MFCM095: Hazards of Common Radiographic Techniques to Staff and Patients.pdf

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BANGALORE-560 001
BACKGROUND PAPER NO.7
DR. SHAM ASHTEKAR
DINDORI, NASIK 422 202

XVI ANNUAL MFC MEET ;

HAZARDS OF COMMON RADIOGRAPHIC TECHNIQUES TO STAFF AND PATIENTS

INTRODUCTION

Diagnostic rediographic techniques constitute an extremely
important tool in the hands of the physician today all over
world.

Exposure r:ates as high as 868 exposures per year per

thousand population are prevalent in European countries(1).

In developing countries the rate is quite less
these.

as compared to

However it also constitutes major source of rediation

to mankind only next to N weapons and Nuclear Energy processors.
Precisely therefore it'has to be used with a lot of discretion

and economy since radiation has proved to be a major determinnat of cancers and genetic mutations.

The Xray Units in India are mainly operated at two levels,
first is the Xray Units in major hospitals and consultant

The

Radiologists processing a good number of exposures even 100 a

day-required for a range of diagnostic needs.

Such installations

normally use hish output low time exposure1 machines with a
reasonable saftey organisation. The Second level is that of the
taluka level nursing homes/clinics, some urban 'Bazar1 X ray

clinics that operate' low output longer time exposure' machines
with poor saftey organisation.

The general consensus among experts .indicates that, properly
used, the usual diagnostic X ray prosedures do not cause much

harm to the patients/staff considering the contribution they
offer in patient managment.

But badly organised units can harm

the population in the long run.
some issues in this context.
2.

This paper attempts to outline

THE BIOLOGIC EFFECTS OF X RAYS :

The biologic effects of X ray can be summed up as follows s
i)

There is no' tolerance level’for exposure since even small

doses are biologically not' lostl

As far as biological effects

are concerned 'there is no 'adjustment dot'- ' for radiation.
ii) The probability of occurrence of X ray hazards shows a
linear relationship with exposure. More the dose proportion­

ately, more shall be the occurrence of hazrdous effects.

iii) There is a sigmoid relationship between the exposure does
and the severity of the effects. Thus after an initial threshhold and then steady rise of dose.-severity curve,there is a

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1

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steep rise for subsequent dosages till there is a platau of
steady rise again. The last segment of staedy rise is accou­

nted for by selective elimination of affected persons due to

deaths.
iv) There are some somatic'certainty effects' like radiation
erythema, bone marrow fibrosis,radiation ulcers, skin cancerh

etc. which almost certainly occur after a latency perioel,
provided the dose is more than 10 and 100 rads for whole body

and partial body irradiation respectively.

sigmoid dose-effect relationship.

These show a

In the early days of radid­

iagnosis these were frequent occurences beacuse of poor
protection measures. In almost all cases of such effects,the
event can be traced back to some past exposure. These effects

are more severe with time concentrated dose as a compared to a

time spreaded exposure..

v)
There are some somatic st.'.ochastic effects like organ
cancers and leukemias that show a linear relation as for dose
effect. These effects occur at their respective ageprofiles,
only much more commonly in the exposed population.

vi) The genetic effects are always stochastic and there are
two modalities. Firstjthe effect is mostly lethal to gonadal
cells so that there is a lower brith rate in the exposed popu­

lation.

Second-less frequently there are chromosome abnormal­

ities and mutations.

Mutations are recessive that show up in

later generations if the other partner also carries recessive

trait.

Such chances increase with accumufotion of abnormal

genes in the total genetic pool of the child bearing (Prosp­
ective or current) age groups.

abnormalities do not

Older parents carrying such

after the gene pool.

The somatic

expression of these abnormalities can be very severe and in

this sense X rays are a major threat to genetic constitution
'Y
of the population if effective gonad protection is not offered.
Children/persons below 18 years are 10 times prone to such
abnormalities as compared to the adults.(1)

vii) These biologic risks to patients have to be weighed against
the possible benifits of radiodiagnosis and those on the staff
compared to level of occupational hazards in other professions

to get a balanced picture of the risk profile.

3.

THE DOSE IN RADIODIAGNOSIS.

The dose of the exposure is a function of many factors. The
output of the machine is Milliampere, the time duration of
exposure, the distance of the subject from the Xray Tube all
decide the dose of the exposure.

3

Maximum Permissible Dose(MPD) is defined as : The Permissible
dose for an individual is that dose, accumulated over a long
period of time or resulting from a single exposure, which, in
.

the light of the present knowledge, carries' a ’negligible pro­

bability of severe somatic or gentic injuries; furthermore it
’ is such.a.dose that any effects that ensue more frequently are
of a minor nature that would not be considered unacceptable by
the exposed individual and by the competent medical authorities

(1).
It is estimated that in the last two decades in most countries
75-96% of the exposed staff did not receive more than one tenth

of the MPD.

It is also estimated that in no country the genet­

ically significant dose from this source is more than 1% of the
natural nackground radiation.

However the same MPD level can

not be accepted for children since children are about 10 times
susceptible as compared to adults.(1)

4.

THE

ESTIMATION OF CANCER RISK :

There can be no generalisation about cancer risk from X rays.

Much depends upon the dose,the organs

receiving Xrays,the age

of the subject, positioning of subjects and some other factors.

When a subject is exposed-w'hole body-all organs may get irradi­
ation but the risk is not- similar in all the organs. Generally
extremeties are not sensitive and so also skin,bones and thyroid.

As for dose every procedure involves, different dosages.

Chest

radiographs, extremities and thinner parts/ need much less

exposure than abdomen.
than thin ones.

Thickset individuals need more exposure

AnAP chest view harms the bone marrow much more

than a PA view.

A 1 repaast1 doubles the dose and the risk thereof . Exposure of abdomen in an 18. year subject causes cancers
with manyfold frequency as compared to the same procedure in a

60 year old subject-

An elderly person can take much more dose

without cancer risk since there is relatively shorter survival
period for cancers to develop. Therefore multiple radiographs
for diagnosis of gastric ulcers,renal stones,barioum shadows

involve much less risk than a single exposure in a child.. Risk
changes to more than 10,000 times from one situation to another
sitution (2).
The variation in risk due to these factors is quite sizeable
as will be evident from the risk tables (2) given in the appendix

5.

GONADAL DOSE s

Almost every exposure,save dental or similarly skin close
exposures and well limited (collimated) exposures, result in

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some irradiation of the gonads'.

Appendix II shows the Gonadal

dose grouping and also bone marrow dose grouping(l).

This will

underline the need to lead-shield the gonads whenever possible.
6.

THE RISK FACTORS, THE X RAY MACHINE,DESIGN FACTORS,SHIELDING;

i)

The useful beam size ;

The Xray beam directed towards.the

target/film is known as the useful (Primary) beam. The useful
beamsize depends ,upon the design of the Xray Tube head outpet

and the distance of the subject from the tube head.

Most often

unless optical devices are used to show the field of the beam?-the

useful beam irradiated regions that surround the target region.

This can be avoided by optical devices and adjusting the distance
factor.

Radiation other than
the useful beam is known as the back/scattercd radiation. This
ii)

Back radiation/scattered radiation ?

mainly affect the staff. Adquate distancing of the operators,
control panel, lead apron are all necessary to avoid the exposure
to- this radiation.

Back radiation can also affect the patient

and suiatable position is necessary to minimise this dose(l).

iii) Fluroscopy : The machine output in fluroscopy operation is
very low but time factor offsets this advantage. Moreover, staff
doing fluroscopy is necessariely exposed to the useful beam in a

routine manner. Proper darkroom facility, timer-indicators,
apring switch,lead flaps,lead ’gloves,proper dark adaptation and

good training are all necessary to minimise dose.
iv)

Calculated Vs actual dose exposure ;

It is possible to

calculate individual exposure doses as per he readings of MA,Kv,
time in secs. But actual doses are found to vary to about 0.1

to r .4t times the calculated dose due to equipment dactors. This

is known to happen even in..best of units (2).

The real way of

estimating actual exposure dose is to use special instruments
like Gigar counters, crystal dosimeters, ionisation chambcs etc.

which is usually not done in India though 3ARC can help do this
on request. It is estimated that much smallar doses than are
actually delivered are really necessary for most of the proce­
dures.

v)

Leakages from Tube head s There is no other way to detect

leakages from tube head (that will give substantially more rad­
iation than the weak back radiation} than special detectors like
the Geiger counters. Whenever new installations/changes are made

it is mandatory to check for this with the help of special

services.

BARC can help in this.
...5/
a
■h

s
vi)

:

5

Film and screens : Insensitive films/screens entail a longer

exposure of the subject and staff and also reduce machine lift.
It is necessary to use suitably sensitive films/screen to minimi­

se exposure.

vii) Design and shielding : X ray can penetrate and have to be
stopped from affecting surrounding people by special design and
devices.

As dar as design is concerned,adquate spacing is the

first important thing.Since radiation at a given point is inver­
sely proportional to distance from the source. Thus a unit ' '■
housed in a 10 x 10 feet room is more hazardous to outside people
than the same unit housed in a 15 x 15 feet room.

this is a restraint in many Xray clinics.

Unfortunately

Secondly the useful

beam har to be primariely directed at exterior wall so that

minimum exposure occurs to the surrounding life. Thus it should
not be directed at the waiting room,wards, street,passages unless
adequately shielded.

The control panel should be outside the

Xray room in units operating more than 50 kv machines.

As for shielding,lead and wall thickness are two principal cons­

iderations.

For every 50 Kv rating of the machine a 0.5mm lead

thickness is necessary to stop the useful beam(eg the fluroscopy
procedures)
Stray radiation can be taken care of by putting a
0.25mm lead barrier (the usual lead aprons) provided the staff

is distanced at about 10 ft from the source.

A 9 inch brick

mortar wall is equivalent to 1mm lead thickness and so is a 6
inch concrete slab.

All walls should be designed to stop the

primary radiation of the useful beam. Since machine position,
direction of beam, installation etc.can change subsequently and
this should be kept in mind. Doors/windows should be sheilded
with a 1mm lead thickness with

adequate overlap so that radi­

ation does not escape the gaps.

It is always better to seek

help of radiation engineers while designing the unit.
viii) Staff Monitoring for radiation ; Xray unit staff and other
. staff routinely coming in contact of Xray units(Nurses/Ward-

servants etc.) are exposed to radiation.

Unless proper preca­

utions are taken tio restrict staff entry in 'switch-on' time,
and .adequately protect the operating staff a great risk awaits
them by way of cancers, leukemias and gonadal irradiation.

Standing behind the Xray tube,lead aprons,control panel,adequate
distance are all necessary.

The film badge monitoring is a

routine method in upper strata Xray clinics.

In the lower cate­

gory of taluka level units,bazar clinics and minor units
operating in small nursing homes no such monitoring is ever done;
perhaps with the idea that the dose involved is low.In this
context,the conditions in the latter category are quite bad

...6/

6

since most of the operators have little, knowledge of the
potential risk of this invisible me'ahce.

At present there is no

working mechanism of regulating the conditions at such clinics.
Although the total work load is quite small in this category,the
neglect of basic protective factors understandbly constitutes a
very real threat to both patients and operators.

7.

CONCLUSION

Xray are a great help in patient management. Generally speaking
MPD is not exceeded both in case of staff and patients since
there is a relative paucity of facilities in developing countries.

As for the well equipped clinics with adequate sheilding and care
little harm is done to staff and the risk is acceptable.

As for

the J.ower rung units conditions are apalling, with potential risk
for both the patients and staff and much needs be done to regula­

te these units.

Gonadal irradiation must be avoided in early and

middle age groups

whenever not necessary.

A longterm projection

of gonadal irradiations to a fair portion of population (that is
going to bear progeny) indicates .accumulation of abnormal
elements in the genetic pool and this can be real cause of conCancer risks
cem: .in the exposed populations is going to increase but no
r A.
generalisation can be possible in this regard. Early age of
exposure, no. of exposures procedures involving high dose to susceptible organs are all risk factors to be watched.

8.

REFERENCES s

<1) Mannual on Radiation Protection in hospitals and General
Practice : Volume 1

By C B Braestrup & K.J. viktelof WHO

Publication. Geneva 1974 PP 28/29,31,27

(2) X-RAYS, HEALTH EFFECTS OF COMMON EXAMS :

By John W.Gofman
& Egan O'Connor, Sierra Club books, San Fransisco 1985
PP 86,87,2,349

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