RAD 1126 FINAL

What does the angle of the anode target create in relation to the effective focal spot?

An effective focal spot much smaller than the actual area bombarded by electrons.

How does a smaller focal spot affect spatial resolution?

It increases spatial resolution.

What is penumbra in the context of x-ray imaging?

The blur created by x-rays emitted from various angles of the focal spot.

How is focal spot size related to penumbra?

Focal spot size is directly proportional to penumbra; doubling the FS size doubles the penumbra spread.

What is the actual focal spot?

The area that is bombarded by electrons, generating significant heat.

What happens when the focal spot is made smaller using a shorter filament?

It concentrates electrons in a smaller area, generating more heat.

What size is the effective focal spot when viewed from the image receptor perspective?

About the size of a pinhead, approximately 1mm.

What is the line focus principle?

A principle stating that a smaller effective focal spot improves spatial resolution.

Typical anode angles used in most x-ray tubes range from what degrees?

15 to 17 degrees.

What are the dimensions of an effective focal spot for a large focal spot?

1 to 2 mm in size.

What are the dimensions of an effective focal spot for a small focal spot?

0.5 to 1 mm in size, which is 4 times smaller.

What defines the effective focal spot from the image receptor perspective?

It is a line perpendicular to the long axis of the x-ray tube.

What can limit spatial resolution in x-ray imaging?

If the pixel size is larger than the effective focal spot.

What is the anode heel effect?

The drop in intensity of photons as they escape the anode due to the angle.

How does the anode heel effect change with bevel angles?

It increases when the bevel of the target is reduced.

What is recommended positioning of the patient relative to the heel effect?

The thicker portion of the patient should be placed toward the cathode side of the beam.

What affects the severity of the anode heel effect?

It is increased with larger focal spots and reduced angles.

At what SID is the heel effect more pronounced?

At shorter source-to-image distances.

Is the size of the focal spot directly or inversely proportional to spatial resolution?

Inversely proportional.

Can an increase in focal spot size affect magnification?

No, it does not affect magnification.

What happens to the penumbra when focal spot size increases?

The penumbra is increased.

What is the relationship between actual focal spot size and spatial resolution?

A smaller actual focal spot increases spatial resolution.

What are the consequences of excessive heat generation in x-ray tubes?

It can damage the tube and reduce image quality.

What aspect of the x-ray imaging process does the effective focal spot primarily influence?

Image sharpness and resolution.

In terms of heat dispersion, why is it problematic to decrease the focal spot size too much?

It concentrates heat in a smaller area.

What is a practical example of applying the line focus principle in imaging?

Using a steeper anode angle to create a smaller effective focal spot.

How does the anode bevel angle affect the effective focal spot?

As the angle is reduced, the effective focal spot also decreases in size.

What is the effective focal spot in imaging terms?

The perceived size of the focal spot from the image receptor's view.

Can the actual focal spot size compromise spatial resolution?

Yes, a larger actual focal spot compromises spatial resolution.

Why is the anode typically located on the left side of the x-ray tube?

To optimize positioning for radiographers and the heel effect.

What measurement is used to define the effective focal spot regarding filament length?

The effective focal spot varies with the length of the filament used.

How does the focal spot size correlate with the quality of an x-ray image?

A smaller focal spot typically leads to a sharper image.

What phenomenon occurs due to the emission of x-rays from different angles within the focal spot?

The spread of penumbra on the image.

What critical aspect of anode design helps manage heat generated during exposure?

The bevel angle of the anode.

How does x-ray tube geometry impact the effective focal spot?

It shapes the effective focal spot’s apparent size and distribution.

What is an implication of not managing the anode heel effect?

It could lead to uneven exposure across the imaging receptor.

What role does the thickness of the anode material play in the heel effect?

Thicker materials can increase the anode heel effect.

In imaging applications, what is the importance of maintaining optimal anode angles?

To achieve the best possible image quality and minimize heel effects.

What relationship exists between pixel size in digital imaging and spatial resolution?

Pixel size must be smaller than the effective focal spot for optimal spatial resolution.

What can occur if the anode angle is too shallow in x-ray tubes?

It may lead to excessive penumbra and poor image clarity.

What effect does scattered radiation have on images?

Scattered radiation reduces both grayscale and contrast.

Where is scattered radiation produced?

Scattered radiation is produced from inside the patient.

What is the relationship between tissue exposure and scatter radiation?

The amount of scatter radiation produced is a direct function of the amount of tissue exposed.

What role does collimation play in scatter radiation?

Collimation reduces the amount of scatter radiation.

What happens when kVp is increased in relation to scatter?

A higher percentage of total exposure comes from scatter as photoelectric effect is reduced.

What is a benefit of using higher kVp?

Higher kVp provides more tissue information due to its long scale.

What should be done to field size to control scatter?

Field size should be reduced whenever possible to control scatter.

How do larger parts affect scatter interaction?

Larger parts increase the percentage of scatter interactions occurring.

What is a compression paddle used for?

It is used to compress the body, leading to a slight decrease in the amount of scatter.

What exception exists regarding scatter with chest imaging?

Air in the chest has low tissue density and does not contribute greatly to scatter.

What is the function of a grid in radiography?

A grid intercepts some of the scatter in the remnant beam.

Who invented the grid and when?

Gustav Bucky invented the grid in 1913.

What innovation did Dr. Hollis Potter introduce to grids?

He created a moving (reciprocating) grid to reduce white line artifacts.

What percentage of scatter do modern grids attenuate?

Modern grids attenuate 70% - 80% of scatter.

What does a grid ratio indicate?

The grid ratio is defined as the relationship of the height to the width of the interspace between the lead strips.

How does grid ratio affect contrast?

Higher grid ratio leads to higher contrast.

What does an increase in grid ratio require regarding tube alignment?

It requires more accurate tube to image receptor alignment.

What is grid frequency?

Grid frequency is the number of lead strips per inch or cm when scanning across the grid.

How have improvements in lead foil affected grid design?

Improvements allowed more lead lines per inch, enhancing grid efficiency.

What is the primary benefit of using a grid?

To improve subject contrast in the resulting image.

What is the most important consideration when using grids?

Increased patient dose due to required increases in exposure technique.

What part thickness indicates the need for a grid?

Parts greater than 10 cm (4 inches) generally require a grid.

What is the Bucky factor?

It distinguishes the exposure needed with and without a grid.

What does selectivity measure in a grid?

Selectivity measures the ratio of primary radiation transmitted to scattered radiation transmitted through the grid.

What is the Contrast Improvement Factor (CIF)?

It measures the effectiveness of a grid by comparing densities across two films.

What happens if exposure isn't increased when using a grid?

The image would be light or grainy due to photon starvation.

What is a focused grid?

A grid where angled grid lines match up with the divergence of the x-ray beam.

What is grid cut-off?

When a grid absorbs primary photons as well as scattered photons, causing grid lines to appear.

What causes the appearance of grid lines in an image?

Grid lines appear when photons strike the grid's lead lines.

What effect does incorrect SID have?

It can cause symmetrical grid cut-off.

How can placing a focused grid upside down affect imaging?

It causes the worst case of grid cut-off.

What does Virtual Grid software do?

It cleans up the scatter effect in imaging.

What is the significance of synergies like SmartGrid + Smart Noise Cancellation?

They enhance image quality by reducing noise and scatter.

How does the size of the field impact scatter?

A larger field size increases the amount of scatter produced.

What is the technique used to ensure optimization with grids?

Adjusting exposure parameters based on grid type.

What does a compression paddle help reduce in imaging?

The amount of scatter.

What is the effect of scatter when using a moving grid?

It improves image quality by reducing grid line artifacts.

What impact does part density have on scatter production?

Higher density increases scatter production.

Why is it advantageous to use grids for thicker body parts?

Grids help control the scatter produced from increased tissue.

What is the general horizontal plane in grid manufacturing?

The lead strips are tilted to align with the x-ray beam divergence.

What is necessary for effective use of high ratio grids during portable examinations?

More precise tube-to-image receptor alignment.

What factors contribute to grid efficiency?

Grid ratio and construction material.

How are modern grids designed to address scatter?

By increasing lead lines per inch and optimizing interspace material.

What are the standard designs for focusing grids based on distance?

Commonly 36" - 42" and 66" - 74" focal ranges.

How does the size of the field relate to scatter in patients?

More extensive fields cause greater scatter production.

What impact do grid artifacts have on image quality?

They introduce noise and reduce clarity.

What careful measurements are required for assessing a grid's performance?

Ion chamber measurements are necessary for evaluating bucky factor and selectivity.

What is the general control over patient conditions during exposure?

Very little to no control over the state of the patient and potential pathology.

What tool is used to measure patient part thickness?

A caliper.

What is the 4 cm rule?

If part thickness increases by 4 cm, you should double your exposure.

What percentage of patients falls into average categories across most exams?

85%-90%.

When kVp is established, what should generally be changed between views?

Only the mAs should be changed.

What does the 15% rule state?

A 15% increase or decrease in kVp will double or halve the exposure.

What is the minimum change required to significantly increase exposure to the IR?

A minimum change of about 35% in exposure or 5% in kVp.

How much should kVp be increased for a radiographic technique of 40 mAs at 100 kVp?

Increased to approximately 105 kVp.

What body habitus types are humans classified into?

Sthenic, hyposthenic, asthenic, hypersthenic.

How is a sthenic body habitus defined?

Average, strong, and healthy in general.

What characterizes an asthenic body habitus?

Very thin due to ill health, may accompany advanced age or disease.

What measurement generally indicates a hypersthenic body habitus?

Excess fat with a barrel-like torso.

In what cases should radiographic exposure technique be increased beyond normal parameters?

When patients are very large and muscular.