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Questions and Answers
The two most important characteristics of an imaging modality are spatial resolution and ______ resolution.
The two most important characteristics of an imaging modality are spatial resolution and ______ resolution.
contrast
In digital imaging, you manipulate ______ to provide sufficient radiation for creating an image.
In digital imaging, you manipulate ______ to provide sufficient radiation for creating an image.
mAs
Spatial resolution is described by the quantity known as spatial ______.
Spatial resolution is described by the quantity known as spatial ______.
frequency
The smallest object that can be imaged is inversely proportional to ½ the spatial ______.
The smallest object that can be imaged is inversely proportional to ½ the spatial ______.
In digital imaging, if the object is smaller than one ______, it cannot be visualized.
In digital imaging, if the object is smaller than one ______, it cannot be visualized.
Film-screen imaging has the best spatial resolution, approximately ______ lp/mm.
Film-screen imaging has the best spatial resolution, approximately ______ lp/mm.
CR is limited to approximately ______ to 5 lp/mm.
CR is limited to approximately ______ to 5 lp/mm.
The highest spatial resolution is achieved by ______ with 15 lp/mm.
The highest spatial resolution is achieved by ______ with 15 lp/mm.
Digital Radiography has a high MTF at low spatial frequencies and has an abrupt cutoff due to ______.
Digital Radiography has a high MTF at low spatial frequencies and has an abrupt cutoff due to ______.
As spatial ______ increases, the objects that can be imaged become smaller.
As spatial ______ increases, the objects that can be imaged become smaller.
Objects with high spatial frequency are generally ______ to image than those with low spatial frequency.
Objects with high spatial frequency are generally ______ to image than those with low spatial frequency.
Fluoroscopy has a spatial resolution of ______ lp/mm.
Fluoroscopy has a spatial resolution of ______ lp/mm.
The ability of a system to record available spatial frequencies is known as ______.
The ability of a system to record available spatial frequencies is known as ______.
A system producing an image identical to the object would have an MTF of ______.
A system producing an image identical to the object would have an MTF of ______.
The focal spot size was previously our limiting factor at ______ mm.
The focal spot size was previously our limiting factor at ______ mm.
Digital radiography has improved contrast resolution but reduced ______.
Digital radiography has improved contrast resolution but reduced ______.
CR and DR have better contrast resolution than __________ because of wider dynamic range.
CR and DR have better contrast resolution than __________ because of wider dynamic range.
A 14-bit Dynamic Range DR system has __________ shades of gray.
A 14-bit Dynamic Range DR system has __________ shades of gray.
The human eye can only discern about __________ shades of gray.
The human eye can only discern about __________ shades of gray.
Optical Density (OD) on film can theoretically range from __________ to 4.
Optical Density (OD) on film can theoretically range from __________ to 4.
The highest signal-to-noise ratio (SNR) with the least __________ is desired.
The highest signal-to-noise ratio (SNR) with the least __________ is desired.
Dynamic range is the range of values that can be displayed by an imaging system in terms of __________.
Dynamic range is the range of values that can be displayed by an imaging system in terms of __________.
Increasing __________ increases the signal-to-noise ratio (SNR).
Increasing __________ increases the signal-to-noise ratio (SNR).
The practical application range of Optical Density is from __________ to 2.5 OD.
The practical application range of Optical Density is from __________ to 2.5 OD.
Interventional Radiography typically uses ______ mA to reduce time.
Interventional Radiography typically uses ______ mA to reduce time.
The lowest mA station(s) come with the option of a smaller ______ spot size.
The lowest mA station(s) come with the option of a smaller ______ spot size.
To minimize motion, use a higher ______ and a shorter time.
To minimize motion, use a higher ______ and a shorter time.
Patient dose is NOT affected by the ______ selected.
Patient dose is NOT affected by the ______ selected.
Time can be expressed in fraction or ______.
Time can be expressed in fraction or ______.
MA and Time are ______ proportional: as one increases the other decreases.
MA and Time are ______ proportional: as one increases the other decreases.
Three-phase or high-frequency generators can typically provide an exposure time as short as ______ ms.
Three-phase or high-frequency generators can typically provide an exposure time as short as ______ ms.
Single-phase generators cannot produce an exposure time less than ______ ms.
Single-phase generators cannot produce an exposure time less than ______ ms.
New mAs = old mAs x new distance squared divided by old distance squared, so New mAs = 10 mAs x 72 inches squared divided by ______ squared.
New mAs = old mAs x new distance squared divided by old distance squared, so New mAs = 10 mAs x 72 inches squared divided by ______ squared.
If the kVp is increased by 15%, the mAs must be cut in half to maintain ______.
If the kVp is increased by 15%, the mAs must be cut in half to maintain ______.
Original factors include 15 mAs and ______ kVp.
Original factors include 15 mAs and ______ kVp.
For a grid ratio of 12:1, the multiplier is ______.
For a grid ratio of 12:1, the multiplier is ______.
To convert technique for a 10 x 12 IR, the multiplier is ______.
To convert technique for a 10 x 12 IR, the multiplier is ______.
Using single phase equipment, Original Factors include 15 mAs, 70 kVp, and a ______ multiplier.
Using single phase equipment, Original Factors include 15 mAs, 70 kVp, and a ______ multiplier.
To convert technique for a grid ratio from 6:1 to 12:1 ratio, the new mAs calculated is ______.
To convert technique for a grid ratio from 6:1 to 12:1 ratio, the new mAs calculated is ______.
When converting mAs for three phase equipment, you multiply by ______.
When converting mAs for three phase equipment, you multiply by ______.
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Study Notes
Digital Imaging Fundamentals
- Spatial Resolution refers to the ability to image small objects clearly.
- In digital imaging, spatial resolution is limited by pixel size.
- The smallest object that can be visualized is limited to half the pixel size.
- The spatial frequency is measured in line pairs per millimeter (lp/mm).
- Higher spatial frequencies are harder to image.
- Contrast Resolution is the ability to distinguish between and visualize similar tissues.
- Digital imaging has a wider dynamic range compared to film-screen imaging.
- Dynamic range is the number of shades of gray a system can capture.
- Bit depth determines the number of shades of grey.
- A 14-bit system has 16,384 shades of gray.
- Window/Leveling allows viewing of specific tissues and densities.
- Signal-to-noise ratio (SNR) is the ratio of the image-forming x-rays to noise (scatter, etc.).
- Noise can limit contrast resolution.
- Higher SNR (less noise) is preferred.
- Patient Dose can be reduced by 20-50% with digital imaging but dose creep has occurred.
- mA Stations are typically available in increments of 100, with the lowest mA settings allowing for smaller focal spot selection.
- The selected mA station impacts the exposure time.
- Exposure time should generally be kept short to minimize patient motion, but it doesn't impact patient dose.
- mA and Time are inversely proportional.
- Decreasing time requires increasing mA to maintain the same mAs.
- Three-phase generators can produce exposure times as short as 1 ms.
- Portable equipment generally has fixed time options.
- Distance affects the technique. Use the Distance-Squared Law calculation.
New mAs = old mAs x new distance2 / old distance2
- 15% Rule helps adjust the technique based on kVp changes.
- Increasing kVp by 15% requires halving the mAs to maintain density.
- Decreasing kVp by 15% requires doubling the mAs to maintain density.
- Grid Ratio influences the technique; use the appropriate multiplier.
- Collimation Field Size affects the technique; use the appropriate multiplier.
- Generator Type affects the technique; use the appropriate multiplier.
- Three-phase generators require smaller mAs values compared to single-phase generators.
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