A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies

Abstract

Purpose Treating uterine fibroids with less invasive therapies such as magnetic resonance‐guided focused ultrasound (MRgFUS) is an attractive alternative to surgery. Treatment planning can improve MRgFUS procedures and reduce treatment times, but the tissue properties that currently inform treatment planning tools are not adequate. This study aims to develop an ex vivo uterine fibroid model that can emulate the in vivo environment allowing for characterization of the uterus and fibroid MR, acoustic, and thermal tissue properties while maintaining viability for the necessary postsurgical histopathological assessments. Methods Women undergoing a hysterectomy due to fibroid‐related symptoms were invited to undergo a preoperative pelvic MRI and to permit postoperative testing of their uterine specimen. Patients that declined or could not be scheduled for a pre‐operative MRI were still able to allow post‐operative testing of their excised tissue. Following surgical removal of the uterus, nonmorcellated tissues were reperfused with a Krebs‐Henseleit buffer solution. An MR‐compatible perfusion system was designed to maintain tissue viability inside the MR suite during scanning. MR imaging protocols utilized preoperatively were repeated on whole sample, reperfused ex vivo uterus specimens. Thermal properties including thermal diffusivity and thermal conductivity of the uterus and fibroids were determined using an invasive needle sensor device in 50% of the specimens. Acoustic property measurements (density, speed of sound and attenuation) were obtained for approximately 20% of the tissue samples using both through‐transmission and radiation force balance techniques. Differences between fibroid and uterus and in vivo and ex vivo measurements were evaluated with a two‐tailed Student t test. Results Fourteen patients participated in the study and measurements were obtained from 22 unique fibroids. Of the 16 fibroids available for preoperative MRI testing, 69% demonstrated classic hypo‐intensity relative to the myometrium, with the remainder presenting with iso‐ (25%) or hyper‐intensity (6%). While thermal diffusivity was not significantly different between fibroid and myometrium tissues (0.217 ± 0.047 and 0.204 ± 0.039 mm2/s, respectively), the acoustic attenuation in fibroid tissue was significantly higher than myometrium (0.092 ± 0.021 and 0.052 ± 0.023 Np/cm/MHz, respectively). When comparing in vivo with ex vivo MRI T1 and T2 measurements in fibroids and myometrium tissue, the only difference was found in the fibroid T2 property (P < 0.05). Finally, the developed perfusion protocol successfully maintained tissue viability in ex vivo tissues as evaluated through histological analysis. Conclusions This study developed an MR‐compatible extracorporeal perfusion technique that effectively maintains tissue viability, allowing for the direct measurement of patient‐specific MR, thermal, and acoustic property values for both fibroid and myometrium tissues. These measured tissue property values will enable further development and...

Efficacy, Complications, and Factors Predictive of Response to Treatment with Transvaginal Radiofrequency Ablation for Symptomatic Uterine Myomas

“…We believe this association can be explained in part by the nature of radiofrequency treatment with ultrasonographic visualization. During ablation, radiofrequency is applied until the ultrasound images show changes in the appearance of the myoma, that could take longer to become apparent in fibroids that are larger or have specific characteristics such as greater fibrosis [22][23][24][25] Among the complications observed in the present study, the single case of intestinal heat injury stands out. This complication, although foreseeable given the nature of radiofrequency treatment, has not been reported previously to date [26].…”

Application Effect of Laparoscopic Myomectomy and Comprehensive Rehabilitation Nursing on Patients with Uterine Fibroids

“…By guiding the patient to take a comfortable position, relax the abdominal muscle, chat, watch TV and other methods to distract attention, in order to alleviate pain. Severe pain can be given analgesics according to the doctor' s advice, so that patients with postoperative pain greatly reduced [21][22][23].…”

Comparison of computer simulations and clinical treatment results of magnetic resonance‐guided focused ultrasound surgery (MRgFUS) of uterine fibroids

“…24 However, a small number of quantitative estimates of in vivo UF perfusion are available in the literature including a feasibility study using an analytic technique 25 and a study involving one patient case exhibiting low clinical heating. 26 Similarly, ex vivo estimates of UF attenuation are available in several studies, [27][28][29] (while in vivo values remain scarce in the literature). 30,31 By gaining information about the particular patient-specific tissue parameters that limit and hinder the heating of a fibroid during a particular sonication, it could be possible to select more optimal sonication parameters for such a sonication.…”