Common applications of nuclear medicine

Isotopes
• Greek isos: meaning "same," and topos,
signifying "place"
• Two or more varieties of an element having the
same number of protons but different number of
neutrons.
• Atomic mass (n+p) varies.

• Stable isotopes:
– Without radioactive property
• Unstable isotopes:
– Have radioactive property
– Critical ratio of neutron: proton inside nucleus >1.54

RADIOACTIVE DECAY
• Unstable isotopes decay to lighter isotopes
or elements.
• During this process 3 types of radiations are
emitted
1) Alpha particles
2) Beta particles
3) Gamma rays

Alpha Particles (α)
Radiu
m
R226
88 protons
138 neutrons
Radon
Rn222
Note: This is the
atomic weight, which
is the number of
protons plus neutrons
86 protons
136 neutrons
+ n
np
p
α (4
He)
2 protons
2 neutrons
The alpha-particle (α) is a Helium nucleus.
It’s the same as the element Helium, with the
electrons stripped off !

Beta Particles (β)
Carbon
C14
6 protons
8 neutrons
Nitrog
en
N14
7 protons
7 neutrons
+ e
-
electron
(beta-particle)
We see that one of the neutrons from the C14
nucleus
“converted” into a proton, and an electron was ejected.
The remaining nucleus contains 7p and 7n, which is a nitrogen
nucleus. In symbolic notation, the following process occurred:
n → p + e ( + ν )
Yes, the same neutrino
we saw previously

Gamma particles (γ)
In much the same way that electrons in atoms can be in an
excited state, so can a nucleus.
Neon
Ne20
10 protons
10 neutrons
(in excited state)
10 protons
10 neutrons
(lowest energy state)
+
gamma
Neon
Ne20
A gamma is a high energy light particle.
It is NOT visible by your naked eye because it is not in
the visible part of the EM spectrum.
Mass defect play a key role

Half-Life
The “half-life”
is the time it takes
for half the atoms of a
radioactive substance to decay.

Radiopharmaceuticals
•These are substances that have been synthesized with
radioactive components, which allow the substance to
be followed within the human body.
•Radiopharmaceutical= Radio isotope + Radio ligand

Common radiopharmaceuticals used in
medicine

Technical
Principles of
Nuclear Medicine

The Gamma Camera
• A collimator.
• A detector.
• Electronic systems.
A gamma camera consists of three main
parts:
electronic
systems
detecto
r
collimator

Common Radiological imaging versus Nuclear imaging

Applications of nuclear medicine
• Diagnostic
• Therapeutic

Diagnostic applications
X ray,CT,
MRI
Nuclear imaging

Advantages of nuclear medicine studies
1. Can provide earlier diagnosis since
physiological changes usually occur prior to
morphological changes.
2. Ability to continuously monitor over periods of
time.
3. Provide quantitation when imaging
instruments are interfaced to computers.
4. Noninvasive , minimal risk for the patient.

Outline
• Definition & Historical perspective
• Basic principles of nuclear imaging
• Basic diagnostic tools
• Diagnostic applications
➢ Endocrine system
➢ Cardiovascular system
➢ Digestive & hepato biliary system
➢ Genitourinary System
➢ Respiratory System
➢ Central Nervous System
➢ Oncology & others
• Therapeutic applications

Positron Emission Tomography (PET )
• Make use of positron-emitting radionuclides
that have been injected into the patient.
• Positrons are attracted to electrons, and when
the two meet, they annihilate each other giving
off two gamma rays.
• The gamma rays are then detected by a large
array of sensors.

• The molecule most commonly used :
Flurodeoxyglucose (FDG), a sugar, for which the
waiting period is typically an hour.
• PET scanners can also be used in combination
with MRI and CT scanners to create 3D images.

Diagnostic applications
X ray,CT,
MRI
Nuclear imaging
PET CT

Single-photon emission computed
tomography (SPECT)
• Uses a rotating gamma camera to obtain images
from multiple angles of the organ under study.
• Can yield 2D & 3D images
• Cheaper than PET
• PET gives higher resolution images than SPECT.

Endocrine system
• Thyroid Gland
• Parathyroid Gland
• Adrenal Gland

Thyroid Imaging Study
What can be detected?
• Assessment of the function of thyroid nodules.
• Location of functioning thyroid tissue.
• Diagnosis and follow-up of thyroiditis.
• Workup of Grave’s disease.
• Suspected occult malignant growth.
• Evaluation of congenital thyroid abnormalities.
• Detection and follow-up of thyroid cancer
recurrences/or metastases

How can it be detected?
• Thyroid gland traps iodine & pertechnate.
• Iodine-123 (dose 3–5 mCi, orally) – preferred
Imaging is obtained usually 4 h but up to 24 h post
administration of radiotracer.
• Alternatively, IV injection of 5 mCi of
Tc99m-pertechnetate, scan after 15 mins.
• Anterior and anterior oblique views are obtained
• Nodules may appear as
– solitary or multiple,
– cold (decreased to absent uptake) or hot (increased
uptake).

GRAVES DISEASE V/S
THYROIDITIS…???

Thyroid Cancer Imaging Studies
I-123 24-h whole-body
scan following surgical
removal of thyroid
gland for
differentiated
carcinoma. Residual
neck thyroid tissue
with or without
residual tumor is
evident (arrow)

Parathyroid Gland
• Clinical Uses
1. Preoperative parathyroid localization
Tc99m sestamibi (MIBI) is currently the
preferred nuclear medicine method for
parathyroid imaging.
2. Intraoperative parathyroid localization
The patient is injected 2 h before surgery and
the probe is used to detect the higher level of
activity by the surgeon during surgery.

Parathyroid Gland
• Clinical Uses
1. PARATHYROID LOCALIZATION
➢ Pre operative v/s post operative
➢ Preoperative Tc99m sestamibi (MIBI) preferred
➢ The patient is injected 2 h before surgery and the
probe is used to detect the higher level of activity by
the surgeon during surgery.
1. IDENTIFYING TUMORS

Adrenal Gland
• Clinical Uses
1. Diagnosis of certain adrenal cortical
disorders such as adenoma and
hyperplasia
1. Diagnosis of adrenal medulla disorders
particularly neuroendocrine tumors

Evaluation of Cushing’s syndrome
Adenoma vs Hyperplasia???
CT /MRI preferred modality
–If unhelpful NP-59 study
➢ LDL cholesterol analog that is transported to
specific LDL receptors on adrenocortical cells
➢ Tagged with radioactive iron (Fe 59)
➢ In primary aldosteronism, early unilateral
increased uptake indicates adrenal adenoma,
➢ Bilateral increased uptake suggests adrenal
hyperplasia.

MIBG scan
Metaiodobenzylguanidine (MIBG) is a
guanethidine analog chemically similar to
noradrenaline.
• It localizes in storage granules of adrenergic
tissue
• Scan is performed 24 and 48 h after injection
of 131I-MIBG and at 6 and 24 h after injection
of 123I-MIBG

I-123 MIBG
study
showing large
Pheochromocy
toma

Indium-111 Tc99m Octreotide Study
• Neuroendocrine and non neuroendocrine organs
have surface receptors that bind to
somatostatin.
• Octreotide, a somatostatin analog is used to
evaluate the tumors that contain these
receptors.(it binds to somatostatin receptor subtypes 2 and 5)
• Among these tumors are
– Pheochromocytoma
– Neuroblastoma and paraganglioma,

Cardiovascular System
What can be detected?
1. Assessment of myocardial viability
2. Evaluation of cardiac function
3. Evaluation of myocardial perfusion
4. Evaluation of myocardial metabolism
5. Diagnosis of soft tissue hemangioma
6. Evaluation of lymph drainage.

What is viable myocardium??
• Myocardium that demonstrates abnormal
function at rest but improves with
revascularization.
• Stunning refers to transient myocardial
dysfunction, caused by abrupt cessation of
circulation.
• Hibernation: when viable myocardium has
reduced/altered its metabolic function as a

What is the importance of viability
assessment..??

Viable myocardium
Non Viable myocardium
Revascularize
CAD with depressed LV function
Medical therapy
Non Viable myocardium Revascularize

1. SPECT
• Most commonly used.
• Radiopharmaceuticals used:
– Thallium 201
– Technetium 99 labeled compounds
• Tc-99 Sestamibi
• Tc-99 tetrofosmin
• Tc-99 teboroxime

Thallium 201
• Potasium analogue.
• Utilizes Na/K+ ATPase, accumulates inside
membranes of viable myocardial cells.
• Half life is 73 hrs, single small dose is usually required.
(2-4 mCi)
• Linear relation between blood flow & uptake.
• Property of redistribution.
• Ischemic area: slow uptake, slow wash out.
• Protocol : inj at peak exercise → immediate imaging;
redistribution images 4 hrs after.

Technetium 99 labeled compounds
• Half life 6hrs.
• Larger dose (10-30mCi) ; repeat injection at 4 hrs.
• Redistribution does not occur.
• Sestamibi : better predictibilty, cost prohibitive.
• The criterion for defining viability is represented by a
relative uptake >50% of maximal tracer activity in a
dysfunctional segment.
• Limitation of SPECT : artifacts
• Sensitivity : up to 90%
• Specificity : up to 70%

2. PET
• Gold standard for assessment of viability.
• Sensitivity to predict functional improvement
after reperfusion: up to 100%; specificity: 93%
• Unlike SPECT, PET uses separate agents to
assess perfusion & viability
• Perfusion agents:
– Rubidium-82
– Nitrogen-13 ammonia
– Oxygen-15 water
Text book of cardio vascular
medicine; E. J. TOPOL

• Metabolic agents used in PET include:
– 18 Fluro deoxy glucose or FDG (mc)
– Carbon-11 acetate
– Carbon-11 palmitate
• Long half life of FDG makes its transportation to
ischemic myocardium more likely.
• During periods of ischemia, myocardium utilizes
glucose, instead of fatty acids.
• Uptake of FDG does not occur in normal
myocardium.
• Limitation: FDG PET difficult to analyze results in
diabetics.

Interpretation of PET FDG
• 3 possible interpretation:
1. Normal perfusion: indicates viability on its
own & does not require perfusion scanning
2. Reduced perfusion with intact metabolism:
mismatch indicates hibernating or viable
myocardium
3. Reduced perfusion with impaired uptake
indicates: myocardial scar- reperfusion not
indicated.

Interpretation of PET FDG
Interpretation Perfusion Metabolism
Normal N N
Viable ↓ N
Scar ↓ ↓

Myocardial perfusion imaging
indications
• Assessment of benefit from proposed
revascularization
– Known severe LV dysfunction, Patient eligible for
revascularization
– Ischemic cardiomyopathy
• Diagnosis of CAD
– Low or Intermediate pretest probability of CAD,
where ECG uninterpretable or unable to exercise.
– High pretest probability of CAD, regardless of
ECG interpretability and ability to exercise.

Myocardial perfusion imaging
indications
• Prognosis
– Use of Potentially Cardiotoxic Therapy eg
adriyamycin.
• Post-CABG assessment
To consider need for additional revascularisation
≥ 5 yrs after procedure

MUGA Scan
• The multiple-gated acquisition (MUGA) scan
• Can provide cine imaging of heart
• Helps to assess:
– Pumping action of heart
– Ejection fraction
– Regional myocardial wall motion.

• Patients own blood is mixed with radio isotope
(Tc-99)→Reinjected
• Electrodes are placed on the patient so that a
time frame can be established
• The time frame is divided into several intervals,
or "multiple gates.“
• The result is a series of pictures showing the left
and right ventricles at end-diastole and
end-systole, and a number of stages in between.
• Procedure takes 1hr approx.

Digestive and hepatobiliary system

Clinical uses
1.Localization of lower gastrointestinal
bleeding.
2. Evaluation of esophageal transit time.
3.Evaluation of gastric emptying.
4.Detection of Gastroesophageal Reflux.
5. Localization of Meckel’s diverticulum

Localization of lower gastrointestinal bleeding
• Radionuclide study can detect a bleeding rate
as low as 0.1 mL/min.
• The two common indications for a radionuclide
bleeding study are:
a. Suspected acute ongoing or intermittent lower
GIB of unknown localization with nondiagnostic
endoscopy
b. Follow-up of known bleeding to assess
treatment effectiveness

• Two radiopharmaceuticals are available for the
study of lower GIB:
– Tc-99m-labeled RBCs and
– Tc-99m-sulfur colloid.
• Tc-99m-labeled RBCs is the most commonly
used method. Imaging is begun with injection of
the radiolabeled RBCs.
• Dynamic images are taken at a rate of 1
frame/10–60 s
• Sensitivity of this method is more than 90%.

Evaluation of gastric emptying
• Tc-99m-SC mixed with egg white for solid
meal and water for liquid meal.
• Dynamic images can be taken for 60 min and
if necessary, static delayed images are taken
every 15 min until at least 50% of the stomach
activity has gone into the bowel.
• Normally, the stomach should empty 50% of
the activity measured at time zero by 90 min.

Scintigraphic Nonimaging Procedures
• Carbon-14 Breath Tests-
Useful in the diagnosis of
Helicobacter pylori infections,
lactose intolerance, and
malabsorption due to bacterial deconjugation
of bile acids.

Other Clinical Uses
• Diagnosis of acute cholecystitis (HIDA Scan)
• Diagnosis of common bile duct obstruction
• Evaluation of neonatal hyperbilirubinemia
• Evaluation of complications after
hepatobiliary surgery

Genitourinary System
Renal radiopharmaceuticals
1. Rapidly excreted radiopharmaceuticals: (to
assess renal function)
(a) 99mTc-mercaptoacetyltriglycine (MAG3):
– Agent of choice,
– Excreted almost exclusively by the renal tubules.
(b) 99mTc-diethylenetriamine penta-acetic acid
(DTPA) ,excreted exclusively by glomerular
filtration.

2. The slowly excreted radiopharmaceuticals
(assessment of parenchymal morphology )
(a) 99mTc-dimercaptosuccinic acid (DMSA)
(b) 99mTc-glucoheptonate.

Performing the Renogram
• The tracer is injected into the patient.
• The radioactive material is removed from the
bloodstream by the kidneys.
• Within a few minutes of the injection, the
radiation is concentrated in the kidneys.
• After 10 – 15 minutes, almost all of the radiation
should be in the bladder.
• The gamma camera takes readings every few
seconds for 20 minutes.

Diagnosis
The Renogram
• The computer adds up
the radioactivity in
each kidney and the
bladder.
• This can be shown as a
graph of activity
versus time –
• A time-activity curve.

Imaging Studies
A.Dynamic Renal Scintigraphy (using rapidly
excreted radiopharmaceuticals)
1. Evaluation of renal perfusion and function
2. Diagnosis of renovascular hypertension
3. GFR Estimation
4. Diagnosis and follow up of urinary tract
obstruction
5.Evaluation of renal transplant complications

Captopril DTPA study for screening
renal hypertension
Angiotensin I
ACE ACE inhibitors– sharp drop in
Angiotensin II GFR and proximal
tubular urine flow
Maintain GFR by increasing the tone
of the efferent glomerular arteriole which
raises the glomerular capillary
hydrostatic pressure

Decreased GFR and tubular flow after the
administration of an ACE inhibitor
Decreased uptake and Prolonged cortical retention
prolonged cortical retention without apparent
of 99mTc-DTPA, which is decreased uptake of
excreted by glomerular 99mTc-MAG3 , which
filtration. is a tubular and blood
flow agent

B.Static Renal Scintigraphy
1. Urinary tract infections
2. Evaluation of renal masses
3. Quantitating differential renal function
4. Congenital renal malformations (horseshoe
kidney)

C. Vesicoureteral reflux study
Direct radionuclide
cystography using
Tc99m Sulfur calloid
is a method to
evaluate for
vesicoureteral reflux
(a) Vesicoureteral
reflux study showing
right
side grade II reflux
(arrow).
(b) Bilateral
vesicoureteral
grade III reflux

Respiratory System
Clinical Uses
The most important uses of nuclear medicine in
respiratory system are in the following conditions:
• Suspected pulmonary embolism
• Inflammatory diseases
• Tumors
• Evaluation of alveolar capillary membrane
permeability
• Preoperative quantitation of lung function

Ventilation perfusion scan
• V/P lung scan most cost-effective noninvasive
screening modality.
- Provides regional and quantitative information
useful for the diagnosis
- Determines the disease severity and monitors
its progress.

Agents used for perfusion -Tc99m
macroaggregated albumin
Agents used for ventilation - Xenon 133,
Crypton 81, Tc99m DTPA, and Technegas.
• In pulmonary embolism, perfusion defects are
seen with no corresponding ventilation
abnormalities or mismatching pattern.

Other uses:
• Lung Cancer
– Solitary lung nodule on plain x-ray
– Staging of the tumor
– PET-FDG is particularly useful in staging the
disease and determines the best treatment choice
and in the follow-up of the response to therapy
• Idiopathic Pulmonary Fibrosis
• Diagnosis of pneumocystis jiroveci pneumonia.

Central Nervous System
Clinical Uses
• Partial complex epilepsy and localization of
seizure foci
• Recurrent brain tumors after surgery and
irradiation
• Cerebrovascular insufficiency: Location, size, and prognosis of
cerebral ischemia and stroke
• Diagnosis of brain death
• Brain injury
• Dementia especially Alzheimer’s disease and AIDS dementia
• Diagnosis and follow-up of certain cerebrospinal fluid disorders

Seizure Localization
In epilepsy patient, use of
Tc-99m-HMPAO - ictal state
PET FDG - interictal phase
Localizes epileptic foci in difficult cases where
other modalities cannot provide accurate
localization.

Brain Tumor
Difficulty arises in distinguishing recurrent
viable tumor from cerebral necrosis resulting
from effective therapy or radiation therapy.
Conventional CT or MRI Metabolic imaging
shows mass effect,
edema, and contrast
enhancement in both
cases
Decreased tumor growth
and metabolism in effective
treatment
Increased uptake of
radionuclide markers of
metabolism in tumour
regrowth .

Nuclear Oncology
Clinical Uses
• Diagnosis of Tumors
• Pretreatment staging of malignant disease
• Detection of residual or recurrent disease
• Evaluating response to therapy
• Radiotherapy planning
• Sentinel lymph node localization

Soft Tissue Infection and
Inflammation
Clinical Uses
1.Diagnosis of infection.
2. Localization of infection.
3. Follow-up of infections.

Nuclear medicine modalities
111In or tc99m labeled white blood cells
• acute infections
• postoperative suspected infections
• inflammatory bowel disease
Test :
Obtain blood from the patient → labeling it in vitro
→reinjection the labeled cells.
Images:
• 30 min and 2 h later when tc99m is used .
• 4 and 24 h when indium-111 is used.

67Ga citrate-labeled antibodies
• Chronic infections and PUO of longer duration
• sarcoidosis
• interstitial lung disease
• suspected infections and inflammatory
conditions in HIV patients
Ga-67 study is obtained-
48 h after injection and can continue for up to
2 weeks.

(a) Ga-67 study in a patient with tuberculosis showing foci of abnormal
accumulation of the radionuclide in the right lung (arrow) and a follow-up study
(b) showing almost complete resolution after therapy

Lymphoscintigraphy
The study is used in:
• Primary and secondary lymphedema due to
surgery or irradiation
• Progressing edema without an obvious
etiology

Lymphoscintigraphy study of a patient with right lower limb edema. The 5 min image
shows beginning of ascent of the radiotracer from the injection sites. The 45 and 90
min images shown illustrates normal drainage of the radionuclide in the left side with
visualization of inguinal lymph nodes (arrow ) and lymph channels (arrow head) and
lack of migration in the right side due to obstruction

Therapeutic Applications
of Nuclear Medicine
Oncologic
• Lymphomas and leukemia
• Polycythemia rubra vera
• Solid tumors (thyroid carcinoma,
neuroblastoma, ovarian, prostate, breast,
osteogenic sarcoma, others)
• Treatment of metastasis-induced bone pain
• Treatment of hepatic tumors

Non oncologic
• Benign thyroid disease particularly
hyperthyroidism
• Radionuclide synovectomy
• Bone marrow ablation
• Intravascular radionuclide therapy for
prevention of restenosis.

Treatment of Hyperthyroidism and
Other Benign Thyroid Conditions
• INDICATIONS OF RADIO IODINE USE:
– As an alternative to surgery
– Recurrence of hyperthyroidism- post surgical cases
– Radioactive iodine is the mainstay of therapy for
residual, recurrent, and metastatic thyroid cancer
that takes up iodine and cannot be resected.
❑ CAN SAFELY BE ADMINISTERED EVEN AMONG
YOUNGER AGE GROUP

Technique
• For more than 60 years, iodine-131 has been
used to treat most cases of Graves’ disease and
hyperfunctioning nodules.
• The radioiodine I-131 is swallowed in a single
dose, in capsule or liquid form,
• Quickly absorbed and concentrated from the
blood by the thyroid gland.
• Approximately 20% of the administered activity
is taken up normally by the thyroid gland
• 75% is excreted by the kidney and 10% by fecal
excretion

• A small amount of I-131 is also found in the
– salivary glands,
– gastric mucosa,
– choroid plexus,
– breast milk, and
– placenta.
• Emits beta & gamma rays.
• 90% of effects are seen with in 2 mm- side
effects are minimal
• Half life is 8 days.
• Dose: 60-100 mCi

Precautions
• Pregnancy is an absolute contra indication.
• If breast-feeding, must stop
• Avoid sexual intercourse for one month
• Should not become pregnant for six months
afterwards
• Patients should be warned that if they travel by air,
they may trigger radiation detectors at airports up
to 95 days after their treatment.
• Use private toilet facilities, if possible, and flush
twice after each use
• Avoid prolonged close contact
• Wash hands regularly

Common applications of nuclear medicine

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Common applications of nuclear medicine