<< Chapter < Page Chapter >> Page >
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?

Got questions? Get instant answers now!

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?

Got questions? Get instant answers now!

Problems&Exercises

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

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

(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?

Got questions? Get instant answers now!

[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} {}

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

(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} {}

Got questions? Get instant answers now!

Questions & Answers

Why is the sky blue...?
Star Reply
It's filtered light from the 2 forms of radiation emitted from the sun. It's mainly filtered UV rays. There's a theory titled Scatter Theory that covers this topic
Mike
A heating coil of resistance 30π is connected to a 240v supply for 5min to boil a quantity of water in a vessel of heat capacity 200jk. If the initial temperature of water is 20°c and it specific heat capacity is 4200jkgk calculate the mass of water in a vessel
fasawe Reply
A thin equi convex lens is placed on a horizontal plane mirror and a pin held 20 cm vertically above the lens concise in position with its own image the space between the undersurface of d lens and the mirror is filled with water (refractive index =1•33)and then to concise with d image d pin has to
Azummiri Reply
Be raised until its distance from d lens is 27cm find d radius of curvature
Azummiri
what happens when a nuclear bomb and atom bomb bomb explode add the same time near each other
FlAsH Reply
A monkey throws a coconut straight upwards from a coconut tree with a velocity of 10 ms-1. The coconut tree is 30 m high. Calculate the maximum height of the coconut from the top of the coconut tree? Can someone answer my question
Fatinizzah Reply
v2 =u2 - 2gh 02 =10x10 - 2x9.8xh h = 100 ÷ 19.6 answer = 30 - h.
Ramonyai
why is the north side is always referring to n side of magnetic
sam Reply
who is a nurse
Chilekwa Reply
A nurse is a person who takes care of the sick
Bukola
a nurse is also like an assistant to the doctor
Gadjawa
explain me wheatstone bridge
Malik Reply
good app
samuel
Wheatstone bridge is an instrument used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component.
MUHD
Rockwell Software is Rockwell Automation’s "Retro Encabulator". Now, basically the only new principle involved is that instead of power being generated by the relative motion of conductors and fluxes, it’s produced by the modial interaction of magneto-reluctance and capacitive diractance. The origin
Chip
what refractive index
Adjah Reply
write a comprehensive note on primary colours
Harrison Reply
relationship between refractive index, angle of minimum deviation and angle of prism
Harrison
Who knows the formula for binding energy,and what each variable or notation stands for?
Agina Reply
1. A black thermocouple measures the temperature in the chamber with black walls.if the air around the thermocouple is 200 C,the walls are at 1000 C,and the heat transfer constant is 15.compute the temperature gradient
Tikiso Reply
what is the relationship between G and g
Olaiya Reply
G is the u. constant, as g stands for grav, accelerate at a discreet point
Mark
Is that all about it?
Olaiya
pls explain in details
Olaiya
G is a universal constant
Mark
g stands for the gravitational acceleration point. hope this helps you.
Mark
balloon TD is at a gravitational acceleration at a specific point
Mark
I'm sorry this doesn't take dictation very well.
Mark
Can anyone explain the Hooke's law of elasticity?
Olaiya Reply
extension of a spring is proportional to the force applied so long as the force applied does not exceed the springs capacity according to my textbook
Amber
does this help?
Amber
Yes, thanks
Olaiya
so any solid can be compressed how compressed is dependent upon how much force is applied F=deltaL
Amber
sorry, the equation is F=KdeltaL delta is the triangle symbol and L is length so the change in length is proportional to amount of Force applied I believe that is what Hookes law means. anyone catch any mistakes here please correct me :)
Amber
I think it is used only for solids and not liquids, isn't it?
Olaiya
basically as long as you dont exceed the elastic limit the object should return to it original form but if you exceed this limit the object will not return to original shape as it will break
Amber
Thanks for the explanation
Olaiya
yh, liquids don't apply here, that should be viscosity
Chiamaka
hope it helps 😅
Amber
also, an object doesnt have to break necessarily, but it will have a new form :)
Amber
Yes
Olaiya
yeah, I think it is for solids but maybe there is a variation for liquids? that I am not sure of
Amber
ok
Olaiya
good luck!
Amber
Same
Olaiya
aplease i need a help on spcific latent heat of vibrations
Bilgate
specific latent heat of vaporisation
Bilgate
how many kilometers makes a mile
Margaret Reply
about 1.6 kilometres.
Faizyab
near about 1.67 kilometers
Aakash
equal to 1.609344 kilometers.
MUHD
Practice Key Terms 6

Get the best College physics course in your pocket!





Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics' conversation and receive update notifications?

Ask