Comparison of a Portable and Non-Portable Ultrasound Machine in the Evaluation of Children With Sickle Cell Disease - A Pilot Study
Phase: NA
Conditions: Sickle Cell Disease
Sponsor: Imperial College Healthcare NHS Trust

September 1, 2014 
Study Title: Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasound in Children 
with Sickle Cell Disease NCT: NCT02090881 Protocol ID: 13HH0858  
 
Patients with SCD age 2 to 16 years attending our tertiary paediatric haematology clinic for stroke 
surveillance were eligible. The study was conducted as part of a higher degree in vascular imaging 
and hence the study duration was limited to six months. Based on patient numbers within the 
service, we aimed to study 25 consecutive patients referred to the vascular sciences department for 
routine TCD scanning. Ethical approval was obtained from the local research ethics committee (ref 
13/LO/1503) and IRAS ID 133045) and written informed consent was obtained from legal guardians. 
A pulsatile flow simulating phantom was used to eliminate patient variability. Study participants 
were scanned by a single operator with imaging TCCD. Initially a full TCD assessment was performed 
using the non-portable Philips IU-22 with a S5-1 phased array transducer (5.0-1.0MHz). The 
measurement was then repeated in every patient in only the MCA on each side of the head using the 
portable Zonare Z-One scanner with a P4-1C phased array transducer (4.0-1.8MHz). For both 
examinations, a standardised screening protocol was used recording velocities from the 
transtemporal windows, a 5mm sample volume size, with no angle correction. Gain was adjusted in 
order to clearly see the spectral Doppler velocity waveform without the presence of noise in the 
background. For the purpose of this study, the TAMM velocities were compared because stroke risk 
categorisation according to the STOP trial was based on TAMM velocity, not peak systolic or end 
diastolic velocities. Each study was categorised as normal, conditional, abnormal or inadequate 
according to criteria previously developed by the STOP protocol. The participants were not 
permitted to sleep during the scan to avoid increase in blood carbon dioxide levels in sleep, which 
can result in increase in TCD velocities. Methods Patients with SCD age 2 to 16 years attending our 
tertiary paediatric haematology clinic for stroke surveillance were eligible. The study was conducted 
as part of a higher degree in vascular imaging and hence the study duration was limited to six 
months. Based on patient numbers within the service, we aimed to study 25 consecutive patients 
referred to the vascular sciences department for routine TCD scanning. Ethical approval was 
obtained from the local research ethics committee (ref 13/LO/1503) and IRAS ID 133045) and 
written informed consent was obtained from legal guardians. 
A pulsatile flow simulating phantom was used to eliminate patient variability. Study participants 
were scanned by a single operator with imaging TCCD. Initially a full TCD assessment was performed 
using the non-portable Philips IU-22 with a S5-1 phased array transducer (5.0-1.0MHz). The 
measurement was then repeated in every patient in only the MCA on each side of the head using the 
portable Zonare Z-One scanner with a P4-1C phased array transducer (4.0-1.8MHz). For both 
examinations, a standardised screening protocol was used recording velocities from the 
transtemporal windows, a 5mm sample volume size, with no angle correction. Gain was adjusted in 
order to clearly see the spectral Doppler velocity waveform without the presence of noise in the 
background. For the purpose of this study, the TAMM velocities were compared because stroke risk 
categorisation according to the STOP trial was based on TAMM velocity, not peak systolic or end 
diastolic velocities. Each study was categorised as normal, conditional, abnormal or inadequate 
according to criteria previously developed by the STOP protocol. The participants were not 
permitted to sleep during the scan to avoid increase in blood carbon dioxide levels in sleep, which 
can result in increase in TCD velocities. 
Study Title: Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasound in Children 
with Sickle Cell Disease NCT: NCT02090881 Protocol ID: 13HH0858 Statistical Analysis Spearman’s 
Correlation Coefficients were calculated to assess the relationships between different parameters in 

September 1, 2014 
order to assess the strength of the association between the two measures. Intra-class Coefficient 
Correlation (ICC) and 95% confidence intervals were used to provide a measure of the strength of 
the association between the measurements from both pieces of equipment and therefore the 
validity of the measurement. It has been stated that ICC >0.75 implies acceptable validity. 
BlandAltman plots were used to estimates the agreement between TAMM velocity measurements 
by determining how much the velocity from one machine differs from another. Statistical analyses 
were performed using SPSS Statistics version 21 (IBM). The level of statistical significance was 
defined as p < 0.05.  
Conclusion The purpose of this pilot study was to evaluate the use of a portable ultrasound machine 
by comparison with an established laboratory-based ultrasound machine. This study demonstrated 
complete agreement in stroke risk categorisation between the two instruments. As a pilot study, it 
confirms the feasibility and clinical significance of this investigation. A larger sample size with a 
greater range in TAMM velocities is needed to further investigate the correlation between different 
ultrasound machines at extremes of measurement such has very high or very low velocities. Further 
evidence is needed in order to establish the implications these differences may have on screening