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Table 2 Characteristics of included studies

From: Diagnostic value of transcranial ultrasonography for selecting subjects with large vessel occlusion: a systematic review

Reference Study setting Condition of interest Index test Reference test Number of patients included in the analysis Time interval from symptoms onset to index test Time interval between index test and reference imaging Experience of the researcher performing transcranial ultrasonography Type of transducer Frequency of insonation
Akopov and Whitman [19] In-hospital AIS TCD MRA, CT 12 Only the results of TCD that was performed within 24 h after ictus were analysed MRA was performed together with the first TCD examination for seven patients (included in the analysis). For all others, MRA was performed 24–72 h after the ictus and close to the second TCD (not included in the analysis) Unclear—TCD was performed by the authors Not specified 2 MHz
Bar et al. [23] In-hospital AIS TCCS ± contrast enhancement CTA 31 Within 3 h 20 min Three skilled sonographers with at least 5 years of experience in ultrasound diagnostics Sector 2–4 MHz
Boddu et al. [24] Unclear—“in the laboratory” AIS TCD MRA 128 Not specified—within 24 h in 33% of participants and within maximum 29 h in 67% of participants From 30 to 300 min (median 60 min) Credentialed neurosonologist Not specified 2 MHz
Brunser et al. [25] In-hospital AIS TCD (PMD) CTA 100 Mean 468 min ± SD 343.2 min Mean 77.8 min ± SD 88.5 min Experienced sonographer certified by the American Society of Neuroimaging Not specified
Gerriets et al. [26] In-hospital AIS, MLS TCCS CT 40 Only results of TCCS examination that were performed 8 ± 3 and 16 ± 3 h from onset were analysed 6 h Unclear—“three investigators” Sector 2.5 MHz
Gerriets et al. [27] In-hospital AIS TCCS ± contrast enhancement CTA, MRA, DSA 58 Immediately on admission, within 6 h from symptom onset (mean 3.4 h) Mean time difference = 0.8 h in 14 patients; 6.1 in 18 patients Doctors with at least 1 year of experience in the field of colour-coded duplex sonography of the brain-supplying arteries Sector 2–2.5 MHz
Goertler et al. [41] Presumably in-hospital, department of neurology AIS TCCS Contrast-enhanced TCCS 23 Within 5 h Not specified but both tests performed within 5 h from symptom onset A sonographer Sector 2–2.5 MHz
Guan et al. [28] In-hospital AIS TCD CTA 128 The mean time from symptom onset to admission was 12.3 (10.1) hours
The mean time from admission to TCD was 15.5 (SD 10.1) minutes
The mean time interval between both examinations was 89.7 (77.8) min
65% patients—less than 30 min difference between them; 25%, 31–90 min; 15%, more than 90 min but less than 180 min
Experienced sonographer Not specified 2 MHz
Kadimi et al. [43] Not specified—presumably in-hospital AIS TCD CT 4 Within 6 h Not specified—both CT and TCD were performed within 6 h of the onset of symptoms Not specified Sector 2 MHz
Kenton et al. [29] In-hospital AIS TCCS MRA 30 Ranged from 4 to 24 h, mean 15.4 h Within 4 h, range 15 min to 4 h; median, 2 h Not specified Curved phase array 2.25 MHz
Kern et al. [30] In-hospital, stroke unit ICH Native transcranial b-mode ultrasound, UPI with contrast enhancement CT 12 Unclear—on day 1 as soon as possible after admission 4.1 ± 2.5 h on day 1 (CT first) Sonographers Sector 2–4 MHz
Kukulska-Pawluczuk et al. [44] In-hospital ICH, MLS TCCS CT 39 The time between initial symptoms of focal neurologic deficit and hospital admission ranged from 1.5 to 48 h with a median of 5.9 h. Index test was performed not later than 12 h after initial CT which was done directly upon admission Not more than 12 h Unknown Sector 2.5 MHz
Leanyvari et al. [45] Unclear AIS TCD CT 12 Within 12.5 ± 8 h after stroke onset or not more than 24.5 h TCD measurements were made before or no more than 4 h after CT Not specified Not specified 2 MHz
Matsumoto et al. [31] In-hospital ICH TCCS CT 20 Within 21 h (within 12 h of the CT study which was performed 4.6 ± 4.4 h from symptom onset) Within 12 h (mean 3.9 ± 4.1 h) Not specified Sector 2.5 MHz
Nasr et al. [32] Outpatient, TIA clinic AIS TCCS MRI-3D-TOF angiography 116 Unclear but presumably within 24 h from the onset 4 h Unclear Not specified
Ovesen [42] In-hospital ICH Transcranial b-mode ultrasound CT, CTA 25 Within 4.5 h Mean 61.1 min (SD 26.6) Unclear (“a single observer”) Sector 1.7–3.1 MHz
Panerai et al. [20] In-hospital AIS TCD MRI-DWI 11 plus 9 healthy controls Within 48 h Median time interval 2 h (range 0.5–8 h) Unclear—performed “in a dedicated cardiovascular research laboratory” Not specified 2 MHz
Rathakrishnan et al. [33] In-hospital AIS TCD CTA 15 Not specified Within 24 h Not specified, a stroke neurologist credentialed in cerebrovascular ultrasound interpreted the TCD findings Not specified 2 MHz
Seidel et al. [34] In-hospital AIS, HT TCCS CT 32 For the purpose of the current review only TCCS findings which were obtained < 12 and 24 ± 4 h from symptoms onset were analysed Unclear but before TCCS Sonographer Sector 2–4 MHz
Seidel et al. [35] In-hospital AIS, HT TCCS CT, MRI in individual cases 55 Within 32 h (mean time 10.6 h (SD, 7.2; median, 8.5; interquartile range, 6.5 h after stroke symptom onset) Within mean time of 14 h (CT was performed immediately after stroke symptom onset with mean 3.3 h; SD, 3.0; median, 2.0; interquartile range, 3.75) The ultrasound investigator Sector 2 MHz
Stolz et al. [36] In-hospital AIS, ICH, MLS TCCS CT 61 Unclear, presumably within 24 h 3–12 h Four sonographers with sufficient experience with the method Not specified 2–2.5 MHz
Tang et al. [37] In-hospital, stroke unit ICH, MLS TCCS CT 51 Unclear but presumably within 24 h because time from symptom onset to reference imaging was 4.1 ± 3.7 h Not more than 12 h, average interval was 5.9 ± 4.0 h Well-trained and experienced sonographers Sector 2 MHz
Tsivgoulis et al. [38] Emergency department AIS TCD CTA 132 Within 24 h Range 10–130 min (median 35 min) Experienced sonographers Not specified 2 MHz
Tsivgoulis et al. [39] Emergency room AIS TCD (PMD) CTA, MRA, DSA 213 Within 24 h Presumed 24 h, angiography was performed within 48 h from ictus Stroke neurologists with specialised training and credentials in cerebrovascular ultrasound Not specified 2 MHz
Viola et al. [21] In-hospital AIS TCD (3D) MRA, CT 47 plus 67 healthy controls Within 3–24 h Unclear, presumably not more than 24 h—both tests were performed 3–24 h from onset Not specified Not specified 2 MHz
Wada et al. [40] Not specified AIS TCCS DSA 40 Within 24 h Not specified—“immediately before cerebral angiography” Unclear Not specified 2–3 MHz, 3700 Hz pulse repetition frequency, low-pass filter was 50 Hz
Zubkov et al. [46] In-hospital AIS TCD CTA 31 Approximately 30 h after symptom onset Unclear, presumably within 24 h Experienced ultrasonographers Not specified 2 MHz
  1. For the purpose of the current review, terminology used to describe an ultrasound probe has been standardised and phased array, sector and pulsed wave Doppler are referred to as the same type of probe
  2. 3D three-dimensional, AIS acute ischaemic stroke, CT computed tomography, CTA computed tomography angiography, DSA digital subtraction angiography, ICH intracranial haemorrhage, HT haemorrhagic transformation, MRA magnetic resonance angiography, MRI-3D-TOF magnetic resonance three-dimensional time-of-flight imaging, MRI-DWI diffusion weighted magnetic resonance imaging; PMD power motion-mode, SD standard deviation, TCCS transcranial colour-coded duplex sonography, TCD transcranial Doppler, UPI ultrasound perfusion imaging