MR technique delivers superior pelvic visualization
 |
“This technique is potentially more sensitive than CT or static MRI because of the ability to visualize actual reflux in non-dilated veins and more specific because the direction of flow can be determined easily regardless of ovarian vein dilation,” the authors noted.
According to researchers from the department of radiology at Duke University Medical Center in Durham, N.C., it is estimated that approximately 10 percent of women have incompetent ovarian vein valves and that of these, approximately 40 percent experience chronic pelvic pain directly as a result of venous congestion.
Noninvasive imaging—ultrasound, CT and MR—has been helpful in the workup of potential pelvic congestion syndrome cases, although none of these modalities has delivered the diagnostic certainty of conventional angiography. However, conventional angiography is a time-consuming, invasive procedure that requires contrast injections—which alters the normal physiologic hemodynamics of the ovarian veins.
“Static CT and MRI rely on the detection of ovarian vein dilation and early filling of the ovarian veins, although neither can accurately determine whether flow is anterograde or retrograde,” the authors noted.
First line therapy is currently ovarian vein ligation or embolization to prevent ovarian vein reflux. Because the generally accepted cause of pelvic congestion syndrome is retrograde venous flow in an incompetent ovarian vein, the direction of flow is of importance to clinicians.
The Duke University team has successfully deployed TR-MRA as a quick and non-invasive technique that allows visualization of physiologic blood flow dynamics. In addition, it has been shown to be highly sensitive for detecting pathology in a variety of blood vessels and body parts when compared with conventional angiography.
The retrospective analysis consisted of 100 consecutive patients who underwent TR-MRA of the pelvis to evaluate suspected or known pelvic pathology. None of the patients carried a diagnosis of pelvic congestion syndrome.
All TR-MRA exams were conducted on a 1.5T system (Magnetom Avanto, Siemens Healthcare). Two time-resolved techniques were used: 75 patients were imaged with the Time-Resolved Angiography With Interleaved Stochastic Technique (TWIST, Siemens); the remaining 25 patients were imaged with the Time-Resolved Imaging of Contrast Kinetics (TRICKS, GE Healthcare) technique. Patients were injected (0.1 mmol/kg body weight) with either gadopentetate dimeglumine (Magnevist, Bayer HealthCare) or gadobenate dimeglumine (MultiHance, Bracco Diagnostics) as a contrast agent, followed with a saline bolus.
The researchers reported that maximum intensity projections (MIPs) of each 3D data set were generated in both the coronal and sagittal planes and each case was independently reviewed by two experienced vascular MR radiologists.
Of 100 women who underwent MRI of the pelvis with the TR-MRA sequence, 10 percent were diagnosed with retrograde flow within the left ovarian vein.
“Review of the medical charts revealed that 40 patients had symptoms of pelvic pain, although 36 had co-existing pathology that can cause pelvic pain,” the authors wrote. “Five of 10 patients with ovarian vein reflux had symptoms of chronic pelvic pain that could potentially be attributable to pelvic congestion syndrome.”
The researchers observed that although there are numerous studies that have directly or indirectly correlated ovarian vein reflux with pelvic congestion syndrome, the actual significance of ovarian vein reflux is still debatable, considering that their study—and others—have shown ovarian vein reflux in asymptomatic women.
The scientists noted that a limitation of the study was that correlation with conventional angiography was not used to assess the sensitivity and specificity of TR-MRA. However, the research team is highly confident in the diagnostic capabilities of the technique.
“Not only can MRI provide detailed anatomic information, including other possible causes of pelvic pain, but also the TR-MRA sequence can provide dynamic imaging of the pelvic vasculature, thereby replacing conventional angiography and eliminating its invasiveness and ionizing radiation,” they wrote. “For these reasons, the TR-MRA sequence has replaced the static MRA sequence for all routine pelvic MRI studies in women at our institution.”