????? ?????? ???????? Clinical Radiation Generator

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????? ?????? ????????Clinical Radiation Generator

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???????? ????????? Radiotherapy
??????? ??????? ?????? ?? ?????? ??????? Using
the ionizing Radiation to treat cancer
?????? ?????? (?? ???) External Beam Therapy
(EBT)
?????? ?????? (?? ???) Brachytherapy
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Radiotherapy

• One of the main treatment modalities for cancer
  (often in combination with chemotherapy and
  surgery)
• It is generally assumed that 50 to 60 of cancer
  patients will benefit from radiotherapy
• Minor role in other diseases

Siemens Oncology
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External Beam Radiotherapy
Beam 2
Beam 3
Beam 1
tumor
patient
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External Beam Radiotherapy

• More than 90 of all radiotherapy patients are
  treated using EBT
• Most of these are treated using X-rays ranging
  from 20keV to 20MeV in peak-energy
• Other EBT treatment options include telecurie
  units (60-Co and 137-Cs), electrons from linear
  accelerators and accelerators for heavy charged
  particles such as protons

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Cancer incidence (WHO)
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Major indications for radiotherapy

• Head and neck cancers
• Gynaecological cancers (eg. Cervix)
• Prostate cancer
• Other pelvic malignancies (rectum, bladder)
• Adjuvant breast treatment
• Brain cancers
• Palliation

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Approaches

• Palliative radiotherapy to reduce pain and
  address acute symptoms - eg bone metastasis,
  spinal cord compression, ...
• Radical radiotherapy as primary modality for cure
  - eg head and neck
• Adjuvant treatment in conjunction with surgery -
  eg breast cancer

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Aim
Patient
Critical organs

• To kill ALL viable cancer cells
• To deliver as much dose as possible to the target
  while minimising the dose to surrounding healthy
  tissues

target
Beam directions
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Prognostic Factors

• Cancer type and stage
• Patient performance
• Radiation dose
• ...

Good prognosis
survival
Bad prognosis
time
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Prognostic Factors

• Cancer type and stage
• Patient performance
• Radiation dose
• ...

Accurate dose delivery matters!
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Dose should be accurate

• To target
• 5 too low - may result in clinically detectable
  reduction in tumour control (eg. Head and neck
  cancer 15)
• To normal tissues
• 5 too high - significant increase in normal
  tissue complication probability morbidity
  unacceptable side effects

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External beam radiotherapy (EBT) treatment
approaches

• Superficial X-rays
• Orthovoltage X-rays
• Telecurie units
• Megavoltage X-rays
• Electrons
• Heavy charged particles
• Others

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External beam radiotherapy (EBT) treatment
approaches

• Superficial X-rays
• Orthovoltage X-rays
• Telecurie units
• Megavoltage X-rays
• Electrons
• Heavy charged particles
• Others

• 40 to 120kVp
• 150 to 400kVp
• 137-Cs and 60-Co
• Linear accelerators
• Linear accelerators
• Protons from cyclotron, C, Ar, ...
• Neutrons, pions

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Superficial radiotherapy

• 50 to 120kVp - similar to diagnostic X-ray
  qualities
• Low penetration
• Limited to skin lesions treated with single beam
• Typically small field sizes
• Applicators required to collimate beam on
  patients skin
• Short distance between X-ray focus and skin

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Superficial radiotherapy
Philips RT 100
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Superficial radiotherapy issues

• Due to short FSD high output and large influence
  of inverse square law
• Calibration difficult (strong dose gradient,
  electron contamination)
• Dose determined by a timer - on/off effects must
  be considered
• Photon beams may be contaminated with electrons
  from the applicator

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Orthovoltage radiotherapy

• 150 - 400kVp
• Penetration sufficient for palliative treatment
  of bone lesions relatively close to the surface
  (ribs, spinal cord)
• Largely replaced by other treatment modalities

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Kilovoltage Equipment (150 - 400 kVp)

• Depth dose dramatically affected by the FSD

FSD 6cm, HVL 6.8mm Cu
FSD 30cm, HVL 4.4mm Cu
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Orthovoltage patient set-up

• Like for superficial irradiation units the beam
  is set-up with cones directly on the patients
  skin

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Megavoltage radiotherapy

• 60-Cobalt (energy 1.25MeV)
• Linear accelerators (4 to 25MVp)
• Skin sparing in photon beams
• Typical focus to skin distance 80 to 100cm
• Isocentrically mounted

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