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Imaging with X-RayBy Nipun
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IMAGE QUALITY
WHAT IS IMAGE QUALITY?
Image quality describes the !erall a""eara#ce $ thea#d its ftness or purpose.
There is al%ays a "lay& bet%ee# image quality a#d dse'
S %e al%ays #eed images that are $ diag#stic !alu$r "ur"se #t the !isually a""eali#g "ictures'
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IMAGE QUALITY
The mai# $actrs t c#sider are) *#trast
S"atial +esluti#
,ise
-istrti# .lur
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*/,T+AST
*#trast0 r mre "recisely c#trast resluti#0is the ability t disti#guish bet%ee# ad1ace#tareas $ the image'
S0 better c#trast mea#s better a""reciati# $
The amu#t $ c#trast bet%ee# tissues is i#tri#li#2ed t their "r"erties a#d the imagi#g mdabei#g used'
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*/,T+AST
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+adigra"
hicc#trast)
3ilm
c#trast
Sub1ect
c#trast
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SU.4E*T */,T+AST
A structure i# the "atie#t is dem#strated by t%
Resolution, sharpness0 r lac2 $ blurri#g $ thimage $ its bu#dary'
Contrast bet%ee# it a#d ad1ace#t tissues causedi&ere#ces i# the tra#smissi# $ 56rays 7r atte$ 56+ays8'
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3A*T/+S A33E*TI,G SU.4E*T*/,T+AST
Sub1ect c#trast C de"e#ds #)The thic2#ess t $ the structure'
The di$$ere#ce i# li#ear atte#uati# ce$$icie#ts $ the tissues i#!l!ed %hich is de"e#de#t # thde#sities a#d atmic #'
Thus
C = (1 2) t
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3A*T/+S A33E*TI,G SU.4E*T*/,T+AST
As atte#uati# de"e#ds # tissue de#sity a#d at#umber)
The mre the t% tissues di&er i# these res"ectsgreater the c#trast'
The higher the 2 > the smaller the atte#uati#
ce@cie#ts > the less is the c#trast
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3A*T/+S A33E*TI,G SU.4E*T*/,T+AST
+adiati# quality ) e#etrati#g ability r 2' Mremre is the "e#etrati#g "%er0 less is the c#tra
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.ALA,*I,G */,T+AST A,-ATIE,T -/SE
A ma1r c#siderati# i# 56+ay imagi#g is t restrict th$ the "atie#t as much as "ssible des"ite able t "rdsatis$actry image'
e#etrati#0 *#trast a#d atie#t -se de"e#d u"# 5beam s"ectrum0 the best s"ectrum "r!ides adequate
e#etrati# a#d *#trast %hile 2ee"i#g the atie#t -l%est "ssible
The s"ectrum "rduced is de"e#de#t u"# the target i#here#t r added (ltrati# a#d 2il6!ltage'
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.ALA,*I,G */,T+AST A,-ATIE,T -/SE
L% E#ergy 728 B L% e#etrati# B High *#tHigh atie#t -se
High E#ergy 728 B High e#etrati# B L% *#tL% atie#t -se
/"timum Situati# ) 2 that gi!es adequatec#a# acceptable"atie#t dse'
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ATIE,T -/SE
This is abut CGy or ilm screen radiography a
between about 0.2 and 0.5 Gy s-1 or uoroscop
!his is the e"it dose emerging rom the patient.
The e#tra#ce sur$ace dse has t be much highebecause $ high atte#uati# $ 56+ays by the "a
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3ILM */,T+AST
Factors affecting film contrast:
Films vary in inherent contrast depending on- Emulsion characteristics.
Development process.
Time-temperature used in processing.
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/!er eD"sed (lm
U#der eD"sed
MaD'c#trast
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*/,T+AST ME-IA
/#e %ay $ i#creasi#g the c#trast is t use a la#ther is t use a c#trast medium'
A c#trast media is a radi6"aque media %ith hatmic #'
The high atmic #' $ the c#trast maDimiFes t"htelectric absr"ti# $ the 56+ays'
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*/,T+AST ME-IA
The t% cmm# c#trast age#ts are Idi#e 76.arium 768'
Air ca# als be used as c#trast media but #% #ly i# duble c#trast barium e#ema studies'
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*/,+AST A,- S*ATTE+
rimary radiati# carries the i#$rmati# t be im
Scatter bscures it as it carries # i#$rmati# a%here it came $rm'
The amu#t $ scatter 7S8 may be se!eral time tamu#t $ "rimary 78 i# the same "siti#'
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*/,+AST A,- S*ATTE+
The SJ +ati de"e#ds # the thic2#ess $ the "atie#t'
3r ty"ical A *hest it is K); 7
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*/,T+AST A,- S*ATTE+
S*ATTE+ +A-IATI/,result i# 3/GGI,G $image'
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SATIAL +ES/LUTI/,
SATIAL +ES/LUTI/, is the ability t detedetail %ithi# a# image'
3i#e detail is mst clearly see# %he# thec#trast bet%ee# the $eature a#d its bac2is high'
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SATIAL +ES/LUTI/,
S"atial resluti# ca# be qua#ti(ed as the higheccurri#g $reque#cy $ li#es that ca# be resl!edhigh c#trast bar "atter#'
The b1ect used t measure the s"atial resluti
2#%# as #$%& '($) !&*! !++#.
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SATIAL +ES/LUTI/, O LI,E AITEST T//L It uses bars $ lead %ith
%idth $ bar equal t thes"ace bet%ee# them'
A bar a#d s"ace ma2es u"the li#e "air a#d s"atial$reque#cy $ the "atter# is
gi!e# as li#e "air "er mm'
The smallest !isible detail isa""rDimately hal$ $ thei#!erse $ the resluti#eD"ressed i# this %ay
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,/ISE
,/ISE re$ers t the !ariati#s i# the le!els $ greimage that are distributed !er its area but u#rethe structures bei#g imaged'
The mst sig#i(ca#t surce $ #ise i# radilgic
imagi#g is quantum noise or mottle'
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,/ISE
,ise reduces the !isibility $ l% c#trast regi#%ithi# the image0 "articularly i$ they are small i#thus reduci#g the !isibility $ (#er detail i# the i
The l%er the #' $ "ht#s detected0 the great
be the #ise'
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Qua#tum mttle
Audible or visible disturbance that hampers theinformation'
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Quantummottle
Normal
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Lesser for slow screen film than fastscreen film'
Increases with high contrast film asdensity differences are exaggerated
Increases with increase of KV .
QUA,TUM M/TTLE
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ATTE,UATI/, /3 56+AYS .Y THATIE,T
In conventional projection radiography, a $au#i$rm0 $eatureless beam $ 56radiati# $alls #"atie#t > it is di&ere#tially absrbed by the tissuthe bdy > the 56ray beam emergi#g $rm the "carries a "atter# $ i#te#sity %hich is de"e#de#tthickness a#d composition o the organs in th
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ATTE,UATI/, /3 56+AYS .Y THATIE,TThe 56rays emergi#g $rm the "atie#t are ca"turelarge Pat "hs"hr scree# > this c#!erts the i#!ray image i#t a !isible image $ light0 %hich the#either)
+ecrded as a #egati!e image # (lm0 t be !ie%
a light bD 7(lm O scree# radigra"hy8 +ecrded electr#ically "rir t "ri#ti#g 7cm"ut
direct digital radigra"hy8
-is"layed as a "siti!e image # a !ide m#it7Pursc"y8'
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-IST/+TI/,
Distortion
Size Sha
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SiFe 6 Mag#i(cati#
Shrter the dista#ce bet%ee# b1ect a#d the sulight0 greater is the mag#i(cati#'
Surce $light
b1ect
shad%
Surce $ ligh
b1ect
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Law of magnication states that%idth $ the image is t the %idth $the b1ect0 as the dista#ce $ image$rm the light surce is t dista#ce$ the b1ect $rm the light surce
Image width = Image distance !"#ect width !"#ect distance
Li i ti f i
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Linear magnication of imag
Mag#i(cati# $actr) image %idth
6666666666666666666666
b1ect %idth'
Mag#i(cati#) image %idth 6 b1ect %idth
666666666666666666666666666666666
b1ect %idth
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Sha"e distrti#)
It is misalignment ofcentral ray, the anatomic
part and the film.
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T SummariFe'
Greater distrti# mea#s "rrecrded detail
Sha"e distrti# is due tim"r"er alig#me#t
SiFe distrti#) mag#i(cati# is due tdi!erge#ce $ beam' Shrter the /I- a#d L#ger the SI- O less is the
distrti#'
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Macrradigra"hy
reser!ati# $ recrdeddetail %hile achie!i#g
mag#i(cati#'
3racti#al $cals"tJmicr$cus tubes areusedR %ith small $cal
s"t 7'Cmm8
Principleofradiographic
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Principle of radiographicmagnification
%
o
&!' &
Image
Ideal "i#tsurce
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.lur
+eometric"lur
!"#ect "lur
&creen"lur
,otion "lur
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Gemetric .lur 7e#umbra8
Arra#geme#t $ 56+ay0 a#atmical "art a#d (lm s"ace'
-e"e#ds #)
-.ecti/e focal s*ot si0e
&ource to image rece*tor distance
!"#ect to image rece*tor distance
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3cal s"t is larger tha# b1ect
3i#ite
$cal s"t
b1ect
.lur
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E&ecti!e $cal s"t siFe
3cals"t
blu
r
3cal s"t
3cal s"t
blur
A . *
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E&ecti!e $cal s"t
,rmal siFe $ $cal s"t u#derstates the e&ecti!
"r1ected siFe $ the s"t by sig#i(ca#t margi#'
ED) 'C mm $cal s"t may be as large as 'Kmm
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b1 i di
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/b1ect image rece"tr dista#ce
A .
Mti# blur
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Mti# blur
Any motion while taking a radiograph can hampe
image.
b iii db
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It can be minimised by:
ImmbiliFati#$ the "art bysa#dbags rcm"ressi#
ba#ds
Sus"e#si#
$res"irati#
Usi#g sh
eD"sure
S bl
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Scree# blur
Cardboard holders provide better recorded
detail than screen as immobilization ispresent
In uncontrolled motion: fast exposurewith screens is used.
Extremely short exposure using highspeed screen can hamper recorded detail.
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3ilm scree#
cmbi#ati#)
Its a combination of film andintensifying screen.
Recorded details is better in fastspeed and medium speed screen
combination
d d d t il i h ith
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ecorded detail is ne/er shar* withintensifing screen "ecause
*rystalsiFe
Acti!elayer
thic2#es
s
3ilmscree#
c#tact
Q t M ttl
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Qua#tum Mttle
Audible or visible disturbance that hampers inform
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Quantummottle
Normal
/b1ect blur
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/b1ect blur
E&ect $ b1ect blur is greater tha# a""reciated'
/b1ects ha!i#g ru#d brder i#trduce blur $act
/b1ect .lur
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/b1ect .lur
T SummariFe
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T SummariFe'
.lur decreases %ith decrease i# $cal s"t siFe0 /
i#crease i# SI- Mti# blur decreased by immbiliFati# r shr
eD"sure
*ardbard hlders decrease scree# blur
+u#ded b1ects i#crease blur' Quantum mottle$ /isi"ledisturba#ce i# D ray
Less i# sl% scree# rece"trs0 mre i# $ast scree# rec
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Sil!er halide
Metallic sil!er
A""ears blac2
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Radiographic density depends on:
Amount of radiation reaching a particular area of
film
The resulting mass of metallic silver deposited pe
area
Measureme#t
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Measureme#t
Measured by a# i#strume#t called -E,SIT/METE
Density = log incident light intensity
transmitted light intensity
Clear film: has a density of 0.06-0.2
Diagnostic radiograph: 0.4 in lightest area and 3 in
3actrs A&ecti#g ED"sure a#d
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-e#sityKV: KV- exposure rate- density
Milli ampere: increases exposure rate
Time: increase in exposure time- increases no. of photoemitted by target.
mA.s: measure of charge transferred from cathode to anduring an exposure.
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X-ray photons arise from variouspoint of focal spot.
Assume photons spread in form ofcone from focal spot after leavingtube'
E33E*T /3
-ISTA,*E)
Radiographic exposure rate decreasesas focus film distance increases'
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+adigra"hic b1ect
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+adigra"hic b1ect
Thic2er a#d de#ser
a#atmical "arts
mre absr"ti# $ Dray'
less eDit $ radiati# #t (lm
/rder $ tissue de#sity
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-e#tal
e#amel
.#eTissu
e3at gas
T summariFe'
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T summariFe'
-e#sity is dar2e#i#g $ D ray (lm due t de"sit
sil!er'
-e"e#ds #6 2!0 mA0 eD"sure time0 dista#ce0 de#sity'
As the dista#ce $ (lm $rm surce i#creases0 eDdecreases'
'-6IC-& %!
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'-6IC-& %!I,7!6IN+'I!+78IQ9LI:;
.y)-r' ,i"u# Gu"ta
&C::--' 'I:I!N
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&C::--' 'I:I!N
As the primary beam pass through the patient,
some of the radiation is absorbed, while the rest
is scattered in many directions
This multidirectional scattered radiation is a
noise factor
In a radiograph of good!uality, less than one-fourthe density should result
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the density should resultfrom scattered radiation.
:I! !% &C::--' :! 7I,; 'I
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It increases with"
increase in the area of the radiation field
and the thic#ness of the part
increase in tube potential
increase in the density of the tissues
Chest 80%scattered 20%primary
Abdomen - 90%scattered 10%primary
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'I!+78IC +I'
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$e/eloped by Gusta/ Buc#y in 0102
It is a de/ice placed between the patient and
the cassette for the purpose of reducing
the amount of scattered radiation reaching thefilm and impro/ing radiographic contrast
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Gusta/ Buc#y3s original gird
+ross hatch type
)odern stationary grid consists of thin , closely
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spaced lead strip measuring about 445mm inwidth
Radiolucent material, plastic or aluminiumseparate them which is 422mm wide
Aluminum is preferred for impro/ed durability of
the grid
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'6N:+-'I&'6N:
+-
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Re!uireIncreas
ede6posure
+astshadowsontheradiographas
thinwhitelines
Absorb147scattered
radiation
-%%ICI-NC; !% 'I!+78IC +I'&
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$epends on
%hysical factors .unctional factors
78;&ICL %C:!&
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0 Grid ratio "- r 8 d9w:d-depth of the interspace channel,
w-width of this channel;
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$epends on"
0 *electi/ity
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Selecti!ity
grid cutoff %rimary radiation transmitted 9scattered radiation transmitted
*#trastIm"r!eme#t 3actr
# 8 Radiographic contrast with grid9Radiographic contrast with out grid
:89,< 9L-
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If Object > 11 Cm Thick Grid is to be used
Grid is to be always used With Intensifyin
!creen
+I'
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Stationary grid
Moving grid
&::I!N; +I'
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Thin wafer grids
Taped to the front of cassette
'sed with intensifying screen
>+R**&$ GRI$= is used in +erebral angiography
*tationary Grid
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Non focused focused
7LL-L ! N!N %!C9&-' +I'
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$istance decentering
'sed in fluoroscopy
7LL-L ! N!N %!C9&-' +I'
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Angulation decentering
%!C9&-' +I'
) f l d
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)ore fre!uently used type
+omprise of parallel strips
*lant more towards lateral edges around a +N?&RG&N+& IN&
'sed in *tanding Abdomen *can, ateral +er/ical
*pine, *wimmers ?iew, %ortable
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,!6IN+ +I'
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$e/eloped by $r (ollis %otter - 01
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%R&+A'TN* IN T(& '*& . .+'*&$ GRI$*
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This sho!d be "ept more #or a c!earerimage to minimise the scattered radiationand a!so the b!rring$
0 *'R+& I)AG& R&+&%TR
$I*TAN+&
n &ocsed grid there ni#orm decrease in densityo# radiograph
n 'on#ocsed grid there is decentering o# beam
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)*C+, . /. &ACT. & 12 1 S .3&3..3 )3C
14 ts e##iciency in c!eaning p scattered radiation$
24 Centering is !ess critica!$
54 6ess e7posre to the patient$4 6ead strips are thic"er there by absorbing more
e##icient!y$
-,!6L !% &C::--' 'I:I!N
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*pace between the patient and the
image receptor is #nown as air gap
Increasing the air gap allows more of the scattered
photons to mo/e laterally outside the film area
$ue to In/erse *!uare aw, there is only small reduction in prima
intensity which can be compensated by increasing the ma
This also result in magnification of image
There is no absorption of scattered radiation in
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the air gap
It re!uire increase in e6posure factors to
#eep radiographic density unchanged
This techni!ue has a place in chest radiograph,
magnification radiograph and in cerebral and
renal angiography
eduction !f &cattered adiation
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Aperture $iaphragms
+ones
+ollimators
7-:9- 'I78+,
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C!N-&
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.AR&$ +N& +IN$&R +N&
C!LLI,:!&
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AN$& (&& &..&+T AN$& +'T ..
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epends on the ang!e the rays ma"e (ith the #ace
o# the targetThe variation in e7posre rate according to the
ang!e o# emission o# the radiation at the #oca! spot
is ca!!ed anode cto## or anode hee! e##ect
Sma!!est e7posre rate occrs at the anode
*se#! in radiographing a region (ith (ide range
o# thic"ness $
Thickest "art is towards the cathode end of the beam
Thinnest "art is towards the anode.
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C!,7-N&:I!N %IL:-&
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Made p o# a!minim or barim p!astic
:ide app!ication in genera! radiography sch as aort arch angiography; Anteropost$ pro
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THA, Y/U