Radiographic processing is necessary for the 

production of the useful visible image.

It links exposure to interpretation and 

influences quality.

The function of processing is designed to provide the 

participant with an understanding of the 

relationship of processing and the visible image.

It covers film structure,

latent image formation,

the role of the developer and developer 

oxidation.

To understand how processing functions.

To understand what processing is,

we need to consider it as a system,

how this system works in relationship to 

the production of the useful visible radiographic 

image.

The function of processing works on of 

course the film,

the latent image and convert it into visible 

image.

So we need to consider the other components,

such as a piece of film.

We see that the basic X 

ray film has emotion on both sides,

both sides of the base.

The emotion is coated,

it's very thin and we can 

consider the total structure in in greater 

detail.

We see that we have an emotion layer on both 

sides of a rather thick piece of film base.

The emotion layer is protected by an anti abrasion code 

and it is aided in its adhesion to the base 

by a sub coat The emotional 

layer,

there's a very thin layer 

compared with the rather thick base,

the base being seven mills or seven thousands of an inch 

thick.

And you can see that the film base has a tent.

The film based.

First of all to discuss this is 

polyester,

it's a 

plastic.

The plastic is made up of long polymer 

chains and specifically the way it is 

manufactured is we begin with dimethyl 

terephthalate,

which is often abbreviated to D.

M.

T.

This is mixed with ethylene glycol in 

a certain ratio.

And this produces a plastic dope which is 

pliable and it's very much like a syrup.

This then is coded.

And as the material solidifies it 

forms a very plastic material,

very flat,

very much like glass.

And that's one of the advantages.

It has much much less 

parallax than what was found with the old 

acetate or tri acetate based films.

Polyester is used throughout the radiographic world 

today as a superior base support 

material.

The tent is in the base to help the radiologist 

and in making his interpretations when he looks at the blacks and 

the the areas that are absent 

absent of black.

So we have a polyester film base.

The polyester is some 12% thinner than 

would be the uh the 

equivalent of a tri acetate base.

And this reduces parallax.

Now the emotion layer is composed of two 

things.

The binder and the recording media.

First of all,

we call this an emotional layer.

This is characteristic uh term 

that's applied to photographic recording 

layers that are on the film base.

But actually chemically speaking,

this is a suspension.

We have suspended in the binder,

the recording media.

The binder is made up of gelatin.

The gelatin itself comes from collagen which 

is a basic uh protein that's found in 

all animal tissues.

Specifically.

The best collagen might come from the flat bones,

the scapula and so forth of cattle 

or cows found in parts of 

Asia and in certain parts of the world.

And this is treated with an acid or an alkali 

material and eventually broken down to form 

the gelatin,

which is then used in radiography.

After many washings infiltration,

going back to the slide,

we have the recording media.

The recording media is a silver hey lied 

and the recording media is 

mixed in with the binder and then the binder is coated 

on both sides of the film 

base.

The actual X ray emotion composition insofar 

as a recording media might be this particular 

formula.

We start with a silver nitrate and this is formed by 

simply taking silver bullion and reacting 

with nitric acid to form a silver nitrate.

This is reacted with potassium bromide in this 

case or as you can see,

iodine and this forms a silver 

bromide.

The components silver nitrate is 

a colorless solution.

potassium bromide would be colorless and the to form 

a sort of white precipitate which 

will fall to the bottom of the reaction 

vessel and that leaves potassium nitrate as 

a waste.

This material then would be washed and cleaned 

gelatin is added as you can see the potassium 

nitrate would be washed out.

Now to consider that we have on 

our basic film two layers 

and we have a large piece of film as I mentioned 

before,

between the two layers of two images that we eventually 

will end up with.

This creates a bit of a problem is unique to radiology and that 

we have two images that we're trying to line up with our eyes.

The rays of light are passing from one image in one 

layer,

one emotional layer through the base where it's distorted and 

bounced around and it emits out the other layer,

picking up added information.

We try to superimpose these two images and 

then drive some sort of interpretation.

This has a tendency to increase 

contrast and to a degree reduce sharpness,

but this is necessary to reduce 

patient exposure and to provide the 

radiologist with the maximum amount of information with the 

least permissible dose of radiation.

Now,

if we consider the basic way that we 

work or function within the field of 

radiology,

we might consider these particular steps.

As we see,

the technologists is making a controlled exposure.

He will make the exposure.

In this case it's a tabletop with aluminum step wedge or image 

quality device and he will take 

this uh exposure that he's made and he will 

place it into a pass box,

It disappears into that magic area called the dark 

room where it is placed into a processor 

and then eventually will come out the processor 

converted into the visible image.

The latent image that the technologist has formed with 

his skills and and art are turned 

into the visible image,

which is necessary for the radiologist to 

make his decision upon.

So processing becomes the link between the latent 

image and the visible image between the 

exposure between the formation of the 

information and the production of the 

useful information the visible image.

And then the technologists in this case doing a 

quality control check,

can compare his uh test 

film with a previously exposed 

control strip.

So we have the formation of the latent image 

processing and the interpretation of the visible 

image.

And of course whether it be a sensitive metric 

strips such as this or 

the actual radiograph.

In this case we have a sense symmetric strip with the 

radiograph.

In either case we are talking about the production of a 

useful item in this case the useful 

radiograph.

So this then becomes the sequence of 

events.

We expose the film.

We place it into the processing situation,

specifically the past box,

the dark room,

the processor and then it comes out the other end and 

we have the finished radiograph now to 

understand how this works and how processing really plays an 

important role in the social function.

We have to look more closely at the sequence of 

events and determine exactly what we're 

working with.

Now to begin 

with we have to say all right,

what's our basic reaction.

We know that we have a patient.

We have a film and we have radiation.

Well specifically we can say 

that on this film we have 

a silver bromide crystal.

It's unexposed and we're going 

to expose it with some unit energy 

level.

Usually you talk about X radiation or perhaps the light from 

the screen but we'll look into this and to go along 

this then will form an ionization 

condition.

We still have the silver hey line but now it's 

broken down instead of being 

balanced.

We have ionic form of the silver and 

the borough.

Mean in this case of bromide and this 

forms then what is commonly called the 

latent image.

I should point out that this is an image.

It does exist and we'll see this as we go along and 

it's however hidden it's a non useful image 

and we need to do something to bring out this 

image to make it more useful.

Okay then so we start off with a silver Halide crystals 

and remember some are not exposed,

Some are but we have a silver hey like crystal,

it has been exposed by the remnant radiation.

That radiation which emits from the patient enters the 

cassette or strikes the film.

So we have the radiation striking the 

crystal and causing a latent 

image.

Now let's look more closely at just what we might consider 

insofar as our silver Halide crystals.

Hey Allied's as such are a group 

of chemicals that have similar properties.

We could use any of these hail IEDs in combination with 

silver as you see bromine chlorine chlorine 

and iodine.

There is 1/5 it's man made as a teen and 

that's seldom used chlorine is also seldom used 

but by using certain combinations of bromine 

or chlorine,

we get different effects,

effects of speed or contrast 

or fine 

detail in various films.

For instance,

industrial radiographic films have a tendency to 

use more silver chloride crystals as 

versus the silver bromide,

which is more usually used in medical.

And sometimes we might even have hybrids such as silver 

I.

Oto bromide for instance,

we need to next consider that there are 

different kinds of exposures,

not the usual X radiation 

that we normally think about.

But you can have for instance,

radiation as a class of 

exposure.

We have the 

radiation X ray which is common to us.

Gamma of course.

Uh heat is a form of radiation and 

as so is light.

Now,

light is a curious thing because we know that very little of 

the original primary beam actually causes the 

exposure in the film and that it's the light from the 

intensifying screens which which which actually causes the 

exposure on the film.

So the X ray beam is magnified many 

times by the intensifying screens.

And it's often said that uh less than 

1% of the original X radiation.

The beam is actually causing an 

image all the rest of the image or 99% 

approximately is coming from the light 

from the intensifying screens.

Of course,

light from a door for 

from a light leak around the processor 

or from a lighting fixture in the 

ceiling.

This light uh whether it be sunlight 

or light from fluorescent tubes is 

also light and it is of a sufficient 

energy level that will cause a breakdown in 

the silver hey lied 

recording media and it will record an image.

Unfortunately,

it's not the image that we want.

So therefore it's an unwanted image.

It's an artifact or defect depending on 

which term you prefer.

Okay,

looking again at our sources of 

energy levels,

we can see that pressure such as handling 

bending of the film,

causing the familiar kink mark or pressure 

mark,

uh closing the cassette lid on the film.

Things of this nature create pressure marks again,

causing the formation of this latent image,

static static electricity discharge through 

ungrounded personnel or 

tabletops,

moisture,

chemicals,

strong chemical fumes are very common source.

Uh,

many of the cleaning chemicals and disinfectants can 

cause uh the breakdown 

of the silver Hey light crystal into the latent 

image and again,

this would appear as fog on the film.

It's non useful density.

Age is a unique form of exposure.

It's not the,

the addition of an extraneous or extrinsic 

extrinsic form of energy.

Actually,

what it turns out to be is that the energy necessary to 

hold the silver Hey,

light crystal together in bond eventually 

fails and the crystal will disassociate as if 

it had been bombarded by an external energy 

level and thereby separated.

So as you can see that we have different highlights that we could 

use in the silver Hey light crystal we have different 

energy levels and when we consider an 

exposure,

remember there's many things that can cause this exposure 

and that includes chemicals.

The chemicals are used to create a visible image 

but they they're used incorrectly can cause 

an improper image.

All right.

The next thing to consider is exactly what 

happens when the 

uh crystal is hit by some sort of 

energy.

Now because we normally have indirect exposure such 

as intensifying screens activated by X 

radiation will consider this aspect.

The light photon will strike 

the crystal and an 

electron is released.

Electron will migrate towards the 

sensitivity speck we see right here.

So this electron will migrate to the sensitivity 

speck and there it will 

be trapped.

And this is called entrapment in 

the theory of the formation of latent 

image,

the entrapment phase.

So the electron is trapped there.

Many people are not sure and they've never been able 

to find out exactly what the sensitivity speck really is.

Many people hold that it is a sulfur deposit.

Others that it's an imperfection in the crystal structure.

But we do know that this electron which is released 

is drawn to this 

spot.

The sensitivity speck and there it's 

trapped and the word entrapment or 

trapping is used because the sensitivity 

speck is not known to have an electrical charge.

And normally we know that uh as 

far as electrical charges go that unlike 

uh will attract and 

like charges will repel.

So it's thought that perhaps this might have a positive charge 

but it's never been determined as such.

So we have this electron,

one electron which will migrate to the sensitivity.

Speck.

The granny mod theory of the latent image formation says that we 

don't just end up with a latent image as you can see here.

The bromide is attacked by the same energy 

that we had with the 

the drawing that I put on the 

blackboard.

The energy level causes the release of the 

electron from the bromide ion 

which is in great abundance.

There's much more bromide than there is silver.

So the bromide yields up the electron.

The electron then goes to the sensitivity speck,

it is trapped there.

And now the silver which is 

positive,

is drawn to the negative electron.

It needs its electron to become stabilized.

So it's very willing to migrate to the spot where the 

electron is trapped.

So in effect the electron makes the 

sensitivity speck become a 

negatively charged location to which the 

silver will migrate and then the silver will react 

with the electron.

Its atomic structure will be satisfied 

and it will neutralize itself.

It will be stable metallic silver.

And at this point we see that the silver 

ion plus the electron forms 

a silver atom at the sensitivity speck 

But this is just one spot in this 

uh crystal.

And in this one particular spot in the crystal 

we may have five or 10 atoms of 

silver.

The entire crystal has not been converted to 

piles of silver or atomic structure 

of silver.

But just this one spot And we see 

that at the one spot we have usually 

in an average exposure about 

five or 10 selling more than 10 silver 

atoms would be collected at the sensitivity 

spot or sensitivity 

speck.

And of course you must realize that while we have one 

crystal that has been exposed,

we have several crystals which have still 

to be exposed or in this case 

they may not need to be exposed to be washed away.

And that will just leave the difference of anatomical 

information.

So at this point we have at least one crystal which has 

been exposed.

The other three are unexposed.

Now the mechanism mechanism of development 

is such that we have this exposed 

crystal that we just saw.

Okay.

And this is the way it's normally written as an 

ionic form,

the latent image.

But we know now that the Gurney ma theory says that this latent 

image does not exist exactly this way that the silver 

silver has been 

neutralized in its ionic form to a stable form.

And we have stable metallic silver.

And incidentally the blooming in the 

remote theory the blooming which is stabilized for 

roaming gas which will linger in the emotion 

and can be detected evolving during the 

development stage as it evolves out of the 

gelatin layers.

Okay,

we have the exposed crystal.

This then is placed into a developing 

solution which contains a reducing 

agent.

The developer then will provide an 

electron and that electron will 

stabilize the remaining silver throughout the entire 

crystal and we end up with many atoms 

of metallic silver.

The developer is a reducing agent which means 

it reduces something else.

In this case it reduces the silver to metallic silver.

The developer itself is oxidized and 

therefore we have oxidation products,

developer,

oxidation products and we have some 

bromide byproducts.

The developer then undergoes an oxidation 

reduction reaction insofar 

as how it functions.

It's an oxidation reduction reaction 

products that are oxidized provide 

electrons.

Those things which have been reduced are 

going to consume an electron.

So the silver has been stabilized.

It has been reduced to a stable state as metallic 

silver,

black,

metallic silver the developer has 

been consumed has been burned up or killed.

Whichever phrase you like.

It's been consumed.

It's been oxidized.

It has produced an electron and its state has been 

altered.

So this is the mechanism of developer.

The developer is said to be selective in its normal 

environment.

Under certain conditions of processing the 

developer provided electron will seek 

out the sensitivity speck which is now called a 

development site and it will provide electrons so that 

the rest of the crystal which now if you will has 

let's say been weakened by this pile of 

silver.

About the sensitivity speck.

Well,

this is now an access point where the electrons 

can enter notice in this next crystal to the right 

that the electrons which are just floating throughout the gelatin 

layer is not attacking the crystal.

It's veering away or bouncing off or just going 

right on through.

It does not react.

We have in this case a bromide barrier that has 

not been broken down by exposure.

So therefore the developer is selective in that it will 

attack the exposed crystal and not 

attack the unexposed crystal.

And this results in the entire crystal 

becoming exposed or becoming black.

So we can say that the developer is selective 

and it will attack the crystal which has been 

exposed and will convert it from a few 

five or 10 atoms of silver to the 

entire crystal being converted 

to metallic silver.

So this is a very important aspect of the 

function of the developer.

The function of processing it has an 

amplification aspect.

It is magnifying our original signal.

Original five or 10 atoms within one 

crystal has been multiplied many many times.

To the point where we have now the entire crystal 

has been converted to piles of atomic 

silver,

black,

metallic silver.

So we have it amplifying as 

such.

And we need to then consider well where have we 

gone from?

And to we've gone from a small 

pile of silver which the granny mod theory says is 

stable black,

metallic silver in the latent image.

This we cannot see it's totally of no value to 

us.

It can be measured,

but we can't use it with our unaided eyes.

It's an unseen image,

but the image is really there and that's why it's called the latent 

image.

It is indeed there.

And we've gone from these few unuseful 

piles of silver.

We've amplified the image to all of this,

a factor of over a million times now.

This crystal with many others can then 

form the useful image 

so that then in summation is the 

importance of the developer to amplify at the 

same time.

We can see in this chart that the developer is 

oxidized.

As I mentioned that there are many things to consider 

insofar as developer oxidation.

The usual way that developers oxidized is use 

oxidation.

And that's the first thing to consider.

Now.

Normally we know that the developer is 

oxidized.

It's necessary that the developer be oxidized to produce 

electrons to stabilize the black metallic silver in the 

latent image.

Next,

we need to say,

okay,

this form of oxidation is use 

oxidation.

We know that it's going to happen.

We've taken steps to develop replenishment 

systems or monitoring the amount of film we 

use the square footage square inches.

The amount of density,

there's many aspects that we have considered because use 

oxidation is a normal function of processing 

the developer is consumed.

It needs to be consumed and therefore we take 

this into consideration and we have a replenishment 

system or method whereby we replace that 

which is consumed on a one for one basis.

Now going back to the chart,

we need to see that we have 

Ariel oxidation as well.

This is harder to predict and to adjust.

four,

for instance,

how the chemistry is mixed,

how you mix your developer.

If you for instance,

take the developer and dump it into the 

replenishment tank or a mixing vessel and use the pressure 

of a water hose to supply the water 

itself.

The force of the water will create a larger 

vortex and is necessary.

This increased surface area will allow those 

preservatives within the developer to react with air 

and produce secondary developer 

products.

Now the secondary developer products are there to 

keep further aerial oxidation from occurring.

However,

the secondary products are not as reactive as 

the original reducing agents.

So we have already less activity.

We have slightly oxidized developer and this is 

not good for good diagnostic clarity.

Second,

the blast of air will create a 

bit of a vacuum.

It will draw air into the chemistry.

Second,

we have air of course in water and 

this all will react with the 

developer and the most usual 

indication of oxidation of the developer would 

be a slightly yellow tinge or 

yellow color in the chemistry itself.

Another way that you can have increased aerial oxidation,

which again means that the developer is 

oxidized or is depleted in some way and 

therefore we don't have sufficient developer to 

fully develop up our image from the latent 

state to the visible state is to have the 

processor on long periods of standby 

without adjusting or compensating 

by replenishment systems.

Of course,

if your stored chemistry is stored in a very hot location 

next to a radiator or a window or non 

ventilated area or underneath the processor.

For instance,

the chemistry should not be stored there because the very high 

heat from the dryer because a more rapid 

oxidation production of air and 

general ariel oxidation of the developer.

A third category of interest is 

chemical contamination or foreign 

contamination.

And the most usual would be chemicals of 

course we have highlights in the water.

We have chlorine in the water to kill germs.

We have flooring to protect our teeth 

and water goes through the earth or comes out of 

the earth.

The soil and highlights are fairly common to earth.

So we have,

hey lies,

this is again known about and 

it's considered in the manufacture of the developers 

at the same time.

You should be aware that you have a municipal water 

supply facility that can advise you if they 

use extra quantities of hail eyes for some 

reason and you should get a 

water analysis sheet from your municipal 

water supply engineer or 

uh sanitation department 

Fixer.

A very small quantity of fixer mixed in with the chemicals 

will cause contamination as small as 

2% by volume because a 

oxidation,

very dramatic oxidation of the developer.

And basically we see this as a 

a failure of contrast in 

the final radiograph that has been contaminated with 

fixer systems cleaners.

Well,

there's two basic types.

The systems cleaner that is most commonly found is 

a self Amick acid based systems cleaner 

and self Amick acids are the single most 

hazardous or violent chemical 

that can attack reducing agents.

So very small quantity will most 

assuredly kill a very large quantity of 

developer reducing agents.

The system's cleaners that are most commonly used,

as I mentioned,

are self Amick acid.

And this is a bit of irony 

because the original self Amick acids were used 

in the motion picture industry where they don't have rollers or 

tubing is such that can absorb 

chemicals.

The other kind of systems cleaner would be 

the chlorine based systems,

cleaners,

heavy metals,

copper such as copper,

penny used as an inexpensive screwdriver and dropped in.

The chemicals will cause contamination.

So in all of this we must keep in mind that we 

must indeed control the 

developer,

keep it good,

keep it at its proper activity level.

Because the developer amplifies the system,

It produces the visible image.

We can say that we start with the exposed 

film.

We go through the developer and of course the rest of the chemicals and the 

dryer,

we end up with the final X ray,

the visible image.

The useful image 

that processing completes with the exposure,

started 

radiography begins and ends in the dark room because this 

is where processing takes place.

Sensei tom a tree is defined as the 

quantitative measure of the response of the film to 

exposure and development.

You must have development to produce the useful 

image.

We can see that in this slide we have a radiograph.

This is the sum total of our efforts,

the best diagnostic quality radiograph that we can produce.

We can say that radiographic processing is necessary 

for the production of the visible image.

It links exposure to interpretation and influences 

quality.