In order to summarize this exhibit we have only focused in radiologist role and we won´t focus so much in MRI sequences or in the role of the others specialities.

Patients with clinically suspected rectal carcinoma underwent sagital T2 Fat supressed sequences to locate tumor. After this we make axial T1 FSE and T2 FSE Fat Supressed sequences perpendicular to the tumor as well as the sames sequences in Coronal plane (parallel to anal canal). After this, sequences T1 FS weighted axial and coronal with Gadolinium.

We don ´t use contrast medium or enema inside rectum

There are differences betweens anatomist and surgeons in definition of what is rectum. We define rectum as the part of the digestive tube placed under an imaginary line between sacrum and pubis (Fig 1).

The approximate distance of rectum from the point of view of endoscopy is 12-15 cm. The limit considered in this project is 15 cm.

We define mesorectum as the fat tissue around rectum, in wich are inside vessels and  lymph tissue, as well as mesorectal layer (Fig 2).  The mesorectal layer is considered also as the Circumferential Resection Margin(CRM)  in surgery. If this margin is free in pathologic analysis will mean a better prognosis.

In the radiological report the radiologist has to describe and asses:

1. Maximum Extramural Depth (MED). We consider MED as the maximum distance between the muscular propia layer of rectum and the most lateral edge of the tumor (Fig 3).

Depending of this distance we talk about T3a(less than 1 mm), T3b(between 1.01 and 5 mm); T3c (between 5.01 and 15 mm) and T3d (more than 15 mm).

2. Distance from the tumor to Mesorectal Layer. The presence of tumor close to mesorectal layer (1 mm or less) is directly related with higher rate of local recurrence and a bad prognosis (Fig 4).

Patients with CRM positive have about 22% rate of local recurrence.

(Fig 5)

Colonoscopy can define the lenght of the tumor but it ´s not accurate to define the possibility of extramural extension or infiltration of mesorectal Layer (Fig 6)

3. Distance from the tumor to external sphincter. Depending if there is infiltration of external sphincter or not the surgical technic may change. The external esphincter is composed of striated muscle and continuous superiorly with the puborectalis and levator ani muscles.

(Fig 7, 8 and 9).

4. Perivascular infiltration. It happens when the growth of the tumor involves the blood vessels that are inside the mesorectum  fat surrounding rectum(Fig 10)

5. Perirectal Fraying. It ´s considered like all the linear imaging that sometimes are seen besides the tumor. Actually is considered like a "desmoplasic" reaction in response of the growth of the tumor but   it can ´t be defined like tumoral extension(Fig 11)

6. Lenght of the tumor (Fig 12) and infiltration to adyacent organs.

7.  Patological Lymph Nodes (Figs 13 and 14). In Vikingo project is considered the pathologist have to asses at least 12 lymph nodes in his/her analysis.

For TMN clasiffication, in MRI the radiologist have to asses:

a) Number (less than 4=N1,4 or more =N2)

b) Morphology and margins (normal, spiculated, lobulated, diffuse).

c) Enchacement.

d) Size.

A combination of all this features gives more sensibility and specifity to talk about metastasic lymph nodes. For example, in MRI lymph nodes with ill defined margins (spiculated, lobulated or diffuse) have a sensibility of 75% and specificity of 98% for malignancy.