Radiating Radiation Prof. Dr. Metin TULGAR

1. Radiating RadiationProf. Dr. Metin TULGAR

2. G a m m a R a d i a t i o n g radiation; Unstable (radioactive) atomsemit raditation as they pass to stablephase. After the emission of alpha and beta particles, gamma radiation occurs in the nucleus. Radiation which results from throwing of photone from the nucleus,is an electromagnetic wave with short lenght. They do not have charge and mass, so they do not affect from electrical and magnetic fields,that is they do not deflect. Typical energy interval is between 0.1 MeV-3 MeV, but it can be out off this interval raely. Penetration distance is more than those of α and β radiations(in meters), 100 times greater than that of beta, and 10000 times than alpha. It is able to pass through a thickened concrete.

3. g radiation reactions: 24He + 49Be (C13)*613C + g 24He + 49Be (613C)*613C + g 4,00387 9,01505 13,000748 (4,00387 + 9,01505).931,5 MeV = (13,00748 + g ) 931,5 MeV in this reaction; mass of g = 0.01144 amu and its energy = 10.7 MeV

4. Interaction between Gamma Radiation and the Matterg radiation does not directly makes excitation and ionization; it is absorbed giving its energy to atoms which it encounters in its way. yasyonu direkt olarak eksitasyon ve iyonizasyon oluşturmaz. That’s why, g radiation is called indirect ionization radiation.There are 3 ways of indirect ionization: • Photoelectric action • Compton action • Pair formation

5. Photoelectric Action The photon, which is realased during gamma radiation, can rescue the electron of an atom which it comes across by giving all of its energy. This action is called photoelectric action, and electron which is pop out is called photoelectron. At this action, the atom which lost its electron becomes an ion charged +1. Photoelectric action play role in absorbtion of photon, whose energy less than 0,511 MeV, by heavy elements. g

6. Compton Action Photon gives not all of its energy to atom which it crashes, and if it can rescue the electron from its nucleus, this action is named Compton action. The electron which fly out after this action is calledCompton electron. The photon, which lossesenergy, makes an angle (θ), and goes on to its way. This photon is named as reflected photon or scattered photon. Compton action plays role in the absorbtion of photons, whose energies are between 0.511 MeV and 1.022 MeV,by light elements. g θ g’

7. Pair Formation Photon which has enough energy can make 1 electron or 1 positron around the nucleus of an atom on its way. Therefore; the matter is formed by energy of electromagnetic wave. This event is called pair formation. Energy of the photon must be bigger than2x0.511MeVfor this action to occur. The positron which occur after this reaction, disappears coming together with an electron, and this is callled as“anihilation”. g e- e+ e-

8. Absorbtion of Gamma Radiations radiations can be absorbed by photoelectric, compton action or pair formation, and loose their effect. The rate of occurance of these three actions is called absorbtion coefficent, and the summation of them are called total absorbtion coefficent. As; I0: intensity of the gamma radiation coming x: thickness of the absorbtion material (cm) I: intensity of radiation passing through x thickness material µ: total absorbtion coefficient (cm-1) I = I0.e-µx

9. The absorbtion material thickness which decrease radiation intensity to half is calledhalf value thickness. I = I0/2 I0/2 = I0.e-µx x1/2= 0,693/µ Problem: Calculate the thickness of a lead sheet which can reduce the intensity of luk g radiation with energy of 1 MeV (total absorbtion coefficient of lead for gamma radiation of 1 MeV is 0.8 cm-1). Solution: x1/2= 0.693/µ = 0.693/0.8 cm-1 = 0.86 cm = 8.6 mm

10. half value thicknesses of important protective materials enerjilere bağlı yarı değer kalınlığı (cm) 100 keV 1 MeV 10 MeV Aluminium 1.5 4.3 11 Ferrite 0.25 1.5 2.9 Lead 0.01 0.9 1.2

11. X R a y s X-Rays have the same characteristics with gamma rays; however, they have different origins. grays are nucleus originated;whereas, X - rays result from changes in energy levels of electrons of an atom or the sudden ceasation of precipitated electrons. Precipitated electrons can be ceased by an X-ray tube anode.Thus; an X-ray, with a wide spectrum that has an energy near to maximum energy level of the constituent electrons, is generated. Energy of the first few electrons that crash the anode is used as the stimulation energy. X-rays are also named as continuous ray or ray of ceasation. The most important distinct feature between X-rays and gamma rays is their wave lengths;

12. In X – ray machines; electrones, originated from heated fleming dismantle, are fastly sent to target atoms. The electron, coming with a high velocity, breakes off electron from the target orbitals, and another electron from the outer orbitals comes and settles down in the emptied places. The energy difference between two electron layers causes a photon to radiate. Television tube is an example for X-ray generator using 18 kV. anode cathode X-rays - +

13. The Difference between wave lenghts of X and Gamma Rays:λX = 10-8 - 10-10 m λg = 10-10 - 10-14 m X and gamma rays’ penetrations are proportional to their energies. They can enter inside the body and can damage the internal organs. Because their penetration distance is great, they give lower energy to small tissue cells, thus they have a lower internal radiation danger. E = hc/λAccording to energyequation;X-rays’ energies are inversely proportional to their wave lengths. The ones with long wave length are named as soft X-ray. On the other hand,X-rays with short wave length are much more intensive.

14. X – Rays in Medicine usually used for diagnostic purposes. X-ray photography devices are the most common application. The intensity of X - rays of photography devices are low.

15. Tapplication Dosages to Various Organs and Tissuesin X-ray photography devices focus film dosage for each pose (mrem) organ undergoing examinationkV mA distancefiltration skinmen gonadfemale gonad Sinuses 80 40 27 inches 3 mm Al 1040 0.1 0.3 Hand, wrist, ant. pos. 46 50 27 inches 3 mm Al 100 0.04 0.01 Chest, ant. pos. 90 3 27 inches 3 mm Al 8 0.01 0.02 Chest tomography, ant. pos. 85 12B 100 cm 3 mm Al 110 0.01 0.02 Thoracal vertebrs, ant. pos. 75 80B 110 cm 3 mm Al 480 1.0 1.3 Lumbar vertebra, ant. pos. 75 80B 110 cm 3 mm Al 480 0.5 95.0 Lumbar vertebra, lateral 85 300B 110 cm 3 mm Al 2000 2.25 270.0 Lumbo-saçral joint 90 400B 110 cm 3 mm Al 3000 2.0 350.0 Pelvis 75 80B 10 cm 3 mm Al 480 20.0 80.0 Abdomen 75 60B 110 cm 3 mm Al 360 0.5 75.0 Abdomen with Ba 90 20B 110 cm 3 mm Al 130 1.5 20.0 I.V.P. Kidney 75 80B 110 cm 3 mm Al 480 0.5 95.0 I.V.P. Utherus 75 80B 110 cm 3 mm Al 480 10.0 80.0 Knee 82 25B 110 cm 3 mm Al 180 1.25 0.4 Ankle 70 30B 36 cm 1 mm Al 200 0.1 0.025

16. Units of Radioactivity • ActivityNumber of disintegration per unit time(disintegration velocity)curie; 1 Ci = 3,7x1010 disintegration/s 1 mCi = 10-3 Ci, 1 µCi = 10-6 Ci • Absorbed Radiation Dose The concentration of absorbed radiation energy 1 Rad = 100 erg/g materyal • Radiation Dose Ionization effect of gamma and X-rays in air.1R=88.6erg/g in air • Biological Dose The harmful biological effect of radiation.rem=rontgen equivalent of man • Relative Biological Effect (RBE) = g veya X ray dose/radiation dose of granules that constitute the same effect dozu For example; 0.05rad αradiation dose have the same biological effect as 1rad γor X ray dose;RBE=1rad/0.005rad=20 • International Unit System (SI) Becquerel (Bq) 1Ci = 3.7x1010 Bq = 37 GBq