iliac vessel attractors

When I left off last night, I was talking about how to use the concept of attraction to help in tracking iliac arteries.  In general the parameters that are available to be modified in my algorithm are the current direction vector (as determined by the longest continuous directional line path), the previous direction vector, and the overall bias vector (a vector that points in the general direction that one expects the vessel to travel). 
As the difference between the current direction vector and the bias vector increases, the contribution of the bias vector is proportionately increased.  The contribution of the previous vector is meant to buffer rapid changes in directionality.  Simple combinations of these three vectors have at one point or another successfully tracked every iliac vessel in my data set.  When dealing with situations like this in the past, my method has been to build in adaptive logic; for example, rather that setting a range of values that may be vessel, the algorithm goes to the last known point of vessel lumen and samples the average density of the contrast at that level and produces an average value around which a range us created.  This process allows the algorithm to accept very high or low density points only in situations where the scan and contrast quality require it.  The probem with the iliac vessel course is that there is not really a good predictive way of determining which parameters to use. 
Interestingly, in previous versions of the software, I used an algorithm which did essentially what I am try to achieve now, which is perform the tracking using a set of varying parameters and determining which ones result in a vessel end point close to the expected location.  The major problem with the previous algorithms was that it was very time consuming.  The current algorithm run in the 1-2 second range and achieves successful tracking in > 90% of vessels which means that the cost per additional vessel tracked will be very high.  One thought is that the since the algorithms already is biased so heavily towards finding the attractor, a validation step should be inserted after the initial iliac tracking algorithm to see if the endpoint and path are reasonable.  If not, the full algorithm can be attempted which evaluates a larger (though still restricted) portion of the parameteric space. 
This kind of logic check is smattered throughout the overall code and serves to reduce the overall run time by excluding computation that are unnecessary and dedicate additional resources to situations where the result is too complex for the simple algorithm. 
Alright, I have to go to the DICOM standards meeting in the morning and so I will call it a night.