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imaging overview
imaging over view
| Question | Answer |
|---|---|
| imaging overview primary exposure factors | kvp/ma/time/sid |
| anode is placed where in the room | anode is placed towards the head (less xray towards the head) |
| ma | milliamperage which is the quantity which is tube current. |
| what does ma control? | density and brightness |
| filament | has high atomic #, k-shell binding of 69, high melting temp |
| is time indirectly or directly related to ma | indirectly related |
| kvp | kilo volts peak which which is the quality of the beam |
| kvp controls what | contrast |
| T or F no amount of mas can make up for insufficient kvp | True |
| sid | source to image receptor distance |
| sid controls what | density |
| inverse square law and formula | intensity of radiation is inversely related to the distance squared |
| inverse square law formula | I1=d2 squared I2 d1 |
| atomic number | number of protons in the nucleus. also same number of electrons in outer shell |
| atomic mass | number of protons and neutrons |
| types of tissue | muscle, adipose, |
| attenuation | weakening of the beam |
| what technical factors control attenuation | kvp and the three pt. factors. type of tissue, atomic # of tissue and number of electrons per gram |
| density or brightness | density (film) blackening to IR. brightness (electronic imaging) measure of candelence at each pixel |
| what two technical factors control density and brightness | ma and sid |
| low kvp = | more absorption, less penetration |
| high kvp = | less absorption, more penetration |
| ARRT definition density | degree of blackening or opacity of an area in a radiograph due to accumulation of black metallic silver following exposure and processing |
| formula | |
| ARRT definition brightness | measurement of the luminance of a monitor calibrated in units of candela per square meter on a monitor or soft copy |
| soft copy | image on computer |
| density is | image on film |
| hard copy | laser film |
| kvp controls | contrast |
| density/ brightness factors | pt, part, pathology etc. asites, plueral effusion, atelectasis |
| anode heel effect | variation of intensity from anode to cathode due to line focus principle |
| FSS controls only what | detail |
| FSS projected onto pt = what | effective FSS |
| chest | cathode inferior |
| abdomen | cathode superior |
| mammography | cathode toward base of breast |
| contrast resolution | density differences |
| film contrast controlled by | manufacture/ crystal size |
| faster speed gives you what | large/ larger crystal size & thicker emulsion |
| slower speed system gives you what? also what is the disadvantage | smaller/ smaller crystals and thinner emulsion. the disadvantage is exposure latitude |
| high contrast | few shades of grey, more blacks and whites/ short scale/chest. less kvp to receive less dose=less s/s |
| low contrast | many shades of grey, few blacks and whites/ long scale |
| for bone work you want what type of film | high contrast |
| beam restriction factor | contrast increases w/ collimation |
| filtration | hardens the beam and reduces pt skin dose |
| where is the filter placed | between the tube and the collimator tube housing |
| OID (air gap) | done in lue of a grid. for every 6" you add 1' SID, s/s misses the IR` |
| what do we use to test for poor screen/film contact | wire mesh test |
| over filtration = | decreased contrast |
| contrast agents | enhances density differences |
| recorded detail (on film or laser film, hard copy) | the sharpness of structural lines as recorded in the radiographic image |
| spatial resolution/ edge enhancement | the ability to see small structures. the sharpness of structural edges recorded in the image |
| factors that affect recorded detail/ spatial resolution | motion, time, ir, pixel size, voluntary and involuntary movements |
| what is the disadvantage of high speed film | higher pt dose |
| OID | as short as possible |
| SID | as long as pratical |
| what controls magnification size distortion | SID & OID |
| what factors affect IR | electronic- pixel/matrix size |
| factors that affect film screen | speed |
| an x ray is a shadow of what | anatomy |
| umbra | distinctly sharp area of a shadow |
| penumbra | imperfect, unsharp shadow surrounding the umbra |
| what are the different types of distortion | size and shape distortion |
| size | not true to size, magnification |
| shape | not true to shape, elongation and foreshortening |
| magnification is controlled by what | SID and OID |
| with increased OID | you increase SID |
| factors that control shape distortion | angle of part and angle of CR |
| visibility of detail | anything that affects contrast (contrast resolution) or density/brightness on an image |
| edge enhancement | adds artificial edge enhancement to image |
| smoothing | surpress noise, but you loose contrast |
| diamond view | siemens |
| no pratical amount of mas will make up for insufficient | kvp |
| fixed kvp technique chart | advantage is that contrast stays the same. a disadvantage is higher pt. dose |
| variable kvp technical chart | advantage is less pt dose. a disadvantage is a variable contrast |
Created by:
eckoultd1972
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