11. Modality Exploration and Radiation Therapy Flashcards

1
Q
A radiologic examination that involves 
the use of strong magnets, 
radiofrequency waves, and computer to 
create an image of the internal 
structures of the body
A

Magnetic Resonance Imaging

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2
Q

Magnetic Resonance Imaging discovered simultaneously in ____ by :

A

1947
o Felix Bloch
o Edward Mills Purcell

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3
Q
In \_\_\_\_, provided an impetus to the 
development of actual clinical imaging 
using strong magnetic fields by 
suggesting that radio wave signal 
relaxation times of different tissues 
might be indicative of tumour 
malignancy
A

Raymond Damadian (1971)

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4
Q

Provided the first 2D MR image of

chemical sample in ____

A

Paul Lauterbur (1973)

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5
Q

MRI Components

A

o Primary magnets
o Gradient magnets
o Radiofrequency (RF) Coils
o Computer system

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6
Q

MRI Image Formation

A

o Large magnet produces a strong
magnetic field around the body
o Nuclei in the body precess at the larmor
frequency
o Gradient coils vary the magnetic field
across the body
o A slice of the body is specified by the
magnetic field variation along the Z-axis

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7
Q

The slow movement of the axis of a
spinning body around another axis due
to a torque acting to change the
direction of the first axis

A

Precession

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8
Q

refers to the rate of precession of
the magnetic moment of the proton
around the external magnetic field

A

Larmor or precessional frequency in

MRI

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9
Q

MRI Image Formation (1)

A
o Gradient coils also vary magnetic 
field along the x and y directions to 
select a tiny volume
o The magnetic field in that volume is 
set so that only the nuclei in that 
volume are at resonant Larmor 
frequency
o The procedure that follows will 
identify the tissue type in that 
volume
o This small volume will form one 
pixel of the final image
o During the scan, many small 
volumes will be scanned
o Nuclei in the volume precess at the 
specified Larmor frequency
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10
Q

MRI Image Formation (2)

A
o A pulse of radio photons is 
transmitted into the body 
o Nuclei absorb energy and resonate, 
they flip into higher energy state
o After a period of time the nuclei 
relax: flip back to their normal 
energy state
o When they relax, they emit a radio 
photon
o The emitted photons form the 
signal received by the RF coils
o The mean time that elapses 
between switching off the 
transmitted RF pulses and receiving 
a signal from relaxing nuclei is the 
relaxation time
o The tissue type at the specified 
volume is identified from the 
relaxation time
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11
Q
is a mathematical 
technique that allows an MR signal to 
be decomposed into a sum of sine 
waves of different frequencies, phases, 
and amplitudes
A

Fourier Transform

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12
Q
is a specialized are of 
radiology that uses very small amounts 
of radioactive amounts, or 
radiopharmaceuticals, to examine 
organ function and structure
A

Nuclear Medicine

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13
Q

Three-stage process of radionuclide imaging

A
o Introduction of suitable radionuclide 
into the patient
o Concentration of radionuclide in the 
specific organ
o Scanning of organ using appropriate 
scanner
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14
Q

Common ways in How to Produce Artificial

Radionuclide

A

o Irradiating materials in a nuclear
reactor
o Using technetium generator
o Using a medical cyclotron

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15
Q

Gamma Camera first developed by _____ in

___

A

Hal Oscar Anger,

1958

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16
Q
Specialized type of scintillation counter 
where the position as well as the count 
of the scintillations within a thin Nal 
Crystal (or multiple crystals) are 
obtained using a number of 
photomultipliers
A

Gamma Camera

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17
Q
is a diagnostic medical 
procedure that uses sound waves to 
produce images on a screen which 
allows medical providers to view 
internal structures of the body
A

Ultrasonography

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18
Q

Approximate speed of sound in Air

A

340 m/s

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19
Q

Approximate speed of sound in Lung

A

650 m/s

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20
Q

Approximate speed of sound in Fat

A

1460 m/s

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21
Q

Approximate speed of sound in Pure water

A

1500 m/s

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22
Q

Approximate speed of sound in Salt water

A

1530 m/s

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23
Q

Approximate speed of sound in Kidney

A

1560 m/s

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24
Q

Approximate speed of sound in Blood

A

1570 m/s

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25
Approximate speed of sound in Muscle
1580 m/s
26
Approximate speed of sound in Bone
3000 m/s
27
is the | ability to bounce an echo
Echogenicity or echogeneity
28
Echogenicity or echogeneity
o Hypoechoic o Hyperechoic o Anechoic
29
``` A device that produces sound waves that bounce off body tissues and make echoes. It also receives the echoes and sends them to a computer that uses them to create a picture called a _____ ```
Transducer, | sonogram
30
is the ability of certain materials to generate an electric charge in response to applied mechanical stress
Piezoelectric Effect
31
The word Piezoelectric is derived from the Greek _____, which means to squeeze or press, and ___, which is Greek for push.
piezein, | piezo
32
Piezoelectric Effect | Strengths
``` o Inexpensive o Quick o Mobile o Non-invasive o Can depict free fluid and aneurysms, e.g. in acute aneurysms o Can differentiate between solid and fluid structures o Can depict flow and motion o Good for shallow structures ```
33
Piezoelectric Effect | Weaknesses
``` o Operator dependent o Images may be hard to interpret o Suffers from image artifacts o May be prone to giving “false positives” o Not good for deep structures o Cannot penetrate through bone or air ```
34
Began in 1930s with angiography
Interventional radiology
35
pionerred transbrachial selective coronary angiography
Mason Jones (Early 1960s)
36
introduced coronary | angiography
Melvin Judkins
37
introduced visceral | angiography
Charles Dotter
38
Refers to the opacification of vessels | through injection of contrast media
Angiography
39
Imaging Procedures
- Angiography - Aortography - Arteriography - Cardiac catheterization - Myelography - Venography
40
Interventional Procedures
- Stent Placement - Embolization - Intravascular stent - Thrombolysis - Balloon angioplasty - Atherectomy - Electrophysiology
41
Embolization
1. Narrow neck aneurysms 2. Aneurysm catheterization 3. Coil development 4. Microcatheter removal
42
described a method of arterial access in which catheter was used
Sven Ivar Seldinger (in 1953)
43
18 gauge hollow | needle with stylet
Seldinger needle
44
Allows safe introduction of the catheter | into the vessel
Guidewires
45
Fabricated of stainless steel and contain an inner core that is tapered at the end to a soft flexible tip
Guidewires
46
are 145 cm | long
Conventional guidewires
47
Catheters - categorized in French (Fr) sizes; __ Fr | equal to __ mm in diameter
3, | 1
48
used for femoral | approach to the brachiocephalic vessels
H1 or headhunter tip- (designed by | Vincent Hinck)
49
highly curved | designed for cerebral angiography
Simmons catheter
50
has angled tip for | celiac, renal, and mesenteric arteries
C2 or Cobra Catheter
51
have side holes for ejecting | contrast media into a compact bolus
Pigtail
52
Procedure room should not be less than 20 feet along any wall and not less than 500 ft^2
Interventional Radiology Suite
53
Control room must be large, perhaps | 100 ft^2
Interventional Radiology Suite
54
2 or 3 radiographers, interventional | radiologist, radiology nurse
Interventional Radiology Suite
55
More massive, flexible and expensive than conventional; radiographic and fluoroscopic imaging
X-ray Apparatus
56
Small target angle
X-ray Tube
57
Large diameter massive anode disc
X-ray Tube
58
designed for magnification | and serial radiography
Cathodes (X-ray Tube)
59
X-ray Tube Small focal spot size
not greater than | 0.3 mm
60
X-ray Tube SID
100 cm
61
X-ray Tube OID
40 cm
62
The use of high-energy radiation from xrays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors
Radiation therapy
63
Teletherapy other name
External beam radiation therapy (EBRT)
64
EBRT
External beam radiation therapy
65
Radiation delivered from a distant source, from outside the body and directed at the patient’s cancer site
Teletherapy
66
``` involves placing radiation sources as close as possible to the tumor site. Sometimes, they may be inserted directly into the tumor ```
Brachytherapy
67
Sometimes, they may be inserted | directly into the tumor
Brachytherapy
68
The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors
Radiation therapy
69
Energies up to 150 Kv with beam filtration of 1-8 mm al at an FSD (focal skin distance) of 10-30 cm
Superficial units
70
with energies of 150-500 kV with 0.5-3 copper filtration at a 50 cm FSD
Orthovoltage unit or “deep therapy”
71
Accelerate electrons in a straight | path
Linear Accelerator (LINAC)
72
Energies up to 5 MeV
Linear Accelerator (LINAC)
73
LINAC
Linear Accelerator
74
Linear Accelerator (LINAC) - Divided into two large structures
o Floor-mounted stand | o Motor-driven gantry
75
``` An evacuated cylindrical structure, consisting of hollow, indirectly heated, oxide-coated cathode surrounded by a copper anode containing equidistant cavities that communicate with the space surrounding the cathode ```
Magnetron
76
Anode and cathode are supplied by pulse direct current supply from the modulator
Magnetron
77
AFC
Automatic Frequency Control
78
Maintains the frequency with | an accuracy of +- kHz
AFC- Automatic Frequency Control
79
AFC- Automatic Frequency Control
Magnetron
80
Simple hollow tubes that carry the RF waves from the magnetron to the accelerator section waveguides
Waveguides
81
are sealed at both ends by ceramic discs that are transparent to microwave radiation
Waveguides
82
Waveguides are filled with ______ to | improve its power-handling capabilities
sulphur hexafluoride
83
Situated between the magnetron and | the waveguide
RF Circulator
84
Act as a one-way valve permitting the RF radiation to pass into the waveguide, but preventing any from passing back into the magnetron
RF Circulator
85
Situated in the gantry of LINAC
Accelerating Waveguide and Accelerator
86
Uses RF to accelerate electrons to | very high velocities
Accelerating Waveguide and Accelerator
87
Electron gun injects electron into the guide impulses under the control of modulator, in synchronization with the RF waves
Accelerating Waveguide and Accelerator
88
at the entrance and exit of the waveguide ensure that the electron beam is centered to the center of the guide and target
Focusing coils
89
Deflects the electron beam through a | 270 degree angle
Bending Magnet and Treatment Head
90
is an evacuated structure situated externally to the accelerator structure
Bending magnet
91
Attached to an external opening on the treatment head
Electron applicator
92
Designed to produce a | “flat” electron beam
Scattering foil