Types of Film

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In addition to screen-film, direct-exposure film, sometimes called nonscreen film and special application film (such as that used in mammography, video recording, duplication, subtraction, cineradiography, and dental radiology), is available. Each has particular characteristics that become more familiar to the radiologic technologist with use.


Screen-Film

As was previously stated, screen-film is the most widely used IR in radiology. Several characteristics must be considered when one is selecting screen-film: contrast, speed, spectral matching, anticrossover/antihalation dyes, and requirement for a safelight.

Table 11-1 Types of Film Used in Medical Imaging

Type
Emulsions
Characteristics
Applications
Intensifying screen
Two
Blue or green sensitive
General radiography
Laser printing
Single with antihalation backing
Matches laser used (about 630 nm)
Laser printers attached to CT, MRI, ultrasound, etc.
Copy or duplicating
Single with antihalation backing
Pre-exposed to Dmax
Duplicating radiographs
Dental
Two packed in sealed envelope
Has lead foil to reduce back scatter
Dentistry
Radiation monitoring
Two packed in sealed envelope
One emulsion can be sloughed off to increase OD scale
Radiation monitoring
Dry transfer
One
Thermally sensitive
“Dry” printers



Non- Screen Film

Non screen film also known as direct exposure film is film that does not require the application of intensifying screen. This is most commonly used in mammography.






















Radiographic Film

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Construction of the Radiographic Film
1.) Base
-          Supports the emulsion 150-300 mm thick, semi rigid lucent and made of polyester, the foundation of the Radiographic Film. Its primary purpose is to provide a rigid structure unto which the emulsion can be coated. It is flexible and fracture-resistant. It maintains the film shape and size during use and processing to limit extortion. It is flexible. It provides region structure.
Ø  Dye
-          Is added to tint the film blue to reduce eye strain.

Ø  Dimensional Stability
-          is the property of the base to maintain its size and shape.
Four Types of Base
1.) Glass Plate – the original film base
2.) Cellulose Nitrate – becomes a substitute of the glass plate and highly flammable.
3.) Cellulose Triacetate – not flammable and safety base
4.) Polyester – more resistant to warping from age and stronger and thinner than cellulose triacetate.
Ø  Emulsion – the heart and the most important part of the x-ray film. This is where the x-rays and light photons from IS interacting and transfer information. Consist of homogenous mixture of gelatin and silver halide crystals and coated evenly in 3-5 mm thick.
Ø  Gelatin – provides mechanical support for the silver halide crystals.
Ø  Silver Halide Crystals – the active ingredient of the emulsion. 98% of the crystal is Ag halide crystal and 2% is Ag iodide.
Atomic Number of the following:
Bromine = 35, Silver = 47, Iodine = 53, Gelatin and Base = 7
Ø  Contaminant – is the imperfection of the arrangement of crystals
3.) Adhesive Layer – a thin coating of material between the emulsion and base, it ensures the uniform adhesion between them. It allows the emulsion and base to maintain proper contact during use and processing.
4.) Overcoat Layer – the protective covering of the gelatin. It protects the emulsion from scratches, pressure, and contamination during handling, processing and storage. It also allows a rough manipulation of film before exposure.

Body Cavities

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1. Pelvic Cavity – contains the rectum, urinary bladder and parts of the urinary system.
2. Abdominal Cavity - contains the peritoneum, liver, gallbladder, pancreas, spleen, stomach, intestines, kidneys, and major blood vessels.
3. Thoracic cavity - includes the pleural membrane, lungs, trachea, esophagus, pericardium, heart and great vessels.
a. abdominal cavity and thoracic cavity – are major cavities.

Vertebrae and Its Localization Point

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“Vertebrae”                  “Localization Point”

Cervical Region 
    C1                            Mastoid Process
   C5                             Thyroid Cartilage
   C7                             Vertebral Prominens
Thoracic Region 
   T2-3                         Suprasternal Notch
   T4-5                         Sternal Angle
   T7-8                         Inferior Angle of Scapula
   T10                          Xiphoid Process
Lumbar Region 
  T12-L3                     Kidneys
  L1                            Transpyloric Plane
  L3                            Inferior Costal Margin
  L4                            Iliac Crest
Sacral and Coccygeal Region
  S1-2                         ASIS
Coccyx                      Symphysis Pubis and greater trochanter

Topographical Landmarks in the Body

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1. Acanthion - midline junction of the upper lip and auricle nose.
2. Auricle or Pinna - ear or outer ear.
3. External Acoustic Meatus - external opening into the ear cannal.
4. Glabella - smooth triangular area, superior to the bridge of the nose and between the eyebrows.
5. Gonion - lower posterior angle seen on each side of the jaw or mandible.
6. Infraorbital Margin or IOM - inferior rim of the orbital base.
7. Inion - prominent bump midline at the back of the head. It is also known as ”external occipital protuberance”.
8. Inner Canthus - junction of the upper and lower eyelids.
9. Mental point - midpoint of the chin. It is in the center of the flat triangular region.
10. Mentum - a flat triangular region.
11. Nasion - slight depression at the bridge of the nose and it marks the junction of the frontal and nasal lobes.
12. Superciliary ridge - a.k.a superciliary arch. It is the ridge of the bone found over each eye and under each eyebrow.
13. Tragus - small flack of cartilage over the EAM.
14. Vertex - most superior portion of the head.

Body Movements

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1. Flexion - degrees of the angle of the joints by bending. It is the opposite of extension.
2. Extension - increase in the angle of the joint or straightening of the joint. It is the opposite of flexion.
3. Inversion - turning the foot inward at the joints.
4. Eversion - turning the foot outward at the angle joints.
5. Dorsiflexion - flexion between lower leg and the foot so the angle between the structures is less than or equal to 90 degrees.
6. Abduction - movement away from the midline.
7. Adduction - movement toward the midline.
8. Pronation - turning unto one’s stomach or turning the hand, so the palm is down.
9. Supination - turning unto one’s back or turning the hand so the palm is facing forward.
10. Rotation - circular movement around a specified axis.
11. Tilt - moving the body part so the sagittal plane is not parallel to the long axis of the rest of the body or body part

Positioning Terminologies

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• Projection - refers to the direction of the central ray which travels through the body.
• View - is used when discussing a radiographic image. “View’ is the exact opposite term of “projection”.
• Position - refers to the specific body position or act of placing the px in the desired position in relation to the film or cassette or even in the table.
• Oblique - px is rotated between lateral and prone or lateral and supine position. It is always at angled at 45 degrees.
• Decubitus - px is in recumbent position and usually implies the used of horizontal plane.
• AP Projection- central ray passes from the anterior to posterior aspect of the body.
• PA Projection- central ray passes from the posterior to the anterior aspect of the body.
• Left lateral projection- CR passes from one side to another. From head, chest and abdomen it is named to the nearest side of the body.
Example: Mediolateral
• PA oblique and projection - a.k.a RAO position.
• Axial Projection- longitudinal central ray angle of 10 degrees more with the long axis of the body or body part.
• Tangential- CR touches the structure at one point skimming it and producing a profile projection. It is opposite of axial.


Directional or Relationship Terminology
1. Anterior or Ventral - front or forward aspect of the body or body part.
2. Posterior or Dorsal - backward part of the body.
3. Medial or Mesial - towards the median plane or middle part of the body. Example: Spine is medial to the kidney.
4. Lateral - refers to the position away to the median plane or middle part of the body. It is the opposite of medial position.
Ex: kidneys are lateral to the spine.
5. Proximal - parts close to the point of origin or attachment.
Ex: elbow is proximal to the wrist.
6. Distal - parts furthest to the point of origin.
Ex: fingers are distal to the wrist.
7. Cephalad - termed as cephalic, cranial or superior.
- Pertaining to or towards the head.
8. Caudal - termed as inferior.
- Away from the head or towards the tail or feet.
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