The calculator in question is the SRU (Society of Radiologists in Ultrasound) classification of internal carotid artery stenosis. This classification system is used in the evaluation of patients with suspected carotid artery disease, specifically to quantify the degree of stenosis or narrowing in the internal carotid artery. 

The SRU classification is particularly useful in the management of patients with cerebrovascular disease, as it helps clinicians to stratify the risk of stroke and guide treatment decisions. It is based on ultrasound findings, including peak systolic velocity (PSV), end-diastolic velocity (EDV), and the ratio of these velocities in the internal carotid artery to those in the common carotid artery.

There are no specific exclusion criteria for the use of the SRU classification. However, it should be noted that this classification system is most accurate when used in conjunction with other clinical and imaging findings. It may be less accurate in patients with tandem stenosis (stenosis in more than one location), near-occlusion with minimal residual lumen, or in cases where technical factors limit the quality of the ultrasound examination.

SRU classification of internal carotid artery stenosis

# Description:
The calculator in question is the SRU (Society of Radiologists in Ultrasound) classification of internal carotid artery stenosis. This classification system is used in the evaluation of patients with suspected carotid artery disease, specifically to quantify the degree of stenosis or narrowing in the internal carotid artery. 

The SRU classification is particularly useful in the management of patients with cerebrovascular disease, as it helps clinicians to stratify the risk of stroke and guide treatment decisions. It is based on ultrasound findings, including peak systolic velocity (PSV), end-diastolic velocity (EDV), and the ratio of these velocities in the internal carotid artery to those in the common carotid artery.

There are no specific exclusion criteria for the use of the SRU classification. However, it should be noted that this classification system is most accurate when used in conjunction with other clinical and imaging findings. It may be less accurate in patients with tandem stenosis (stenosis in more than one location), near-occlusion with minimal residual lumen, or in cases where technical factors limit the quality of the ultrasound examination.
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# Inputs:
## Internal carotid artery peak systolic velocity, cm/sec
A. < 125
B. 125-230
C. > 230
D. High, low or undetectable
E. Undetectable

## Plaque estimate, %
E. None
F. < 50
G. >= 50
H. Visible
I. Visible, no detectable lumen
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# Scoring:
- If A and E, then Normal internal carotid artery
- If A and F, then Degree of stenosis is < 50%
- If B and G, then Degree of stenosis is 50-69%
- If C and G, then Degree of stenosis is ≥ 70%
- If D and H, then Near occlusion
- If E and I, then Total occlusion
- If true, then Use additional parameters)