Nuclear Medicine

Question 1

What is the main radionuclide used in Nuclear Medicine?

Answer 1

(Metastable) Technetium (Tc)

Question 2

What produces Tc in the nuclear medicine department?

Answer 2

A generator made from parent atom Molybdenum (Mb)

Question 3

what process is involved in Tc production

Answer 3

isomeric transition

Question 4

what is isomeric transition?

Answer 4

the production of a gamma ray without any change in atomic mass or number

Question 5

What is the half life of Technetium?

Answer 5

6 hrs

Question 6

What does the generator consist of?

Answer 6

the generator is a lead lined container with the parent radionuclide

Question 7

Where is the Mb in the generator?

Answer 7

It is adsorbed onto a column of alumina, silica or an ion-exchange resin

Question 8

What is the eluate from a Technetium generator called?

Answer 8

Sodium
pertechnetate

Question 9

Why do we need a generator?

Answer 9

Time available for processing, transporting, storage and dispensing is limited because of its short half-life

Question 10

Advantages of Molybdenum as the parent radioisotope

Answer 10

Half-life of 66hrs which allows it to be transported easily without loss of activity
This allows the daughter radioisotope to be easily produced at the facility

Question 11

how is the carrier free daughter eluted from the generator?

Answer 11

this is done by passing a solvent like saline over the column

Question 12

what are some advantages of using Tc in Nuclear Medicine?

Answer 12

6hr half life
pure gamma emitter
easy to shield
easy incorporation with other chemicals
non-toxic
rapid excretion

Question 13

How long does a typical generator last?

Answer 13

1 week

Question 14

Technetium decays with the emission of…

Answer 14

a 140 kEv gamma
ray

Question 15

What is transient equilibrium?

Answer 15

When equilibrium is reached by a parent-daughter radioactive isotope pair where the half-life of the daughter is shorter than the half-life of the parent.

Question 16

What is Molybdenum breakthrough?

Answer 16

When tiny amounts of Molybdenum are contained in the solution of sodium pertechnetate

Question 17

How is Mo breakthrough measured?

Answer 17

Comparing eluate activity with and without Pb shielding using a well counter

Question 18

What imaging device is used in Nuclear Medicine?

Answer 18

Gamma camera

Question 19

What is the gamma camera combined with?

Answer 19

a Collimator

Question 20

What is the purpose of the collimator on the gamma camera?

Answer 20

to establish a relationship
between the distribution of isotope in the patient and the
position at which gamma rays are detected in the crystal

Question 21

What is the gamma camera made of?

Answer 21

sodium iodide doped with thalium

Question 22

What effect does crystal thickness have on detector efficiency and spatial resolution?

Answer 22

The thicker the crystal, greater detector efficiency but lower spatial resolution

Question 23

The amplitude of the signal detected in the PM tube is proportional to what?

Answer 23

The amplitude of the signal detected is proportional to the amount of light emitted

Question 24

The light emitted is proportional to what?

Answer 24

The light emitted is proportional to the energy of the gamma ray

Question 25

What is the Z pulse?

Answer 25

the summation of the PM tube outputs provides an energy, which is proportional to the total light produced in the crystal

Question 26

Where does the Z pulse go?

Answer 26

to the pulse height analyser (PHA)

Question 27

What does the Pulse Height Analyser do?

Answer 27

PHA selects the isotope peak & excludes compton scatter

Question 28

What is the Z pulse proportional to?

Answer 28

The Z pulse is proportional to the total light output from one scintillation

Question 29

what happens if Z pulse is accepted?

Answer 29

the positional circuitry is triggered to locate the gamma ray interaction

Question 30

what is the PHA purpose?

Answer 30

choice of photo peak exclude compton scatter

Question 31

What is the goal of Nuclear Medicine?

Answer 31

To map the distribution of radiotracers

Question 32

What renders gamma rays not useful for accurate measurement of radionuclide location?

Answer 32

when gamma rays scatter in the body first and change direction

Question 33

What does the collimator design affect?

Answer 33

spatial resolution sensitivity size of FOV magnification/minification

Question 34

What does spatial resolution depend on?

Answer 34

diameter of holes in the collimator length of holes septal thickness distance of pt from collimator surface intrinsic resolution of detector

Question 35

What is the point spread function (PSF)?

Answer 35

a profile of measured counts as a function of position across a point source

Question 36

What is the modulation transfer function?

Answer 36

MTF is one way to more completely characterise the ability of a system to reproduce spatial frequencies

Question 37

How is the MTF calculated?

Answer 37

It is calculated as the fourier transform of the PSF or LSF and is a plot of the response of a system to different spatial frequencies

Question 38

What is the relationship between resolution and sensitivity?

Answer 38

If resolution is increased by a factor of 2, the sensitivity is decreased by a factor of 4

Question 39

What is the unit of radioactive decay?

Answer 39

Becquerel (in NM, we use Mega Becquerel [MBq])

Question 40

what has replaced lung perfusion with technetium

Answer 40

CT Pulmonary Angiogram

Question 41

How is Tc predominantly excreted?

Answer 41

Urination

Question 42

What is encouraged to lower body dose post NM imaging?

Answer 42

Frequent urination/bladder emptying

Question 43

What effect does the collimator have on the gamma camera?

Answer 43

it reduces sensitivity to improve spatial resolution and ensure image accuracy.

Question 44

What is the typical administered activity for an isotope bone scan?

Answer 44

400-750 MBq

Question 45

What is often used for Lung Perfusion Scans?

Answer 45

technetium-99m macroaggregated albumin (Tc-99m MAA)

Question 46

What is the weakest link of Nuc Med, and what should be done because of it?

Answer 46

The collimator is the weakest link. Keep the patient close to the collimator

Question 47

What is intrinsic resolution determined by?

Answer 47

Multiple compton scattering in detector crystal ( minor limitation ) Statistical fluctuations in the distribution of light photons between PM tubes ( major limitation )

Question 48

The collimator improves..

Answer 48

The spatial resolution of the gamma camera

Question 49

Clinical uses of Nuclear Medicine

Answer 49

Helps in early diagnosis Determines severity of disease Determines response to therapy