Form I 131 Sample: Fill & Download for Free

This seems to be a homework question. The preceding two questions I looked at were perhaps also homework questions.

Blood Volume may also be measured semi-automatically in under one hour by the BVA-100 reporting Total Blood Volume (TBV), Plasma Volume (PV) and Red Cell Volume (RCV) using the indicator dilution principle, microhematocrit centrifugation and the Ideal Height and Weight Method.The indicator or tracer, is an I-131 albumin injection. An equal amount of the tracer is injected into a known and unknown volume. Clinically, the unknown volume is the patient’s blood volume, with the tracer having been injected into the patient’s blood stream and tagged to the blood plasma. Once the tracer is injected a technician takes five blood samples which undergo microhematocrit centrifugation to extrapolate true blood volume at time 0. The concentration of the I-131in the blood is determined from the blood radioactivity against the standard which has a known I-131 dilution in a known volume. The unknown volume is inversely proportional to the concentration of the indicator in the known volume; the larger the unknown volume, the lower the tracer concentration, thus the unknown volume can be calculated. The microhematocrit data along with the I-131 indicator data provide a normalized hematocrit number, more accurate than hematocrit or peripheral hematocrit measurements.Measurements are taken 5 times in 6 minute intervals .

There are two kinds of radioactive decay questions that frequently show up. First, there is the ridiculously easy ones (like this one), where the elapsed time is some small number of half-lives. Then there are the practical ones which actually require the application of first-order kinetics.One day (24 hours) is three half-lives. The amount of the radioisotope decreases by one half over a period of time equal to the half-life.24g —→ 12g —→ 6g —→ 3g …….. amounts of I-131……….1 …………. 2 ………..3 …………….. number of half-livesTherefore, in one day (3 half-lives) the amount of I-131 will decrease from 24g to 3g.Just for grins we can pretend that this was a practical problem and do the calculations. Radioactive decay follows first-order kinetics which is described by this equation: A=Ao e^(-kt) …. where A is the “amount” of substance, the activity or the number of atoms, k is the “decay constant” which may also be represented by lambda, λ, and t is the elapsed time. The decay constant is related to the half-life: k=ln2/t½, where k=0.0866.A = 24g x e^(-0.0866 x 24) = 3.0g