0444

Microcirculatory changes in the uterus of women during the menstrual cycle - based on intravoxel incoherent motion MRI
Yajie Li1,2, Qi Zhang2, Caixia Fu3, Qing Li4, and Robert Grimm5
1Shanghai Institute of Medical Imaging, Shanghai, China, 2Department of Radiology, Huashan Hospital, Shanghai, China, 3MR Application Development, Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China, 4MR Collaborations, Siemens Healthineers Digital Technology (Shanghai) Co., Ltd., Shanghai, China, 5MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany

Synopsis

Keywords: Uterus, Diffusion/other diffusion imaging techniques, Intravoxel incoherent motion, Microcirculation, Perfusion

Purpose: To assess the feasibility of intravoxel incoherent motion MRI on detecting the microcirculatory changes in the uterus of women during the menstrual cycle.

Methods: Volunteers underwent MRI scans by using IVIM. The changes of D value, D* and f value of three layers of uterine structure during menstrual cycle were analyzed quantitatively.

Results: During menstrual cycle, the D values of junctional zone were significantly lower than in myometrium. Meanwhile, the f values of the three zones structure of uterus were significantly different.

Conclusion: IVIM can be used for noninvasive and quantitative evaluation of uterine blood microcirculation changes.

Introduction

The physiology of the uterus changes periodically under the influence of hormones (1,2). Traditional magnetic resonance imaging (MRI) focuses on evaluating the structure of the uterus, while the intravoxel incoherent motion (IVIM) can reflect the blood microcirculation (3–5). The purpose of this study is to assess the feasibility of intravoxel incoherent motion MRI on detecting the microcirculatory changes in the uterus of women during the menstrual cycle.

Methods and Materials

Twenty-one young female volunteers (age range: 23-32 years, mean age: 26.1 years) with regular menstrual cycles (28±7days) were recruited in this study. Volunteers with significant dysmenorrhea, a history of gynecologic disorders, contraceptive use in the past six months, and contraindications to MRI were excluded from the study. Each participant was scanned during menstruation phase (first three days of menstruation), ovulatory phase (two days before and after the expected date of ovulation day), and luteal phase (seven days before the next menstruation) (Fig.1).
MRI was performed with a 3T scanner (MAGNETOM Prisma; Siemens Healthcare, Erlangen, Germany) with an 18-channel phase array body coil. IVIM was acquired with a single-shot ZOOMit spin-echo echo-planar imaging (SE-EPI) sequence along the axis of the uterus corpus. Scanning parameters for IVIM MR imaging were as follows: TR= 3200 msec, TE=65mesc, FOV= 200*200mm, Slice thickness= 5.0mm, Slice number= 15, Bandwidth= 1666Hz/Pixel, diffusion directions=3, twelve b values (0, 10, 20, 30, 50, 70, 100, 150, 200, 400, 800, 1000s/mm2).
All IVIM parameters were calculated by using a post-processing research application (Body Diffusion Toolbox, Siemens Healthcare, Erlangen, Germany). Manual-shaped regions of interest (ROIs) were defined respectively within endometrium, junctional zone and myometrium in the regions with a good-fitting curve. The two radiologists blinded to the menstrual cycle of volunteers performed the analysis on the diffusion coefficient (D), pseudo diffusion coefficient (D*), and perfusion fraction (f).
Statistical analysis was performed with IBM Statistical SPSS® v. 22.0(SSPS Inc., Chicago, IL). Difference among three zonal during the menstrual cycle was evaluated using one-way analysis of variance (ANOVA).

Results

Three volunteers were excluded because of the presence of uterus leiomyomas. Therefore, a total of 18 female participants were recruited in our investigate cohort. Curve fitting results showed that the IVIM model fitted the data well (Fig. 2).
The mean D, D* and f values of each uterine zone during menstrual cycle are listed in Table 1. The D values of three zonal structures of uterine in ovulation and luteal phases were significantly higher than that in menstrual phase, and the difference was statistically significant (P＜0.05). In comparison to the menstrual phase, the f value of endometrium was much lower during the luteal phase (P=0.004).
The P values of IVIM-related parameters between different layers of uterus in the same menstrual cycle are showed in Table 2. In each phase of menstrual cycle, the D value of the junctional zone was significantly lower than that of the myometrium, with statistical significance (P＜0.001). During ovulation and luteal phase, the D value of the junctional zone was also lower than that of the endometrium (P＜0.001) (Fig 3). The f value of myometrium was significantly higher than that of endometrium and junctional zone during ovulation and luteal phase (P＜0.013).

Discussion

The mean D value in each zonal structure of uterine in menstrual phase was significantly lower than those in other phases of menstrual cycle, which indicated that the diffusion of water molecules in the uterine during menstruation was limited. Periodic contractions of the spiral artery walls during the menstrual phase result in disruption of the epithelium and blood vessel rupture, which cause restricted diffusion by three layers of the uterus (6,7). D values within junctional zone were significantly lower than those within the myometrium during every menstrual phase. It is possible that the junctional zone is a structure consisting of compact smooth muscle bundles, which can reduce the water molecule content, the extracellular space, the cytoplasmic nucleus ratio, and the arrangement of myocytes (8).
D* is the diffusion coefficient associated with capillary perfusion, which depends on the average blood flow velocity of the capillary (4,9). However, there was no significant difference in D* values in the structure of each layer of uterus during the menstrual cycle. Signal attenuation measured by DWI with low b value mainly reflects perfusion effect (10,11). However, lower b values may result in sensitivity to noise, which will lead to the reduction of SNR of the D* maps (12,13).
In the present study, f values of myometrium were significantly higher than junctional zone and endometrium during ovulatory phase and luteal phase. Meanwhile, f values of junctional zone were also higher than endometrium during luteal phase. We assume that because the circumferential arcuate arteries are developed when the bilateral uterine arteries enter the myometrium, these arteries sequentially branch to form the radial arteries and perforate the endometrium as small-caliber conductance vessels (14).
IVIM, a non-invasive quantitative imaging method, can be used to obtain the changes in the blood microcirculation in each layer of the uterus during the menstrual cycle. The study of the parameters related to normal uterine IVIM is helpful to analyze the indicators under abnormal conditions.

Acknowledgements

We would like to thank all the volunteers for their contributions to this study.

References

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Figures

Figure 1 MR scans in the temporal line with different phases of the menstrual cycle. The menstrual cycle consists of menstrual (MP), follicular (FP), ovulation (OP) and luteal phases (LP). Each volunteer underwent three MR scans among the menstrual cycle including MP, OP and LP. The “scan” box represented the scanning period of each volunteer.

Figure 2 A 26-year-old volunteer in luteal phase. (a) Square selection box was drawn on IVIM map images of uterus in myometrium. (b) The green line shows the IVIM curve of the standard model, and the red line represents the real measurement. The standard and measured IVIM curves indicate good fit.

Figure 3 The D values within different zones of the uterus during the menstrual cycle. In each phase, the D value of the junctional zone was significantly lower than that of the myometrium. In addition to the menstrual phase, the D value of the junctional zone was lower than that of the endometrium in the other two phases. EM, endometrium; JZ, junctional zone; MY, myometrium; * *P<0.01, ***P<0.001.

Table 1 The mean D, D* and f value in each zonal structure of the uterus during the menstrual cycle. EM, endometrium; JZ, junctional zone; MY, myometrium; MP, menstrual phase; OP, ovulatory phase; LP, luteal phase. The unit of D* and D value are 10−3 mm2 /s, f value has no units.

Table 2 The P values of D, D* and f values in each phase of the menstrual cycle within every zonal structure of the uterus. EM, endometrium; JZ, junctional zone; MY, myometrium; MP, menstrual phase; OP, ovulatory phase; LP, luteal phase.

Proc. Intl. Soc. Mag. Reson. Med. 31 (2023)
0444
DOI: https://doi.org/10.58530/2023/0444