IAEA code of practice for dosimetry in diagnostic radiology: recommendations for...

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SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALENRADIATION AND NUCLEAR SAFETY AUTHORITY

IAEA code of practice for dosimetry in diagnostic radiology:

recommendations for hospitals and specific issues

Antti KosunenRadiation Metrology Laboratory-STUK

Radiation safety and dosimetry in medical applications

11‐12 May 2012

TTÜ, Ehitajate tee 5, Tallinn, Estonia

SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALENRADIATION AND NUCLEAR SAFETY AUTHORITY 210.5.2012 / AK-STUK

• Review /introduction to contents of IAEA TRS 457 for clinical dosimetry

• Experiences of use the IAEA TRS 457(KAP meters, others)

• Remarks based on work at the SSDL of STUK

• Methods by TLD are not reviewed

Presentation

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http://www-pub.iaea.org/MTCD/publications/


Dosimetry formalismDosimetry intrumentationQuantities and uncertainties

• General radiography• Fluoroscopy• Mammography• Computed tomography• Dental radiography

IAEA TRS 457, Clinical dosimetry

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• Dosimetry• phantom• patient

• Guidance for selection of patients for DRL

•Appendix VI. Application of patient dose measurements• Background• Guidance for DRLs• Guidance for organ dose conversion factors for examinations• Summary of using effective dose



• Assumed that the x- ray equipment is properly maintainedaccording to QA program

• Assumed that the x ray tube output is linear relative to tube loading,if not complementary measurements are required

• HVLFor interpolations of calibration coefficientsFor conversions to organ doses (mammography)

Not necessrerily for every dose measurement, as information from Quality Control results exist


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• Examples and worksheets for measurements

• Dosimeters should be calibrated at the laboratory• Calibration interval:

• Based on national requirements,• Usually should not exceed two years



( 2sd )

• Risk assessment : Absolute risk • Dose surveys

~20 %

• Relative risk• Interventional procedures • Quality assurance

measurements• Paediatric procedures

7 %

IAEA TRS 457, Accuracy requirements for dosimetryAt reference conditions of dosimetry

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Air kerma based formalism

IAEA TRS 457, Dosimetry formalism

Beam quality correction factor


IAEA TRS 457, Selection of instruments, clinical

Requirements of International Standards are followed:

Requirements for dosemeters at laboratory can be used also as a background information for clinical dosemeters

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IAEA TRS 457, Measurement uncertainty (accuracy)


IAEA TRS 457, General radiology, dosimetry quantities

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IAEA TRS 457, General radiology

Incident air kerma

Air kerma detector with isotropic response


IAEA TRS 457, General radiology, phantoms

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IAEA TRS 457, Review on phantoms


IAEA TRS 457, General radiology, uncertainty

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IAEA TRS 457, Fluoroscopy, dosimetry quantities


IAEA TRS 457, Fluoroscopy

•Anti- scatter grid in position if used•Focus to table top distance as used clinically•Phantom 20 cm, 30 cm for large patients•Collimation large, to phantom size•Exposure under ABC

Detector with back scatter measurement capability

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IAEA TRS 457, Fluoroscopy


IAEA TRS 457, Fluoroscopy, uncertainties

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IAEA TRS 457, Fluoroscopy, kerma -area product (PKA)

Toroi et.al. A tandem calibration method for kerma-area product meters, PMB 53, 2008

Tandem method withreference KAP meterBeam area method

Calibration of KAP meters in situ


5 mmAl total filtration

Toroi et.al. Effects of radiation quality on the calibration of kerma-area product meters in x-ray beams, PMB 53, 2008

IAEA TRS 457, Kerma -area product

Incident beam

Transmitted beam

KAP meter

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IAEA TRS 457, Fluoroscopy, Kerma area- product

Beam area or tandem method

Over and under couch set-ups


IAEA TRS 457, KAP -meters

Toroi et.al. Effects of radiation quality on the calibration of kerma-area product meters in x-ray beams, PMB 53, 2008

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IAEA TRS 457, Kerma -area product (KAP)


Toroi & Kosunen. The energy dependence of the response of a patient dose calibrator, PMB 54, 2009

IAEA TRS 457, KAP-meters

Large fields for reference KAP meter30 cm * 30 cm

50-150 kV

Patient Dose Calibrator PDC-1Radcal

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KAP-meters, Set-up

80 kV, 4.8 mmAl, 10*10cm at 30 FDD

Toroi et.al. Calibration of kerma area product meters with a patient dose calibrator, IDOS proceedings, Vol2, IAEA, 2011http://www-pub.iaea.org/books/IAEABooks/8700/Standards-Applications-and-Quality-Assurance-in-Medical-Radiation-Dosimetry-IDOS-Proceedings-of-an-International-Symposium-Vienna-9-12-November-2010


IAEA TRS 457, KAP uncertainties

IEC 60580, 25 % (k=2)

In examinations with varying voltage, 25 %

For specific tube voltage and energy dependence considered: 6 % (k=2)

KAP indicators based on calculations need to be calibrated also

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IAEA TRS 457, Mammography, dosimetry quantities


IAEA TRS 457, Mammography

Plane parallel IC withentrance window

(low energy dependence)

45 mm PMMA phantom

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IAEA TRS 457, Mammography, HVL

HVL measurement


IAEA TRS 457, Mammography, glandular dose

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IAEA TRS 457, Mammography, uncertainties


IAEA TRS 457, Computed tomography, dosimetry quantities

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IAEA TRS 457, Computed tomography

CT air kerma indices

T, Nominal slice thicknessN, number of slices/detector rows per scan for MSCT/MDCT

In air or in a phantom


IAEA TRS 457, Computed tomography, phantoms

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IAEA TRS 457, Dosimetry formalism



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Air kerma lenght product


IAEA TRS 457, Computed tomography, kerma lenght product

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AAPM, IAEA, Recent approach for wide CT beam dosimetry

Work by ICRU…?

2010 2011


IAEA HHS No5, Computed tomography

From :IAEA Human Health Report No:5, Status of computed tomography dosimetry for wide cone beam scanners, 2011

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Computed tomography, kerma lenght product, STUK approach

Measurement of kerma lenght product for whole examination


IAEA TRS 457, Dental radiography, dosimetry quantities

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IAEA TRS 457, Dental radiographyTRS include quidance for bitewiew and panoramic examinations

Uncertainties

Kerma lenght product 13 % - 6 %Kerma area product 13,2 % – 6,4 %


The development of advanced dosimetry techniques for diagnostic and interventional

radiologyCoordinated Research Project on Implementation of the

International Code of Practice on Dosimetry in Diagnostic Radiology TRS 457

IAEA TRS 457, Implementation and testingAdvanced techniques, 2010 -2013

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Paediatrics - clinicalDevelopment of guidanceGeneral RadiographyfluoroscopyCTanalysis & uncertaintyInterpretation of clinical dataDevelopment of guidancedevelopment of questionnaireorgan dose + eff. Dose & riskSSDLPreparation for intercomparisonintercomparison -SSDL - KLPintercomparison -SSDL - KAPnew qualities [KAP & mammo]Farmer chambers with RQT


I/II


Advanced dosimetryDevelopment of guidanceMDCTcone beam CT vs CTmammographic tomosynthesisdental dosimetrySkin doseDevelopment of guidanceFilm characterisation SSDLhigh dose calibrationhigh dose patientslow dose calibrationlow dose patientsuncertainty


DICOMDevelopment of guidancesurvey of DICOM capabilityUncertainty formulationAssessment of clinical scenariosassessment of uncertainty budget from scenariosDevelopment of guidance

I/II

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•IAEA TRS 457 contains a comprehensive description of dosimetry methods used for diagnostic radiology

•Two options for reference KAP are presented; beam area or use of a reference KAP meter

•Generally 13 – 15 % (k=2) level of uncertainty (KAP meters 25 %) can be achieved for measurements in clinical dosimetry. Accuracy below 10% requires use of reference class dosemetersand/or calibration of dosemeter for user specific radiation qualities.

Summary I/II


For dosimetry of wide beam CT the IAEA TRS457 methods need to be complemented by more recent dosimetry guidance (AAPM, IAEA, others)

IAEA TRS 457 has limitations for wide beam CT dosimetry. More recent recommendations exist; AAPM (2010), IAEA (2011)

Advanced dosimetry techniques for diagnostic and interventional radiology are under investigation in the coordinated research project by IAEA.

Summary II/II

IAEA code of practice for dosimetry in diagnostic radiology: recommendations for...

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