MRI Features And Clinical Value In High Intensity Focused Ultrasound Ablation Of Abdominal Wall Endometriosis

Background:Abdominal wall endometriosis (AWE) is defined as endometrial tissue that is superficial to the peritoneum. Due to the low overall incidence, to our best knowledge, several reports using MR imaging in AWE, have been described in the literature. AWE is a rare occurrence in malignant transformation, and in this condition, it is comparatively uncommon to see the MR images of adenocarcinoma arising from AWE.As far as we know, there has been several reports of AWE with HIFU ablation by far, which demonstrates that HIFU has curative effect for AWE, the integrity of the abdominal wall could be preserved, and leaves no scar on the skin. However, as HIFU ablation is an invasive therapy method, we cannot get the postoperative pathological diagnosis, so the lesion location, size and the depth of invasion of AWE is crucial for complete HIFU ablation. In addition, it is extremely important to have the fully understanding of the nature of the AWE lesion preoperatively.Of all the current imaging techniques, MRI not only can provide noninvasive imaging in any directions, but also has good soft tissue resolution at the same time. Thus, MRI imaging seems to be useful in determining the location, size, concurrent change and depth of infiltration in surrounding tissue preoperatively. And the postoperative MRI seems to be useful in therapeutic evaluation and prognosis evaluation after HIFU ablation.Objective:The purpose of this study was to explore the clinical value of MRI in the treatment of AWE with US-guided HIFU ablation by analyzing the MRI findings of AWE pre and post HIFU ablation.Methods:1. A retrospective analysis was made on the clinical materials and pelvic MRI of 30 patients, including a recurrent adenocarcinoma arising from AWE in 1 case, referred for HIFU treatment. Analyze the MRI characteristics of AWE on Tl-weighted and T2-weighted images as well as enhanced sequences.2. Assessed the ablation rate with the enhanced MRI scan pre and post HIFU treatment of AWE lesions in 27 cases, and then evaluated the the clinical value of MRI in treatment outcomes and prognosis post HIFU ablation.3. Analyzed the imaging features of AWE lesions on diffuse weighted imaging (DWI) sequence, and explored the pathological outcomes by comparing the ADC values in 17 cases pre and post HIFU treatment.Results:l.This study presented 30 lesions in 29 patients, MRI findings showed the location among the 30 AWE lesions:4 lesions were in subcutaneous adipose tissue,15 lesions were in the rectus abdominis and anterior rectus sheath, and 10 lesions were infiltrating the posterior rectus sheath.2.29 cases (30 lesions in total):On T2-weighted MR imaging 26 lesions appeared iso-intense or slightly hypo-intense compared with skeletal muscle, with small foci of high intensity or ringlike high intensity. On T1-weighted imaging 16 lesions showed iso-intense or slightly hyper-intense compared with skeletal muscle, with small foci of high intensity. The lesions appeared relatively clear on post -contrast T1-weighted images,25 lesions were significantly enhanced, the other 5 lesions showed cricoid enhancement or inhomogeneous enhancement.3.The post-operatively MR images of a recurrent adenocarcinoma arising from AWE in 1 case showed multiple nodules and masses in the left anterior abdominal wall, beside the abdominal aorta, in the left psoas and left inguinal region with ill-defined margins. The appearance of the lesions showed hyper-intensity on T2-weighted fat-suppressed images and iso-intensity on T1-weighted fat-suppressed images. The lesions appeared significantly enhancement or ringlike enhancement, and showed significantly high signal on the DWI sequence, mean ADC value of the lesions was (1.28±0.16) x10-3mm2/s.4. Eventually,27 cases (27 lesions in total) underwent MRI examination after HIFU ablation,2 lesions showed iso-intense signal, while 25 lesions were high or slightly high signal on T1-weighted images; 21 lesions showed hypo-intensity or mixed signals, and 6 lesions were slightly high signal on T2-weighted images; 25 lesions showed annular enhancement and had no contrast agent perfusion in the middle of the lesion, and 2 lesions were significantly enhanced.5.Mean ADC value of 17 AWE lesions was (1.46±0.30)x10-3mm2/s preoperatively, and it was (1.87±0.37)x10-3mm2/s post HIFU treatment. ADC values were higher postoperatively, with significant differences in statistics(P<0.05).Conclusions:1. MRI is a useful technique for demonstrating the location, size and concurrent changes in AWE, which shows great value in diagnosis and preoperative localization for HIFU treatment.2. Postoperative MRI can not only prompt postoperative pathology outcome, but also can make great use in effect evaluation and prognosis after HIFU ablation.