Contrast Media

CONTRAST MEDIA :X-RAY,CT,USG

Shivaprakash.B.HPG-BIR

• Contrast means act of distinguishing by comparing the differences,

Or is a perceptual effect of juxtaposition of different colors.

How do I define?• A contrast medium (or contrast

agent) is a substance used to enhance the contrast of structures or fluids within the body

Necessity for use• The contrast in the imaging is

dependent on the variable attenuation of the x-ray beam(number of electrons in path of beam).

Factors affecting• Thickness of the substance

being studied• Its density• Number of electrons per atom

of the element

Where do we use• Intravascular Intravenous CT DSA Intravenous urography Venography (phlebography)

Intra-arterial Angiocardiography Computed

tomography Coronary angiography Pulmonary angiography Aortography Visceral and peripheral arteriography Digital subtraction angiography

• Intrathecal (Use USFDA-approved contrast media only)

Myelography (myelographic nonionic only)

Cisternography (myelographic nonionic only)

• Other Oral, rectal, or ostomy – gastrointestinal tract

Conventional fluoroscopy CT Herniography Peritoneography

Vaginography Hysterosalpingography Arthrography ERCP Cholangiography Nephrostography Pyelography – antegrade, retrograde

Urethrography – voiding, retrograde Cystography Sialography Ductography (breast)

• Miscellaneous Sinus tract injection Cavity delineation (including

urinary diversions, such as loop and pouch)

How do we classify• Water insoluble available in form suspensions

of large insoluble particles as Barium

• Water soluble Iodinated contrast materials

Iodinated contrast materials

Classification of RCM

No of iodine atoms

Osmotic particles

I:P ratio

Mol.wt Iodine content

osmolality

Ionic monomer

3 2 3:2 600-800 70 1500-1700

HOCM

Diatrizoate

Iothalamate

Metrizoate

Non ionic monomer(LOCM)

3 1 3:1 700-800 150 600-700

Iohexol

Iomeron

Ionic dimer LOCM

6 2 3:1 1269 150 560

Ioxaglate

Non ionic dimer LOCM

6 1 6:1 1550-1626

300 300

Iodixanol

Iotrolan

Preference for iodine• High efficacy in absorbing X-

rays within diagnostic energy spectrum

• Chemical versatility allowing allowing stable binding of multiplicity of atoms to one organic molecule

• Low toxicity if released from RCM

Physico-chemical properties• Solubility• Water content• Electrolytes• Calcium binding• O2 tension• Viscosity• Osmolality• Mixing with other fluids• pH and buffering capacity

Does our body react to it? The reactions to contrast

material can be classified as• By systems with various

manifestations• With intensity of reaction and

treatment essence• Mode of reaction to the RCM

• On intensity Mild reaction Signs and symptoms appear

self-limited without evidence of progression

• Nausea, vomiting, Altered taste, Sweats Cough, Itching, Rash, Warmth, Pallor Nasal stuffiness, Headache, Flushing Swelling: eyes, face Dizziness Chills Anxiety Shaking

• Rx-Requires observation Patient reassurance

Moderate • Signs and symptoms are more

pronounced. Tachycardia/bradycardia

Bronchospasm, wheezing, Hypertension Laryngeal edema, Generalized or diffuse erythema, Mild hypotension, Dyspnea

• Rx-require prompt treatment. close, careful observation

for possible progression to a life-threatening event.

• Severe Signs and symptoms are often

life-threatening, including: Laryngeal edema Convulsions

(severe or rapidly progressing) Profound hypotension Unresponsiveness Clinically manifest arrhythmias Cardiopulmonary arrest

• Rx-prompt recognition and aggressive treatment; manifestations and treatment frequently require hospitalization.

To proceed with severe reaction• Airway secured, on artificial

ventilation.• External cardiac massage and

external DC version• IV fluid infusion to restore

blood volume and IV drug administration

• a powerful diuretic frusemide 20–40 mg IV slowly or IM for pulmonary oedema   

•  diazepam and barbiturates for convulsions   

•  adrenaline   •  salbutamol (b2 agonist metered

dose inhaler)    •  hydrocortisone or methyl

prednisolone (100–1000 mg)    •  aminophylline (very slowly,

250–500 mg)   

•    chlorpheniramine for allergic or anaphylactic symptoms   

•    vasopressors, e.g. noradrenaline (or metaraminol 0.5–5 mg slow IV infusion)   

•    dihydroxyphenylaline (or dopamine) infusion (2.5–5μg kg-

1 min-1) for hypotension with monitoring of the blood pressure

• Adrenaline is main stay in treatment of the condition dosage being 0.3-0.5 ml of 1/1000 solution.

• Who react very often Patients with a previous ADR

to RCM Asthmatics Allergic and atopic patients Cardiac patients with

decompensation, unstable arrhythmia, recent myocardial infarction

Renal patients in failure, diabetic nephropathy, on metformin

Feeble infants and aged patients

Patients with various metabolic and haematological disorders

Thyrotoxic: goitrous patients

Premedications• 1.Prednisone – 50 mg orally at

13 hours, 7 hours, and 1 hour before contrast media injection, plus

Diphenhydramine – 50 mg intravenously, intramuscularly, or by mouth 1 hour before contrast medium injection.

• 2. Methylprednisolone – 32 mg orally 12 hours and 2 hours before contrast media injection. An antihistamine can also be added to this regimen.

Patient selection and preparation strategies

• History – A careful, focused history is the necessary first step.

• Hydration – This should be adequate in all patients and is especially important in patients with renal dysfunction or paraproteinemias & in others (e.g., neonates, elderly, & debilitated individuals) who would be compromised by dehydration.

• Have equipment and expertise ready

• Heads up! – Be aware of specific risks, the patient’s status, possible reactions & the best response to them, & where & how to get help.

Special conditions• Pregnancy-iodinated contrast

can be given.Thyroid function of the neonate should be checked in first week of life

• Treatment with beta blockers-may impair response to treatment of bronchospasm induced by RCM

• Lactation-no special precaution required

• Thyrotoxicosis-IV contrast C/I in hyperthyroid.

• Avoid thyroid uptake studies & treatment for two months after iodinated contrast administration

• Pheochromocytoma-advised alpha & beta blockers with orally administered drugs before iodinated contrast

• Sickle cell anemia-risk of ppting crisis,iso-osmolar contrast indicated

• Myelomatosis-Bence jones proteins can ppt in the tubules,adequate hydration required

Why react?• Inhibition of enzymes such as

cholinesterase, resulting in increased concentration of acetylcholine;

• Release of vasoactive substances such as histamine, serotonin or bradykinin may result in vasomotor collapse.

• Activation of physiological cascade systems including the complement activation system

the kinin system with bradykinin release, the coagulation system inducing intravascular coagulation and the fibrinolytic system causing lysis of fibrin and blood clots.

• The immune system disturbances.

• Anxiety, apprehension and fear of the radiological procedure.

• Chemotoxicity depends on intrinsic structure.

Effects on erythrocytes and endothelium depends on hyperosmolaltity.

Due to cation and the anion.• Hyperosmolar reactions Endothelial damage Erythrocyte damage• Blood brain barrier damage• Vasodilatation & hypervolemia• Cardiac depression

Contrast induced nephropathy• Definition CIN is a condition in which an

impairment in renal function (increase in serum creatinine >25% or 44 micromol/L) occurs within 3 days after IV administration of contrast medium in the absence of an alternative cause.

• Markers

• Risk factors Increased serum creatinine

levels,particularly secondary to diabetic nephropathy

Dehydration Congestive heart disease Age older than 70 yrs Concurrent administration of

nephrotoxic drugs(e.g,NSAIDS,Aminoglycosides)

Hypertension Hyperuricemia Multiple myeloma

• Reducing the risk of CIN Identifying pts at risk normal serum creatinine

<1.2mg/dl for females & <1.4mg/dl for males.

serum creatinine >1.5 mg/dl or clearance <60ml/min/1.73 m2 is defined as renal impairment

patients with clearance <30ml/min/1.73 m2 are definitely at risk.

Choice & dose of contrast media. Hydration - normal saline iv 4-6 hrs before

and after contrast medium at rate of ml/kg/hr.

- isotonic bicarbonate 1 hr before at the rate of 1 mL/kg/hr for 6 hrs after infusion

- isotonic bicarbonate with NAC (dose of 1200 mg twice a day for 48 hrs,starting 24 hrs before contrast administration)

• Outpatients with moderate renal impairment (GFR 45-60 mL/min) 1000 mL/hr before & after contrast medium

• Patients receiving larger doses or with advanced chronic renal disease ( GFR < 45 mL/min ) better hydrated with IV saline.

• Pharmacological manipulation NAC reduces nephrotoxicity

through anti oxidant and vasodilatory effects

theophylline fenoldopam & CCB’s can be used.

• DO’s hydrate use low/iso-osmolar RCM stop nephrotoxic drugs 24 hrs

before RCM consider alternatives

• DON’TS use of High osmolar RCM administer large doses of

contrast administer mannitol &

diuretics perform multiple studies within

72 hrs

Contrast agents & renal tract• Intravenous urography better delineation Average adult dose being 20g

of iodine independent of kidney function

- the nephrogram has two components

->vascular blush which is most prominent in 20-60 sec after contrast injection

->tubular opacification which begins 1-2 min after injection.

• Diagnostic quality is related to filtered load,amount of the contrast excreted.

• UV=GFR*P

Contrast agents & the GIT• Contrast agents to consider are• Barium Practical properties - adherence of barium to

mucosal surface - must not flocculate when in

contact with the mucosa

Factors governing• Particle size & shape ranging between 0.1-20 micro

m.• Density of barium w/v or w/w. high density barium >200%w/v medium density 100-200%w/v low density 50-100%w/v• Gums for adherence

• Flocculation of barium usually negatively

charged,flocculates if positive ions are added to the suspension.

• Stabilising agents• Clinical applications for esophagus both single &

double contrast 100%w/v is adequate

for stomach high density barium 240%w/v

• For small bowel if follow through low density barium 40%w/v if small bowel enema higher density about 100%w/v• For large bowel moderate density 80-120%w/v

Complications • Leakage into the pleural or

peritoneal spaces• Leakage into the mediastinum• Possible pulmonary aspiration• Given orally in suspected large

bowel obstruction

Role of iodinated contrast • Investigations of possible leaks

from the upper GI tract, esophagus & duodenum.

• Gastrograffin (75% aqueous solution of sodium & methylglucamine diatrizoate with 0.1% Tween 80)

Uses • Esophageal tear• Duodenal perforation• Small bowel ileus vs mechanical

obstruction• In CT 3% solutions 1 hr before

the procedure• Investigation & treatment of

meconium ileus• Post surgical anastomosis

C/I’s• Causes severe chemical

pneumonitis so c/i in case of suspicion that aspiration into bronchial tree may occur.

• Hyperosmolar effect draws water into the bowel loops in a small child & infant may cause severe electrolyte disturbance & death.

• In this cases Non ionic contrast iopamidol with flavouring agent is used.

Biliary system• Cholecystographic agents

(iopadate & iopanic acid)• Cholangiographic agents

(meglumine iotroxate) Contraindications & adverse

effects• Oral agents Hepatic dysfunction Parotitis skin rash & most

commonly GI symptoms diarrhoea.

• IV agents Acute anaphylactoid reactions Bronchospasm &

cardiovascular collapse• Absolute contraindications myeloma & waldenstrom’s

macroglobulinemia

Contrast agents in Ultrasound• Requirements Easily introducible Stable in the duration of

examination Low toxicity Modify one or more acoustic

properties of tissues

Blood pool agents• Free gas bubbles normal saline indocyanine green renograffin• Limitations large in size effectively filtered

by lungs unstable,go back into the

solution withinn second or so.

• Encapsulated air bubbles Levovist 99.9%

microcrystalline galactose microparticles & 0.1% palmitic acid

microbubble size 3 to 4 micro m.

Echovist a galactose agent with larger bubbles used for visualisation of non vascular structures

• Low solubility gas bubbles To increase back scatter &

longevity of the bubbles,low solubility gases as perfluorocarbons with low diffusion rate & increased longevity are used.

Sonovue with sulfur hexafluoride & phospholipid

Optison with perfluoropropane filled albumin shell

• Selective uptake agents Colloidal suspension of liquids

are taken up by the reticulo endothelial system from where they are excreted

Levovist provides late phase of enhancement in liver parenchyma & spleen.

Bubble behaviour & incident pressure

• Microbubbles scatter ultrasound in a manner dependent on the sound to which they are exposed

• At low incident pressures they produce linear back scatter enhancement,resulting in augmentation of the echo from the blood

• As it increases the beyond 50 to 100 kPa contrast agent back scatter begins to show non linear characters,such as emission of harmonics

• As peak pressure reaches near 100 kPa transient non linear scattering resulting in destruction of the bubble

Peak pressure Bubble behaviour

Acoustic behaviour

Application

<100 kPa Linear oscillation

Linear backscatter enhancement

Doppler signal enhancement

0.1-0.5 mPa Non linear oscillation

Harmonic backscatter

Real time vascular imaging

>0.5 mPa Disruption Transient non linear echoes

Interval delay perfusion imaging

Thank you