The Anatomic And MR Imaging Study Of The Urogenital Diaphragm And The Fascia Around The Rectum

Objective:Using magnetic resonance imaging(MRI) combine with sectional anatomic and the normal people MR scan to study the pelvic membrane. The focus of the study is urogenital diaphragm, Denonvilliers'fascia, mesorectum and mesorectal fascia,and to find and cofirm the structrue of these membrane and fascia, analyses the normal imaging feature and evaluate the local invasion of pelvic tumor MRI imaging feature.Materials and Methods:1.Seven speciments of cadaver pelvic,4 males and 3 females. Firstly use the MRI scan to the male cadaver, then coronal, sagittal and axial celloidin to observe the membrane sturcture.2.From January 2008 to February 2010,30 health volunteers'the pelvic scan were imaged with MRI examination, each gender have 15 people. The average age of male people is 29.4, the femal people is 24. All of the femal volunteers were without childbearing history. All the volunteer were admitted to have the MRI scan.3.From March 2008 to February 2010,six patients with pelvic membarne invaded by tumor were choosen to MRI scan and observe the imaging features.Using rate compare and rank sum test descripe the ability of exhibition to the membrane in different sequences.Results:1. Urogenital diaphragm:(1)Cadaver:normaly the urogenital diaphragm connect to ramus inferior ossis pubis and ischiadic ramus. There are three layer inside the urogenital diaphragm, they are superior fascia of urogenital diaphragm, inferior fascia of urogenital diaphragm and deep transverse muscle of perineum. (2) MRI imaging: coronal is the best location to exhibit the urogenital diaphragm; all of the structure appears like "sandwich", and the three layer is moderate signal in MRI. Fat-depresstion of T2WI can see more clear of this structure.2. Denonvilliers'fascia:(1)Cadaver:in thin section anatomy, Denonvilliers'fascia is at the posterior part of bladder, prostate and seminal vesicle (vagina for women), it mix together to the rectovesical pouch at the above part. (2) MRI imaging:in T1WI or T2WI imaging the Denonvilliers'fascia appears as a low-signal-intensity linear sturcture. The whole path of Denonvilliers' fascia can be seen at sagital image. It can be seen more clearly in man's MRI imaging than in woman's.3. Mesorectum and mesorectal fascia:(1)Cadaver:the mesorectal fascia is a continuous smooth structure surrounding the rectum and mrsorectum as a complete "sock", whose main component is collagen and formed by the pelvic visceral fascia. In the structures of mesorectum are fat, blood vessels, nerves, and lymphatics. In thin section anatomy, the rectum and its surrounding structures are well displayed, it could display the sturctures of the rectum. (2)MR imaging:MR can display most of the related structures surrounding the rectum. Mesorectal fascia, as a distinct thin layer, encompassed the mesorectum and is well seen on MR images. In T1WI or T2WI MR imaging, the mesorectum and is well seen on axial MR images. In T1WI or T2WI MR imgaing, the mesorectal fascia appears as a low-signal-intensity linear structure surrounding the mesorectum. The mesorectum is shown on axial and sagittal sections as a high-signal-intensity which was similar to the signal of fat surrounding the rectum, containing vessels and lymphatic tissue.MR images with tumor invasion:(1)Direct sign of invasion:two patiens of prostate tumor has the enlarge of prostate and irregular size. Low nodus signal can notice in the peripheral zone. The structure of Urogenital diaphragm can't see very clearly. Four patients for rectal cancer, the rectum invaded by tumor broken through the enteric cavity.(2) Indirect sign:fat gap disappeared and lymph node enlarged. The vessel concentrate to the mass.Conclusion:1. Urogenital diaphragm:this structure can be found on both man and woman. On MRI imaging, it looks like "sandwich", the three layers are superior fascia of urogenital diaphragm, inferior fascia of urogenital diaphragm and deep transverse muscle of perineum. Coronal scan is the best choice to show this sturcture.2. Denonvilliers'fascia:On MRI image this structure can be seen more clearly in man than in women. On T1WI or T2WI MR image the fascia appears as a low-signal-intensity. Sagital scan is the best plate for this structure.3. Mesorectum and mesorectal fascia:Mesorectal fascia, as a distinct thin layer, encompassed the mesorectum and was well seen on MR images. In T1WI or T2WI MR imgaing, the mesorectal fascia appears as a low-signal-intensity linear structure surrounding the mesorectum. The mesorectum was shown on axial and sagittal sections as a high-signal-intensity which was similar to the signal of fat surrounding the rectum, containing vessels and lymphatic tissue.4. Malignant tumor can invade the urogenital diaphragm, Denonvilliers'fascia and mesorectum and mesorectal fascia, the MRI imaging can provide valuable information for preoperative radiotherpy and serves as a promising method to determine different treatment policy for rectal and prostate cancer patients pre-operatively. This would be helpful for staging the rectal and prostate cancer based on the distance between the tumor and the fascia, the relation of the tumor with the circumferential resection margins, and on the prognostic factors.