Diffusion-weighted MRI using an endovaginal coil for evaluating early cervical cancer

Magnetic resonance imaging is currently the gold standard for assessing the neck of the womb and surrounding tissues in cases of cervical or suspected cervical cancer. However, conventional techniques lack both resolution (pixel size 0.6 mm) and contrast when standard MRI pulse sequences are used. It is possible to increase the resolution of the images by placing a receiver probe close to the part under study to maximise signal and reduce noise from that region. We have previously developed an endovaginal receiver for use at 1.5T and shown significant improvement in resolution. However contrast between tumour and non-tumour tissue remains low and requires use of specialist sequences such as diffusion-weighted images which are inherently low on signal-to-noise ratio. Production of an endovaginal coil for use at a higher field strength (3.0T) would enable use of higher resolution diffusion-weighted imaging. We propose therefore to build an endovaginal device for use at 3.0T, optimize the diffusion-weighted imaging and compare the accuracy of conventional MRI techniques with and without the addition of diffusion-weighted imaging for detecting early stage cervical cancer by comparing with the tissue findings at surgery.

Endovaginal T2-W magnetic resonance imaging (MRI) techniques allow precise location of small cervical cancers, but accuracy of tumour detection is reduced post cone-biopsy because of cervical distortion, haematoma and granulation tissue. The signal-to-noise ratio improvement provided by an endovaginal coil enables acquisition of Diffusion-Weighted sequences (DW-MRI), which have the potential to differentiate small tumours from post-surgical change based on water diffusion within tissues. At 1.5T, our pilot data using an endovaginal coil indicates a trend to improve sensitivity for tumour detection when DW-MRI is used in conjunction with T2-W MRI. We wish to develop this technique for use at 3.0T which offers further gains in signal-to-noise ratio leading to better resolution and thus potentially improved accuracy for tumour detection. We propose to build an endovaginal coil for use at 3.0T (addressing issues such as increased susceptibility artefacts from coil components at higher field strength), integrate it with an external pelvic array coil, optimise the DW-MRI protocol and perform a blinded comparison of T2-W MRI with and without DW-MRI against a histological gold standard in patients with Stage Ia2 and Ib1 cervical cancer.