Molecular imaging

The term molecular imaging (ger .: molecular imaging ), the study of physiological processes and the diagnosis of diseases at the molecular level by means of imaging techniques together in real-time in vivo.

With the knowledge of biochemical research and molecular biology , it is in principle possible to attribute certain diseases to molecular abnormalities. For example, Alzheimer's disease is attributed to the build-up of (macro) molecular plaque in the patient's brain . The goal of molecular imaging is to detect these molecular signatures of diseases and to use them for medical diagnosis. Ideally, diseases can be diagnosed and treated with this before the onset of the first symptoms . In Alzheimer's disease, plaque deposits appear years before the clinical symptoms.

Molecular imaging, like the theranostics concept, is part of a paradigm shift in the existing health system , which is intended to lead from the current "health service" with its curative measures to a prophylactic , preventive health service. In this way, maintaining health rather than restoring it is the focus of medical care.

The principle of molecular imaging

A transport molecule or particle (for example a nanoparticle ) is coupled to a signaling molecule or atom , which is also connected to a “target-finding unit”. The latter can be certain ligands such as antibodies or their fragments, aptamers , simple peptide sequences or oligonucleotides . These ligands are specific for molecular markers of certain diseases. According to the lock-and-key principle , they bind to the diseased tissue with the highest possible selectivity and thus enrich the signaling molecules bound to them. These in turn can be detected and localized from the outside using imaging methods.

Imaging Molecules

The most advanced and established is molecular imaging with radionuclides . The decay of the radioactive isotopes can be detected with the imaging methods scintigraphy , positron emission tomography (PET) or SPECT (single photon emission computed tomography) with high sensitivity and very low doses in the pico molar range (see main article: Nuclear medicine ).

The main disadvantages of imaging with radionuclides, in addition to the high costs of these procedures, are above all the radiation exposure for the patient. They prevent these procedures from being used routinely, for example, for early detection or for permanent therapy control. For the realization of the concept of molecular imaging, work is therefore currently being carried out on a large number of additional diagnostic methods. These include above all magnetic resonance tomography , sonography (imaging using ultrasound) and optical methods (usually using fluorescence ).

Depending on which imaging molecules are targeted, i. H. are to be detected, both cellular structures and functions can be visualized. An example of functional molecular imaging is apoptosis imaging.

Examples

• ¹⁸ Fluorodeoxyglucose , the “workhorse” in positron emission tomography , especially in oncology
• Arcitumomab is a murine monoclonal antibody that is approved for the diagnosis of colorectal carcinomas and is used with ^99m Tc for SPECT.
• Somatostatin receptor scintigraphy with ⁶⁸ Ga- DOTATOC

See also

In vivo diagnostics

literature

• VR Fuchs, HC Sox Jr .: Health Affairs. 2001: 20 (5), pp. 30-42
• R. Weissleder, U. Mahmood: Molecular imaging. In Radiology , 219/2001, pp. 316-333.
• D. Piwnica-Worms, KE Luker: Imaging Protein-protein interactions in whole cells and living animals. In Ernst Schering Res Found Workshop , 49/2005, pp. 35–41.
• TF Massoud, SS Gambhir: Molecular imaging in living subjects: seeing fundamental biological processes in a new light. In Genes & Development , 2003, pp. 545-80

Individual evidence

1. ↑ R. Lamerichs et al .: Molecular Imaging: the road to better health care. In Medicamundi , 47/2003, pp. 2-9.
2. ↑ ^{a b} Wagner V, Wechsler D, Early Technology Detection: Nanobiotechnology II: Applications in Medicine and Pharmacy , VDI Technologiezentrum, 2004 ( Memento of the original from September 29, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 3.5 MB) 
3. ↑ I. Böhm et al .: Molecular imaging of apoptosis and necrosis - cell biological principles and use in oncology. In Fortschr Röntgenstr RöFo 2006; 178: pp. 263-271
4. ↑ I. Böhm et al .: Molecular imaging of apoptosis in cardiovascular diseases. in Fortschr Röntgenstr RöFo 2007; 179: pp. 780-789