Administration of radiopharmaceuticals, whether oral, IV, or intra-articular, for the purpose of imaging, diagnosis or treatment
Senyawa penanda yang dipakai dalam kedokteran nuklir disebut radiofarmaka.
Radiofarmaka terdiri dari dua komponen, yaitu radioisotop dan senyawa pembawanya.
Radioisotop memungkinkan suatu radiofarmaka dapat dideteksi dan diketahui lokasinya, sedang senyawa pembawa menentukan tempat akumulasi radiofarmaka tersebut.
Setelah masuk ke dalam tubuh, radiofarmaka akan menuju ke organ tertentu. Karena senyawa tersebut dapat memancarkan radiasi gamma, maka keberadaannya di dalam organ tubuh dapat diketahui dengan pemantau radiasi, baik kinetik maupun distribusinya.
All substances are made of atoms .
These have electrons (e) around the outside (negatively charged), and a nucleus in the middle.
The nucleus consists of protons (positively charged) and neutrons (neutral).
The atomic number of an atom is the number of protons in its nucleus.
The atomic mass is the number of protons + neutrons in its nucleus.
Isotopes of an atom have the same number of protons, but a different number of neutrons.
Consider a carbon atom: It has 6 protons and 6 neutrons - we call it "carbon-12" because it has an atomic mass of 12 (6 plus 6).
One useful isotope of carbon is "carbon-14", which has 6 protons and 8 neutrons.
Radioisotopes, Radionuclides: unstable isotopes which are distinguishable by radioactive transformation.
Radioactivity: the process in which an unstable isotope undergoes changes until a stable state is reached and in the transformation emits energy in the form of radiation (alpha particles, beta particles and gamma rays).
Radiation refers to particles or waves coming from the nucleus of the atom (radioisotope or radionuclide) through which the atom attempts to attain a more stable configuration.
Radiasi Type of Radiation Alpha particle Beta particle Gamma ray Symbol or Charge +2 -1 0 Speed slow fast Very fast Ionising ability high medium 0 Penetrating power low medium high Stopped by: paper aluminium lead
Peluruhan Bahan Radioaktif
Half life — symbol t1/2 — the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
To be useful as a diagnostic tool, a radioisotope must meet certain criteria. It must:
have a short half life, ideally about the same as the time required to perform the diagnosis.
not emit alpha or beta radiation, because they would be trapped inside the patient and could not be detected externally.
emit gamma radiation which is energetic enough to allow its exact source to be identified.
be energetic enough to provide useful clinical information but not so energetic as to be dangerous to the patient
From a field of more than 2300 radioisotopes, only a handful come close to satisfying the criteria for use as diagnostic tools.
Of these, the reactor produced Technetium – 99m, is by far the best, being used in more that 80% of all nuclear diagnostic tests performed.
Note: the m in the symbol 99mTc means this is the “metastable” form of Tc, which radiates gamma rays and low energy electrons.
It has a half-life of six hours which is long enough to examine metabolic processes yet short enough to minimise the radiation dose to the patient.
Technetium-99m decays by an "isomeric" process which emits gamma rays and low energy electrons. Since there is no high energy beta emission the radiation dose to the patient is low.
The low energy gamma rays it emits easily escape the human body and are accurately detected by a gamma camera. Once again the radiation dose to the patient is minimised.
The chemistry of technetium is so versatile it can form tracers by being incorporated into a range of biologically-active substances to ensure that it concentrates in the tissue or organ of interest
Once a radiopharmaceutical has been administered, it is necessary to detect the gamma ray emissions in order to attain the functional information. The instrument used in Nuclear Medicine for the detection of gamma rays is known as the Gamma camera.
The components making up the gamma camera are the collimator, detector crystal, photomultiplier tube array, position logic circuits, and the data analysis computer.
Photo Multiplier Tube
Hasil Gambar Kamera Gamma
Bone scans are typically performed in order to assess bone growth and to look for bone tumors. The tumors are the dark areas seen in the picture.