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Estimates of Radiation Dose to the Embryo from
Nuclear Medicine Procedures
EdwardM.Smith*and G. G. Warner
Oak Ridge National Laboratory, Oak Ridge, Tennessee
These phantom studies and computer calculations provide a direct meansof estimating the radiation dose to the embryo resulting from the administration of a radiopharmaceutical to the mother during organogenesis.
The specific absorbed fractions to the embryo from 19 source organs werecomputed for 12 monoenergetic photon energies. Tables of absorbed doseper unit cumulated activity, S, for the embryo as a target organ have beenassembled for sOmTc, 1111n, llSm7@@123,, 131k, and 133Xe. In addition, the doseto the embryo was calculated for several of the radiopharmaceutical-s forwhich the MIRD Committee has published dose estimate reports.
J Nuci Med 17: 836-839, 1976
The estimate of the radiation absorbed dose to theembryo is essential when a radiopharmaceutical hasbeen intentionally or unknowingly administered to
a woman at the beginning of her pregnancy (1).Currently there are no direct methods of calculatingthe dose to the embryo unless it is assumed to beequivalent to the dose to the uterus. The latter maybe calculated by using the MIRD Committee's formalism and the data contained in MIRD Pamphlet
No. 1 1 (2) and the revision of MIRD PamphletNo. 5 (3).
MATERIALS AND METHODS
Anatomic model. A sphere of radius 0. 13 cm andmass 9.2 mg is the geometric model chosen to represent the embryo (4) during the period of organo
genesis, i.e., 10—41days after conception. Althoughthe weight and physical dimensions of the embryovary significantly during this period, these changeswill have little effect on the dose estimates since specific absorbed fractions are relatively insensitive tomass and shape, especially when the target organ isdistant from the source organ (2,3) . The sphere rep
resenting the embryo is located at the origin of the
semiaxes of a 66-cm3 ellipsoid, representing theuterus in the heterogeneous adult phantom (3). Thesemiaxes of the ellipsoid representing the uterus are
2.5, 5.0, and 1.5 cm; a plane truncates the y axis ofthe ellipsoid anteriorly. Figures 1A and lB are computer plots of sections through the adult hermaphrodite phantom illustrating the shape of the uterus andits position relative to other organs.
Specificabsorbedfractions.The specificabsorbedfractions cI@were calculated for 12 monoenergetic
photon energies and various source organs (Table1), asdescribedin the revisionof MIRD PamphletNo. 5 (3) with the exceptions noted below. To reduce the computing time, the embryo was taken asthe source organ and the source organs listed inTable 1 were taken as the target organs with theexception of bone, lungs, and red marrow. To reducecomputer time further, the Build-Up Factor Codewas used rather than the Monte Carlo Code. Whenused appropriately, the agreement between the twocodes is good (5). A linear extrapolation was madeto obtain clsfor 10 keV. After t was calculated withthe embryo as the source organ, the reciprocity the
orem was used to calculate t for the embryo as the
target organ.
Received Feb. 10, 1976; revision accepted April 15, 1976.For reprints contact: E. M. Smith, 404 Church Ave.,
Suite 15, Maryville, TN 378701.C Consultant.
836 JOURNAL OF NUCLEAR MEDICINE
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INSTRUMENTATION AND PHYSICS
@— Since the reciprocity theorem is not valid when
the target and source organs have different elemental-0 U@ Ø ‘0W@@ W@-0 ‘0P—.‘0‘0‘1@‘0P—.‘0‘0P—.‘0 compositions, direct Monte Carlo Code calculations
0@ @??@? ??@1@' c?cI@@
0 L@JUi LU IU LU LU ILl IU IU W lu ISi lu IU UJ LU IU Mi IU were made for bone, lungs, and red marrow as sourceNV@@flN'f)@ o.elc,4c.),o,@ mv@@qc.)o@ OC@•@C'4 ‘-O'O@ Ir).V@','@.
,.:@ @-N .- C'4 l(@‘@V@(.@@@ organs. To improve the statistics of these calculations,
the embryo was assumed to be a sphere with a mass_ov@,o,ow) InV)'O'OF-,. ‘O'O'fl@ ‘O'O@
0@ c1sc??@ 1?@cIs@s@1@ oflOgm.Thischangeshouldnotaffecttheaccuracy0@ @JIUIUluMi w UiI5JIUW IUUiW Uilu USMiIIIIIJ
‘-P-%'nc@)@ c'imm@ [email protected]@'on'o @nc'i'o@c@4 I ‘@°@F%C@)C@)‘0 O@‘nq C'4‘e@@-c'@U!@@ I of the calculations since@ is relatively insensitive
.-@,,.:c4c4 ,.:.:C.;C.41,; ‘n'â',c-i.- ,-.-.-w@to the mass of the target organ as long as the two
@ organsarenotadjacent.
0@@@@ Absorbed dose per unit cumulated activity. TheI ‘[email protected]@me@o@ -@-@‘-@1flOC'lC@4_‘@c-@e4C'4..: ,.;CMIflW)‘0@ N ,.:,.:vc valuesofabsorbeddoseperunitcumulatedactivity,
S, were calculated as described in MIRD Pamphlet-O.'@'o'O'fl.nw@'o'op-% .()@@
@ 0 ??@@?@ ¶??@ ci@?@ No. 11 (2) using the values of 4@ given in Table 1.@ q Uiw w UJIU @gji@jlu lu lu w iu lu lu tu lu iu lu
E .@@@ o@v)mm.- .-8@ The results are given in Table [email protected]'e @m@p-@o mo@N@ 0@ ,-Ir@e@c@@M @,-c.@e4Ir@ [email protected]
U' Absorbed dose calculations. The values given in..z‘?@ Table 3 were obtained by using the general MIRD.0v),O,Ov@ IflIfl,O-OF@@‘O'O'fl@ ‘O'O@O
@ 0@ @. dosecalculations:0 0 @:@@@@@@@@ LUUi Ui LUIU IiiP-@mI-%0 O'O@0'@) C'4O'F-@N0 N.O.O'- o.@; 0@,[email protected] C@C@ ‘ousv)c@4vjNe4V@@ 15(embryo) = @i5(embryo@-r11)
@;o ,Ov)[email protected]@@ •o'o.n-o@@‘O@'O@ hvs@@ II@
@ @:@@@@ bI
LUIUWIUUJ UJ$UUJWW UJUJI&JWW
@o °@@
m@c@c1@% II, (rads),W4 0
0
z>@ @o@o,oo@@ S(embryo@—rl)=@IFI(embryo4-rh)
2@@@@@ I
o@@ . @.—om@@-o.@.—0r--,@ .)-OO.@=11.@@ .@ (rads/@Ci-hr),e.@ ‘-t-@c@ic@s―@C'@C-@C'@o@-t-Zc-ioc'i.-o@ .ILz@ -a.o@ g@@ i@(embryo)=@Ah(O,oo)S(embryo@—rl,)
0'OP%01@)@ h.@ 8 o clscM@@ cls@@ ““7 @T@' .@n0@ iuwwiuIUiuluUiUiIUUi(UIUUJLUIUWMiIU@ z@ q .r)O.-@-@'[email protected].'oc'smp-@@.@-op'-@0 (rads),01; 0@ 2@ C'@(')C'I.-V) o:.-.-,-M.; t@4,@o where 15(embryo) is the total mean dose to the emu@ 1.@4 C
— @@*,.%F@%v)@[email protected]@cDm @mW)E bryo (rads); 17(embryo*-r11) is the mean dose to.0
‘0@@ c@)0 0.@ C.) -0 I(@-0 O@(@)Q -0 .n 0 O@ a the embryo from source organ r1, (rads) ; A1(O, cc)@I- ci@ E
@ UI ‘@‘@ (‘4m ‘a@ @ac@ir-Zmc'i .5 @Sthe cumulated activity in source organ r1, from04 Sus £ t = 0 to t cc (MCi-hr) ; @Iis the mean energy
@O m@m00c@,v@ 5@ ). 0@@@@@@@@@@@@@@ :i:@@@@@ emitted per nuclear transformation for i-type radia@ C,'u@
.-V@[email protected] N(@)F-.@@ o..-o@0 ,@@@ 0 @1)@ m@‘n‘@@ 0 01-.‘@ei-o@@ @,‘@@ .0 tions(gm-rad/@Ci-hr);41(embryo4-r11)isthespe@ MI @-@:@.,@ ‘a,.: ,.;@ @,;,-@@ C4 N@ C,'@ cific absorbed fraction of energy for the target organ,@IM
v,.@,- ‘0C@ ‘0F@ @.o. -@ @o‘o -0 P@%@ 0 0. 0 ‘0@ the embryo, for i-type radiations emitted in source
@ V)@@@@@ organ r1, (gm'); and S(embryo@-r11) is the abw2@ oc')'e@o'oNw)[email protected]@omo@ta@ 0 Ci@@@ov@0 0c.)an.-.o NO@'ON@@% ‘@0@@'° sorbed dose to the embryo per unit cumulated ac@@@ “5@c'5@-@.,‘@vic.@'d
2 tivity in source organ r1, (rads/1@Ci-hr).,o,,@ c@,[email protected] ‘o'oO@@o‘no@o'o 5
0 m o c@0@ c'o@ @.cj cjscj@@ c@i@ o .@ The dose calculations were made for a 70-kg refLiJjJJ,JJJJ I1JJJjJI@JL@J WWUJUJUJ IiJIIJI@JJJ .@
0@@@@ 0 o 0 0 0 0 0 (N 0 0 0 0 0 0 0@ erence adult as described in Refs. 2 and 3. It was0 oo@@*@@q @-oc-@oo@@
r-Zm o N ,@.@p@@: @j N c@@ ‘@c@@ assumed that the uterus was not enlarged and that
the presence of the placenta could be neglected. TheSf embryo weighed 9.2 mg and was implanted cen@-:@ C
.@@ :.@ trally in the uterus. The embryo was assumed notCO@...@ .2@@@ i@@ @g.;@ tobeirradiatedbyanyparticulateradiationsexcept3
a C@2°@ 1; 1@ 8 a@@ 2@ .@‘@@ I@ when the activity is uniformly distributed in the total-01@0
@ -g@ .k@@@ t @.@@ ;@ @.@ @0.@@@ body. In this case the embryo contains its [email protected] @gg@& @@cbO
1@@@ i@ @5 @5 @5 @5@ > C 0 @E@ g :@ C .• @-a@ tionate share of activity and S(embryo+-total body)
:@.3 @OOe.t8@t*@Ireflects this. The bladder was assumed to contain200 ml of urine. All assumptions used in the appropriate MIRD Dose Estimate Reports (6—9) werealso assumed in the dose estimates given in Table 3.
Volume 17, Number 9 837
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SOURCE ORGANS r1,Radionuclides
Sourceorgans @mTc 1111n “@ln @l ‘@l ‘@Xe
SMITH AND WARNER
subl ingualg'and
flyer
bladder
stomach
FIG.1. Computerplotsof sectionsthrough adult hermaphrodite phantom IIlustrating shape of uterus and its positionrelative to other organs.
TABLE 2. S(embryo+-r11), ABSORBEDDOSE PER UNIT CUMULATED ACTIVITY (rads/@Ci-hr), FOR SEVERALRADIONUCLIDES AND VARIOUS WITH THE EMBRYO AS THE TARGET ORGAN*
l.4E—06
5.7E—052.3E—O63.OE-06
3.1E—05
l.8E—052.2E—053.6E—062.1E—O6
3.2E—07
AdrenalsBladder contentsBone (total)
GI tract (stom. cont.)GI tract (SI and cant.)
GI tract (ULI cant.)GI tract (LLI cont.)Kidneys
4.OE—07l.9E—057.6E—079JE—071.1E-.05
6.1E—067.6E—061.2E—066.5E-078.4E—08
8.6E—073.2E—051.3E-061.8E—06l.8E—05
9.9E—061.2E—052.1E—061.3E—062.4E—07
4.9E—072JE—059.OE—071.1E-06l.4E—05
7.4E—069.2E—061.4E—067JE—071.1E—07
l.3E—064.9E—052.OE—062.8E-062JE—05
l.5E—O51.9E—053.3E—O62.OE—063.6E—07
7.OE-089.8E—062.1E—072.1E—074.8E—06
2.1E—062.7E—O62.5E—07l.3E—071.2E—08
LiverLungs
2.3E—062.6E—062.OE-056.8E—074.5E—09
7.OE-075.4E—[email protected]—06
6.6E-.068.OE—065.8E—052.2E—062.4E-08
2.1E—061.8E—062.4E—088.2E—06
3JE—064.6E-063.3E—05l.3E—062.5E—08
1.2E-071.1E-062.5E—088.4E—06
2JE—O63.8E—062JE—058.OE—077.3E—09
8.3E—076.5E—077.3E—094.1E—06
5.8E-.066.9E—06
5.OE—052.1E—063.9E—08
l.9E—061JE—063.9E—08l.2E—05
M.arrow (red)Other tissues(muscle)Ovaries
PancreasSalivary glands
7.OE—07L3E—069.9E—06
4.2E—1O
l.9E.-07l.OE—074.2E—lO5.3E—06
SkinSpleenThyroidTotal body
. The digits following the symbol E indicate the power of 10 by which the
4.0 X 10@'.initial number is to be multiplied, e.g., 4.OE—07
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Rodspermillicuri.Radiopharmaceuticaladministered
0.007
INSTRUMENTATION AND PHYSICS
tions include the use of the S values (Table 2), whichspecify the anatomic model, a uniform distribution
of activity in the source organ, a bladder containing200mlofurine,andthenucleardata.
ACKNOWLEDGMENTS
This research is sponsored by the Energy Research andDevelopment Administration under contract with UnionCarbide Corporation. This paper was originally presented atthe 16th Annual Meeting of the Southeastern Chapter ofthe Society of Nuclear Medicine in Atlanta, Ga., October,1975.
‘@mTc-sulfurcolloid (normal) (6)SomTcsodium pertechnetate (7):
resting populationnon-resting population
“9-sodiumiodide (15%) (8)“1-sodiumiodide (15%) (8)‘@‘l-sodiumrose bengal (9)lml.sodium rose bengal (9)
0.0370.0390.0320.100.130.68
RESULTS AND DISCUSSIONREFERENCES
1. HALL E: Effects on the embryo and fetus. In Radiobiology for the Radiologist. Hagerstown, Md., Harper & Row,
1973,pp 230—239
2. SNYDER WS, FORD MR, WARNER GG, et al. : “5―Absorbed Dose Per Unit Cumulated Activity for SelectedRadionuclides and Organs, MIRD Pamphlet No. 11. NewYork, Society of Nuclear Medicine, 1975
3. SNYDER WS, FORD MR. WARNER GG : Estimates ofSpecific A bsorbed Fractions for Radiation Sources Uniformly Distributed in Various Organs of the HeterogeneousPhantom, MJRD Pamphlet No. 12. New York, Society ofNuclear Medicine : to be published
4. GRAY H : Gray's Anatomy, 32nd edition. New York,Longmans
5. SNYDER WS, Foa.o MR, WARNER GG : Estimates ofabsorbed fractions for photon emitters within the body. InHealth Physics Division A nnual Progress Report. Oak
Ridge, Tenn., ORNL-481 I, July 31, 1972, pp 86—906. ATKINS HL, CLOUTIER Ri, LATHROPKA, et al.:
MIRD/Dose Estimate Report No 3 : Summary of currentradiation dose estimates to humans with various liver conditions from @mTc-su1furcolloid. I NucI Med 16: lO8A—108B, 1975
7. LATHROPKA, ATKINSHL, BERMANM, et al.: MIRD/Dose Estimate Report No 8: Summary of current radiationdose estimates to normal humans from @mTcas sodiumpertechnetate. I Nucl Med 17 : 74—77,1976
8. BERMAN M, BRAVERMAN LE, BURKE J, et al. : MIRD/Dose Estimate Report No 5 : Summary of current radiationdose estimates to humans from ‘@I,1241,@9,“II, @t,19, and1:5.)! as sodium iodide. I NucI Med 16: 857—860, 1975
9. FREEMAN LM, PA-I-rONDD, ROSENThALLL, et al.:MIRD/Dose Estimate Report No 7 : Summary of currentradiation dose estimates to humans from “I,124! 19, 19,and “Ias sodium rose bengal. I NucI Med 16: 1214—1217,1975
The values for cI(embryo4—r@)and @(uterus+-rh)were compared for six source organs. In general,
F(embryo4—r1) is greater than 4(utems+-r11) forenergies 30 keV or greater, sometimes approaching
twice the value of 4(uterus+-r11). These ratios fluctuate considerably.
To ascertain the variability of 4@(embryo4-rh),additional studies should be performed to investigatethe effects that the implantation site of the embryoand the relative location of the uterus to other abdominal organs have on 4(embryo—rh). The effectof the variable size of the bladder and its contents isof even greater importance to the calculation of4@(embryoE—r@).
Since radioactivity was assumed not to cross theplacenta, nonpenetrating radiation is not includedin these calculations except for activity uniformlydistributed in the total body. If, for example, 99mTc@pertechnetate did cross the placenta, and the concentration in the placenta equaled that in a 70-kg womanin whom O9mTcis uniformly distributed and has aninfinite biologic half-time, the dose to the embryofrom nonpenetrating radiations would be 0.0044rads per millicurie administered. This is approximately an order of magnitude less than the valuegiven in Table 3 for this radiopharmaceutical, whichdoes include the fraction of 99mTc uniformly distributed in the total body in the dose estimate.
Before the values given in Tables 1—3are used,the user should be fully aware of all the assumptionsand limitations inherent in these values. The assump
Volume 17, Number 9 839
TABLE 3. DOSE ESTIMATESFOR THE EMBRYO
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1976;17:836-839.J Nucl Med. Edward M. Smith and G. G. Warner Estimates of Radiation Dose to the Embryo from Nuclear Medicine Procedures
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