IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

Part 16.4: Optimization of protection in fluoroscopy Practical exercise

IAEA International Atomic Energy Agency

Overview / Contents

• To become familiar with quality control tests in fluoroscopy • To measure the low contrast resolution and noise according to the suggested procedures • Interpretation of results

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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology Part 16.4: Optimization of protection in fluoroscopy

Low contrast resolution and noise

IAEA International Atomic Energy Agency

Low contrast resolution and noise

Purpose : • to measure the low contrast resolution and the influence of noise on low contrast detectability Equipment : • • image quality phantom (Leeds phantom) 2 mm Cu filter

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Low contrast resolution

• The

low contrast resolution

determines the size of detail that can be visibly reproduced when there is only a small difference in density relative to the surrounding area • Low contrast resolution is considerably noise. limited by • The perception threshold in relation to contrast and detail size can be determined, for example, by means of a contrast-detail curve.

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Leeds Fluoroscopy Phantom Noise and contrast loss

• Incorporates: 19 discs, each 11 mm diameter, of different x-ray contrasts.

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Leeds Fluoroscopy Phantom Noise and contrast loss

• Typical fluoroscopic image of the test object. View the small circles at center and count the number of visible circles

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Images from: http://www.leedstestobjects.com/modules/products/pr oduct_setup/file_library/SFS%20SET%20product%20 specifications.pdf

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Leeds Fluoroscopy Phantom Noise and contrast loss IAEA

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Noise and contrast loss

Interpretation of results

The threshold contrast is determined by the detail which can only just be detected. The threshold contrast of a modern system in average adjustment

should not be greater

than the following values:

Field size diameter

cm 30 - 35 22 - 25 15 – 18

Threshold Contrast

% 3.3 2.7 2.3

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Leeds Fluoroscopy Phantoms Overall Imaging Performance

• • Incorporates : 108 discs in 12 groups of different diameters; in each group there are 9 discs of different X-Ray contrasts.

Is used to assess the threshold-contrast detail-detectability.

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Leeds Fluoroscopy Phantoms Overall Imaging Performance

Typical fluoroscopic image of the test object.

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Leeds Fluoroscopy Phantoms Overall Imaging Performance Interpretation of results

Data are plotted as a function of detail diameter.

Threshold detection index is defined as H (A) = [C(A)  A] -1

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Where to Get More Information

Quality Control in Diagnostic Imaging, Gray JE, Winkler NT, Stears J, Frank ED. Available at no cost. http://www.diquad.com/QC%20Book.html

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