Physics and Radiobiology of Nuclear Medicine

(Jeff_L) #1

Answer
For^201 Tl,


A= 10 ×3.7 × 107 =3.7 × 108 dps

Using Eq. (3.2),


Because 1 g · atom^201 Tl =201 g^201 Tl =6.02 × 1023 atoms of^201 Tl (Avogadro’s
number),


=46.7 × 10 −^9 g
=46.7 ng

Therefore, 10 mCi of^201 Tl contains 1.4 × 1014 atoms and 46.7 ng.


Problem 3.2
At 10:00 a.m., the 99mTc radioactivity was measured as 150 mCi (5.55 GBq)
on Wednesday. What was the activity at 6 a.m. and 3 p.m. on the same day
(t1/2of 99mTc =6 hr)?


Answer
Time from 6 a.m. to 10 a.m. is 4 hr:


At=150 mCi (5.55 GBq)
A 0 =?

Using Eq. (3.4)


150 =A 0 e+0.1155×^4
A 0 = 150 ×e0.462
= 150 ×1.5872
=238.1 mCi (8.81 GBq) at 6 a.m.

Time from 10 a.m. to 3 p.m. is 5 hr:


A 0 =150 mCi
At=?

lfor m99 Tc hr^1

0 693

6

==0 1155 −

.

.

Mass of Tl in mCi MBq

201 1.40 10^14

(^1037023)


201

602 10

()=

××

. ×

N

A

==

×

×

− =×

l

37 10

2 638 10

140 10

8
6

. 14

.

. atoms


l=
×××

=×−−

0 693

304246060

2 638 10^61

.

.

. sec


28 3. Kinetics of Radioactive Decay

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