Nuclear Medicine Topics

8/9/2019 Nuclear Medicine Topics

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Nuclear M edicine T opics By A bdel- R ahman A bdel- H aleem

GAMMA CAMERA

1. The Multi-hole Collimator:

Composition: It consists of a lead disk, drilled with about 20.000 circular holes

(each hole = 2.5 mm), the holes are separated by lead septa (0.3 mm thick)which absorb the rays attempting to pass through them obliquely.

Dimensions: measures 40 cm in diameter and about 2.5 cm thick.

Function: it directs gamma-rays emitted from the patient and rejects the rays

attempting to pass though them obliquely.

2. The Crystal:

Composition: it is a single large phosphor crystal made of NaI (Sodium iodide),

activated with a trace of thallium.

Dimensions: 50 cm in diameter and 9-12 mm thick.

Function:

o Absorption of Gamma-rays, principally by the photoelectric process, each

gamma-ray (photon) when absorbed by the crystal produces a flash of light.

o The flash contains about 5000 light photons that travelling in all directions,

the distribution of light leaving the crystal depends on which collimator hole

the gamma-ray passed through.

3. Photo-Mult iplier Tubes (PMT):

Composition: each photomultiplier consists of an evacuated glass envelope

containing a photocathode coated with a material that absorbs light (coming

from the crystal) and emits electrons (photoelectrons).

These photoelectrons are accelerated towards a positive anode. In their route the electrons strikes a series of dynodes.

When each electron strikes a dynode it gives out 3-4 electrons, which are then

accelerated, to strike the next dynode. (Multiplication factor is about 106

).

Finally, each initial flash of light produces a pulse of charge that could be

measured electronically.

4. Pulse Arithmetic Circuit :

It is a microprocessor chip that combines the pulses from all the PMTs according

to certain equations.

This is responsible for accurate positioning of the images.

5. Pulse Height Analyzer (PHA):

The main function is to choose certain energy and discard any other unwanted

energies. i.e. reject pulses which are either lower or higher than pre-set level.

In case of 99mTc the window might be set at 126-154keV, centered on 140keV.


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6. The Computer:

The computer system uses the coming X-, Y- and Z- pulses to build up a digital

image in a 128 128 matrix, and store this image in the memory.

Then the digital images can be displayed on a monitor screen.

The stored image can be manipulated and improved: the background can be

suppressed, contrast enhanced by windowing.

Quantitative data can be extracted, e.g. a plot of activity along a selected line.

7. The Monitor :

The display system converts the previous data to thousands of light dots, make

up the image.

The brightness of each pixel depends on the number of counts i.e. the number of

gamma-rays which have emanated from the corresponding area of the patient.

Two types of monitors:

1) Long persistence screens: on which each dot of light persists for a long timefor a visual image to build up the image quality is not good enough for

diagnosis but it is helpful for positioning the patient and making sure that the

activity has been taken up.

2) Short persistence screens: on which each dot quickly dies away but can be

captured on film, gives high quality images.


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TECHNETIUM GENERATOR

Why technetium?

Because it fulfills most of the desirable criteria of the ideal radionuclide, as it has:

1. Suitable physical half life = 6 hours and suitable effective half life.

2. Pure gamma emitter.

3. Emit gamma rays with suitable energy = 140 keV.

4. Emits monoenergic gamma rays (only 140 keV).

5. Easily and firmly attached to many pharmaceuticals e.g.

DTPA.

6. Have low toxicity.

7. Readily available and cheap (as it is generator product).

Structure of the generator:

o The generator consists of parent radionuclide (99Mo)

column (with alumina Al2O3), shielded with lead.o 99m-Tc is not bound to alumina and eluted with sterile

saline.

o Elution can be made daily, but the strength of successive

eluents deceased with the decay of 99m Mo.

o After a week, the generator is replaced and the old one is

returned for recycling.

Radiopharmaceuticals

Desirable propert ies of a radionuclide for imaging:1. Suitable physical half life (few hours), similar to the time from preparation to

injection.

2. Suitable effective half life:to be eliminated from the body with effective half life similar to the duration of

the examination, to reduce the subsequent dose to the patient.

3. Pure gamma emitter (which produce the image) i.e. not emitting alpha or beta

particles (which have a high linear energy transfer and only deposit dose in patient).

4. Emit gamma rays with suitable energy (50-300 keV) and ideally about 150 keV:This range of energies is high enough to exit from the patient and low enough to

be easily collimated and easily measured.

5. Emits monoenergic gamma rays: so the scatter can be eliminated by energydiscrimination by the pulse height analyzer.

6. Easily and firmly attached to the pharmaceutical at room temperature and has

high stability invivo and invitro.

7. Have low toxicity.

8. Readily available and cheap.


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DEFINITIONS

Radioactivity:A physical process in which unstable nuclei gets rid of extra energy by emitting particles

(e.g. B or Alpha particles) or gamma rays , to reach the stable state.

Nuclide:A type of atom specified by its atomic number, atomic mass, and energy state.Isotope:

Form of an element having same atomic number but different atomic weight and

different radioactivity. Isotopes of the element have the same chemical properties, but

differing in physical properties.Example: Oxygen occurs in nature as 3 different isotopes, each with 8 protons (sameatomic number). The most common isotope is 16O (8 protons, 8 neutrons), whichconstitutes 99.7% of all oxygen atoms on earth. There is also the rare isotope 18O (0.1%)and the even rarer isotope 17O.

Radioactive isotope:unstable isotope that made radioactive.

Isomer:nuclide with different energy state: each of two or more nuclides that have the same mass numberand atomic number but different energy states and half-lives.Any of two or more nuclei with the same mass number and atomic number that have differentradioactive properties and can exist in any of several energy states for a measurable period of time.

Isobar:Any of two or more kinds of atoms having the same atomic mass but different atomic numbers.

Half-life- the time required for something to fall to half its initial value.

Physicalhalf-life (1/ t phys):= the time in which a radioactive substance will lose half of its activity through disintegration.=the average time required for the decay of half the atoms in a given amount of a radioactivesubstance.Note: The half-life of a substance does not equal half of its full duration of radioactivity. For

example, if one starts with 100 grams of radium 229, whose half-life is 4 minutes, then after 4minutes only 50 grams of radium will be left in the sample, after 8 minutes 25 grams will be left,after 12 minutes 12.5 grams will be left, and so on.

Biologic half-life (1/t biol):The time in which a living tissue, organ, or individual eliminates, through biologic processes, half ofa given amount of a substance that has been introduced into it.

Effectivehalf-life (1/ t eff): The half-life of a radioactive isotope in a biologic organism (human tissues) , resulting from the

combination of radioactive decay and biologic elimination. The effective half-life is shorter than either the biological or physical half-lives.

It depends on the radiopharmaceutical used and the target organ, also it can vary from personto person.

1/t eff =1/ t biol +1/t physCurie:

A unit of radioactivity equal to the amount of a radioactive isotope that decays at the rate of3710

10disintegrations per second

Becquerel:The SI derived unit used to measure the rate of radioactive decay, equals to one nuclear decay(disintegration) per second


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General Scheme

I nd i ca t i ons: indications may be classified into:

A. Assessment of the organ anatomy.

B. Assessment of the function.

Contra ind ica t ions:o Pregnancy.

o Breast feeding.

o Contraindications to CM: e.g. hypersensitivity to Iodine.

Rad iopharm aceu t i ca ls ( t r ace rs ) :o Mode of action: .

o Gamma-emitter = . Kev

o Half life: ..minutes, hours or days.

o Dose: . mCio Route: ..

o Advantage: ..

o Disadvantage:

Equ ipm en t :o Gamma camera preferably with dual head for SPECT (Single Photon Emission

Computed Tomography) studies.

o Collimator:

Low-energy general purpose collimator (for 99mTc-labelled tracers).

Pat ien t p repara t ion :

Pa t ien t pos i t i on : The patient lies supine

Every effort should be made to position the camera as close to the patient as

possible.

Patient immobilization for the duration of image acquisition is very important.

Technique:

I n t e r p r e t a t i o n :


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RADIONUCLIDE THYROID IMAGING

I nd i ca t i ons:1. Assessment of the gland size and shape.

2. Assessment of the gland function (hyper- or hypo- thyroidism).

3. Post-operative (e.g. post-thyroiectomy) assessment.4. Detection of thyroid nodules and differentiate between cold and hot ones.

5. Detection of ectopic thyroid tissue.

Contra ind ica t ions: General

Radiopharmaceut ica ls :99 m Tc Per techneta te (mostly commonly used):

o Mode of action: Pertechnetate ions are trapped in the thyroid tissue by an

active transport mechanism, but are not organified.

o It carries the properties of99m Tc:

Gamma-emitter = 140 Kev

Physical half life = 6 hrs.o Dose: 3-5 mCi.

o Route: IV.

o Advantages: cheap and available.12 3 I - sodium i od ide :

o Mode of action: Iodide ions are trapped by the thyroid in the active transport,

and organified, allowing overall assessment of thyroid function.

o Gamma-emitter = 159 Kev

o Half life: 13 hours.

o Dose: 100 mCi

o Route: orally.o Advantage: it is the agent of choice, not emit B particles

o Disadvantage: expensive with limited availability (as it is a cyclotron product).

13 1 I - sodium i od ide :o Mode of action: as

o Gamma-emitter = 364 Kev

o Half life: 8 days.

o Dose: 100 mCi (5 mCi orally in case of whole body scan)

o Route: Orally.

o Disadvantage: expensive with limited availability (as it is a cyclotron product)

and emits B particles (not pure gamma-rays).Equ ipm en t : Gamma camera with pinhole collimator (in cases of I-labeled pharmaceuticals).

Pa t ien t p repara t ion :1. Stoppage of anti-thyroid drugs e.g. Carbimazole for 2 days before scanning.

2. Stoppage of thyroid hormones e.g. thyroxin 4 weeks prior to examination.

3. The patient should avoid IV contrast media e.g. for IVP for 4 weeks before

examination.


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Pat i en t pos i t i on :

The patient lies supine, with extended neck and the camera anterior to the neck.Techn ique:

Static scan

1. Imaging starts 20 min after IV 99mTc injection and 4 hours after IV 131I.2.The patient is asked not to move and not to swallow or talk during imaging3.Views:

o Anterior view and Oblique 45 views.o Anterior view with markers to the thyroid cartilage and the suprasternal notch.

Dynamic scan

1. Imaging starts immediately after IV 99mTc injection and images taken every 15sec. for 30 min.

2. It is useful in assessment of perfusion and blood supply of the gland andlesions detected.

Whole-body scan (using 131I):

Used for locating sites of metastasisI n t e r p r e t a t i o n : ( n o r m a l t h y r o i d sc an )

The normal gland exhibits homogenousdistribution of the tracer.

Its configuration has the appearance of abutterfly or wide V.

Each lobe has a height about 5 cm (withthe right being 0.5 cm larger than the left in

of patients) and width of about 2 cm.

The size of the isthmus varies from thinand barely visible, to wide producing an

intense image.

The pyramidal lobe can be found in asmall proportion of normal scans.

No retro-sternal extension.


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RADIONUCLIDE BONE IMAGING

I n d i ca t i o n s:1. Bone tumors: e.g. benign tumors e.g. osteoid osteoma & chondroblastoma-

malignant tumors e.g. osteosarcoma and metastasis.

o Early detection (6 months earlier than X-ray) and staging.o Differentiation between benign and malignant neoplasms.

2. Bone trauma:

o Detection of bone trauma not obvious on X-ray e.g. stress fractures.

o Assessment of blood flow to the adjacent areas.

3. Bone infections: e.g. osteomylitis.

4. Metabollic bone diseases such as hyperparathyroidism, osteoporosis,

osteomalacia.

5. Medicolegal: to differentiate between recent and old fracture.

6. Pagets disease.

Rad iopharmaceut i ca l :9 9 m Tc -m e t hy lene d i - phosphona t e ( M DP) :mostly commonly usedo Dose: 10-20 mCi


o Route: IV.

o Advantages: cheap and available.

Equ ipm en t :1. Gamma camera.

2. Low-energy high-resolution collimator.

Pa t i en t p repa ra t i on :1. The patient should be well hydrated: the patient is asked to drink 2 liters of water.

2. The patient is asked to void immediately before imaging.

Pa t i en t pos i t i on :

The patient lies supine.

Techn ique :

Sta t ic scan: Imaging starts 3 hoursafter IV 99mTc-MDP injection (this to allow the time for the

bone to uptake the tracer from the soft tissues).

D y n a m i c scan (Tr ip le Phase Scan) : 3 phases:

o Arterial phase: immediately after injection (24 frames/5 sec are taken) to

determine perfusion of certain areas of the skeleton.

o Blood-pool phase: 2 min after injection

o Delayed phase: 2-4 hours after injection (the time needed to wash out the

tracer from the soft tissues).


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Norm a l scan charac te r i s t i cs : The greatest amount of the tracer localization occur in the

area where bone has maximum stress either due to weight

bearing or tension from muscular attachments.

Symmetry of right halves, but some diseases may display

this symmetry. Areas that show normal increased tracer localization are

shoulder, acromio-clavicular joints and sternum and

anterior iliac crest.

Both kidneys are visualized.

Causes of diminished tracer uptake:

1. Physiological: steroid therapy, Vitamin D treatment

2. Pathological: e.g. avascular necrosis.

3. Physical: metal prosthesis e.g. metal joint, - cardiac

pace maker mammary implant barium in colon.

Causes of increased tracer uptake:1. Physiological: calcification anywhere e.g. calcified costal

cartilage, heart valve, aneurysm...

2. Extravasation of the tracer at the site of injection

3. Infarctions e.g. heart, brain, spleen...

4. Haematoma.


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RADIONUCLIDE RENAL IMAGING

I n d i ca t i o n s:1. Assessment of renal function, as alternative to IVP in iodine hypersensitivity.

2. Assessment of renal artery stenosis.

3. Assessment of renal perfusion.4. Assessment of renal transplantation.

5. Assessment of reflux nephropathy.

6. Urinary tract infections.

7. Renal trauma.

8. Renal space occupying lesions.

Rad iopharmaceut i ca l :A.

Technet ium labe led Agen t s :

99mTc-D iMercaptoSuccinic Acid (DM SA) :o

Dose: 1-5 mCio Half life: 6 hours.

o Use: retained by the cells lining the PCT, so used in cortical imaging.

o Advantages: cheap and available.99mTc-D iethelene TriaminePentaacitic Acid (DTPA) :o Dose: 3-5 mCi


o Use: 100% excreted by the kidneys (neither metabolized nor absorbed), and used to

measure GFR (glomerular filtration rate).

o Advantages: high excretion efficiency, so high quality images cheap and available.99mTc-MercaptoAcetylt r i Glycine ( M A G - 3 ) :o

Dose: 5 mCi


o Use: cleared by tubular secretion (80%) with only 20% Glomerular filtration.

o Advantages: high excretion efficiency, so high quality images and therefore used in

poor renal function and renal failure.

B.

I od ine labe led Agen t s :

123I -orthoiodo hippurate ( H i p u r a n e )o Dose: 0.25 mCi


o Excreted by tubular secretion (70%) and glomerular filtration (30%)

o Advantage: gives high kidney/background ratio.

o Disadvantage: Expensive as it is a cyclotron product.

Equ ipm en t : As bone scan

Pa t i en t p repa ra t i on : As bone scan

Pa t i en t pos i t i on : The patient lies supine, and the camera against the patientback, except in cases of renal transplantation where the camera should be anterior as

the transplanted kidney is usually located in the iliac fossa.


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Techn ique :

Sta t ic scan: The radiopharmaceutical is administered IV.

Images are acquired at 3 hours (best kidney/background ratio) after injection.

Views: Posterior, right & left posterior oblique.

D y n a m i c scan: The radiopharmaceutical is administered IV and image acquisition is started.

First 2-3 min: rapid framing (one frame/10 sec), then 1 frame every 1 min for 30

min.

If poor excretion is seen from one or both kidneys after 10-20 min, a diuretic e.g.

frusemide 40 mg (Lasix) is given slowly during imaging. Imaging should be

continued for at least a further 15 min.

To obtain a renogram, draw area of interest (AOI) around contour of each

kidney.

N o r m a l r e n o g r am :The no rm a l r enog ram cons i st s o f 3 phases:a. First phase (renal perfusion):

rapid ascending phase

representing perfusion, seen

within 4-6 sec.

b. Second phase (uptake phase):

ascending but less steeper

phase representing the

secretory phase (the tracer is

actively excreted by the

kidney), seen within 1-3 min,

slope of the curve is normally

between 50 to 70%.

c. Third phase (excretion or

clearance phase): descending

representing excretory phase

(the clearance > the intake).

Renogram peak: is the point at

which the input equals the

output through the renal

parenchyma, normally less

than 5 min.


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RADIONUCLIDE LUNG IMAGING

Ventilation (V)perfusion (Q) imaging

Def in i t i on :Ventilation (V)perfusion (Q) scanning is a noninvasive technique for the

assessment of the distribution of pulmonary blood flow and alveolar ventilation.

I n d i ca t i o n s:1. Suspected pulmonary embolism.

2. Evaluation of acute obstructive diseases e.g. asthma.

3. Evaluation of COPD.

4. Quantitive assessment of right to left shunting

Rad iopharmaceut i ca l :

A.Per f us ion scan agen ts : 99mTc -MacroAggegated Albumin ( M A A ) :

o Dose: 3-5 mCi99mTc -microspheres:o Dose: 1-5 mCi

o Disadvantages: expensive.

B.Vent i l a t ion scan agen t s :81K r ( K r y p t o n ) gas:o The ideal agent of choice for ventilation imaging but it has a very short half-life and is

expensive to produce.

o Half life: 13 sec.133Xenon gas:o Half life: 5.25 days.

o Dose: 10-15 mCi

o Advantages:it is cheaper; it is readily available.o Disadvantage: with the lower energy of xenon, the images are of poorer resolution.

99mTc -DTPA Aerosol:o Dose: 40 mCi

Equ ipm en t : As bone scan + gas dispensing system and breathing circuit for ventilation

Pa t i en t p repa ra t i on : the patient should have a chest x ray within 24 hours of the study,as interpretation requires this film to firm suspicions of anatomical abnormalities e.g. cardiomegaly,

kyphosis and to improve the specifity of diagnosis.

Techn ique :

Per fu s ion scan :1. Patient position: The patient lies supine; to avoid the effect of gravity that increases

blood flow to the dependent part of the lung.

2. Perfusion scanning is performed following the intravenous injection of 99m technetium-

labelled protein microparticles which, because of their size, undergo microembolization

in the pulmonary vascular bed.

3. The radiopharmaceutical (MAA) is administered IV directly (particles will stick to a

plastic cannula).

4. Images are acquired.

5. Views: Anterior-Posterior- Lateral - right & left posterior oblique.


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Vent i la t io n scan : 1. The patient is positioned (sitting if possible) initially with his back to the camera.2. The test typically consists of three phases. The first stage is the initial, or ventilation

stage, which reflects the rate of ventilation of the different lung segments. Second is the

equilibrium stage, which represents gas volume of the lungs. The third stage is the

wash-out phase, which demonstrates any gas trapping that may occur in obstructivediseases.

a. Wash in phase: the patient inhales a radioactive gas through a mask placed over

the nose and mouth.

b. Equilibrium phase: the patient is asked to breathe a mixture of oxygen and the

radiopharmaceutical (133

Xenon) and images are taken during late inspiration.

c. Wash out phase: the 133Xenon source is disconnected, the patient breathe

normally and images are taken during expiration.

3. Views: Anterior-Posterior- Lateral - right & left posterior oblique.

Af t e r ca re : No special aftercare is needed. The patient may resume normal activities immediately.

Charact e r i s t i c s o f no r m a l s t udy :An te r i o r v iew :

1. Both lungs show uniform tracer

distribution, with relative photopenia

(decreased radioactivity) at the apices, as

the perfusion is gravity dependent.

2. The heart results in area of photopenia in

the left lower lung field and may encroach

slightly the right lower lung field.

3. The aortic arch shows a concave area of

the left lung.

4. Other mediastinal structures may affectthe medial aspects of both lungs

especially when enlarged.Poste r i o r v i ew :

1. This view shows greater lung volume with

greater concentration of the tracer,

especially in the dependent areas.2. The medial borders of both lungs are

straight and separated by linear midline band of cold spot (the spine).

Com m on pa tho log ica l appearances :Pu lm ona ry embo l i sm:

Characteristically, it results in severe reduction or total loss of perfusion to the areas of

lung supplied by the affected arteries, whilst ventilation remains unchanged or shows

only a minor reduction.

Des t ruc t i on o f l u ng t i ssue ( e .g . em physem a) :It results in patchy loss of both perfusion and ventilation, but the abnormalities are

usually well matched.

I n f ect i ve conso li da t i on :It results in severely affected ventilation whereas perfusion is reduced to a lesser degree

(reverse mismatch).


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RADIONUCLIDE CARDIAC STUDIES

Myocardial Perfusion Imaging (Rest/Stress test)

I nd i ca t i ons:1. Diagnosis and assessment of extent and severity of myocardial ischemia or

infarction.

2. Assessment of myocardial viability: this is a critical issue in management of

patients with myocardial infarctionas patients with viable myocardial segmentsare candidate for revascularization.

3. Evaluation of prognosis.

4. Evaluation of effects on angioplasty and bypass surgery on myocardial perfusion

with pre- and post-intervention imaging.

Rad iopharmaceu t i ca l :

A-201Thallium (201-thallous chloride)o Mode of action: uptake of thallium by the myocardium is based on the fact

that thallium acts a potassium (K+) analogue, and therefore the Na-K pump is

responsible for the cellular uptake.

o Dose: 1-3 mCi IV.

o Physical half life: 73 hr.

o Advantages: single dose -low radiation dose K-analogue.

o Disadvantages: Low Gamma Energy (81 KeV) long half life (73 hrs).

B-99mTc-M ethoxyIsoBu ty l Isonitrite (99mTc MIBI)o It carries the properties of Tc-99m.

o Dose: 30 mCi IV divided into 2 doses.o Physical half life: 140 hr.

o Advantages: better image quality

o Disadvantages: It has minimal redistribution -dose is splitted into 1st dose

before the physical stress and 2nd

dose after 24 hours.

C-99mTc-Tet ro fosmin (Myoview)o Similar uptake characteristics and diagnostic efficacy to MIBI.

Equ ipm en t : 1. Gamma-camera (preferably dual-headed) with low-energy high-resolution

collimator2. Exercise equipment e.g. bicycle ergometer or treadmill.

3. 12-lead ECG monitor.

Pat ien t p repara t ion : 1. The patient should stop cardiac drugs (Beta-Blockers, calcium channel Blockers)

48 hours before the study.

2. The patient should avoid caffeine for 24 h.

3. Fasting for 4-6 hours: to avoid nausea, vomiting during exercise.


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Pat ien t pos i t i on :

The patient lies supine, the camera anterior to the chest.

Techn ique : (us ing 201 TL )The principle: comparison between myocardial perfusion at rest and under stress

conditions (either physical or pharmacological).

Initiate physical or pharmacological stress.

201TL is administered IV at the maximal stress.

Planar imaging:

1- Image after 5 min.

2- Image again at rest 3-4 h after redistribution period, during which the patient

should not eat.

3- Image again after 24 hours (physical and mental rest).

4- Views: Anterior - LAO 45 - LAO 70 - left lateral.

SPECT imaging: (preferably using dual headed camera)

1- SPECT images may be severely degraded by patient movement, so attention

should be paid to keeping the patient very still.

2- 180 orbit from RAO 45 to LPO 45 .

3- Short, vertical long and horizontal long axis views are reconstructed.


Diseased but patent arterial territories will show lower perfusion under stress

conditions than healthy arteries, but show relatively improved perfusion at rest.

Infracted tissue will show no improvement at rest.

Pharmacolog ica l s t ress :

Adenosine infusion 0.14 mg/kg/min, is a potent coronary vasodilator.

It has a short biological half life (8-10 s), so most side effects are reversed simplyby discontinuing infusion.

Contraindications: asthmatic patients, second-degree heart block.

Other agents: Dobutamine Dipyridamole.

Af te rca re :1. Monitoring of the patient post exercise.

2. Examine the patient for any side effects of drugs used.

Compl ica t ions:1. Induction of angina.

2. Cardiac arrhythmias, particularly after dobutamine.

3. Cardiac arrest.


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Acute Myocardial Infarction Imaging

I nd i ca t i ons:Diagnosis and assessment of recent myocardial ischemia or infarction, especially

when other standard tests are inconclusive.


99mTc-py rophospha teo Mode of action: uptake by damaged myocardium and form a complex with

calcium, it also localizes in bone, so rib uptake interferes with planar imaging.

o It carries the properties of Tc-99m:

Gamma-energy = 140 Kev

Physical half life = 6 hrs.

Biological half life = 2.5 days

o Dose: 15 mCi.

o Route: IV.

Equ ipm en t : Gamma-camera (preferably dual-headed) with low-energy high-resolution

collimator

Pat ien t p repara t ion : Fasting for 4-6 hours.

Pat ien t pos i t i on :The patient lies supine, the camera anterior to the chest.

Technique: 99mTc-pyrophosphate is injected IV 2-3 days after suspected infarction.

Planar imaging:

1- Images 3 hours later.

2- Views: Anterior - LAO 45 - LAO 70 - left lateral.

SPECT technique: (preferably using dual headed camera)1- SPECT images may be severely degraded by patient movement, so attention

should be paid to keeping the patient very still.

2- 180 orbit from RAO 45 to LPO 45 .

3- Short, vertical long and horizontal long axis views are reconstructed.


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Radionuclide Ventriculography

Radionuclide Cardiac Angiography

(First pass & Gated blood-pool study)

I nd i ca t i ons:1. Assessment of intracardiac blood kinetics i.e. evaluation of Lt. Ventricular

Ejection Fraction (LVEF) and Rt. Ventricular Ejection Fraction (EVEF).

2. Assessment of myocardial reserve in coronary artery disease.

3. Detection and quantification of intracardiac shunts.


For Fi r st p ass: 99mTc-pe r techne ta teo It carries the properties of Tc-99m:


Physical half life = 6 hrs.o Dose: 12-25 mCi.

o Route: IV.

For Ga ted b lood-poo l s t udy : 99mTc-lab eled RBCs o It carries the properties of Tc-99m:

o Dose: 20 mCi.

o Route: IV.

Equ ipm en t : 1. Gamma-camera with low-energy high-resolution collimator.

2. ECG monitor.

Pat ien t p repara t ion : Fasting for 6 hours.

Pat ien t pos i t i on :The patient lies supine, the camera anterior to the chest.

Technique:First pass angiography:

1- The ECG trigger signal is connected.

2- The tracer is injected IV as a bolus.

3- Rapid serial images are obtained at a fast rate (20 frames/sec or more) for

approximately 20-30 sec.

4- Computer analysis allows definition of the ventricular edges and subtraction

of background counts.

Gated blood-pool study:

1- The ECG trigger signal is connected.


3- Information is gained by successive cardiac cycles are added together in

sequels according to ECG control.


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RADIONUCLIDE LIVER SCANNING

I nd i ca t i ons:1. Diffuse liver diseases.

2. Hepatic space occupying lesions: primary and secondary tumors, abscesses and

cysts.3. Veno-occlusive disease (Budd-Chiari Syndrome).


99mTc-co l lo ido Mode of action: uptaken and cleared by phagocytosis into the

reticuloendothelial cells (especially Kupffer cells of the liver), where it is

retained. Spleen is demonstrated as well as liver.




o Dose: 3-5 mCi.

o Route: IV.

Equ ipm en t : Gamma-camera with low-energy high-resolution collimator.

Pat ien t p repara t ion : Fasting for 6 hours.

Pat ien t pos i t i on :The patient lies supine, the camera anterior to the upper abdomen.

Technique:Static Imaging:


2- images are obtained after 15-30 min

3- Views:

a. Anterior (with costal margin markers).

b. Posterior.

c. Lateral.

d. Obliques: RAO- LPO.

Dynamic Imaging:


2- Rapid serial images are obtained immediatelyafter injection at a fast rate for approximately 20-

30 sec

3- Views: Anterior RAO - Posterior- LPO.

4- SPECT may be used for assessment of diffuse liver disease and to improve

detection of small and deep-seated lesions.

Af te rca reNo special aftercare is necessary.


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Homogenous distribution of the tracer except areas of normal photopenia.

Rapid disappearance of colloid tracer from cardiac pool to the liver and

spleen, increased spleen activity occurs in cases of hyperslenism.

The liver has normally greater activity than spleen.

Causes of focal areas of increased tracer accumulation:1. Inferior and superior vena cava obstruction: this leads to increased

perfusion of the quadrate lobe.

2. Budd-Chiari syndrome: this syndrome is characterized by thrombosis

of the hepatic veins, resulting in decreased blood flow to the liver

except in the region of the caudate lobe.

3. Focal nodular hyperplasia and cirrhosis.

4. Abscess, hemagioma and hamartoma.


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RADIONUCLIDE HEPATO-BILIARY SCANNING

I nd i ca t i ons:1. Suspected acute cholecystitis.

2. Obstructive and non-obstructive jaundice.

3. Suspected bile leaks after trauma or surgery.4. Biliary dilatation.


99mTc-Hepat i c I m inoD iace t i c Acid ( 99mTc HIDA)o Mode of action: uptaken and cleared from circulation by hepatocytes and

secreted into bile in a similar way to bilirubin.




o Dose: 3-5 mCi.

o Route: IV.

Equ ipm en t : Gamma-camera with low-energy high-resolution collimator.

Pat ien t p repara t ion : 1. Fasting for 6 hours.

2. For infants: Phenobarbitone 5 mg/kg/day is given 3-5 days prior to the study to

enhance hepatic excretion of the tracer.

Pat ien t pos i t i on :The patient lies supine, the camera anterior to the upper abdomen.

Technique:Static Imaging:


2- Images are obtained 10 15 20 -25 30 35 40 -45 min after tracer

administration.

Static Imaging:


2- 1-min 128128 dynamic images are obtained for 45 min.

Af te rca reNo special aftercare is necessary.

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Nuclear Medicine Topics