Application of 3.0 T multimodal MRI in FIGO staging of cervical cancer

2.1 General information

The data of 30 cases of cervical cancer confirmed by surgery and pathology or biopsy in our hospital from January 2018 to August 2022 were collected. The age of the enrolled patients ranged from 35 to 83 years, with an average of (57.10 ± 12.06) years.

2.2 Inclusion and exclusion criteria

According to the criteria defined in the multicentre clinical trial protocol [7, 8], cases of sporadic cervical cancer with complete clinical presentation and data were screened for inclusion in the study group. Inclusion criteria: (1) MRI was performed within three to five days after menstruation in non-menopausal patients. (2) Cervical cancer was diagnosed by biopsy or surgery within seven days after MRI examination. (3) No cervical cancer-related treatment, such as chemoradiotherapy and immunotherapy, was performed before the MRI examination. (4) An informed consent form was signed before the examination. Exclusion criteria: (1) Contraindication to MRI or claustrophobia and failure to complete the whole sequence. (2) Poor MRI image quality due to other reasons. (3) A history of gynaecological surgery, radiotherapy, chemotherapy or immunotherapy.

2.3 Examination method

Magnetic resonance imaging examination: Before the examination, the patient was instructed to drink water to fill their bladder appropriately. An indwelling needle was placed in the vein on the back of the hand. The patient assumed a supine position and placed their hands on their forehead. before lying on the MRI bed, to prevent anxiety, it was explained to the patient that the machine would make a particular noise during the examination.

Using a Siemens Spectra 3.0 T Superconducting Magnetic Resonance Imaging system, an eight-channel phased-array surface coil was selected.

Routine MRI scan: T1WI horizontal axis (TSE sequence: TR: 552 ms, TE: 13 ms, THK: 4.5 mm), T2WI horizontal axis (TSE sequence: TR: 3,000 ms, TE: 42 ms, THK: 4.5 mm), T2WI-fs horizontal axis (TSE sequence: TR: 2,400 ms, TE: 42 ms, THK: 4.5 mm), T2WI coronal (TSE sequence: TR: 3,820 ms, TE: 53 ms, THK: 4.5 mm), T1WI coronal (VIBE–Dixon sequence: TR: 4.0 Ms, TE: 2.5 MS, THK: 3.0 mm), T2WI sagittal (TSE sequence: TR: 3,280 ms, TE: 73 ms, THK: 4.5 mm) and T2WI-fs sagittal (TSE sequence, TR: 5,180 ms, TE: 68 ms, THK: 4.5 mm). Between 25 and 40 layers of each sequence were collected.

Diffusion-weighted imaging transverse axis, the value of diffusion-sensitive gradient b = 50 and b = 800 s/mm² (TR: 4,100 ms, TE: 69 ms, THK: 4.5 mm).

Multi-direction enhancement: After the intravenous injection of contrast agent Gd-DOPA (0.2 ml/kg), the transverse, coronal and sagittal T1WI sequences (VIBE-Dixon sequence: TR: 4.0 Ms, TE: 2.6 ms, THK: 3.0 mm) were scanned in sequence, and 40 layers were collected from each sequence.

2.4 Image analysis

A retrospective analysis of pathologically confirmed cervical cancer with conventional MRI plain scan images and assessment of FIGO staging was performed by two experienced deputy chief physicians (with 14 to 15 years’ experience, respectively) in the hospital’s imaging department [9], with the results used as a control group. Three months later, the two radiologists re-evaluated the FIGO staging using conventional MRI, DWI and multi-direction contrast-enhanced images, with the results used as observation data. In the event of a disagreement between the two observers, the determination of the FIGO stage of the images was discussed jointly.

2.5 Statistical methods

Measurement data were represented by ( X ¯ ± S ). Differences in FIGO staging accuracy between multiple imaging modalities and conventional MRI images for cervical cancer were examined using the one-sided Fisher’s exact probability method [10]. In addition, the Kappa test [11] was used for interobserver agreement (poor agreement: Kappa value 0.40, good agreement: Kappa value = 0.75–0.40, good agreement: Kappa value $>$ 0.75). Using SPSS version 26.0 statistical software, a value of 0.05 was considered statistically significant.

3.1 3.0 T MRI multimodal FIGO staging accuracy of cervical cancer

The final clinical stages of FIGO staging were as follows: Stage I ( n = 13), Stage II ( n = 7), Stage III ( n = 7) and Stage IV ( n = 3). There were 27 cases of squamous cell carcinoma and three cases of adenocarcinoma. In addition, clinical manifestations of abnormal vaginal bleeding (irregular, contact or postmenopausal) were found in 27 patients, and physical manifestations were found in three cases.

Overall, the accuracy of the multiple imaging modalities was higher than that of conventional MRI ( p = 0.013), and the accuracy of Stages I, II and III was also higher. However, there was no statistical difference ( P I = 0.161, P I ⁢ I = 0.324, P I ⁢ I ⁢ I = 0.324), and there was no difference in Stage-IV FIGO image staging between the two methods. The data are shown in Table 1.

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The two physicians did not find pelvic lymph nodes on conventional MRI, and the FIGO staging was Stage II. However, three months later, when the two physicians re-evaluated FIGO using multiple imaging modalities, the DWI layer and apparent diffusion coefficient (ADC) maps clearly showed enlarged lymph nodes; FIGO imaging staging was assessed at Stage IIIC1, and the final clinical FIGO staging confirmed correct FIGO staging with multiple imaging modalities (Fig. 1A–D).

The presence of T1WI-enhanced and intact mucosal line enhancement of the cervical external orifice (Fig. 2A) and the T2WI ‘T-shaped’ sign were reliable indications that the lesion was confined to the cervix, with no vaginal invasion (Fig. 2B).

Enhanced sagittal T1WI (Fig. 3A), axial T2WI (Fig. 3B) and coronal T2WI-fs (Fig. 3C) were combined to assess the extent of paracervical involvement more comprehensively.

4.1 DWI application and cause analysis

Diffusion-weighted MRI is an imaging method that uses MRI to observe the microscopic diffusion motion of water molecules in living tissues [5]. The speed of water diffusion can be expressed by ADC and DWI [14]. Maps of ADC are direct indicators of tissue diffusion and show the slow diffusion of water molecules in tissue, low ADC values, black images, and vice versa. Diffusion-weighted imaging reflects the strength of the diffusion signal; if the diffusion speed is slow, the signal loss is reduced when de-phased, the movement is high, and the image is white [14]. Both DWI and ADC are sensitive to displaying enlarged lymph nodes [14]. In this study, the primary and metastatic lymph nodes of cervical carcinoma were hyperintense on DWI and hypointense on ADC maps, i.e. ADC values were decreased, with good contrast to normal tissues (Fig. 1C and D). Therefore, it is of great importance in FIGO staging. The reason for this is that in cancer cells, growth and division are vigorous, the distribution of tumour cells is dense, nuclei are large, the cytoplasm is thin, and extracellular volume is reduced, limiting the movement of water molecules [15]. In addition, some studies have found that although the ADC values of lesions or lymph nodes in cervical cancer groups decreased, the degree of difference. The ADC values of cervical cancer cells with different pathological types or different degrees of differentiation are significantly different due to the other types of cancer cells volumes, the size and density of the outer space and the additional movement limits of water molecules [16]. Squamous cell carcinoma has a more compact extracellular space than adenocarcinoma, and water molecules are more severely restricted in this tight extracellular space; accordingly, the ADC value of squamous cell carcinoma of the cervix is lower than that of adenocarcinoma [17]. Therefore, the ADC value can further subdivide FIGO staging.

4.2 The application and analysis of multi-direction contrast-enhanced imagin

On MRI images, the edge of the lesion is clearly enhanced, which helps increase the contrast of the image against the surrounding normal tissue and improves the display of lesions [6]. The significant enhancement of the cervical and vaginal mucosa was helpful in determining the invasion of the corresponding structures and the staging (Figs 2 and 3). The tumour tissue is rich in blood vessels with different diameters, irregular distribution and rigidity, forming a vascular network of abnormal communications between arteries and veins. In addition, the cellular structural integrity of the vessel wall is poor, the basement membrane is deformed and incomplete – with only one layer of endothelial cells – and the permeability of the vessel wall is increased. After enhancement, the contrast agent enters the cancer focus and shows noticeable enhancement [18].

4.3 Key points of cervical cancer staging

Determining whether the vaginal fornix is invaded is a problematic point in FIGO staging, and the presence of a T-shaped sign on T2WI is a reliable indicator of non-invasion of the vagina. Interrupted vaginal mucosal line enhancement is the key to excluding Stage I and assessing Stages II to IV [19].

Diffusion-weighted imaging did not show the anatomic structure satisfactorily, T2WI and coronal T2WI showed the compression of fat well, and T2WI showed a low signal of the muscular layer, which had disappeared. In addition, the peripheral fat was blurred, and coronal T2WI examination revealed a mass protruding from the cervix (Fig. 3B).

Even if the lesion was localised to the cervix, Stage IIIC-1 was seen when pelvic lymph node metastasis was found, with Stage IIIC2 when para-aortic lymph node enlargement was observed (Fig. 1); the latter option involved extended-field full-dose radiotherapy [12], so lymph node enlargement should be evaluated. The staging criteria for inguinal lymph node metastasis are not specified but are included in this article for distant metastasis.

Klerkx [20] found that the sensitivity and specificity of conventional MRI in the evaluation of patients with cervical cancer were 33% and 83%, respectively. Anis Cerovac [21] found that MRI showed higher sensitivity, specificity and accuracy than transvaginal ultrasound in evaluating patients with endometrial cancer (97% vs. 77%; 85% vs. 88%; 90% vs. 83%, respectively). The above studies’ accuracy, sensitivity and specificity are significantly lower than those of this study, indicating that 3.0 T multimodal MRI FIGO has high accuracy in evaluating the staging of cervical cancer.

This study has the following limitations: 1. The sample size was small, only Stages I to IV were statistically analysed, and there was no further statistical research on sub-classifications. 2. No separate classification study was performed for cervical carcinoma with different pathological types and different degrees of differentiation. 3. Diffusion-weighted imaging was the only functional imaging method used from many imaging techniques, so further research on, for example, spectral imaging, dynamic enhancement and perfusion imaging, is required.