Radiotracers available

Nuclear medicine involves the use of radioactive substances to diagnose and treat diseases. It can be used to determine the health of a patient, track the course of a disease, and measure the effect of treatment. Nuclear medicine imaging is used to provide functional information at the molecular and cellular level via the injection of radioactive tracers. Imaging can be performed on either positron emission tomography (PET) or single-photon emission computed tomography (SPECT), and the most commonly used radioisotopes include:
-        PET (Fluorine-18, Iodine-124, Gallium-68)
-        SPECT (Technetium-99m, Iodine-123, Indium-111)
All tracers with an * are or have been used in a clinical setting at the department of nuclear medicine at the NKI-AVL, tracers with an ᵠ are also routinely produced at the NKI-AVL.

General tumor characterization

F18-FDG * (fluoro-2-deoxy-D-glucose) is a marker for tissue uptake of glucose. Highly metabolic tissue, such as the heart, brain, and most malignant tissue, have high uptake of FDG. Thus, FDG is excellent for identification and characterization of a wide variety of tumors. FDG is ineffective for slow-growing tumors such as prostate tumors.
F18-FLT * (3'-deoxy-3'-[(18)F]fluorothymidine) is a thymidine analog that measures cell proliferation. It has comparable sensitivity to FDG and usually higher specificity. FLT is effective in the brain due to the low uptake of FLT in normal brain tissue.
F18-HX4 * (flortanidazole) or F18 FAZA (fluoroazomycin-arabinoside) are both hypoxia markers that are effective in measuring hypoxia in tumors. F18-HX4 is currently being used in patients with lung cancer and head & neck tumors. (Disclaimer: F18-HX4 is only available if the study has been approved by Siemens)
Tc99m-Sestamibi or Tc99m-Tetrofosmin ᵠ are mainly used in cardiac imaging, but are typically used at our institute in breast cancer patients to evaluate the effect of neoadjuvant chemotherapy.

Neuro-endocrine system

Ga68-DOTATATE ᵠ (DOTA-octreotate) is a radiolabeled somatostatin analog that binds to somatostatin receptors. It is typically used to image neuroendocrine tumors.
111In-pentetreotide is another somatostatin analog which is often used for imaging of neuroendocrine tumors. It has high sensitivity in detecting pancreatic neuroendocrine tumors.
Radioactive iodine * (I124 for PET or I123 for SPECT) can be used to visualize local remnant thyroid tissue after tumor resection, or visualize distant metastasis of thyroid cancer. Iodine is bound in thyroid cells to precursors of thyreoglobuline. In the clinical setting these scans are used to predict response to Iodine therapy or detect malignant disease. 123I-MIBG ᵠ (meta-iodobenzylguanidine) is a radiolabeled molecule similar to noradrenaline that is taken up by adrenergic tissue such as neuroendocrine tumors.

Genitourinary system

F18-choline * is taken up by tissues with increased metabolism since choline is an important component in the buildup of phospholipid cell membranes. It is mainly used in the detection of prostate tumors, which have low uptake of FDG and FLT, but it can also be used in the detection of gliomas.

Ga68-PSMA  ᵠ (prostate-specific membrane antigen, GCP-II) is a transmembrane protein that is over-expressed in human prostate tissues. Uptake in prostate tumors is much higher than healthy tissue, and uptake is usually more profound than 18F-choline.
Tc99m-MAG3 ᵠ (mercaptoacetylglycylglycylglycine) binds to blood proteins and thus has fast renal excretion. It is effective for measuring renal function and will thus be taken up by the kidneys. A dynamic acquisition can be used to measure kidney extraction and excretion. Tc99m-DMSA ᵠ (dimercaptosuccinic) is a water soluble chelating agent that is commonly used to measure the morphology, structure, and function of the kidneys.

Nervous system

F18-DOPA is a radiolabelled analog of L-DOPA, a precursor to neurotransmitters such as dopamine, norepinephrine, and epinephrine. It is commonly used in the early diagnosis of Parkinson’s disease, but it can also be used in the imaging of neuroendocrine tumors.
Tc99m-HMPAO (exametazime) is a lipophilic molecule used to visualize brain perfusion patterns to show brain ischemia, cerebrovascular accident, brain trauma or aid in the differential diagnosis Alzheimer-Dementia. Regional accumulation is dependent on perfusion, after which it accumulates in glia cells and neurons through specific and a-specific binding.
I123-IBZM (3-iodo-6-methoxybenzamide) binds to dopamine-D2-receptors, which are concentrated in the striatum (nigrostriatal pathway). In a clinical setting the scans aid in the differential diagnosis between Morbus Parkinson, multiple system atrophy or progressive palsy. The IBZM and FPCIT scans are often combined. I123-FPCIT (N-ω-fluoropropyl-2ß-carbomethoxy-3ß-{4-iodophenyl}nortropane, DaTSCAN) is a cocaine analog that has high affinity for the dopamine-transporters. In a clinical setting the scans aid in the differential diagnosis between Morbus Parkinson and tremors. F18-DOPA PET can be performed as an alternative.

Skeletal system

Tc99m-oxidronate ᵠ (HDP – hydroxydiphosphonate) is commonly used in bone imaging for the detection of altered osteogenesis. Thus, it is useful in the detection of bone tumors.

Antibody-conjugates

Zr89 * or In111 can be labelled to various monoclonal antibodies or conjugates to study biodistribution and tumor targeting. Certain antibodies can be purchased as a radiolabeled form or may be produced at the department of Nuclear Medicine, including trastuzumab, cetuximab, and bevacicumab

Miscellaneous tracers

99mTc-albumin nanocolloid ᵠ, with/without ICG, is effective in sentinel node detection during surgery. 99mTc-macrosalb ᵠ (LyoMAA or MAA) is used for internal radiotherapy planning for techniques such as 90Y microsphere treatment for hepatocellular carcinoma. It is also used in lung perfusion measurements. MAA gives a reasonable estimate to the absorbed dose of the tissue.

Radionuclide therapies

In the clinical setting radionuclide therapy can be used for the treatment of neuroendocrine malignancies, lymphoma, and metastatic disease in the liver and skeleton. The isotopes generally used for therapies are long-lived including Yttrium-90, Luthetium-177, Radium-223, Iodine-131, Samarium-153m, Strontium-89 and Rhenium-186. Though possible in certain cases, these isotopes are less suitable for imaging.

Clinical guidelines and background

Clinical guidelines
Clinical practice:
Overview in imaging mouse tumors:
PET for cancer imaging:

 

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