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Beam Limiting Device (BLD)

It's purpose is to limit the size of the beam and area of exposure to patient, thereby reducing the harmful effects of scatter and to improve image contrast.

1.) Aperture Diaphragm
2.) Cones and Cylinders
3.) Variable Aperature Collimator

What are the types of beam limiting devices?

Aperture Diaphragm

___is the simplest type of all BLD's.

Head Units

Aperture diaphragm is commonly used at dedicated ___.

Fixed Opening

Disadvantage of aperture diaphragm is its ___?

Lead or a Lead Lined Plate

In the aperture diaphragm there is ___ placed directly below the window of the x-ray tube.

Opening

The ___ of the aperture diaphragm is designed to just cover less than the size of the image receptor used.

Unexposed Border

An ___ of the aperture diaphragm should be visible on each edge of the radiograph.

Cones and Cylinders

___ are modifications of the diaphragm.

Circular

Usually the useful beam is in a ___ shape.

Dental

Cones and cylinders are widely used in ____ radiography.

Align

Cones and cylinders are difficult to ___.

Image Receptor

Cones and cylinders must be aligned with the ___.

Variable Aperture Collimator

___ is the most common BLD.

Efficient

Variable Aperture Collimator is the most ___ BLD.

2

NCRP guideline: Variable Aperture Collimator must be accurate to within ___% of the source-to-image distance.

Positive Beam Limiting (PBL) Device

Most variable aperture collimator are automatically adjusted when a film is inserted in a bucky, called a ___.

Lead Filters

Positive Beam Limiting (PBL) Device are equipped with usually two or more ___ stacked one above the other.

Mirror and a Light Bulb

Positive Beam Limiting (PBL) Device uses a ___ as a guide for projection of the field know as a light localization apparatus.

Inherent Filtration

The filtration afforded by the glass envelope, insulating oil and glass window.

0.5 mm aluminum

Inherent filtration is usually ___ equivalent.

Increases

With age, filtration ___.

Quality

As filtration increases, so does beam ___, but quantity is decreased.

Added Filtration

Sheets of aluminum placed between the protective tube housing and external housing.

Added

___ Filtration attenuates more low energy than high energy x-rays.

1.) High energy
2.) Greater penetrability
3.) Higher quality beam

Added filtration results in?

Quantity (lower)

Added filtration affects x-ray ___.

Total Filtration

Equals inherent filtration plus added filtration.

Optimum kVp

___ equates to decreased skin dose.

Photoelectric Interaction

___ is decreased with the tissue.

Exposure

Shorter ___ time results in decreased patient dose and reduces the chance of motion.

10

Grid is generally used on body parts greater than ___ cm. in thickness.

Patient Dose

Use of grid increases ___.

Ratio

Higher grid ___ results in higher patient dose.

Medium or High

___ speed Film/Screen: 8-10 cm. body part thickness.

10

Grid: Greater than ___cm. body part thickness

1.) Proper technique
2.) Proper positioning
3.) Appropriate marker
4.) Correct patient identification

Methods used to avoid repeated radiographs?

Fast

Use ___ film/screen combination.

1.) Digestive organ motion
2.) Cardiac motion
3.) Muscle Spasms

Shorter exposure time is used for involuntary motion such as?

Quality Control Program

Proper processor maintenance, Proper equipment testing and maintenance.

Safe Period

Radiographic examinations should be performed only during the first 10 days following the onset of the menstrual period.

Added Plus Inherent Filtration

How do you calculate total filtration?

Slow

What film/screen combination must be used for parts lesser than 8 cm?

To reduce the radiation exposure to the reproductive organs.

What is the purpose of patient shielding?

An effective means of reducing the risks of genetic defects for the whole population.

What is the importance of patient shielding?

1.) Flat contact
2.) Shadow shield
3.) Shaped contact shield

What are the types of shielding devices?

Flat Contact

Flat piece of plastic covered lead, Similar to lead apron.

Shadow Shield

___ is attached to the x-ray tube.

Suspended

Shadow shield is ___ over the area being radiated.

Light Field

Align the shadow shield with the ___ for accurate placement to avoid areas of interest.

Shaped Contact Shield

____ consist of a radiopaque material contoured to enclose the testicles.

Cleaned and Reused

Shaped contact shield can be ___.

Athletic Supporters or Jockey

Shaped contact shield is available in ___ style.

Reproductive

Patient shielding should be considered for all patients, especially children and those who are potentially ___.

5

Gonadal shielding should be used when the gonads lie in or within ___cm of a well-collimated field or the useful beam.

Positioning and Beam Collimation

Proper patient ____ should not be relaxed when gonad shields are in use.

Interfere

Patient shielding should only be used when it does not ___ with obtaining the required diagnostic information.

AP or PA

Flat contact: ___ views.

Sterile Field

Shadow shield: ___ or incapacitated patient.

1.) AP or PA,
2.) Lateral
3.) Oblique

Shaped contact shield: ___ views, Selected fluoroscopic exam.

1.) Pelvis
2.) Hip (Except oblique)
3.) Upper femur
4.) CXR
5.) Extremity

Shield males in what exams?

1.) Retrograde urethrograms
2.) Voiding cystourethrograms
3.) Oblique views of the hip
4.) Visualization of the rectum
5.) Symphysis pubis

Shielding will interfere with what exams?

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