ARRS 2022 Abstracts

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E1778. Hybrid Imaging 18F-FDG PET/MRI in Rectal Cancer
Authors
  1. Pokhraj Suthar; Rush University Medical Center
  2. Jagadeesh Singh; Rush University Medical Center
  3. Rameshwar Prasad ; Rush University Medical Center
Background
18F-FDG PET/CT is a common examination performed to detect and stage cancer and evaluate treatment response. Rectal cancer is the third most common malignant neoplasm worldwide, with 55% of patients presenting in advanced stages at the time of initial diagnosis. Prognosis of rectal cancer is directly related to tumor infiltration into the mesorectum and ability to achieve negative circumferential resection margins. The main recurrence risk factors for rectal cancer are extent of the primary tumor, metastases to locoregional lymph nodes, extramural venous invasion, and distance from the primary tumor to the mesorectal fascia. This case-based PET/MRI pictorial review highlights the PET/MRI findings as well as staging and restaging of rectal cancer.

Educational Goals / Teaching Points
The goals of this exhibit are to learn the spectrum of characteristic PET/MRI findings and patterns of rectal cancer; review the utility of PET/MRI in diagnosis of TNM staging of rectal cancer; learn the prognostic value in restaging PET/MRI; and correlate 18F-FDG PET/MRI findings with other imaging modalities.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
18F-FDG PET/CT is a common examination performed to detect and stage cancer and evaluate treatment response. For functional evaluation of a tumor, 18F-FDG PET is useful due to a high metabolic turn rate of malignant cells, and it is useful in diagnosis of distant metastatic lesions. MRI of the pelvis is a gold standard imaging method for local staging of rectal cancer due to excellent soft tissue resolution. Tumor glycolysis and cellular density is diagnosed with FDG PET; tumor proliferation, apoptosis, and necrosis are diagnosed with DWI MRI; and tumor vascularity is diagnosed with contrast-enhanced MRI/CT. So, by using fusion FDG PET/MRI, tumor multifunctional evaluation is possible. This educational exhibit demonstrates an MRI acquisition protocol and various MRI sequences used for rectal cancer and fusion of FDG PET with MRI.

Conclusion
The presented PET/MRI case-based pictorial review raises awareness and strengthens the judgment of the reading physician about role of PET/MRI in staging and restaging of rectal cancer.