Rajiv Dhamija, MDChief Division of Nephrology-Rancho Los

Amigos National Rehabilitation Center-Department of Health Services Los Angeles

County-

Associate Clinical Professor of Internal MedicineWestern University of Health Sciences

Basic Knowledge

Literature Review

Reporting Standards

Time –decreasing the time for which the imagingmodality is used deceases radiation exposure foroperator, staff, and patient.

Distance –Doubling the distance from the source ofradiation decreases the exposure to 1/4th of the originalradiation dose (3). The operator should be positionedon the opposite side of the source of radiation ifpossible.

Shielding –occurs on multiple levels, includingarchitectural, portable, equipment mounted, andpersonal protective equipment.

X-ray Physics and image formation

Interaction of X-rays with matter

X-rays are both electromagnetic waves and particlesthat move along straight lines in vacuum

Interaction with matter

No interaction

Simple change in direction

Change in direction and energy (Compton Scatter)

Complete absorption (photoelectric effect)

X Ray Absorption Elastic scatter (Rayleigh) : x

ray deviated without energychange

Inelastic scatter (Compton):x ray leaves part of energyand emerges in diffdirection

Complete absorption(photoelectric eff) x rayenergy completelytransferred to matter

Equipment

X-ray tube

Image detector with anti scatter device on other side

Table between them supporting the patient

X-ray tube emits photons with differentenergies

Highest energies (keV) corresponds to highestvoltage applied to the X-ray tube (kVp)

The greatest source ofradiation to theoperator and staffoccurs from scatterradiation. (3)

radiation is greateston the radiographictube (emitter) sideand lower on theimage colleting side.(3)

Primary x –ray beam 5 to 20 mGy/h

Scatter radiation 1 to 10 mGy/h

Leakage x-ray By law, no more than

1 mGy/h allowed

Direct Cellular damage (1/3 of damage)

Direct DNA breakages

Indirect cellular damage (2/3 of damage)

Water hydrolysis and free radical formation withincells

Deterministic effects

Typically occur once a threshold level of exposure isoverstepped

Clinical severity is correlated with intensity ofexposure

i.e. Skin, hair, physician lens

Stochastic effects

Likelihood of occurrence increases with exposure

Concern repeatedly exposed physicians, staff, andpatients

Prompt-24 hours to 2 weeks > 2 Gy exposure

Early- > 6 Gy exposure

Mid-term- > 10 Gy

Long-term- > 15 Gy

Table 1Classification of radiation induced skin injuries (American National Cancer Institute)8.

Grade 1 2 3 4 5

Symptoms Faint erythema or dry

desquamation

Moderate to brisk

erythema; patchy moist

desquamation, mostly

confined to skin folds

and creases; moderate

edema

Moist desquamation in

areas other than skin

folds and creases;

bleeding induced by

minor trauma or

abrasion

Life threatening

consequences; skin

necrosis or ulceration of

full thickness dermis;

spontaneous bleeding

from involved site; skin

graft indicated

Death

Classification Prompt Early Midterm Long-term

Timing ofSymptoms 24 hr. - 2 wk. 2-8 wks. 6-52 wks. >4 wks.

Exposure >2 Gy >6 Gy >15 Gy >15 Gy

EffectTransientErythema

InflammatoryErythema

Erythema progresses todermal necrosis

Dermal atrophy with tissueloss

Spontaneouslyresolves Itching, pain

Subcutaneous fat/bloodvessel damage

Permanent induration ortelangiectasia

Patient related: Active smoking, nutritional depletion, diabetes

mellitus, hyperthyroidism, obesity or overlappingskin folds, skin location and surfaces

Procedure related: Prolonged exposure to same skin entrance point,

overlapped areas of irradiated skin, short intervalrepeated exposures

Physician related: Lens- cataracts

Repeated exposures to unprotected areas

Probabilistic event

Increases proportionally to the intensity of theexposure

Induce development of solid cancers, leukemia,malformations on offspring several years afterthe exposure

Depends on radio sensitivity of exposed organor tissue

Brain cancers mainly on left side

Leukemia associations amongstinterventionalists

Estimates: 100 peripheral angiographic proceduresper year annual dose estimates

40 mSv eye

30 mSv head

6 mSv under protective lead apron

In the APview, abimodaldistributionwas noted,greatest at theposition ofthe operatorand assistant(10)

In the leftlateral view,a singlepeak wasgreatest atthe side ofthe table,next to theemitter. (10)

In the RAOview, asingle peakwas greatestat the side ofthe table,next to theemitter. (10)

Annual environmental exposure 1-3 mSv

Exposed workers 100mSv over 5 years (20 mSvper year)

Physicians practicing 15 years receiving 2-5MSv per year has LAR cancer estimated 1 in200

Pregnancy-

Main feared stochastic effect

1-5 mSv exposure considered threshold

Monitoring Patient Exposure-Indirect Fluoroscopy Time (min) Calculated differently depending on system and

manufacturer

Correlates poorly with biological risk

(DAP) kerma area product (Gy.cm2) Stochastic- to compare same anatomic region at

different institutions

(CAK) Cumulative air kerma (mGy or Gy) Deterministic dose at Skin

Monitoring Patient Exposure-direct Entrance skin dose (Gy)

Nearly half of all radiationexposure in the US is due toionizing radiation received duringmedical procedures.

The majority of which comes fromCT scans in acute care settings. (1)

Do No Harm Risks vs. benefits Lifetime monitoring and reporting

throughout health/hospitalsystems

Estimated averageionizing radiation bysource at the USpopulation level in 2006(2)

Justification, optimization and dose limitation Dose limits and reference level establishment

ALARA (as low as reasonably achievable)

Quality Control Imaging system calibration

Patient Information Risks vs. benefits

Recording and Reporting of doses from procedures

Utilization of Diagnostic reference levels

Availability of dose indicating devices One under lead apron (chest level)

One outside lead apron (level of collar or left shoulder)

Lack of training in radiation protection

Accreditation, certification and recognition: medical education and training in medical radiation

protection

Train the trainer

National and state authorities recognizing formaleducation

Exams and recertification's periodically

Physicians involvement in policy

Should be accepted like blood borne hazards(masks and gowns)

Technique Additional Info

Use shielding whenever possible Radio protective pads or drapesshould not be visible in thefluoroscopic image

Minimize the use of fluoroscopy Beam should only be on whenphysician is looking at the screen.Low frame-rateCollimate

Magnification Increasing the magnificationdecreases scatter radiation tooperator, but increases patient skinentry dose for patient (9)

Plan ahead Review all existing imageinformation prior

Patient size Large patients increase the amountof scatter radiation.

SCATTER RADIATIONDISTRIBUTION WITHOUTTABLE SKIRT

SCATTER RADIATIONDISTRIBUTION WITH TABLESKIRT

Shield Type Radiation Reduction toOperator

Table Skirt 64% reduction toextremities (4)

Ceiling suspendedShields

50% reduction in head,neck, and lens (5)

Mobile shield 95% reduction in APand 70% reduction inlateral scatter (6)

Lead patient drape 1/9th to 1/5th reductionin scatter radiation (7)

Apron, thyroid shield,gloves

0.25mm lead thickness10%0.5mm thickness allows2% through (3)

Architectural shielding isbuilt into walls andceiling.

Ceiling mounted apronscan help alleviateergonomic issues causedby heavy aprons.

Lead composite aprons(combined with materialslike cadmium, tin, iodine,barium, antimony, ortungsten) can help reduceweight but have mixedefficiencies (4)

Increasing horizontalcollimation decreases the field ofview in the horizontal plane.

Increased horizontal collimationdecreases scatter radiation foroperator, assistant, andanesthesiologist, with greatestreduction to operator (9)

0 cmCollimation

10 cmCollimation

Operator 2.3mSc/h .32mSv/h

Assistant .93mSv/h .13mSv/h

Anesthesiologist

.77mSv/h .04mSv/h

Increasing vertical collimationdecreases field of view invertical plane

Increased vertical collimationdecreases scatter radiation foroperator, assistant, andanesthesiologist, with greatestreduction to operator

0 cmCollimation

10 cmCollimation

Operator 2.3mSv/h .28mSv/h

Assistant .93mSv/h .10mSv/h

Anesthesiologist

.77mSv/h .06mSv/h

Increasing themagnification from 0to 3 caused a decreasein radiation exposurefor the operator from2.30mSv/h to.83mSv/h. Similartrends were noted forthe assistant and theanesthesiologist (9)

• Mean Peak Skin Dose for eachprocedure was less than 50 mGy.

• Tunneled dialysis catheter hashighest dose area product (DAP)and mean peak skin dose (PSD)

• Significant differences found influoroscopy time found intunneled vs non-tunneled access

Heilmaier et al. looked at theradiation exposure betweengroup 1, with patient dosemonitoring systems, andgroup 2, with patient dosemonitoring plus real timeoccupational dose monitoring.

Group 1 had an meanradiation dose of 47 Gy . Cm2,Group 2 had a mean radiationdose of 37 Gy . Cm2.

noted a decline in Kerma areproduct in group 2 for 15 ofthe 19 procedures and alsonoted a strong correlationbetween patient andoccupational dose.

Christopoulos et al. had 505patients cardiaccatheterization randomlyassigned the use or no use ofBeeper Sv radiation monitor,which produces a warningsound in response to excessradiation exposure.

The Beeper SV group hadradiation exposure mean of 9microSv compared to 14microSv for the controlgroup.

Concluded that real timedosimetry with audiofeedback can significantlyreduce operator radiationexposure.

Cho S, et al. used intracardiacECG monitoring to placedialysis catheters on 142hemodialysis patients withoutthe use of fluoroscopy.

They monitored the ECG for thehighest P wave morphology, atwhich point they stoppedadvancing the catheter.

The catheter flow was adequatein 139 cases and was only foundto be malposition in 6 of the 142cases.

No significant complicationswere noted.

Concluded that intracardiacECG monitoring was safe andeffect method of tunnel catheterplacement for all adults withevident P waves on ECG.

Radiation Protection- consider lifetime radiationburden and age of patient

Dose Reduction during Procedures Pulse mode Frame rate to be lowest possible Time on pedal Low dose-setting (half or low dose modes) Digital subtraction angiography-requires substantial

radiation exposure Collimation reduce field of view Magnification- use digital zooming and corrected image

intensifiers Limit Angulations- leads to increased scatter

Imaging chain geometry- detector should be placed ads close to patient aspossible to avoid beam energy dispersion and low signal acquisition

Auto-exposure settings- allows constant image quality at the lowest dose Flat panel detector technology- can lead to reduction in radiation exposure

up to 30% Operator controlled imaging -Pre-operative image analysis- 3D workstations Advanced imaging applications: Image fusion available in hybrid rooms-

allows up to 70% reductions reported Shielding- levels decrease inverse squared distance from main source,

longer sheaths, table mounted lead skirts to avoid downwards deflectedX-rays, 0.5mm lead equivalent garments reduce scatter radiation by 90%,sterile gloves (15-30%) but should not be used in field of view, surgicalprotective drapes suggested with bismuth and barium but must be out offield of vision

Follow up after accidental exposures- fluoroscopy time >60 minutesshould raise serious concern, record information carefully in patientsmedical record

Dose awareness- live radiation dose exposures on systems monitor, doseinformation tracking systems with statistical analysis.

Basic knowledge about X-rays and radiationprotection is mandatory

Training and education of Interventionists isoften incomplete and fragmented

Specific training at beginning of careers andrefresher courses play a key role

Specific attention Application of radiation dose reduction strategies

Monitoring of patients and personnel

Universal acceptance like that of blood bornehazards

1: Lee, Christopher, Elmore, Joann, Radiation-related risks of imaging studies 2015,https://www.uptodate.com/contents/radiation-related-risks-of-imaging-studies?source=search_result&search=radiation%20safety&selectedTitle=2~150

2:https://www.uptodate.com/contents/image?imageKey=PC%2F61739&topicKey=PC%2F14613&rank=2~150&source=see_link&search=radiation%20safety

3: Fazel, Reza, Einstein, Andrew J, Radiation risk to healthcare workers from diagnostic andinterventional imaging procedures 2016, https://www.uptodate.com/contents/radiation-risk-to-healthcare-workers-from-diagnostic-and-interventional-imaging-procedures?source=search_result&search=radiation%20safety&selectedTitle=5~150

4: Meisinger, Quinn, Stahl, Cosette, Andre, Michael P, et. Al, Radiation Protection for the fluoroscopyOperator and Staff. American Journal of Roentgenology, October 2016, 207:4,http://www.ajronline.org/doi/full/10.2214/AJR.16.16556

5: Vano, E, Gonzalez, L, Beneytez, F et. Al. Lens injuries induced by occupational exposure in non-optimized interventional radiology laboratories. January 28, 2014, Epub.http://www.birpublications.org/doi/10.1259/bjr.71.847.9771383

6: Luchs JS, Rosioreanu A, Gregorius D et. Al. Radiation safety during spine interventions. 2005 Journalof Vascular and Interventional Radiology 16:107-111 http://www.jvir.org/article/S1051-0443(07)60606-X/abstract

7: King JN, Champlin AM, Kelsey Ca, et. Al. Using a sterile disposable surgical drape for reduction ofradiation exposure to interventionalists American Journal of Roengenology, 2002, 171:1http://www.ajronline.org/doi/10.2214/ajr.178.1.1780153

8: Mettler F, Huda W, Yoshizumi T, et Al. Effective Doses in Radiology and Diagnostic NuclearMedicine: A catalog, July 2008, 248:1

9: Haqqani O, Agarwal P, Halin N, et. Al. Minimizing radiation exposure to the vascular surgeon Journalof Vascular Surgery 2011 55:3 799-805

10: Haqqani O, Agarwal P, Halin N. et Al. Defining the radiation “scatter cloud” in the interventionalsuite Journal of Vascular Surgery 2013 58:5 1339-1345

Radiation Doses for Venous Access Procedures; Erik S.Storm, Donald L. Miller, Laurie Jean Hoover, Jeffrey D. Georgia,and Tara Bivens, Radiology 2006 238:3, 1044 1050

Radiation dose associated with dialysis vascular access interventional procedures in the interventionalnephrology facility. BeathardGA, Urbanes A, Litchfield T; Semin Dial. 2013 Jul-Aug;26(4):503-10. doi: 10.1111/sdi.12071. Epub 2013 Mar 15.

Editor's Choice –Minimizing Radiation Exposure DuringEndovascular Procedures: Basic Knowledge, Literature Review,and Reporting Standards. Hertault, A. et al. European Journal ofVascular and Endovascular Surgery , Volume 50 , Issue 1 , 21 –36

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