Unit 2 Medical Physics

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Unit 2 Medical Physics

• Paul Kane
• School of Health Sciences
• UUJ

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Topics for this session

• Fibre Optics and Lasers in medicine
• Light in therapy
• Ultrasound in therapy
• Radioisotopes in therapy
• Choosing modalities

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Fibre Optics
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Fibre Optics Explained

• Glass fibres around 120 micrometres dia
• Can carry light up to 50km without need for
  repeaters or boosting
• Commonly known applications are in data and voice
  communications

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Why the light Stays in

• When light meets an interface between 2 materials
  it will be transmitted or reflected
• Fibre optics manipulate this phenomenon

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Refractive Index and TIR
Low to High
High to Low
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ZigZag NOT STRAIGHT!
Lower Refractive Index
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Medical Application
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Medical Application

• Fibre optic tube
• Light source
• Lens
• Can be used to explore natural body cavities
• OR small artificial ones

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Advantages

• Can examine a variety of structures without
  requiring surgery
• Minor apertures can expand role further
• Can carry out surgical procedures via specialised
  variants of endoscope

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Light in Therapy

• Fibre optics can convey special light such as
  LASERs
• Light Amplified by Stimulation of Emitted
  Radiation
• LASER useful as surgical tool

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Laser Applications

• Eye Surgery
• Hair Removal
• Procedures on skin
• General Surgery
• Neurosurgery
• Urology

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Other Light Applications

• SAD (Seasonal Affective Disorder)
• Skin Disorders
• Delayed Sleep Phase Syndrome

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Ultrasound in Therapy

• Useful with injuries to soft tissue and joints
• Can aid the bodies own repair mechanisms
• Relieve pain and increase mobility
• Sports medicine makes great use of it

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Specialised Technique

• Lithotripsy
• Derived from the greek for Breaking Stones
• Break down of areas of calcification in areas
  like kidneys and gall bladder

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Why use Ultrasound?

• Readily available
• Proven technology
• Painless
• No need for surgery
• Safe and relatively cheap
• Not always effective
• Some procedures may require repetition

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Radioisotopes in Therapy

• Nuclear medicine utilises unsealed radioactive
  sources often attaching to a pharmaceutical to
  encourage uptake by specific tissue
• Therapeutic applications also use sealed sources

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Example Applications

• I131 thyroid cancer or thyrotoxicosis
• Ir192 breast cancer
• Cs137 endometrial tumours
• Co60 teletherapy units

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Afterloading

• Catheters introduced to treatment area
• Therapist controls insertion of sources from
  behind shielding

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Teletherapy

• Useful for a wide variety of radiotherapy
  applications

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Attributes of Therapeutic Isotopes

• In a form which can be manipulated
• Tend to be beta emitters
• Co60 is a gamma emitter

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Problems

• Radiation protection issues
• Dosimetry
• Finite life span of isotopes

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Which Modality?

• What is available
• What does the clinician recommend
• What can the patient tolerate
• Is there a safer/cheaper alternative?
• Can potential risks be justified?

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QUESTIONS?