Nuclear Medicine

Question 1

what is nuclear medicine?

Answer 1

It is a branch of medicine which involves application of radioactive substances for imaging and therapy

Question 2

what are the steps involved in nuclear medicine?

Answer 2

1. A suitable radiopharmaceutical (or radionuclide) is introduced into the patient;
2. The radiopharmaceutical is allowed to concentrate in a specific organ;
3. The organ is scanned using an appropriate scanner, e.g. gamma camera

Question 3

what is difference b/w x-rays and nuclear medicine?

Answer 3

1. x-rays provide structural and anatomical function

2. nuclear medicine provide physiological and functional information

Question 4

Define radiopharmaceutical

Answer 4

• radio means radioactive element and pharmaceutical means drug or medicine
• therefore, radiopharmaceutical is a radioactive element/substance that can be administered into the body for diagnostic and therapeutic purposes

Question 5

which radioisotope is used in DTPA scan or renogram?

Answer 5

technetium (gamma ray emitter) and DTPA (technetium labelled DTPA) is excreted by kinder which allows to measure the renal function and GFR

Question 6

Define radioisotope

Answer 6

isotope is an element with same atomic number but different atomic mass so radioisotope is any isotope that is radioactive

Question 7

why isotopes become radioactive and explain radioactive decay?

Answer 7

• due to an unstable nucleus
• the strong nuclear forces do not generate enough NBE to hold the nucleus together permanently
• therefore, to attain stability the nucleus emits an extra energy in the form of radiation and converts into a stable nucleus of lower energy
• this is called radioactive decay

Question 8

what are the features of stable nucleus?

Answer 8

1. equal number of protons and neutrons (lighter elements)

2. strong nuclear binding energy (NBE) to hold the nucleus together

Question 9

what are three modes of decay?

Answer 9

1. alpha decay or alpha particle emission
2. beta decay or beta particle emission
3. gamma decay

Question 10

what are the features of alpha decay?

Answer 10

1. rapid emission of an alpha particle (consist of 2 neutrons and 2 protons)
2. the atomic mass of nucleus should >150 and
3. the nucleus must have too few neutrons for the number of protons
4. they have a short range in tissue so have little practical application

Question 11

what are the features of beta decay?

Answer 11

1. conversion of neutrons to protons and vice versa
2. a particle have a mass equal to that of an electron is ejected from nucleus
3. nucleus should contain too many neutrons
4. the particle may have either positive (positron) or negative charge (negatron)

Question 12

how many steps are there in decay process and what is decay scheme?

Answer 12

Decay process - can either be a single step with mode of decay or a multiple step process with one or many modes of decay
decay scheme - the graphical representation of decay process

Question 13

Define

1. physical half life

2. activity

Answer 13

1. physical half life - it is the time taken by the radioactive isotope sample to decay to one half of its original value
2. activity - total number of disintegration per second
   - it is measured in becquerel (Bq)
   - 1Bq = 1 nuclear disintegration per second

Question 14

define

1. biological half life

2. effective half life

Answer 14

1. biological half life - it is the time taken by any chemical in an organ to reduce to half its original concentation
2. effective half life - it is the time taken by certain radionuclide in a certain organ to be reduced to half its original activity

Question 15

what are the properties of an ideal radioisotope?

Answer 15

1. Have a short half-life
2. Emit gamma-rays of relatively low energy
3. Emit no particles
4. Be added to the pharmaceutical without altering it’s chemical nature
5. Be readily excreted
6. Be easily generated

Question 16

what is gamma camera?

Answer 16

• specialised imaging equipment
• able to detect gamma photons
• does NOT produce radiation
• design is evolving continuously

Question 17

what does the gamma camera consists of?

Answer 17

collimator, detector, photomultiplier, electronics (used for creating images)

Question 18

what is the detector in gamma ray

1. made of
2. its function
3. efficiency

Answer 18

1. made up of scintillation crystal, usually sodium iodide doped with thallium
2. its function is convert gamma radiations into visible light
3. inefficient process - only about 10% of gamma radiation is converted to light

Question 19

what is structure and function of photomultiplier tube?

Answer 19

• consist of photocathode (where the the incoming light photon hits) , dynode (electron is passed through this) and anode (sends photomultiplier outputs as electric impulse)
• they are closely packed for optimum light detection

Question 20

what is SPECT and what are its features?

Answer 20

SPECT - single photon emission computed tomography

1. uses similar radiopharmaceuticals as 2D imaging - e.g. technetium based
2. mode of acquisition changes, i.e. how the data is acquired and processed
3. cross sectional imaging

Question 21

what is PET and what are its features?

Answer 21

PET - positron emission tomography

1. diffrent pharmaceutical to planar and SPECT imaging - FDG (flurodeoxyglucose)
2. radiopharmaceuticals decay by the emission of positrons
3. annihilation - positron travels a few mm then interacts with an electron -> 2 gamma photons are emitted and 180degree opposed to each other
4. the camera detects the gamma rays to produce the image

Question 22

name two 3D imaging techniques?

Answer 22

1. SPECT

2. PET

Question 23

what is the role of NM?

Answer 23

1. Physiological measurement
Lung, heart, kidney, bone
2. Diagnosis of primary tumours
3. Diagnosis of secondary tumours (metastases)
4. Radionuclide therapy
2D- planar imaging technique
3D- SPECT and PET