The radiation exposure usually results from diagnostic as well as therapeutic radiation devices.

BIOLOGICAL EFFECTS OF RADIATION Radiation produce changes within the living tissues.

The X-ray beam while traversing the tissue forces the electrons to be ejected from the atomic lattice.

The atom is thus left with surplus +ve electrical charge.

The cells within the tissue come to a state of high chemical reactivity which can initiate biological effects.

DIRECT AND INDIRECT EFFECTS OF RADIATION The DIRECT effect appears due to absorption of energy by the

molecules.

While INDIRECT effects are caused by the products of radiation decomposition [radiolysis] of water and other solutes of the body.

After radiolysis of water in the cells, there is formation of free radicals with unpaired electrons. These free radicals and the H2O2 formed by them are highly reactive and mutagenic.

Since these free radicals possess large amount of energy , they can readily break chemical bounds such as proteins , nucleic acids and lipids.

REACTION SHOWING FORMATION OF FREE RADICALS WITH UNPAIRED ELECTRONS:

DAMAGES PRODUCED BY THE RADIATION IN A DNA MOLECULES ARE:-

Change of base (deamination) , loss of base , H+ bond breakage between chains , single strand break , double strand break , cross-linking with helix and cross-linking with other DNA molecules and protein.

Any alteration in the order is most likely to change the genetic information. These changes may lead to mutations, disturbed normal cell proliferation or other cellular activities.

SUSCEPTIBILITY OF DIFFERENT SPECIES TO THE RADIATION:- Gy = Gray 1 Gray = 1 joule of energy per Kg. of absorbing material. 1 Gray = 100 Rads. LD 50/30 = dose that will kill 50% of the population within a peroid of 30

days.

Species LD 50/30Rabbit 7.5 GyRat 7.1 GyMouse 6.4 GyHamster 6.1 GyGuinea pig 4.5 GyMan 3.0 Gy

Dog 2.5 Gy

EARLY EFFECTS OF RADIATION:-The intensive irradiation of the entire body severely

depletes radiosensitive cells in many organs simultaneously. The combined effect produces “radiation sickness” (acute radiation syndrome).

THE DEGREE OF INJURY TO DIFFERENT TISSUES/ORGANS BY RADIATION:- Lymphoid tissue: within 15 min. after a moderate dose,

there is marked reduction in cell division among lymphocytes & many show necrotic changes.

Bone marrow: the precursors of red blood cells, granulocytes & platelets are radiosensitive. Within a week or two after radiation exposure most of the radiosensitive elements disappear from marrow leaving an aplasticmarrow containing resistant cells & haemorrhages.

Organ of vision: radiation induces inflammatory reactions in the conjuntiva & sclera.

Digestive system: large dose of radiation cause ulcers & erosions in the buccal cavity. Also the pepsinogensecreting cells are adversely affected & parietal cells are functionally disturbed resulting in decreased hydrochloric acid production. The net effect of this is gastric ulcers & haemorrhage. Also large doses of radiation may shorten the villi of intestine & cause injury resulting loss of fluids & decreased absorption and electrolyte imbalance.

Respiratory system: radiation pneumonitis, hyalinisation & fibrosis of the lungs may be observed.

Female reproductive organs: ova & the granulosa cells are highly radiosensitive.

Male reproductive organs: spermatogonia are highly sensitive, at higher dose it may not be able to fertilise ova. If fertilisation occurs, the implantation fails. And the sterility sets in at dose above 2-4Gy.

Urinary system: parenchymal cells, ureters & bladder are radioresistant. The damage to the kidneys occur due to the injury to the blood vessels, the resultant ischemia produces hypertension .

Skin: germinal layer of the epidermis is adversely affected. Higher doses of radiation cause cell death & increased cellular differentiation, these cells migrate to the superficial layer of the skin & desquamate. Normal tight ridged structure of the dermis become loose. Dermatitis & subsequent ulcers develop above dose of 10 Gy.

DELAYED EFFECTS OF RADIATION:-It includes shortening of the life span, leukamia,

malignant tumours & cataract. In man, there may also be induration & atrophy of the skin, connective tissue & lungs.

GENERAL PRINCIPLES OF RADIATION SAFETY:- Increasing the distance between the radiation source and

personnel.

No individuals other than operator and those essential involved in the procedure should be in the X-ray room.

Wherever possible, the animal should not be manually restrained. Chemical restraint combined with physical restraint devices should be employed.

To avoid exposure to the primary beam, a cassette holding device should always be used in large animal radiography.

The operator should be in a shielding booth or behind a shielding screen or atleast 6 feet away from the X-ray source.

No part of the body should be exposed to the primary X-ray beam.

USE OF PROTECTIVE BARRIERS:-

Gloves: The lead gloves should have 0.5mm lead equivalent for voltages upto100kv.

Goggles: Lead goggles should be used during fluoroscopy examinations.

Aprons: Aprons should have a minimum of 0.25mm lead equivalent for voltages upto100kv.

X-ray room & equipment: The X-ray facilities should be located away from the flow of

traffic & public

Warning signs must be displayed near the location of X-ray units.

The wall of the X-ray room should be atleast 22cm thick.

It is essential to check X-ray equipments periodically for possible leakage.

REDUCTION OF EXPOSURE FACTORS: Correct exposure factors must be used in the first

attempt.

The X-ray film should be processed correctly and properly to avoid repetition.

Avoid unnecessary exposures on owners demand.

Use of aluminium filters of atleast 2.5mm thickness to absorb the soft X-ray.

USE OF RADIATION MONITORING DEVICES: Radiation monitoring devices should be worn all the time

by the individuals involved in radiographic work.

Ideally, one film badge should be worn at the belt level to monitor whole body exposure and the other at the neckline to estimate exposure to the skin of the head & neck and eyes.

At periodic intervals these monitoring devices should be sent to the research center(Division of Radiation Safety, Bhabha Atomic Research Center, Trombay, Bombay) for calculating radiation dose.

MONITORING DEVICE:

MAXIMUM PERMISSIBLE DOSE FOR VET. & STAFF:BODY PART ONE WEEK ONE YEARWhole body, 100m rem 5,000m rem

Gonads, bone marrow,

Lens of the eye

Hands forearms 1,500m rem 75,000m rem

& feet .

Where, rem = rad*quality factor.

Made by: Girjesh Upmanyu