Radiation Protection for Assistant Practitioners in Mammography Lecture 3

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Radiation Protection for Assistant Practitioners
in MammographyLecture 3

• John Saunderson
• Radiation Protection Adviser
• (TPRH ext. 6690)

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IRMER Syllabus

• Production of X-rays
• Absorption and scatter
• Radiation hazards and dosimetry
• Special attention areas
• Radiation Protection
• Laws Guidelines
• Equipment .

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1.3 Special Attention Areas

• Pregnancy and potential pregnancy
• Infants and children
• Medical and biomedical research
• Health screening (covered elsewhere)
• High dose techniques .

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Deterministic Effects to Fetus
(Typical breast dose 2 mGy 0.002 Gy.)
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Pregnancy potential pregnancy

• 100s of mGy needed to cause fetal death or
  malformation
• But an increased risk of childhood cancer (3 per
  Sv) .

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Stochastic Effects to Fetus
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If Pelvic Area in Beam, or Nuclear Medicine

• No possibility of pregnancy - proceed
• Probably pregnant - radiologist decides
• delay X-ray until after delivery, or
• use non-X-ray technique (e.g. ultrasound), or
• go ahead with X-ray but keep dose low
• Possibly pregnant, low dose procedure - proceed
  if period is not overdue.
• High dose procedure (10s of mGy, e.g. pelvic CT)
• X-ray in first 10 days of menstrual cycle .

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Pregnancy and Mammography

• There is no requirement to enquire about
  pregnancy prior to mammography as there is no
  significant dose to the fetus
• NHBSP Dec 02

• For pregnant staff,
• a risk assessment must be performed,
• dose to fetus lt 1 mSv for rest of pregnancy.

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Infants and children

• Higher risk of inducing cancer than adults .

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Medical and biomedical research

• Need to take extra care, especially where healthy
  volunteers involved
• Must be approved by Local Research Ethics
  Committee
• Must set dose constraints or target levels of
  dose .

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Health screening (covered elsewhere)

• X-raying healthy individuals
• Must ensure overall benefit outweighs risk
• Therefore, QA etc. very important .

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High dose techniques

• CT
• Fluoroscopy
• etc. .

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2. Management and Radiation Protection of Patient
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2.1 Patient Selection

• Justification of the individual exposure
• Patient identification and consent
• Use of appropriate radiological information
• Alternative techniques
• Clinical evaluation of outcome
• Medico-legal issues .

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Justification of the individual exposure

• By law, all exposures must be justified
• For breast screening
• Women invited within NHSBSP invitation protocol
• Women not invited, but fit NHSBSP protocol
• For other, practitioner must decide (e.g.
  radiologist)
• A written record must be made of who authorised
  each X-ray.

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Patient identification and consent

• (covered elsewhere)
• By law, the Trust must have a patient ID
  procedure
• ID should be positive (Yes, dear wont do! .

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Use of appropriate radiological information

• (covered elsewhere) .

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Alternative techniques

• Always use lowest dose technique, that will
  achieve the clinical result .

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Clinical evaluation of outcome

• By law, all films must be reported .

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Medico-legal issues

• e.g. X-rays for insurance purposes
• Special procedures must be in place to ensure
  that exposures are justified .

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2.2 Radiation Protection

• General radiation protection
• Use of radiation protection devices
• patient
• personal
• Procedures for untoward incidents involving
  overexposure to ionising radiation .

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• Justification
• Optimisation
• Limitation

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(No Transcript)
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All doses should be kept

• As
• Low
• As
• Reasonably
• Achievable
• The ALARA Principle .

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Basic Principles

• Time
• Distance
• Shielding

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Distance

• Double distance 1/4 dose
• Triple distance 1/9th dose.

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Shielding
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Shielding
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Organising radiation safety

• Controlled Areas
• Local Rules
• Radiation Protection Supervisor
• Radiation Protection Adviser
• Radiographer
• Assistant Practitioner .

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Use of radiation protection devices

• patient
• personal

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Untoward Incidents

• Overexposure of patient
• Overexposure of staff
• ?.

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Incidents

• Any untoward occurrence which may result in
  excess radiation to staff or patients must be
  referred to the Radiation Protection Supervisor
  and the Radiation Protection Adviser, who will
  estimate the dose and liase with management, HSE,
  DoH, HMIP, etc. as appropriate
• Suspect equipment must be withdrawn from service
  and labelled according.

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Patient Doses Much Greater Than Intended

• x 20 - extremities, skull, chest, etc.
• x 10 - lumbar spine, abdomen, pelvis, mammography
  and other examinations not referred to elsewhere,
  
• x 3 - fluoroscopy, digital radiography, C.T

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Investigation

• establishing what happened
• identifying the failure
• deciding on remedial action to minimise the
  chance of a similar failure
• estimating the doses involved
• decide whether patient informed (usually yes).

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(End lecture 3 by now)
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3. Statutory Requirements and Advisory Aspects
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3.1 Statutory Requirements and Non-Statutory
Recommendations

• Regulations
• Local rules and procedures
• Individual responsibilities relating to medical
  exposures
• Responsibility for radiation safety
• Routine inspection and testing of equipment
• Notification of faults and Health Department
  hazard warnings
• Clinical Audit .

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4. Diagnostic Radiology
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4.1 General

• Fundamentals of radiological anatomy
• Fundamentals of radiological technique
• Production of X-rays
• Equipment selection and use
• Factors effecting radiation dose
• Dosimetry
• Quality assurance and quality control .

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4.3 Fundamentals of Image Acquisition, etc.

• Image quality v. radiation dose
• Conventional film processing
• Additional image formats, acquisitions, storage
  and display .

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f i n
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Trash next
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Attenuation, Scattering and Absorption

• 0.34 mm Al at 28 kV Mo/Mo
• For average breast
• 0.2 of x-ray energy reaches film
• 99.8 absorbed in breast