b

c

Fig. 33  Lymph node staging in different patients. (a–c) PD-TSE images in transverse orientation. (a) Suspicious lymph node of round configuration measuring 1 cm in diameter of the external iliac artery group on the left (arrow) in a patient with cervical cancer with bilateral parametrial infiltration and ureteral distention (open arrows). (b) Suspicious round and enlarged lymph nodes along the external iliac artery on both sides and an increase in the number of presacral lymph nodes with round configuration (arrows). (c) Suspicious round and enlarged lymph nodes of the common iliac artery group on both sides (arrows). The presence of pelvic lymph node metastases is not taken into account in the FIGO staging system

Hematogenous dissemination to the skeleton occurs late. MRI with unenhanced and contrast-enhanced fat-saturated T1-weighted sequences depicts bone metastases as hyperintense lesions in the low-inten- sity bone marrow with high sensitivity. CT primarily shows the extent of osseous destruction.

2.4\ Specific Diagnostic Queries

2.4.1\ Preoperative Imaging

Pretherapeutic local tumor staging is crucial to determine resectability and to select the most suitable operative procedure (simple hysterectomy, radical hysterectomy, trachelectomy, extent of lymphadenectomy), which is primarily based on tumor size, lymph node status, and parametrial involvement. The surgical procedure chosen based on the MRI findings is often specified further by surgical lymph node staging. If no primary surgery and no surgical lymph node staging are performed, the MRI findings serve to determine the target volume to be irradiated. MRI after adjuvant therapy serves to reconsider the indication for surgery. In patients with local recurrence, the MRI findings have an important role in deciding to reoperate and the surgical technique. Contraindications to curative exenteration are intraperitoneal implantation, nonresectable nodes, extensive involvement of the pelvic sidewall and liver or lung metastases.

Furthermore, MRI plays a crucial role in establishing the indication for radical trachelectomy. Only patients in whom MRI demonstrates a tumor-free internal os of the cervical canal at the isthmus uteri are candidates for trachelectomy (Peppercorn et al. 1999). Therefore it is additionally important to estimate the distance of the tumor from the uterine isthmus and from the vaginal vault. Trachelectomy is not performed if there is infiltration of the isthmus or of the myometrium of the uterine corpus. The isthmus is identified by its small diameter and the entrance of the uterine vessels.

2.4.2\ Imaging Before Radiotherapy

In patients scheduled for primary radiotherapy without surgical staging, the pretreatment ­radiologic evaluation together with the clinical findings gains in importance. Although exter-

nal beam radiotherapy is still usually planned by means of a CT scan, MRI has an increasing role in treatment planning and controlling radiation (Figs. 39 and 40). The superior accuracy of T2-weighted images in the delineation of the primary tumor and the adjacent soft-tissue invasion make MR imaging more and more appreciated.

The CT scan performed to plan radiotherapy serves to determine the physical parameters of irradiation such as number and direction of the radiation fields, collimation, and dose distribution. The use of 3D-based individual planning of radiation fields has almost completely replaced the four-field box technique (Fig. 39).