Wedged gel pad for bowel manipulation during MR-guided high-intensity focused ultrasound therapy to treat uterine fibroids: a case report

Abstract

Background: Magnetic resonance guided high-intensity focused ultrasound (MR-HIFU) therapy is not feasible in all patients with uterine fibroids because of limiting anatomical factors such as scar tissue, bowel loops or other obstacles in the sonication path. These may prevent the treatment or limit the treatment window, and therefore, also the volume where HIFU therapy can be delivered. Bowel loops present a particular problem because of bowel gas bubbles and hard particles which may cause reflection or absorption of ultrasound energy, potentially leading to thermal damage and even bowel perforation. Most commonly used techniques for bowel repositioning are bladder and/or rectum filling but these are not always sufficient to reposition the bowel loops. With more efficient bowel repositioning technique, the number of eligible patients for MR-HIFU treatment could be increased, and therapy efficacy 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 symptomatic fibroids undergoing MR-HIFU treatment when bladder and/or rectum filling was not sufficient to reposition the bowel loops. No severe adverse effects were observed in these cases. The non-perfused volume ratios (NPVs) immediately after 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 treatment could be an effective tool to manipulate the bowels in cases where the bladder and/or rectum filling is not sufficient to reposition the bowel loops. A wedged gel pad could also be used in other situations to achieve better treatment coverage to the uterine fibroid.

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

Fig. 1

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

Fig. 2

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

Fig. 3

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

Fig. 4

T2W planning images displayed on the therapy planning console with ultrasound beam view where bowels are presented with red color and target uterine fibroid not accessible with blue color

Fig. 5

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

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%)

Fig. 7

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

Fig. 8

T2W planning images displayed on the therapy console with ultrasound beam view where bowels are presented with red boundary and uterine fibroid with blue boundary

Fig. 9

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

Fig. 10

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