At first, this study included 68 females, results of 3 of them were excluded as they were not able to complete the study, and so, the final number was 65 females.
Some patients were referred from the Gynecology and Obstetrics Department and others from the Oncology Center.
The study included adult females ≥ 18 years old, participants who agreed to join the study according to the ethical considerations. All females participants were subdivided into 2 groups: Group A (control): 24 females (13 premenopausal females examined during the early proliferative phase of endometrial cycle as the endometrium thickness is the lowest, form 5–7 mm) and (11 asymptomatic postmenopausal females). Inclusion criteria are healthy women with no history of gynecologic diseases or operation. Women using intrauterine contraceptive devices, taking oral contraceptives, or taking hormone replacement therapy were excluded because these are reported to affect uterine appearance on MR. Group B (pathological or diseased): 41 females (11 premenopausal and 30 postmenopausal) patients presented by vaginal bleeding and abnormally thickened endometrium proved by transvaginal (TVS) examination. Also, all premenopausal females were symptomatic and examined in the early proliferative phase of the cycle to ensure that the thickened endometrium is pathological and not related to menstrual phases.
Virgins, pregnant women, females with general contraindication to MRI scanning, and patients underwent previous pelvic surgery or exposed to pelvic radio or chemotherapy were excluded in both groups.
The collected data was correlated to the histopathological results (as the gold standard) in cases of endometrial pathologies.
The examination was done at the Diagnostic Radiology Department (initial TVS examination in the ultrasound unit, and MRI examination in the MRI unit) in the duration from July 2018 to December 2019.
Written informed consents were taken from all participants.
All cases were examined by:
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(1)
Transvaginal ultrasound (TVS): The TVS examination was conducted on the commercially available Toshiba Xario using the transvaginal probe (661PVT-6 MHz).
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(2)
Magnetic resonance imaging (MRI): The MRI study was conducted on the commercially available 1.5 Tesla (Philips Ingenia) using Phased array coils.
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(3)
Histopathological examination of the abnormally thickened endometrium as a gold standard for correlation with MRI data.
MRI protocol
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(A)
Non-contrast conventional MRI sequences
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Axial T1WI (TR/TE, 400–600/10–14 ms); FOV, 32 cm; matrix 263 × 171; slice thickness, 6 mm; inter-slice gap, 1.3 mm
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High-resolution sagittal and axial T2WI (TR/TE, 3000–6000/100–110 ms)
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T2WI with chemical shift-selective fat saturation pulse using the following parameters: (TR/TE, 4000–6000/100–120 ms); slice thickness, 5 mm; gap, 1 mm; field of view (FOV), 32 to 42 cm; matrix, 256 × 256
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(B)
Diffusion-weighted imaging (DWI)
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DW-MRI in the axial, and sagittal planes using a single-shot echo-planar imaging sequence (TR/TE effective range, 8000–10,000/70–100; slice thickness/intersection gap, 5/1 mm; FOV, 32 to 42 cm; matrix, 128 × 128
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b value 0, 500, and 1000 s/mm2
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Generation of ADC maps for visual and quantitative analysis.
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(III)
Diffusion tensor imaging (DTI)
- Diffusion tensor, which consisted of a single-shot, medium or high (sensitivity encoding) SENSE, spin-echo echo-planar sequence in 16 encoding directions and a diffusion-weighting factor (b value) of 0 and 800 s/mm2 in sagittal, axial or combined views using SS-EPI (slice thickness, 3 mm; inter-slice gap, 1 mm; repetition time (TR), 10,000 ms; echo time (TE),60 ms; matrix, 100 × 132; voxel size, 1.67 × 1.67 × 3.00 mm; acquisition time, 6.12 min; number of excitations (NEX), 2; number of slices, 40.
- The field of view (FOV) was 320 × 320 mm2, and the thickness and inter-slice gap values were the same for DTI and T2W images to enable anatomical compatibility for analysis.
Post-processing (data analysis)
The Digital Imaging and Communications in Medicine (DICOM) images were transferred to workstation (extended MR Workspace 2.6.3.5, Philips medical systems Nederland B.V) supplied by the vendor.
DW-ADC maps were generated from MRI-DW images.
DWI and DTI included qualitative and quantitative analysis:
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(1)
The qualitative analysis
Regarding the signal intensity, endometrial SI was evaluated on high b value images, and corresponding DW-ADC maps.
Two dimensional (2D) analysis: DT-ADC (MD), DT-FA gray-scale, and color-coded maps were automatically generated by the software. Visual assessment of the signal of the endometrium in those maps was done.
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(2)
The quantitative analysis
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(a)
DW-ADC maps
Single or multiple circular regions of interest (ROI) were drawn manually on the targeted regions.
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(b)
DTI maps
DT-FA and DT-ADC (MD) parameters were calculated by drawing elliptical, manually positioning region of interest (ROI). Five (5) ROIs were placed on the normal or diseased endometrium in the sagittal plane image and 3 ROIs in the axial plane image.
DT-FA was calculated as follows (Nott et al., 2017):
$$ FA\sqrt{\frac{3}{2}\cdot \frac{\left({\lambda}_1-{\left(\lambda \right)}^2\right)+{\left({\lambda}_2-\left(\lambda \right)\right)}^2+{\left({\lambda}_3-\left(\lambda \right)\right)}^2}{{\lambda_1}^2+{\lambda_2}^2+{\lambda_3}^2}} $$
DT-ADC (MD) was calculated as follows (Nott et al., 2017):
$$ \mathrm{MD}=\left(\uplambda 1+\uplambda 2+\uplambda 3\right)/3 $$
Mean values of DT-FA and DT-ADC (MD) of both sagittal and axial images were then calculated.
Statistical analysis
Data were fed to the computer and analyzed using IBM SPSS software package version 22.0. The normality of data was first tested with one-sample Kolmogorov-Smirnov test.
Descriptive (quantitative) data were calculated in the form of mean and standard deviation (±SD).
Qualitative data were described using number and percent.
Validity was tested by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy.
The used tests were one-way ANOVA test: for normally quantitative variables, to compare between more than two groups (normal and benign, normal and malignant, and benign and malignant).
For all previously mentioned statistical tests done, the threshold of significance is fixed at 5% level (P value). The smaller the P value obtained, the more significant are the results.