Transcript RADIOPHARMACY Diagnostic Nuclear Medicine 3 continue

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RADIOPHARMACY
Diagnostic Nuclear Medicine 3
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Nuclear medicine is a branch of medical imaging that uses small
amounts of radioactive material to diagnose and determine the
severity of or treat a variety of diseases, including many types of
cancers, heart disease, gastrointestinal, endocrine, neurological
disorders and other abnormalities within the body.
Because nuclear medicine procedures are able to pinpoint
molecular activity within the body, they offer the potential to
identify disease in its earliest stages as well as a patient’s
immediate response to therapeutic interventions.
.
Cardiac nuclear medicine is useful in diagnosing coronary artery
disease and cardiomyopathy and identifying possible damage to
the heart from chemotherapy or radiotherapy.
Nuclear medicine, or radionuclide, diagnostic imaging procedures
are non-invasive and, with the exception of intravenous injections,
are usually painless medical tests that help physicians diagnose
and evaluate medical conditions.
These imaging scans use radioactive materials called
radiopharmaceuticals or radiotracers
CARDIAC IMAGING
Perfusion agents for cardiac imaging.
Radiopharmaceuticals are useful in cardiac imaging as agents that provide
information on the regional myocardial blood perfusion.
They typically are administered as part of a cardiac stress test so as to
provide information at peak cardiac output.
The patient will run on a treadmill to “stress” the heart .
IV coronary vessel dilating agents are used in place of the treadmill when the
patient is not physically able to exercise. Examples of these pharmacological
agents are dipyridamole, adenosine, and dobutamine.
The patient will also be imaged when the heart is at rest, usually 3 hrs
following stress study.
1. Thallous chloride Thallium-201 (Tl-201 )
It is used for myocardial perfusion imaging in the diagnosis of coronary artery
disease and localization of myocardial infarction.
Bio-distribution
(1) Tl-201 is a monovalent cation with distribution analogous to a potassium
ion (K ) ; myocardial uptake is by active transport via the Na /K adenosine
Triphosphatase (ATPase) pump.
(2) Bio-distribution is generally proportional to organ blood flow at the time
of injection, with blood clearance by myocardium, kidneys , and liver.
(3) Tl-201 is excreted slowly.
(4) Redistribution allowing to perform rest study in 3 hrs following stress study
with single injection given once at peak stress.
Physical half -life: 73 hr
Primary radiation emissions: 68-80 Kev (mean peak 73 keV) γ- rays
Administration and dosage. IV, 3 mCi (111 MBq)
2.Tc-99m sestamibi ( Tc99m MIBI)
exists as a sterile, pyrogen-free IV injection after kit reconstitution with
Tc-99m pertechnetate and heating at 100°C for 10 min.
Bio-distribution
(1) Tc-99m sestamibi is a cation complex that has been found to accumulate
in viable myocardium by passive diffusion into the myocyte with subsequent
binding to the mitochondria within the cell.
(2) The major pathway for clearance (excretion) of Tc-99m sestamibi is the
hepatobiliary system with bile.
(3) Tow injections are needed for stress and rest studies, given with each study.
Administration and dosage. IV, 10 mCi (370 MBq) Stress study
20 mCi (740 MBq) Rest study
3. Tc-99m tetrofosmin
exists as a sterile and pyrogen- free IV injection ready for labelling with
Tc-99m pertechnetate.
Tc-99m tetrofosmin is a lipophilic, cationic complex that has been found to
accumulate in viable myocardium.
After the Tc-99m pertechnetate is added to the kit , it must be heated in
a hot water bath at 100°C for 10 min to form Tc-99m MAG3.
Bio-distribution
The major pathways for clearance of Tc-99m tetrofosmin are the hepatobiliary
system and the renal system .
Administration and dosage. IV , same as MIBI.
Myocardial Infarction
Myocardial Infarction
Myocardial Ischemia
THYROID IMAGING
Overview
The basic function of the thyroid gland is the product ion of thyroid
hormone for the regulation of metabolism.
The thyroid hormones are produced within the gland through the
organification of iodine obtained from the oxidation of available
iodide circulating in the blood.
The inability of the body to distinguish between the isotopes of
iodine provides a perfect metabolic tracer for the thyroid
biochemical system.
The function of the thyroid gland can be evaluated by the uptake
of I-131 or I-123 , allowing the detection of hypothyroidism
with decreased uptake and hyperthyroidism with increased
uptake.
Thyroid scan
An image taken of a patient's thyroid gland after the patient
swallows radioactive iodine or IV injection of technetium.
The image shows the thyroid gland in action as it accumulates
radioactive material.
Thyroid scanning is used to determine how active thyroid tissue is in
manufacturing thyroid hormone. This can help the physician to
determine whether inflammation of the thyroid gland (thyroiditis) is
present.
It can also show the presence and degree of overactivity of the
gland (hyperthyroidism).
Thyroid scanning is especially helpful in evaluating
thyroid nodules, particularly after a fine-needle
aspiration biopsy has failed to provide a diagnosis.
A scan can reveal whether a thyroid nodule is
functioning.
A functioning nodule actively takes up iodine to produce
thyroid hormone, and so it produces a localized 'hot'
area on the image.
A non-functioning nodule does not take up iodine, and
it produces a localized 'cold' area.
Most nodules, particularly if they are functioning, are
not malignant.
1. Sodium iodide iodine-123 ( I-123 )
is a radiopharmaceutical available in either solution or capsule form
for oral administration.
Bio-distribution
(1) Orally administered iodine is rapidly absorbed from the Gastrointestinal
(GI ) tract ; thyroid gland uptake is evident within minutes.
(2) Sodium iodide I-123 is considered an ideal radiopharmaceutical for iodine
uptake and imaging studies because of its short half- life and useful 160 keV
primary gamma (γ) emissions.
Physical half -life: 13 hr
Primary radiation emissions: 160 keV.27 γ energy photons
Administration and dosage. Oral : 100 μCi (0.1 mCi or 3.7 MBq)
2. Sodium iodide
iodine-131 ( I-131 )
Is not considered an ideal radioiodine radiopharmaceutical for iodine
uptake and imaging studies because of its long half- life, poor imaging
properties, and the high radiation dose to the thyroid from its β decay
component .
The radiation dose from the high-energy β particle with the imaging
potential of its γ emissions make this radionuclide the agent of choice for
therapeutic treatment of hyperthyroidism and thyroid cancer .
Physical half life: 8 days
Decay mode: by β decay
Primary gamma emissions: 360 keV γ energy photons.
Administration and dosage. I-131 is available as either a capsule or in
solution for oral administration. 100 μCi (0.1 mCi or 3.7 MBq)
Tc-99m pertechnetate Thyroid Uptake and Scan
As I-123 is not always available, and I-131 is not an ideal diagnostic agent,
Tc-99m pertechnetate is the most commonly radiopharmaceutical to
evaluate the function of the thyroid gland.
Tc-99m pertechnetate is a monovalent anion with an ionic radius
similar to iodide.
As a result , the pertechnetate ion is trapped by the thyroid gland in a
fashion similar to iodide.
The two species (iodide and pertechnetate) are different in that Tc-99m
pertechnetate is not organified or incorporated into thyroid hormone,
and it is subsequently released unchanged.
Administration and dosage. IV, 5mCi (185 MBq)
Tc-99m sodium pertechnetate
(NaTc-99m O4-)
Normal Thyroid
Cold Nodule
Hot Nodule
Tc-99m pertechnetate
The chemical form of 99mTc available from the Moly generator is sodium
pertechnetate (NaTc-99m O4-).
The pertechnetate ion, Tc-99m O4 , having the oxidation state 7+ for 99mTc,
resembles the permanganate ion.
It has a configuration of a pyramidal tetrahedron with Tc+ located at the
centre and four oxygen atoms at the apex and corners of the pyramid.
Chemically, 99mTcO4 is a rather nonreactive species and does not label any
compound by direct addition.
In 99mTc-labeling of many compounds, prior reduction of Tc-99m from the
7+ state to a lower oxidation state is required.
Various reducing agents are used, among these, stannous chloride
(SnCl2 2H2O), is the most commonly used reducing agent in most
preparations of Tc-99m labelled compounds
Tc-99m pertechnetate
Clinical application
1-Thyroid scintigraphy
Determination of thyroid uptake and morphology
Diagnosis and localization of hot/cold nodules
2-Salivary gland scintigraphy
To assess salivary gland function and duct status
3-Imaging of gastric mucosa
To diagnose ectopic gastric mucosa (Meikles diverticulum)
4-Lachrymal gland scintigraphy
To evaluate nasolachriml drainage
5-Testicular imaging
Tc-99m pertechnetate
Clinical application
6-Barin scintigraphy
Visualization of brain lesions when blood brain barrier is defect (BBB)
7-In vivo labeling of RBCs
Regional blood pool imaging
Detection of GIT bleeding
8-Labeling most of the pharmaceuticals used in NM studies
Thank you and Good Luck
Prof. Dr. Omar Shebl Zahra