Approach to Oncologic Imaging

Approach to Oncologic Imaging

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Oncologic Imaging in Nuclear Medicine

In oncology, nuclear medicine provides whole-body analysis using various radiotracers that are utilized by tumors in such molecular pathways as glucose utilization, neurotransmitter function, and receptor uptake. The most commonly used oncology studies are F-18 FDG PET/CT and Tc-99m MDP bone scan.

F-18 FDG: A glucose analog, F-18-labeled fluorodeoxyglucose is taken up by many types of tumor cells in the glycolysis pathway and is trapped after phosphorylation by hexokinase. Three-dimensional images are obtained with a circular array of detectors and a CT scanner in the PET/CT bore.

Tc-99m MDP and F-18 NaF: Both Tc-99m MDP and F-18 NaF localize to regions of increased bone perfusion and osteoblastic response. Both types of bone scans can be used in oncologic imaging, although Tc-99m MDP bone scans are performed more commonly.

I-123 and I-131: Radioactive iodine is incorporated into normal and cancerous thyroid tissue through the sodium-iodide symporter. Dedifferentiated tumors may lose this symporter and thus their radioactive iodine avidity. F-18 FDG PET/CT is useful for dedifferentiated and anaplastic tumors.

Ga-68 dotatate and In-111 octreotide: Somatostatin receptors take up these tracers and allow for neuroendocrine tumor imaging. As F-18 FDG has low or variable avidity for these types of tumors, these are the tests of choice for pulmonary carcinoid and well-differentiated neuroendocrine tumors.

Ga-67: Rapidly dividing tumor cells utilize Ga-67 similarly to ferric ion and thus show higher uptake compared to surrounding tissue. Historically used to stage and follow therapy in lymphoma patients, it has been largely replaced by F-18 FDG PET/CT.

MIBG: An analog of norepinephrine, metaiodobenzylguanidine, localizes in benign and malignant neural crest tissue, where it is stored in neurosecretory granules. Imaging with I-123 MIBG is most common; therapy with I-131 MIBG is also available at some centers. Ga-68 dotatate PET/CT can also be used for diagnosis.

F-18 fluciclovine and Ga-68 PSMA: Both are used for prostate cancer imaging, as fluciclovine is an amino acid analog that is used by prostate cancer cells and PSMA interacts with the prostate-specific membrane antigen.

PET/CT

Provides whole-body analysis of functional and anatomic data for myriad tumors. Clinical oncologic applications include staging, restaging, therapeutic response, and detection of unknown primary and incidental tumors.

• F-18 FDG PET/CT: Most common radiotracer used with PET/CT, as many tumors are F-18 FDG avid
• Ga-68 dotatate PET/CT: High affinity for somatostatin subtype 2 receptors; useful for well-differentiated gastrointestinal neuroendocrine tumors, medullary thyroid cancer, paraganglioma, and neuroblastoma
• F-18 fluciclovine and Ga-68 PSMA PET/CT: Detect primary/recurrent tumor and metastases in patients with prostate cancer

MIBG Scintigraphy

MIBG scintigraphy remains common for staging of neuroblastoma in children. The sensitivity of MIBG for neuroblastoma is ~ 90%. Ga-68 dotatate PET/CT is sensitive for paragangliomas and neuroblastoma and provides a higher resolution scan in a shorter time.

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Tags: Diagnostic Imaging Nuclear Medicine

May 7, 2023 | Posted by admin in CARDIOVASCULAR IMAGING | Comments Off

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