Patients are typically instructed to fast for 4–6 hours prior to MRI in order to diminish artifacts due to peristalsis. In addition, an antiperistaltic agent, such as butylscopolamine bromide or glucagon, is administered intramuscularly or intravenously at the beginning of the examination. Patients are also instructed to empty their urinary bladder to decrease ghost artifacts related to bladder motion/filling. Use of vaginal gel is optional and maybe helpful in assessment of tumour extension into the vagina in patients with cervical cancer as it can assist in radiotherapy planing. Imaging is performed with the patient in the supine position using a multichannel phase array surface coil. Saturation bands placed along the subcutaneous fat of the anterior and posterior body wall are useful to diminish near-field artifact which is more pronounced at 3T. The standard MRI uterus protocol includes axial SE T1WI with a large FOV to evaluate the entire pelvis and upper abdomen for lymphadenopathy as well as bone marrow changes; and high-resolution FSE T2WI in the sagittal, axial and coronal planes. Other extra planes and imaging sequences are specific and designed to answer a specific clinical question. An extra T2WI sequence in the coronal oblique (parallel to the long axis of the uterus) plane is crucial for precise classification of uterine anomalies. Large FOV T2WI in the coronal plane should also be obtained to look for potential associated renal tract anomalies in these patients. T2WI in the axial oblique plane are crucial for accurate evaluation of depth of myometrial invasion (perpendicular to the long axis of the uterus) in endometrial cancer and parametrial invasion (perpendicular to the long axis of the cervix respectively) in patients with cervical cancer. Dynamic contrast-enhanced MR images are obtained with a three-dimensional gradient echo T1-W fat saturated sequence after the administration of 0.1 mmol/kg of gadolinium at a rate of 2 mL/sec. Images are traditionally acquired prior to contrast medium injection and then during multiple phases of enhancement in sagittal planes at 25 sec, 1 min, and 2 min after injection; a delayed sequence is acquired on axial oblique 4 min after injection. The maximum tumor to myometrium contrast is achieved in the equilibrium phase (2 minutes post injection) which is the most optimal phase of enhancement for assessment of the depth of myometrial invasion in endometrial cancer. One could even argue that since the distinction between tumors confined to the endometrium and those who invade the inner myometrium is no longer of clinical importance, as both categories are classified as stage IA in the revised FIGO staging system, the early phases of enhancement (arterial and portal phase) may no longer be needed for staging of endometrial cancer. DW-MRI is now part of routine MRI protocol for evaluation of uterine malignancies. It should be performed at two or more b-values, which include one or more low b-values (50-100 s/mm2) since perfusion contribution to diffusion is then eliminated and a very high b-value (750-1000 s/mm2). Both breath hold and non-breath hold DW sequences can be used. However, the type of DW sequence differs among manufacturers and the radiologist should be familiar with the strengths and limitations of their own scanners. Combination of DWI with conventional MRI sequences improves lesion detection and radiologist confidence in imaging interpretation. DW-MRI can be useful for accurately determining the depth of myometrial invasion in endometrial cancer. This can be particularly helpful in cases of tumors that are either iso- or hyper-intense relative to the myometrium or when the use of intravenous contrast medium is contra-indicated. In addition, ADC values are inversely related to the cellularity of tumours which may be useful for distinguishing between benign and malignant tissues and for monitoring tumour response to treatment in cervical cancer. There are several MRI pitfalls that should be recognized when imaging the female pelvis. MRI appearances of uterus and ovaries are dependent on the phase of menstrual cycle/use of exogenous hormone therapy. Normal postsurgical and post-radiation appearances of the pelvis can sometime mimic tumor recurrence. It is important to become familiar with these appearances in order to avoid potential pitfalls. One very common pitfall is differentiation of transient myometrial contraction from adenomyosis. Interrogation of all imaging planes over the duration of the entire MRI examination can be useful to distinguish between the two, although myometrial contractions can last up to 45 min. Both dynamic contrast-enhanced MRI and diffusion weighted MRI improve the accuracy of MRI in evaluation of the malignant pelvic conditions. However, certain pitfalls related to each technique should be recognized in order to avoid misinterpretation.

Acknowledgements

No acknowledgement found.