Therapy Machines Flashcards

1
Q

Characteristics of a Superficial Unit:

A
  1. 50-150 kVp
  2. 8 mA
  3. SSD = 20cm
  4. 2000 rad/min Max
  5. dmax = surface
  6. spec’d out by Al (not kVp) - also called “aluminum beam”
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2
Q

Characteristics of an Orthovoltage Unit:

A
  1. 150-500 kVp
  2. 10-20 mA
  3. SSD = 50cm
  4. 100 rad/min
  5. dmax = surface
  6. spec’d out by Cu (not kVp) - also called “copper beam”
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3
Q

What is the range of a Superficial Unit?

A

8cm in tissue

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4
Q

What is the HVL of a Superficial Unit?

A

8mm Al

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5
Q

What is the d90 of an Orthovoltage Unit?

A

d90 = 2cm

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6
Q

What is the HVL of an Orthovoltage Unit?

A

1-4mm Cu

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7
Q

What is needed to calculate MU/time for Superficial and Orthovoltage units?

A
  1. Filter type
  2. BSF
  3. Output in Air
  4. Air gap (if present)
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8
Q

For Superficial and Orthovoltage units, what will a change in filter affect?

A

HVL and Dose Rate

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9
Q

For Superficial and Orthovoltage units, an increase in HVL will result in what?

A

increasing the PDD (beam hardening)

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10
Q

How does filtering shift a beam for Superficial and Orthovoltage units?

A

Filtering shifts the avg E to the right (max E does not change with filtration)

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11
Q

How does Co-60 decay?

A

beta- with release of 2 gamma rays

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12
Q

What initial source E is a Co-60 unit loaded with?

A

10,000 Ci

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13
Q

What is the Dose Rate of a Co-60 Unit?

A

200 cGy/min at 80cm

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14
Q

What is the dmax of a Co-60 Unit?

A

0.5cm

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15
Q

What is the source size of a Co-60 Unit, and will this create small or large penumbra?

A

ss = 1.5 - 2cm (with circle end facing pt); large penumbra

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16
Q

What are some advantages of Co-60 Units when compared to Cs-137 and Ra-226?

A
  1. Higher specific Activity
  2. Increased Output/Ci
  3. Higher E - deeper penetration
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17
Q

What are the leakage rates of Co-60?

A

OFF: 2mR/hr Avg; 10mR/hr Max
ON: 0.1% of dose in air at 100cm (same as LINAC)

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18
Q

Medical Cyclotrons accelerate ____?

A

charged particles (not electrons)

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19
Q

What energy is a Low E Cyclotrons, and what elements can they produce?

A

<18 MeV; F-18, O-15, N-13, C-11

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20
Q

What energy is a Medium E Cyclotrons, and what elements can they produce?

A

18 MeV to 40 MeV; I-123, TI-201, Pd-103

21
Q

What energy is a High E Cyclotrons, and what elements can they produce?

A

> 40 MeV; Cu-67

22
Q

What imaging agents are used for myocardial perfusion?

A

TI-201 and N-13

23
Q

What imaging agents are used for myocardial metabolism?

24
Q

What imaging agents are used for soft tissue tumor imaging?

25
What imaging agents are used for regional glucose metabolism (besides kidneys and brain)?
F-18
26
What imaging agents are used for blood flow (for brain)?
C-11
27
What imaging agents are used for oxygen metabolism?
O-15
28
General operation flow of LINAC:
1. Klystron/Magnetron generate MW energy; 2. Waveguide carries MW from Klystron to Accelerator Tube (guide); 3. Electron gun injects e' into Accelerator tube; 4. MW accelerate e' close to the speed of light; 5. Bending Magnet directs e' beam to tx head; 6. e' beam interacts with target (for x-ray) or scattering foil (for e') to generate tx beam
29
Flow of tx head for Photon production:
1. e' beam hits tungsten (or gold) target; 2. Primary collimator; 3. Flattening Filter; 4. Ion chamber; 5. Secondary collimator (jaws); 6. Slot for hard wedge, blocks, compensators
30
Flow of tx head for e' production:
1. e' beam passes through primary collimator; 2. Scattering Foil; 3. Ion Chamber; 4. Secondary collimator; 5. Accessory Mount; 6. Electron Applicator (cone)
31
Characteristics of a Modulator:
1. Pulse forming - pulse and repetition 2. Thyratron switch 3. Pulsed DC provided to e' gun 4. Pulsed DC provided to MW generator
32
Characteristics of a Klystron:
1. Power Amplifier (low level MW to high level MW) - requires input power 2. High E 3. Stable
33
Characteristics of a Magnetron:
1. High power oscillator 2. Low E (<12 MeV) 3. Circular cavity 4. Unstable
34
Material of a Accelerator Guide, why:
Copper cavities: heat and electric conductivity
35
Characteristics of a Traveling Wave (accelerator guide):
1. Long guide 2. 75 keV 3. Dummy load required
36
Characteristics of a Standing Wave (accelerator guide):
1. Short guide 2. 150 keV 3. NO dummy load required
37
Characteristics of a circulator (isolator):
1. prevents damage from reflected MW power
38
Characteristics of an Electron Gun:
1. Injects e' into the Accelerator Guide 2. Thorium impregnated Tungsten filament 3. Copper Anode 4. Control grid
39
Characteristics of an Accelerator Guide:
1. Evacuated (vacuum to keep out contaminants) | * *note: the rf wave guide has freon or SF6, NOT the accelerator guide**
40
Characteristics of a Bending Magnet
1. Bend e' to 90 or 270 degrees | 2. maintain small focal point
41
How is output affected by Asymmetrical jaws:
1. Sc is about the same 2. Sp similar to block 3. Changes to Off axis ratio 4. Normalization
42
Effects on dose profile when 1/2 beam blocking:
Energy at gradient is produced by Compton scattering - 2cm from CAX to 100% isodose line to 50% isodose line
43
MLC intra-leaf transmission
1-2%
44
MLC inter-leaf transmission
3-4%
45
MLC Acceptance Testing:
1. Actual Leaf Position 2. Time Reach Position 3. Radiation (intraleaf) Leakage 4. Interleaf Leakage 5. Beam Contamination 6. Repeated at several gantry angles
46
MLC Characteristics:
1. not as accurate as Cerroban 2. More efficient than blocks 3. Tongue and groove effect
47
Jaw Transmission
<1%
48
Cerroban Transmission
3-5%