Advantages of Transcranial Power Duplex Imaging After Contrast Injection to Detect Low Flow in a Moyamoya Syndrome

To the Editor: We read with great interest articles recently published in Stroke by Nabavi et al,1 Goertler et al,2 and Postert et al,3 who reported an increasing interest for the diagnostic value of contrast-enhanced transcranial color-coded duplex sonography in ischemic cerebrovascular disease. To the best of our knowledge, however, transcranial power duplex imaging (TPDI) after contrast injection has not yet been evaluated in stroke patients. TPDI is one of the most recent development in neurosonology. Distinct from color duplex flow imaging (CDFI), PDI produces intravascular color signals based on the reflected echo amplitude, depending mainly on the amount of red blood cells within the sample volume. The consequence of this principle, associated with the use of special filter systems for blood/tissue discrimination, is an increased signal-to-noise ratio. PDI provides a more useful diagnosis in complicated, high-grade stenoses of internal carotid arteries (ICAs) than does CDFI,4 but it has not yet been studied in stenoses of intracranial arteries, even though a superiority of PDI over CDFI has been suggested regarding the depiction of central as well as peripheral segments of intracranial vasculature.5 Injection of contrast agent for ultrasound results in a significant signal enhancement of the cerebral arteries and improves the diagnostic usefulness6 of transcranial duplex imaging, but it has not yet been evaluated specifically in severe stenoses of intracranial vasculature. However, a recent study7 suggests a strong interest in using ultrasound contrast with CDFI in the differential diagnosis between subocclusion and occlusion of ICA, allowing the depiction of slow flow in large vessels. We would like to share our interesting experience of combining these 2 new duplex imaging modalities—TPDI with contrast injection—to improve cerebral artery delineation and to image low flow in a case of moyamoya syndrome. In October 1996, a 42-year-old …