A new 1-MHz probe for transcranial Doppler sonography in patients with inadequate temporal bone windows

Recent large-scale transcranial Doppler sonography (TCD) studies have revealed that, in 3%-5% of patients, the temporal bone window is insufficient for examination with 2-MHz probes. The diagnostic value of a new 1-MHz probe for TCD was compared with a standard 2-MHz probe in patients with an insufficient ultrasonic window. From a total population of 514 consecutive patients, the study involved only patients in whom a bad or absent temporal bone window was revealed during 2-MHz TCD examination. Fifty patients (39 women and 11 men) with a mean age of 71 +/- 9 y were investigated with a 2-MHz probe and subsequently with a 1-MHz probe. Using the 2-MHz probe, 18 patients (group I) lacked a temporal insonation window bilaterally, while 12 had an absent bone window unilaterally (group II). Twenty patients (group III) had bilateral bone windows, but with insufficient detection of the anterior and posterior cerebral arteries. In four of the 18 patients in group I (22%), the circle of Willis could be demonstrated with the 1-MHz probe. In 11 of the 12 patients in group II (92%), it was possible to demonstrate the contralateral vessels through the ipsilateral bone window with the 1-MHz probe, while this was only possible in 25% with the 2-MHz probe. All 20 patients of group III could be successfully examined with the 1-MHz probe. The 1-MHz probe provides an opportunity to perform TCD studies in older patients presenting with absent or insufficient temporal bone windows for examination with 2-MHz probes.