IMAGE PRODUCTION AND EVALUATION
Class One
SELECTION OF TECHNICAL FACTORS
Ups and down chart

Technique Charts

Caliper Measurement
•	Measure the patient and determine technique by size
Fixed Versus Variable kVp
•	Fixed kV Charts use optimal kV and mAs varies by size

•	Advantages of Fixed 
•	Contrast consistent 
•	Decreased patient dose due to using the highest possible kV
•	Extend tube life by using low mA
•	Disadvantages of fixed
•	Increased scatter from high kV
•	Decreased contrast

•	Variable kV uses a fixed mAs and kV varies by size
•	Advantages of Variable
•	Produces higher contrast
•	Disadvantages of variable
•	Contrast changes with changing kV

APR
•	Pre set techniques
•	Usually pictures of anatomy
•	Pick SML and the computer sets technique
•	Can be overridden by technologist 
Special Considerations

•	Casts
•	Fiberglass casts require no technical changes
•	Plaster casts require an increase in technique
•	2 times the mAs or an increase in kV by 15% from the usual technique. Wet casts will require more 	

•	Anatomic And Pathologic Factors	

•	Rule of thumb 
•	Additive diseases increase kV 5-15%

•	 Destructive Diseases decrease mAs 25-50% 

Examples of Additive Conditions

•	Abscess- an encapsulated infection increases tissue thickness and may alter composition
•	Edema- swelling causes an increase in tissue thickness and may alter composition
•	Tumors- an abnormal new growth in tissue results in an increase in tissue thickness and may alter composition
•	Cardiomegaly- an enlargement of the heart causes an increase in the thickness of the part
•	Pneumonia – inflammation of the lung tissues causes fluid to fill in the alveolar spaces. Fluid has much greater tissue density than air normally present.

Examples of Destructive Conditions
•	Anorexia- a psychological eating disorder which results in an extreme weight loss. Overall body thickness is reduced. 
•	Atrophy- a wasting away of body tissue with diminished cell proliferation, resulting in reduced thickness of a specific part or the entire body.
•	Emphysema- over distention of the lung tissue by air will result in a decrease in lung tissue density.
•	Pneumothorax- free air in the pleural cavity displaces normal lung tissue and results in decreased density within the thoracic cavity

•	Pediatrics	
•	Shorter exposure time
•	Fast screen speed
•	Low mAs 

•	Contrast Media	
•	Generally Increase kV
•	Barium – use high kV; 90 or above
•	Iodinated solutions- use 70-80 kV
•	Negative contrast (air) - no change
Automatic Exposure Control
 
•	Effects Of Changing Exposure Factors On Radiographic Quality	 (up and down chart)
•	kV and mAs will seesaw one goes up the other goes down to maintain image quality
•	Will not work for small anatomy (nasal bones) or metal
•	Detector Selection	
•	Place cell over area of interest
•	Chest = two outer
•	T spine = center
•	Anatomic Alignment	
•	Positioning is the key to correctly using AEC
•	Density Control (+1 Or -1) 
•	+1 or more for Bertha and -1 for frail elderly patient
•	Center cell is in the middle with the R & L are slightly higher
•	Back up timer will cut exposure if too long. It is set ~ 150% of manual exposure.

Image Receptors
	
•	Film Screen and Grid Selection	
•	Slower speed screens for detail, faster for low dose
•	Grids are used when the part is more than 10 cm or technique is higher than 70 kV. Lower ratio grids are used with lower kV ranges and higher ratio grids are used with higher kV ranges
•	Film Characteristics	
•	1. Film contrast	
•	Contrast increases with the use of a grid or as speed increases
•	2. Film and exposure latitude	
•	Higher ratio grids and faster screens have less latitude

Image Receptors 
•	Film-screen Combination	
•	Phosphor type	
•	Rare earth used today are Gadolinium, lanthanum and yttrium. Remember G.L.Y. (or GLOW) These are in the blue-green family
•	Relative screen speed
•	100 par screen- all other speeds are based off par screen
•	Single versus double film/screen system	 
•	Single is for more detail used in mammography and extremity
Digital radiography

•	Computed radiography	Image is made on an IR, scanned and made digital
•	Direct digital radiography Image is sent directly to digital
•	Exposure indication S number range; computer can’t add information (technique) but can take away	

H&D curves
Numbers to remember!!!!!!
•	Diagnostic density Range  .25  -  3.0
•	Base                                   .05  - .10
•	Base plus fog should not exceed  .22
•	Speed point                         1.0
•	Aver gradient                       .25  -  2.50
How to read curves…….
•	Slope tells us about the contrast
•	The steeper the slope the higher the contrast (short scale, B&W)
•	The lower the slope the lower the contrast (longer scale, more grays)
•	A has higher contrast
How to read curves…….
•	Speed point (1.0) measures the speed
•	Film closer to the left or y axis is faster
•	Film A reaches 1.0 with less exposure than film B
•	More detail would result from a slower film
•	Faster film would be better for pediatrics (faster and decreased dose)
How to read curves…….
•	The Average Gradient tell us the films latitude
•	Latitude=range of acceptable exposures 
•	Look at the exposure from .25 OD and the exposure from 2.50OD 
•	Film B has a wider latitude
Grid Terms
•	Cut off = absorbing primary radiation: creates undesirable image
•	Clean up= absorbing scatter radiation: helps to increase image contrast
Grid Construction
.
Grid Patterns
•	Crossed

Focused (a type of linear)
GRID ERRORS
OFF LEVEL
•	Occurs when the tube is angled across the long axis of the grid lines or the film is tilted.

Radiographic Film
•	Film Construction
•	Base 
•	Adhesive
•	Emulsion with Crystals
•	Supercoat

•	Screens are used to amplify the beam and reduce patient dose
•	The screens produce light when struck by        x-rays
•	99% of the image is produced by light
•	Duplitized film has 2 screens, one for each side of the film. Single sided film will use a single screen.
Screen Parts

 Minimal phosphorescence and maximum fluorescence 
Film Screen Contact
•	Contact is important
•	Film is sandwiched between two screens
•	Poor film screen contact will decrease detail and increase density
Poor Film Screen Contact

Inverse Square Law
		I1       (D2)2
          I2        (D1)2

Use for questions asking for mR or intensity

Direct Square Law
		mAs1       (D1)2
         mAs2         (D2)2

Use for questions asking for mAs, time or mA with distance changes

Magnification
 SID          or          Image
SOD			  Object

Percent of magnification
Image- Object    x 100
       Object
Field Size Calculation
D1 = F1
D2   F2
D1= Distance from focal spot to     opening of restricting device
D2= SID
F1= Opening of restricting device
F2= field size
****Tip 1 can NEVER be bigger than 2’s*****
(see next slide for picture)

Multipliers for changes in collimation field sizes
•	14x17=1
•	10x12=1.25
•	8x10= 1.40
Field size going to
Field size coming from   X  mAs
Grid conversion 
Screen Conversions
3-2-1 BLAST OFF!
Multiple Conversion Problems
Which has the greatest density?
Checklist method