Comparison of hybrid FDG PET/MRI compared with PET/CT in colorectal cancer staging and restaging: a pilot study

Raj Mohan Paspulati, Sasan Partovi, Karin A. Herrmann, Smitha Krishnamurthi, Conor P. Delaney, Nghi C. Nguyen

Research output: Contribution to journalArticlepeer-review

65 Scopus citations


Purpose: We report our initial clinical experience from a pilot study to compare the diagnostic accuracy of hybrid PET/MRI with PET/CT in colorectal cancer and discuss potential PET/MRI workflow solutions for colorectal cancer. Methods: Patients underwent both FDG PET/CT and PET/MRI (Ingenuity TF PET/MRI, Philips Healthcare) for rectal cancer staging or colorectal cancer restaging. The PET acquisition of PET/MRI was similar to that of PET/CT whereas the MRI protocol was selected individually based on the patient’s medical history. One nuclear medicine physician reviewed the PET/CT studies and one radiologist reviewed the PET/MRI studies independently. The diagnostic accuracy of each modality was determined in consensus, using available medical records as a reference. Results: Of the 12 patients enrolled, two were for initial staging and ten for restaging. The median scan delay between the two modalities was 60 min. The initial imaging was PET/CT in nine patients and PET/MRI in three patients. When PET/CT was performed first, the SUV values of the 16 FDG avid lesions were greater at PET/MRI than at PET/CT. In contrast, when PET/MRI was performed first, the SUV values of the seven FDG avid lesions were greater at PET/CT than at PET/MRI. PET/MRI provided more detailed T staging than PET/CT. On a per-patient basis, with both patient groups combined for the evaluation of N and M staging/restaging, the true positive rate was 5/7 (71%) for PET/CT and 6/7 (86%) for PET/MRI, and true negative rate was 5/5 (100%) for both modalities. On a per-lesion basis, PET/CT identified 26 of 29 (90%) tumor lesions that were correctly detected by PET/MRI. Our proposed workflow allows for comprehensive cancer staging including integrated local and whole-body assessment. Conclusions: Our initial experience shows a high diagnostic accuracy of PET/MRI in T staging of rectal cancer compared with PET/CT. In addition, PET/MRI shows at least comparable accuracy in N and M staging as well as restaging to PET/CT. However, the small sample size limits the generalizability of the results. It is expected that PET/MRI would yield higher diagnostic accuracy than PET/CT considering the high soft tissue contrast provided by MRI compared with CT, but larger studies are necessary to fully assess the benefit of PET/MRI in colorectal cancer.

Original languageEnglish (US)
Pages (from-to)1415-1425
Number of pages11
JournalAbdominal Imaging
Issue number6
StatePublished - Aug 12 2015
Externally publishedYes


  • Liver metastases
  • PET/CT
  • PET/MR
  • Rectal carcinoma

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging
  • Gastroenterology
  • Urology


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