Download Lecture 1(2) -Sources in diagnostic Rad.– Fluoroscopy - gnssn

Radiation Sources in medicine
diagnostic Radiology
Fluoroscopy
IAEA
International Atomic Energy Agency
Day 7 – Lecture 1(2)
Objective
• To become familiar with of fluoroscopy equipment;
• To become familiar with specific radiation risks associated
with this type of equipment.
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Contents
• Description of fluoroscopy x-ray systems.
• Equipment malfunction affecting radiation protection.
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Fluoroscopic Equipment
•
•
•
Fluoroscopic equipment uses electronic image intensifiers to
provide real-time (dynamic) imaging;
Fluoroscopy is used for the
dynamic evaluation of
functional disorders and
guidance during routine
surgical procedures,
biopsies, etc.
Fluoroscopy is used during
interventional radiology
procedures.
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Fluoroscopic Equipment (cont)
General
purpose
fluoroscopic
system
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Fluoroscopic Equipment (cont)
Mobile fluoroscopic
system for routine
procedures during
surgery
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Fluoroscopic Equipment (cont)
All fluoroscopic units shall use an image intensifier, and:
• shall have an exposure control switch that energises
the x-ray tube only when continually pressed (i.e. a
dead man control);
• should allow the user to choose between continuous
or pulsed x-ray generation.
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Fluoroscopic Equipment (cont)
Direct fluoroscopy should no longer be used.
• “Direct” fluoroscopy does not use electronic image
amplification. The real-time image is viewed on a
fluorescent screen in a completely darkened room and
requires the fluoroscopist to dark adapt for approximately
20 minutes before the examination.
• Improper attention to these requirements can significantly
increase the radiation dose to patients and users.
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Fluoroscopic Equipment (cont)
All fluoroscopic units:
• shall display the instantaneous values of x-ray tube
voltage (kV peak), tube current (mA) and accumulated
fluoroscopic exposure time at the control or to the user.
• should be provided with a Dose-Area Product metre or a
measuring system to indicate patient exposure.
• The dose rate at the image intensifier input phosphor shall
not exceed the relevant IEC recommended values.
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Fluoroscopic Equipment (cont)
•
Manual collimation of the fluoroscopic x-ray beam should be
possible in addition to automatic collimation and adjusted to
(but never greater than) the effective area of the image
intensifier.
•
If the fluoroscopic unit is capable of high dose-rate operation a
separate visual and / or audible warning shall be provided to
the operator.
•
Fluoroscopic systems should incorporate a “last image hold”
mode where the last few frames of the fluoroscopic image are
displayed as a static image when the fluoroscopic exposure
ceases.
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Malfunctions affecting radiation protection
The types of malfunctions that should be considered are:
• generator and x-ray tube deficiencies listed in
previous lectures
• imaging system problems listed in previous lectures,
especially a reduction in image intensifier conversion
factor, low efficiency optics, poor resolution and contrast
of the image intensifier TV chain;
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Malfunctions affecting radiation protection (cont)
• inappropriate filtration of the useful x-ray beam;
• misalignment of the x-ray beam and image intensifier;
• excessive dose rate (above IEC recommendations) at the
image intensifier input phosphor;
• inadequate or improperly adjusted shielding devices;
• fluoroscopic exposure timer inaccurate or not functioning;
• incorrectly calibrated patient dose measuring system.
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