Feasibility of MRI-Transvaginal Ultrasound Imaging for Deeply Infiltrating Endometriosis

Recent study reveals TVUS-MRI fusion imaging feasible for the detection of DIE

Key Points

Highlights:

• Although TVUS-MRI fusion imaging accurate for the detection of DIE; fusion imaging has many technical considerations that need to be addressed before being implemented in daily practice.

What’s done here?

• This study aims to evaluate the utility of MRI-Ultrasound fusion imaging using the anatomical landmarks for the purposes of diagnosing Deeply Infiltrating Endometriosis (DIE).
   

Key Results:

• 10 patients with clinical signs of DIE were included in this single-center study. The researchers used pelvic anatomical landmarks in order to fuse the images. 
• Measurement 1, the distance from the marked landmark organ and the fusion target were found to be an average of 13.6mm. Measurement 2 was not feasible because the visualization of the two points in one ultrasound image was not possible.
• After measuring the distance between anatomic landmarks, only 6/20 (30%) attempts to fuse the calibrated point were successful. In the remaining 70%, there was a deviation with a mean of 11.1mm.
• While this technique is feasible, further studies are required to reassess the accuracy of this technique to diagnosis DIE and to combine the positive effects of both MRI and TVUS imaging before being implemented for daily clinical practice.

Limitations:

• Variations in anatomy were important in the decreased accuracy of the fusion images in detecting DIE.
• Multiple calibrations for each patient were necessary, especially after patient movement.

Lay Summary

Endometriosis is a disease whereby endometrial tissue is present outside of endometrium. A specific form of endometriosis, Deeply Infiltrating Endometriosis (DIE), is characterized by endometriotic glands that invade through the endometrium and other structures in the pelvis and is associated with significant morbidity. Developing noninvasive and safe imaging techniques that accurately diagnose DIE will allow for a patient’s team of doctors to plan for appropriate treatments.

Fusion imaging is a new technology and includes the merging of cross-sectional imaging data obtained by MRI with ultrasound images while the images are being acquired.

This single institute study conducted by researchers from Leiden University Medical Center, Netherlands, aimed to evaluate the feasibility and accuracy of MRI-TVU fusion imaging for the purposes of diagnosing DIE. The researchers first use pelvic anatomical landmarks in order to fuse the images versus using visual inspection of each image. Patients were included in the study if their MRI scan was obtained 90 days or less prior to fusion imaging, symptoms that were diagnosed as DIE via MRI, and those without movement artifact in their imaging. Calibration of the images was performed by localizing two points on the uterus. Next, the distance between a marked organ on MRI and Ultrasound was determined by superimposing the two images (known as measurement 1). Measurement 2 was then obtained by taking the distance between the target organ to the nearest calibration point. Measuring the 2 point calibration between MRI and Ultrasound images were also performed.

The results of the measurements are as follows: Measurement 1, the distance from the landmark organ marked and the fusion target were found to be an average of 13.6mm. Measurement 2 was not feasible because visualization of the two points in one ultrasound imaging was not possible. Matching the 2-point calibration between MRI and Ultrasound was successful in only 30% (6/20) attempts, and in the remaining, there was a deviation of which the mean was 11.1mm. 

The explanation for this deviation in distance may be due to multiple factors including constantly moving pelvic structures such as the ovaries, movement via implementation of the TVUS probe affecting MRI images, and patient movement. Authors of this study conclude that fusion imaging for DIE is a feasible, reproducible new technique. However, further studies are required to reassess the accuracy of this technique to diagnosis DIE and combine the positive effects of both MRI and TVUS imaging. Before implementing this technique in daily practice, improvement in the software and more precise clinical conditions need to be met.

Research Source: https://www.ncbi.nlm.nih.gov/pubmed/30255164