Radioactivity measuring instruments

Quality assurance of radiopharmaceutical preparation and use is obviously a very important topic because of its direct impact on patient diagnosis, treatment and health (see, e.g. Abreu 1996). Reference materials play only a small - but nevertheless important -role in this process, mainly in the area of calibration of radioactivity-measuring instruments. The materials of interest are all pure chemical containing calibrated activities of selected radionuclides used commonly in nuclear medicine (e.g. Co, Ga, I,... 

The radiation emitted by radioactive materials is harmful to living matter. Small quantities of radioactive isotopes are used in the process industry for various purposes for example, in level and density-measuring instruments, and for the non-destructive testing of equipment. 

Finite resolution and partial volume effects. Although this can occur in other areas of imaging such as MRS, it is particularly an issue for SPECT and PET because of the finite resolution of the imaging instruments. Resolution is typically imaged as the response of the detector crystal and associated electron to the point or line source. These peak in the center and fall off from a point source, for example, in shapes that simulate Gaussian curves. These are measures of the ability to resolve two points, e.g. two structures in a brain. Because brain structures, in particular, are often smaller than the FWHM for PET or SPECT, the radioactivity measured in these areas is underestimated both by its small size (known as the partial volume effect), but also spillover from adjacent radioactivity... 

Marie (NLP 1903, NLC 1911 ) and Pierre (NLP 1903 ) Curie took up further study of Becquerel s discovery. In their studies, they made use of instrumental apparatus, designed by Pierre Curie and his brother, to measure the uranium emanations based on the fact that these emanations turn air into a conductor of electricity. In 1898, they tested an ore named pitchblende from which the element uranium was extracted and found that the electric current produced by the pitchblende in their measuring instrument was much stronger than that produced by pure uranium. They then undertook the herculean task of isolating demonstrable amounts of two new radioactive elements, polonium and radium, from the pitchblende. In their publications, they first introduced the term radio-activity to describe the phenomenon originally discovered by Becquerel. After P. Curie s early death, M. Curie did recognize that radioactive decay (radioactivity) is an atomic property. Further understanding of radioactivity awaited the contributions of E. Rutherford. 

When the products of nuclear transformations are radioactive, they can be detected and determined quantitatively in terms of the radiations that characterize their radioactive decay. Instruments can measure the quantities of radioactive isotopes present in samples, and these methods are much more rapid and convenient than laborious chemical analyses. 

A radioactivity counter can tell if your skin is contaminated with uranium, because uranium is radioactive. If you inhale large amounts of uranium, it may be possible to measure the amount of radioactivity in your body with special radiation measurement instruments. See Chapters 2 and 6 for more information. 

In addition, the LMRI elaborates and distributes radioactivity standards and references, and provides calibrations, measurements and testings in radioactivity and dosimetry, for measuring instruments and ionising radiation sources. These services are intended for research, industry and medicine. 

Radiation protection technicians use radiation measuring instruments to iocate and assess the risk posed by contaminated materiais. Then they decontaminate the area with high-pressure cieaning equipment and remove the radioactive materiais. The work often requires the technicians to wear protective suits. The phys-icaiiy demanding work is care-fuiiy pianned and carried out, with an emphasis on safety. 

The °Y was assayed using either a Nal(Tl) solid scintillation counter to measure the bremsstrahlung or a Tri-Carb 2100TR liquid scintillation counter (Packard Instrument Co., USA). All radioactive measurements were made using a Nal(Tl) counter. 

Instrumentation and measurcmt l af radioactivity Radiation detectors. Some important biwironic circuit . The statistics of radioactive measurements. 

The methods for determination of radionuclides in the environment occupy a special place among instrumental methods. They are not competing with the other methods. These methods provide very valuable information which may be used as an indication for other environmental studies (besides radioactivity measurements) because in the general case radioactive and stable nuclides of the same element have similar behaviour (exceptions to this rule are well known and described). 

Most of the effluent and environmental radioactivity measurements are made using gamma-ray spectrometry. This is a far more cost effective approach than radiochemical analysis the Instrumental measurement can be readily automated, and detection decisions can be made more or less simultaneously for many radionuclides. The validity of those decisions, and of the corresponding detection limits, however, requires either that the peaks be Isolated and lie on a linear baseline, or that a detection limit model be employed which Is more complex than that used for "simple" counting. Baseline or interference model uncertainties should be Included, and an iterative solution is required to estimate the detection limit when spectrum deconvolution is involved. Details are beyond the scope of this chapter, but a relatively simple limiting estimate can be derived by treating the estimated standard error for a low level radionuclide peak of interest as though it were the null standard error, [12, p. 81]. 

The radioactive element promethium has a very short half-life and veiy few applications outside of the laboratory. Most of it is used exclusively in research. Promethium can also be used as a source of X-rays and radioactivity in measuring instruments. 

Figure 1 Schematic picture of a radioactivity measurement setup. The indication at the instrument (number of counts ) depends not only on the intensity of the radiation (given in Bq) but also on the counting geometry (shape and size of radioactive sample, distance, absorption and scattering effects, etc.). In addition, type and energy of the radiation and suitability of the detector plays an important role in the counting efficiency .

Properly calibrate radiation measurement instruments before each use. Train personnel in handling radiation wastes. Each department that generates radioactive wastes should develop written procedures that cover handling of, transportation, and disposal. Properly secure and store all waste materials and designate controlled areas. Dispense or draw materials only behind a protective barrier. Label refrigerators that contain stored materials. Notify the radiation control officer when receiving a contaminated shipment. 

Short-level radioactive sources are also being used as gas-solid flow measuring instruments. Generally, these units have slow response times and are not applicable for measurement in small-diameter pipes unless a special section can be created to look axially for the measurement. 

Mrs. Northway revealed that her hairdresser asked whether her head was radioactive, a grocery-checkout clerk picked up her money with tissue paper, and her son was taunted and ostracized by schoolmates. In a feature story on the trials of the Northways and McVeys, Look, magazine concluded that the entire episode caused a "kind of damage. . . which does not show up on radiation-measuring instruments and medical tests. It comes from fear and anxieties and disrupted femily i lives. It also comes from the dread that exposure to man-made radiation may produce results in future years that cannot be anticipated by ourent... 

RADIAC. An acronym derived from radioactivity detection, indication, and computation. RADIAC is used for various types of radiological measuring instruments or equipment. 

For the naturally occurring elements, many new artificial isotopes have been made, and these are radioactive. Although these new isotopes can be measured in a mass spectrometer, this process could lead to unacceptable radioactive contamination of the instrument. This practical consideration needs to be considered carefully before using mass spectrometers for radioactive isotope analysis. 

To minimize experiment time a very strong Co/Rh source was used, with an initial source strength of about 350 mCi at launch. Instrument internal calibration is accomplished by a second, less intense radioactive source mounted on the end of the velocity transducer opposite to the main source and in transmission measurement geometry with a reference sample. For further details, see the technical description in Sect. 3.3. 

In terms of atomic spectrometry, NAA is a method combining excitation by nuclear reaction with delayed de-excitation of the radioactive atoms produced by emission of ionising radiation (fi, y, X-ray). Measurement of delayed particles or radiations from the decay of a radioactive product of a neutron-induced nuclear reaction is known as simple or delayed-gamma NAA, and may be purely instrumental (INAA). The y-ray energies are characteristic of specific indicator radionuclides, and their intensities are proportional to the amounts of the various target nuclides in the sample. NAA can thus... 

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