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Nuclear Med > week 3-4 > Flashcards

week 3-4 Flashcards

1
Q

what are the 3 types of administration of radiotracers

A
  • ingestion
  • inhalation
  • injection
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2
Q

what are the differences between NM and x-ray imaging

A

NM
- requires injection of radiopharmaceutical. the gamma ray emitted from the patient is detected by the cameras which creates images
X-ray
- images are formed by passing x-rays through the body to the image receptor placed behind the body

NM
- patient is radioactive
X-ray
- patient is not radioactive

NM
- provides functional information
X-ray
- provides anatomical information

NM
- gamma camera does not produce radiation
X-ray
- X-ray tube produces radiation

NM
- system/organ senstive
X-ray
- not system/organ sensitive

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3
Q

advantages of NM imaging

A
  • non invasive and minimal risk to patients
  • patient can be imaging over several hours without additional radiation dose
  • provide qualitative information
  • physiological changes take place before morphological changes
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4
Q

most common form on NM imaging

A

static/ planar acquisition

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5
Q

what is a static/ planar acquisition

A
  • single shot
  • study is completed either at the end of specified time or counts
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6
Q

what is a dynamic imaging

A
  • study changes overtime
  • imaging is undertaken while radiotracer is administered in a patient
  • time per frame is dependent on the physiologic changes that is measured
  • for purpose of imaging alone, longer time per frame are generally used in order to provide sufficient imaging statistics for each frame
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7
Q

what is whole body imaging

A
  • move and shoot
  • imaging of the whole body is acquired in one image
  • continuous movement and imaging
  • imaging time is dependent on the speed of the imaging couch
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8
Q

why is MUGA scan used

A
  • imaging of a moving organ
  • imaging the heart poses challenges due to the heart’s movement
  • insufficient counts due to short acquisition time
  • long acquisition time results in a blurred image due to overlapping of moving parts
  • therefore, MUGA scan is used
  • electrocardiographic (ECG) gating is used to synchronise image acquisition with the patient’s heart rate
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9
Q

factors that affect image quality

A
  • collimators type
  • distance of detectors to patient
  • time per image
  • photopeak selection
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10
Q

primary function of collimators

A

accurate spatial localisation

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11
Q

5 types of collimators

A
  • low energy high resolution (LEHR)
  • low energy general purpose (LEGP)
  • medium energy general purpose (MEGP)
  • high energy general purpose (HEGP)
  • pinhole collimators
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12
Q

what is low energy collimators used for

A

nuclides emitting photons up to 160keV

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13
Q

what is medium energy collimators used for

A

nuclides emitting photos between 160keV to 250keV

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14
Q

what is high energy collimators used for

A

nuclides emitting photos >250keV

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15
Q

key artefacts in NM

A
  1. movement
  2. cold artefacts - seen as photophenic defects
    - metallic implants, accessories, etc
  3. hot artefacts - seen as areas of increased uptake
    - injection site artefacts
    - contamination artefacts
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16
Q

common indication for a bone scan

A
  • skeletal metastatic disease and staging
  • trauma/ fractures
  • infection
  • metabolic bone disease and other benign osteopathies (eg Paget’s disease, fibrous dysplasia)
  • avascular necrosis
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17
Q

advantages of bone scan

A
  • high sensitivity for cortical lesions
  • ease of surveying the whole skeleton
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18
Q

disadvantages of bone scan

A
  • non-specific
  • any cause of increased metabolic activity whether due to metastatic disease, primary bone tumour, inflammation of trauma can cause increased tracer uptake
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19
Q

explain the bone scan uptake mechanism

A
  • diphosphonate is absorbed onto the surface of bone especially at sites of new bone formation
  • uptake will depend on local vascularity and the degree of osteoblastic activity
20
Q

patient preparation for a bone scan

A
  • ensure patient well hydrated and void frequently
  • void before scan
  • remove all metal objects before imaging
  • note location of pacemaker, colostomy bag etc
21
Q

why must patients hydrate themselves for bone scan

A
  • allow rapid excretion of radiopharmaceutical via kidneys
  • minimise radiation dose to bladder
  • pubic lesions may be obscured by bladder activity
  • to obtain good quality image
22
Q

what is the average injection-to-imaging time

A

2-4 hours

23
Q

patient positioning for a bone scan

A
  • supine
  • elbows straight with palms on lateral side of thighs
24
Q

3 phases in a triphasic bone scan

A
  • phase 1: angiographic/ flow
  • phase 2: blood pool
  • phase 3: delayed
25
Q

most common indication for a renal MAG3 study

A

assessment of possible obstruction in urinary system

26
Q

characteristics of Tc99m- MAG3

A
  • functional radiopharmaceutical
  • high extraction fraction
  • tracer of choice for patients with poor renal function
27
Q

imaging type for renal imaging

A
  • dynamic imaging
  • static pre and post void
28
Q

purpose of Lasix administration

A

to differentiate between dilated renal collecting system from an obstructed renal collecting system

  • dilated, unobstructed: kidneys increases urine flow rate due to increased in urine output
  • dilated due to obstruction: kidneys unable to increase urine flow rate
29
Q

3 phases of kidney time activity

A
  • vascular phase: represents uptake
  • transit phase: represents transit through kidney
  • elimination phase: excretion from the kidney and expulsion down the ureter
30
Q

normal split function of kidneys

A

44%/56%

31
Q

how does collimator type affect image quality

A

medium and general purpose collimator degrades image contrast of a bone scan

32
Q

how does distance of detector affect image quality

A

the closer the detector is to the source (patient), the better the resolution

33
Q

how does time affect image quality

A

the longer the detector stays at a spot, the more photons it can capture, giving rise to better resolution

34
Q

what are some steps in proper handling of radiopharmaceuticals

A
  • correct dose given to correct patient
  • correct radioisotope when measuring dose
  • activity within acceptable range
  • radiopharm smoothly administered to patient
35
Q

radiopharmaceutical for bone scan

A
  • analogues of calcium, hydroxyl or phosphate

eg. Tc-99m diphosphate:
- 99mTc-MDP (methylene diphosphate)
- 99mTc-HDP (hydroxymethylene diphosphate)

36
Q

how much radiopharm to inject into a patient of less than 85kg for a bone scan

A

15mCi intravenously

37
Q

how long does it take for the radiotracer to localise in the bone for the bone scan and how much

A

3 hours post-injection; 50%

38
Q

advantages of 18F-Na as PET radiotracer for bone scan over Tc99m diphosphonate

A
  • increased spatial resolution
  • improved target to background ratio
  • increased sensitivity
39
Q

disadvantages of using 18F-Na as PET radiotracer for bone scan over Tc99m diphosphonate

A
  • higher radiation dose
  • higher cost
  • potentially higher false positive result due to increased uptake at sites of degenerative changes
40
Q

when is 18F-Na used

A

temporary shortage of Tc99m

41
Q

radioactivity for renal MAG3 for an adult

A

5mCi

42
Q

what does a lung scan see

A
  • air flow (ventilation - V)
  • blood flow (perfusion - Q)
  • commonly known as V/Q scan
43
Q

formula for calculating geometric mean of the lung

A

(ant counts x post counts of each side of the lung) ^ 1/2

44
Q

how long does it take for a bone scan from prep to end

A

2-3hours from radiotracer to reach bones, 45 mins scan time

total: about 4 hours

45
Q

summary of a renal 99mTc-MAG3 scan

A

dynamic scan > lasix injection > pre-void scan > 60 mins walk around > post void scan

46
Q

summary of a renal 99mTc-DMSA scan

A

injection of radiotracer > 2hours > void > scan anterior, posterior, RPO, LPO

47
Q

summary of a lung ventilation scan

A

inhale through mouth via mouthpiece (~5-10mins), cover blanket, wear mask > scan

Nuclear Med (3 decks)

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