From Hevesy to PET Nuclear Medicine Imaging Bevezet

From Hevesy to PET Nuclear Medicine Imaging

Bevezető • Személyes bemutatkozás(video): • Név, iskola bemutatása, néhány kép az iskoláról • A nukleáris medicina megalkotójának tekintik a magyar George Charles de Hevesy-t. Aki 1943 -ban Nobel díjat kapott a radioaktív nyomjelzés felfedezésért. • We are interested in nuclear • Ennek kapcsán szeretnénk a phisics: mai modern diagnosztikai • We join the Twinning eljárásokról egy rövid project on THE FIRST bemutatót tartani. EUROPEAN NUCLEAR COMPETITION FOR SECONDARY SCHOOL STUDENTS

What is Nuclear Medicine? • NUCLEAR MEDICINE IMAGING procedures IMAGING look at the bodily functions to help make your diagnosis.

Radiology and nuclear imagery In traditional radiology, one measures the relative absorption of X-Rays passing through the body. In nuclear imagery, a handful of radioactive atoms (carefully chosen to latch on to the relevant organ) are injected into the body, and the gamma rays they emit from inside are detected so as to measure the concentration of radioisotope in the organ in question.

What about the radiation? • Very small amounts of radiation are given during nuclear medicine imaging scans. • Larger amounts are used for therapy in order to target very specific areas. • The scanners (equipment) do not give off radiation.

Nuclear medicine imaging Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear medicine, in a sense, is "radiology done inside out" or "endoradiology" because it records radiation emitting from within the body rather than radiation that is generated by external sources like X-rays. In addition, nuclear medicine scans differ from radiology as the emphasis is not on imaging anatomy but the function and for such reason, it is called a physiological imaging modality. Single photon emission computed tomography(SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine. Diagnostic In nuclear medicine imaging, radiopharmaceuticals are taken internally, for example, intravenously or orally. Then, external detectors (gamma cameras) capture and form images from the radiation emitted by the radiopharmaceuticals. This process is unlike a diagnostic X-ray, where external radiation is passed through the body to form an image. There are several techniques of diagnostic nuclear medicine.

History

The origins of this medical idea date back as far as the mid-1920 s in Freiburg, Germany, when George de Hevesy made experiments with radionuclides administered to rats, thus displaying metabolic pathways of these substances and establishing the tracer principle. Possibly, the genesis of this medical field took place in 1936, when John Lawrence , known as "the father of nuclear medicine", took a leave of absence from his faculty position at Yale Medical School, to visit his brother Ernest Lawrence at his new radiation laboratory (now known as the Lawrence Berkeley National Laboratory) in Berkeley, California. Later on, John Lawrence made the first application in patients of an artificial radionuclide when he used phosphorus 32 to treat leukemia. John H. Lawrence

George Charles de Hevesy • George Charles de Hevesy (German: Georg Karl von Hevesy; 1 August 1885 – 5 July 1966) was a Hungarian radiochemist and Nobel Prize in Chemistry laureate, recognized in 1943 for his key role in the development of radioactive tracers to study chemical processes such as in the metabolism of animals. He also co-discovered the element hafnium.

Introduction to Nuclear Medicine

Nuclear Medicine Diagnoses What?

Nuclear medicine • Nuclear medicine is the medical specialty in which radioactive tracers are used for the diagnosis and treatment of diseases, for example, where patients are scanned in so-called SPECT and PET scanners. • Worldwide, around two million patients are scanned every year using nuclear medicine techniques.

An impossible problem In 1912 Rutherford set Hevesy the challenge to separate Radium-D from lead. Radium-D is an isotope of lead, that is, it has the chemical properties of lead, but with a different mass of the most common. Hevesy’s simple and ingenious idea was that the radioactive Radium-D, which could not be separated from the lead, could be detected in the body and thus could be used as an indicator or tracer for lead.

Hevesy discovered the basic principles for the indicator technique, which later evolved into nuclear medicine •

Positron Emission Tomography Single photon emission computed tomography(SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine.

Positron Emission Tomography • The technique is based on the detection of radioactivity emitted after a small amount of a (beta-positive emitter) radioactive tracer is injected into a peripheral vein. • The tracer is administered as an intravenous injection usually labelled with oxygen 15, fluorine-18, carbon-11, or nitrogen-13. • The total radioactive dose is similar to the dose used in computed tomography.

Positron Emission Tomography

Signal detector Positron Emission Tomography is an imaging technique which maps the distribution of beta-positive emitters throughout the body. The positrons (positive electrons) emitted are identified by the fact that, once they have lost their energy (their range does not exceed a few millimeters), they annihilate with an electron to yield two gamma photons each of 511 ke. V of energy and emitted back to back. Both gamma reach simultaneously a pair of opposing detectors placed on either side of the annihilation location. Electronic circuits associating these pairs of detectors are designed to identify the annihilation photons.

Coincidence circuit • • The two gamma rays emitted back to back during the positron annihilation are detected almost simultaneously by two opposite scintillators. This coincidence is a very strong signature that distinguishes them from other photons. Specific electronic circuits "coincidence" circuits pick up gamma pairs. On the figure, it is requested that the signals coming from the scintillators A and B coincide within 12 billionths of a second (nanosecond). The straight line joining the centers of detectors A and B is an approximation of the actual line of flight of the two gamma rays

FDG-PET There are 4 positron-emitting radioisotopes that are usemore than any others. These are • fluorine-18 (F-18), • carbon-11 (C-11), • nitrogen-13 (N-13) and • oxygen-15 (O-15). The reason these are so commonly used is that they have many attractive properties, one of which is that they can be easily substituted directly into biomolecules. For example: PET scanning with the tracer fluorine 18 (F-18) fluorodeoxyglucose (FDG), called FDG-PET, is widely used in clinical oncology. This tracer is a glucose analog that is taken up by glucose-using cells and phosphorylated by hexokinase (whose mitochondrial fo rm is greatly elevated in rapidly growing malignant tumors)

Average Free Range Positrons emitted by a beta-plus marker disappear after travelling a few millimetres through the body, by annihilating with an atomic electron in a process whereby both particles cease to exist.

Tumor is seen • Whole-body PET scan using 18 F-FDG. The normal brain and kidneys are labeled, and radioactive urine from breakdown of the FDG is seen in the bladder. In addition, a large metastatic tumor mass from colon cancer is seen in the liver. Animation

Producing beta-positive emitter radioisotopes

The Cyclotron and PET • The most difficult and sophisticated part of a PET installation is the cyclotron. It is a machine used to produce the radioisotopes (radioactive chemical elements) which are used to synthesize the radiopharmaceuticals (the actual substances which are used to make the functional images of the body).

Cyclotron The cyclotron was one of the earliest types of particle accelerators, and is still used as the first stage of some large multi-stage particle accelerators. It makes use of the magnetic forceon a moving charge to bend moving charges into a semicircular path between accelerations by an applied electric field. The applied electric field accelerates electrons between the "dees" of the magnetic field region. The field is reversed at the cyclotron frequency to accelerate the electrons back across the gap. When the cyclotron principle is used to accelerate electrons, it has been historically called a betatron.

History Brainchild (idea): Leo Szilard Realization: Ernest Orlando Lawrence • Leo Szilard submitted patent applications for a linear accelerator in 1928, and a cyclotron in 1929. • American physicist Ernest Lawrence received the 1939 Nobel Prize for inventing the cyclotron. Credit went to Lawrence, but Leo Szilard (Hungarian. German-American physicist and inventor) invented it first. • Szilard filed a German patent application on the cyclotron on January 5, 1929. Lawrence conceived the idea independently several months later. Lawrence's American patent application was not filed until January 26, 1932. L. Szilard (1898 - 1964) E. Lawrence (1901 – 1958)

Leo Szilard (left) talks with Ernest O. Lawrence (right) at the American Physical Society meeting in Washington D. C. , on April 27, 1935. (http: //members. peak. org/~danneng/lawrence. html)

Short half-life • The most frequently used radioisotopes in PET are: – – Carbon-11, with a half-life of 20 min Nitrogen-13, with a half-life of 10 min Oxygen-15, with a half-life of 2 min Fluorine-18, with a half-life of 110 min • be readily incorporated into an useful radiopharmaceutical, by chemical synthesis.

PET Center • This is why most of the PET installations in the world have the cyclotrons just by the side of the PET machine. • It is truly a race against the clock, once the radioactive isotope is produced, to synthesize the radiopharmaceutical and get injected into the patient, so the PET and the cyclotron should be a few minutes away from each other.

Képek készítésének ideje Nukleáris hétvége Debrecenben 2007. november 16 -18.

Látogatás a PET centrumban

Hungarian cyclotron history: Cyclotron of ATOMKI • The MGC-20 cyclotron of ATOMKI has been the major particle accelerator facility in Hungary since it started operation in 1985. • For about two decades it was the only cyclotron type accelerator in the country and was used for various research and application programs. In the biginning ATOMKI produced beta-positive emitter isotopes for Clinic of Debrecen.

Medical cyclotrons Many positron emitters have short half-lives and thus require on-site cyclotrons for application.

PET cyclotron

PET Center in Debrecen PET-CT DIAGNOSZTIKAI és CIKLOTRON KÖZPONT – BUDAPEST PET centrum Debrecen

Source • https: //www. nbi. ku. dk/english/www/george_ /de_hevesy/del 1/ • https: //en. wikipedia. org/wiki/Leo_Szilard • https: //en. wikipedia. org/wiki/Positron_emissi on_tomography • https: //www. researchgate. net/publication/86 05379_PET_tracers_and_radiochemistry • http: //www. cerebromente. org. br/n 01/pet/pe tcyclo. htm