Concept explainers
Videos
A counting system has a background of 360 counts during a 20-minute counting period. What is the lower limit of detection with this system for counting times of
(a) 2 minutes?
(b) 20 minutes?
(c) 200 minutes?
(a)
Lower limit of detection for counting times of 2 min
Answer to Problem 9.14P
Lower limit detection is 24 cpm.
Explanation of Solution
Given:
Time during which gross count was made,
Background count,
Time during which background count was made,
Formula used:
Background counting rate,
Lower limit of detection,
Calculation:
Background counting rate,
Lower limit of detection,
Conclusion:
Lower limit detection is 12 cpm.
(b)
Lower limit of detection for counting times of 20 min
Answer to Problem 9.14P
Lower limit detection is 4.6 cpm.
Explanation of Solution
Given:
Time during which gross count was made,
Background count,
Time during which background count was made,
Formula used:
Background counting rate,
Lower limit of detection,
Calculation:
Background counting rate,
Lower limit of detection,
Conclusion: Lower limit detection is 4.6 cpm.
(c)
Lower limit of detection for counting times of 200 min
Answer to Problem 9.14P
Lower limit detection is 658 cpm.
Explanation of Solution
Given:
Time during which gross count was made,
Background count,
Time during which background count was made,
Formula used:
Background counting rate,
Lower limit of detection,
Calculation:
Background counting rate,
Lower limit of detection,
Conclusion:
Lower limit detection is 3.3 cpm.
Want to see more full solutions like this?
Chapter 9 Solutions
Introduction To Health Physics
- The (effective) dose to a patient can be measured in milli-Serverts (mSv) or expressed as the time taken to receive the equivalent dose from background radiation. A certain radiograph gives a 1.232 mSv dose which is equivalent to a background radiation dose of 32 weeks.a)How many days in 32 weeks? Give your answer as a whole number. b)Using the information for the radiograph in this question, calculate the UK daily background dose (in mSv/day). Give your answer to 5 decimal places and use it to this accuracy, if needed in subsequent calculations. c)Another radiograph has a 0.0054 mSv dose. Work out the equivalent background dose (in days) for this radiograph. Give your answer to 2 decimal places and use it to this accuracy in any subsequent calculations. d)How many hours is the number of days in part c) equivalent to? Give your answer to 2 decimal places.arrow_forwardIf a sample emits 2000 counts per second when the detector is 1 meter from the sample, how many counts per second would be observed when the detector is 3 meters from the sample? --Using the sample in above, how many counts per second would be observed when the detector is 10 meters away from the sample?arrow_forwardEstimate the exposure rate 2 m from 4 Ci sources of 57Co,22Na,65Zn?Exposure Rate constant for 57Co=0.9 (R.cm2) / (hr.mCi)Exposure Rate constant for 22Na =12 (R.cm2) / (hr.mCi)Exposure Rate constant for 65Zn =2.7 (R.cm2) / (hr.mCi)arrow_forward
- Q_ A person's hand receives a radiation dose at a rate of 50mSvh-1 at a distance of 1cm from a source. What would the dose rate be if the person's hand is 18cm from source?arrow_forwardA radioactive source is producing 1.50 MeV gamma rays. If two detectors are placed 4.00 m and 7.00 m away respectively, what is the ratio of the measured intensities of the near detector over the far detector (I2/I1)? Do NOT include units in your answer answer to 2 decimal places.arrow_forwardCalculate the CT pitch factor for a scan length 16 cm, 20 tomographic sections an the nominal slice thickness is 5 mm.arrow_forward
- A radiation worker received a gonad dose 25 mGy over the year. If 100% of dose was from x-ray what is the equivalent dose ? a) 25 mGy b) 25 msvarrow_forwardRadiation from a point source obeys the inverse-square law. If a Geiger counter 1 m from a small sample registers 360 counts per minute, what will be its counting rate 2 m from the source? What will it be 3 m from the source?arrow_forwardUsing the systematics of exponential processes, the time scale for getting out of a pandemic at its peak through exponential decay of the infection rate or the death rate is estimated from: If the delta variant death rate per day (Po) peaked at 2000 in late September and declined at the national rate of − 1% per day, what is t, the time in days to defeat the virus (i.e. time until the last person dies)? answer choices: 350 525 450 760arrow_forward
- IB. Wliv is a PET scan more accurate than a SPECT scan?arrow_forwardA particular radioactive source produces 100 mrad of 2-MeV gamma rays per hour at a distance of 1.0 m. (a) How long could a person stand at this distance before accumulating an intolerable dose of 1 rem? (b) Assuming the gamma radiation is emitted uniformly in all directions, at what distance would a person recieve a dose of 10 mrad/h from this source? dont provode hand written solutionarrow_forward1. Lead shield that is 0.27 mm thick is equivalent to 1 HVL. How thick should the lead shield be if the radiation intensity is to be reduced to 12.5 % of its original values? 2. A worker at a reactor is composed to 20 mead of slow neutron whose RBE is 4. What is dose equivalent of this exposure? What precentage of his allowed annual dose equivalent did he received?arrow_forward
Modern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage Learning
University Physics Volume 3PhysicsISBN:9781938168185Author:William Moebs, Jeff SannyPublisher:OpenStax