Sainio et al. Journal of Therapeutic Ultrasound (2018) 6:10 https://doi.org/10.1186/s40349-018-0116-4

CASE STUDY Open Access

Wedged gel pad for bowel manipulationduring MR-guided high-intensity focusedultrasound therapy to treat uterine fibroids: acase reportTeija Sainio1,2* , Gaber Komar1, Jani Saunavaara1,2, Visa Suomi1, Kirsi Joronen3, Antti Perheentupa3,Antti Viitala1 and Roberto Blanco Sequeiros1

Abstract

Background: Magnetic resonance guided high-intensity focused ultrasound (MR-HIFU) therapy is not feasible in allpatients with uterine fibroids because of limiting anatomical factors such as scar tissue, bowel loops or other obstaclesin the sonication path. These may prevent the treatment or limit the treatment window, and therefore, also thevolume where HIFU therapy can be delivered. Bowel loops present a particular problem because of bowel gasbubbles and hard particles which may cause reflection or absorption of ultrasound energy, potentially leading tothermal damage and even bowel perforation. Most commonly used techniques for bowel repositioning are bladderand/or rectum filling but these are not always sufficient to reposition the bowel loops. With more efficient bowelrepositioning technique, the number of eligible patients for MR-HIFU treatment could be increased, and therapyefficacy be improved in cases where bowel loops limit the treatment window.

Case presentation: A wedged exterior gel pad was used in two patients presented with in total of four symptomaticfibroids undergoing MR-HIFU treatment when bladder and/or rectum filling was not sufficient to reposition the bowelloops. No severe adverse effects were observed in these cases. The non-perfused volume ratios (NPVs) immediatelyafter treatment were 86% and 39% for the first patient, and 3% for the second patient.

Conclusions: Our preliminary experience suggests that the use of a wedged gel pad during MR-HIFU treatmentcould be an effective tool to manipulate the bowels in cases where the bladder and/or rectum filling is not sufficientto reposition the bowel loops. A wedged gel pad could also be used in other situations to achieve better treatmentcoverage to the uterine fibroid.

Keywords: Gel pad, Uterine fibroid, Bowel repositioning, MR-guided high-intensity focused ultrasound

BackgroundUterine fibroids, also known as leiomyomas or myomas,are the most frequent benign tumors affecting womenin premenopausal age [1, 2]. Uterine fibroids can causesymptoms including severe menorrhea, urinary inconti-nence, dysmenorrhea, and infertility which can have a

*Correspondence: teija.sainio@tyks.fi1Medical Imaging Centre of Southwest Finland, University of Turku and TurkuUniversity Hospital, Turku, Finland2Department of Medical Physics, Division of Medical Imaging, Turku UniversityHospital, Turku, FinlandFull list of author information is available at the end of the article

huge impact to women’s quality of life [3–6]. Current,conventional treatment options for symptomatic uter-ine fibroids are medical, surgical, and uterine arterialembolization (UAE) which can have major side effects orare invasive [6].Magnetic resonance-guided high-intensity focused

ultrasound (MR-HIFU) therapy is a promising nonin-vasive treatment method for uterine fibroids with goodadverse event profile [7]. In MR-HIFU uterine fibroidtherapy the ultrasound waves are focused into the bodytargeting fibroid tissue, to form a localized area of high-intensity ultrasound (HIU), inducing rapid temperature

© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to theCreative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Sainio et al. Journal of Therapeutic Ultrasound (2018) 6:10 Page 2 of 10

elevation. Heat generation is due to absorption of theultrasound waves in tissue, therefore acoustic energyis transformed to heat. Heating the tissue above 57 °Cinduces, e.g., coagulative necrosis and irreversible tissuedamage in seconds, while surrounding tissue remainsviable [8, 9]. At the moment, uterine fibroids are one ofthe most commonly MR-HIFU -treated tumors. In addi-tion, HIFU’s clinical efficacy in the treatment of uterinefibroids has been widely shown [10–15].However, not all patients are suitable for MR-HIFU

therapy. For reasons such as excessively thick subcuta-neous fat layer (> 4 cm), large fibroid (> 10 cm), locationof fibroid (fibroid is too deep, > 10 cm from the skin)or fibroid tissue type is not favorable (Funaki classifi-cation). Funaki et al [16] showed that the efficacy ofMR-HIFU treatment correlates with the signal intensityof T2-weighted magnetic resonance images and classi-fied fibroids into 3 types based on the signal intensity ofT2-weighted magnetic resonance images as follows: type1, low intensity; type 2, intermediate intensity; type 3,high intensity. Funaki type 1 and type 2 fibroids are suit-able candidates for MR-HIFU treatment, whereas type 3fibroids are not.One major factor negatively affecting HIFU treatment

feasibility is bowel loops between the abdominal wall andthe uterine fibroid. Since, the ultrasound beam focus-ing is implemented by a concave ultrasound transducerthat consists of multiple transducer elements. The ultra-sound beam shape is a conical being wider at the base.This conical shape of the beam may present a limitationin the uterine fibroid treatment delivery due to overlyingbowel gas bubbles and hard particles within the lumenwhich may reflect or absorb the ultrasound energy inunpredictable ways. This may potentially lead to unin-tended thermal damage, and at worst, bowel perforationthat requires surgical intervention [17–21]. A safe acousticwindow can be established in some cases with beam shap-ing and/or tilting, or by manipulating bowel loops withbladder and/or rectum filling [22].

Previous studies [17, 18, 23] have reported that 14-74% of patients requesting MR-HIFU are good candi-dates for the treatment, and in 7-13% of cases bowelswere partially or completely obstructing the acoustic win-dow. Usually, the bowel loops can be repositioned withbladder and/or rectum filling but these are not alwayssufficient to reposition the bowel loops [22, 24]. Kimet al. [24] reported that bladder and/or rectum fill-ing technique is not effective in repositioning bowelsin 5% of bowel obstruction cases. With an alternativeor adjuvant bowel repositioning technique, the numberof patients suitable for MR-HIFU treatment could beincreased, and better treatment results could be achievedin cases where the bowel loops limit the treatmentwindow.Hesley et al. [25] reported that in some cases, a con-

vex gel pad was helpful in displacing the bowel loops awayfrom the treatment window during HIFU therapy. How-ever, a disadvantage of the method was that the use of aconvex gel pad resulted in a considerably longer distancebetween the transducer and targeted tissue, limiting thereach of HIFU. The study did not assess the safety and fea-sibility of convex gel pad for bowel displacement duringHIFU therapy.The purpose of this case report is 1) to introduce a novel

way of repositioning the bowel loops positioned betweenthe abdominal wall and the uterine fibroid by using awedge shaped gel pad, and 2) to discuss the potential ben-efits and drawbacks of this technique from the aspect ofsafety and feasibility.

Case presentationMaterials andmethodsPatients were recruited to our clinical trial (clinicaltri-als.gov identifier NCT02914704) based on their wishnot to undergo surgical treatment among other criteria.Patients underwent MR imaging protocols for screen-ing, HIFU therapy, and 3-month follow-up as shown inTable 1.

Table 1 MRI imaging protocols for screening, HIFU therapy and 3-month follow-up

Examination Sequence type Purpose Imaging plane TR (ms) TE (ms) FA (°) Section thickness (mm) FOV (mm)

Screening T2W TSE Uterine fibroid Sagittal 4844 95 90 3 240x240T2W TSE Uterine fibroid Axial 3845 80 90 4 300x300T1W Uterine fibroid Sagittal 5.2 2.6 7 3 345x250DWI Uterine fibroid Axial 3733 83 90 5 375x290CE-T1W Uterine fibroid Sagittal 5.2 2.6 7 3 345x250

Treatment FFE Air bubble assessment Coronal 15 12 10 2 280x280T2W TSE Treatment planning Sagittal 1550 150 90 1.6 250x250FFE-EPI Temperature monitoring Coronal/Sagittal 37 19.5 19 7 400x400CE-T1W Non-perfused volume Coronal 5.2 2.6 7 3 345x250

3-month follow-up T2W TSE Uterine fibroid volume Sagittal 4844 95 90 3 240x240T2W TSE Uterine fibroid volume Axial 3845 80 90 4 300x300CE-T1W Non-perfused volume Sagittal 5.2 2.6 7 3 345x250

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HIFU therapy was performed using an extracorpo-real, clinical tabletop MR-HIFU system (Sonalleve V2MR-HIFU system, Profound Medical Inc., Mississauga,Canada) in combination with a 3.0 T clinical MR scan-ner (Ingenia, Philips Healthcare, Best, The Netherlands).Immediately prior to the therapy, lower abdomen wasdepilated and a Foley catheter was inserted. Premedi-cation (1 g paracetamol, 800 mg ibuprofen and 5 mgdiazepam) was administered to reduce possible pain anddiscomfort during the treatment. The patient was posi-tioned on the Sonalleve table in prone position and acous-tic coupling between skin and the device was achievedwith degassed and deionized water. The Sonalleve tablewas then advanced into the magnet bore and 3D T2-weighted TSE images were acquired and transferred totherapy delivery console for treatment planning. Basedon these images, a safe sonication path was ensured byexcluding any interleaving bowel loops or, if necessary, byrepositioning them.In case of bowel obstruction our protocol is 1) blad-

der filling (till discomfort) 2) rectum filling if necessary 3)bladder emptying. At each point we try to establish suf-ficient coverage (> 50% of the fibroid) to the fibroid withbeam shaping or tilting. Due to natural limitations of thesetechniques, we are sometimes forced to apply the hereindescribed wedged gel pad and in some cases also vagi-nal pessary in order to improve the position of the uterinecervix.We have used wedged gel pad in total of three casesand have achieved a satisfactory reposition of the bowelloops in all three cases.A gel pad (27.5 × 27.5 × 4.0 cm3, Aquaflex, Parker Lab-

oratories Inc., Germany) was sculpted into wedged shapeusing a sharp, shapeable blade manufactured by our tech-nical division (Fig. 1). With the use of a sharp bladethe cutting surface was smooth preventing air bubbles

getting trapped between the skin and the gel pad. Shap-ing of the gel pad can also be performed with other typeof cutting device that results in a smooth cutting sur-face in order to prevent air pockets created by surfaceirregularities. The sloping edge was placed caudal to thebowels and reached from side to side. The cutting wasdone approximately in 45 degrees angle. Degassed waterwas added between the gel pad and acoustic window, andultrasound gel-water (1:1) solution was added betweenthe gel pad and abdominal skin to ensure good acousticcoupling.The wedged gel pad, due to its shape, creates a force

in the anteroposterior direction as well as in caudocra-nial direction. This increases the pressure in the cranialpart of the lower abdomen (while not affecting the loca-tion of pelvic structures) whereby the bowel loops locatedbetween the uterus and the abdominal wall are displacedin the cranial direction (Fig. 2). The wedged shape not onlyfacilitates this dislocation but also allows for a better sealbetween the gel pad and the skin on the other hand andsmoother transition between the gel pad and the trans-ducer surface eliminating the problem of air bubbles andskin fold.

Case 1A 33-year-old woman of African background with threesymptomatic intramural uterine fibroids in the anteriorwall which caused deformation of the uterine cavity withtwo years of unsuccessful pregnancy attempts. Patienthad previously underwent a laparoscopic enucleation ofuterine fibroid in the posterior wall. The fibroids wereclassified as Funaki type I based on T2W images, andcontrast-enhanced T1W images were assessed. Fibroidsizes were 5.0 × 4.6 × 4.8 cm3, 2.5 × 1.3 × 2.0 cm3, and2.8 × 1.9 × 2.4 cm3 (Fig. 3).

Fig. 1 a) The blade that can be used to modify gel pad and b) produced wedged gel pad on the treatment window

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Fig. 2 A diagrammatic presentation of the anatomy before and after wedged gel pad placement, where a) uterus with myoma, b) US-gel filledrectum, c) saline filled bladder, d) intestines moving within the abdominal cavity, e) abdominal wall and f) gel pad compressing the abdominalcavity, restricting the anterior-posterior space where intestines may move

As demonstrated in Fig. 4, filling the urinary bladder tothe point of discomfort did not achieve the desired results,and despite tilting and shaping of the ultrasound beam,sufficient coverage of the target could not be achieved(Fig. 4).After application of the wedged gel pad, the bowels were

repositioned so that the two target fibroids could be safelysonicated (Fig. 5).Before therapy, good acoustic coupling between the

surfaces was ensured with T1W sequence for detect-ing any air bubbles in the sonication path. The largestfibroid was treated first followed by the smaller fibroid.Good temperature rise was observed, average maximumtemperature per sonication was 76.8 °C (63.8-115.1 °C),in both fibroids. The patient experienced mild pain

during the treatment and opioid pain medication (fen-tanyl, 0.5 μg) was administered. The patient reportedthe gel pad was getting hot during the sonications butno adverse effects were observed due to the treatmentand gel pad usage. This highlighted the importance ofincreased cooling times between sonications. The totaltreatment time from first to last sonication (19 sonica-tions) was 178 min and average treatment power andenergy per sonication were 184 W and 5.3 kJ, respec-tively. Immediately after the treatment contrast-enhancedT1W images were acquired, indicating non-perfused vol-ume ratios (NPVs) of 86% and 39% (Fig. 6). There were noareas of abnormal enhancement within the subcutaneoustissue, and skin was normal after treatment. The vol-ume and shrinkage of the fibroids at 3 months follow-up

Fig. 3 T2W screening images of uterine fibroids (red asterisks) in a) the sagittal and b) axial plane

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Fig. 4 T2W planning images displayed on the therapy planning console with ultrasound beam view where bowels are presented with red color andtarget uterine fibroid not accessible with blue color

were 29 mL and 49%, 5 mL and 2.5% respectively(Fig. 6).

Case 2A 40-year-old woman presented with symptomaticintramural uterine fibroid in posterior wall. The presentedsymptom was severe menorrhea. The fibroid was classi-fied as Funaki type II based on T2W images, and contrast-enhanced T1W images were assessed. Fibroid size was 5.7× 5.0 × 5.0 cm3 (Fig. 7).As demonstrated in Fig. 8, the filling of the urinary blad-

der to the point of discomfort, again did not achieve thedesired results and despite tilting and shaping of the ultra-sound beam, sufficient coverage of the target could not beachieved (Fig. 8).After application of the gel pad, the bowels were reposi-

tioned so that the uterine fibroid could be targeted safely(Fig. 9).Before therapy, good acoustic coupling between sur-

faces was confirmed with T1W sequence to detect anyair bubbles in the sonication path. Despite high power(300 W), a poor temperature rise was observed, averagemaximum temperature per sonication was 56.4 °C (47.3-72.4 °C) in the fibroid. The patient experienced severepain during the treatment and opioid pain medication

(fentanyl, 0.5μg) was administered twice during the treat-ment. The patient reported a sensation of heat on the skinsurface during the sonications and after the treatment theskin looked visually irritated due to the treatment and thegel pad usage. The total treatment time from first to lastsonication (9 sonications) was 155 minutes and averagetreatment power and energy per sonication were 284 Wand 6.8 kJ, respectively. Immediately after the treatment,contrast enhanced T1W images were acquired, showingnon-perfused volume ratio (NPV) of only 3% (Fig. 10). Forthis reason more detail analysis was done after the treat-ment. The conclusion is that the poor treatment resultwas most likely caused by high perfusion in the fibroidwhich prevents the tissue from reaching the thermal abla-tion temperature. This conclusion was reached based ondynamic contrast enhanced images that were obtainedduring the screening MRI. There were no areas of abnor-mal enhancement within the subcutaneous tissue, how-ever there was reddening of the skin which disappearedin few hours. This could be caused by the gel pad as it isfunctioning as an insulator and the cooling effect of directskin cooling device does not reach the skin as effectivelyas without the gel pad. This results in higher tissue tem-peratures which may cause irritation to the skin or evenskin burns if cooling times are not sufficient.Since this is

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Fig. 5 T2W planning images displayed on the therapy planning console with ultrasound beam view after application of wedged gel pad where redcolor boundary is bowels, blue is uterine fibroid, and green is the gel pad

unusual shape of the gel pad in not taken into account bythe software, maybe we should use slightly longer coolingtimes in these cases. Due to poor treatment result patientwas settled on hysterectomy.

DiscussionIn MR-HIFU treatments, unfavorable bowel loop positioncan prevent or limit the treatment window, and there-fore, also the volumewhereHIFU therapy can be delivered

to. Manipulation of the bowel loops with bladder and/orrectum filling can be attempted but these are not alwayssufficient to reposition the bowel loops. Hesley et al. [25]reported that a convex gel pad was helpful in displacingthe bowel loops from the treatment window during HIFUtherapy.In this report, we assess MR-HIFU therapy of two

patients with a total of four symptomatic uterine fibroidswhere bladder and/or rectum filling was not sufficient

Fig. 6 Contrast enhanced T1W images immediately after the treatment (NPVs: 86% and 39%) and at 3-month follow-up (Shrinkages: 49% and 2.5%)

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Fig. 7 T2W screening images of uterine fibroid (red asterisk) in a) the sagittal and b) axial plane

to reposition the bowel loops. Temperature images wereclosely monitored to detect any unwanted heating on thegel pad surface. Longer cooling times were used duringthe gel pad assisted treatments to account for cumulativeheating on the skin, due to gel pad preventing the cool-ing effect to the skin from the direct skin cooling device.The basic principle was that the more power was usedthe longer cooling time was applied. The minor adverse

effects in the second patient with Funaki type II fibroidcould suggest that the use of wedged gel pad is not prefer-able in treating Funaki type III fibroids and that careshould be taken when treating Funaki type II fibroids.However, there were no thermal injuries in the abdominalmuscle or subcutaneous fat layer.Poor treatment result in case two demonstrates that

Funaki classification alone may not be sufficient to predict

Fig. 8 T2W planning images displayed on the therapy console with ultrasound beam view where bowels are presented with red boundary anduterine fibroid with blue boundary

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Fig. 9 T2W planning images displayed on the therapy console with ultrasound beam view after application of wedged gel pad where red boundaryis bowel, blue is uterine fibroid and green is the gel pad

treatment outcome. Particularly in Funaki type II fibroids.In these cases perfusion and diffusion imaging might offeradditional, sometimes crucial, information.Both MR-HIFU therapies were technically successful.

The wedged gel pad in the sonication beam did not seemto reduce the efficacy of the energy delivery to the tar-get, which was expected as the gel pad mostly consistsof water. Due to the asymmetric shape of the gel padin the ultrasound beam path, a slight deformation in the

ultrasound focal point might be induced. However, thepatient-specific ultrasound simulations were conductedand they showed that the use of the wedged gel pad doesnot cause a reduction in the ultrasound peak pressurenor focal point deformation, and therefore, no therapeuticefficacy is lost.The wedged gel pad seems to be able to create a force

in anteroposterior direction which increases the pressurein the lower abdomen displacing bowel loops in cranial

Fig. 10 Contrast enhanced T1W images in a) sagittal and b) axial plane immediately after the treatment (NPV: 3%)

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direction allowing a safe sonication path to the fibroid.Wedged gel pad can therefore be used as an alterna-tive or adjuvant bowel repositioning technique. Using thistechnique the number of patients suitable for MR-HIFUtreatment could be increased, and better treatment resultscould be achieved in cases where bowel loops limit thetreatment window. On the other hand there are also draw-backs related to this technique, for example increasedcumulative heating which can result in skin irritations. Itmight also be more time consuming than bladder and/orrectum filling techniques.Among the limitations of this study have to be men-

tioned the small number of patients and the lack of Funakitype III fibroids, although these type of lesions are typi-cally not well suitable for HIFU therapy [16].

ConclusionsIn conclusion, our experience presented here, suggeststhat the use of wedged gel pad during MR-HIFU treat-ment could be a simple and effective tool to manipulatethe bowels in cases where filling of the bladder is not suf-ficient to create a suitable treatment window. Wedged gelpad could also be beneficial in other situations to achievebetter treatment coverage to the uterine fibroid.

AcknowledgementsNot applicaple.

FundingFinnish Cultural Foundation.

Availability of data andmaterialsThe datasets used and/ analysed during the current study are available fromthe corresponding author on reasonable request.

Authors’ contributionsTS, GK, JS, KJ, AP, VS and RBS have made substantial contributions to theconception and design of the study, acquisition of data, and analysis andinterpretation of data; have been involved in drafting the article; and haveapproved the final version to be published. VS and AV have been involved inrevising it critically for important intellectual content. All authors haveapproved the final version to be published

Ethics approval and consent to participateThis case study was part of Treatment of Benign Uterine Disorders Using HighIntensity Focused Ultrasound (MR-HIFU) trial (clinicaltrials.gov identifierNCT02914704). Local ethics committee approval was obtained from EthicsCommittee, Hospital District of Southwest Finland for the protocol prior tostudy initiation.

Consent for publicationConsents for publication were obtained from all participants.

Competing interestsThe authors declare that they have no competing interests.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.

Author details1Medical Imaging Centre of Southwest Finland, University of Turku and TurkuUniversity Hospital, Turku, Finland. 2Department of Medical Physics, Division ofMedical Imaging, Turku University Hospital, Turku, Finland. 3Department ofObstetrics and Gynecology, Turku University Hospital, Turku, Finland.

Received: 27 July 2018 Accepted: 23 October 2018

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