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Guidelines for Patient RadiationDose ManagementMichael S. Stecker, MD, Stephen Balter, PhD, Richard B. Towbin, MD, Donald L. Miller, MD, Eliseo Vañó, PhD,
Gabriel Bartal, MD, J. Fritz Angle, MD, Christine P. Chao, MD, Alan M. Cohen, MD, Robert G. Dixon, MD,Kathleen Gross, MSN, RN-BC, CRN, George G. Hartnell, MD, Beth Schueler, PhD, John D. Statler, MD,Thierry de Baère, MD, and John F. Cardella, MD, for the SIR Safety and Health Committee and the CIRSEStandards of Practice Committee
J Vasc Interv Radiol 2009; 20:S263–S273
Abbreviations: ACR � American College of Radiology, FDA � Food and Drug Administration
THE membership of the Society of In-terventional Radiology (SIR) Safety andHealth Committee represent experts ina broad spectrum of interventional pro-cedures from both the private and aca-demic sectors of medicine. Generally,these Committee members dedicate thevast majority of their professional timeto performing interventional proce-dures; as such, they represent a validbroad expert constituency of the subjectmatter under consideration.
Technical documents specifying theexact consensus and literature review
From the Department of Angiography & Interven-tional Radiology, Brigham & Women’s Hospital,Boston, Massachusetts (M.S.S.); Department of Med-icine and Radiology, Columbia University MedicalCenter, New York, New York (S.B.); Department ofRadiology, Phoenix Children’s Hospital, Phoenix,Arizona (R.B.T.); Department of Radiology and Ra-diologic Sciences, Uniformed Services University ofthe Health Sciences, Bethesda, Maryland (D.L.M.);Department of Radiology, National Naval MedicalCenter, Bethesda, Maryland (D.L.M.); Radiology De-partment, Medicine School, Complutense Univer-sity, Madrid, Spain (E.V.); Department of Radiology,Meir Medical Center, Kfar Saba, Israel (G.B.); De-partment of Radiology, University of VirginiaHealth System, Charlottesville, Virginia (J.F.A.); De-partment of Radiology, Kaiser Medical Center, SanRafael, California (C.P.C.); Department of Vascular/Interventional Radiology, University of Texas,Houston, Texas (A.M.C.); Department of Radiology,University of North Carolina, Chapel Hill, NorthCarolina (R.G.D.); Greater Baltimore Medical Cen-ter, Owings Mills, Maryland (K.G.); Department ofRadiology, Cooley Dickinson Hospital, Northamp-
ton, Massachusetts (G.G.H.); Medical Physics Divi-sion, Department of Radiology, Mayo Clinic, Roch-methodologies as well as the institu-tional affiliations and professional cre-dentials of the authors of this docu-ment are available upon request fromSIR, 3975 Fair Ridge Dr, Ste 400 North,Fairfax, VA 22033.
METHODOLOGY
The SIR produces its safety-relateddocuments using the following process.Documents of relevance and timelinessare conceptualized by the Safety andHealth Committee members. A recog-
ester, Minnesota (B.S.), Department of Radiology,Mary Washington Hospital, Fredericksburg, Vir-ginia (J.D.S.); Radiologie Interventionnelle, InstitutGustave Roussy, Chevilly–Larue, France (T.d.B.);and the Department of System Radiology, GeisingerHealth System, Danville, Pennsylvania (J.F.C.). Re-ceived February 24, 2009; final revision receivedApril 1, 2009; accepted April 2, 2009. Address cor-respondence to M.S.S., c/o Debbie Katsarelis, 3975Fair Ridge Dr, Ste 400, North Fairfax, VA 22033;E-mail: [email protected]
From the 2009 SIR annual meeting.
The opinions expressed herein are those of the au-thors and do not necessarily reflect those of theUnited States Navy, the Department of Defense, orthe Department of Health and Human Services.None of the authors have identified a conflict ofinterest.
Research funded wholly or in part by Rex Medicalfor M.S.S. J.F.A. has been a speaker for Siemens.
© SIR, 2009
DOI: 10.1016/j.jvir.2009.04.037
nized expert is identified to serve as theprincipal author for the document. Ad-ditional authors may be assigned de-pendent upon the magnitude of theproject.
An in-depth literature search is per-formed by using electronic medical lit-erature databases. Then, a critical re-view of peer-reviewed articles andregulatory documents is performedwith regard to the study methodology,results, and conclusions. The qualitativeweight of these articles is assembled intoan evidence table, which is evaluatedand used to write the document suchthat it contains evidence-based data,when available.
When the literature evidence isweak, conflicting, or contradictory, con-sensus is reached by a minimum of 12Safety and Health Committee members.A Modified Delphi Consensus Method(Appendix A [1]) is used when neces-sary to reach consensus. For purposes ofthese documents, consensus is definedas 80% Delphi participant agreement ona value or parameter.
The draft document is critically re-viewed by the Safety and Health Commit-tee members, either by means of tele-phone, conference calling, or face-to-facemeeting. The finalized draft from theCommittee is sent to the SIR member-ship for further input and criticism dur-ing a 30-day comment period. Thesecomments are discussed by the Safetyand Health Committee, and appropriaterevisions are made to create the finished
document. Before its publication, theS263
S264 • Guidelines for Patient Radiation Dose Management July 2009 JVIR
document is endorsed by the SIR Exec-utive Council.
INTRODUCTION
In the early 1990s, the U.S. Food andDrug Administration (FDA) received re-ports of significant radiation-inducedskin injuries associated with interven-tional fluoroscopy (2), prompting the re-lease in 1994 and 1995 of three guidancepublications on documenting radiationuse (3–5). A number of professional ra-diological societies, including the SIR,have been working since then to reducethe frequency of these events. In 2007,the American College of Radiology(ACR) published its recommendationson issues related to patient radiation ex-posure in medicine. This document fo-cuses mostly on diagnostic imaging pro-cedures, such as computed tomography(CT) and nuclear medicine, and not in-terventional procedures (6). The ACR’s2008 revision of the Technical Standardpertaining to the management of the useof radiation in fluoroscopically guidedprocedures (7) takes a different, butcomplementary, approach to the topicthan that used in this SIR guideline. Flu-oroscopically guided invasive proce-dures may require the use of significantquantities of radiation for their comple-tion. This can put patients at risk fordeterministic radiation injuries. In addi-tion, all irradiated patients are at risk foran increased incidence of stochastic in-juries.
These guidelines are written to beused for radiation dose management re-lated to interventional radiologic proce-dures. The most important processes ofcare are (a) patient selection, (b) proce-dure performance, (c) patient monitor-ing, and (d) appropriate documentationand follow-up. The outcome measuresor indicators for these processes are in-dividualized patient radiation risk as-sessment, appropriate informed consentrelating to radiation risk, and compli-ance with recording administered dose.
Concerns over patient radiationdoses are valid. Nonetheless, it must beclearly understood that the goal of allinterventional radiology procedures isto treat patients and thereby improvetheir well-being. This will almost alwaysrequire administration of some radia-tion and may sometimes require the ad-ministration of clinically significantamounts of radiation. In general, the
risk of radiation is low compared toother procedural risks, and the benefitsof imaging guidance are great (8). Im-age-guided procedures typically causeless morbidity and mortality than theequivalent surgical procedure. An in-formed patient will virtually alwaysagree that the potential harm due to ra-diation is less than the potential harmdue to a procedure that is cancelled, in-complete, or clinically inadequate be-cause of concerns over radiation.
DEFINITIONS
Absorbed Dose
The energy imparted per unit massby ionizing radiation to matter at a spec-ified point. The International System ofUnits (SI) unit of absorbed dose is thejoule per kilogram. The special name forthis unit is the gray (Gy). For purposesof radiation protection and assessingdose or risk to humans in general terms,the quantity normally calculated is themean absorbed dose in an organ or tis-sue.
Air Kerma
The energy extracted from an x-raybeam per unit mass of air in a smallirradiated air volume. Air kerma ismeasured in grays. For diagnostic ra-diographs, air kerma is the dose deliv-ered to that volume of air.
Biologic Variation
With respect to radiation, the differ-ences among individuals in the thresh-old dose required to produce a deter-ministic effect or the differences indegree of effect produced by a givendose. Biologic variation may be idio-pathic, due to underlying disease, ordue to patient age. The skin on differ-ent parts of the body and differentskin types vary in radiosensitivity (9).
C-arm Fluoroscopic System
A fluoroscopic system consisting of amechanically coupled x-ray tube andimage receptor. Such systems typicallyhave two rotational degrees of freedom(left-right and cranial-caudal). Most ofthese systems have an identifiable cen-ter of rotation called an isocenter. Anobject placed at the isocenter remainscentered in the beam as the C-arm is
rotated. C-arm fluoroscopes may haveeither fixed or variable source-to-imagereceptor distance. Radiation protectionstrategies differ for these differentclasses of systems.
Cumulative Dose (CD)
See Reference point air kerma.
Deterministic Effect
Detrimental health effect for whichthe severity varies with the dose ofradiation, and for which a thresholdusually exists (ie, causally determinedby preceding events). The effect is notobserved unless the threshold is ex-ceeded, although the threshold dose issubject to biologic variation. Once thethreshold dose is exceeded in an indi-vidual, the severity of injury increaseswith increasing dose. Examples of de-terministic effects include skin injury,hair loss, and cataracts.
Dose
General term used to denote meanabsorbed dose or effective dose. Theparticular meaning of the term shouldbe clear from the context in which it isused. In this document “dose” meansthe absorbed dose to tissue unless oth-erwise specified.
Dose-Area-Product (DAP)
See Kerma-area-product.
Effective Dose (E)
The sum, over specified tissues, ofthe products of the dose in an organand the tissue weighting factor for thattissue. Current techniques for estimat-ing effective dose use computer simu-lation based on a “model” body andstatistical simulations of radiation ex-posure. This yields only a gross approx-imation of effective dose. The stochasticrisk to an average member of an irradi-ated population is expressed in terms ofsieverts (Sv). Effective dose is often usedin the literature to roughly estimate theradiogenic risk to an individual. Ageand sex modifiers, appropriate to theirradiated individual, should be applied
to such calculations.
Stecker et al • S265Volume 20 Number 7S
Fluorographic Image
A single recorded image obtainedby using an image intensifier or digitalflat panel as the image receptor. A dig-ital angiographic “run” consists of aseries of fluorographic images.
Fluoroscopy Time (FT)
The total time that fluoroscopy isused during an imaging or interven-tional procedure.
Interventional Reference Point (IRP)
For isocentric fluoroscopic sys-tems, the interventional referencepoint is located along the central x-ray beam at a distance of 15 cm fromthe isocenter in the direction of thefocal spot (10,11). The interventionalreference point is close to the pa-tient’s entrance skin surface. TheFDA prescribes the location of theinterventional reference point forseveral non-isocentric geometries(11).
Isocentric Fluoroscopic System
An imaging system in which there isa point in space through which the cen-tral ray of the x-ray beam passes regard-less of beam orientation. This point iscalled the isocenter. An object placed atthe isocenter will not move across thefield of view as the imaging system isrotated.
Kerma
Kinetic energy released in matter;the energy extracted from an x-raybeam per unit mass of a specified ma-terial in a small irradiated volume ofthat material (eg, air, soft tissue, bone).Kerma is measured in grays. For thex-ray energies covered in this report,the kerma produced in a small vol-ume of material delivers its dose tothe same volume (which is not truein high-energy radiation therapy).
Kerma-Area-Product (PKA)
The integral of air kerma across theentire x-ray beam emitted from the x-ray tube. Kerma-area-product is a sur-rogate measurement for the entireamount of energy delivered to the pa-
tient by the beam. Kerma-area-productis measured in Gy · cm2. Conversionfrom units reported by commonly usedequipment are given in Table 1. Kerma-area-product is usually measured with-out scatter. This quantity was previ-ously called dose-area-product. Earlierpublications used the abbreviations‘KAP’ and ‘DAP’ for this quantity.
Peak Skin Dose (PSD)
The highest dose at any portion of apatient’s skin during a procedure. Peakskin dose includes contributions fromboth the primary x-ray beam and fromscatter. Peak skin dose is measured ingrays (to soft tissue).
Qualified Medical Physicist
An individual who is competent topractice independently one or more ofthe subfields of medical physics. TheACR recommends that the individualbe certified in the appropriate sub-field(s) by the American Board of Radi-ology in Diagnostic Radiological Phys-ics or Radiological Physics (7). Themedical physicist must also be familiarwith the relevant clinical procedures.
Reference Point Air Kerma (Ka,r)
The air kerma accumulated at a spe-cific point in space relative to the fluo-roscopic gantry (see interventional ref-erence point above) during a procedure.Reference point air kerma does not in-clude backscatter and is measured ingrays. Reference point air kerma issometimes referred to as reference dose,cumulative dose, or cumulative airkerma. Earlier publications used the ab-breviations ‘CD’ and ‘RPDose’ for thisquantity.
Significant Radiation Dose
A selected threshold value that is
Table 1Kerma-area-product Unit Conversion
Unit Used To Convert to Gy · cm2
dGy · cm2 divide by 10cGy · cm2 divide by 100mGy · cm2 divide by 1,000�Gy · m2 divide by 100
used to trigger additional dose manage-
ment actions. There is no implicationthat a dose below the significant doselevel is safe or that a dose above thesignificant dose level will always causean injury.
Stochastic Effect
A radiation effect whose probabil-ity of occurrence increases with in-creasing dose but whose severity isindependent of total dose. Radiation-induced cancer is an example.
Threshold Dose
The minimum radiation dose atwhich a specified deterministic effectcan occur. Threshold doses differamong individuals as a result of biologicvariation. The threshold dose for skininjury also differs in different anatomicsites on the same individual.
BACKGROUND
Interventional radiology differs fromdiagnostic imaging in that interven-tional radiology procedures are gener-ally therapeutic, thus shifting the risk-benefit ratio for radiation exposure.However, the radiation dose for someinterventional procedures may be sev-eral orders of magnitude greater thanthat for simple radiographic studies. Amajor intervention, such as transcathe-ter embolization, can deliver an effectivedose to the patient of 100 mSv, whereasa typical chest radiograph delivers 0.1mSv. This can often be reduced if theoperator adheres to the principle ofALARA (as low as reasonably achiev-able) (12).
Deterministic injuries occur only af-ter the radiation dose to the tissue ex-ceeds a given threshold dose. In inter-ventional fluoroscopy procedures, thetissue of concern is the skin—althoughthe lens of the eye is another consid-eration. The skin at the site where ra-diation enters the body receives thehighest radiation dose of any body tis-sue. Once the threshold dose is ex-ceeded, the injury becomes progres-sively more severe with increasingdose, although the true severity of ma-jor injuries will only become apparentweeks to months after the procedure(Table 2). Very high doses usuallyproduce some symptoms within 24hours of the procedure.
The incidence of deterministic in-
S266 • Guidelines for Patient Radiation Dose Management July 2009 JVIR
juries increases with increasing bodymass, the nature and complexity ofthe procedure, the radiation historyof the patient, the presence of otherdisease processes (eg, diabetes melli-tus), individual idiosyncrasy, andpossibly other factors. The actual riskfor major radiation injury is unknown.Based on estimates in the literatureand reports to the FDA, the frequencyis estimated to be between 1:10,000and 1:100,000 procedures (14).
It should also be noted that pro-longed fluoroscopy/fluorography witha peak skin dose greater than 1,500 rads(15 Gy) to a single field over a period of6 months to 1 year is a reviewable sen-tinel event as mandated by the JointCommission (15,16). The American As-sociation of Physicists in Medicine is
Table 2Deterministic Effects of Single-delivery
Band
Single-siteAcute
Skin DoseRange(Gy)*
NationalCancer
InstituteSkin
ReactionGrade Prompt (�2
A1 0–2 NAA2 2–5 1 Transient eryB 5–10 1 Transient ery
C 10–15 1–2 Transient ery
D �15 3–4 Transient eryAfter verydoses, edemand acuteulceration;term surgicinterventiolikely to berequired
Note.—This table is applicable to the norphysical or clinical factors. Abrasion or inapply to the skin of the scalp. The dose aearlier as the skin dose increases. NA � n* Skin dosimetry is unlikely to be more a† Refers to radiation-induced telangiectasulceration, may be present earlier.
working to have the definition of this
sentinel event modified because theJoint Commission defines a sentinelevent as an “unexpected” (15) outcomeand implies that a reviewable radiationoverdose is “preventable” (16). In somecircumstances, a planned interventionmay require a sufficient dose of radia-tion to reach the Joint Commission’sthreshold for a sentinel event in order toachieve a life-preserving outcome—especially if the patient has had multiplefluoroscopically guided procedures orradiation therapy in the recent past,with radiation delivered to the samearea of skin (17).
Although much of radiation dosemanagement is based on sequelae thatcan be seen, albeit delayed weeks tomonths, stochastic effects must also beconsidered. The likelihood of stochastic
diation Dose to the Skin of the Neck, To
Approximate Time of Ons
k) Early (2–8 wk) Midterm (6
No observable effects ema Epilation Recovery from hma Erythema, epilation –Recovery
–At higher doseserythema, permpartial epilatio
ma –Erythema,epilation
–Possible dry ormoistdesquamation
–Recovery fromdesquamation
–Prolonged eryth–Permanent epil
mah
g-
–Erythema,epilation
–Moistdesquamation
–Dermal atrophy–Secondary ulcer
to failure of mdesquamationsurgical intervlikely to be req
–At higher dosesnecrosis; surgiintervention lirequired
l range of patient radiosensitivities in the ation of the irradiated area is likely to exactime bands are not rigid boundaries. Signapplicable. Adapted from reference 13.rate than �50%.Telangiectasia associated with an area of i
effects increases with the total radiation
energy applied to the patient. The prin-cipal injury is the induction of a malig-nancy. The probability of a radiation-induced malignancy caused by aninvasive procedure is small comparedto the “natural” frequency of malignan-cies. Based on published data, the fre-quency of fatal malignancy in the U.S.population is about 21% (18). With useof the linear no-threshold model, a typ-ical interventional procedure is esti-mated to increase the risk of developinga fatal cancer by less than 0.5% in adults(estimating a worst-case effective doseof 100 mSv, which is multiplied by a riskof 5% per Sv [19]), assuming a normallife span. The probability of a new (non-radiation-induced) malignancy beingdiagnosed in the next 10 years is about16.5% for a 60-year-old man (18). The
, Pelvis, Buttocks, and Arms
f Effects
wk) Long Term (�40 wk)
ectedloss None expected
rolongedent
–Recovery–At higher doses, dermal
atrophy and/or induration
an
–Telangiectasia†–Dermal atrophy and/or
induration–Skin likely to be weak
on duetheal;ionedermal
to be
–Telangiectasia†–Dermal atrophy and/or
induration–Possible late skin breakdown–Wound might be persistent
and progress into a deeperlesion
–Surgical intervention likelyto be required
nce of mitigating or aggravatingate radiation effects. This table does notd symptoms are expected to appear
al moist desquamation, or the healing of
Ra rso
et o
w –52
xpthe airthe
, pan
nthe em
atio
thehig
a
lonal
n
atioistoentuir, d
calkely
ma bsefec erbnd s anot
ccuia. niti
possible radiogenic increase is too small
Stecker et al • S267Volume 20 Number 7S
to be documented statistically in the en-tire worldwide interventional patientpopulation.
It is particularly important to includethe risk of stochastic effects in risk-ben-efit considerations when treating pedi-atric and young adult patients andwhen procedures involve substantialabsorbed dose to radiosensitive organs,such as thyroid, breast, or gonadal tis-sue (3,20). The risk of cancer induction iselevated in children relative to that ofadults because of their increased suscep-tibility to radiation and longer potentiallife span (21,22). The risk is approxi-mately three times higher for newbornsand declines to that of adults by themiddle of the 3rd decade of life (21).Hence, additional consideration must begiven to adolescent patients, who havean adult-sized body but a child’s ele-vated risk coefficients. However, otherthan embolization of congenital arterio-venous malformations, the risk to chil-dren is lessened because many of theprocedures performed on them are gen-erally lower in complexity. Further-more, children’s smaller body mass gen-erally results in lower doses—althoughin small children it is possible to imparta high dose to the whole body if poorcollimation technique is used.
New technology has allowed reduc-tion of both the fluoroscopic and fluoro-graphic dose rates without reduction inimage quality. However, the increas-ingly complex nature of many of theinterventions performed may negatethis technologic dose-rate savings, re-quiring the use of significant amounts ofradiation for their completion.
As of 2008, no manufacturer sells flu-oroscopic equipment capable of provid-ing real-time monitoring of peak skindose, although aftermarket methods forestimating peak skin dose are available(23,24). However, all equipment used inthe United States provides total fluoros-copy time, and many systems manufac-tured within the past 15 years havekerma-area-product measurement capa-bility. All equipment manufactured af-ter June 10, 2006, and sold in the UnitedStates must also provide air kerma rateat the interventional reference point andcumulative air kerma (11). For severalreasons, fluoroscopy time correlatespoorly with peak skin dose (25), but if itis the only measurement available, it isbetter than not monitoring at all. Refer-ence point air kerma correlates with
peak skin dose better than does kerma-area-product, although both referencepoint air kerma and kerma-area-prod-uct have wide variability for differentinstances of the same procedure (25,26).In the RAD-IR study (26), the linear re-gression between peak skin dose andreference point air kerma (Ka,r is re-ferred to in that document as CD) andthe linear regression between peak skindose and kerma-area-product (PKA is re-ferred to in that document as DAP)were as follows:
PSD �mGy� � 206 � 0.513 � Ka,r (mGy)
PSD �mGy� � 249 � 5.2
� PKA (Gy · cm2) �Note: the coefficient
has been changed to allow use
of the more standardized units
for kerma-area-product�.
It should be kept in mind that these“conversion formulas” are approxima-tions and not precise replacements foractually measuring the peak skin dose.Particularly, they are invalid below ref-erence point air kerma of about 500mGy and/or kerma-area-product ofabout 50 Gy · cm2, as the y-intercept wasnot forced to zero in the original calcu-lations. However, they may be used toestimate the peak skin dose by usingdata that are more readily available.
In addition, all statements of patientdose contain some degree of uncer-tainty. Even the most sophisticateddose-measurement instrumentation hasunavoidable uncertainties related tovariations in instrument response withchanges in beam energy, dose rate, andcollimator size. Converting these mea-surements into skin dose introduces yetfurther uncertainties related to the pa-tient’s size and position relative to thebeam. Finally, clinically available doseand kerma-area-product measurementsignore the effect of backscatter from thepatient. Backscatter can increase skindose 10%–40%, depending on the beamarea and energy. Estimated skin dosesmay differ from actual skin dose by afactor of two or more. Users of dose datashould be aware of these uncertainties.
Monitoring patient radiation dosemust also be performed during CT-guided interventions. In CT-guided pro-cedures, the initial localizing scan con-tributes the most to effective dose
because it is distributed over a largearea. Scans obtained during guidance ofthe needle, catheter, or probe are themain contributor to the peak skin dosebecause they are repeatedly performedin approximately the same location(27,28). The cross-sectional images forguidance are obtained with reduceddose settings, and each delivers a factorof 5–15 times less peak skin dose relativeto typical diagnostic scans.
CT fluoroscopy employs continuouslow-dose CT with real-time image re-construction and display. It generally in-creases patient radiation dose comparedwith conventional CT scans for guid-ance, where discrete scans are acquiredintermittently between manipulationsof the needle, catheter, or probe. How-ever, the dose is highly dependent onthe operator. The peak skin dose fromCT fluoroscopy– guided proceduresmay reach those from other interven-tional procedures (29). To date, reportsof skin effects due to CT are extremelyrare and have been associated with thecombination of repeated multidetectorCT studies and fluoroscopic proceduresin the same anatomic area (30).
The peak skin dose from CT per-formed without table incrementation isproportional to the tube current (in mil-liamperes) and exposure time (in sec-onds) and approximately proportionalto the square of the tube potential (kilo-volt peak), although this varies consid-erably between CT systems (31,32). Re-ducing any of these parameters willreduce peak skin dose, but imagequality may be adversely affected dueto an increase in image noise. Real-time dose monitoring uses indexes de-veloped for CT scans in which the pa-tient is translated through the x-raybeam and may overestimate the peakskin dose by a factor of up to two(31,33). This overestimated peak skindose and the total procedure time areshown on the in-room monitors of al-most all modern interventional CTsystems and may result in an addi-tional margin of safety for avoidanceof skin injury.
The effective dose from a CT-guidedinterventional procedure is a relativelycomplex calculation based on indexesderived from standard dosimetry phan-toms and specific to a particular scanner(31,32). It is not displayed on the systemand must be estimated by a qualifiedmedical physicist. Because the CT guid-ance scans cover a relatively thin section
of anatomy and are performed with
S268 • Guidelines for Patient Radiation Dose Management July 2009 JVIR
greatly reduced dose settings (eg, milli-ampere seconds), the initial diagnosticquality scan obtained to localize theanatomy of interest is the primary con-tributor to the total effective dose. Esti-mates of effective dose for typical CTexaminations can be found elsewhere(28,32).
SIR GUIDELINES
Radiation dose management requiresa comprehensive approach including pre-procedural planning, intraproceduralmanagement, and postprocedural care. Italso includes periodic quality assessment.
The informed consent process sup-plies patients, or their representatives,with sufficient information to make anappropriate decision regarding a pro-posed procedure. One purpose of thisguideline is to ensure that the radiationelements of this informed consent pro-cess are appropriately implemented.
Radiation data are available to theoperator during the course of a proce-dure. It is the operator’s responsibility tobe informed about dose levels and toinclude radiation dose in the continuousrisk-benefit balance used to determinethe value of continuing a procedure (8).When using a biplane system, eachplane is considered independently un-less the fields overlap, in which casedoses are additive.
Participation by the radiologist in thefollow-up of patients at risk is an inte-gral part of radiation dose management.Close follow-up, with monitoring andmanagement of radiation-induced in-jury or referral to another specialist, isappropriate for the interventional radi-ologist.
Preprocedural Planning
Individual training.—All operatorsshould meet institutional requirementsfor privileges to use fluoroscopy. Allnurses, technologists, and other person-nel shall receive initial training in pa-tient radiation management when be-ginning work in the interventionalradiology suite. All staff shall also re-ceive refresher training in radiationmanagement that should occur at leastannually. Radiation safety trainingshould be in accordance with institu-tional policy and governmental regula-tions and generally will include re-view of the potential adverse effects
of radiation on patients, operation ofthe institution’s fluoroscopic equip-ment, factors that affect patient dose,and measures that can be taken toreduce dose.
Equipment.—Rooms that are onlyequipped with fluoroscopy time moni-toring should be avoided for proceduresthat may result in significant radiationdose.
Patient consent.—Radiation risks as-sociated with interventional proceduresshould be discussed with patients aspart of the preprocedure consent pro-cess, particularly when the expecteddose of radiation may be high. Specifi-cally, but not exclusively, the followingprocedures have been associated withan increased occurrence of significantradiation dose (34):
• embolization (including chemo-embolization)
• renal and/or visceral angioplastyor stent placement
• transjugular intrahepatic portosys-temic shunt creation or revision
• complex biliary intervention• nephrostomy procedure for stone
access• complex, multilevel vertebral aug-
mentation procedures (includingvertebroplasty and kyphoplasty)
Radiation risks should also be dis-cussed when the following patient crite-ria are met, especially when one of theabove procedures is planned:
• weight less than 10 kg (22 lbs) orgreater than 135 kg (300 lbs)
• intervention in pediatric andyoung adult patients involvingsubstantial absorbed dose to radi-osensitive organs (eg, lens of eye,breasts, gonads, thyroid); exam-ples may include, among others,some embolization procedures, ve-nous recanalizations, cardiac inter-ventions, and some CT-guidedinterventions
• pregnancy• procedure anticipated to be techni-
cally difficult, unusually pro-longed, or that could, within a rea-sonable likelihood, result in a skindose metric that will require fol-low-up (eg, if the operator’s expe-rience is such that performance ofsimilar procedures has been asso-ciated with an average radiationmetric of 50% of the below-noted
patient follow-up thresholds)• radiation therapy has been used oris planned for the same anatomicregion
• procedures involving the use of ra-diation have been performed in thesame anatomic region within theprevious 60 days; previous irradi-ation should be reviewed in thecontext of the additional radiationthat the patient is likely to receive
If it is considered desirable to includespecific language in the consent form,the example given in Appendix B maybe used. It must be remembered thatinformed consent is more than just asigned document; it is an active processbetween the physician and patient. Asigned form without an adequately de-tailed dialogue is inadequate. Docu-mentation that the radiation risk discus-sion was conducted and understood bythe patient should be included in thepatient’s medical record. The patient’sprevious radiation exposure, includingradiation therapy, should also be con-sidered when planning the clinical ap-proach to the current procedure.
Procedure planning.—In the past, be-cause noninvasive diagnostic imagingmethods were inadequate for procedureplanning, interventional radiology pro-cedures traditionally comprised diag-nostic imaging followed by an interven-tion, all in the same session. This may nolonger be necessary as the quality ofdiagnostic imaging has greatly im-proved across all modalities. Preproce-dure imaging can assist in the planningof interventional radiology procedures,access routes, and selection of devices.All pertinent prior imaging studiesshould be reviewed and, when possible,outside images should be examinedfirst-hand instead of simply reviewingreports. When appropriate and feasible,utilization of noninvasive cross-sec-tional imaging modalities (eg, ultra-sonography, magnetic resonance [MR]imaging, MR angiography, MR cholan-giopancreatography, CT, multidetectorCT angiography) is recommended inthe work-up of interventional radiologypatients, with preferential use of imag-ing modalities that do not require theuse of ionizing radiation. When CT isemployed, there must be careful atten-tion to dose reduction for the diagnosticstudy to decrease total-patient radiationdose. Decreasing the tube voltage andusing automatic tube current modula-
tion can result in substantial dose reduc-
Stecker et al • S269Volume 20 Number 7S
tions without compromising diagnosticimage quality (35,36). Preprocedure di-agnostic imaging may reduce proceduretime and complication rates and reducefluoroscopy time and the number of flu-orographic images obtained.
Reconstructed images from MR an-giography and multidetector CT an-giography allow accurate depiction ofanatomy and treatment planning. It isfeasible to replace digital subtraction an-giography with cross-sectional imagingas the initial modality for the evaluationof peripheral arterial disease (37,38). Al-though it requires radiation, use of mul-tidetector CT angiography instead ofdigital subtraction angiography may re-sult in a reduced total radiation dose tothe patient (39). This must be balancedagainst the well-known limited abilityof multidetector CT angiography toevaluate the lumen of extensively calci-fied arteries (40). For evaluation of acutegastrointestinal bleeding, multidetectorCT angiography is a promising first-lineexamination that provides a time-effi-cient method for directing and planningpatient therapy (41). There is probablyalso value in preprocedural cross-sec-tional imaging for procedures such astransjugular intrahepatic portosystemicshunt creation (42), percutaneous accessfor renal stone disease (43), and complexbiliary interventions.
Finally, it must be understood thatradiation is only one consideration inprocedure planning. Other risks mustbe considered, such as adverse eventsdue to iodine- and gadolinium-basedcontrast agents, the potential for mis-leading, confusing, or nondiagnosticpreintervention imaging studies, and in-creased costs and lost time due to per-forming multiple tests. These issuesmust be carefully balanced for each in-dividual patient and each clinical
Table 3Summary of Radiation Monitoring Dose
Parameter Firs
Peak skin dose (PSD) 2,Reference point air kerma (Ka,r) 3,Kerma-area-product (PKA) 30Fluoroscopy time (FT) 30
* Assuming a 100-cm2 field at the patientactual procedural field size.
situation.
Intraprocedural Management
Procedural Radiation Monitoring.—Radiation dose is monitored throughoutthe procedure. This responsibility maybe delegated to a technologist, nurse orother personnel depending on the insti-tution’s policy and needs and in accor-dance with relevant laws and regula-tions. The following rules should beapplied in order of availability of radia-tion monitoring technology (Table 3):
• For fluoroscopy units that can pro-vide estimates of peak skin dose,the operator is notified when thisreaches 2,000 mGy, then every 500mGy after that.
• For units with reference point airkerma capability, initial notifica-tion is given at 3,000 mGy and thenevery 1,000 mGy thereafter. Giventhe formulas above, this corre-sponds to an initial peak skin doseof about 1,800 mGy and an incre-ment of about 500 mGy.
• For units with kerma-area-productcapability, the notification level isbased on a procedure-dependentnominal x-ray field size at the pa-tient’s skin. With use of a 100-cm2field, the initial report would be at300 Gy · cm2 and subsequently atincrements of 100 Gy · cm2. Giventhe formulas above, this corre-sponds to an initial peak skin doseof about 1,800 mGy and an incre-ment of about 500 mGy. Note thatdifferent brands of fluoroscopes re-port kerma-area-product using dif-ferent units; conversion factors aregiven above in Table 1 of the Def-initions section.
• For units that can only monitor flu-oroscopy time, the operator is no-tified when the total fluoroscopytime has reached 30 minutes and
otification Thresholds
otification Subsequent Notifications
mGy 500 mGymGy 1,000 mGyy · cm2* 100 Gy · cm2*
in 15 min
kin. The value should be adjusted to the
then in increments of 15 minutes or
less. Notification intervals shouldbe reduced for procedures that in-volve a relatively large number offluorographic images (includingdigital subtraction angiographyand cineangiography). All fluoro-scopes display fluoroscopy time.However, because of poor correla-tion with other dose metrics, itshould be used with caution tomonitor patient irradiation.
With regard to these notifications, theoperator should consider the radiationdose already delivered to the patientand the additional radiation necessaryto complete the procedure, along withother factors, in the continuing risk-benefit evaluation. It is understood thatit is unlikely that a procedure will bestopped purely because of radiationdose concerns, as the clinical benefit of asuccessful procedure almost always ex-ceeds any detriment to the patient dueto radiation. However, if any of theabove thresholds are met in the perfor-mance of a procedure, any dose for ad-ditional procedures performed withinthe subsequent 60 days should beclosely monitored and generally shouldbe considered additive to the dose al-ready received. As previously stated, bi-plane systems are a special situation.The dose received from each planeshould be considered independentlywhen the fields do not overlap. Whenthey do overlap the doses are additive.
Dose minimization techniques.—Throughout the procedure, the equip-ment should be operated at the lowestfluoroscopic dose rate that yields ade-quate images. Pulsed fluoroscopyshould be used, at the lowest pulse ratethat yields adequate image quality. Careshould be taken to use the least amountof fluoroscopic time and acquire theleast number of fluorographic imagesconsistent with achieving the clinicalgoals of the procedure. Appropriate col-limation should be used. The source-to-image receptor distance should be max-imized and the object-to-image receptordistance should be minimized. Imagemagnification (“zoom”) should be usedonly when essential clinically. C-arm an-gles should be varied from time to timeif this does not interfere with the con-duct of the clinical procedure, in orderto minimize skin dose (44). C-arm angu-lation is of increased importance oncethe operator receives the first dose
N
t N
0000000 Gm
’s s
notification.
S270 • Guidelines for Patient Radiation Dose Management July 2009 JVIR
For CT-guided procedures, dosecan be reduced by using low milli-ampere second techniques after ob-taining the localizing scan (27) aswell as by reducing the number ofsections acquired and increasing thepitch for spiral scans (28). Also, the“quick-check” method of CT fluoros-copy may offer reduced radiationdose compared to the “real-time”method (45).
Postprocedural Care
Dose documentation.—Estimated ra-diation dose is recorded in the medicalrecord, preferably the formal procedurereport, for every procedure. Existing SIRguidelines for recording patient radia-tion dose are followed (46). As detailedin that document, ideally the peak skindose and kerma-area-product are re-corded, as they are the most useful pre-dictors for deterministic and stochasticeffects, respectively. If peak skin dose isnot available on a fluoroscopic system,reference point air kerma is an accept-able substitute. If none of these otherparameters is available and fluoroscopytime is used as the radiation dose met-ric, recording the total number of fluo-rographic images acquired during theprocedure is also helpful for recon-structing the estimated dose. However,fluoroscopy time should not be used asthe only metric of estimated radiationdose if any of the others are available.
The operator is promptly notified ifany of the following occur: the finalpeak skin dose exceeds 3,000 mGy, thereference point air kerma exceeds 5,000mGy, the kerma-area-product exceeds500 Gy · cm2, or the fluoroscopy timeexceeds 60 minutes (Table 4). These val-ues are based on the dose conversionequations given above and on the rela-tionships between skin dose and skineffects given in Table 2. They are
Table 4Thresholds for Patient Follow-up
Parameter Threshold
Peak skin dose (PSD) 3,000 mGyReference point air
kerma (Ka,r)5,000 mGy
Kerma-area-product(PKA)
500 Gy · cm2
Fluoroscopy time (FT) 60 min
slightly less conservative than those
given in the 2008 ACR Technical Stan-dard (7), and those recommendationsmay be used instead, according to localpreferences. The values used in this SIRguideline are intended to trigger fol-low-up for a dose that might produce aclinically relevant injury in an averagepatient. The values used in the ACRdocument are intended to prompt fol-low-up for a dose that might result in aminor reaction in an average patient.
The operator writes an appropriatenote in the patient’s medical record ifany of these values are exceeded, signi-fying that a significant radiation dosehas been administered. Notation in themedical record may also be appropriateeven if these thresholds are not ex-ceeded, such as for patients on whomother procedures involving radiationexposure are planned or have alreadybeen performed within 60 days. In ad-dition, arrangements for radiation fol-low-up are made if any radiation dosemetric exceeds the thresholds givenabove.
Patient follow-up.—Patients receivinga significant radiation dose are followedup after the procedure. In this context, asignificant radiation dose is a selectedthreshold value that is used to triggeradditional dose management actions(47). For interventional radiology proce-dures in adults, a significant radiationdose is any of the following: a peak skindose greater than 3,000 mGy, a referencepoint air kerma greater than 5,000 mGy,or a kerma-area-product greater than500 Gy · cm2 (Table 4). A fluoroscopytime greater than 60 minutes is not itselfa dose value, but it is an indirect indica-tor of a significant radiation dose. Thereis no implication that a dose below thesignificant dose level is safe or that adose above the significant dose levelwill always cause an injury. In fact, itmay be desirable to perform follow-upfor lower radiation doses in special sit-uations, such as previous recent irradi-ation of the same anatomical region.
The threshold values given in Table 3were chosen both as simple round num-bers for ease of use and also so that afterthree notifications, regardless of thedose metric used, patient follow-up isnecessary. In other words, if the fluoro-scopic system provides reference pointair kerma, but not peak skin dose, theoperator would be notified first at 3,000mGy, next at 4,000 mGy, then again at5,000 mGy. A reference point air kerma
of 5,000 mGy indicates that the patientshould have clinical follow-up for deter-ministic radiation-induced injury. Theoperator would continue to be notifiedafter each additional 1,000 mGy.
A patient who has received a signifi-cant radiation dose is given written ra-diation follow-up instructions on theirdischarge instruction sheet. Sample dis-charge instructions are given in Appen-dix C. The patient is instructed to notifythe operator and/or a qualified medicalphysicist of the results of self-examina-tion of the irradiated area (either posi-tive or negative). Clinical follow-up isarranged if the examination is positivefor findings of deterministic radiationeffects. A qualified medical physicistevaluates all positive patient reports re-garding the dosimetric aspects of theprocedure and discusses these findingswith the operator. The physicist mayalso assist in facilitating clinical fol-low-up as determined by the operator.There may be other recommendationsand/or requirements pertaining to pa-tient follow-up according to a particularinstitution’s policies.
Recommendations for QualityAssessment
A periodic statistical report of doserecording performance and dose utiliza-tion is performed. A dose recordingcompliance rate of less than 95% for anyoperator prompts additional radiationsafety training, as discussed above.There is a review of the medical neces-sity for radiation utilization for thoseprocedures that are above 95th percen-tile of the dose-distribution histogramfor the institution, for procedures com-monly performed at that institution. Forexample, this review might demonstratethat the specific procedure could havebeen performed with fewer or shorterfluorographic runs or that better colli-mation could have been used. Alterna-tively, comparison may be made to lo-cal, regional or national compilations ofdose data, when available (34,48). Addi-tionally, there is periodic reporting tothe institution’s radiation safety officerregarding those cases in which the radi-ation follow-up was positive for deter-ministic radiation effects. This includesreview of the appropriateness of the ra-diation dose for those cases.
Appropriate review of image qualityin relation to radiation dose should beperformed at least annually as part of a
comprehensive quality control pro-
Stecker et al • S271Volume 20 Number 7S
gram, as performed by a qualified med-ical physicist.
Acknowledgments: Dr Michael S.Stecker authored the first draft of thisdocument and served as topic leader dur-ing the subsequent revisions of the draftby Drs Balter, Towbin, Miller, Vañó, andBartal. Dr Donald L. Miller is also chair ofthe SIR Safety and Health Committee. Dr.Thierry de Baère is chair of the CIRSEStandards of Practice Committee. Dr.John F. Cardella is councilor of the SIRStandards Division. All other authors arelisted alphabetically. Other members ofthe Standards of Practice Committee andSIR who participated in the developmentof this clinical practice guideline are(listed alphabetically): James R. Duncan,MD, PhD, Sanjoy Kundu, MD, DonaldLarsen, MD, Jorge A. Leon, MD, NealNaito, MD, MPH, Albert A. Nemcek, Jr,MD, Anne Oteham, RN, BSN, WilliamPavlicek, PhD, Rajeev Suri, MD, Louis K.Wagner, PhD, Eric M. Wasler, MD. Fi-nally, we would like to thank Debbie Kat-sarelis for all of her effort coordinatingthe synthesis of this document.
APPENDIX: A
Consensus Methodology
Thresholds are derived from crit-ical evaluation of the literature andevaluation of empirical data fromSafety and Health Committee mem-bers’ practices. Agreement wasreached on all statements in this doc-ument without the need for utilizingmodified Delphi consensus tech-niques (1,491,49).
APPENDIX: B
Example of Documentation of In-formed Consent for Radiation Risk
You have been scheduled for aninterventional procedure. This in-volves the use of x-rays for imagingduring the procedure and document-ing the results. Because of the natureof the planned procedure, it is possi-ble that we will have to use signifi-cant amounts of radiation.
Potential radiation risks to you in-clude:
• A slightly elevated risk for can-cer several years later in life.This risk is typically less than ½percent. This risk is low in com-
parison to the normal incidenceof human cancer, which is 33%for women and 50% for men ac-cording to the American CancerSociety.
• Skin rashes occur infrequently;on very rare occasions they mayresult in tissue breakdown andpossibly severe ulcers. Hair lossmay occur which can be tempo-rary or permanent. The likeli-hood of either of these occurringdepends on the difficulty of theprocedure and whether you aresensitive to radiation due to pre-vious procedures, disease, orgenetic conditions.
You or your family (proxy) will beadvised if we actually used substan-tial amounts of radiation during thecase. If this happens, you will begiven written instructions statingthat you are expected to have a fam-ily member check you for any of theabove signs.
APPENDIX: C
Example of Postprocedure PatientDischarge Instructions for High-dose Procedures
X-Ray Usage - one of these two boxesis checked as part of the discharge in-struction process:
□ Your procedure was completedwithout the use of substantial amountsof x-rays. No special follow-up isneeded because radiation side effectsare highly unlikely.
□ Your procedure required the use ofsubstantial amounts of x-rays. Radiationside-effects are unlikely but possible.Please have a family member inspect your___________________________, for signsof redness or rash two weeks from today.Please call (###) ### - #### and tell uswhether or not anything is seen.
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SIR DISCLAIMER
The guidelines of the Society of Interventional Radiology attempt to define practice principles that generally shouldassist in producing high quality medical care. These guidelines are voluntary and are not rules. A physician maydeviate from these guidelines, as necessitated by the individual patient and available resources. These guidelinesshould not be deemed inclusive of all proper methods of care or exclusive of other methods of care that are reasonablydirected towards the same result. Other sources of information may be used in conjunction with these principles toproduce a process leading to high quality medical care. The ultimate judgment regarding the conduct of any specificprocedure or course of management must be made by the physician, who should consider all circumstances relevantto the individual clinical situation. Adherence to SIR guidelines will not assure a successful outcome in every situation.It is prudent to document the rationale for any deviation from the suggested guidelines in the department policies andprocedure manual or in the patient’s medical record.
