Figure 10: Using IVUS for treatment planning
Figure 10A: Assessing vein size before angioplasty: This axial IVUS illustrates some of the difficulty in assessing dimensions of veins and in choosing the proper balloon for safe and effective treatment of stenoses. Depending on orientations of the central ray of the fluoroscope and the vein axis, widely discrepant estimations of size may occur. The shortest diameter is less that 6 millimeters and the longest diameter is greater than 11 millimeters. Too small a balloon may be ineffective or result in short term clinical response. Too large a balloon may overdistend and injure the vein, thus increasing risk of stenosis or tear of the vein wall. Seeking a balloon 50% greater in size than this vein would indicate a balloon with CSA of about 100 mm2. A ...mm balloon was chosen.
Figure 10B: Quantifying stenosis: 1. Venography illustrates overdilation of the IJV during procedure done by a prior proceduralist. This stenosis was mostly likely caused by angioplasty of the incorrect segment or restenosis. 2. Curved echo represents wall of stenosed valves without remainder of vein excluded from direct flow. 3. Cross sectional measurement of both inner stenotic lumen and outer edge of wall, allows accurate calculation of percentage stenosis of 61.7% as opposed to values derived from diameter measurements ranging from 13% to 52%.
Table 1 Angioplasty balloon cross sectional area
Balloon Diameter (mm)
|
CSA (mm2)
|
|
Balloon Diameter (mm)
|
CSA (mm2)
|
5
|
2
|
|
12
|
113
|
6
|
28
|
|
14
|
154
|
7
|
38
|
|
16
|
201
|
8
|
50
|
|
18
|
254
|
9
|
63
|
|
20
|
314
|
10
|
79
|
|
22
|
380
|
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