A Method for Determining Organ Dose from 

External Exposure Monitoring Data

Timothy D. Taulbee, James W. Neton, and Larry J. Elliott

U.S. Department of Health and Human Services (DHHS), Centers for Disease Control and Preventio

National Institute for Occupational Safety and Health (NIOSH), 4676 Columbia Parkway MS: R-45, Cincin

• Organ dose is needed for a 

compensation decision under the United States Energy Employees Occupational Illness Compensation Program Act (EEOICPA) of 2000.

• To determine organ dose from 

monitoring data, Dose Conversion Factors (DCFs) are needed.

• Dose Conversion Factors are 

dependent on:

•Organ of Interest (Cancer 

Location)

•Radiation Monitoring Method•Photon Energy•Exposure Geometry

METHOD

INTRODUCTION 

CO

Monitoring Device Conversion• Problem:

1.ICRP Publication 74 Organ 

Dose Conversion Coefficients use a non measurable quantity of free-air KERMA.

2.Measured Radiation Exposure 

or Dose quantities include:

• Exposure (Roentgen (R))• Ambient Dose Equivalent 

(H*(10))

• Personal Dose Equivalent 

(Hp(10))

• Solution: Organ dose is 

determined by first converting measured dose to free-air KERMA and then applying DCFsin ICRP 74.

a

T

a

p M ,Hp( ) D K

D

K

H ( ) DCF( D ) T → = × 10

1

10

Energy Interval Estimation• Problem:

1.Photon exposures typically cover 

a wide range of energies.

2.Organ dose conversion 

coefficients are tabulated for discrete energies.

3.Probability of Causation 

calculations used in the NIOSH Interactive RadioEpidemioligicalProgram (NIOSH-IREP) use three photon energy intervals based on Radiation Effectiveness Factors (REFs).

– Photons < 30 keV– Photons 30-250 keV– Photons > 250 keV

• Solution: Calculate average dose 

conversion factor by integrating over energy interval and dividing by the energy range.

H (10)Gy

Lung Dose - Gy 0.695

( )

( , )

p

0.250

0.030 ,0.030 0.250 = =

∫ −

Range

f E dE

DCF

DM Eγ MeV

Exposure Geometry• Problem:

1.Organ dose is dependent on 

exposure geometry.

2.Typical work environment can 

result in multiple exposure geometries. Organ dose conversion coefficients are tabulated for discrete energies.

3.Of the six exposure geometries 

presented in ICRP Publication 74, only four are of primary interest in occupational dose.

• Solution: An average dose 

conversion factor can be developed using a time weighted average approach.

( ) ( ) ( )

() () ROT M ROT ISO M ISO

M W AP M AP PA M PA

w DCF

D E w DCF

D E

DCF

D E w DCF

D E w DCF

D E

γ γ

γ γ γ

, ,

, , ,

+

= + +

ISO 50%

ROT 50%

Security Guard

ROT 10%

AP 90%

Glovebox Chemist

Chemical

Separations

ISO 25%

ROT 75%

Reactor Operator

ROT 50%

AP 50%

Fuel Handler

Reactor

ISO 25%

AP 75%

Machinist

AP 25%

ISO 75%

General Laborer

Uranium Facility

Facility Job Geometry TWA

Photon Energy (MeV)

0.01 0.1 1 10

Lung Dose Conversion Factor

DT/Exposure - AP Geometry

0.00.20.40.60.81.01.21.4

Photon Energy (MeV)

0.01 0.1 1 10

Lung Dose Conversion Factor

DT/Hp(10) - AP Geometry

0.00.20.40.60.81.01.21.4

• Example of Work Specific Dose 

Conversion Factor (same cancer and energy interval)

• Lung Cancer Dose Conversion 

Factor

Organ Dose/Exposure (DT/D

M) 30-250 keV photons (Eγ

)

1.Glovebox Chemist

DCF(D

M,Eγ

)W = 0.965 Gy/100R

2.Security Guard

DCF(D

M,Eγ

)W = 0.702 Gy/100R

• Large va

Conversdue to m

• Computa

should binformat

• General

methodospectrum precisely geometr

• Same m

applied t

• Publishe

used to cbadge anorgan do

• Using thi

magnitudbetween and orgaand accodose rec

B

Dose Conversion Factor (DT/DM)

30-250 keV Photons - AP Geometry)

0.000.200.400.600.801.001.201.401.60