Introduction

Hysterectomy used to be the standard treatment for women with symptomatic fibroids of the uterus. In recent years, other options have become available including surgical uterine sparing treatments, such as myomectomy, medical therapies, such as GnRH-agonists, or selective steroid receptor modulators [1–4]. Radiological interventional alternative treatments are magnetic resonance-guided focused ultrasound surgery (MRgFUS) and uterine artery embolization (UAE).

MRgFUS is an essentially noninvasive technique that induces coagulation necrosis within the fibroid [5–8]. UAE is a minimally invasive technique that causes fibroids to undergo infarction by blocking off their blood supply [9, 10]. Both MRgFUS and UAE are considered safe and effective treatment options for women with symptomatic uterine fibroids [11–18].

Limited technical eligibility for MRgFUS is described as disadvantage of this treatment in small sample sizes [19]. Eligibility for MRgFUS can be affected by the presence of other diseases, location of the fibroid within the pelvis as well as its relationship to close-by anatomical structures [20].

At our department more than 10 years of experience with MRgFUS and UAE exist.

We designed this retrospective study in which we included all women with symptomatic fibroids who applied for UAE at our institution and underwent MRI as part of their pretherapeutic diagnostic workup to evaluate the technical eligibility for MRgFUS in a large cohort. The pretherapeutic MRI datasets were used to determine technical eligibility for MRgFUS treatment. In addition, we compared the technical eligibility for MRgFUS and UAE and identified the most common reasons for technical ineligibility for MRgFUS treatment.

Materials and Methods

Study Population

The institutional review board approved the entire study. Each woman gave written, informed consent for the examination and study participation. All included women were older than 18 years, premenopausal, had symptomatic fibroids, applying for UAE at our institution between 2001 and 2012, and underwent MRI at baseline. All women had finished family planning. Women with contraindications to MRI examination or MR contrast agent administration were excluded. Before analyzing technical eligibility for MRgFUS, we excluded women with other pathologies than fibroids in baseline MRI and women without or with incomplete MRI data.

Study Endpoint

Primary study endpoint was defined as technical eligibility for MRgFUS treatment of women applying for UAE based on MRI criteria without mitigation technique. Secondary outcome was defined as the most frequent exclusion criteria for MRgFUS treatment and differences in technical eligibility for MRgFUS and UAE treatment.

Technical Eligibility for MRgFUS Treatment

Women applying for UAE were assessed retrospectively for technical eligibility for MRgFUS treatment based on preinterventional MRI criteria according to the U.S. Food and Drug Administration (FDA) approvals. The MRI criteria for technical ineligibility for MRgFUS are summarized in Table 1.

Table 1 Absolute and relative contraindications for technical ineligibility for MRgFUS treatment on basis of MRI criteria
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The baseline MRI data sets originally obtained to evaluate women before UAE were retrospectively reanalyzed by two radiologists in consensus to determine whether these women were technically eligible for MRgFUS. One was a senior reader with more than 10 years of experience in MRgFUS and the other a junior reader with <5 years of experience in MRgFUS. In each case, all reasons for technical ineligibility for MRgFUS treatment were recorded, meaning that multiple entries per patient were possible. Technical eligibility was defined for one MRgFUS treatment session, the possibility of multiple treatments was not considered. Further repetitive treatments and mitigation techniques also were not considered.

Technical Eligibility for UAE

UAE could be conduct in women applying for UAE with respect to the following contraindications: suspected uterine malignancy, active pelvic infection, a large pedunculated subserosal fibroid with a pedicle <50 % of total fibroid diameter, aberrant vessel supply, and fibroids with complete autoinfarction. Additional contraindications for UAE were contraindications to iodinated contrast agent, such as renal failure, manifest hyperthyroidism, or uncorrectable coagulopathy.

Baseline MRI

Baseline MRI was performed at 1.5 T (Signa, General Electric Medical Systems, Milwaukee, WI or Magnetom Symphony, Siemens Medical Systems, Erlangen Germany). After an initial localizer scan, T1-weighted and T2-weighted sequences in three orthogonal planes as well as post-contrast, fat-saturated T1-weighted sequences with administration of gadolinium-based contrast medium at a dose of 0.1 mmol/kg body weight were acquired.

Statistical Analysis

Demographic data are given with median and range or upper and lower quartiles (25th and 75th percentile). Technical eligibility for both treatments was compared using the McNemar test for paired samples. Statistical significance was accepted at P < 0.05. Statistical analysis was performed using the SPSS software package (SPSS 20.0.0.; SPSS Corporation, Chicago, IL).

Results

Patient Population

From July 2001 to July 2012, a total of 783 women applied for UAE at our institution. Seventy-three women could not be included in the study due to uterine pathology other than fibroids (n = 24) or missing MRI data (n = 49). Other pathologies than uterine fibroids diagnosed on baseline MRI in women applying for UAE are listed in Table 2. Seven hundred and ten women with symptomatic fibroids were included in the retrospective analysis of technical eligibility for MRgFUS treatment. Figure 1 presents a flow diagram of the patient selection procedure based on our exclusion criteria. The women finally included in the retrospective analysis had a median age of 44.2 years (25th–75th percentiles: 41.3–47.4 years).

Table 2 Pathologies other than uterine fibroids diagnosed on baseline MRI in women with fibroid-like symptoms applying for UAE
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Fig. 1
figure 1

Flow diagram of patient selection for the retrospective analysis of technical eligibility for MRgFUS

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Technical Eligibility for MRgFUS

Women with other diagnosis than fibroids (n = 24) or missing MRI data (n = 49) were excluded from further analysis.

Primary outcome was defined as technical eligibility for MRgFUS treatment, which was the case in 276 of 710 (38.9 %) of the women based on MRI criteria. In 434 of 710 (61.1 %) of the women who applied for UAE, MRgFUS treatment would not have been possible. The reasons for MRgFUS ineligibility were as follows (multiple reasons possible; Fig. 2): bowel interposition in the ultrasound beam path, 262/434 (60.4 %) (Fig. 3); >5 fibroids, 205/434 (47.3 %; Fig. 4); distance from the fibroid to the sacral bone surface, 110/434 (25.3 %); fibroid size/shape or uterus size, 70/434 (16.1 %; Fig. 5); severe concomitant adenomyosis, 18/434 (4.2 %). There were no women who were ineligible because of aberrant vessels, extensive cutaneous scars, or foreign material in the ultrasound beam path. In 254 cases, there was only one reason for MRgFUS ineligibility, in 268 cases two reasons, in 123 cases three reasons, and in 20 cases four reasons.

Fig. 2
figure 2

Reasons for technical ineligibility for MRgFUS treatment

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Fig. 3
figure 3

Technical ineligibility for MRgFUS treatment of two intramural fibroids in a retroflected uterus due to bowel interposition in the ultrasound beam path in T2-weighted MR image at baseline

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Fig. 4
figure 4

Technical ineligibility for MRgFUS treatment due to the presence of multiple myomata. Four fibroids are shown on this single T2-weighted MR image at baseline

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Fig. 5
figure 5

Technical ineligibility for MRgFUS treatment due to large fibroid size in a T2-weighted MR image at baseline

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Technical Eligibility for UAE

Women with other diagnosis than fibroids (n = 24) or missing MRI data (n = 49) were excluded from further analysis.

Technical eligibility for UAE was not given in 6/710 (0.8 %) of the women due to the following reasons: complete autoinfarcted fibroids in four of six women, fibroid shape (a large pedunculated subserosal fibroid with a pedicle <50 % of total fibroid volume) in one of six women, and aberrant vessel supply in one of six women.

Comparison of Technical Eligibility for MRgFUS and UAE

Comparison of technical eligibility for MRgFUS and UAE showed a significantly lower feasibility for MRgFUS (38.9 %) versus UAE (99.2 %; P < 0.001) based on MRI criteria.

Discussion

MRgFUS is a noninvasive, safe, and effective technique, which technical eligibility is described as limited. However, this statement is based on studies with a small number of included patients [19]. In this study, we wanted to verify this result in a larger cohort. We retrospectively evaluated the technical eligibility for MRgFUS treatment of women with symptomatic uterine fibroids who applied for UAE. The evaluation was based on MRI criteria in accordance to the U.S. FDA approvals using baseline MRI data sets obtained before UAE. As secondary endpoint, the reasons for technical ineligibility for MRgFUS treatment and differences in technical eligibility for MRgFUS and UAE treatment were identified.

Based on MRI criteria, 276 of 710 (38.9 %) of women with symptomatic uterine fibroids who applied for UAE were technically eligible for MRgFUS treatment. On the one hand, this rate is in agreement with eligibility rates published in the literature, such as in the publication of O’Sullivan et al. [21] who estimated a rate of 35 % for MRgFUS eligibility based on data from InSightec (Tirat Carmel, Israel). On the other hand, it is in opposite of data given in the literature, such as Behera et al. [19] who classified 16 % (27/169) of women as clinically and anatomically eligible for MRgFUS treatment based on MRI. Zaher et al. [22] used GnRH analogue treatment or bowel mitigation techniques before MRgFUS treatment, which resulted in a considerably higher eligibility rate of 74 % (74/100). These seem to be promising results for widening MRgFUS eligibility by fibroid shrinkage due to preinterventional GnRH analogue use and bowel interposition reduction. Further opportunities to widen technical eligibility for MRgFUS could be multiple treatment planning, which offers the opportunity to treat a greater total fibroid volume or treatment of selected fibroids, which are suspected to be responsible for the clinical symptoms.

The most frequent reasons for technical ineligibility in our study were bowel interposition in the ultrasound beam path (60.4 %), >5 fibroids (47.3 %), distance from the fibroid to the sacral bone surface (25.3 %), fibroid size/shape or uterus size (16.1 %), and severe concomitant adenomyosis (4.2 %).

Because we found the presence of bowel in the ultrasound beam path to be the most common reason for technical ineligibility of MRgFUS, it is recommended to use bowel mitigation techniques so that MRgFUS can be used in more women.

Zhang et al. [23] was able to treat more women with MRgFUS using a degassed water balloon for bowel compression and Zaher et al. [22] also could widen MRgFUS eligibility by bowel mitigation techniques. Other investigators found it helpful to manipulate uterus position by means of bladder or rectal filling [20]. MRI in prone position for MRgFUS treatment planning may be helpful to improve estimation of technical eligibility of MRgFUS with mitigation technique.

A limitation of this study is that the technical eligibility for MRgFUS was assessed retrospectively based solely on MRI criteria. Clinical eligibility for MRgFUS treatment was not considered. Also no mitigation techniques or multiple treatment sessions of MRgFUS were considered.

Our results suggest that up to 40 % of women with symptomatic fibroids are technically eligible for MRgFUS treatment. Hence, technical eligibility for MRgFUS is significantly lower than for UAE. Because bowel interposition in the ultrasound beam path is the most common reason precluding MRgFUS, mitigation techniques should be evaluated in further studies to enable more women with symptomatic uterine fibroids MRgFUS treatment.