Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasound in Children With Sickle Cell Disease

Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasound in Children With Sickle Cell Disease

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

Sickle cell disease (SCD) affects haemoglobin - the molecule in blood cells which carries oxygen. It causes red blood cells to become abnormal crescent (or sickle)- shaped. Sickled red blood cells cannot travel through small blood vessels as easily as normal red blood cells which can lead to blockages. This means that oxygen may be prevented from getting to where it is needed. Individuals with sickle cell disease also suffer form abnormality in the lining of their blood vessels, which contributes to the damage. Damage and blockage can occur in the blood vessels in the brain and means that children with sickle cell disease have a significant risk of suffering from strokes. Research has shown that transcranial Doppler ultrasonography can be used in this setting to identify children at most risk of getting strokes. Ultrasound is therefore used in children with sickle cell disease to measure the blood flow in the vessels in the brain. This research has formed the basis of the National Health Service (NHS) Standard of Care for Sickle Cell Disease in the United Kingdom (UK) which uses transcranial Doppler ultrasonography at once a year to screen children with sickle cell disease aged 2 to 16. Ultrasound is used because it is portable, does not uses ionising radiation such as x-rays, is non-invasive and gives good results. However, the results are dependent on the operator. This means that the screening service is provided by centres of excellence with experienced scanning staff visiting clinics in smaller hospitals with portable machines. There is a lack of research comparing the use of portable machines to laboratory-based machines. This is important because screening can identify children at high risk of stroke and may be used by clinical staff to make a decision about the care of the child.

Children aged 2-16 years of age with Sickle Cell Disease and under the care of consultant haematologist as part of the NHS screening programme.

Measurement of Time Average Mean of the Maximum (TAMM) in cm/Sec in Cerebral Arteries Using 2 Different Ultrasound Machines.

A flow phantom was used to compare Time average mean maximum velocity measurements from a Philips IU-22 and Zonare Z-One ultrasound machine. 25 children with SCD (aged 2-15 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 programme, were studied. The Time Averaged Mean of the Maximum (TAMM) velocities in the middle cerebral artery (MCA) and stroke risk categorisation using the two ultrasound machines were compared.

Inclusion Criteria: Clinical Diagnosis of Sickle Cell Disease Under surveillance as part of the NHS Sickle Cell & Thalassaemia Screening Programme Children between the ages of 2 - 16 years old. Those under 16 years of age must be accompanied by a responsible adult. Exclusion Criteria: Participants older than 16 years of age as this is outside the scope of the sickle cell screening programme. Individuals unable to give fully informed and voluntary consent. Individuals with inadequate temporal windows as it will not be possible to record measurements of velocity.