CONTRAST MEDIUMCONTRAST MEDIUM

RAD 323 Lecture. 1

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• Radiographic procedures: By Stephen Chapman• Positioning in Radiography: By k.C.clarke.• Text book of radiographic positioning and related anatomy;bykenneth L.Bontrager,5th edition

References

Websites

• http://www.e-radiography.net/

Learning objectivesLearning objectives

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By the end of this Lecture the student will be able to:

Define the term contrast

Differentiate between subject and radiographic contrast

Identify the subject contrast chart in relation to material type

Differentiate between long scale and short scale contrast

Explain contrast Media Properties

Explain different types of contrast media used in GIT exams

Explain pharmacological agents pharmacological agents used in GIT exams

Differentiate between Retrograde and Antegrade GIT studies

ContrastContrast

Definitions◦"contrast"

exhibit noticeable differences when compared◦"radiographic contrast"

visible differences between densities on an image◦"subject contrast"

difference in the transmission of x rays due to the tissue type in the body part

Subject Contrast DefinitionsSubject Contrast Definitionsradiolucent

◦tissues that x rays easily penetrate◦appear dark gray to black on the image

radiopaque◦tissues that x rays do not penetrate easily◦appear light gray to white on the image

Subject Contrast ChartSubject Contrast Chart

Very Very radiolucentradiolucent

Moderately Moderately radiolucentradiolucent IntermediateIntermediate

Moderately Moderately radiopaqueradiopaque

Very Very radiopaqueradiopaque

BlackBlack Dark Dark graysgrays

GrayGray Light grayLight gray White White (clear)(clear)

GassesGasses

AirAirFatty Fatty tissuetissue

MuscleMuscle

CartilageCartilage

BloodBlood

CholesteroCholesterol stonesl stones

Uric AcidUric Acid

StonesStones

BoneBone

Calcium Calcium stonesstones

MetalsMetals

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Radiation QualityRadiation Quality

Low kVpHigh contrastBlack and WhiteShort ScaleGreat differences

in adjacent structures

High kVpLow contrastMany shades of

grayLong ScaleLittle differences

in adjacent structures

Radiographic Contrast vs. Contrast Radiographic Contrast vs. Contrast MediaMedia

• Radiographic Contrast:Radiographic Contrast: Difference between adjacent densities in a radiograph.• The films or images have different levels of density –

different shades of gray• X-rays show different features of the body in various

shades of gray. • The gray is darkest in those areas that do not absorb X-

rays well – and allow it to pass through• The images are lighter in dense areas (like bones) that

absorb more of the X-rays.

Radiographic Contrast vs. Contrast Radiographic Contrast vs. Contrast MediaMedia• Contrast Media: Contrast Media: Diagnostic agents that are instilled into

body orifices or injected into the vascular system, joints, and ducts to enhance subject contrast in anatomic areas where there is low subject contrast.

CONTRAST

X-RAY DYE

DYE

Purpose of Contrast MediaPurpose of Contrast Media

To enhance subject contrast or render high subject contrast in a tissue that normally has low subject contrast.

Contrast Media PropertiesContrast Media Properties

able to show organ betterphysiologically

◦no permanent alteration of organ◦non toxic◦able to be eliminated / excreted

Contrast MediaContrast Media

Negative contrast

Radiolucent-AIR

Low atomic # material

Black on film

Positive contrast

Radiopaque-BARIUM

High atomic # material

White on film

Contrast Media and

Contrast Media and

Pharmacological Agents for GIT

Pharmacological Agents for GIT

ExamsExams

Barium Sulfate: BaSO4Barium Sulfate: BaSO4

• High atomic number• Not soluble in water = suspension• Used to coat the lining of organs• Supplied in different thicknesses• Used–Esophogram, UGI, Small Bowel,

Lower GI or BEcontraindications

perforations of GI tract proximal to an obstructed

bowelprecautions

adequate hydration post examination

Gastrografin or HypaqueGastrografin or Hypaque

• High atomic #– Close to iodine

• Water soluble• Similar usage as Barium

Water soluble, safe in the abdominal cavity Safe to use if perforation is

suspected Very harmful to the lung tissue

Do not use if aspiration is possible

Why use Barium Sulphate?Why use Barium Sulphate?

It has a high atomic number (Z=56) It has a high atomic number (Z=56)

Non-toxic Non-toxic

Relatively cheap Relatively cheap

body cannot metabolize BaSO4

Buscopan Buscopan Glucagon Glucagon Maxalon Maxalon

Why are they given?Why are they given?

Pharmacological agentsPharmacological agents

Pharmacological agentsPharmacological agents

Buscopan (20mg iv) & Glucagon (0.3mg iv) both relax Buscopan (20mg iv) & Glucagon (0.3mg iv) both relax smooth muscle (Glucagon more potent & can be used smooth muscle (Glucagon more potent & can be used on patients with glaucoma & cardiovascular disease). on patients with glaucoma & cardiovascular disease).

Useful in barium enema examinations. Useful in barium enema examinations. Maxalon (20mg iv/oral) increases gastric peristalsis Maxalon (20mg iv/oral) increases gastric peristalsis

(useful in follow through examinations) (useful in follow through examinations)

Exams of the GI tractExams of the GI tract

Antegrade studies (with the normal flow)

◦ esophagus, stomach, small bowel

◦ contrast barium barium + air oral iodine solution

BaSO4 Only

BaSO4 + Air

GI Studies GI Studies (cont.)(cont.)

Retrograde studies (against the flow)

◦ colon◦ contrast

barium barium + air

BaSO4 Only BaSO4 + Air

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Classification of C.M

1.Negative Contrast Media: •These are contrast media which have: - Low atomic numbers. - So low densities. - Provides negative contrast. Examples: air, nitrogen, oxygen, and carbon dioxide, etc.

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2. Positive Contrast media:These are contrast media which have:- High atomic numbers.- High densities. - Provides positive contrast.Examples:i) Barium sulphate.ii) Organic iodine compounds.

UNIT VII 23

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Routes of introduction of C.M.Routes of introduction of C.M.

Positive contrast media may be introduced by one of the following methods: 1- Intra-vascular injection: Examples: Arteriograms, venogram, and lymphangiogram. 2- Ingestion: Examples: Ba meal oral cholecystography.

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Routes of introduction (continues) 3-Injection directly into the site of interest:Examples: Cystogram and retrogradepyelography. 4- Administered I.V. or ingested and then excreted or concentrated by the organ(s) under examination: Examples: Excretion urography and oral cholecystography.5- Injected and then caused to move (usually by postural changes) to the site of interest: Example: Myelography.

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Factors Influencing the choice of Contrast Media

1. Appropriateness: The C.M chosen should be appropriate for the

necessary examination or investigation e.g. -Ba-sulphate for Ba meal, -Omnipaque for myelogram

2.Acheivable radio-opacity: The contrast medium should provide the

desirable degree of radio-opacity.

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3.Toxicity and /or side effects:

The contrast medium must be safe and non-toxic both locally where it is administered and elsewhere in the body that it may reach. i.e. it should not produce any unwanted effect on the body in general.

4.Viscosity: For some examinations such angiocardiography a relatively low viscosity is desirable to enable rapid injection of a large volume of contrast medium .

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For examinations where the contrast medium is injected and stays in the organ or dissipates slowly from it (e.g H.S.G.) , a more viscous contrast medium can be used.

5. Cost:

The C.M. should be reasonably priced and affordable.

6. Persistence: Some contrast may remain in the body for several years and are thus of use in assessing progress by continuing to show any change in the size of the contrast filled lesion without further injection.

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7. Miscibility:

For some examinations like cyst puncture, the contrast should mix with the fluid into which it is injected. In other words it should mix with the body fluid (e.g. CSF and urine )