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The figure shows a patient undergoing a scan in a cylindrical device. The P E T system uses two gamma ray photons produced by positron electron annihilation. These gamma rays are emitted in opposite directions.
A PET system takes advantage of the two identical γ size 12{γ} {} -ray photons produced by positron-electron annihilation. These γ size 12{γ} {} rays are emitted in opposite directions, so that the line along which each pair is emitted is determined. Various events detected by several pairs of detectors are then analyzed by the computer to form an accurate image.

Phet explorations: simplified mri

Is it a tumor? Magnetic Resonance Imaging (MRI) can tell. Your head is full of tiny radio transmitters (the nuclear spins of the hydrogen nuclei of your water molecules). In an MRI unit, these little radios can be made to broadcast their positions, giving a detailed picture of the inside of your head.

Simplified MRI

Section summary

  • Radiopharmaceuticals are compounds that are used for medical imaging and therapeutics.
  • The process of attaching a radioactive substance is called tagging.
  • [link] lists certain diagnostic uses of radiopharmaceuticals including the isotope and activity typically used in diagnostics.
  • One common imaging device is the Anger camera, which consists of a lead collimator, radiation detectors, and an analysis computer.
  • Tomography performed with γ size 12{γ} {} -emitting radiopharmaceuticals is called SPECT and has the advantages of x-ray CT scans coupled with organ- and function-specific drugs.
  • PET is a similar technique that uses β + size 12{β rSup { size 8{+{}} } } {} emitters and detects the two annihilation γ size 12{γ} {} rays, which aid to localize the source.

Conceptual questions

In terms of radiation dose, what is the major difference between medical diagnostic uses of radiation and medical therapeutic uses?

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One of the methods used to limit radiation dose to the patient in medical imaging is to employ isotopes with short half-lives. How would this limit the dose?

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A neutron generator uses an α size 12{α} {} source, such as radium, to bombard beryllium, inducing the reaction 4 He + 9 Be 12 C + n . Such neutron sources are called RaBe sources, or PuBe sources if they use plutonium to get the α s. Calculate the energy output of the reaction in MeV.

5.701 MeV

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Neutrons from a source (perhaps the one discussed in the preceding problem) bombard natural molybdenum, which is 24 percent 98 Mo . What is the energy output of the reaction 98 Mo + n 99 Mo + γ ? The mass of 98 Mo is given in Appendix A: Atomic Masses , and that of 99 Mo is 98.907711 u.

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The purpose of producing 99 Mo (usually by neutron activation of natural molybdenum, as in the preceding problem) is to produce 99m Tc. Using the rules, verify that the β decay of 99 Mo produces 99m Tc . (Most 99m Tc nuclei produced in this decay are left in a metastable excited state denoted 99m Tc .)

42 99 Mo 57 43 99 Tc 56 + β + v ¯ e

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(a) Two annihilation γ size 12{γ} {} rays in a PET scan originate at the same point and travel to detectors on either side of the patient. If the point of origin is 9.00 cm closer to one of the detectors, what is the difference in arrival times of the photons? (This could be used to give position information, but the time difference is small enough to make it difficult.)

(b) How accurately would you need to be able to measure arrival time differences to get a position resolution of 1.00 mm?

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[link] indicates that 7.50 mCi of 99m Tc size 12{"" lSup { size 8{"99m"} } "Tc"} {} is used in a brain scan. What is the mass of technetium?

1 . 43 × 10 9 g size 12{1 "." "43" times "10" rSup { size 8{ - 9} } `g} {}

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The activities of 131 I size 12{"" lSup { size 8{"131"} } I} {} and 123 I size 12{"" lSup { size 8{"123"} } I} {} used in thyroid scans are given in [link] to be 50 and 70 μ Ci , respectively. Find and compare the masses of 131 I and 123 I in such scans, given their respective half-lives are 8.04 d and 13.2 h. The masses are so small that the radioiodine is usually mixed with stable iodine as a carrier to ensure normal chemistry and distribution in the body.

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(a) Neutron activation of sodium, which is 100% 23 Na , produces 24 Na , which is used in some heart scans, as seen in [link] . The equation for the reaction is 23 Na + n 24 Na + γ . Find its energy output, given the mass of 24 Na is 23.990962 u.

(b) What mass of 24 Na size 12{"" lSup { size 8{"24"} } "Na"} {} produces the needed 5.0-mCi activity, given its half-life is 15.0 h?

(a) 6.958 MeV

(b) 5 . 7 × 10 10 g size 12{5 "." 7 times "10" rSup { size 8{ - "10"} } `g} {}

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Questions & Answers

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how many topic are in physics
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a ripple tank experiment a vibrating plane is used to generate wrinkles in the water .if the distance between two successive point is 3.5cm and the wave travel a distance of 31.5cm find the frequency of the vibration
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straight line motion is called linear motion
then what
linear motion is a motion in a line, be it in a straight line or in a non straight line. It is the rate of change of distance.
your are wrong Saeedul
Linear motion is a one-dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimension
is a one-dimensional motion along a straight line, and can therefore be described mathematically using only one spatial dimensions. 
what is a classical electrodynamics?
what is dynamics
dynamic is the force that stimulates change or progress within the system or process
what is the formula to calculate wavelength of the incident light
David Reply
if a spring is is stiffness of 950nm-1 what work will be done in extending the spring by 60mmp
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State the forms of energy
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Word : Mechanical wave Definition : The waves, which need a material medium for their propagation, e.g., Sound waves. \n\nOther Definition: The waves, which need a material medium for their propagation, are called mechanical waves. Mechanical waves are also called elastic waves. Sound waves, water waves are examples of mechanical waves.t Definition: wave consisting of periodic motion of matter; e.g. sound wave or water wave as opposed to electromagnetic wave.h
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a wave which require material medium for its propagation
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SI.unit of power is.watt=j/c.but kw.and Mw are bigger.umots
What is physics
aish Reply
study of matter and its nature
The word physics comes from a Greek word Physicos which means Nature.The Knowledge of Nature. It is branch of science which deals with the matter and energy and interaction between them.
why in circular motion, a tangential acceleration can change the magnitude of the velocity but not its direction
Syafiqah Reply
because it is balanced by the inward acceleration otherwise known as centripetal acceleration
What is a wave
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Tramsmission of energy through a media
is the disturbance that carry materials as propagation from one medium to another
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find the triple product of (A*B).C given that A =i + 4j, B=2i - 3j and C = i + k
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Difference between north seeking pole and south seeking pole
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Practice Key Terms 6

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