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SMU-DDE-Assignments-Scheme of Evaluation PROGRAM SEMESTER SUBJECT CODE & NAME BK ID SESSION MARKS Q. No 1. A Bachelor/Diploma in Medical Imaging Technology III BMI 301 – Medical and Radiation Physics-II B1975 WINTER 2015 30 Criteria Marks Total Marks Define scattered radiation. Explain the various beam restricting devices. (Unit 1, Page No.3, 9 - 11 ) 1 10 Define of scattered radiation The radiation emitted by atoms or molecules after bombardment by a primary radiation is known as secondary radiation. Beam restrictors can be classified into three categories: 3 1. Aperture diaphragms 2. Cones and Cylinders 3. Collimators Aperture diaphragms: Of all these beam restricting devices, aperture diaphragm is the simplest. It is attached to the head of the X-ray tube, and it is fundamentally a diaphragm made of either lead or lead-ruled metal. One of the major applications of aperture diaphragm is in dental radiography. As studied in the previous section, radiographic extension cones are considered as variations of the aperture diaphragm. An aperture diaphragm is usually designed to be employed with a particular film size at a given distance, which forms its limitation. Because of this disadvantage, it does not easily fit different distances and sizes of the films. Cones and cylinders: This is the second type of X-ray beam restrictor that comes in two basic shapes: conical and cylindrical. The flared shape of a cone would seem to be the ideal geometric configuration for an X-ray beam restrictor. However, the flare of the cone is usually greater than the flare of the X-ray beam, in which case the base plate that attaches the device to the tube housing is the only part that restricts the X-ray beam. Cylinders may be equipped with extensions to increase their length for giving better beam restriction. A major disadvantage of aperture diaphragms, cones and cylinders is the severe limitation they place on the number of available field sizes. Collimators: The radiographic X-ray beam is usually focused with the help of a device known as collimator. Thus, the most widely used form of beam restriction is a collimator. A collimator has two sets of lead shutters that are adjustable in an X-ray unit. A specialised technologist is able to view the field that is required to be irradiated through a collimator. This way the technologist can isolate regions scan to produce radiographic images of only those 3 3 SMU-DDE-Assignments-Scheme of Evaluation 2. A 3. A regions. Collimation is important, because of the large size of the anatomy of the lumnar spine, which will radiate scatter radiation when the lateral lumbar spine is imaged. Posterior, within the skin line of the patient, collimation of the X-ray beam will lead to a considerable reduction in scatter radiation and much improved image quality. Define radiographic grid. Discuss various types of radiographic grids. (Unit 2, Page No. 16,18,22-24) Grids greatly improve the quality of the radiographic image by 1 10 filtering out much of the scattered radiation produced during a radiographic examination. 9 Single grids: A grid that has a high frequency and thin single strips of interspace material. Multi-leaf grids: A device made of individual leaves of tungsten or any other material having a high atomic number, which can move about autonomously in and out of the particle beam path to block it. Parallel grids: In the parallel grid model, the lead strips run parallel to each other. As the strips are in the vertical direction, they do not align themselves with the primary beam. Focused grids: The scattered radiation is effectively reduced by focused grids. The lead strips are skewed progressively as they move away from the centre of focused grids. It is of paramount importance to use focused grids correctly and carefully to realize the full effectiveness of these grids. Stationary grids: Stationary grids are located at a stationary position, and during exposure these grids do not move. These grids are generally used in mobile radiography. Cross-hatched grids: A cross-hatched grid is also called as crisscross grid, which is a composite of two grids with strips of lead placed perpendicular to each other. Discuss the importance of radiation protection. (Unit 7, Page No. 119-120) 4 10 The protection of environment and people from the damaging effects of the ionizing radiation, including electromagnetic radiation that is high energy and particle radiation, is known as radiation protection or radiological protection. Radiation protection can be divided into three categories, i.e., medical radiation protection, occupational radiation protection, and public radiation protection. The protection of patients is the medical radiation protection. The protection of workers is the occupational radiation protection. The protection of individual members of the public and of the complete population is the public radiation protection. Three factors manage the amount, dose, and radiation obtained from a source. The combination of the following three factors controls the radiation exposure: 1. With the increase in distance, the dose decreases because of the inverse square law. SMU-DDE-Assignments-Scheme of Evaluation 2. The second factor is shielding. A mass of absorbing material located around a reactor decreases the radiation to a level safe for humans. This absorbing material is known as a biological shield. 3. Decrease in time of the radiation exposure lessens the effective dose. Practically, radiation protection is a task of selecting a combination of the three factors for a cost-effective solution. It is of great significance that the radiation personnel and workers be protected when they work during the operational procedures. There are many protective devices, such as protective clothing, which are available in every X-ray room. These devices are used to protect the workers from the unnecessary exposure to both the primary and scattered beam. Proper protection measures are required to be taken to protect the staff members, patients, public, instruments, personnel and monitoring areas. Protection of medical staff members and patients: While using ionizing radiation to examine female patients of reproductive age, possible risks and hazards to the embryo should be considered. Alternative imaging modalities and methods not using ionising radiation should be taken into account. Examination with potential high patient doses, such as computed tomography assessments, should be performed after a suitable clinical judgment by the radiologist. Protection of personnel: The national laws and international recommendations should be followed to avoid occupational exposure of pregnant radiation workers. According to the ICRP recommendations, the pregnant diagnostic radiographers should not participate in the assessment that deals with Xray units and equipment. Protection of public: Common public should not be allowed to enter the unsupervised controlled areas to avoid radiation exposure. Only the person who is required to go through an X-ray procedure should be allowed to enter the X-ray rooms and units. 6 *A-Answer Note –Please provide keywords, short answer, specific terms, specific examples (wherever necessary) ***********