MR IMAGING PROTOCOL Fig. 6
To review pelvis and value pelvic and inguinal lymph nodes:
- Axial T1-weighted fast spin-echo .
- Coronal,
sagital and axial T2-weihgted fast spin-echo.
To assess vaginal tumor and its invasion of adjacent tissues:
- Oblique axial (perpendicular to long axis of vagina) T2-weighted high resolution images.
Optional:
- Diffusion-weighted (b=400 and 800 sec/mm2).
- Axial fat-saturated T2-weighted FIESTA (fast imaging with steady-state precession).
The use of gel to distend the vagina can upgrade the diagnose.
The use of intravenous contrast may not be advantageous because adjacent tissues can intensely enhance.
MR IMAGING NORMAL VAGINA Fig. 7
The vaginal wall is constituted by three layers (inner to outer): the mucosa,
the muscular and the adventitia.
These layers have different intensities:
- Mucosa layer: High signal intensity on T2 weighted imaging.
- Muscular layer: Low signal intensity on T2- weighted imaging.
- Adventitial layer: High signal intensity on T2-weighted imaging.
All of them uniform intermediate signal intensity on T1-weighted imaging.
The signal of the vaginal wall and thickness of the mucosal layer fluctuate depending on the menstrual cycle.
The mucosal layer is thicker and of higher T2-weighted signal intensity in the late proliferative and early to middle secretoy phases of the menstrual cycle.
In postmenopausal women mucosa layer is slim with widespread decrease singnal intensity of the all thickness of the vaginal wall.
Althoug with the use of hormone replacement therapy may be maintanined MR imaging appearance of the vagina in postmenopausal women.
MR IMAGING PRIMARY VAGINAL MALIGNANCIES
The most important role of magnetic resonance imaging in vaginal cancer is staging,
since the histological diagnosis is usually made prior to MR imaging.
Although the FIGO staging of vaginal cancer is based on physical examination however MR imaging allows us to know the exact extension of the tumor as well as the involvement of the lymph nodes. In addition,
most vaginal tumors have a non-specific behavior in MR imaging,
distinguishing only melanoma that has a different behavior in magnetic resonance.
So there is very little literature on the characteristics in the MRI of different types of vaginal tumors,
the largest radiological series incudes 34 patients (1)
Squamous cell primary vaginal carcinoma Fig. 8 Fig. 9 Fig. 10 ,
as well as primay vaginal adenocarcinoma,
present in the T2-weighted sequences an intermediate-high homogenous signal intensity greater than the pelvic muscles.
This allows us to assess the local invasion in view of muscularis layers of the vagina are hypointense.
In T1 sequences the tumor is isointense to the vaginal wall,
visualizing an alteration of the normal morphology of the vagina only when it is a large lesion.
After the administration of contrast ,
primary vaginal tumors show more vivid signal enhancement than the rest of the vaingal wall.
The primary melanoma of the vagina presents a low signal in T2-weighted sequences and a high signal in T1-weighted sequences.
This is due to the paramagnetic effect of melanin and methemoglobin in MRI.
Varying according to the amount of melanin and methemoglobin the characteristics of MRI.
Another type of primary vaginal tumors that may have a special appearances is leiomyosarcoma,
which is similar to primay uterus leiomyosarcoma.
Primay vaginal leiomyosarcoma Fig. 11 could appear with intermediate signal intensity with pockets of high signal intensity on T2-weighted sequences and with low/intermediate signal intensity on T1-weighted sequences.
STAGING PRIMARY VAGINAL MALIGNANCIES
Vaginal cancer staging is still based physical exam.
MRI is not used in the initial staging,
although the FIGO Gyneocologic Oncology Committee recommends using it for a better definition of the tumor and its extension.
FIGO's classification is the most used for the staging of vaginal tumors,
but there are other classifications.
Fig. 12 Fig. 13 Fig. 14
MRI IMAGING SECONDARY VAGINAL MALIGNANCIES
Metastatic tumors are more frequent than the primary malignant tumors of the vagina.The most frequent is the direct tumor spread from contiguous organs for instances vulva ,
cervix uteri ,
bladder and rectum .
These tumors conserve the MRI appearance of the primary tumor.
The invasion of the vagina is included in their staging:
- T4 urinary bladder carcinoma
- T4a rectal carcinoma.
Fig. 17
- T2a cervix uteri (involvement limited to the upper two‐thirds of the vagina without parametrial involvement) or T3 (The carcinoma involves the lower third of the vagina) Fig. 15
- T3 carcinoma of vulva (involvement of lower third of vagina without extension to adjacent perineal structures) or T4 (tumor invades upper 2/3 of vagina) Fig. 18
The remote vaginal metastases are very uncommon from ovarian,
breast,
colon,
melanoma and uterus.