Quality Assurance and Quality Control Tests (PART II)

- safelight testing

- darkroom light leakage testing

light and leakage testing (2):

- cracks or pinholes in the filter

- wrong wattage of the bulb being installed

- doors on a sodium vapor lamp being open too far

safelight may become unsafe over time as a result of (3):

semiannually or more frequently

safelight testing is done at least ___ or ___ if problems are discovered

bulb or filter replacement

safelight should be changed after a

annually

if safelight is turned on 24/7, filters should be changed

every 2 years

if safelight is turned on 12/7, filters should be changed

- penetrometer

- sensitometer

methods of safelight testing (2):

8 x 10

penetrometer: load an ___ in cassette with film from a fresh box

40 in. SID

penetrometer: expose the cassette in the x-ray room at a

70 kVp and 5 mAs

penetrometer: expose at approximately ___ and ___

1

penetrometer: step-wedge image should have an OD about __ on the densitometer

2 minutes

penetrometer: expose the film to normal safelight conditions for __ minutes, then process the film

no safelight fog

no line =

penetrometer: maximum acceptable fog:

> 0.05 optical density

penetrometer: indicates serious safelight fog

penetrometer procedure

acceptable to dual-emulsion films only

2 minutes

sensitometer: expose the film to normal safelight conditions for __ minutes and then process the film

1.4 OD

sensitometer: use a densitometer to determine the step that will have an optical density closest to __

0.05 OD

sensitometer: for dual emulsion films, the maximum density difference should not exceed ___

0.02 OD

sensitometer: for single emulsion films, the maximum density difference between the halves cannot exceed ___

sensitometer procedure

acceptable for both single-emulsion and dual-emulsion films

55-75°F (14-24°C)

films should be stored at a temperature between

30-60%

films should be stored at a humidity between

40-85°F (5-30°C)

chemicals should be stored at a temperature between

70°F (21°C)

temperature storage for chemicals should not exceed ___ for an extended period of time

Thomas Alva Edison

he developed IS in 1896

Michael Pupin

first used Film/Screen combination a year after IS was developed

luminescence

x-rays exiting the patient energize the phosphor crystals which results to emission of light

- fluorescence

- phosphorescence

luminescence can occur by one of two different processes:

fluorescence

light emitted within 10−8 s after crystals are exposed

phosphorescence

light emitted sometime after 10−8 s after crystals are exposed

intensifying screen speed

refers to the amount of light emitted by the screen for a given amount of x-ray exposure

more

a fast screen creates ___ light compared to a slow screen when exposed to identical exposure factors

- intensification factor

- relative name

- speed value

intensifying screen speed can be measured by (3):

intensification factor

exposure required to create a certain OD without a screen divided by exposure required with a screen to create the same OD

IF = exposure without screen / exposure with screen

formula for intensification factor:

relative speed

- most common method of designating screen speed

- used for all screens with rare earth phosphors

- a number that's a multiple of 100 is used

mAs

relative speed: when the speed of the screen is changed, a change in ___ is required

new mAs = old mAs x speed value / new relative speed

formula for new mAs:

older, non-rare earth screens

use specific names such as fast or slow to designate screen speed

300

relative speed of ultrahigh or hi-plus

200

relative speed of high or fast

100

relative speed of medium, par, or standard

50

relative speed of detail, slow, or high resolution

25

relative speed of ultradetail

acceptance, yearly

quality control testing of screen speed should be done on __ and then __

- multiple IS speed uniformity

- single IS speed uniformity

standard QC test to check for speed uniformity is performed in two ways:

multiple IS speed uniformity

testing several IS of the same marked screen speed

single IS speed uniformity

testing a single IS

1.5

speed uniformity: make an exposure of a step wedge or homogenous phantom onto an IR so that the center of the image has an OD of about__

±0.05

speed uniformity: OD readings should not vary by more than a value of __

1.5

screen uniformity: make an exposure of a homogenous phantom onto an IR that yields an OD of approximately __

±0.05

screen uniformity: OD readings should not vary by more than a value of __

intensifying screen phosphors

emit blue, blue-green, or green light

monochromatic (blue sensitive films)

film sensitivity to blue-violet-emitting phosphor

orthochromatic (green sensitive films)

film sensitivity to green-emitting phosphor