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Term 3 IP2-Unit 2
Prime & Geometric Factors
| Question | Answer |
|---|---|
| What are the 4 prime factors of the x-ray beam? | Contrast, Density, Detail, Distortion |
| This is the sharpness of structural lines or minute details on the radiograph: | Detail |
| What are the 2 categories of radiographic detail? | 1) Visibility of detail 2) Geometric Detail |
| These are factors that can be seen but not necessarily measured: | Visibility of detail |
| These are factors that can be measured: | Geometric Detail |
| In digital radiography, the term is __________ when referring to radiographic detail. | Resolution |
| Anything that deviates from optimum technique will have what effect on visibility of detail? | Reduce visibility of detail |
| Increasing motion will have what effect on the visibility of detail? | Reduce |
| Increasing speed screen will have what effect on the visibility of detail? | Reduce |
| kVp or mA that is too high or too low will have what effect on the visibility of detail? | Reduce |
| What has the greatest effect on the reduction of detail? | Motion |
| Decreasing collimation is making the field size _____________, and __________ detail. | Larger; Reduces |
| What are 4 ways to reduce motion: | 1) Short exposure technique 2) Immobilization 3) Suspension of respiration 4) Communication |
| What is the MOST important way to reduce motion? | Communication |
| Geometric detail refers to what 2 radiographic properties? | Umbra & Penumbra |
| Image proper or true image is called: | Umbra |
| The light hazy area surrounding the true image is called: | Penumbra |
| Anything that increases penumbra does what to detail? | Reduces detail |
| What factors affect Geometric Detail? | SID, OID, FSS |
| Regarding Geometric Detail and the factors that affect it, what is the best factor settings to produce the greatest geometric detail? | Small FSS Long SID Short OID |
| Of the 3 factors that affect Geometric Detail, which factor affects Geometric Detail the most? | OID |
| What would increasing FSS do to penumbra? | Increase penumbra |
| Shorter SID's do what to penumbra? | Increase Penumbra |
| Extremities would tend to require a small or large FSS? | Small FSS |
| Typically, anytime the mAs is above 100 would require what type of focal spot size? | Large FSS |
| When mAs is 50 or below the focal spot size will be __________. | Small FSS |
| Certain situations may cause for an increase in OID, in these cases what can be done to reduce the negative effects of a larger OID? | Increase the SID |
| As mA is increased, what happens to the focal spot? | Blooming (bulging) of the focal spot |
| What is used to measure the focal spot size on focal spots larger than 0.3mm? | Pinhole Camera |
| What is used to measure the focal spot size on focal spots smaller than 0.3mm? | Star Pattern |
| What is the projection of an inclined line into a surface resulting in a smaller area? | Line Focus Principle |
| The advantage of the line focus principle gives the heat capacity of a _________ focal spot and the geometric _____________ of a _______ focal spot. | Large; Sharpness; Small |
| Which is larger, the effective focal spot or the actual focal spot? | Actual focal spot |
| This is the area projected onto the patient and the image receptor: | Effective focal spot |
| This is the area bombarded by electrons: | Actual focal spot |
| What is the average target angle? | 5 to 15 degrees |
| The smaller the angle, the ________ the effective focal spot. | Smaller |
| Small angle = _________ effective focal spot | Small Effective Focal Spot |
| What tool is used to measure the radiographic detail? | Line Pair Test Tool |
| SOD: _______ _______ ________ | Source to Object Distance |
| How can you calculate the SOD? | SOD = SID - OID |
| What is the calculation for penumbra? | FSS(width) X OID ÷ SOD |
| In calculating for penumbra, the smaller the number would equal what? | Greater detail |
| This is the misrepresentation of the true size and or shape of the object: | Distortion |
| What are the 2 types of distortion? | Size & Shape |
| True distortion is _________ distortion. | Size |
| False distortion is _________ distortion. | Shape |
| This is the 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 |
| Formula for Law of Magnification: | Image width ÷ Object width = SID ÷ SOD (I/O=I/O) |
| Decreasing _______ = increase in magnification | SID |
| This is the misrepresentation of the shape of an object: | Shape Distortion |
| Shape distortion is caused by misalignment of _________, _________, or __________. | Tube; Object; Film |
| The greater the distortion, the poorer the _______________. | Definition |
| Ideally, what should be parallel and what should be perpendicular? | Object and film parallel; Tube perpendicular to both object & film |
| What are the 2 types of shape distortion? | Foreshortening and Elongation |
| What is caused when the object is not parallel with the film? | Foreshortening |
| What causes elongation? | Tube Angulation |
| Increases in magnification results in increasing what? | OID |
| Distortion primarily occurs because subject anatomy is __________. | Inclined |
| How can distortion be corrected? | Proper patient positioning |
| To reduce magnification, reduce _____. | OID |
| Distortion of an x-ray image results from unequal ____________. | Magnification |
| How much larger will an image be if placed midway between the image receptor and the light source? | 2 times larger |
| A foreshortened image results from an __________ object. | Inclined |
| What effect does focal spot size have on the magnification factor? | None |
| What effect does collimation have on geometric factors? | None |
| What is MOST responsible for radiographic spacial resolution? | Focal Spot Size |
| To increase image sharpness use a _______ focal spot size. | Small |
| A relative lack of FSB would be ________ in detail. | Sharp |
| An IVP is routinely conducted with an anteroposterior projection to ________ the FSB of the kidneys. | Minimize |
| What principally controls geometric blur? | FSS |
| Best way to minimize FSB without affecting optical density is to use a very _______ focal spot. | Small |
| Another term for FSB is _________. | Penumbra |
| Imaging an object lateral to the central axis of the beam will cause FSB to be __________ on the __________ side. | Larger; Cathode |
| What can be increased to reduce FSB? | SID |
| When the focal spot is switched from large to small, penumbra will be _________. | Reduced |
| Image contrast is the product of image receptor contrast and ___________ contrast. | Subject |
| Spatial resolution is principally affected by what? | FSS |
| Ensuring good screen film contact will also ensure reduced __________. | Blur |
| Use of contrast media principally affects ____________ resolution. | Contrast |
| Increasing collimation results in improved ___________ resolution and patient dose. | Contrast |
| Geometric blur is most influenced by _____________ _______ _______. | Focal Spot Size |
| kVp does what to image blur? | Nothing |
| Direct exposure radiography is used for better ______________ resolution. | Spatial |
| Increasing grid ratio will have what affect on radiographic contrast? | Increase |
| When the mAs is adjusted to provide constant optical density after an increase in kVp, motion blur is reduced if the same _____ is used. Why? | mA; mAs is adjusted by reducing time (shorter exposure) which reduces blur (motion) |
| the ability of an imaging system to discriminate between two adjacent high-contrast objects. | Spatial resolution |
| When an object is present to one side of the central axis of the x-ray beam what will happen to subject contrast? | Nothing |
| When an object is to one side of the central axis of the x-ray beam, what will happen to magnification? | Nothing |
| What does kVp do for the visibility of detail? | Nothing |
| What will increasing mAs do for the visibility of detail? | Nothing |
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