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In this article, Orla O’Reilly RVN offers a recap on the principals of producinggood quality radiographs using traditional ionising radiation methods. Thearticle provides refresher points on radiographic principals, and exploreswhat can go wrong during the process and how to correct these problems.

How to: produce agood quality diagnostic

radiograph

Key prINCIpALS

In order to be of diagnostic value, radiographs have to be

of good technical quality. A good radiograph should show

accurately the structure under examination, the quality of 

both contrast and detail should be good and there should

be no misleading artefacts on the film. Many factors

influence the formation of the image:

Positioning;•

Screen and film combinations;•

Exposure factors; and,•

Processing.•

X-rays are a form of ionising radiation and they can be

potentially harmful to living tissue, so personal protection

is very important. A radiograph is the ‘picture’ produced on

film when an object/patient is exposed to this radiation.

The varying levels of absorption of x-rays by different

tissue types produces five radiographic opacities:

Black - gas;•

Dark grey – fat;•

Light grey – soft tissue and fluid;•

Nearly white – bone; and,•

White – metal.•

Kiovotage (kV) refers to the penetrating power of the

beam and the speed of the x-rays. Thicker tissues and

those with a higher specific gravity will require a higher kV

setting. The normal range of kV settings on a veterinary 

x-ray machine is 40 – 125kV with 50 – 70kV being

adequate for most small animal radiography.

Miiampee (mA) refers to the exposure time in

seconds. This dictates the number of x-rays and affects

the density, or the degree of blackening of the film.

NB: If kV is increased by 10, the mAs can be 

halved (and vice versa) to produce the same quality 

radiograph. This can be important when performing

thoracic radiographs when there is a need to keep 

mAs low in order to minimise movement blur fromrespiration.

All exposures should be recorded in an exposure book

which should be referred to prior to any radiographic

investigation to compare with previous exposures. Keeping

such a record should minimise the need for repeat

radiographs due to poor choice of exposure factors, thus

reducing unnecessary radiation exposure to staff and the

patient.

Fim-foca ditance (FFD) is the distance between the

x-ray tube and the cassette. This should be either 70cm

(small animal) or 100cm (large animal) depending on

model. Distance should be kept constant for all x-rays in

order to minimise variables.

Object-fim ditance (OFD) is the distance between the

part of the patient being radiographed and the cassette.

This should be kept to a minimum (directly on plate as

much as possible) to avoid magnification and distortion of 

the image also know as the penumbra effect.

Fim/sceen Combination (Fat/sow). Cassettes with

intensifying screens contain crystals that emit light when

exposed to radiation. Fast screens produce more light for

a set exposure level then slow screens but have larger

crystals. This means that fast screens cause higher

density but poorer detail compared with slow screens

(similar to the pixels of a television; the smaller the pixels

the finer the detail).

light Beam Diaphagm (lBD) refers to an area of light

which directly corresponds to the area or beam of direct

radiation. This allows tight collimation over the specific

area of interest.

NB: To test that the LBD is working effectively, place 

metal paperclips on a cassette at the corners of the 

light beam. When a radiograph is exposed the clips 

should appear white at the corners of the image.

scatte radiation is the term used to describe secondary 

radiation. This is a form of radiation with lower energy 

than direct or primary radiation. It is produced when theprimary radiation interacts with the object and is reflected

in infinite directions. This can adversely affect the quality 

of the radiograph by causing a general blackening of the

film and reduced contrast or fogging. Scatter radiation is

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149Veterinary Ireland Journal Volum 64 Numb 3

an important health and safety concern and so protective

lead clothing and screens are essential to protect

personnel from repeated exposure to scatter radiation. The

amount of scatter increases as both patient size and area

of collimation increases. A grid should be used to absorb

scatter radiation when the area being radiographed is

thicker than 10cm.NB: Lead clothing only protects against scatter 

radiation and not against primary radiation. For this 

reason, personnel should never hold an animal for a 

radiograph in the primary beam.

Manua Poceing involves chemicals (developer and

fixer) in either horizontal or vertical tanks. Developing

stage takes 5 minutes at 20°C, fixing approximately 10

minutes and then the film is washed in cold running water

for 15–30 minutes. This method is very time consuming

and labour intensive and requires good management of 

chemicals in order to avoid significant processing film

faults.

 Automatic Poceing uses the same chemicals but

the film is loaded into an automatic processor. The

temperature is higher and consequently processing is time

reduced. This method requires machine and chemical

maintenance.

Digita Poceing is the quickest and cleanest method

of processing. The contrast of the image can be altered, a

specific area magnified for examination and images saved

to computerised files to avoid multiple storage boxes. The

fact that the image can be edited post processing means

that it reduces the number of repeat radiographs being

carried out which saves on time and personal exposure toradiation.

reCAp:

Sedate/anaesthetise patient as necessary.•

Know exactly what area of the patient is to be•

radiographed and what views are required.

Have good knowledge of the anatomy of the relevant•

area.

Have equipment ready e.g. cassettes, positioning aids,•

markers and grid if applicable.

Wear protective clothing and a personal•

thermoluminescent dosimeter.

Ensure automatic/digital processor switched on•

(automatic processing).

Ensure chemicals are not exhausted and are at the•

correct temperature (manual processing).

Check exposure chart for appropriate settings.•

Ensure access to room by other staff and clients is•

restricted and that safety light is working.

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50 Veterinary Ireland Journal Volum 64 Numb 3

Troubleshooting - What can go wrong and how to correct it:

Exposure and processing aults

Problem Cause Solution

Dark flm Over exposure

Over developed

Developer temperature too high

Excessive ogging 

Reduce exposure actors

Use automatic timer

Use thermometer in tank

Use automatic timer

Pale flm Under exposed

Developing time too shortDeveloper temprtature too cold

Exhausted developer

Developer too dilute

Incorrect flm-screen combination

Increase exposure actors

Use automatic timerUse insulating temperature jacket and thermometer in tank

Keep developer covered to prevent oxidation and water

contamination

Keep record o flm-screen combinations

Poor detail FFD too short

OFD too long 

Uneven screen contact

Increase FFD

Reduce OFD

Check screens regularly 

High contrast

Low contrast

Insufcient kV

High kV

Incorrect processing 

Excessive og 

Increase kV/grid

Reduce kV

Review processing procedures

Blurring Movement

Poor flm/screen contact

Use sedation/GA as required

Take exposure at expiratory pause except when radiographing 

lungs when it should be done at peak inspiration

Keep mAs low and increase kV when imaging the thorax to

avoid movement blur rom respiration

Use new cassette and/or repair

Edge o flm underex-

posed

Grid cut o Correct FFD

Lines on flm when using 

grid

Primary beam not perpendicular to cassette/grid or grid is

upside down

Ensure 90° angle

Ensure correct way up

General og 

Chemical og 

Radiation og 

Localised og 

Prolonged storage o flms

Developer time too long, temperature too high or developer

exhausted

Pre-exposure to radiation

Excessive secondary radiation

Exposure to white light

Incorrect saelight

Prolonged inspection during development

Damaged cassette

Rotate stock

Use automatic timer, thermometer and replace or replenish

developer solution.

Review storage acilities

Reduce exposure actors

Ensure darkroom light proo 

Reer to flm type

Review manual processing 

Check cassettes regularly 

Stains and arteacts

Problem Cause Solution

 Yellow stains Prolonged development in exhausted solutions

Developer temp. too high

Films stuck together

Change or replenish developer solution

Use thermometer in tank

 Agitate in developer

Brown stains Deposits o oxidised developer

Deposits o silver sulphide

Replace developer solution and wash properly 

Wash or appropriate timesBlue-green stains Exhausted chrome alum. fxer Replace fxer solution

Streaking Lack o agitation

Dirty processing hangers

Insufcient rinsing 

Drying marks

 Agitate in developer and fxer

Clean regularly 

Review processing protocols

White splashes

Black splashes

Fixer

Developer

Review processing protocols

White specks and marks Dirt, dust or stains on intensiying screens

Finger prints

Crimp marks

Clear marks surrounded by a ring 

Lightening static marks

Metal tag on collar

Microchip

Clean regularly with proprietary cleaner

Work with clean dry hands

Hold by edges only 

Bubble marks- agitate flm during processing 

Remove flm slowly rom box and place in cassette without

dragging across suraceRemove collar

Scan

Scratching Emulsion sensitive when wet Care with adjacent hangers

Drips and stains Contrast media, urine, blood or water on cassette suraces Clean cassette suraces i soiled or use protective radiolucent

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