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A quality assurance program in dental radiology · A quality assurance program in dental radiology...
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PEDIATRIC DENTISTRY/Copyright © 1981 byThe American Academy of Pedodontics/Vol. 3, No. 1
A quality assurance program indental radiology
Richard W. Valachovic, DMDAllan B. Reiskin, DDS, DPhilSusan T. Kirchhof, RT
AbstractA quality assurance program in radiology provides the
basis for systematic measurement of various parameterswhich affect the quality and production of a radiographicimage. We have outlined a program which can beimplemented in dental offices by dentists or auxiliarypersonnel without sophisticated instruments. Tests designedto establish the adequacy of specific functions are describedtogether with reasons for poor image quality.Implementation of a quality assurance program results inreduction in expenditures, increased radiation thrift andimproved diagnosis.
IntroductionThe production of radiographs involves several
complex processes. Small variations in exposure geom-etry, beam quality or processing technique can havedramatic results on the final image. If one wishes togenerate consistent and diagnostic radiographs, care-ful regulation of the imaging process must be rigor-ously maintained. Simple steps can be taken to assurethat uniform image production is achieved throughthe utilization of a systematic quality assuranceprogram.1 In addition to its contribution to the pro-duction of high quality images, such a quality assur-ance program also plays a major role in keeping pa-tient exposure to a practical minimum.2
This paper will describe a quality assurance pro-gram that can easily be implemented in the privatedental office to efficiently monitor the various param-eters that affect the characteristics of the radio-graphic image. Through the regular application of thisprogram, problems in any aspect of image productioncan be readily identified and corrected.
Accepted: October 3, 1980
RADIOLOGY QUALITY ASSURANCE PROGRAMValachovic, Reiskin, and Kirchhof
Parameters Which Affect Image QualityThere are four basic parameters which affect image
quality that may be measured: (1) image processing;(2) the basic characteristics of the x-ray generator; (3)image receptors; and (4) darkroom inte~,qdty (Table All of these parameters may be measured to a limiteddegree of sensitivity without sophisticated equipment.
The most frequently encountered reason for varia-bility in producing an image is in the processing of theexposed film; this is the one parameter over which thedentist has the most control. X-ray generator per-formance is generally quite stable and maintenance isusually delegated to a qualified serv~ceperson. Thequality of most commercial film products is not highlyvariable and is easily maintained through proper stor-
Table 1. Quality assurance tests and frequency of performance.
Tests of Image Processing: Every DayA. Solution temperaturesB. An index of speedC. An index of contrast
Tests of X-Ray Generator Performance: Every 3 MonthsA. Reproducibility of x-ray outputB. Linearity of mAs stationsC. Field size and densityD. Mechanical stability of suspension
Tests of Image Receptor Quality: Every MonthA. Base plus fogB. Film artifact identification
Tests of Darkroom (or Daylight Loader) Integrity: EveryMonth (or with every change of safelighting)
A. Light leaksB. Safelight conditions
Tabl
e 2.
Tro
uble
shoo
ting
the
poor
qu
ality
im
age
Poss
ible
Cau
ses
(Lis
ted
in d
esce
ndin
g or
der
Tes
ting
Proc
edur
es
Obs
erva
tion
of p
roba
bilit
y)
(if a
pplic
able
: see
text
)
1. S
ight
dev
elop
men
t 2.
Pro
cess
ing
erro
rs
Tes
ts o
f im
age
proc
essi
ng
A.
Exh
aust
ed s
olut
ions
B
. D
evel
opm
ent t
ime
too
shor
t C
. D
evel
oper
tem
pera
ture
too
low
D
. Im
prop
er m
ixin
g of
che
mic
als
Con
sist
ently
lig
ht
film
s 3.
Inc
orre
ct e
xpos
ure
fact
ors
4. E
xpir
ed fi
lm
5. V
aria
ble
gene
rato
r per
form
ance
Che
ck te
chni
que
char
t T
ests
of i
mag
e re
cept
or q
ualit
y T
ests
of g
ener
ator
per
form
ance
Cor
rect
ive
Act
ion
Sigh
t dev
elop
men
t sho
uld
not b
e us
ed
Rep
leni
sh/r
epla
ce a
t pro
per
inte
rval
s Fo
llow
man
ufac
ture
r’s r
ecom
men
datio
ns
Follo
w m
anuf
actu
rer’
s rec
omm
enda
tions
Fo
llow
man
ufac
ture
r’s r
ecom
men
datio
ns
Adj
ust e
xpos
ure
fact
ors a
s ne
cess
ary
Dis
card
exp
ired
film
C
all s
ervi
cepe
rson
1. P
roce
ssin
g err
ors
Tes
ts o
f im
age
proc
essi
ng
A.
Dev
elop
er te
mpe
ratu
re t
oo h
igh
B.
Dev
elop
men
t tim
e to
o lo
ng
Follo
w m
anuf
actu
rer’
s rec
omm
enda
tions
Fo
llow
man
ufac
ture
r’s
reco
mm
enda
tions
C
onsi
sten
tly
C.
Dev
elop
er to
o co
ncen
trat
ed
Follo
w m
anuf
actu
rer’
s re
com
men
datio
ns
dark
D
. So
lutio
n co
ntam
inat
ion
Avo
id c
ross
con
tam
inat
ion
films
2. I
ncor
rect
exp
osur
e fa
ctor
s C
heck
tech
niqu
e ch
art
Adj
ust e
xpos
ure
fact
ors a
s ne
cess
ary
3. F
ogge
dfilm
s A
. E
nvir
onm
enta
l exp
osur
e B
. L
ight
leak
s T
ests
of i
mag
e rec
epto
r qu
ality
T
ests
of d
arkr
oom
inte
grity
S
tore
film
pro
perl
y (s
ee te
xt)
Secu
re p
roce
ssin
g ar
ea fr
om li
ght l
eaks
4.
Var
iabl
e ge
nera
tor p
erfo
rman
ce
Tes
ts o
f gen
erat
or p
erfo
rman
ce
Cal
l ser
vice
pers
on
1. P
roce
ssin
g er
rors
T
ests
of i
mag
e pr
oces
sing
Fo
llow
man
ufac
ture
r’s r
ecom
men
datio
ns
2. V
aria
ble
gene
rato
r per
form
ance
T
ests
of g
ener
ator
per
form
ance
C
all s
ervi
cepe
rson
V
aria
ble
A.
Tim
er m
alfu
nctio
n A
. lin
eari
ty a
nd re
prod
ucib
ility
dens
ity
C.
Vol
tage
inst
abili
ty
C.
repr
oduc
ibili
ty
film
B.
mA
inst
abili
ty
B.
linea
rity
3. X
-ray
tube
det
erio
ratio
n T
est o
f fie
ld s
ize a
nd d
ensi
ty
Cal
l ser
vice
pers
on
1. F
ogge
dfilm
s A
. E
nvir
onm
enta
l exp
osur
e T
ests
of i
mag
e rec
epto
r qua
lity
Sto
re fi
lm p
rope
rly
(see
text
) V
aria
ble
B.
Lig
htle
aks
Tes
ts of
dar
kroo
m in
tegr
ity
Secu
re p
roce
ssin
g ar
ea fr
om li
ght l
eaks
fil
m
C.
Impr
oper
han
dlin
g T
est o
f film
art
ifac
t H
andl
e fil
m w
ith c
are
duri
ng p
roce
ssin
g co
ntra
st
2. U
nsta
ble
deve
lope
r tem
pera
ture
T
ests
of im
age
proc
essi
ng
Follo
w m
anuf
actu
rer’
s rec
omm
enda
tions
3.
Var
iabl
e ge
nera
tor p
erfo
rman
ce
Tes
ts of
gen
erat
or p
erfo
rman
ce
Cal
l ser
vice
pers
on
Blu
rred
1.
Pat
ient
mov
emen
t W
atch
pat
ient
dur
ing
expo
sure
im
age
2. I
nsta
bilit
y of
sus
pens
ion
Tes
t of m
echa
nica
l sta
bilit
y A
djus
t sus
pens
ion as n
eces
sary
m
1. C
one
cutt
ing
8 Pa
rtia
l A
. T
echn
ical
mal
posi
tion
Alig
n fie
ld w
ith
imag
e re
cept
or
imag
e B
. P.
I.D.
mal
alig
nmen
t T
est o
f fie
ld si
ze a
nd d
ensi
ty
Tes
ts o
f im
age p
roce
ssin
g A
djus
t as n
eces
sary
or c
all s
ervi
cepe
rson
R
eple
nish
/rep
lace
at p
rope
r int
erva
ls
2. I
nade
quat
e im
mer
sion
of f
ilm
into
solu
tions
1. P
roce
ssin
g er
rors
T
ests
of im
age
proc
essi
ng
Avo
id c
ross
cont
amin
atio
n Fo
llow
man
ufac
ture
r’s r
ecom
men
datio
ns
A.
Solu
tion
cont
amin
atio
n B.
Inc
ompl
ete
agita
tion
“f
9;
Z
G
-4
Fi
lm
C.
Impr
oper
han
dlin
g H
andl
e fil
m w
ith c
are
duri
ng p
roce
ssin
g A
rtif
act
D.
Soile
d pr
oces
sor
rolle
rs
Cle
an p
roce
ssor
at r
egul
ar in
terv
als
2. F
ogge
dfilm
s A
. E
nvir
onm
enta
l exp
osur
e B
. L
ight
leak
s T
ests
of im
age r
ecep
tor q
ualit
y T
ests
of d
arkr
oom
inte
grity
S
tore
film
pro
perl
y (s
ee te
xt)
Secu
re p
roce
ssin
g ar
ea fr
om li
ght l
eaks
N
3.
Def
ectiv
e fil
m q
ualit
y T
ests
of im
age r
ecep
tor q
ualit
y D
isca
rd d
efec
tive film
-I
age; however, all film packages should be routinelytested before use. Finally, the integrity of the dark-room (or daylight loader of an automatic processor) iseasily evaluated and corrected as necessary (Table 2).
Quality Assurance Testing ProceduresA test object or step wedge which will be used
throughout these quality assurance procedures, andwhich is sized for use with No. 2 dental x-ray film maybe purchased commercially" or constructed using dis-carded sheets of lead foil saved from used No. 2 dentalx-ray film packets. Figure 1 illustrates the method of
aSpectroline X-Ray Analyzer Model 8958, Spectronics Corp.,29 New York Ave., Westbury, Long Island, NY 11590.
Figure 1: Construction and utilization of an office-constructed test
object for use with No. 2 dental film.
IA: Cut a paper template to the size of a No. 2 dental film. Draw
lines horizontally at '/•" intervals.
1 B: Tape pieces of lead foil saved from used No. 2 dental film
packets at each marked interval. Cut off excess lead foil to size of
paper template.
1C: Insert template to which the pieces of lead foil have been
taped into an empty No. 2 dental film packet.
1 D: When using test object, place it on top of film to be exposed
on a flat surface. Place tip of P.I.D. over test object and film in con-
tact with flat surface.
28RADIOLOGY QUALITY ASSURANCE PROGRAM
Valachovic, Reickin, and Kirchhof
construction. A thermometer for measuring solutiontemperatures is the only other instrument that isneeded.1. Image Processing. Film processing is the singlemost variable step in the production of an x-rayimage. Therefore, the following tests should be per-formed on a daily basis. Reproducible results can onlybe obtained if a time/ temperature method of develop-ment is adhered to.3 "Sight developing" should neverbe used during these quality assurance tests or routineprocessing.
A thermometer should be allowed to come to equi-librium in the developing solution before any testingof image processing begins. If at all possible, the opti-mal time and temperature recommended by the man-ufacturer should be used; with most products, this willbe 68 °F and five minutes.
A standard test film which will be the basis of fu-ture comparisons of image processing should be pre-pared using a machine which is known to be properlycalibrated and its performance verified. Expose a No.2 dental film through the test object using normalmandibular molar technique. This radiograph shouldbe processed in freshly prepared solutions according tothe manufacturer's recommendations. After the filmhas been properly washed and dried, it should bemounted and kept in a safe place for future daily com-parisons. When similar exposures are made on a dailybasis, changes in film speed can be determined by therecognition of overall decrease or increase in density(Figure 2A). A similar test for automatic processorscan be performed by deriving a standard using thesame procedures described above. Alterations in filmcontrast can be recognized by non-uniform changingof density on the steps exposed through the test object(Figure 2B). The step with the least amount of leadshould be completely black, representing near maxi-mum density. Each individual step should have a uni-form density; variation within a step being an indica-tion of artifact.
2. Tests of the Basic Characteristics of the X-rayGenerator. The basic characteristics of the x-ray gen-
A B
Figure 2: A: Left side: standard test film (see text). Right side:
test film showing change in film speed as evidenced by overall
changes in density.
B: Left side: standard test film (see text). Right side: test film show-
ing change in film contrast as evidenced by non-uniform changing
of density on the steps.
erator which may easily be measured by the dentist orauxiliary personnel without specialized equipmentare: reproducibility of x-ray output, linearity of mAsstations, field size and density, and mechanical stabil-ity of the tube head and arm suspension.
Reproducibility refers to the consistency of the x-ray output over time of an individual machine usingthe same technique factors.4 Linearity refers to the re-lationship between the change in x-ray output as afunction of time from an individual machine assumingall other technique factors remain constant.5 The sizeof the x-ray field as it exits the P.I.D. (position indi-cating device or "cone") must be no larger than a legallimit of the state in which the generator is located andits density should be uniform. The suspension of thetube head and arm must be stable in any given posi-tion to prevent motion distortion. It is our recommen-dation that the following tests be used to measurethese elements of x-ray generator performance per-formed at a minimum of three month intervals.
(a) Reproducibility of x-ray outputExpose a group of films through the test object one
at a time using normal mandibular molar technique atfive minute intervals for a total of six exposures. Whenall of the films are processed together in freshly pre-pared chemicals, the densities at each step shouldmatch precisely (Figure 3A). If the density at eachstep of the test object does not match on a set of filmswhich are processed together, one must presume thatthere is a fault in machine performance (Figure 3B).
B
Figure 3: A: Six test films with equal densities at each step show-
ing reproducibility of x-ray output.
B: Six test films with varying densities at each step showing lack of
reproducibility of x-ray output.
Several factors may contribute to this variability.Unstable line voltage is a common reason for the pro-duction of films of different densities and contrastlevels; however, in most parts of the country, electri-cal supplies are carefully regulated and informationabout the power supply can usually be obtained fromthe electric company or a building engineer. In addi-tion to fluctuations in line current, deteriorating per-formance of the x-ray timer or mA stabilizer can also
PEDIATRIC DENTISTRY
Volume 3, No. 1 29
produce differences in both density and contrast. Theend result of each of these problems is a loss of repro-ducibility which means that images on radiographs ex-posed using the same technique factors will not becomparable.
(b) Linearity of the mAs stationsOne film should be exposed through an office fabri-
cated test object using normal mandibular molar tech-nique. A second film should be exposed through thesame test object using one-half of the mAs of the firstexposure and a third film exposed using twice the mAsof the first exposure. When the three films are proc-essed together, step two on the first film (normalmolar technique) should be equivalent to step one onthe second film (one-half of the mAs of the first film)and step three of the third film (twice the mAs of thefirst film). Figure 4A illustrates this relationship.Should a comparable visible shift fail to occur, onemay presume that there is a lack of linearity in chang-ing from one mAs to another (Figure 4B). The end re-sult will be an inappropriate change in density as themAs is changed.
A B
Figure 4: A: Three test films with appropriate relationship (see
text) showing linearity of the mAs stations.
B: Three test films without appropriate relationship (see text) show-
ing lack of linearity of the mAs stations.
(c) Field size and densityThe field size at the end of the P.I.D. can be simply
measured by exposing an occlusal film which is in con-tact with the open end of the cylinder. The darkenedarea of the film should measure no more than 2.75inches or 7.0 centimeters.6 In addition, the densityacross the exposed part of the film should be uniform(Figure 5A). If the field size exceeds the legal limit orif the density is not uniform, the possibility of a badlyfitting or damaged P.I.D., or of a malpositioned x-raytube in the tube housing should be investigated (Fig-ure 5B). Machines which use a lead diaphragm for col-limation should be examined for improper positioningor alignment of the diaphragm if problems are evidentduring testing.
Malalignment of the x-ray field may result in cone-cutting or image distortion. Density aberrationsacross the field may result in non-uniformity of thedensity of the image. In general, defects found as a re-sult of these tests of machine performance cannot be
Figure 5: A: Occlusal test film showing acceptable field size and
uniform density.
B: Occlusal size test film showing unacceptable field size and non-
uniform density.
remedied by the dentist but require the efforts of aproperly trained serviceperson.
(d) Mechanical stability of the suspensionThe tube head of an x-ray generator is suspended
from its support by a retractable arm. If the suspen-sion is not stable, the tube head may drift or vibratewhile its arm is extended during use. The stabilitymay easily be measured by placing the tube head andarm at the maximum extension from the support.Watch for drift or vibration as the tube head is re-leased. If there is any movement of the tube head, theresult may be motion distortion. Such instability maybe corrected by adjusting the suspension as recom-mended by the manufacturer in the operator's manual.
3. X-Ray Receptors. The quality of most dental x-ray film is carefully controlled by the manufacturer incompliance with industry standards.7 A commoncause of spoiled film is fogging, often the result of im-proper storage. To measure the amount of base plus
30RADIOLOGY QUALITY ASSURANCE PROGRAM
Valachovic, Reiskin, and Kirchhof
fogb of dental x-ray film, process an unexposed film infreshly prepared solutions. Following adequate wash-ing and drying, most dental x-ray film should appeartransparent with a slight blue tinge. No artifactsshould be noted on the film. If fogging is noted on thetest film, one should examine the method of storageand rotation of the boxes of film. Dental film is bestkept refrigerated and away from any source of radia-tion, chemical vapor, heat or high humidity. Filmshould be purchased at intervals which insures useprior to its expiration date. Film which has passed theexpiration date should be discarded and never used fordiagnostic purposes0. This test should be per-formed monthly.4. Darkroom or Daylight Loader Integrity. It isimportant to insure that no light capable of sensitiz-ing the film be allowed into the darkroom (or daylightloader of an automatic processor). A simple test forthis problem is to remove a dental film from its packetin a safelighted darkroom and place it on a flat surfacein the area where film is normally handled (or on aflat surface inside of the daylight loader). On top ofthe film, place a coin or other opaque object which in-completely covers the film. Allow it to remain in placefor at least five minutes (this is presumed to representthe maximum time during which a film may be ex-posed to these conditions during normal processing).Following this interval, process the film using normaltechnique. If there are any light leaks from safelightdefects or breaches in darkroom integrity, the area offilm not under the coin will have been sensitized andappear to have an increased density after processing(Figure 6).
DiscussionThere are a number of reasons for developing qual-
ity assurance programs in dental radiography. Prior to1974, there were no requirements for machine perform-ance8 and the operating stability of many x-ray gener-ators in use today is uncertain. Studies have shownthat there are a variety of types of machine malfunc-tion which may occur as a result of use and aging.9.10
There is evidence to suggest that sight development isa common practice used to compensate for inadequatemachine performance, inadequate operator training,or defective processing chemistry.11 In a recent paper,we described how a quality assurance program may behelpful in minimizing patient exposure and radiationrisk.12 There is also an economic incentive for reducingthe number of retakes through a quality assurance
''Base plus fog: The amount of light attenuation which occurs whenlight passes through the celluloid backing plus any increased den-sity due to sensitization of the emulsion of the x-ray film.
cExpired unexposed film or other discarded film can be sold forsalvage because of their high silver content.
program which also minimizes the expenditure forlabor and materials13. In addition, serious liability canresult from mis-diagnosis caused by poor radiographs.
Governmental intervention in this area is becominga more likely possibility. Several states, such asIllinois,14 have established maximum allowable expos-ures for diagnostic x-ray procedures. The Commis-sioner of the Food and Drug Administration has re-cently proposed recommendations for the implemen-tation of quality assurance programs in all diagnosticradiology facilities including private dental offices.15
Several studies were cited by the F.D.A. as part of itsproposed recommendation. The first citation referredto information obtained from an examination of ra-diographs submitted to the National Institute of Oc-cupational Safety and Health under its pneumoco-niosis compensation program.16 Although facilitiesparticipating in this program were screened, Trout etal. found that 44% of the participating units had from10 to 40% of their radiographs rejected as being of in-adequate quality for the diagnosis of pneumoconiosis.
A second study by Beideman et al. examined pre-authorization dental radiographs submitted to thePennsylvania Blue Shield.17 A preliminary assessmentof these radiographs found that at least 50% of thefilms were not adequate as a basis for evaluating pro-posed treatment plans. The Food and Drug Admin-istration pointed out two consequences of poor qualityimages. In the first case, a suboptimal image deniesthe practitioner the full extent of diagnostic informa-tion that should be available. In the second case, thepatient may receive unproductive radiation exposuresas a result of radiographs which must be repeated.
The F.D.A. concluded that a considerable numberof inadequate films resulted from processing failures,and it estimated that a dose reduction to active bonemarrow could range from 209,000 to 330,000 rems an-nually by reducing the number of repeated radio-
Figure 6: Test film showing result of exposure by darkroom light
leak.
PEDIATRIC DENTISTRY
Volume 3, No. 1 31
graphs in hospitals alone. The F.D.A. also estimatedthat elimination of retakes in non-hospital facilitieswould significantly add to this total, as would theelimination of unnecessary radiation exposure due toinappropriate films produced in both hospitals andprivate offices and clinics.
There are a number of programs which have at-tempted to improve radiologic practices in dentistry.The Dental Exposure Normalization Technique{DENT) programd is a federal project, managed byparticipating states, which is based on consultationwith dentists to identify causes of excessive exposureand to suggest corrective actions which have beenshown to effectively reduce the exposures.18 TheNashville Dental Project proved the effectiveness ofan educational approach for voluntary improvementof radiographic practice. Survey data were collectedon 110 x-ray units (72 dental offices) in Nashville,Tennessee in 1972. Dental consultants visited theoffices two months later to present the findings and todemonstrate techniques which would improve radio-graphic practice. In 1973, a follow-up survey was con-ducted to determine the effectiveness of the consulta-tion visits. Average exposures were reduced from 472mR/film in 1972 to 311 mR/film in 1973.19
In another Nashville study, Johnson and co-work-ers surveyed a number of dental offices to determinethe reasons for high skin exposures. They found thatalthough the dental x-ray generators surveyed were ingeneral compliance with recommended standards, theoverexposure was the result of dentists failing to useproper processing techniques20.
Summary
We have described a quality assurance program forcommon intraoral d~ntal x-ray generators and tradi-tional modes of film processing. Practitioners who per-form extraoral radiographic examinations will need toidentify other test procedures to deal with the use ofintensifying screens, cassettes, and adjustable collima-tors21,22.
Dr. Valachovic was assistant professor, Dr. Reiskin is professor,and Ms. Kirchhof is st~ff radiologic technologist at the Universityof Connecticut School of Dental Medicine, Division of Oral Radiol-ogy, Farmington, Connecticut. Requests for reprints should be sentto Dr. Valachovic who is now Research Fellow in Dental Care Ad-ministration, Harvard School of Dental Medicine, 188 LongwoodAvenue, Boston, Massachusetts 02115.
References
1. Nelson, R. E., Barnes, G. T., and Whitten, D. M.: "Economicanalysis of a comprehensive quality assurance program," RadiolTechnol, 49:129-134, 1977.
dDentists wishing to utilize the services of the DENT programshould contact their own states’ Departments of Radiation Con-trol or other appropriate agencies.
RADIOLOGY QUALITY ASSURANCE PROGRAM32 Valachovic, Reiskin, and Kirchhof
2. Goldman, L. and Vucich, J. J.: "Automatic processing Q.A.:impact on a radiology department," Radio1, 125:591-595, 1977.
3. Bureau of Radiological Health: "Fast film exposure and proc-essing in dental radiography," DHEW Publ. No. (FDA) 78-8039, Supt of Documents, Govt Print Off, 1978.
4. Gray, J. E.: "Photographic quality assurance in diagnosticradiology, nuclear medicine and radiation therapy," DHEWPubl. No. (FDA) 76-8043, Supt of Documents, Govt Print Off,1976.
5. Starchman, D. E., Johnson, R. G. and Howland, W. J.:"Linearity of exposure with indicated time and current for
¯ diagnostic radiography units," RadioI, 122:489-492, 1977.6. National Council on Radiation Protection and Measurements:
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7. A.N.S.I.: "Reg. U.S. Pat. Off. PH6.2-1970 (Rev. of PH6.2-1961)," Approved March 3, 1970 by the American NationalStandards Institute, Inc.
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