Radiography Image Intensification Factors

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of a photostimulable storage phosphor imaging plate in computed radiography?

To convert light into an electronic signal

To directly convert x-ray photons to numerical values

To convert incoming x-ray photons to light

To store images temporarily (correct)

Which component is commonly found in direct conversion detectors?

Photomultiplier tube

Photodetector

Amorphous selenium (correct)

Scintillator

What is the key difference between computed radiography and digital radiography?

Computed radiography uses film-based images while digital radiography does not.

Digital radiography utilizes a reusable detector instead of a cassette. (correct)

Computed radiography requires manual processing of images.

Digital radiography is solely based on traditional film/screen systems.

In digital image formation, what do the individual matrix boxes represent?

Picture elements or pixels Signup and view all the answers

Which of the following best describes the role of a scintillator in indirect conversion systems?

It transforms incoming x-ray photons into light. Signup and view all the answers

What type of conversion process do indirect conversion detectors use?

A two-part process involving light and signal conversion Signup and view all the answers

What does each pixel location in a digital image matrix have?

An assigned address Signup and view all the answers

How does a digital radiography system typically operate?

Through a binary machine language Signup and view all the answers

What factor is primarily responsible for determining the density of radiographic film?

mAs Signup and view all the answers

What happens to radiographic density as mAs is increased?

Density increases proportionally Signup and view all the answers

What concept explains the relationship between the intensity of light and the duration of exposure in photography?

Reciprocity law Signup and view all the answers

At what kVp range is a change of 8-9 percent required to maintain consistent exposure?

50–90 kVp Signup and view all the answers

When exposure to a film is increased, what is the result until Dmax is reached?

Density increases Signup and view all the answers

Why is mAs used as the primary controller of radiographic film density?

It maintains constant intensity and duration of x-ray exposure Signup and view all the answers

What percentage change in kVp is required in the higher ranges of 90-130 kVp?

10–12 percent Signup and view all the answers

How did Bunsen and Roscoe contribute to the understanding of photographic film exposure?

They stated that film reaction to light is proportional to intensity and duration Signup and view all the answers

What does a 'bit' represent in the binary system?

An on or off value Signup and view all the answers

How is the total number of pixels in a matrix calculated?

Multiplying the number of boxes in the row by the number of boxes in the column Signup and view all the answers

What does the term 'field of view' (FOV) refer to in digital imaging?

The overall dimension of the image matrix Signup and view all the answers

What technology does Computed Radiography (CR) use for image capture?

Phosphor imaging plates Signup and view all the answers

Which factor influences the brightness and contrast of a digital image in radiography?

The shades of gray represented by pixels Signup and view all the answers

How did the introduction of Computed Radiography (CR) in the 1980s affect digital imaging?

It initially faced issues with high cost and low image quality Signup and view all the answers

What happens to large focal spots at higher milliamperages?

They tend to bloom more. Signup and view all the answers

What represents a three-dimensional volume of tissue in medical imaging?

Voxel Signup and view all the answers

What is the consequence of focal spot blooming regarding density changes?

It rarely causes visible density differences. Signup and view all the answers

Which aspect of the digital image can be adjusted through windowing?

The contrast and brightness Signup and view all the answers

How does kilovoltage (kVp) affect radiographic density?

It influences both beam intensity and quality. Signup and view all the answers

What is one of the primary effects of the anode heel effect on radiographic density?

It varies exposure by up to 45% across the IR. Signup and view all the answers

In a well-calibrated x-ray unit, what should not occur when changing focal spots?

Variations in density/IR exposure. Signup and view all the answers

When focal spot blooming is perceived as causing density changes, what action may be indicated?

Replacement of the x-ray tube. Signup and view all the answers

Which of the following statements about kVp is true?

It significantly impacts both the quantity and quality of the beam. Signup and view all the answers

What reflects a common misconception regarding focal spot adjustments?

Focal spot changes lead to immediate visible differences. Signup and view all the answers

What effect do grids have on radiographic images?

Grids absorb scatter, reducing film density. Signup and view all the answers

How is size distortion or magnification measured in radiography?

Using the magnification factor calculated through geometry. Signup and view all the answers

What occurs during elongation in radiographic images?

The tube or image receptor is improperly aligned. Signup and view all the answers

Which scenario is associated with foreshortening?

The part is improperly aligned relative to the receptor. Signup and view all the answers

What is a necessary condition for proper positioning in radiography?

The central ray must be perpendicular to both the part and the receptor. Signup and view all the answers

What type of distortion may occur with improper alignment of the anatomical part?

Both size and shape distortion can occur. Signup and view all the answers

Which of the following describes the relationship between the central ray and the anatomical part to avoid distortion?

The central ray should meet the anatomical part at a right angle. Signup and view all the answers

What common misconception might arise regarding the causes of foreshortening?

Foreshortening is caused by changes in tube angle. Signup and view all the answers

What is the primary purpose of alignment adjustments in radiography?

To ensure the tube central ray, part, and image receptor are correctly aligned Signup and view all the answers

What happens if the central ray is not positioned perpendicularly to the anatomical part?

Some degree of shape distortion will occur Signup and view all the answers

How can central ray angulation be advantageous when dealing with anatomical parts?

It helps differentiate structures when parts are superimposed Signup and view all the answers

What is a common result of incorrectly positioning the anatomical part with respect to the central ray?

Distortion of the image Signup and view all the answers

What consequence may arise from off-centering the image receptor?

Clipping of a portion of the area of interest Signup and view all the answers

In radiographic imaging, how should the long axis of the anatomical part be positioned relative to the central ray?

Perpendicular to both the image receptor and the central ray Signup and view all the answers

What does the central ray represent in radiographic imaging?

The exact center of the focal spot Signup and view all the answers

What occurs when the image receptor is misaligned with the anatomical part?

Clipping may result while retaining parallelism Signup and view all the answers

Study Notes

Image Intensification Factors

Age Correction: A table is used to correct exposure factors for children and infants (ages birth to 12 years) compared to adults. Multiply the adult exposure factor by the correction factor to determine the correct exposure for the patient's age. The correction factor varies with age. (Example given of how to calculate child dosage)
Contrast: Contrast is the difference in brightness/density between two tones in an image.
- Low contrast = low differences = more radiographic fog
- High contrast = high differences = better definition/clearer image
- Beam restriction (less scattered radiation) reduces unwanted IR exposure and, thus, increases contrast
OID (Object to Image Receptor Distance): Less scattered radiation and less unwanted IR exposure, this improves contrast
KVP (Kilovoltage Peak): Controls the penetrating power of the beam. Lower KVP values result in less penetrating power and higher contrast.
- 30-50 KVP: ~8-9% change in exposure required to maintain consistent image density
- 50-90 KVP: ~6% change in exposure required to maintain consistent image density
- 90-130 KVP: ~10-12% change in exposure required to maintain consistent image density

Radiographic Density

Density is the overall darkness/blackening of the radiographic image.
It results from the accumulation of metallic silver after exposure to radiation and subsequent processing.
The quantity of radiation absorbed by the film determines the density.
Primary, remnant, and secondary radiation contribute to the overall density.

Technique Conversion Factors

Motion: Motion can be physiological/involuntary or accidental/voluntary
- Physiologic motion can be controlled by high mA and short exposures
mAs (Milliamperage-seconds): Controls the quantity of radiation.
- Doubling or halving mAs will result in a proportional change in density
- Used primarily to control film/image density

Other Factors

Focal Spot: Larger focal spots lead to more blooming (radiation expansion) at higher mA, which can impact density variation, while a smaller focal spot makes accurate focusing of the electron beam possible, especially at high mA.
Anode Heel Effect: Intensity of radiation varies across the image receptor. More intense toward the cathode (negative cathode) side.
Distance (SID and OID): Affects intensity and thus density according to inverse square law. Increased distance = decreased intensity, decreased exposure and density (inverse relationship). Decreased distance = increased intensity and density. Used in calculating adjustments to technical factors.

Distortion

Shape Distortion: Occurs when central ray is not perpendicular to the anatomical part and the image receptor. This results in elongated or foreshortened structures.
Size Distortion: Magnification of an anatomical structure due to the relationship between SID (source to image distance) and SOD (source to object distance) according to the inverse square law.
Alignment: Proper alignment of the part and the image receptor and the tube is critical, and improper alignment (off-centering) can cause distortion.

Image Receptor (IR) Exposure—Digital

Digital Radiography (DR): Uses a reusable detector instead of film for recording. Two types: computed radiography (CR), and direct digital radiography (DDR).
- Computed Radiography (CR): uses a photostimulable phosphor imaging plate (PSP), which is read using a laser and transformed into a digital image
- Direct Digital Radiography (DDR): Uses detectors that directly convert X-ray photons into electrical signals, resulting in a digital image.

Latendt Image

The latent image needs to be read and manipulated by the computer and used in either soft or hard copy form.
The latent image in X-ray CR film/imaging plates is the pattern of trapped electrons in the imaging plate that create a digital radiographic image (similar to a latent image on film which creates a physical image).

Filtration

Filtration reduces beam intensity, which reduces the amount of scatter radiation impacting the IR, improving image quality (and reducing exposure).

Anatomical Parts

Tissue thickness and atomic number affect density. Greater tissue thickness will result in less density.
Contrast media can be either radiolucent (less dense) or radiopaque (more dense).

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers essential factors affecting image intensification in radiography, including age correction for pediatric patients and the roles of contrast, OID, and KVP in image quality. Learn how to apply these concepts to enhance diagnostic imaging. Test your knowledge on how these variables impact radiographic outcomes.