Poi (Lec) - Full finals reviewer

- Mostly classified by speed
- Inversely proportional to the image resolution

Film screen combination

The size of penumbra is greater than the effective focal spot size

Near the source

The size of penumbra is less than the effective focal spot size

Away from the source

The most important factor for determining spatial resolution

Detail

No variation of intensity in what portion of the x-ray beam

Central ray

Resolving Power: Radiographic film

100 lp /mm

Resolving Power: Very fast screen:

7 lp /mm

Resolving Power: Fine detail screen:

15 lp /mm

Resolving Power: Non screen/Direct exposure film:

50 lp /mm

Resolving Power: Unaided eye

10 lp /mm

Screen speed: Very fast

1200

Screen speed: Ultra high or hi plus

300

Screen speed: High or fast

200

Screen speed: Medium, par or standard

100

Screen speed: Detail, slow, or high resolution

50

Screen speed: Ultra detail

25

Relationship of film-screen combination to the imager resolution

Inversely proportional

- For examination that requires higher resolution
- For extremity examination
- Higher patient dose

Slower intensifying screen

- Use to reduce patient dose
- For examination that do not require higher resolution

Faster intensifying screen

It keep them in direct contact with one another

Pressure pad

Resolving Power: depends on

Phosphor size, phosphor thickness, phosphor concentration

- Under the direct control of the patient
- Patient communication

Voluntary motion

- Not under the direct control of the patient
- Decrease exposure time

Involuntary motion

- Difficult to detect
- May cause vibration of the cassette in the Bucky tray

Equipment motion

- Affects recorded detail
- Blurring of an image that results from results in loss of radiographic quality
- Results in repeated radiographs

Motion blur

Resolution

General

Spatial resolution (Ability to demonstrate 2 small objects with high contrast)

Sharpness

Contrast resolution (Resolution of greyshades)

Differentiation

Temporal resolution (How fast the data is acquired during acquisition)

Time

- To increase visualization/diagnosis
- Decrease eyestrain

Blue dye

Screen film has \____

Pure light

Direct exposure has \____

Pure radiation

Classification of distortion

Size and shape

- Misrepresentation of size and shape of the structures being examined
- Exists even if contrast and density are poor

Distortion

Magnification is controlled by

Maximize SID, Minimize OID

Used to check for screen film contact

Wire-mesh test

- Generally a matter of magnification
- The images on the radiograph are larger than the object they represent
- Inversely proportional to SID

Size distortion

Relationship of magnification to OID

Directly proportional

- Caused by excessive OID and insufficient SID
- Causes anatomic structure to appear larger on the

Magnification

- Causes anatomic structure to appear longer than in reality
- Caused by improper tube, part, or image receptor angulation or alignment
- Caused by angulation along the long axis of the part

Elongation

- Causes anatomic structure to appear shorter than in reality
- Caused by improper tube, part, or image receptor angulation -Caused by angulation against the main axis of the part

Foreshortening

It include 2 projections 90 o from one another

Radiation examination

Misrepresentation by unequal magnification of the actual shape of the structure being examined

Shape distortion

Refers to the direction and degree the tube is moved from its normal position perpendicular to the image receptor\____ of the tube is designed to cause a controlled or expected amount of shape distortion to avoid superimposition

Angulation

Source to skin distance is also called

Pluro

The best radiation protection is \____

Distance

What is the degree of standard angulation (Perpendicular)

0 degrees

How many inches and cm is Air gap

118, 300

The degree of axial

10 degree or higher

- Angulation of the Elongation
- The most common direction of tube angle is

Longitudinal

Angulation of the Foreshortening

Transverse

- Major controller of image resolution
- Primary factor in controlling spatial resolution
- Does not affect x ray quantity or quality
- Controlled by the line focus principle

Focal spot size

- Tube that has a very small focal spot
- Used in mammography

Microfocus tube

- The distinctly sharp area or area of complete shadow
- Receives essentially no photons

Umbra

- The imperfect, unsharp shadow surrounding the umbra
- Receives more photons
- Important factor for determining spatial resolution

Penumbra

- Angling the target
- A design wherein the x-ray tube is angled to allow large area for heating while a small focal spot is maintained

Line focus principle

A large focal spot provides a shorter \____

Exposure time

- Used for general imaging Used to image thick or dense body parts
- Provides for a shorter exposure time
- Minimizes motion blur
- More capacity to produced x rays
- Higher anode heat capacity

Large focal spot size

- This focal spot is used to improve the image resolution
- Used for fine detail imaging
- Used to image thin or less dense body parts
- Used for extremity radiograph
- Less capacity to produce x rays
- Always used for magnification radiography
- Lower anode heat capacity

Small focal spot size

Uses magnification to easily visualized structures that are too small

Magnification radiography

Shape distortion can be avoided by careful alignment of the CR with the anatomical part and IR

Alignment

Simply a method of describing the exact amount of angulation and is usually stated as the angle between the central ray and the image receptor plane from the standard reference point of perpendicularity

Degree

This type of cathode is designed to provide two focal spot

Focusing cap

- It is where the focusing cup is located
- Negative side
- Where thicker and larger body parts are examined

Cathode

- Positive side
- Where thinner or smaller body parts are examined

Anode

Towards the anode side (%)

25% above

Towards the cathode side (%)

20% below

The minimum target angle to cover the largest film size possible at short SID (40 degrees)

12 degree

Unit of heat in radiology

Heat unit

It is the standard reference point in perpendicular

90 degree

Involuntary motion is caused by the following:

Heart pulsation, Chill, Peristalsis, Spasm, Tremors, Pain

Voluntary motion resulting from lack of control is caused by the following:

Nervousness, Discomfort, Excitability, Mental illness, Fear, Age, Breathing

Formula of magnification

M \= SID/SOD

Formula of Object

O \= I/M

Formula of Focal spot blur

EFS x OID/SOD

- This is the consequence of angling the x-ray tube target
- The absorption of x-ray in the heel of the target

Anode heel effect

Usually termed cephalad when the tube is angled toward the head of the patient, and caudad when it is angled toward the patient’s feet

Longitudinal angulation

- Designed to provide a constant OD regardless of tissue thickness, composition or failure of the reciprocity law
- Positioned after the IR

Automatic exposure control

Designed to provide a constant \____ regardless of tissue thickness, composition or failure of the reciprocity law

OD

AEC is used to minimize \____

OID

- Tables that provide a means of determining the specific technical factors to be used in a given radiographic examination
- Provides RT with a guide to the selection of exposure factors for all patients and all examinations
- Allows for consistently good diagnostic images

Radiographic technique charts

Radiographic technique charts describes standard methods for consistently producing a \____

high quality image

Total filtration in Collimator Housing

3.0 mm Al

Total filtration for standard

2.5 mm Al

This is checked for accurate light field and x ray beam coincidence

Collimators

\____ Kilovoltage Radiographic Technique Chart\____ Kilovoltage Radiographic Technique Chart\____ kilovoltage Radiographic Technique Chart\____ Exposure Radiographic Technique Chart

Variable, fixed, high, automatic

Uses a fixed \____ value and a \____ that varies according to the thickness of the anatomical part

mAs, kVp

- Uses a fixed mAs value and a kVp that varies according to the thickness of the anatomical part
- Advantage provides radiographs with an inherently short scale of contrast

Variable Kilovoltage Radiographic Technique Chart

Additive factor: Single phase

30

Additive factor: Three-phase

25

Additive factor: High-frequency generator

23

The kVp varies with the thickness of the anatomical part by

2 kVp/cm

- Most often used
- Developed by Arthur FuchsUses a fixed kVp value and a mAs that varies according to the thickness of the anatomical part
- A method of selecting exposures that produce radiographs with a longer scale of contrast

Fixed Kilovoltage Radiographic Technique Chart

Optimum kVp for spine and trunk

80 kVp

Optimum kVp for soft tissue of the abdomen

70 kVp

Optimum kVp for most extremities

60 kVp

Reduced mAs by 30%

Small part

Increase mAs by 30%

Large part

Increase mAs by 50%

Swollen part

- Usually use kVp greater than 100Ideal for barium work
- Used for routine chest radiography

High Kilovoltage Radiographic Technique Chart