| Small errors in
measurements can lead to large errors in calculated
results. Measurement accuracy is dependent upon
the resolution of the image and following standard
measurement techniques. The transducer that
will provide the best resolution for the measurement
should be selected. Use the highest frequency
possible that will allow visualization of the structure
to be measured. The focal point should be located
at the structure to be measured. The display
should be maximized (magnified using zoom, depth,
width) so only the area of interest is visualized.
Timing measurements should be done under higher sweep
speeds. Consistent settings and probes should
be used for similar measurements between patients
and between studies of the same patients. Do
not change settings or change probes and expect that
the measurements will be equally accurate.
Measurements
of length or area of a cardiac structure should be
made on the inside edge or leading edge to leading
edge technique. When measuring slopes, use two
points as far apart as possible. Use the ECG
for locating mechanical end-diastolic and end-systolic
phases.
The doppler
angle may be off more than 20 degrees which will induce
an error greater than 5%. While the Doppler
in one plane may appear to be correct, in another
plane it can be off more than 20 degrees. Therefore, clinical interpretation is important. If your measurements do not fit the clinical picture, search for views or angles that may indicate that your measurements are not accurate.
|
| Accuracy Factors |
| Resolution |
| Focal Point |
| Display Size |
| Sweep Speed |
| Consistency |
| Leading Edge Technique |
| Slope Points |
| ECG utilization |
|