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- Jul 15, 2015
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See images for question/explanation and associated figures.
The passage states that the half-life of Co60 is 5 years and the half-life of X is 1 year.
The explanation goes on to say that "Because X has a shorter half-life, it is logical that it would release more radiation in the same period of time because it undergoes decay more quickly"
"If GKS-Co involved radioactive material that decayed much more slowly than that in GKS-X, we would expect the GKS-Co tumor-reducing effects to catch up to or surpass GKS-X as time passed."
The above explanations seems contradictory. One says X undergoes decay more quickly, the other is implying Co does not "involve radioactive material that decays much more slowly".
Also, the trend shown in the table does imply X is releasing more radiation/time, but as you go from months 3 to 6, you see that the change in tumor volume is actually greater for Co than X (X:-0.98 vs Co:-0.21) making me think that if you continued to monitor tumor volume past 6 months, Co tumor-reducing effect would indeed catch up to X.
Why is C wrong? I can see A is true, but...the explanation implies C is wrong and that Co does NOT undergo decay much more slowly. Maybe if the Q-stem asked why X is more effective than Co but it's just asking about their capacities in general.
The passage states that the half-life of Co60 is 5 years and the half-life of X is 1 year.
The explanation goes on to say that "Because X has a shorter half-life, it is logical that it would release more radiation in the same period of time because it undergoes decay more quickly"
"If GKS-Co involved radioactive material that decayed much more slowly than that in GKS-X, we would expect the GKS-Co tumor-reducing effects to catch up to or surpass GKS-X as time passed."
The above explanations seems contradictory. One says X undergoes decay more quickly, the other is implying Co does not "involve radioactive material that decays much more slowly".
Also, the trend shown in the table does imply X is releasing more radiation/time, but as you go from months 3 to 6, you see that the change in tumor volume is actually greater for Co than X (X:-0.98 vs Co:-0.21) making me think that if you continued to monitor tumor volume past 6 months, Co tumor-reducing effect would indeed catch up to X.
Why is C wrong? I can see A is true, but...the explanation implies C is wrong and that Co does NOT undergo decay much more slowly. Maybe if the Q-stem asked why X is more effective than Co but it's just asking about their capacities in general.
