Method FUZZ MRI ablation of uterine fibroids: the advantages and disadvantages of the method
Since 2000, more and more application in the treatment of uterine fibroids finds focused ultrasound ablation (FUZZ). FUZZ-ablation of uterine fibroids with ultrasound waves, which is used to control by means of magnetic resonance imaging, is one of the most modern methods. It combines the latest technological advances in the diagnosis and treatment of fibroids.
The characteristics and description method
In the structure of gynecological diseases one of the first places is occupied by the uterine fibroids. They are the most common benign tumors and according to various sources, diagnosed at 25-45% of women of reproductive age. When conducting casual research fibroids are detected on average 70% of women.
Recently the main methods in their treatment was hormone therapy, surgical myomectomy (removal of the node), and hysterectomy (amputation or hysterectomy). However, the results of treatment of the first two methods are characterized by high recurrence, and hysterectomy hormonal disorders and vegetative-vascular disorders.
In recent decades introduced new ways of treatment of hysteroscopic resection of submucosal (submucous) nodes, laparoscopic or transvaginal temporary uterine artery embolization (UAE), laser or cryosurgery of the nodes. However, there is no universal method that can be applied to all patients. All of these techniques to a greater or lesser extent, invasive. The only non-invasive technology is the fuzz MRI ablation of uterine fibroids.
The physical basis and mechanisms of action
The term «ablation» means the destruction and partial removal of biological tissue. The General physical meaning of FUZZ-ablation is an isolated thermal effects of focused ultrasonic waves to areas of the body, evaporation and degradation. From the usual diagnostic waves used in ULTRASONIC research, therapeutic ultrasonic waves are less frequency (about 1 MHz) and a higher capacity of 50-300 watts.
It is assumed that the mechanism of the effect of focused ultrasound for fibroids is:
- direct temperature impacts, resulting from the release of energy of the ultrasonic wave when meeting an obstacle; the heating of biological tissue to 55-60 in one second leads to their dehydration, denaturation (precipitation) of proteins, damage to vascular and destruction of collagen structures;
- indirect effect on the tumor, which is the change in local blood flow and malnutrition of its tissues.
The use of ultrasonic waves of sufficiently high energy power for 10 seconds, point cause necrosis (necrosis) tissues. Ablation zone formed under the influence of a single focused pulse has a cylindrical shape. Its diameter near the radiator is 2 mm, length 4 mm and the greatest depth (15 cm) minimum size of necrotic cylinder is 2 mm and 8 mm, the maximum is 10 and 20 mm, respectively.
Treatment of benign tumors, in particular uterine fibroids, do not require the destruction of each of its cells. Enough to perform coagulation of the tissues of the body in its different parts, as a rule, 30-50 points, which allows to fully achieve the cessation of uterine bleeding and get rid of symptoms of compression of the tumor to the pelvic organs.
As in the process of diagnostic ultrasound, ultrasonic waves have a FUZZ-ablation to penetrate through the tissue without damage. However, the focusing of the rays and the duration of exposure within 1-30 seconds leads to heating tissue to 55-90. The region of thermal coagulation in this case is 0.6 mm in diameter and 2 cm deep tumor and has not spread to nearby areas. Such exposure is carried out repeatedly until the moment destructive process will not be covered by the planned amount of the treatment region.
The highest selectivity of action, efficacy and safety of FUZZ-ablation in the treatment of uterine fibroids due to several factors:
- a significantly higher content of the matrix (extracellular connective tissue structures) in tissue most fibroids compared to adjacent tissue, in particular surrounding the tumor of the myometrium; the intercellular matrix has the properties delay and high absorption of energy of ultrasonic waves, and muscle cells of the tumor already affected secondarily as a result of heating of the matrix;
- the difference of perfusion (the passage of) blood in the tumor and the normal myometrium;
- the location of the vascular network of the peripheral departments of fibroids.
These properties due to the practical impossibility of damage to unmodified vessels and the muscle layer of the uterus that contains the fibroids. The device generating the wave, allows you to configure the settings for the focus from the small size (diameter of 0.8 mm and a length of 1 cm) to large ( diameter 0.7 mm and length up to 4.5 cm). In addition, the selectivity and the effectiveness of the procedure is provided by the determination of the exact localization, tumor volume, possibility of separating of segments impact through MRI (magnetic resonance imaging).
Cure myoma node with a diameter of 2 cm could be achieved after 1-3 effects (sonicate) in the course of one procedure, and fibroids of the uterus size 20 weeks or after 100 Sonicare. The procedure lasts on average 2.5-5 hours.
At the same time, the effect of FUZZ-ablation is directly dependent on the structure of the myoma, that is, its magnetic resonance properties measured in relation to the muscle layer of the uterus. Depending on this, the tumors are divided into:
- Hypo -, or dark — histological structure corresponds to the simple myoma node without the presence of edema of the connective tissue (stroma); they use small energy of ultrasonic waves and a small number of impacts during one procedure (80);
- isointensity, or «gray,» which is defined by stromal edema; the treatment usually takes place in two stages — «drying» and the healing process;
- hyperintense, or «white,» the therapy which is usually ineffective, as they either do not absorb electromagnetic waves, or the degree of absorption is very low.
Difficult FUZZ therapy education with heterogeneous structure, a large number of partitions, zones lack of perfusion within the site and the presence of calcifications. The latter not only reflect light, but are able to reallocate their energy, which can cause damage to surrounding healthy tissues.
The benefits of diagnostics and control by means of MRI
In the initial stages of application of the methodology FUZZ-ablation was used fluoroscopy, ultrasound, computed tomography. However, they do not allow continuous dynamic control over the degree of the temperature of heating, which on average should amount to 60 ° and should not exceed 100о.
Failure to comply with these conditions may cause boiling of the interstitial (intercellular) fluid vaporization and formation of gas bubbles, which causes damage and tearing of the tissue, the border zone of ablation. In addition to the constant temperature control is also required high-quality visualization of the tumor itself and the precise definition of their localization.
Namely, magnetic resonance imager, part of the hardware system for carrying out the FUZZ-ablation allows:
- pre-split abnormal formation of the conditional segments (segments);
- plan the duration and power of exposure;
- accurately summarize the focus of the ultrasonic waves of high power (up to 300W) to the point of impact;
- selectively heat the tissue to a high temperature without increase in adjacent healthy structures of the myometrium.
The degree of necrosis and the volume of tissue subjected to ablation, is estimated in real time using the magnetic resonance temperature mapping. At the same time, the heterogeneity of the fibroids in many cases becomes an obstacle in the calculation of the required temperature at the points-targets.
Thus, MRI is used for:
- high-precision spatial planning points and the geometric parameters of each sonically (impact);
- precision focusing ultrasonic waves;
- control each sonically individually and the entire procedure as a whole in real time;
- adequate assessment of the volume of the destroyed tissues, for which additional injection of contrast solution-based preparations of gadolinium.
Evaluation of the results
In accordance with the data of different authors the results of treatment with FUZZ-ablation mixed. For example, the improvement of symptoms after the procedure in the period from six months to 1 year, some authors noted 50% of patients, or 79%, and some at 89% and even 92%.
The maximum decrease in the severity of symptoms of the disease were observed during the first 3 months after the procedure. The estimate of reduction of tumor volumes by different authors ranges from 13.5% to 48,7% of the original volume.
And ambiguous attitude to the impact of this technology on fertility and pregnancy, due to insufficient number of observations. There are several separate descriptions of safe pregnancy and delivery. Despite contraindications for women planning pregnancy, most researchers believe that FUZZ therapy helps to restore female reproductive functions.
Contraindications and complications
FUZZ-ablation of uterine fibroids is indicated if there is symptomatic myomas in women not planning pregnancy, as well as in the eligibility age — from 45 years before menopause.
The use of the method is not recommended when:
- Age less than 18 years of age and a body weight exceeding 110 kg.
- Pregnancy and menopause.
- The presence of extensive skin scarring in the anterior abdominal wall, not allowing to change the angle of impact.
- Excessively close location myoma node to the anterior abdominal wall (danger of burns) or when the distance to the fibroids of more than 12 cm, which does not allow the ultrasound beams to overcome it.
- The size of the uterus more than 20 weeks, and the dominant (primary) node in case of multiple fibroids of the uterus — more than 10 cm, and with the fibroids on the leg.
- The presence of active inflammatory processes in the pelvic organs, endometrial hyperplasia adenomatous nature, dermoid ovarian cysts, intrauterine device, and in the case of the assumption of the possibility of the presence of a malignant tumor.
- Uterine bleeding and after embolization of uterine arteries.
- The active period of General or local infectious process.
- The presence in the patient’s body of metallic implants.
- Intolerance to contrast agents, severe form of claustrophobia.
Serious complications during and after the FUZZ-ablation was observed. There were some cases of complications such as:
- A slight increase in body temperature.
- Light burns the skin of the abdomen (not higher than I degree) and unexpressed inflammation in this area.
- The abundant and prolonged menstrual bleeding.
- Of dyspeptic symptoms.
- Pain in the lumbar, sacral and gluteal areas, in the upper and middle sections of the hips, the resulting thermal effects on the roots of the sciatic nerve and require analgesics (average 10%).
Any methods of treatment have their positive and negative sides or flaws. To last when using the FUZZ-ablation include the duration of the procedure, possibility of recurrence, the persistence of intact segments, the dependence of the effect on the histological structure of fibroids, the high cost of the procedures.
At the same time, this method can be an alternative for surgical methods of treatment and uterine artery embolization.