title: MR imaging for preoperative evaluation of primary rectal cancer: practical considerations.
abstract: High-resolution magnetic resonance (MR) imaging plays a pivotal role in the pretreatment assessment of primary rectal cancer. The success of this technique depends on obtaining good-quality high-resolution T2-weighted images of the primary tumor; the mesorectal fascia, peritoneal reflection, and other pelvic viscera; and superior rectal and pelvic sidewall lymph nodes. Although orthogonal axial high-resolution T2-weighted MR images are the cornerstone for the staging of primary rectal cancer, high-resolution sagittal and coronal images provide additional value, particularly in tumors that arise in a redundant tortuous rectum. Coronal high-resolution T2-weighted MR images also improve the assessment of nodal morphology, particularly for superior rectal and pelvic sidewall nodes, and of the relationship between advanced-stage tumors and adjacent pelvic structures. Rectal gel should be used in MR imaging examinations conducted for the staging of polypoid tumors, previously treated lesions, and small rectal tumors. However, it should not be used in examinations performed to stage large or low rectal tumors. Diffusion-weighted imaging is useful for identifying nodes and, occasionally, the primary tumor when the tumor is difficult to visualize with other sequences. Three-dimensional T2-weighted imaging provides multiplanar capability with a superior signal-to-noise ratio compared with two-dimensional T2-weighted imaging.
authors.affiliation: Department of Diagnostic Radiology, University of Texas M.D. Anderson Cancer Center, 1400 Pressler St, Unit 1473, Houston, TX 77030, USA. hkaur@mdanderson.org
authors.forename: Harmeet
authors.initials: H
authors.lastname: Kaur
authors.forename: Haesun
authors.initials: H
authors.lastname: Choi
authors.forename: Y Nancy
authors.initials: YN
authors.lastname: You
authors.forename: Gaiane M
authors.initials: GM
authors.lastname: Rauch
authors.forename: Corey T
authors.initials: CT
authors.lastname: Jensen
authors.forename: Ping
authors.initials: P
authors.lastname: Hou
authors.forename: George J
authors.initials: GJ
authors.lastname: Chang
authors.forename: John M
authors.initials: JM
authors.lastname: Skibber
authors.forename: Randy D
authors.initials: RD
authors.lastname: Ernst
mesh_terms: D001003:Anal Canal / Q000473:pathology; D016477:Artifacts; D001808:Blood Vessels / Q000473:pathology; D017024:Chemotherapy, Adjuvant; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D019468:Disease Management; D005782:Gels; D006801:Humans; D021621:Imaging, Three-Dimensional; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009130:Muscle, Smooth / Q000473:pathology; D009361:Neoplasm Invasiveness; D010537:Peritoneum / Q000473:pathology; D011300:Preoperative Care / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio
chemical_list: D003287:Contrast Media; D005782:Gels