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Image chapter 7 & HW
| Question | Answer |
|---|---|
| Image magnification increases with increasing the | OID |
| Distortion primarily occurs because | subject anatomy is inclined |
| Distortion can be corrected by | Proper patient position |
| To reduce magnification one should do what | Reduce OID |
| Distortion of an x-ray image results from unequal | Magnification |
| In magnification radiography, when the subject is placed equidistant between the source and the image receptor, the size of the image will be | 2.0 times object size |
| When an object is present to one side of the central axis of the x-ray beam what happens | subject contrast will remain unchanged and the magnification factor will remain unchanged |
| To obtain minimum magnification, one should do what | postion the anatomy close to the image receptor |
| What condition contributes the least to image distrotion | A thin object at a long SID |
| To minimize magnification one should do what | Position the object as close to the image receptor as is practical |
| A foreshortened image | results from an inclined object |
| Image magnification can be reduced with the use of what | Shorter OID |
| What is not one of the factors of the geometric factors that affect radiographic quality | Collimation |
| The magnification factor is not dependent on | Focal spot size |
| The magnification factor increases with increasing what | OID |
| In mammography what condition would be most effective in improving the sharpness of detail of microcalcifications near the chest wall | Postioning the anode the same side as the chest wall |
| What is most responsible for radiographic spatial resolution | focal spot size |
| The sharpness of detail in a radiograph is best increased by the use of what | Small focal spot |
| A radiographthat shows a relative lack of FSB would be | Sharp in detail |
| An intravenous pyelogram (IVP) is routinely conducted with an anteroposterior projection to | minimize the FSB of the kidneys |
| Geometric blur is controlled prinicipally by what image system characteristic | Focal spot size |
| The best way to minimize FSB without affecting optical density is to use very | Small focal spot |
| Another term for FSB is | Penumbra |
| When one images an object lateral to the central axis of the x-ray beam the FSB will be | Larger than the cathode side |
| Increasing what is effective in reducing FSB | SID |
| When the focal spot is switched from larger to small | Penumbra will be reduced |
| FSB can be reduced ny | Reducing OID |
| Image contrast is the product of image recptor contrast and | Subject contrat |
| Spatial resolutiuon is principally affected by waht | Focal spot size |
| When proper radiographic detail cannot be obtained because of a large OID, what change in technique may ne used to improve the detail | Increase SID |
| Magnification is reduced by | Increasing SID and reducing OID |
| Focal spot blur can be reduced by what | using a small focal spot size |
| When radiographic technique factors are adjusted to provide an acceptable image and then filtration is added to the x-ray tube what will increase | Average energy of the x-ray beam |
| Ensuring good screen film contact also encures reduced | Blur |
| Use of contrast media prinicipally affects what | contrast resolution |
| Reducing field size through proper collimation usually results in improved | contrast resolution and patient dose |
| What is most often influenced by focal spot size | geometric blur |
| In a radiographic examination of the lumbar spine what technique would result in the greatest exposure of the patient | 70kVp/200mAs |
| What does not affect image blur | kVp |
| what is a principle reason for using direct exposure radiography | Better spatial resolution |
| If the other factors remain constant what would have the highest optical density | 200mA, 500ms, 90cmSID |
| An anteroposterior examination of the abdomen is taken at 80kVp, 50mAs, and 100cm SID. If the scale of contrast is to be shortened the radiologic technologist must do what | reduce kVp and increase mAs |
| Assume that the usual exposure time for a lateral cervical spine radiograph at 100cm SID is 100ms. At an SID of 90cm all other factors remaining the same , the correct exposure time would be | 80ms |
| When radiographic technique factors are adjusted to obtain an acceptable image, patient dose will increase as what increases | Grid ratio |
| Geometric blur can be reduced by | reducing focal spot size |
| When technique factors are adjusted to obtain an acceptable image motion blur will increase what | Slow radiographic intensifying screens( compared with fast screens |
| With other factors staying the same optical density will increase with increasing | mAs |
| Radiograhic contrast is increased by what | increasing grid ratio |
| When the mAs is adjusted to provide constant optical density after an increase in kVp | Motion blur is reduced if the same mA is used |
| The sharpness of structural lines or minute details on the radiograph is | detail |
| these are the factors that can be seen but not necessarily measured | Visibilty of Detail |
| These are the factors that can be measureed | Geometric detail |
| What are the 4 factors of the x-ray beam | contrast, density, detail and distortion |
| What are the two types of radiographic detail | visibilty of detail and geometric detail |
| Anything that deviates from optinium technique will do what to the visibility of detail | reduce it |
| increasing the screen speed will have what effect on detail | reduce it |
| decreasing collimation will have what effect on detail | reduce it (makes the field size larger) |
| Increasing the motion has what effect on detail | reduces it and has the greatest effect on reducing the detail |
| What are the 4 ways to reduce motion | short exposure technique, immobilization of the part, suspension of respiration and communication |
| What is the most important way to reduce motion | communication |
| What are the two properties of geomteric detail | umbra and penumbra |
| image proper or true image is | umbra |
| the light hazy area surrounding the true image | penumbra |
| What are the three factors that effect geometric detail | SID, OID and FSS |
| What is the best setting with the geometric factors to produce the greatest geometric detail | Long SID, Sort OID, and Small FSS |
| increasing the SID ____ penumbra and _____ detail | reduces; increases |
| Increasing the OID____ penumbra and _____ detail | increases ;decreases |
| Increasing the FSS ___ penumbra and _____ detail | increases; decreases |
| When do we use a long SID and why | on a Chest for a sharper image |
| If we had to increase the OId because of a situation what would we do to the SID and why | increase the SID to compensate for the increase in OID |
| When do we use a small FSS | Extremity work |
| What whappens to the focal spot as mA is increased | Blooming of the focal spot(increase in electrons) |
| What do we use to measure a focal spot size for a Pinhole Camera | >0.3mm |
| What do we use to measure a focal spot size of a Star Pattern | <0.3mm |
| What is the projection of an inclined line into a surface resulting in a smaller area | line focus principle |
| What is the purpose of the line focus principle | it gives us the heat capacity of a large focal spot and the geometric sharpness of a small focal spot |
| The area projected onto the patient and the image receptor | effective focal spot |
| the area bombarded by the electrons(at anode;target;in the tube) | Actual focal spot |
| Which focal spot is the largest | actual focal spot |
| What is the average Target Angle | 5 to 15 degrees |
| The smaller the target angle the_____ the effective focal spot is | smaller |
| The best radiograph having the most detail will have | a long SID, Short OID and Small FSS |
| What tool is used to measure the detail or resolution of the radiograph | line pair test |
| What does SOD mean | source to object distance SID-OID=SOD |
| how do you measure geometric unsharpness or penumbra | width of the focus x OID/ SOD |
| When you are measuring the geometric unshrapness whic would have the greatest detail | the smaller number |
| misrepresentation of the true size and or shape of the object | distortion |
| What are the types of distrotion | size and shape |
| what is the true distortion | size |
| what is the false distortion | shape |
| misrepresentation of the true size of an object | size distortion |
| The width of the image is to the width of the object as the distance of the image from the light source is to the distance of the object from the light source | law of magnification |
| The longer the SID the____ the magnification; the shorter the OID the____ the magnifiaction | less;less |
| What is the formula for law of magnification | image size / object size= SID/OID |
| If you increase the OID for certian reasons what should you do to SID and why | increase it to compensate for the loss of detail and increase of magnification |
| The misrepresentation of the shape of an object | shape distortion |
| what is shape distortion caused by | misalignment of the tube-object-film |
| The greater the distortion the ____ the definition | poorer |
| What is the Ideal object film and tube postion | the object and film should be parallel with each other and the tube perpendicular (90degrees) to both the object and film |
| The image is shorter than the object | foreshortening |
| the image is longer than the object | elongation |
| what is foreshortening caused by | the onject is not parallel with the film |
| what cause elongation | the tube being angled |
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