Dynamic Multi-position MRI of Pelvic Floor Anatomy in Normal Volunteers. A. J.
Yun, B. L. Daniel, B. Chen, and T. Efird. Dept. of Radiology, Stanford University, ...
Dynamic Multi-position
MRI of Pelvic Floor Anatomy in Normal Volunteers
A. J. Yun, B. L. Daniel, B. Chen, and T. Efird Dept. of Radiology, Stanford University, Stanford CA 94305 Introduction: Incontinence and pelvic prolapse, two of the most common urogynecologic conditions affecting women, are attributed to various functional and anatomic abnormalities of the bladder, urethra, and pelvic organs. Currently available methods of evaluation for these conditions include physical exam, bead-chain cystography, vaginography, ultrasound, and video urodynamics. Compared to these methods, MRI can offer superior, multicompartment soft-tissue detail without radiation exposure or invasive patient preparation. Yang, et al, reported dynamic MRI evaluation of pelvic floor descent in patients who were imaged at rest and while straining in the supine position. Fielding, et al, observedchangesthat occurred in the resting pelvic floor anatomy of normal volunteers when imaged in supine and sitting positions within an open MRI environment. In our work, we performed dynamic evaluation of pelvic floor anatomy in asymptomatic female volunteers in supine, lithotomy, and sitting positions with simultaneous manometry in an open-configuration MRI. Methods: Ten normal female volunteers participated in the study. The subject age ranged from 25 to 48. All denied symptoms of incontinence or prolapse and prior pelvic surgery. The subjects were imaged in an open .5 T open MR scanner (Signa-SP, GE Medical Systems, Milwaukee, WI) with real-time pelvic manometry. The pelvic manometer was constructed using a saline-filled sterile condom wrapped around a 12F Robinson catheter (Sherwood Medical, St. Louis, MO) which was attachedto a central venous pressure monitor. The subjects voided within a half-hour prior to starting the study and self-inserted the manometer intravagianally prior to entering the MR scanner. The volunteers were imaged in the supine, lithotomy, and sitting positions. A body flex coil was wrapped around the pelvis when imaging in the supine and lithotomy positions. A loop coil was placed under the patient when imaging in the sitting position. In each of the three positions, the patients were imaged at rest and while straining. The degree of straining was standardizedto 30ml rise in water manometric pressure from baseline. For each set of imaging, sagittal localizer was followed by a midline sagittal T2-weighted Fast Spin Echo scan (TR 3000; TE 104; 36x36 FOV; 256x128 matrix; 1 NEX; 9mm skip lmm; 30 seconds) demonstrating the bladder, urethra, symphysis, vagina, cervix, and rectum. Using the sagittal images, the following parameters were measured: distance between the symphysis and anterior urethra, distance between symphysis and posterior urethra, posterior urethral angle, and the distancesfrom the bladder neck and cervix to the pubococcygeal line.
Figure 1: SagittalT2-weightedFSE imagesin the pelvis. (A) supine at rest; (B) supine while straining; (C) lithotomy at rest; (D) lithotomy while straining; (E) sitting at rest; (F) sitting while straining.
Symphysis to a. ureth (mm) Symphysis to p. ureth (mm) Posterior urethral angle
bladneckto pubococ (mm)
supine supine litho rest strain rest 11.6 12.6 14.1
litho strain 16.3
sitting sitting rest strain 15.5 16.4
I!Z2.5
2! 3.3
f 5.9
f 8.9
z!z3.7
+ 5.6
22.4
23.9 I!I 4.4
23.7 f 9.5
27.7 + 12.6
25.8 zk 5.7
29.1 + 9.2
I!Z3.2
150.2
161.2
147.8
178.0
163.7
182.1
k 23.3
f 19.9
f 22.6
km30.8
f 20.4
I!C30.0
124.7 k 6.5
Cervix to 34.5 pubococ(mm) f 7.8
1 14.7
123.5
110.8
I!I 11.7
k4.5
f 15.3
21.1
26.0
15.6
118.5 f4.4 25.4
16.0 k 13.6 9.1
Z!I15.2 + 13.5 t 21.2 * 12.8 & 22.3
Figure 2: Pelvic floor measurementsin asymptomaticwomen. Results: Image quality was adequateto demonstrate the pelvic floor anatomy in all cases [Figure la - If]. Pelvic floor anatomic measurementsare shown in Figure 2. Conclusions: Images of the pelvic floor may be obtained in supine, lithotomy, and sitting positions during rest and straining in an open MR environment. Significant variations in pelvic floor anatomy were observed among asymptomatic volunteers. It is hoped that collection of dynamic, multi-positional pelvimetric measurementsin asymptomatic volunteers will establish a baseline for evaluation of patients with stress incontinence and pelvic prolapse.
Acknowledgments: The department of Radiology and the department of OB/GYN. References: 1. Fielding, J., et al, JMRZ, 6, 961, 1996. 2. McCarthy, S., Radio1 Clinics of North America, 30, 769, 1992. 3. Mostwin, J., et al, Urol Clinics of North America, 22, 539, 1995. 4. Yang, A., et al, Radiology, 179, 25, 1991.
