Radiation as a friend or foe

RADIATION as a friend or

foe• ASHISH RANGHANI

• PG PART 2

• GDCH, AHMEDABAD

UNDER GUIDANCE OF

DR. J.S SHAH

PROFESSOR AND HEAD

ORAL MEDICINE AND RADIOLOGY

GDCH

DATE- 10/02/2017

CONTENTS• Introduction

• Radiation and Types of Radiation

• Sources of Radiation

• Benefits And Risks of Radiation

• Uses of Electromagnetic waves

• Uses Of Radiation In Dentistry

• Radiotherapy

• Nuclear Medicine

• Types Of Radiation Effects

• Deterministic Effects

• Stochastic Effects

• Short Term Effects

• Long Term Effects

• In-utero Effects

• Radiation Effect On Cells

• General Effect Of Radiation

• Radiation Effect On Oral Cavity

DISCOVERY OF X-RADIATION

• Wilhelm Conrad Roentgen on November 8, 1895 discovered x-rays

One of roentgen 1st experiments in 1895 was a film of his wife Bertha's hand with a ring on her finger

• The first use of X rays was in medical diagnosis, within six months of their discovery in 1895

• So a benefit from the use of radiation was established very early on, but equally some of the potential dangers of radiation became apparent in the doctors who overexposed themselves to X rays in the early 1900s.

What is radiation?....1,2

• Radiation refers to the propagation of energy through space or a medium

• Ionizing radiation includes Gamma rays, X rays and the radiation from radioactive materials.

• Non-ionizing radiation includes ultraviolet light, radiant heat, radio waves and microwaves

Electromagnetic Spectrum1,2

• Gamma rays

• X – rays

• Ultraviolet

• Visible light

• Infra-red

• Microwaves

• Radio waves

Highest frequency

Shortest wavelength

Lowest frequency, Longest wavelength

Electromagnetic Waves

Low HighENERGY

Radio waves

Microwaves

Radar

Infrared

Visible light

Ultra-violet

X-ray

Gamma-ray

Non-ionizing radiation

Ionizing radiation

Sources of ionizing radiation

Natural sources

• Cosmic rays

• Gamma rays from the Earth

• Radon decay products in the air

• Various radionuclides found naturally in food and drink

Artificial sources

• Medical X rays

• Fallout from the testing of nuclear weapons in the atmosphere

• Discharges of radioactive waste from the nuclear industry

• Industrial gamma rays

Radiation, people and environment, international atomic energy agency

source Dose (msv)

Nuclear industryUranium miningFuel fabricationNuclear reactorsReprocessingMedical usesRadiologyDentistryNuclear medicineRadiotherapyIndustrial sourcesIrradiationRadiographyIsotope productionLuminizing

4.51.01.41.5

0.50.060.80.6

0.11.61.90.4

The average dose overall to occupationally exposed workers from artificial sources is less than 1 mSv in a year


Benefits and risks

• The discovery of ionizing radiation and radioactive materials has led to dramatic advances in medical diagnosis and treatment, and they are used for a wide range of procedures in industry, agriculture, and research.

• They can be harmful to human beings, and people must be protected from unnecessary or excessive exposures.


RADIATION as a friend

USES OF GAMMA RAYS 6

• Gamma rays kill microbes, and are used to sterilise food so that it will keep fresh for longer. This is known as "irradiated" food

Gamma rays are also used to sterilise medical equipmentSterilization of plastic syringes, hypodermic needles, scalpels, surgical blades and adhesive dressings & sutures

Gamma rays are the highest energy electromagnetic wave.

Gamma sterilization of human tissue grafts

In industry, radioactive "tracer" substances can be put into pipes and machinery, then we can detect where the substances go

Study the nucleus in atoms

Ultraviolet Waves 6

• UV Light that is at a higher frequency and energy than violet light

• The main source of ultra-violet radiation is sunlight

• UV light can kill micro-organisms

• Ultra-violet radiation is used in hospitals to sterilize the surgical instruments and operating theatres as it kills bacteria and viruses

• Too much exposure can cause:

• Sunburn and skin cancer

• As it damages cell DNA

Infra-red waves 6

• Infrared waves are heat waves

• Night vision goggles detect infrared waves and allow the user to see the movement of objects in the dark.

• Many TV remotes use infrared

• It shows a thermo-detector which is placed outside hospitals/airport to identify the warm and cool parts of a person by analyzing infra-red radiation emitted from the person’s body. And through this we can see if someone is having a fever

• For navigation through fog & haze as it is less easily scattered compared to visible light

Microwaves 6

• One of their most common uses is in microwave ovens.

• Other uses of microwaves: • Radar communication • Analysis of fine details of

molecular and atomic structure

• Telephone communication (mobile phones, etc)

Why are Radio Waves Important? 6

The biggest use for radio waves are communication, such as phones, texts, emails and instant messaging.

Radio waves, that we use every day. Such as-

• Television

• Wireless networks

• Mobile phones

• GPS systems

• Police radios

• Radio controlled toys

Dental uses of radiation

• Ionizing radiation has two very different uses in dentistry — for diagnosis and therapy

• X-rays plays a vital role in the practice of dentistry

1. As part of routine examination,

2. Diagnostic purpose,

3. Treatment planning or for follow-up evaluation of the patients

• Much higher doses are required to treat malignant diseases in combination with other forms of treatment.

• Oral Radiology-Principles and Interpretation, White and pharoh-6th Edition

Diagnostic radiology

• Radiographs are important in the routine investigation of dental caries and its sequelae,

• Evaluation of periodontal diseases,

• Identification of osseous pathologies such as cysts and tumors

• Evaluation of traumatic injuries involving the jaws and facial bones

• Radiographs are also useful in the evaluation of growth and development

• From the foregoing it is very clear that radiographs are sometimes referred to as the main diagnostic aids of the clinician


DENTAL CARIES• Intraoral radiography can reveal caries

lesions that otherwise might go undetected, especially in case of proximal lesions

• Various radiographs for caries detection:

• Bitewing: Aids in detecting caries in interproximal areas and distal ends of premolars and molars, and caries at CE junction.

• Periapical: Aids in detecting gross carious lesions, root caries and changes in the apical and inter radicular bone due to caries.

• OPG: Useful to examine a case with multiple carious teeth or rampant caries.

Radiographic Assessment of Periodontal Conditions

Radiographs are especially helpful in the evaluation of the following features:

• Amount of bone present

• Condition of the alveolar crests

• Bone loss in the furcation areas

• Width of the periodontal ligament space

• Poorly contoured or overextended restorations

• Root length and morphology and the crown-to-root ratio

• Open interproximal contacts, which may be sites for food impaction

Inflammatory lesions of the jaws

• Periapical inflammatory lesions associated with a mandibular first molar

Occlusal film demonstrates chronic phase of osteomyelitis

Panoramic film reveals large sequestra (black arrow) and a periosteal reaction at theinferior border of the mandible in a case ofchronic osteomyelitis

Cysts of Jaw

Dentigerous cyst that is expanding distally from the involved third molar

Radicular Cyst

Benign Tumors of the Jaws

• Radiologic examination will provide information regarding the extent of the lesion, and sometimes the characteristics are so specific that a preliminary diagnosis of the type of benign tumor can be made

Malignant Diseases of the Jaws• There are various diagnostic imaging modalities available to aid in

the diagnosis.

• Intraoral radiographs still provide the best image resolution and are able to reveal malignant changes

• Panoramic radiographs provide an overall assessment of the maxillofacial osseous structures and can reveal relevant changes such as destruction of the boundaries of the maxillary sinus.

• Computed tomography (CT) images can provide a superior three-dimensional analysis of the osseous structures and better determine the position and extent of the tumor

• Positron emission tomographic (PET) scans, a technique capable of detecting abnormal cellular metabolic activity associated with malignant tumors, have been fused with CT images to provide an accurate location of the tumor in preparation for radiotherapy.

• Magnetic resonance imaging (MRI) has provided three-dimensional soft tissue images of tumors and information regarding perineuralspread and involvement of lymph nodes

• The purposes of TMJ imaging are to evaluate the integrity and relationships of the hard and soft tissues, confirm the extent or stage of progression of known disease, and evaluate the effects of treatment

Trauma to Teeth and Facial Structures

• Radiologic examination is essential for evaluating trauma to the teeth and jaws.

• The presence, location, and orientation of fracture planes and fragments can be determined, and the involvement of nearby vital anatomic structures can be assessed.

• Furthermore, foreign objects that have become embedded within the soft tissues as a result of trauma can be detected.

SIALOGRAPHY

• Sialography is the radiographic visualization of the salivary gland following retrograde instillation of soluble contrast material into the ducts before imaging with plain films, fluoroscopy, panoramic radiography, CT

• Iodine which is used as a contrast media

CONTRAST MEDIA

Two types of contrast media are presently available for contrast studiesWater soluble- SinografinOil based- Ethiodol

Arthrography

• Arthrography is a technique in which an indirect image of the disk is obtained by injecting a radiopaque contrast agent into the joint spaces under fluoroscopic guidance.

• Magnetic resonance imaging (MRI) has replaced arthrography and is now the imaging technique of choice for the soft tissues of the TMJ

SCINTIGRAPHY (Nuclear medicine)

• Scintigraphy with technetium (Tc) 99m is a dynamic and minimally invasive diagnostic test to assess salivary gland function and to determine abnormalities in gland uptake and excretion

• Technetium is a pure gamma ray– emitting radionuclide that is taken up by the salivary glands

• It has also been used to aid in the diagnosis of ductal obstruction, sialolithiasis, gland aplasia and Sjögren’ssyndrome

• Salivary imaging is performed following the injection of Tc 99m pertechnetate

• The uptake, concentration, and excretion of the pertechnetate by the major salivary glands and other organs is imaged with a gamma detector that records both the number and the location of gamma particles released in a given field during a period of time

• A special detector called a gamma camera is used to observe how the organs or tissue behave or how quickly the radionuclide moves

Scintigraphy, 99m Tc-pertechnetatescan of the salivary glands (right and left anterior oblique views) demonstrates increased uptake of radioisotope in the right parotid gland (black arrowhead)

Scintigram taken after administrationof a sialogog (lemon juice) demonstratesretention of isotope in right parotid gland (white arrowheads). This is a typical presentation of salivary stasis

OBJECT LOCALIZATION

Two Dimensional Techniques

• Tube Shift Technique / Clark`s Technique

• Occlusal Radiography

• Right Angle Technique / Miller`s Technique

Three Dimensional Techniques• Computed Tomography Scan (CT)• CBCT ( Cone Beam Computed Tomography)

Frenny karjodkar, Text book of oral radiology. 2nd edition.

Methods Used to Localize Objects

Interpretation

When the dental structure or object seen in the second radiograph appears to have moved in the same direction as the shift of the position indicating device (PID), the structure or the object in question is said to be positioned lingually. But, if the object appears to have moved in a direction opposite to the shift of the PID, then the object in question is said to be positioned buccally.

SLOB rule: Same side Lingual - Opposite side Buccal.


Right angle technique

• Here two projections are taken at right angles to each other, which helps to localize an object in the maxilla or mandible.


Method

• A periapical radiograph is taken to show the position of the object superio-inferiorly and anteroposteriorly.

• Next, an occlusal radiograph is taken which will show the object’s buccolingual and anteroposterior relationship.

A. The object appears to be located in bone on the periapical radiograph.

B. The occlusal radiograph reveals that the object is actually located in the soft tissue lingual to the mandible


Occlusal Radiography• Locate roots and

supernumerary, unerupted, and impacted teeth

• Stones in the ducts of sublingual and submandibular glands

• To determine the medial and lateral extent of disease

• Fractures of the mandible and maxilla

ASSESSMENT OF FOLLOWING ANATOMIC PARAMETERS ON RADIOGRAPHS

• Height of the alveolar bone

• Buccolingual dimension of the ridge at the implant site

• Determine bone quality

• Determine long axis of alveolar bone

• Determine Jaw boundaries

• Pathology detection

• Position of inferior alveolar canal

Dental Implants

• periapical radiograph of two successful dental implants

• The close apposition of the bone to the surface of each implant.

Periapical radiograph of bone loss around a root-form dental implant (thin radiolucent band surrounding the implant), indicatingfailure of osseous integration.

Periapical view of a fractured endosseousimplant

What is Radiotherapy ?

• It is the medical use of ionizing radiation, generally as part of cancer treatment to control or kill malignant cells by destroying reproductive integrity of the malignant cells.

• Radiotherapy can be given as

1. External radiotherapy (Teletherapy)

2. Internal radiotherapy (Brachytherapy)

Head and Neck Cancer Treatment, RadiologyInfo.org Reviewed: Mar-21-2016

• Head and neck cancer represents the 6th most common malignancy & accounts for approx. 6% of new cancer cases annually worldwide.

• The first patient was treated with radiation in 1896, two months after the discovery of the X-ray.


• Patients with early-stage head and neck cancers are treated with one modality—either radiation therapy or surgery.

• Patients who have more extensive cancers are often treated with chemotherapy and radiation therapy.

• Sometimes, patients are treated with surgery followed by postoperative radiation therapy and chemotherapy


Intensity-modulated radiation therapy (IMRT)

• An advanced mode of high-precision radiotherapy that utilizes computer-controlled x-ray accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor.

• The radiation dose is designed to confirm to the three-dimensional (3-D) shape of the tumor by modulating—or controlling—the intensity of the radiation beam to focus a higher radiation dose to the tumor while minimizing radiation exposure to healthy cells


External beam therapy (EBT)• A method for delivering a beam of high-energy x-rays to

the location of the tumor.

• The beam is generated outside the patient usually by a linear accelerator targeted at the tumor site.

• These x-rays can destroy the cancer cells and careful treatment planning allows the surrounding normal tissues to be spared.

• No radioactive sources are placed inside the patient's body.


Other Uses of X rays-• Examination of Baggage in Airports :

The use of X-rays in airports to examine for the presence of dangerous weapons or bombs is a routine practice

• Industrial Use• X-rays reveal structural information

about the material• It can therefore be used to detect

structural deficits or cracks in metal objects that are likely to be missed by the human eye

Study the crystal structure of

crystalline substances

Examination and analysis of paintings, where studies can reveal such details as the age of a painting and underlying brushstroke techniques that help to identify or verify the artist

Health Concerns

• The widespread use of x-rays led to serious injuries.

• Some early experimenters did tie x-ray exposure and skin burns together.

How do X-rays cause damage?

• Two main mechanisms are thought to be responsible:

• Direct damage to specific targets within the cell

• Indirect damage to the cell as a result of the ionization

of water or other molecules within the cell.

• The first warning of possible adverse effects of x-rays came from Thomas Edison, William J Morton, and Nikola Tesla who each reported eye irritations from experimentation with x-rays and fluorescent substances.

Deterministic effects

• Nonstochastic effects (deterministic effects) are somatic effects that have a threshold and that increase in severity with increasing absorbed dose.

• Examples of nonstochastic effects include erythema, loss of hair, cataract formation, and decreased fertility.

• Compared with stochastic effects, deterministic effects require larger radiation doses to cause serious impairment of health.

Eric Whaites.Essentials of Dental Radiography and Radiology.4th edition

Stochastic effects

• Their development is random and depends on the laws of chance or probability. Examples of somatic stochastic effects include leukaemiaand certain tumours.

• These damaging effects may be induced when the body is exposed to any dose of radiation.

• There is no threshold dose, and that every exposure to ionizing radiation carries with the possibility of inducing a stochastic effect.


Short-Term Effects

• Following the latent period, effects that are seen within minutes, days, or weeks are termed short-term effects. Short-term effects are associated with large amounts of radiation absorbed in a short time (e.g., exposure to a nuclear accident or the atomic bomb).

• Acute radiation syndrome (ARS) is a short-term effect and includes nausea, vomiting, diarrhea, hair loss, and hemorrhage.

• Short-term effects are not applicable to dentistry.


Long-term effects

• Effects that appear after years, decades, or generations are termed long-term effects.

• Long-term effects are associated with small amounts of radiation absorbed repeatedly over a long period.

• Repeated low levels of radiation exposure are linked to the induction of cancer, birth abnormalities, and genetic defects.

Eric Whaites. Essentials of Dental Radiography and Radiology.4th edition

BIOLOGICAL EFFECTSEFFECT ON CELLS

1.DNA

2.CYTOPLASM

3.NUCLEUS

4.CHROMOSOMES

GENERAL EFFECT OF RADIATION

1.SKIN

2.BONE MARROW

3.Testicles

4.GONADAL

5.EYE

EFFECT ON ORAL TISSUES1.ORAL MUCOSA-MUCOSITIS2.TASTE BUDS 3.SALVARY GLANDS-4.TEETH5. RADIATION CARIES6.BONES7. MUSCULATURE

EFFECT ON WHOLE BODY1.ACUTE RADIATION SYNDROME

CYTOPLASM

Increased permeability of plasma membrane to sodium and potassium ions.

Swelling and disorganization of mitochondria.

Focal cytoplasmic necrosis.

NUCLEUS

• Nucleus is more radiosesitive than the cytoplasm

• Inhibition of cell division

Chromosome Aberrations

If radiation exposure occurs after DNA synthesis (I,e G2 or late s)only one arm of the effected chromosome is broken

If radiation occurs before DNA synthesis (G1 or early S) both arms are effected

The survivors of the atomic bombings of Hiroshima and Nagasaki have demonstrated chromosome aberrations in circulating lymphocytes more than two decades after the radiation exposure.

GENERAL EFFECT OF RADIATION

SKIN

Physical foundations of radiology, Otto glasser, Third edition

Doses up to 1000 R or so given within a few days leave little or no permanent mark

Two or three times this amount may leave permanent tanning and some superficial blood vessel damage

Hair loss may be permanent and some sweat gland destroyed

Hair loss

Skin: The reaction of the skin to radiation may be categorized as:

• Essentials of Oral and maxillofacial radiology, Freny R Karjodkar

Early or acute signs

• Increased susceptibility to chapping

• Intolerance to surgical scrub

• Blunting and leveling of finger ridges

• Brittleness and ridging of finger nails

Late or chronic signs:

• Loosening of hair and epilation

• Dryness and atrophy of skin, due to destruction of the sweat glands

• Progressive pigmentation, telangiectasis and keratosis

• Indolent type of ulcerations

• Possibility of malignant changes in tissue


HEMATOPOIETIC INJURY

The usual picture of blood reaction to radiation is leukopenia, which in some cases may progress to leukemia, anemia, lymphopenia, and loss of specific immune response

The primary somatic risk from dental radiography is leukemia induction, especially in young individuals.

This is because at birth all bones contain only red bone marrow. younger individuals are at a greater risk of developing leukemia.

Eyes

• Epilation of eyelashes

• Inflammation, fibrosis and decreased flexibility

of the eyelid

• Damage to the lacrimal glands, leading to

dryness

• Ulceration of the cornea

• Initiation of cataract formation from the

periphery towards the center


Testicles

• Permanent sterility may be produced by acute dose of 500 r to the reproductive organs

• Suppression of germinal activity

• Alteration in fertility


ORAL MUCOUS MEMBRANE

• The oral mucous membrane contains a basal layer composed of rapidly dividing, radiosensitive stem cells.

• Near the end of the second week of therapy, as some of these cells die, the mucous membranes begin to show areas of redness and inflammation (mucositis).


• As then therapy continues, the irradiated mucous membrane begins to separate from the underlying connective tissue, with the formation of a white to yellow pseudomembrane (the desquamated epithelial layer).

• At the end of therapy the mucositis is usually most severe, discomfort is at a maximum, and food intake is difficult.


Taste Buds

• Taste buds are sensitive to radiation. • Patients often notice a loss of taste

acuity during the second or third week of radiotherapy.

• Bitter and acid flavors are more severely affected when the posterior two thirds of the tongue is irradiated and salt and sweet when the anterior third of the tongue is irradiated.

• Taste loss is reversible and recovery takes 60 to 120 days


SALIVARY GLANDS

• The parenchymal component of the gland is sensitive to radiation. The gland demonstrates progressive fibrosis adiposis, loss of fine vasculature and simultaneous parenchymal degeneration.

• Parotid gland is more radio sensitive than the other glands


• There is marked decrease in the salivary flow.

• The composition of saliva is affected.

• There is increased concentration of sodium,chloride, calcium, magnesium ions and proteins.

• The saliva loses its lubricating properties.

• The mouth becomes dry and tender due to xerostomia.

• The pH of saliva is decreased which may initiate decalcification of enamel.

• A compensatory hypertrophy of the salivary gland may take place and the xerostomia may subside after six to twelve months after therapy.


Teeth

Exposure

Before calcification completion - tooth bud may be damaged

• At later stage of development - may arrest growth


Pulp shows decrease in vascular elements, with accompanying fibrosis and atrophyPulpal response to infection, trauma, and various dental procedures appears compromised

• Children receiving radiation therapy to the jaws may show defects in the permanent dentition such as retarded root development, dwarfed teeth, or failure to form one or more teeth

• Eruptive mechanism of teeth is relatively radiation resistant

• Adult teeth are resistant to the direct effects of radiation exposure

• Radiation has no direct effect on the crystalline structure of enamel, dentin, or cementum, and radiation does not increase their solubility.

RADIATION CARIES

• Radiation caries is a rampant form of dental decay that may occur in individuals who receive a course of radiotherapy that includes exposure of the salivary glands

• Patients receiving radiation therapy to oral structures have increases in Streptococcus mutans,Lactobacillus, and Candida .

• Caries results from changes in the salivary glands and saliva, including

• Reduced flow,

• Decreased pH,

• Reduced buffering capacity,

• Increased viscosity, and altered flora.


TYPES• Clinically, three types of radiation caries exist.


• The most common is widespread superficial lesions attacking buccal, occlusal, incisal, and palatal surfaces

• Another type involves primarily the cementum and dentin in the cervical region.

• These lesions may progress around the teeth circumferentially and result in loss of the crown

• A final type appears as a dark pigmentation of the entire crown. The incisal edges may be markedly worn

Radiation has a rapid effect on the salivary glands• In the first two weeks,

with a cumulative RT dose of 20 Gy, around 80% of salivary function is lost

• Above 58 Gy there was a complete loss of salivary gland function

Bone


Radiation acts by destroying osteoblasts and to a lesser extent

osteoclasts

Subsequent to irradiation, Normal marrow may be replaced with fatty marrow and fibrous connective

tissue.

The marrow tissue becomes hypo vascular, hypoxic, and hypo cellular

• Osteoradionecrosis is the most serious clinical complication that occurs in bone after irradiation.

• The decreased vascularity of the mandible renders it easily infected by microorganisms from the oral cavity

• This bone infection may result from radiation-induced breakdown of the oral mucous membrane, by tooth extraction, a periodontal lesion, or from radiation caries

• This infection may cause a non healing wound in irradiated bone

• It is more common in the mandible than in the maxilla, probably because of the richer vascular supply to the maxilla and the fact that the mandible is more frequently irradiated

• The higher the radiation dose absorbed by the bone, the greater the risk for osteoradionecrosis.


Musculature

• Restriction in mouth opening usually starts about 2 months after radiotherapy is completed and progresses thereafter

• An exercise program may be helpful in increasing opening distance.


Radiation may causes inflammation and fibrosis

resulting in contracture and trismus in the muscles of mastication

Usually the masseter or pterygoid muscles are involved.

EFFECTS IN WHOLE BODY

80

ACUTE RADIATION SYNDROME

Acute Radiation Syndrome (ARS) is an acute illness caused by irradiation of the entire body (or most of the body) by a high dose of penetrating radiation in a very short period of

time (usually a matter of minutes)


Acute Radiation Syndrome


DOSE (Gy) MANIFESTATION

1 to 2 Prodromal symptoms

2 to 4 Mild hematopoietic symptoms

4 to 7 Severe hematopoietic symptoms

7 to 15 Gastrointestinal symptoms

>50 Cardiovascular and central nervous system symptoms

STAGES OF ARS

• Prodromal stage (N-V-D stage): The classic symptoms for this stage are nausea, vomiting, as well as anorexia and possibly diarrhea (depending on dose), which occur from minutes to days following exposure. The symptoms may last (episodically) for minutes up to several days

• Latent stage: In this stage, the patient looks and feels generally healthy for a few hours or even up to a few weeks

• Manifest illness stage: In this stage the symptoms depend on the specific syndrome and last from hours up to several months

• Recovery or death: Most patients who do not recover will die within several months of exposure. The recovery process lasts from several weeks up to two years


Bone marrow (hemopoietic) syndrome:

• (2 to7 Gy) Here severe damage may be caused to the circulatory system.

• The bone marrow being radiosensitive, results in fall in the number of granulocytes, platelets and erythrocytes.

• Granulocytes, with short lives in circulation, fall off in a few days, whereas red blood cells, with long lives in circulation, fall off slowly

• Clinically this is manifested as lymphopenia, granulocytopenia and hemorrhage due to thrombocytopenia and anemia due to depletion of the erythrocytes.


GASTROINTESTINAL SYNDROME• The gastrointestinal syndrome is caused by whole-body

exposures in the range of 7 to 15 Gy, which causes extensive damage to the gastrointestinal system in addition to the hematopoietic damage described previously

• Because of the denuded mucosal surface, there is loss of plasma and electrolytes, loss of efficient intestinal absorption, and ulceration of the mucosal lining with hemorrhaging into the intestines

• These changes are responsible for the diarrhea, dehydration, and loss of weight

• Endogenous intestinal bacteria readily invade the denuded surface, producing septicemia


• At about the time that developing damage to the gastrointestinal system reaches a maximum, the effect of bone marrow depression is beginning to be manifested.

• The result is a marked lowering of the body ’s defenseagainst bacterial infection and a decrease in effectiveness of the clotting mechanism.

• The combined effects of damage to these hematopoietic and gastrointestinal stem cell systems cause death within 2 weeks from fluid and electrolyte loss, infection, and possibly nutritional impairment.

• Thirty of the firefighters at the accident site at Chernobyl, Ukraine, died in the first few months of the hematopoietic or gastrointestinal syndrome

Cardiovascular and central nervous system syndrome

• (More than 50 Gy): This produces death within one or two days.

• Individuals show incordination, disorientation and convulsions suggestive of extensive damage to the nervous system.


Effects on the unborn child

• Embryos and fetuses are considerably more radio-sensitive than adults because most embryonic cells are relatively undifferentiated and rapidly mitotic

• The developing fetus is particularly sensitive to the effects of radiation, especially during the period of organogenesis (2–9 weeks after conception).

• These effects are deterministic in nature

• Exposures in the range of 2 to 3 Gy during the first few days after conception are thought to cause undetectable death of the embryo.

• The period of maximal sensitivity of the brain is 8 to 15 weeks after conception.


• The major problems are:

1.Congenital abnormalities or death associated with large doses of radiation

2.Mental retardation associated with low doses of radiation.

There is also an Increased risk for childhood cancer, (leukemia and solid tumors), after irradiation in utero.

X-ray examination Estimated riskof fatal cancer

Dental intraoral (x 2) 1 in 2 000 000

Dental panoramic tomograph

1 in 2 000 000

Skull (PA) 1 in 670 000

Skull (Lat) 1 in 2 000 000

Chest (PA) 1 in 1 000 000

CT chest 1 in 2500

CT head 1 in 10000

A broad estimate of the magnitude of the risk of developing a fatal radiation-induced cancer, from various X-ray examinations, was published in theUK in 1999 by the NRPB in their booklet

Guidelines on Patient Dose to Promote the Optimisation of Protection for Diagnostic Medical Exposures, 1999

Chernobyl accident

• Despite all the safety measures applied in using radiation and radioactive materials, accidents can happen

• An explosion in a nuclear reactor at the Chernobyl nuclear power plant on 26 April 1986 caused the release of substantial quantities of radionuclides during a period of ten days

• As the contaminated air spread throughout Europe and beyond, local weather conditions largely determined


• The accident had a catastrophic effect locally and high radiation exposures of emergency workers led to the deaths of 31 people.

• The firemen received large external doses from deposited radionuclides, between 3 and 16 Sv, and contamination on their skin lead to severe erythema

• A further 209 people were hospitalized of whom 106 were diagnosed as having acute radiation sickness

• The most significant radionuclides were iodine-131, caesium-134 and caesium-137

• Between 1945 and 1999 there were some 140 serious reported accidents involving excessive radiation exposure in the nuclear industry, military facilities, hospitals, research facilities, and general industry. The most frequent occurrence (about 70 in total) is the mishandling or misappropriation of sealed sources used for radiography in industry and radiotherapy in hospitals


REFERENCES

1.White and pharoh-Oral Radiology-Principles and Interpretation 6th

2.Essentials of Oral and maxillofacial radiology, Freny R Karjodkar

3.Eric Whaites.Essentials of Dental Radiography and Radiology.4th edition.

4. Physical foundations of radiology, Otto glasser, Third edition

5. Head and Neck Cancer Treatment, RadiologyInfo.org Reviewed: Mar-21-2016

6. Radiation, people and environment, international atomic energy agency

Thank you

Radiation as a friend or foe

Health & Medicine

Transcript of Radiation as a friend or foe