Radiation can be useful for medical and research purposes but also carries health risks. Effects depend on radiation dose and whether exposure is localized or whole-body. Early effects from substantial whole-body doses within days to months include acute radiation syndrome with hematologic, gastrointestinal, or central nervous system symptoms. Tissues most sensitive to radiation include lymphoid tissue, bone marrow, and gonads. Localized radiation can permanently damage skin, hair follicles, and fertility depending on dose.

1. Dr Muhammad Salman Khan

2. 
Radiation has been described as a doubleedged sword. On the one hand, radiation itself
is a useful tool for research; medical diagnosis
and therapy and on the other hand, radiation
exposures, especially at high levels, can lead to
increased frequencies or severities of various
adverse health effects.

3. 
To produce a radiation response in humans
within a few days to months, the dose must be
substantial, such a response is called an early
effect of radiation exposure.

4. 
Early radiation responses are described as
deterministic,those that exhibit increasing
severity with increasing radiation dose.

5. 

Radiosensitivity is the relative susceptibility of
cells, tissues, organs, organisms, or other
substances to the injurious action of radiation.
In general, it has been found that cell
radiosensitivity is directly proportional to the
rate of cell division and inversely proportional
to the degree of cell differentiation

6. Highly Radiosensitive
Moderately Radiosensitive Least Radiosensitive
Lymphoid tissue
Skin
CNS
Bone marrow
Vascular endothelium
Muscle
GI Epithelium
Lung
Bone and Cartilage
Gonads
Kidney
Connective tissue
Embyonic tissue
Liver
Lens

7. 
The sequence of events that follow high-level
radiation exposure leading to death within
days or weeks is called the acute radiation
syndrome.

There are, in fact, three separate syndromes
that are dose related and that follow a rather
distinct course of clinical responses.

8. 
These syndromes are;
-Hematologic death
-Gastrointestinal (GI) death
-Central Nervous System (CNS) death

9. 
In addition to the three lethal syndromes, two
periods are associated with acute radiation
lethality;
-Prodromal Period
-Latent Period

10. 
It consists of acute clinical symptoms that
appear within minutes to hours of total body
exposure to the radiation doses of
approximately 100 rad (1 Gy) and may last
from a few hours to a couple of days
-Anorexia, Nausea, Vomiting, Diarrhea.
-Easy Fatigability.
-Reduction in WBCs ( Leukopenia).

11. 
Effect is dose dependent;
-Varies in time of onset
-Severity
-Duration

12. 
After the period of initial radiation sickness, a
period of apparent well-being occurs, which is
called the latent period.
-extends from hrs or less(5000 rad) to
weeks(100 to 500 rad)

13. 
In this stage the symptoms depend on the
specific syndrome and last from hours up to
several months.

14. 
Most patients who do not recover will die
within a few to several months of exposure.
The recovery process lasts from several weeks
up to two years.

15.  Prodromal
Phase symptoms i.e nausea,
vomiting and diarrhea develops, with time of
onset from later than 1 hour to about 24 hours
after exposure and may persist for several
days.

16.  Latent
phase lasts up to a month, relatively
asymptomatic except for some fatigue and
weakness.

17.  Manifest
Illness Phase, characterized by
neutropenic fever, systemic and localized
infections, sepsis, and hemorrhage.

18.  Recovery
Phase begins in 2 to 4 weeks, but as
long as 6 months may be required for full
recovery.
 Death may occur as a result of generalized
infection, electrolyte imbalance, and
hemorrhage.
 Mean Survival Time is 10 to 60 days.

19. Pathophysiology of the GI Syndrome:
 Depletion of the epithelial cells lining lumen of
GI tract.
 Intestinal bacteria gain free access to the
body.
 Hemorrhage through denuded areas.
 Loss of absorptive capacity.

20. 

Prodromal Period: Severe nausea and vomiting
with watery diarrhea and cramps develops
within hours after exposure and may persist
for hours to as long as a day.
Latent Period of 3 to 5 days follows, during
which no symptoms are present.

21. 

Manifest Illness: Return of severe diarrhea,
vomiting with fever; progression to bloody
diarrhea, shock and death without aggressive
medical intervention may occur within 3 to 5
days.
Mean Survival Time is 4 to 10 days.

22. 




Malabsorption
Malnutrition
Fluid and Electrolyte Shifts
Dehydration,
Acute Renal Failure, Cardiovascular collapse
GI bleeding
Anaemia
Sepsis
Paralytic Ileus
Vomiting, Abdominal
distention

23.  Prodromal
Period: Nausea, vomiting and
burning sensation in the skin within a few
minutes of exposure.
The pt become nervous and confused with loss
of vision, balance and consciousness within
the first hour.

24.  Latent
Period: Lasts up to 12 hours, during
which earlier symptoms disappear.

25.  Manifest
Illness: Symptoms of prodromal
stage return but are more severe.
The person becomes disoriented;
loses muscle coordination;
has difficulty breathing;
may develop convulsive seizures;
loss of equilibrium, ataxia and lethargy;
lapses into coma; and dies.
 Mean Survival Time is 0 to 3 days.

26.  CNS
syndrome is characterized by raised
intracranial pressure, vasculitis and meningitis.

27. The LD50/60 is the dose
of radiation to the whole
body that causes 50%
of irradiated subjects to
die within 60 days.
LD50/60 for human is approx 350 rad
after whole body radiation.

28. As the whole body
radiation dose
increases, the average
time between exposure
and death decreases.

29. 
When only part of the body is irradiated, in
contrast with whole-body irradiation, a higher
dose is required to produce a response.

30. 
Every organ and tissue of the body can be
affected by partial-body irradiation.

31. 
The effect is cell death, leading to total lack of
function for that organ or tissue, or it can be
followed by recovery.

32. 
Examples of local tissues that can be affected
immediately are;
-Skin
-Gonads
-Bone Marrow

33. 
The most commonly affected tissue is the
skin.

Damage to the basal cells results in the earliest
manifestation of radiation injury to the skin.

34. 

Early Transient Erythema: Within a few hours
after single doses in excess of about 200 rad/2
Gy, an early transient erythema might occur in
a well-defined area matching the entrance site
of the X-ray beam.
The area may look much like sunburn.

35. 


This reaction peaks at about 24 hrs and
subsides after approximately 48 hrs.
It is thought to represent an early phase of
inflammation, with hyperemia and increased
permeability of the capillaries resulting from
the release of proteolytic histamine-like
enzymes.
The intensity of the erythema increases with
the dose.

36. 


Main Erythema:A second hyperemic phase,
the main erythematous reaction (main
erythema), begins about 10 days after a dose
of about 600 rad and earlier when doses are
very high.
Its intensity, which is also dose-dependent,
reaches a peak around the 14th day.
The skin becomes warm and edematous.

37. 


The patient may complain of burning,
tenderness, and itching.
The main erythema represents a secondary
inflammatory reaction to damage to the
proliferating cells at the basal cell layer of the
epidermis.
If the dose is not much greater than the
threshold, the erythema fades after 4 weeks.

38. 


Temporary Epilation (hair loss): Epilation (hair
loss) results from depletion of the germinal
layers of hair follicles.
Single doses of 300-600 rad might result in
temporary loss of hair after about 3 weeks.
Re growth occurs after approximately 8-12
weeks.

39. 
Permanent Epilation: Doses in excess of 700
rad may irreversibly damage the hair follicle,
and permanent epilation of the affected
follicles ensues.

40. 

Dry Desquamation: If the radiation dose
exceeds about 800-1200 rad, the main
erythema may progress to dry desquamation
of the skin within 25-30 days.
The erythematous skin is then covered with
scales and flakes of corneum, similar to the
aftereffects of a sunburn.

41. 
Moist Desquamation:If the radiation dose is
even higher i.e 1500-2000 rad, blistering and
sloughing of the superficial skin (moist
desquamation) occurs within 20-28 days.

42. 


Blister Formation: At radiation doses in excess
of about 1500-2500 rad, blister formation
occurs in about 15-25 days.
Ulceration (within skin): At radiation dose
above 2000 rad ulceration within the skin may
occur in 2-3 weeks.
Necrosis (deeper penetration): At radiation
dose of about 2500 rad, necrosis develops in 3
weeks.

43. 
As an example of local tissue effects, human
gonads are particularly sensitive to radiation.

Because these organs control fertility and
heredity, their response to radiation has been
studied extensively.

44. Testicular Dose Effect
(rad)
10-30
Temporary Oligospermia
30-50
100% temporary aspermia from 4-12 months post-exposure. Full
recovery by 48 months.
50-100
100% temporary aspermia from 3-17 months post-exposure.
Full recovery beginning 8-38 months
100-200
100% temporary aspermia from 2-15 months post-exposure. Full
recovery biginning 11-20 months
200-300
100% aspermia beginning at 1-2 months post-exposure. No recovery
observed up to 40 months

45. Ovarian
Dose (rad)
Effect
60
No effect
150
Some risk for ovulatory suppression in women > 40 years of age.
250-500
In women aged 15-40, 60% may suffer permanent ovulatory
suppression; remainder may suffer temporary amenorrhea. In women
> 40 years of age, 100% may have permanent ovulation suppression.
Menopause may be artificially produced.
500-800
In women aged 15-40, 60-70% may suffer permanent ovulatory
suppression; remainder may experience temporary amenorrhea.
>800
100% ovulation suppression.

46.  Haematopoietic
system consists mainly of;
-Lymphocytes
-Granulocytes
-Thrombocytes
-Erythrocytes

48. 
Cytogenetics is the study of the genetics of the
cells, particularly cell chromosomes.

50. • Single hit effects produced by radiation during G1
phase are breakage of a chromatid called
chromatid deletion.
• During S phase both the remaining chromosome
and the deletion are replicated.
• The chromosome aberration visualised at
metaphase consists of a normal looking
chromosome with material missing from the ends
of two sister chromatids and two accentric
fragments without centromere (isochromatids)

51. 


A single chromosome can sustain more
than one hit
In the G1 phase of the cycle ,ring
chromosomes are produced if the two hits
occur on the same chromosome
Dicentrics are produced when adjacent
chromosomes each suffer one hit and
recombine

52. 


These are multihit aberations
These result in no loss of genetic
material,simply rearrangement of genes
Require karyotypic analysis for detection

53. Formation Of Dicentric
Chromosome

54. Formation Of Ring
Chromosome

55. Procedure
Amount of Radiation (mrem)
X-Ray extremity (arm,hand,foot,leg)
1 mrem
X-Ray dental
1 mrem
X-Ray chest
6 mrem
X-Ray pelvis/hip
65 mrem
X-Ray skull/neck
20 mrem
X-Ray barium enema
405 mrem
X-Ray upper GI
245 mrem
CT-head
200 mrem
CT-abdomen
800 mrem
Nuclear medicine (e.g. thyroid scan)
14 mrem