Ga-68 labeled DOTA-peptides such as DOTANOC, DOTATOC or DOTATATE PET-CT are currently the state-of-art-method for the detection and staging of NETs. NETs are usually small at presentation and DOTA PET has excellent sensitivity for identifying these small lesions. However, an anatomical correlate with MRI or CT is needed to identify the PET finding which warrants accurate registration for overlaying the PET on MRI/CT. The simultaneity of acquisition in PET-MRI offers unmatched registration for accurate identification of NET as exemplified. Furthermore, with the advent of integrated PET-MRI, many limitations faced with PET-CT are greatly circumvented. MRI shows a better soft tissue contrast and seems to be superior in the detection of the small liver, and bone metastases without the radiation exposure associate with the CT Scans. Hence many patients having DOTA PET-CT do end up with an additional MRI abdomen saving to patient cost, discomfort, and also physician’s difficulty in interpretation.
A 68-year old male, presented with loss of appetite. Endoscopy done revealed sub-mucosal (~1 cm) nodular lesion in the duodenum, which was biopsied and histopathologically proven to be carcinoid tumor.Ga-68 DOTATATE PET-MRI was done for further evaluation.
DOTATATE PET MIP image shows discrete focal areas of increased DOTATATE uptake in the infrahepatic region (black arrows).
TruFISP MR axial image (left)reveals a soft tissue nodular lesion (10 mm) in the medial wall of duodenum showing increased DOTATATE uptake on the PET axial (middle) and PET MR fused (right) image.
A subcentimeter (5mm) lymph node is identified in the axial T1 W image (left) with increased DOTATATE uptake on PET image (middle) and fused PET- MR image (right).
Ga-68 DOTATATE localizes in Somatostatin Receptor (SSTR) in the body, and help for identifying Neuroendocrine tumor. At present DOTATATE PETCT is being used as the criterion standard for staging, deciding treatment option like surgery and monitoring of Neuroendocrine Tumors.
In general, the lesions usually are small at presentation thus accurate localization is necessary. Sequentially acquired CT images followed by PET images in PET CT often poses difficulty inaccurate localization due to misregistration.
On the other hand, the simultaneity of acquisition in Simultaneous PET-MRI now brings an unmatched fusion of the PET and MR image in one examination so that even small lesions with increased PET uptake are better localized. In this case, a small duodenal polyp and a still smaller active peripancreatic node could be identified with an accurate localization.
This short PET-MRI Scan case was compiled by Dr. Sangeeta Taneja and Dr. Amarnath Jena (Nuclear Medicine Physician at PET-Suite @ Indraprastha Apollo Hospital, Sarita Vihar).
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