RT 210 MOTTLE, GRAININESS, AND EFFECTS OF FOCAL SPOT

RT210 FLASHCARDS BY YJV

Noise

an unwanted image that adds a negative impact on the radiographic image quality

1. Accidental exposure to scattered radiation

2. Poor condition in film storage

3. Improper circuits design

4. In convention radiographic image, it may be due to unprofessional development

5. Due to imbalance in chemical property

Noise appears due to:

1. Film graininess

2. Structure mottle

3. Quantum mottle

4. Scattered radiation

Components of Noise:

Structure Mottle

Similar to film graininess

phosphor of intensifying screen

Structure mottle refers to the ____________

inherent

Both film graininess and structure mottle are _______ to screen film radiography

very little

Both film graininess and structure mottle contribute _______ in radiography noise

beyond the control

Structure mottle is _______ of the radiologic technologist because the phosphor of the image receptor was actually made by the manufacturer

somewhat under the control

Quantum Mottle is _________ of radiologic technologist and principle contributor to radiographic noise

Quantum Mottle

refers to the random nature by which x-ray interact with the image receptor

quantum mottle will be higher

If the image is produced with a few x-ray, then quantum mottle will be _______ than the image produced with large number of x-rays

very fast intensifying screen

The use of ________ normally increases quantum mottle

Decrease radiation dose

Decrease patient dose

Increase Noise

Decrease spatial resolution

Decrease contrast resolution

FAST IR:

Increase radiation dose

Increase patient dose

Decrease Noise

Increase spatial resolution

Increase contrast resolution

SLOW IR:

reduce quantum mottle

The use of high mAs, low kVp, and slow image receptor __________

increase patient dose

Disadvantage of using high mAs, low kVp, and slow image receptor:

limits the amount of information

Example: fogging on the radiographic image

The presence of noise _________ which can be extracted from the image. Especially the finer details of structure may be lost by being swamped by the effect of noise.

Example: ________

Film graininess

Refers to the distribution in size and space of silver halide crystal in emulsion

Not controlled by the radiologist

Granularity

measurement of the phenomenon

Graininess

visual impression

minute density variations

When a developed x-ray film is viewed in detail on an illuminated screen, ________ are visible in a grainy sort of structure.

blurred, unsharp edges of anatomic details

Photons emerging from various points on a measurable focal spot are responsible for producing ____________.

directly related

The extend or size of the unsharp area is _______ to the focal spot size and OID, and inversely related to the SID; that is unsharpness increases as focal spot size and OID increase and as the SID decreases.

inversely related

The extend or size of the unsharp area is directly related to the focal spot size and OID, and _______ to the SID; that is unsharpness increases as focal spot size and OID increase and as the SID decreases.

unsharpness increases

The extend or size of the unsharp area is directly related to the focal spot size and OID, and inversely related to the SID; that is ________ as focal spot size and OID increase and as the SID decreases.

focal spot blur, geometric unsharpness or edge gradient

The border of unsharpness around image details is often referred to as

better the geometrically recorded detail

The smaller the focal spot size, the _________. As distinction is made between the actual focal spot and the effective (projected or apparent) focal spot.

sharply defined borders

X-ray photons emitted from a point source will provide an image having ___________

blur or unsharpness

X-ray photons emitted from a measurable focal spot will produce a zone o ___________ around each image detail.

directly related

The degree of blur is ________ to the size of the focal spot.

smaller, better, lesser

The ______ the focal spot size, the ______ the image resolution, and the ______ the focal spot blur

Actual focal spot

Cathode to anode (area on anode where electrons strike)

thermionic emission

in actual focal spot, This is where the phenomenon called the _______ will come to action.

many electrons

It means that if the actual focal spot size is big, it can accommodate _________.

Effective focal spot

Anode to outside tube

spatial resolution

In Effective focal spot, it determines ______

increased, increased

However, for stationary x-ray tubes, if the actual focal spot size is ______, the effective focal spot is also _______.

better the image resolution

The smaller the effective focal spot, the _________.

sacrificed

In this case, to accommodate more electrons/x-rays, the effective focal spot is

Using the line-focus principle

The goal is to have a large actual focal spot to accommodate the electrons but a small effective focal spot must be maintained. How is this achieved?

angulation

For the rotating x-ray tube, since there is an anode disc and anode stem, this is where _______ comes in (line-focus principle).

providing better image quality

line principle was made so that if the actual focal spot is increased, the effective focal spot is smaller, therefore, ___________

low exposure factors

That is why stationary tube can only accommodate ________ that is because the actual focal spot size has a limit.

more heat

For rotating x-ray tube, _______ is accommodated because regardless if the actual focal spot is increased, the effective focal spot will still remain small.

Because the x-rays will be concentrated on one area and will have the collective effort of creating the image.

With bigger effective focal spots, the distribution of x-rays will be larger as well making the x-rays go elsewhere and not just in one area.

Why is smaller effective focal spot better for resolution?

larger effective focal spot

➢ Wider angulation →

smaller effective focal spot

➢ Narrow angulation →

TRUE

TRUE OR FALSE: The addition of the angulation of the anode, made it possible for the actual focal spot to accommodate more energy while maintaining a small effective focal spot which would result to a better image quality.

anode heel effect

Although rotating x-ray tube can accommodate enormous amounts of heat, one down fall is ________ due to the presence of the anode disc.

decrease in x-ray beam intensity

As x-ray photons are produced at the anode focus, a portion of the divergent beam nearest the anode end is absorbed by the anode’s heel. This represents a _________ at the anode side of the x-ray beam.

the more pronounced the heel effect.

The smaller/steeper the anode angle/bevel, the ____________

much lesser

The x-rays that hit the beveled angulation of the anode, loses some of its energy as attenuation happens. So, the energy of the x-rays on the positive side of the x-ray tube (anode) is _________ than the energy on the negative side of the x-ray tube (cathode).

must know

Radiographers ______ the negative and positive side of the x-ray tube to properly position the patient.

cathode side, anode side

The thicker side of the patient’s anatomy of interest must be placed on the ________ and the thinner part on the ________

→ increased blur → decreased detail

Focal spot size affects detail by influencing the degree of blur or sharpness: increased focal spot size

directly related, inversely related

Unsharpness or blur is _______ to focal spot size and OID, and _______ to SID

Increase unsharpness

Decrease unsharpness

Focal Spot Size:

▪ INCREASE focal spot size → ________

▪ DECREASE focal spot size → ________

INCREASE unsharpness

DECREASE unsharpness

OID and Blur/Unsharpness:

▪ INCREASE OID →

▪ DECREASE OID →

DECREASE unsharpness

INCREASE unsharpness

SID and Blur/Unsharpness:

▪ INCREASE SID → DECREASE unsharpness

▪ DECREASE SID → INCREASE unsharpness

small focal spot

The use of __________ improves recorded detail, but generates more heat at the anode

line focus principle

The effective or projected focal spot size is always smaller than the actual focal spot according to the ________

largest, smallest

Effective focal spot size varies along the longitudinal axis of the image receptor, being ______ at the cathode end and _____ at the anode end of the x-ray beam

TRUE

TRUE OR FALSE:

Smaller anode angles can permit larger actual focal spot sizes while maintaining small effective focal spot sizes – at the expense of accentuating the anode heel effect

INCREASE, DECREASE, INCREASE

SMALLER anode angle → _____ actual focal spot → _____ effective focal spot → _____ anode heel effect

DECREASE, INCREASE, DECREASE, DECREASE

LARGER anode angle → _____ actual focal spot → _____ effective focal spot → _____ sharpness → _____ anode heel effect

small anode angle

Use of a _______ can limit image receptor coverage at traditional and short SIDs