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Cardiovascular Molecular Imaging: Overview of Cardiac Reporter Gene Imaging
Published in Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer, Cardiovascular Molecular Imaging, 2007
Joseph C. Wu, Sanjiv S. Gambhir
Several receptor-based PET reporter genes have also been described. The first is the dopamine 2 receptor (D2R), a 415 amino acid protein with a seven transmembrane domain, found in substantial levels primarily in the striatum (42). The D2R gene has been used as a PET reporter gene, both in an adenoviral delivery vector and in stably transfected tumor cell xenografts (43). The location, magnitude, and duration of D2R reporter gene expression can be monitored by PET detection of D2R-dependent sequestration of injected 3-(2′-[18F]-fluoroethyl)-spiperone ([18F]-FESP) probe, a high-affinity D2R ligand. The second is the somatostatin type 2 receptor (SSTr2), which is expressed primarily in the pituitary gland. When used as a reporter gene, the location of SSTr2 expression can be monitored by systemic injection of a 99mTc labeled SSTr2 peptide probe ([99mTc]-P829) and subsequent imaging with a conventional gamma camera (44). Another promising approach involves the human sodium/iodide symporter (hNIS) gene, which is expressed in the thyroid gland. The accumulation of radioactive isotopes iodine ([123I] and [131I]) has been used in nuclear medicine for the diagnosis and targeted therapy of thyroid pathology (45). In general, the main advantage for receptor-based reporter genes is that the D2R, SSTr2, and hNIS are cloned from endogenous genes (striatum, pituitary, and thyroid gland, respectively), which are less likely to evoke a host immune response (46).
Iodine is needed to maintain health
Published in Tatsuo Kaiho, Iodine Made Simple, 2017
Typical radioactive iodine isotopes include iodine 123, iodine 125, and iodine 131 (see the table). There are 15 radioactive iodine drugs, constituting one-third of all radioactive drugs. Iodine 123 has a half-life (13.2 hours) and γ ray (159 keV) energy suitable for diagnostic imaging. Iodine 123 is used for 12 diagnostic radiopharmaceuticals including ioflupane [123I]. Iodine 125 has a long half-life of 59.4 days and emits weak γ ray energy (27.5 keV), and is suitable for radiation treatment. For example, an iodine 125 seed (125I encapsulated in a 5 mm long, 1 mm diameter titanium capsule) is sold commercially. It is embedded into the focus of a prostate cancer patient using a dedicated needle.
Images from Radioactivity: Radionuclide Scans, SPECT, and PET
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
It was also mentioned in Section 6.2 that alpha and beta rays are absorbed before they can exit the body because charged particles have such short ranges. Thus, radionuclides for imaging should not emit charged particles, since beta or alpha rays will add to the undesirable effects of the radiation dose without providing a useful signal for imaging. For example, the isotope iodine-131 is useful for therapy, but less useful for imaging alone because it emits both gamma and beta rays. By contrast, a different isotope of iodine, iodine-123, emits only gamma rays and is much safer for use in imaging the thyroid.
Aptamer-based technology for radionuclide targeted imaging and therapy: a promising weapon against cancer
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Oreste Bagni, Clara Nervi
The main purpose of nuclear imaging is represented by the detection and the quantification of metabolic and molecular changes due to different pathological conditions in living subjects. This approach entails the administration of radiolabeled probes and the detection of photons produced in the process of radioactive decay and interaction with neighboring tissues. Different modalities of detection can be applied, depending on the type of radionuclide bound to the probe. In case of a gamma-emitting probe, such as the already cited 99mTc, or indium-111 (111In) and iodine-123 (123I), the appropriate technological approach is represented by gamma-camera also through single-photon emission tomography (SPECT) or hybrid SPECT/CT system [19]. On the contrary, positron emission tomography (PET/CT) approach, which is characterized by superior sensitivity, spatial resolution, and quantification capabilities, is applied when molecular probes are labeled with positron emitting radionuclides, such as fluorine-18 (18 F) and gallium-68 (68 Ga).
Theranostic approaches in nuclear medicine: current status and future prospects
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Agostino Chiaravalloti, Orazio Schillaci, Roberto Cianni, Oreste Bagni
As previously mentioned, radioactive iodine therapy (RAI) has represented the oldest example of theranostic approach to cancer. Iodine is an essential element for thyroid production of hormones thyroxine (T4) and triiodothyronine (T3). Two iodine radioisotopes are routinely used in nuclear medicine practice. The former is iodine-123 (123I), that has a half-life of 13.22 hours and emits predominant energy of 159 keV and can be applied for obtaining high-quality pre- and post-therapeutic imaging. The latter is the already cited 131I which presents the characteristics of both a beta (β−, approximately 90% of the radiation, mean: 192 keV, mean tissue penetration: 0.4 mm) and gamma (approximately 10% of the radiation, mean: 383 keV) emitter. In 1946, the radionuclide 131I was successfully applied for the treatment of thyroid carcinoma. DTC includes malignancies originating from cells delimiting thyroid follicles with three well-studied histotypes: follicular (FTC), papillary (PTC) and Hurtle cell carcinoma (HTC) [9]. Surgery, especially total thyroidectomy, represents the first choice of treatment: in such a case, the optimal surgical approach takes into account several factors such as histology, disease extent, and the presence of lymph node involvement. It is of crucial importance of preserving the neighboring anatomical structures such as nerves and blood vessels [10].