Applying PET/MR in Neuroendocrine Tumors - Imaging Dynamic Processes in Both Modalities

Neuroendocrine Tumors

Neuroendocrine tumors (NET's) are characterized, among other features, by presence of high concentration of somatostatin receptors. In recent years, for purposes of Positron Emission Tomography (PET) imaging, somatostatin receptor ligands have been labelled with the positron emitting radioisotope 68Ga to form molecules that bind to these somatostatin receptors that are present in high concentration in NET's and in low concentrations, if at all, in normal tissues. In the last 10-15 years, radioactively labelled versions of these molecules have been used for both diagnostic and therapeutic purposes in the management of patients with NET's. The main goal of this study is to assess the feasibility of performing dynamic 68Ga-DOTATATE PET in the PET/MRI system and analyzing the effect of diffusion and perfusion over Ki values.

Working hypotheses 1. The PET/MR system will provide dynamic PET images of at least comparable quality compared to PET/CT. Dynamic PET/MR will be feasible, with the 45 minute dynamic PET acquisition occurring during the MR sequences, eliminating the need for the patient to undergo two separate lengthy studies. 2. Diffusion and perfusion parameters extracted from MRI sequences will provide information that improves the process of Ki evaluation. 3. The use of advanced statistics methodologies, such as those used in radiomics, to correlate Ki data with diffusion and perfusion data will provide a quantification tool that will improve staging, prediction and monitoring after treatment. 4. Parametric Patlak Ki images calculated from the dynamic series of PET images will show better contrast between tumors and normal tissue, as compared to contrast in the conventional static images obtained from the last time frame of the dynamic image series. Tumors identified on the static PET image will be visualized at least as well on Patlak Ki images, and possibly additional tumor foci may be identified. MRI should assist in confirming and interpreting such findings. Research plan Population: 50 patients with NETs that have evidence of at least one abdominal lesion with diameter greater than 2cm. All patients will be aged 18 years or older of both sexes. Inclusion criteria: Patients with confirmed NET. Exclusion criteria: Patients younger than 18 years; pregnancy; other known active malignancy; contraindication to MRI tests or intravenous contrast agents.

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