The purpose of this study is to measure the diagnostic performance of whole body (WB) MR-PET for staging rectal cancer, compared with current standard of care (chest/abdominopelvic CT and rectal MRI) to investigate clinical feasibility of WB MR-PET as a one-stop preoperative imaging modality in patients with rectal cancer.

Inclusion Criteria:

1. Adult patients newly diagnosed with rectal cancer on colonoscopy or sigmoidoscopy, who are potentially eligible for neoadjuvant chemoradiotherapy.
2. Patients who sign informed consent.

Exclusion Criteria:

1. Patients who are contraindication for CECT
2. Patients who are contraindication for MRI/CE-MRI
3. patients who are diagnosed with Tis or T1 cancer after polypectomy or EMR
4. Patients who were already diagnosed with an active other cancers.
5. Premenopausal female patients who are pregnant.
6. Patients with fasting serum glucose level (>200mg/dL) on blood glucose meter prior to WB MR-PET.
7. Patients who are physically compromised to undergo WB MR-PET.

Adult patients newly diagnosed with rectal cancer.