin burns. Very mild nerve irritation lasting a day or two might also occur.
- The technique is currently being tested on liver tumour ablation and bone secondaries.
- Hindley J, Gedroyc W M, Regan L. MRI guidance of focused ultrasound therapy of uterine fibroids: early results, 2004. Am J Roentgenol 183(6): 1,713-9
- Stewart E A, Gedroyc W M et al. Focused ultrasound treatment of uterine fibroid tumours: safety and feasibility of a non-invasive thermoablative technique 2003. 189(1): 48-54.