CVI may break ultrasound barriers

Philips hopes that color velocity imaging (CVI) will prove asrevolutionary to the ultrasound profession as the introductionof Acuson's 128-channel imaging eight years ago. CVI has the potentialto provide new information because it uses a non-Doppler techniqueto measure blood-flow velocity, said Thomas E. Bird, general managerof Philips Ultrasound in Santa Ana, CA.

Advances in high-speed processing enable Philips to calculateblood-flow velocity directly through the use of time/distancemeasurements (SCAN 2/14/90). CVI is not hampered, therefore, bylimitations inherent in Doppler's use of waveform measurementsto calculate velocity, Bird said.

"We can show new and better accuracy at estimating velocity.There is more information, and that new information has to findapplications," he said.

Philips hopes clinical research will prove that CVI is as accurateas spectral Doppler in estimating velocity. In other words, avelocity measurement obtained at any point on the CVI color mapcorresponds to the spectral Doppler measurement taken at thatsame point.

"We can derive a (velocity) value from any vessel we cansee and angle correctly. The role of color Doppler, on the otherhand, is to image the vessel so you can figure out where to placeyour sample volume. It (color Doppler) is only a road map to thespectrum, nothing more," said Thomas DiGiacinto, marketingdirector.

CVI's greater precision opens up the possibility of providingvolumetric information, which is beyond the capability of currentblood-flow measurement techniques. Philips is developing a color-quantificationcapability for CVI, but is cautious about making claims untilfurther clinical research is completed.

"In the laboratory, it (CVI quantification) is very accurate,but the proof of the pudding is in clinical studies," DiGiacintosaid.

CVI calculates blood flow velocity by tracking the speed ofparticular blood cells over minute distances. Philips disputesa claim made by competitor Acoustic Imaging that CVI cannot trackblood cells accurately when blood flow accelerates too rapidly(SCAN 3/16/88).

CVI's processing speed is more than sufficient to track anyblood flow in the human body, Bird said.

"Theoretically, cells could move fast enough that we wouldlose a degree of accuracy, but (the patient) would be dead bythat time," he said.

With 128 channels functioning simultaneously, CVI performs20 million to 25 million calculations per second, he said.