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33 Cards in this Set
- Front
- Back
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Post decay factor formula
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e^-lambda(time)
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Pre decay factor formula
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e^lamdba (time)
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formula to figure how much time it taks an RP to decay
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t=T1/2 ln (Ao/A) / .693
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formula to figure out the half life of RP if you have the time, original activity & current activity
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T1/2=t(.693) / ln (Ao/A)
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Concentration formula
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activity/volume = concentration
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Standard deviation counts formula
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Sq. root of (c/t)
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%SD counts formula
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% SD= 100/ sq. root of radioactivity of nuclei decaying (which is n)
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SD formula
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sq root of : (sum deviations^2 / total # of data minus 1)
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If you have a known decay factor how do you figure decay based on variable numbers of half-lives?
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Known decay factor to the power of however many half lives. Ex. 3 half lives of TC with a DF of .8909 over 3 half lives = (.8909)^3
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Unknown decay factor (or how to find the current activity if you have original activity) formula
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A=Ao (e^-lambda (time)
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How to decay nuclei formula
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N=(No) x e^ -lambda (t) ... post
N=No x e ^lambda(t)... pre |
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Decay rate formula
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DR=lambda (N)
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Formula to decay concentration
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Concentration x e^ -lambda(t)
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Formula figure volume desired
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V=Activity/concentration
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Decay constant aka lambda
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.693/Half life of RN
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To find total number of nuclei aka N
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DR/lambda=N
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to find acitivy if you have decay rate per MINUTE
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DRdpm x (Ci / 2.22 x 10^12dpm) OR
mCi/2.22 x 10^9) |
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True value vs. theoretical value
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True=actual
theoretical= math figured value |
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2 types of value errors
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Systematic
Random |
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Systematic error is caused by?
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miscalibrated or miscalculating machines
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random error is caused by?
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uncontrollable errors i.e voltage fluctuations
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Mean
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average value add all and divide by total number
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Mode
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value that occurs most often
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median
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middle value
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Accuracy means?
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how close measurements are to true value
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Precision?
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reproducibility of measurements
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Poisson distribution
(gaussian-for large number of events or normal distribution) |
model for radom events such as RA disitrigrations
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Standard deviation means?
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how tightly events cluster around a mean
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SD of 1 is about what %? 2? 3?
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1SD=68%; 2SD=95%; 3SD=99%
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If you have 1000 counts in 5 min what is the SDcount error rate?
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1000c/5m=200cpm so SD count=sq. root 200=14.1% error rate
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Higher count rates = higher or lower errors?
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Higher errors- dead time of gamma camera
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Effective half life formula
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Te= (Tp x Tb)/ (Tp +Tb)
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Formula to figure slope in GM counter
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Slope=C2-C1/V2-V1
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