Carlton Adler Ch 41
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| what is a tomogram? | the actual image?
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| what is a tomograph? | the piece of equipment used
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| what is tomography? | the modality/ exam
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| principle of tomography | synchonized movement of two elements, objects in plane of fulcrum sharp, objects farther away blurred
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| pivot point around the movement occurs, object being examined is placed at this point | fulcrum
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| where is object being imaged placed? | fulcrum
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| method to overcome superimposition | tomography
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| three elements of tomography | tube, object, IR
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| terms used to describe section of interested in tomography | slice or cuts
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| what is the result of a tomographic image? | area of fulcrum is sharp because it has not moved in relationship to tube & IR during position
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| arc or angle the tube travels. Total distance traveled by the tube | tomographic amplitude
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| arc or angle the tube travels during the exposure | exposure amplitude
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| what kind of slices do we take in tomography | only coronal slices
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| blurring of anatomic structures lying outside to focal plane | motion blur
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| what is properly imaged in tomography | only the object lying in the focal plane
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| how is blur demonstrated on the tomogram? | objects lying outside focal plane demonstrate increasing blur the further away from the object plane
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| how does blur effect density? | increased blurring causes decreased density. Objects are more transparent, permits objects with the focal plane to be seen through the blurring
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| how is tomographic amplitude (arc) related to blur | direct relationship. Increase in arc, increase in blur
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| how is distance from fulcrum related to blur? | directly. Increase in distance of an object from fulcrum, increase in blur
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| how is distance from IR related to blur? | directly, increase in object from IR, increase in blur
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| as the tube approaches perpendicularity, what happens to blur? | blur increases
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| blurred edges or margins | phantoms
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| when are phantoms produced? | during complex tomographic motion
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| occurs when tube motion is parallel to long axis of object | phantoms
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| The tomographic arc is greater or less than the exposure arc? | greater than or equal to
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| the exposure arc is greater or less than the tomographic arc? | less than or equal to
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| what decreases phantom images | reduced section thickness and increased exposure amplitude
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| pivot point | fulcrum
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| how do you adjust fulcrum? | move table up or down OR move fulcrum up or down, patient remains stationary.
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| region within the image exhibits satisfactory recorded detail and is controlled by the fulcrum | focal plane
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| controlled by the exposure angle (amplitude) | width of the focal plane
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| what is the relationship between thickness and exposure angle? | inverse relationship- as angle increases, section thickness decreases.
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| what determines section thickness? | tomography angle
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| controlled at the table, increments of 1/2 cm or 1 cm. | section interval
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| cannot exceed the section thickness | section interval
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| most common and most widely used type of motion | linear
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| variety of motions | pluridirectional
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| types of pluridirectional movements | curvilinear, circular, elliptical, figure eight, trispiral, hypocycloidal
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| slice thickness relationship to movements | more complex motion uses thinner slices
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| must match length of time required for x-ray tube to complete the tomo amplitude | exposure time
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| what kind of mA used for tomogram? | low mA, 100 mA
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| narrow angle, small exposure amplitude, 10ยบ arc- produce thick sections, application in chest and renal studies | Zonography
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| when lesion has been localized and fine detail is needed - produces thinner sections | wide angle tomography
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| curved, used mostly for head, mandible. Tube & IR collimated to a slit and travel in opposite directions | panoramic tomography
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| technique used to produce rad image with depth perception, making it 3D | stereoradiography
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| common uses for stereoradiography | chest, skull, shoulder, sinus, FB
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