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CSB069 - RT Treatment 4 > Week 12 - Functioning and Molecular Imaging > Flashcards

Week 12 - Functioning and Molecular Imaging Flashcards

1
Q

application for radiotherapy

A
  • staging and decision making
  • treatment plan optimisation
  • measuring radiotherapy response
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2
Q

problems with CT based anatomical imaging (staging)

A
  • CT has limited spatial resolution and sensitivity
  • often can’t resolve metastatic disease or nodal involvement
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3
Q

problems with CT based anatomical imaging (treatment planning)

A
  • CTV delineation and assumption of uniform radiosensitivity
  • organ at risk contouring. Function usually not considered and assumed to be uniform
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4
Q

problems with CT based anatomical imaging (treatment response)

A
  • where was the dose actually delivered
  • response of disease and normal tissues both during and post-treatment
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5
Q

what is FI in RO

A

mapping in three dimensions the distribution of a tumour, tissue or functional feature and to provide information about the clinical response of tumours or healthy tissues to ionising radiation

provide information about the functional and metabolic characteristics of tissues and tumors in a patient’s body. provides insights into how tissues are functioning, metabolizing, and responding to various processes, such as disease or treatment

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6
Q

MRI T1 images for

A

gross anatomy

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7
Q

MRI T2 images for

A

biological pathology

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8
Q

nuclear medicine

A

measure the distribution of a radionuclide in the body

  1. inject the patient with the gamma emitting radiotracer
  2. detect where the radiotracer goes in the body
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9
Q

SPECT

A

allows a 3D distribution of radionuclide to be reconstructed from multiple 2D projections

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10
Q

Explain how PET/CT works

A

Positron emitting radionuclide injected into patient, positrons annihilate with electrons creating 2 photons which are detected via coincidence detection allowing a tomographic image to be created

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11
Q

Discuss the rationale behind PET/CT

A

PET & CT occurs on the same day, in the same position, CT provides more anatomical definition allowing for a more accurate location of PET uptake to be determined.

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12
Q

Discuss how MRI imaging/ functional imaging is used in lung

A

Fast MRI imaging sequences (high spatial and temporal resolution) & hyperpolarised He-3 to determine lung function.

Perfusion - absorption of gas into the blood (Krypton-81m gas)

Ventilation - measures gas intake into the lungs

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13
Q

Define true coincidence

A
  • Coincidences simultaneously detected on both detectors resulting from the same annihilation of a positron and corresponding to the 511 keV energy photons not having undergone any scatter
  • the true signal that one wants to detect
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14
Q

Define random coincidence

A
  • Photons emitted by different annihilations but detected in the same window
  • background noise
  • reduced by lowering coincidence time window
  • alpha filters or septa
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15
Q

What is the 1/2 life of 18F?

A

110 minutes

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16
Q

What is the 1/2 life of 11C?

A

20 minutes

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17
Q

What is the application for 18F?

A

glucose metabolism

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18
Q

What is the application for 11C?

A

tumour protein synthesis

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19
Q

Why should PET/CT be used in lung cancer?

A

PET can increase accuracy of tumour delineation and detect unsuspected nodal and metastatic disease

20
Q

How does diffusion weighted MRI help in functional imaging?

A

Provides contrast which correlates with differences in water-tissue mobility which can be restricted in tumours with high cellularity - treatment can cause a change in this

provides information about the movement of water molecules within tissues. Malignant tumors often have higher cell density (high cellularity) and restricted water diffusion.

21
Q

List 5 applications of functional MRI in lung RT

A
  1. Fast imaging sequences (high spatial and temporal resolution)
  2. Tumour mobility (dynamic imaging)
  3. Effect of motion on dosimetry using probability density function
  4. Hyperpolarised He-3 to determine lung function
  5. Measure response to radiation
22
Q

List 2 applications of functional MRI in prostate RT

A
  1. Superior imaging modality to determine disease extent and contouring
  2. Blood oxygen level dependant sequences for measuring hypoxia
23
Q

List 5 functional magnetic resonance imaging

A
  1. Spectroscopy
  2. Dynamic contrast enhanced
  3. Diffusion weighted imaging
  4. Fast pulse sequences
  5. Hyperpolarising
24
Q

define functional imaging

A

Functional imaging refers to mapping in three dimensions the distribution of a tumour, tissue or functional feature, and to provide information about the clinical responses of tumours or normal tissues to ionising radiation.

25
Q

Define SUV

A
  • standard uptake value
  • assesses the level of radioactivity within a region of interest in the body
26
Q

What is the role of dynamic contrast enhanced MRI (DCE-MRI) in fMRI?

A
  • performed following the injection of a contrast such as Gadolinium
  • image sequence used to assess uptake of contrast (higher uptake of contrast in tumours due to leaky blood vessels)
  • used to measure extravascular extra-cellular space (T1) or tissue perfusion and blood volume (T2*)
27
Q

What is the role of magnetic resonance spectroscopic imaging (MRSI) in fMRI?

A
  • image sequence used to assess the concentration of isotopes in tissue (changes in concentration in tumour due to changes in metabolism)
  • used to detect tumours
28
Q

What is the role of diffusion weighted MRI (DW-MRI) in fMRI?

A
  • image contrast that correlates with differences in tissue-water mobility
  • image sequence used to assess the ease with which water molecules move in tissue (reduced motion of water molecules in tumours due to higher cellularity)
  • used to measure tumour response (i.e., swelling, lysis, and/or necrosis) using apparent diffusion coefficient (ADC) maps
29
Q

List 5 applications of functional MRI in lung RT

A
  1. Fast imaging sequences (high spatial and temporal resolution)
  2. Tumour mobility (dynamic imaging)
  3. Effect of motion on dosimetry using probability density function
  4. Hyperpolarised He-3 to determine lung function
  5. Measure response to radiation
30
Q

List 2 applications of functional MRI in prostate RT

A
  1. Superior imaging modality to determine disease extent and contouring
  2. Blood oxygen level dependant sequences for measuring hypoxia
31
Q

List 5 functional magnetic resonance imaging

A
  1. Spectroscopy
  2. Dynamic contrast enhanced
  3. Diffusion weighted imaging
  4. Fast pulse sequences
  5. Hyperpolarising
32
Q

PET

A
  • 18F decays by emitting positrons
  • positron annihilate with electrons at the end of their tracks (1-2mm) creating two annihilation photons
  • conservation of energy and momentum
    • photon energy equals 511keV
    • 180 degrees to each other
33
Q

advantages of PET over normal nuclear medicine techniques

A
  • spatial resolution
  • quantification
34
Q

What is the 1/2 life of 15O

A

2 minutes

35
Q

application of 15O

A

cerebral blood flow

36
Q

What is the 1/2 life of 13N

A

10 minutes

37
Q

application of 13N

A

myocardial flood flow

38
Q

hyperpolarisation

A
  • nuclei are driven to a very high degree of polarisation increasing the MR signal temporarily
39
Q

application of fMRI in RT - brain

A
  • used frequently to assist in GTV and CTV delineation in planning
  • fOAR for conformal avoidance
  • measurement of response to therapy
    • diffusion maps
40
Q

application of fMRI in RT - lung

A
  • fast image sequences can give high spatial and temporal resolution. up to 10 images per second
  • tumour mobility from dynamic imaging
  • effects of motion on dosimetry using probability density function
  • hyperpolarised He-3 to determine lung function
    • avoidance of functioning lung during planning
41
Q

application of fMRI in RT - prostate

A
  • MRI is superior imaging modality for the prostate
  • extent of disease and contouring
  • multiple combinations of MRI sequences
    • T2, DCE, DW and MRS all have a role in improving cancer detection and mapping
  • blood oxygen level dependent (BOLD) sequences for measuring hypoxia
42
Q

fMRI in brain

A
  • used frequently to assist in GTV and CTV delineation in planning
  • Measurement of response to therapy - diffusion maps
  • Can do correlation between diffusion coefficient pre-post treatment
43
Q

application of PET in NSCLC

A
  • Unsuspected nodal disease can be detected
  • Two types of imaging: ventilation and perfusion using Krypton gas
  • Can highlight blood flow
44
Q
A
45
Q

application of PET in hypoxia and glucose metabolism

A
  • hypoxia cells in tumours have an increased radio resistance
  • F18 and FMISO can evaluate glucose metabolism and correlation for tumour hypoxia
  • However, hypoxia is not the sole cause of increase in glucose metabolism observed in cancer cells *specific to tumour type
46
Q

application of PET in breast cancer

A
  • Patient treated for breast cancer with bone and supraclavicular lymph node metastases detected by PET/CT

CSB069 - RT Treatment 4 (7 decks)

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