Treatment of Uterine Fibroids With Magnetic Resonance Guided High Intensity Focused Ultrasound

Inclusion Criteria:

• Women aged 18 to 50 years

• Weight <140kg

• Pre or perimenopausal

• Uterine size <24 weeks

• Cervical screen by Pap test: Normal, Low Grade Squamous Intraepithelial Lesion, orAtypical Squamous Cells of Undetermined Significance as per Cancer Care Ontarioguidelines

• Transformed symptom severity score ≥40

• Willing to attend all study visits

• Willing to complete evaluation forms

• Willing and able to use reliable contraception; MR-HIFU Criteria Trial Arm 1:

• Minimum of 50% of fibroid volume accessible for treatment

• Dominant fibroid ≤8 cm

• Uterine volume <900 cc

• Total fibroid treatment volume <250 cc

• No more than 5 fibroids planned for ablation

• Completely non-enhancing fibroids should not be treated MR-HIFU Criteria Trial Arm 2:

• Minimum of 50% of fibroid volume accessible for treatment

• Dominant fibroid >8 cm or uterine volume >900 cc

• Total fibroid treatment volume <250 cc

• No more than 5 fibroids planned for ablation

• Completely non-enhancing fibroids should not be treated

Exclusion Criteria:

• Other pelvic disease (endometriosis, ovarian tumor, acute pelvic disease, other mass)

• Significant systemic disease even if well controlled

• Positive pregnancy test

• Abnormal uterine bleeding (participant can be included if an endometrial biopsyconfirms no hyperplasia or malignancy in the past 6 months)

• Extensive scarring along anterior abdominal wall (>50% of area)

• Surgical clips or scar tissue in the path of the MR-HIFU beam

• MRI contraindicated according to standard operating procedure

• MRI contrast contraindicated (including renal insufficiency)

• Calcifications around or throughout uterine tissues

• Fibroids not quantifiable on MRI

• Highly perfused or brighter than myometrium in T2-weighted MRI fibroids (Type 3fibroids).