Tuesday, February 06, 2007

2006 for CT Angiogram and other non invasive scans

2006 was an interesting and challenging year for the 64MSCT. Nationally, we saw more machines being purchased and installed. I am not sure where all the indications are coming from.

Speaking of indications, we learned that 64MSCT is invaluable in the ER to screen patients with chest pains for CAD, so that we would know whether to admit or to send them home. Using the scans to guide lipid lowering therapy is also a good indication. Somehow, using it as a non-invasive tool to screen for CAD is not yet an established indication. This is obviously because, although the negative predictive value is 98% or thereabouts, the positive predictive value is only about 92-95% in most academic institutions, who do and correlate their scans. Not to forget also that these scans have unevaluable segments (in some cases up to a third). The need for beta-blockers with the present generation 64MSCT, and also the radiation (equivalent to 500 CXRs) must not be forgotten. 2006 saw all these factors better understood.

In our own practice, across the board, the 64MSCTs score about 50% accuracy, when we had to study them, and most of the errors seem to be over-reading (meaning a 50% stenosis is read as 70% or more, resulting in more patients getting unnecessary angiograms).

Over the horizon, the Toshiba chaps have just install two 256slice MSCT in the USA. The last American Radiological Society meeting in Chicago in Nov, showcase the prototypes from Siemens, GE, Toshiba, and Philips. I was told that the machines are all faster, with newer dual source X-rays scanning at the same time, so as to lessen scan time, so as to lessen breath-holding. The newer scans also allow pulsing of the X-rays so as to lessen radiation. Looks like they heard all our earlier complaints and improved upon them. So the 2008 scans will probably be 256-slice, with one-third the scan time (so no need to hold breath and also no need for beta-blockers) with one third the radiation hazard. I think that the early experience presented in Chicago also showed a higher positive predictive value and much less non-evaluable segments.

As for the other scans (a few quick words). The MRI cardiac angiograms are getting very good, except it costs alot. This scan can study plaque morphology better, and lend itself to future molecular tagging during the scan, so as to better define tissues.

As for the common echocardiograms, well, the 4D hardwares are good and also tissue scanning is better refined, allowing a future role for tisue scanning and tissue pefusion grading. Basically, non-invasive techniques are better now. However, the professional discipline to use the scan properly (good medical practice conduct), is still sorely missing. That seems to be the biggest challenge for non-invasive scans in 2006 and also beyond.

powered by performancing firefox

No comments: