Sacral injury and influencing factors after ultrasonic ablation of uterine fibroids ≤30 mm from the sacrum

Abstract

To study sacral injuries and influencing factors after ultrasonic ablation of uterine fibroids no more than 30 mm from the sacrum. METHODSA total of 406 patients with uterine fibroids who underwent percutaneous ultrasound ablation were analyzed retrospectively. All patients underwent contrast-enhanced magnetic resonance imaging (MRI) scans before and after high-intensity focused ultrasound. The abnormal signal intensity (low signal intensity on T1WI and high signal intensity on T2WI) on the postoperative MRIs was indicative of a sacral injury. The patients were divided into a sacrum injury group and a sacrum non-injury group. The relationship between fibroid characteristics, ultrasound ablation parameters, and injury was analyzed using univariate and multivariate analyses. RESULTSThere were 139 cases of sacral injury (34.24%). When the distance from the fibroid's dorsal side to the sacrum was 0-10 mm, the risk assessment showed that the danger of sacral injury increased by 1.85 times and 3.03 times compared with that at a distance of 11-20 or 21-30 mm. Furthermore, the risk of sacral injury increased by 1.89 times and 3.23 times when the therapeutic dose (TD) of a fibroid was >500 KJ compared with that of a fibroid with TD= 250-500 KJ and <250 KJ. CONCLUSIONA distance of 10 mm or less and a TD of >500 KJ were significantly correlated with sacral injury. The distance from the fibroid's dorsal side to the sacrum and the TD were the main causes of injury to the sacrum. A distance of 10 mm or less and a TD of >500 KJ carried higher injury risks, while a distance of 21-30 mm and a TD of <250 KJ were the most appropriate circumstances to reduce the risk of sacral injury.

Factors influencing magnetic resonance imaging changes associated with pelvic bone injury after high-intensity focused ultrasound ablation of uterine fibroids: a retrospective case-control study

“…Despite its clinical significance, to the best of our knowledge, no study has specifically assessed the entire pelvis for bone damage using MRI after HIFU over a patient sample of comparable size. Previously, a few studies investigated the postoperative sacral injury with imaging changes and analyzed the factors influencing them ( 9 - 11 ). Moreover, assessing bone injury with CE-MRI provides an objective image-based endpoint.…”

“…As a thermal ablation technique, any factor that affects energy deposition in the target area can have an impact on the therapeutic efficiency of HIFU. To reduce the risk of postoperative pelvic injury, patients should be adequately evaluated preoperatively to select suitable patients for treatment; the geometric focus of ultrasound should be as far forward as possible without being too close to sensitive soft tissue structures or the sacrum, pubis, or other bony structures where safety margins discussed in the literature in terms of bony structures include distances ranging from 21 to 30 mm ( 11 , 31 , 32 ). In addition, to reduce the distance between the fibroid and the transducer, a number of other techniques can be used clinically to achieve the goal, such as filling the rectum with water to push the target fibroid forward, or tilting the beam path to control the heat distribution in the far field.…”