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78
Chapter 8: References
Ref
e
re
n
ces
Volume Measurement
The volume measurement performed by iLook is an ellipsoid approximation of the actual volume
of the anatomical feature. That is, the formula used for the volume measurement is
where d
1
,
d
2
, and d
3
are the three measurements taken in cm., as described in
. Additionally, there are system tolerances related to the iLook volume measurement.
These system tolerances are given as a percentage based on the following formula:
where
ε
g = 0.01,
ε
0 = 0.02, and dmax = screen depth in cm. When each measurement taken is at least
20% of the screen depth, the variation in the system tolerance for the volume measurement ranges
from +/- 10% to +/- 35% in almost all cases.
Acquisition Error
Acquisition error includes errors introduced by the ultrasound system electronics relating to signal
acquisition, signal conversion, and signal processing for display. Additionally, computational and
display errors are introduced by the generation of the pixel scale factor, application of that factor to
the caliper positions on the screen, and the measurement display.
Table 1: 2D Measurement Accuracy and Range Table
2D Measure
Accuracy and Range
System Tolerance
a
Accuracy By
Test
Method
b
Range (cm)
Axial Distance
< ±2% plus 1% of full scale
Acquisition
Phantom
0.1-30 cm
Lateral Distance
< ±2% plus 1% of full scale
Acquisition
Phantom
0.1-35 cm
Diagonal Distance
< ±2% plus 1% of full scale
Acquisition
Phantom
0.1-30 cm
a. Full scale for distance implies the maximum depth of the image.
b. An RMI 413a model phantom with 0.7 dB/cm-MHz attenuation was used.
⎟
⎠
⎞
⎜
⎝
⎛
⎟
⎠
⎞
⎜
⎝
⎛
⎟
⎠
⎞
⎜
⎝
⎛
=
2
2
2
3
4
3
2
1
d
d
d
Volume
π
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
−
⎥
⎦
⎤
⎢
⎣
⎡
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
±
⎥
⎦
⎤
⎢
⎣
⎡
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
±
⎥
⎦
⎤
⎢
⎣
⎡
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
±
=
1
1
1
1
100
3
max
0
2
max
0
1
max
0
d
d
d
d
d
d
Tolerance
System
g
g
g
Volume
ε
ε
ε
ε
ε
ε
Summary of Contents for iLook
Page 1: ...iLook USER GUIDE...
Page 2: ......
Page 3: ...iLook USER GUIDE...
Page 8: ...vi...
Page 28: ...20 Chapter 2 Getting Started Getting Started...
Page 40: ...32 Chapter 3 The Exam Exam...
Page 64: ...56 Chapter 5 Safety Safety...
Page 88: ...80 Chapter 8 References References...
Page 94: ...86 Chapter 9 Glossary Glossary...
Page 100: ...92 Index Index...
Page 101: ......
Page 102: ...P02651 04...