Visualization With Positron Emission Tomography, Computed Tomography, Magnetic Resonance Imaging, Positron Emission Tomography/Computed Tomography, and Positron Emission Tomography/Magnetic Resonance Imaging
A 71-year-old male patient presented with progressive flushing and diarrhea. In his medical history, a primary gastrointestinal carcinoid tumor of the terminal ileum had been surgically resected 8 years previously. For the tumor staging, whole-body PET, CT, and MRI from head to foot were performed to evaluate both the region of the primary tumor and the presence of metastases at the same time. PET was performed with a carbohydrated 18F-labeled somatostatin-receptor ligand ([18F]FP-Gluc-TOCA) using a state-of-the-art 3D full-ring PET scanner of a PET/CT (Biograph Sensation16; Siemens AG). CT was performed with a venous-dominant contrast phase using a 16-slice CT of the PET/CT. MRI was performed with a coronal HASTE, STIR, and T1-weighted TSE sequences as well as a high-resolution axial T2-weighted TSE sequence with navigator technique using a 1.5-T whole-body scanner (Magnetom Avanto; Sie- mens AG). Whole-body PET, CT, and MRI revealed an extensive nonresectable metastatic disease. The main advantage of PET is its high sensitivity in identifying cancerous areas at an early stage. However, the primary difficulty with PET is the lack of an anatomic reference frame. Whole-body CT and MRI produce large amounts of image data, resulting in the possibility of overlooking subtle pathological findings. The combination of PET with CT or MRI facilitates the accurate correlation of molecular aspects and metabolic alterations with anatomic findings and therefore improves the diagnostic value in identifying and characterizing malignancies and tumor staging in comparison to PET, CT, or MRI alone. Whole-body PET/MRI is a promising diagnostic modality because of the considerably lower radiation exposure in contrast to PET/CT and the high soft-tissue resolution of MRI (Figure).