• Auto c
alibraon can be used when the anatomy is in isocenter. For objects at this locaon, 2D-QA
knows all relevant distances that are needed for automac computaon of the geometrical
magnicaon and the calibraon factor. No further user input is required.
• Manual calibraon is applicable for any locaon in the X-ray beam. The calibraon factor for the
anatomy under invesgaon is computed with help of a calibraon object of known size posioned
nearby. The user marks the calibraon object and indicates its actual size.
Note that errors in the calibraon factor directly translate into proporonal errors in QCA/QVA distance
measurements. In the computaon of volumes in LVA/RVA, these errors even mulply by a factor of 2
to 3. Therefore it is important to adhere to the following guidelines for accurate calibraon.
Avoid foreshortened views on the calibraon object and the anatomy.
• This is important in distance calibraon and for all measurements in anatomical regions of interest.
Posion the calibraon object and the object under invesgaon accurately.
• If you intend to use auto calibraon, the object under invesgaon must be placed as close to the
isocenter as possible during image acquision (within at most 5 cm).
• If you intend to use manual calibraon (catheter, sphere, or distance), the calibraon object must
be placed as close as possible to the anatomy under invesgaon.
• Dierences in height between the anatomy and the isocenter (in auto calibraon), or between the
anatomy and the calibraon object (in manual calibraon) cause dierences in geometrical
magnicaon. This leads to addional errors in the calibraon factor of 1-1.5% for each cenmeter
of dierence in height.
Auto calibraon, or intermediate sized objects for manual Calibraon, is preferred.
• Preferably use auto calibraon when the anatomy under invesgaon is suciently close to the
isocenter (within at most 5 cm). Most images are usually acceptable for auto calibraon.
• In case auto calibraon is not applicable, catheter calibraon is usually considered as the most
convenient opon. However, when used in combinaon with modern small-diameter (4-6 French)
catheters, it is also the least accurate opon (see the following table). If possible, use distance
calibraon on a sizing catheter or sphere calibraon instead.
• In general, the accuracy of manual calibraon increases with the object size or distance used. Do
not use small calibraon objects for manual calibraon. If possible, choose a calibraon object of
intermediate size (a few cenmeters) for opmal accuracy.
Overview of Calibraon Factor Accuracy
Calibraon me
thod (specicaon
condion)
CF accuracy for properly posioned
objects
Addional errors in CF from inaccu-
rate posioning or views
Auto calibraon
Accurate
1
1-1.5% for each cenme
ter of dier-
ence in height between isocenter and
anatomy
Distance calibraon (over distance of a
few cm)
Accurate
1
1-1.5% for each cenme
ter of dier-
ence in height between object and
anatomy.
This method is sensive to foreshort-
ening in the image
Sphere calibraon (with metal ball of a
few cm diameter)
Accurate
1
1-1.5% for each cenme
ter of dier-
ence in height between sphere and
anatomy
Catheter c
alibraon
2
(catheter of 6
French diameter lled with contrast
agent)
Less accurate: approximately 7% error
in
troduced
3
1-1.5% for each cenmeter of dier-
ence in height between catheter and
anatomy
Note 1: Accurate means that the small de
viaon from this source does not adversely aect overall measurement accuracy.
Note 2: As veried for commonly used catheters. Due to the small diameter of modern catheters and diversity in their walls,
obtainable accuracies may vary with catheter brand and size.
Note 3: Errors from using unlled catheters or catheters below 6 French can be 20% or more.
2D Quant
ave Analysis (Opon) Calibraon Guidelines
Azurion Release 1.2 Ins
trucons for Use 159 Philips Healthcare 4522 203 52421
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