Physics and Radiobiology of Nuclear Medicine

66 6. Interaction of Radiation with Matter Fig. 6.8. Plot of linear attenuation coefficient of g-ray interaction in water (equiv ...

It is defined as the thickness of the absorber that reduces the intensity of a photon beam by one-half. Thus, an HVL of an absor ...

and the amount of lead needed to reduce the exposure of a point source of radiation by 70%. Answer Because the initial beam is r ...

Electromagnetic radiations and electrons have low LETs compared to heavy particles (e.g.,a-particles), which have high LETs. Ex ...

If 1 mCi of a radionuclide is adequately shielded by 5 HVLs of a shield- ing material, how many HVLs are needed to provide equa ...

7 Gas-Filled Detectors 71 Principles of Gas-Filled Detectors The operation of a gas-filled detector is based on the ionization o ...

72 7. Gas-Filled Detectors Fig. 7.1. A schematic diagram of a gas-filled detector illustrating the principles of operation. Fig. ...

the design of the gas detector and the applied voltage. In this region, the total current measured is equal to the number of ion ...

As the applied voltage is increased beyond the Geiger region, a single ionizing event produces a series of repetitive discharges ...

tion (current) produced by different radionuclides so that equal activities produce the same reading. In most dose calibrators, ...

Constancy Daily constancy check is performed by measuring a long-lived radioactiv- ity (e.g.,^137 Cs) in the dose calibrator and ...

Geometry Variations in sample volumes or in geometric configurations of the con- tainer can affect the accuracy of measurements ...

When these electrons neutralize the ionized molecules of the quenching gas, energy is released, which causes the dissociation of ...

The exposure rate (mR/hr or counts/min) given by the GM tube for x- rays or g-rays depends on the energy of the photons, because ...

(e) Background radiation? (f) Radiation survey of a diagnostic x-ray installation? (a) Why are halogen gases added to GM counte ...

8 Scintillation and Semiconductor Detectors 81 Scintillation Detectors As stated in Chapter 7, the detection efficiency of g- an ...

NaI(Tl) is 0.25msec and that for anthracene is 0.026msec. The faster decay time permits the use of organic scintillators at high ...

Scintillation Detectors 83 T able 8.1. Characteristics of different solid scintillation detectors.* Effective atomic Density Sci ...

Lutetium Oxyorthosilicate Detector Lutetium oxyorthosilicate (Lu 2 [SiO 4 ]O(Ce) or LSO) doped with cerium is another solid dete ...

Because semiconductors are much denser than gases, they are more effi- cient for x- and g-ray detection than gas detectors. Also ...