Comparison of a Portable and Non-Portable Ultrasound Machine in the Evaluation of Children with Sickle Cell Disease: A Pilot Study

Abstract

Background: Transcranial color Doppler (TCCD) ultrasound is used to identify children with sickle cell disease (SCD) at high risk of developing stroke. There is anecdotal evidence to suggest that different ultrasound equipment can give different blood flow velocities. The purpose of this study was to compare two different TCCD ultrasound machines. Methods and Results: A flow phantom was used to compare PSV measurements from a Philips IU-22 and Zonare Z-One ultrasound machine. Twenty-five children with SCD (aged between 2 and 16 years) attending the outpatient clinic at St. Mary’s Hospital, Imperial College Healthcare NHS Trust, as part of the NHS Sickle Cell & Thalassaemia (SC&T) screening program were studied. The two ultrasound machines compared the TAMM velocities in the middle cerebral artery and stroke risk categorization. PSV measurements using a flow phantom were underestimated by Philips IU-22 (31%) and Zonare Z-One (53%). TAMM velocities varied considerably between machines, with a poor agreement in stroke risk categorization. As a result, three children identified at increased risk of stroke by Philips IU-22 were not identified by Zonare Z-One. Conclusion: Two ultrasound machines were found to underestimate PSV using a flow phantom. The two ultrasound machines were shown to positively correlate, and this was statistically significant. However, there was variation in the TAMM velocities recorded by the machines which resulted in the different categorization of the stroke risk of a small number of the subjects. This pilot study confirms the feasibility and clinical significance of this investigation.

Keywords

• sickle cell disease
• stroke
• ultrasound
• transcranial doppler