Table Of ContentRadiation Exposure and Image Quality
in X-Ray Diagnostic Radiology
Horst Aichinger (cid:129) Joachim Dierker
€
Sigrid Joite-Barfuß (cid:129) Manfred Sabel
Radiation Exposure and
Image Quality in X-Ray
Diagnostic Radiology
Physical Principles and Clinical Applications
Second Edition
Authors
Dr.HorstAichinger Dr.JoachimDierker
UnterfarrnbacherStr.32 Hegenigstr.56
90766Fu¨rth 91056Erlangen
Germany Germany
[email protected] [email protected]
Dipl.Phys.SigridJoite-Barfuß Prof.Dr.ManfredSa¨bel
Friedhofstr.4a Universit€atsklinikumErlangen
91058Erlangen RadiologischesInstitut
Germany Maximiliansplatz1
[email protected] 91054Erlangen
Germany
[email protected]
ISBN978-3-642-11240-9 e-ISBN978-3-642-11241-6
DOI10.1007/978-3-642-11241-6
SpringerHeidelbergDordrechtLondonNewYork
LibraryofCongressControlNumber:2011928414
#Springer-VerlagBerlinHeidelberg2012
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Preface to the 1st Edition
X-raydiagnosticradiologyisamajorworld-wideactivity.InEuropeapproximately250million
X-rayexaminationsareperformedannually,andintheUnitedStatesofAmericaasimilarlevel
of radiological activity is undertaken. This results in the fact that the largest contribution
to radiation exposure to the population as a whole is known to be from man made
radiation sources arising in the form of diagnostic X-rays (UNSCEAR 2000). It is also
known that exposures vary widely, due to differences in X-ray techniques and the level of
skill of the operator of the equipment. Consequently radiation protection of the patient is a
major aim in modern health policy. The two basic principles of radiation protection of the
patient as recommended by the International Commission on Radiological Protection
(ICRP 1991) are justification of practice and optimisation of protection.
Justification is the first step in radiation protection. It is generally accepted that no
diagnostic exposure is justifiable without a valid clinical indication. In comparison to the
associated radiation risk, every examination must result in a net benefit for the patient.
Justification also implies that the necessary result cannot be achieved with other methods
whichwouldbecombinedwithlowerrisksforthepatient.
OnceadiagnosticX-rayexaminationhasbeenclinicallyjustified,thesubsequentimaging
processmustbeoptimised.TheoptimaluseofX-raysinvolvestheinterplayofthreeimportant
aspectsoftheimagingprocess(CEC1996):
(cid:129) Thediagnosticqualityoftheradiologicalimage
(cid:129) Theradiationdosetothepatient
(cid:129) Thechoiceofimagingtechnique
Inrespect ofdiagnostic radiology, the ICRP does notrecommend the application ofdose
limitstopatientirradiationbutdrawsattentiontotheuseofdosereferencelevelsasanaidto
optimisationofprotectioninmedicalexposure.
The principles of justification and optimisation are largely translated into a legal frame-
work by the Medical Exposure Directive (MED) 97/43/Euratom (CEC 1997). Concerning
optimisationtheMEDstatesexplicitlyinArticle4,1(a)that:
(cid:129) ‘All doses due to medical exposure for radiological purposes, except radiotherapeutic
procedures, shall be kept as low as reasonably achievable consistent with obtaining the
requireddiagnosticinformation,takingintoaccounteconomicandsocialfactors’.
ThisconceptisknownastheALARAprinciple(aslowasreasonablyachievable).
InArticle4,2.(a)theMEDstatesthat:
(cid:129) ‘MemberStatesshallpromotetheestablishmentandtheuseofdiagnosticreferencelevels
forradiodiagnosticexaminations’.
DiagnosticreferencelevelsaredefinedinArticle2oftheMEDas:
(cid:129) ‘Dose levels in medical radiodiagnostic practices for typical examinations for groups of
standard-sizedpatientsorstandardphantomsforbroadlydefinedtypesofequipment.These
levels are expected not to be exceeded for standard procedures when good and normal
practiceregardingdiagnosticandtechnicalperformanceisapplied’.
v
vi Prefacetothe1stEdition
The authors of this book have been engaged for a long time in the solution of problems
concerning optimisation in X-ray diagnostic radiology, three of us (Aichinger, Dierker,
Joite-Barfuß) as physicists in development working groups of Siemens Medical Solutions
andone(S€abel)asamedicalphysicistinauniversityhospital.Duringthistimealotofdata
material have been accumulated, which could be useful for physicists and engineers in the
medicalradiodiagnosticindustry,formedicalphysicistsandfordiagnosticradiologistswork-
ingatproblemsofimagequality,patientdoseestimationandespeciallytheestablishmentof
diagnosticreferencelevels.InthisconnexionthepublicationoftheMEDwasthetriggerpoint
forourdecisiontocollectandpublishthismaterial.
Inparticularthefiguresandtablesincludedshouldenableamedicalphysicistto:
(cid:129) Calculatethescatter-freecharacteristicquantitiesoftheprimaryradiationbeam
(cid:129) Estimatepatientdoses(organdose,effectivedose)
(cid:129) Optimise radiographic and fluoroscopic exposure parameters in relation to the medical
indication
(cid:129) Takeintoaccounttheinfluenceofscatteredradiationonimagequalityanddose
The data provided for the solution of these tasks are partly based on X-ray spectra,
measured on diagnostic X-ray tube assemblies, and supplemented by the results of
measurementsonphantomsandsimulationcalculations.
Takinginto consideration thatmammographyscreeningis increasingly establishedX-ray
mammographyistreatedinsomedetail.Ontheotherhand,concerningcomputedtomography,
thepresentationisconfinedtotheaspectofdoseestimation.Anessentialreasonforthisisthat
one ofour colleagues (Kalender 2000) has written anexcellentbook on computed tomogra-
phy,whichcoverstheaspectofimagequalityindetail.
Ourbookconsistsofthreeparts:
(cid:129) The ‘Physical Principles’ reviews some information on radiation physics, dosimetry and
X-ray diagnostic technique, which will be useful for the understanding of the figures and
tables, but it is not intended to replace standard books on the physics of diagnostic
radiology.
(cid:129) In the ‘Clinical Applications’ the material presented is applied to some clinical problems
concerning radiation exposure of the patient, image quality and optimisation of imaging
equipment.
(cid:129) The ‘Supplement’ includes all the figures and tables, which are necessary for the
calculations. It is complimented by a CD-ROM that includes the most important data of
the‘Supplement’andalotofadditionalusefulfiles.
A detailed description of the contents of the different parts of the book is given in the
following‘Introduction’.
In the preparation of this book we asked for and received the help of a number of well-
qualified people: We are grateful to John H. Hubbell, Ph.D., from the National Institute of
StandardsandTechnology,Gaithersburg,USA,forhissupportintheselectionofthemostup-
to-datephotoninteractioncoefficientsandtoG.T.Barnes,Prof.Ph.D.,fromtheUniversityof
AlabamainBirmingham,USA,forinformationinrespecttohisworkaboutscatteredradiation
in mammography. Moreover we thank Tassilo v. Volkmann, Ph.D. from Kodak for the
provision of the data of screen-film combinations and M.A.O. Thijssen, Ph.D. from the
University Hospital in Nijmegen, Netherlands, for information about his CDRAD-phantom.
LastbutnotleastwethankI.Aichingerforherpreparationofsomeofthefiguresinthisbook.
HorstAichinger
JoachimDierker
SigridJoite-Barfuß
ManfredS€abel
Prefacetothe1stEdition vii
References
CEC(CommissionoftheEuropeanCommunities)1996.EuropeanGuidelinesonQualityCriteriaforDiag-
nosticRadiographicImages.EUR16260(Luxemburg:CEC)
CEC(CommissionoftheEuropeanCommunities)1997.CouncilDirective97/43/EURATOMof30June1997
onhealthprotectionofindividualsagainstthedangersofionisingradiationinrelationtomedicalexposure,
OfficialJournaloftheEuropeanCommunities,NoL180/22
ICRP (International Commission on Radiological Protection) 1991. 1990 Recommendations of the ICRP,
Publication60,AnnalsoftheICRP21No.1–3(NewYork:PergamonPress)
KalenderWA(2000)ComputedTomography.(M€unchen:PublicisMCD)
UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) 2000. Sources and
EffectsofIonizingRadiation.(NewYork:UnitedNations)
Preface to the 2nd Edition
Sincethepublicationofthefirsteditionin2004X-rayimaginghasbecomealmostcompletely
digitalinmoderndiagnosticradiologyinstitutes.OntheothersidetherearestillalotofX-ray
unitsinoperationwhichusefilm-screencombinationsforradiographyandimageintensifiers
for fluoroscopy. Therefore we have decided to leave the concerning material in the book
essentially as it was. Furthermore for the full understanding of the new potentials in digital
imaging,i.e.theadvantagesandfurtherdevelopmentpossibilitiesbutalsothecomplexity,the
knowledge of the physics in conventional imaging is of great importance. In addition the
frequency of computed tomography increases still rapidly, and – because it involves larger
radiationdosesthanmostoftheconventionalimagingprocedures–obtainsgrowingattention
also in radiation protection. Accordingly we have added to this edition some facts on the
principlesofCTimaging.
Indetailthefollowingimprovementshavebeencarriedout:
(cid:129) More detailed consideration of the aspects of image quality and radiation exposure in
digitalimagingandcomputedtomography
(cid:129) Actualisationofthecitedreferences
(cid:129) Removalofobsoletetextpassages,figuresandtables
(cid:129) Correctionofdiscoveredprintingerrors
We are grateful to Elke Nekolla, Ph.D., from the German Federal Office for Radiation
Protection for placing Fig. 1.1 to our disposal. Furthermore we are grateful to Dr. Helmuth
Schramm from Siemens Medical Solutions for his information about the functioning of
fluoroscopywhenusingaflatpanelimagereceptorinmodernX-rayequipments.
HorstAichinger
JoachimDierker
SigridJoite-Barfuß
ManfredS€abel
ix
