Radiotracers for SPECT brain imaging
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SPECT radiotracers for brain imaging are divided into two classes: diffusibles and not-diffusible radiotracers; this distinction lies in the ability (or not) to cross the blood-brain barrier (BBB).
The not-diffusibles radiotracers - composed of ions or polar molecules - are unable to cross the lipid double layer of cell membranes, their brain accumulation, therefore, is an indication of an altered BBB permeability, they are a classic example: pertechnetate anion (99mTcO4-), 99mTc-DTPA, 99mTc-sestaMIBI, 201Tl-chloride, 67Ga-citrate.
The diffusibles radiotracers, capable of crossing the blood-brain barrier by passive transport, are neutral, lipophilic and low molecular weight molecules. Depending on their localization mechanism, they can in turn be divided into two subclasses: perfusion and receptor-binding radiotracers.
Perfusion radiotracers are located in the brain tissue proportionally to the blood flow (for esample, (e.g. 99mTc-HMPAO and 99mTc-ECD). Receptor-binding radiotracers (for example, (e.g. 123I-IBZM, and 123I-ioflupane), instead, selectively interact with specific brain receptors (e.g. dopamine D2 and DaT). Their distribution are therefore greater in those areas of the brain that selectively express target receptors.
-<p>SPECT radiotracers for brain imaging are divided into two classes: diffusibles and not-diffusible radiotracers; this distinction lies in the ability (or not) to cross the blood-brain barrier (BBB).</p><p>The not-diffusibles radiotracers - composed of ions or polar molecules - are unable to cross the lipid double layer of cell membranes, their brain accumulation, therefore, is an indication of an altered BBB permeability, they are a classic example: pertechnetate anion (<sup>99m</sup>TcO<sub>4</sub><sup>-</sup>), <sup>99m</sup>Tc-DTPA, <sup>99m</sup>Tc-sestaMIBI, <sup>201</sup>Tl-chloride, <sup>67</sup>Ga-citrate.</p><p>The diffusibles radiotracers, capable of crossing the blood-brain barrier by passive transport, are neutral, lipophilic and low molecular weight molecules. Depending on their localization mechanism, they can in turn be divided into two subclasses: perfusion and receptor-binding radiotracers.</p><p>Perfusion radiotracers are located in the brain tissue proportionally to the blood flow (for esample, <sup>99m</sup>Tc-HMPAO and <sup>99m</sup>Tc-ECD). Receptor-binding radiotracers (for example, <sup>123</sup>I-IBZM, <sup>123</sup>I-ioflupane), instead, selectively interact with specific brain receptors. Their distribution are therefore greater in those areas of the brain that selectively express target receptors.<!--[if gte mso 9]><xml>- +<p>SPECT radiotracers for brain imaging are divided into two classes: diffusibles and not-diffusible radiotracers; this distinction lies in the ability (or not) to cross the blood-brain barrier (BBB).</p><p>The not-diffusibles radiotracers - composed of ions or polar molecules - are unable to cross the lipid double layer of cell membranes, their brain accumulation, therefore, is an indication of an altered BBB permeability, they are a classic example: pertechnetate anion (<sup>99m</sup>TcO<sub>4</sub><sup>-</sup>), <sup>99m</sup>Tc-DTPA, <sup>99m</sup>Tc-sestaMIBI, <sup>201</sup>Tl-chloride, <sup>67</sup>Ga-citrate.</p><p>The diffusibles radiotracers, capable of crossing the blood-brain barrier by passive transport, are neutral, lipophilic and low molecular weight molecules. Depending on their localization mechanism, they can in turn be divided into two subclasses: perfusion and receptor-binding radiotracers.</p><p>Perfusion radiotracers are located in the brain tissue proportionally to the blood flow (e.g. <sup>99m</sup>Tc-HMPAO and <sup>99m</sup>Tc-ECD). Receptor-binding radiotracers (e.g. <sup>123</sup>I-IBZM and <sup>123</sup>I-ioflupane), instead, selectively interact with specific brain receptors (e.g. dopamine D2 and DaT). Their distribution are therefore greater in those areas of the brain that selectively express target receptors.<!--[if gte mso 9]><xml>
References changed:
- 11. Reiche W, Grundmann M, Huber G. [Dopamine (D2) receptor SPECT with 123I-iodobenzamide (IBZM) in diagnosis of Parkinson syndrome]. (1995) Der Radiologe. 35 (11): 838-43. <a href="https://www.ncbi.nlm.nih.gov/pubmed/8657887">Pubmed</a> <span class="ref_v4"></span>
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