Radiation Kilo Curie

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Hazards of X-RaysJohn SaundersonRadiation
Protection Adviser .
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Wilhelm Roentgen

• Discovered X-rays on 8th November 1895 .

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Colles fracture 1896 .
Frau Roentgens hand, 1895
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Dr Rome Wagner and assistant
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First radiograph of the human brain 1896
In reality a pan of cat intestines photographed
by H.A. Falk (1896) .
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First Reports of Injury

• Late 1896
• Elihu Thomson - burn from deliberate exposure of
  finger

Edisons assistant - hair fell out scalp became
inflamed ulcerated .
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Mihran Kassabian (1870-1910)
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Two Types of Effect

• Deterministic effects (threshold effects)
• Stochastic effect (chance effects) .

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Deterministic Effects

• Caused by significant cell necrosis
• Not seen below a threshold dose
• Above the threshold, the bigger the dose, the
  worse the effect .

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Radiation-Induced Skin Injuries, from FDA, Sept
1994, Avoidance of serious x-ray induced skin
injuries to patients during fluoroscopically-guide
d procedures
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Dose Units

• Absorbed dose - Gray (Gy)
• Dose equivalence - Sieverts (Sv)
• (for X-rays 1 Gy 1 Sv)
• Effective dose - average dose over whole body,
  weighted for organ radiosensitivity (Sv) .

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Tissue Weighting Factors
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Stochastic Effects

• Caused by cell mutation leading to cancer or
  hereditary disease
• Current theory says, no threshold
• The bigger the dose, the more likely effect.

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Data Sources for Risk Estimates

• North American patients - breast, thyroid, skin
• German patients with Ra-224 - bone
• Euro. Patients with Thorotrast - liver
• Oxford study - in utero induced cancer
• Atomic bomb survivors - leukaemia, lung, colon,
  stomach, remainder .

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ICRP risk factors
5.0 x 10-5 per mGy ? 1 in 20,000 chance .
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Example of Radiation Injury in Cardiology

• 40 year old male
• coronary angiography
• coronary angioplasty
• second angiography procedure due to complications
• coronary artery by-pass graft
• all on 29 March 1990 .

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Fig. A 6-8 weeks after multiple coronary
angiography and angioplasty procedures
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Fig. B 16 to 21 weeks after procedure, with small
ulcerated area present
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Fig. C 18-21 months after procedure, evidencing
tissue necrosis
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Fig. D Close up of lession in Fig. C
From injury, dose probably in excess of 20 Gy .
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Fig. E Appearance after skin grafting procedure .
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Doses in CardiologyTaken from Real-time
quantification and display of skin radiation
during coronary angiography and intervention,
den Boer A, et al., Oct 2001

• 332 patients
• 25 - 99 Gy.cm2 dose-area product
• 4 - 18 mGy effective dose
• 15000 - 11100 risk of inducing fatal cancer .

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Dose Area Product

• Stochastic risks approx. proportional to DAP
• Skin dose is DAP / area irradiated
• 1 Gy.cm2 ? 3 mGy skin dose
• 1 Gy.cm2 ? 0.2 mSv effective dose .

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20/11/96
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Pregnancy - Radiation Risks
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ICRP Basic Principles

• Justification
• Optimisation
• Limitations .

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Fin
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Equipment PerformanceImage Quality Patient
SafetyJohn SaundersonRadiation Protection
Adviser
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Entrance Dose Rates for Standard Phantom
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Time to Reach 2 Gy for Standard Phantom
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Skin dose rate (mGy/min)
Remedial level 50 mGy/min for largest
field Suspension level 100 mGy/min
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Image Quality Test Objects
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Spatial Resolution
(Number of bar sets seen)
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Threshold Contrast
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Tube Voltage (kV)

• Higher kV lower patient dose
• e.g. changing from 100 to 110 kV leads to 12
  reduction in skin dose
• Higher kV less contrast
• e.g. changing from 100 to 110 kV reduces
  spine/soft tissue contrast from 1.48 to 1.34 (9
  drop).

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Filtration

• More filtration lower patient dose
• e.g. ? 0.1 mm Cu ? ? 33 skin dose
• More filtration less contrast
• e.g. ? 0.1 mm Cu ? ? spine/soft tissue contrast
  at 80 kV from 2.76 to 2.46 (11 drop).

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Tube to Patient Distance

• Greater FSD lower patient dose
• e.g. ? from 50 to 70 cm ? ? 49 skin dose
• Greater FSD less magnification
• (so fewer distortions).

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