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