METHODS
—
DOS] tETRIC EQUATIONS
Declining continuous uptake of radioactive dietary items was mathematicall modeled for each nuclide of concern.
The following general equations were
used
ype =
uU,/Fy - a
.
fy (s XiKi
i K {Kg
Ap? =
o
le
=
-(\+Kp )t
~CAtK: te
E"
-e
i’*))
"
|
dp?
L
.
1
=-(A4K.)t
iv)
q- 4° (i Xie
£
Xi
(e (AtKg)e _ . (AK;. )t))
1 (2
. K.-K
1
1 iE
D=f
=(,+K. et
G KX; e A'S)
L
KK
1
£E
e
-
(A+Kg)t
r
i
x;
x
+
(K E +A) (K,1 +A)
t
+ q°
or
(1)
» and
(2)
.
-(A+K;)
(Xicke
,
{j-e
(
X+
Kg)
e
-(K. +A
(Kj
*)
-(A 4K;1 Je ),
(3)
i
where
t
= time post onset of uptake, days,
X
= instantaneous fraction of atoms decaying per unit time, day!
P° = initial atom ingestion rate, atoms day},
Kj = instantaneous fraction of atoms removed from compartment i by physiological
mechanisms, day"! ,
Xj = compartment i deposition fraction,
t
X; = the number of atoms in compartment i relative to the number in all compart-
ments at the onset of uptake (t#=0),
U
= instantaneous urine activity concentration, Bg gol,
U. = subject urine excretion rate, & day—l,