rajiv dhamija, md · 2018-04-01 · rajiv dhamija, md chief division of nephrology-rancho los ......
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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
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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
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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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