RT 131 - control of scatter radiation beam restriction - P.P.

image forming x rays - 3 x ray paths
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Terms in this set (58)
image forming x rays - 3 x ray paths
-scatter (compton)
-absorbed in patient
-transmitted through patient
photoelectric absorption
x rays absorbed in patient
scatter adds _____ to the image without adding any ______
fog / patient info
scatter causes _____ to decrease
contrast
the two major factors that affect the amount of scatter produced and exiting the patient
-part thickness
-beam field size
volume of tissue depends on 2 things
-part thickness
-beam field size
higher kVp = _____ in scatter
increase
approx ____% of x rays incident on the patient reach the IR
1%
increasing the volume of tissue irradiated results in ______ scatter production
increased
increased thickness will _____ the volume of the tissue
increase
increased field size will ____ the volume of tissueincreasebeam restricting devices decrease the _____ and the ____x ray beam field size and the amount of tissue irradiatedgrids are used to _____ image qualityimprovegrids improve images by ...-absorbing scatter that exits the patient -reducing the amount of scatter reaching the image receptorcollimation = (3)-reduced scatter -reduced dose -improved contrast resolutionbeam restriction limitspatient exposurebeam restriction ____ the amount of scatter produced within the patientreducesa beam restricting device changes the ___ and ___ of the primary beamshape and sizeincreasing collimation meansdecreasing the field sizedecreasing collimation meansincreasing the field sizeto maintain exposure to the IR ____ must be increasedmAsbeam restriction _____ patient dosedecreasesbeam restriction ____ scatter produced within the patientreducesbeam restriction ___ scatter the IR is exposed toreducesbeam restriction ____ radiographic contrastincreasesincrease Collimation: patient dose ____decreasesincrease collimation - scatter radiation _____decreasesincrease collimation - radiographic contrast ____increasesincrease collimation - (film screen) radiographic density _____decreasesincrease collimation - (digital) quantum noise ____increasesincrease field size - patient dose _____increasesincrease field size - scatter radiation ____increasesincrease field size - radiographic contrast ___decreasesincrease field size - (film screen) radiographic density ____increasesincrease field size - (digital) quantum noise _____decreasesaperature diaphragma flat piece of lead (diaphragm) that has a hole (aperture) in it and is placed directly below the x ray tube windowcones and cylindersan aperture diaphragm that has an extended flange attached that varies in length and shapecollimatorlocated immediately below the tube window, has two or three sets of lead shutters that limit the x ray beamBecause of the aperture's proximity to the radiation source (focal spot), a large area of _______ surrounds the radiographic image.unsharpnessAperture's size and shape can be changed, the projected field size is or is not adjustable.is notA _______ is essentially an aperture diaphragm that has an extended flange attached to it.cone or cylinderCones and cylinders limit _____ surrounding the image than aperture diaphragmsunsharpnesscones and cylinders come in ____ sizeslimitedcones and cylinders may or may not be interchangeable among tube housingsmay not be_____ are more useful than cones (less unsharpness)cylindersCones and cylinders are almost always made to produce a _____ projected field.circular______ are considered the best beam-restricting deviceCollimatorsLocated immediately below the tube window; has two or three sets of lead shutters that limit the x-ray beamcollimatorscollimators are equipped with a _______ source and a mirror to project a light field onto the patientwhite lightcollimators are equipped with an x-ray _______ guide in case of light failurefield measurementcollimators are equipped with a ______ template with _______plastic / crosshairsautomatic collimators are also calledPBL (positive beam limiting device)automatic collimatorsAutomatically limits the size and shape of the primary beam to the size and shape of the IRCollimators have two sets of ________ that are used to change the size and shape of the _________.lead shutters / primary beamLimiting the size of the x-ray field to the anatomic area of interest will _______ scatter production and ______ patient exposure.decrease / reduce____ to the anatomic area of interest is an important radiation safety practice that should be routinely performed.CollimatingLimiting the use of grids or using a grid with a lower grid ratio will ______ the radiation exposure to the patientdecreasePlacing a lead shield on the x-ray table _____ scatter radiation.absorbs