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RADIATION & RADIOISOTOPES IN
MEDICINE
Acute Radiation Exposure
Radiation Dose Effect
• 1 rad to bone marrow • Risk of leukemia is 2 in 100,000
• 10 rad, whole body • Elevated number of chromosome
abberations: No detectable injury or
symptoms
• 100 rad, whole body • Mild radiation sickness -- nausea,
vomiting, fatigue are possible
• 400 rad, whole body • Likely to result in death for 50%
of exposed and untreated population
• 1,000 rad, whole body • Erythema and blistering
• 4,000 rads or more, whole body • Death within 48 hours from shock
and vascular damage
• 1,000 - 6,000 rads, small volume • Used to treat cancer over 6 weeks
The Effects of Radiation
Depends Upon
1. The energy of radiation
2. The dose rate
3. Time total dose is received
4. Part of the body exposed
Background radiation (average) 363 mrem/yr
Trans Atlantic Flight at 38,000 ft 5 mrem
Chest x ray 10 mrem/film- 15
mrem/film
Nuclear Medicine Study 430 mrem
Nausea and Vomiting 100,000 mrem
(100% survival) (acute)
Lethal dose (bone marrow) 325,000 mrem
50% in 60 days (LD50/60) (acute)
Cancer treatment series 6,000,000 mrem/
6 wks
ACUTE RADIATION
SYNDROME
* An acute illness, which follows a roughly
predictable course over a period of time ranging
from a few hours to several weeks after exposure
to ionizing radiation.
• It is characterized by the development of group of
signs and symptoms which are manifestations of
reactions of various body systems to irradiation of
the whole body or to significant portion of it.
EARLY CLINICAL CLASSIFICATION OF PATIENT
FEATURES DURING THE FIRST 48 HOURS
1. No nausea, vomiting or diarrhea
Lymphocytes above 1500 cu mm at 48 hrs
No erythema or local symptoms
Probable no life threatening injury
2. Nausea, mild vomiting, possibly diarrhea
Possibly conjunctival redness or erythema
Lymphocytes 800 to 1500 at 48 hrs
Probably serious injury. Plan for therapy.
3. Pronounced nausea and vomiting, possibly diarrhea
Possible erythema and conjunctival redness
Lymphocytes 100-800 cu mm at 48 hours
Probable life threatening injury. Plan maximal
therapy.
4. Prompt severe vomiting and bloody diarrhea
Erythema, hypotension, lymphocytes below 100 cu
mm at 48 hours
Almost certainly lethal exposures. Supportive
therapy.
CLINICAL COURSE OF ACUTE RADIATION
SYNDROME
IRRADIATION
0-48 hours Hours-28D Hours-30D Hours-60D
PRODROMAL LATENT MANIFEST DEATH /
ILLNESS RECOVERY
•ANOREXIA Prodrome •IMMUNOSUPPRESSION
•NAUSEA Absent or •INFECTION
•VOMITTING Diminished •VOMITTING and
•DIARRHEA DIARRHEA
•FEVER •ELECTROLYTE
•CONJUNCTIVITIS IMBALANCE
•ERYTHEMA •HEMORRHAGE
•BLOODY DIARRHEA
•HYPOTENSION
•CV/CNS EFFECTS
Treatment of Radiation Injuries
• * Standardized therapeutic protocols (treatment
schemes) do not exist
• 1. Symptomatic treatment
• IV Fluids, blood transfusion, analgesic,
• antipyretic. antibiotics, antiemetic, etc.
• 2. Wound cleaning and prevention of infection
• 3. Improve local microcirculation
• 4. Reconstructive and plastic surgery
• 5. Amputation for very severe injuries
• 6. Long term and careful clinical
observation and evaluation ( local
injuries are characterized by excessively
prolonged or incomplete healing)
MEDICAL USES OF RADIATION
• Sources of Medical Radiation
1. Diagnostic and interventional x-rays
2. Diagnostic and Nuclear Medicine application
3. Radiation therapy from either external or
internal sources
• Difference of Medical Radiation from
other Radiation Sources
1. Those exposed directly benefit from it
2. Dose received is over a short time only
3. Dose given to limited portion of the body
only
4. Exposed population is selected
Medical Uses of X Rays
• Biological Effects
– Affects all tissues of the body
– Affects rapidly growing tissues more than
normal tissues
• Used in treatment of cancers
• Why it affects the fetus and the reproductive
system
1. Used in the diagnosis of diseases
• X ray of the different parts of the body to determine the
presence, type and nature of diseases
• To localize foreign bodies
• Special procedures
• Mammography – to determine presence of breast
mass
• GI series – determine diseases of the gastrointestinal
tract
• KUB-IVP – determine diseases of the kidneys
• CT Scan – to determine disease of the brain
• Cerebral angiography
• Ventriculography, etc.
2. Used in the treatment of diseases like cancers and
other tumors
3. Uses in pregnancy
• To demonstrate fetal parts in suspected pregnancy
• To demonstrate fetal abnormalities
• To demonstrate the lie, presentation, and maturity of the fetus
• To show presence of cephalo pelvic disproportion
• In suspected fetal death
4. For fertility work up
• Hysterosalphyngography
– Indication:
» Infertility
» Repeated abortions
» Uterine bleeding
NUCLEAR MEDICINE IMAGING
INSTRUMENTS
1. GAMMA CAMERA
• Most common; it does not emit ionizing radiation,
merely detects radiation emitted by patient
2. SPECT – Single Photon Emission Computerized Tomography
• Produces cross sectional images of radio tracer
distribution in the body
• It has the ability to remove overlying structures which
may obscure an abnormality
3. PET – Positron Emission Tomography
• Enables blood flow, metabolic rate and receptor
density to be measured
• Projections are acquired simultaneously
4. CYCLOTRON – particle accelerators
• Linear accelerator, cyclic accelerator
• Bombardment of the target by a beam of particles
created by the ionization of a gas
Proportion of Imaging Procedures
Thyroid - 40 %
Cardiac - 30 %
Pulmonary - 10 %
Bones - 7%
Renal - 3%
Liver and gall bladder - 3%
Gastrointestinal - 1%
Miscellaneous - 1%
Gamma Camera – principal instrument for
imaging in Nuclear Medicine
1. Thyroid Imaging
Radiopharmaceutical Used Activity Radiation Dose
Tc 99m 1-10 mCi 1.5 – 15 mGy
I 123 0.5-1 mCi 7.5-75 mGy
:: Radiation dose given by IV then imaged with Gamma Camera
Clinical Application
• To confirm the presence of nodule within the thyroid
• To identify the functional characteristic of the nodule
• To demonstrate the presence of multiple nodule
2. Cardiovascular Imaging
Radiopharmaceutical Used Activity Radiation Dose
Tc 99m 10-20 mCi
TI 201 0.5-3 mCi 3-5.5 mGy
:: Patient is made to exercise then the radiopharmaceutical is injected by IV
then imaged with a gamma camera.
Clinical Application:
• To evaluate patients with coronary artery disease
• To evaluate patients who had undergone coronary bypass
• To evaluate patients with Acute MI
• To monitor results of coronary artery angioplasty
• Shows the quantity, size and extent of lesion
3. Bone Imaging
Radiopharmaceutical Used Activity Radiation Dose
Tc 99m 10-20 mCi 5.6 – 12 mGy
Clinical Application
• For staging cancer
• Diagnosis of patients with breast cancer before surgery
• To determine the extent of metastasis
• To evaluate the result of therapy
• To investigate bone injuries
• To assess the size and extent of bone tumor
• To confirm the presence of osteomyelitis
• To investigate bone pains
4. Kidney Imaging
Radiopharmaceuticals Used:
• Technitium 99m
• Iodine-125
• Chromium
Clinical Application
• To evaluate extent of injury in kidney trauma
• To localize obstruction
• To evaluate kidney function
• To confirm presence of secondary kidney damage
5. Liver Imaging
Radiopharmaceutical used Activity adm.
Tc 99m 7-15 mCi
Clinical Application:
• To determine normal liver function
• To determine the presence of hepatic cirrhosis
• To determine the presence of fibrosis secondary to toxicity
• Chronic hepatitis
6. Diagnosis of the different types of cancers, the
stages, the extent of metastasis, etc.
7. Diagnosis of rheumatoid arthritis and
osteoarthritis
• Shows grade of inflammation and degenerative process
PRECAUTIONS IN PREGNANCY FOR
NUCLEAR MEDICINE PROCEDURES
1. If possible, defer study until later stage of
gestation.
2. Give minimal dose (should not exceed I-2 mSv)
3. Hydrate patient and encourage to void
frequently to decrease time of exposure of fetus
4. Pertechnitate and Gallium which concentrate in
the placenta should be avoided
5. Limit the procedure to those which are
absolutely necessary only
POSSIBLE EFFECTS TO THE
FETUS
1. Risk of fetal cancer
(1 in 100,000) - < 1-2 mSv
> 2 mSv (8 in 10,000)
2. Hypothyroidism
3. Cretinism
DESIRABLE PROPERTIES OF
RADIONUCLIDES USED IN NUCLEAR
MEDICINE
• Diagnostic and Therapeutic
1. Posses a relatively short half life
2. Should not emit particulate radiation
3. Should emit gamma radiation with energy high
enough to be detected
4. Not emit gamma radiation with energy so high
as to make detection inefficient
5. Be available in the highest specific activity to
avoid toxic response in patients
• 2, 300 radionuclides
Following are used in diagnosis:
1. Technetium 99m – 80% used
2. Thallium 201
3. Gallium 67
4. Indium 111
5. Iodine 123
Following are used in treatment
1. Iodine 131
2. Phosphorus 32
3. Yttrium 90
4. Radium
5. Iridium
6. Argon 40
7. Cobalt 60
8. Cesium 137
9. Carbon 12
10. Neon 20
11. Silicon 28
TECHNECIUM 99M – ideal radionuclide for
use in Nuclear Medicine because:
1. It is a pure gamma emitter
2. It has a short physical half life
3. It has a gamma ray energy of 140 kev
4. It is carrier free (no stable isotope present)
5. It can be produced cheaply
6. It can exist in various valency states
Radiation Therapy
1. Iodine 131 therapy in thyroid cancer 50-200 mSv at 3
months interval for 3 years
2. Radium needle treatment in tongue cancer
Iridium 192 hairpin treatment in cancer of the tongue,
palate and gums then subjected to intraoral electron
beam at 40-50 Gy
3. Treatment of cervical cancer with the use of: Co 60
Cs 137
4. Heavy Particle radiation therapy for the different types
of cancer using carbon 12, neon 20, silicon-28, argon 40
5. Fast Neutron Therapy
6. Proton radiotherapy for the treatment of cancers
of the head and neck, spine and tissues
7. Radiotherapy and Hyperthermia – heat treatment
with radiation – also for the treatment of the
different types of cancer
8. Intraoperative radiation therapy – used in deep
seated tumors which are difficult to operate
9. Treatment of Breast cancer and other cancers
after surgery with Co 60
10 Leading Causes of Mortality in the
Philippines
1. Diseases of the Heart
2. Diseases of the vascular system
3. Malignant neoplasms
4. Pneumonias
5. Accidents
6. Tuberculosis, all forms
7. COPD & Allied Conditions
8. Conditions pertaining to the perinatal period
9. Diabetes Mellitus
10. Nephritis, Nephrotic Syndrome and Nephrosis
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