Assessment of adnexal masses with Diffusion Weighted and dynamic contrast enhanced MR

INTRODUCTION

MRI used mainly in setting of sonographically heterogeneous adnexal mass, it can provide tissue characterization according to signal properties. ¹

Adnexal masses remain the first indication for gynecologic surgery. Our goal is to minimize number of women unnecessarily undergoing cancer surgery. ²

It may not be possible to decide preoperatively whether conservative or radical surgery is appropriate for adnexal masses. Pelvic MRI helps in difficult cases and may provide a more definitive diagnosis. MRI is  utilized for detection the origin of the lesion and determine its content with has a high accuracy. DWI helps in discrimination between types of masses, diagnosis of peritoneal implants. ³

When DWI revealed areas characterized by restricted diffusion or by low values of ADC generally correspond with foci of hypercellularity. Therefore, compatible with uncontrolled malignant proliferation.⁴

We studied the role of DW sequences and dynamic enhanced MRI, its diagnostic accuracy and also the ability DW images in accurate detection of lymphadenopathy.

PATIENTS AND METHODS

The current study is a prospective analysis that was conducted at Obeid hospital KSA (OBH) in the period from November 2019 to March 2020.

Patients:

The study included 20 patients with twenty adnexal masses that fulfilled the inclusion criteria:

• Complex solid/cystic patterns.
• Vegetations and/or septations in cystic masses.
• Heterogeneous cystic masses
• Large mass size (≥5 cm in max. length).

Exclusion criteria:

• T1WI hyper intense lesions.
• T2WI very low hypo intense lesions are considered fibrous.
• Contra indications to MRI study.

They referred from the Gynecology department to the Women’s imaging unit based on preliminary ultrasound examination used for cases selection.

The patients’ age (22 to 62 year old) (mean 39.77).

The main complain of the cases was abdominal pain (n=10), and/or long standing abdominal enlargement (n=5), other cases came with different complaints such as loss of weight.

Methods:

Patients referred to radiology department with preliminary US confirming the adnexal complex lesion.

MR imaging was performed on (Achieva, Philips medical system) 1.5-T. They imaged in supine position with the aid of pelvic phased-array coil. (SENSE XL Torso coil 16 channels).

Patient preparation:

Patients were instructed to fast for 6 hours and full bladder prior examination. MR Imaging protocol (Tab 1). Slice gap is one mm and flip angle 90 in all non-contrast sequences

Analysis of study:

• Pre-contrast images.
• Contrast enhancement.
• Wall thickness, presence of vegetations and/or mural enhancement.
• Presence of ascitis.
• Presence of pathologically enlarged pelvic or Para-aortic lymph nodes.
• Soft tissue infiltration.
• Omental deposit if present.

DWI qualitative analysis:

Our data analysis focused upon T2WI as base reference for mass detection. DWI high SI (diffusion restriction) in the solid components on different b values (0, 500, 1000, and 1500).

Matched ADC maps were applicable using also the available workstation: presence of bright SI on the ADC map stands for benign tissue, intermediate SI for malignant tissue and low to intermediate SI for fibrous /fatty tissue.

Quantitative analysis:

Manually plotted (ROI) was drawn at the part that showed hyperintensity, ROIs from 15 to 150 mm². ^{5, 6, 7, 8}

Statistical analysis:

The MRI suggested pathology had been correlated with surgical pathology specimen being the reference.

Using computer software package SPSS 15.0 in the analysis. For quantitative variables, mean and standard deviation were presented. Frequency and percentages were presented for qualitative variables, all statistical parameters were calculated for the MRI and DWI. T-test was done to estimate differences in quantitative variables. P Value < 0.05 is considered to be significant.

Table 1: The sequences of MRI study.

RESULTS

20 patients that revealed 20 adnexal  lesions selected after a preliminary pelvic ultrasound examination. The patients age range of 25 to 62 years (M= 39.77 +/-13.8 SD) showed benign lesions, while those their age ranged from 22 to 50 years (M=39.625 +/-10.676SD) showed malignant lesions.The histopathology of the evaluated masses were (10 benign, two borderline, and eight malignant) (Table 2).

The benign tumors were (two teratomas, two serous cystadenoma, two pedunculated subserous fibroid, one mucinous cystadenoma, one papillary serous cystadenofibroma,, one tubo-ovarian abscess, one pelvic abscess) (Figure 1).

Borderline tumor was: (borderline papillary serous cystadenoma). Malignant tumors included: (three- cystadenocarcinoma, three mucinous cystadenocar-cinoma, one juvenile granulosa cell tumor, one clear cell carcinoma) (Figure 2).

Table 2: The pathological types included in the study.

Fig 1: Benign tumors percentage.

Fig 2: Malignant tumors percentage.

Most of the masses elicited intermediate intensity in T1 (70%), some elicited subtle hyper intense signal (15%), and mixed signal (15%).(Figure 3).

Most of the masses elicited mixed intensity in T2(60%), while the rest elicited bright signal intensity (40%).(Figure 4).

The adnexal masses showed variable contrast uptake either early (30%) or delayed (25%) or no appreciable enhancement (45%) (Figure 5).

Regarding the malignant masses: two of them showed wall thickness > 3 mm (25%), four cases showed solid parts, vegetations > 1cm (50%), two masses were associated with moderate ascites (25%), and another two showed associate enhancing peritoneal nodules (25%) (Figure 6).

Some masses revealed hyperintensity in DWI and were diagnosed as being malignant in spite of benign pathology, these masses included the following entities: 1) mature cystic teratoma(n=2), 2) tubo-ovarian abscess(n=1) and 3 uterine fibroid (n=1). (Table 3).

Fig 3: Intensities of the masses in T1.

Fig 4: Intensities in T2.

Fig 5: Contrast uptake by the masses.

The different ADC values for malignancy, the minimum was 0.2 x 10-3 mm2/s and maximum was 1.1 x 10-3 mm2/s with Mean +/- SD 0.74(+/-38722), while for benign masses, minimum was 0.2 x 10-3 mm2/s and maximum was 2.7 x 10-3 mm2/s with Mean +/- SD 1.45 (+/-5463).(Table 4).

We compared the cases which was diagnosed by MRI as benign or malignant tumors as criteria mentioned before, with those diagnosed depending on the DWI and DCE-MRI, and the pathology which is considered the golden ruler.

For the sake of statistical evaluation, the borderline pathology of low potential malignancy (papillary serous cystadenoma) was categorized with the benign tumors.

Conventional MRI suggested malignant pathology in 12 tumors as being malignant. Seven were true positive (TP), two were border line, while three were benign and diagnosed as being malignant (FP). Conventional MRI suggested benign pathology in eight cases; seven were true negative (TN) while 1 malignant and diagnosed benign (FN). Diffusion-weighted (DWI) magnetic resonance suggested malignancy in 14 tumors compared to only 8 stated by the pathology (TP=8), (FP=6).

DCE-MRI was able to diagnose 7 malignant tumors (TP), one showed enhancement delay and was diagnosed as benign (FN). (Table 5), ( Figure 7).

Fig 6: Criteria of malignancy in DCE MRI.

Table 3: showing signal intensities of the pathological entities presented in the current study regarding DWI at different b-values and corresponding ADC map.

Table 4: showing the different ADC values of the included masses.

Table 5: Result of conventional MRI, DWI & DCE.