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[33]
training may include the implementation of specific stroke dispatch criteria, dispatch call monitoring ,
[34]
telemedicine to triage cases prior to activation and use of more accurate stroke scales . The challenge
should ideally be nation-wide and involve government with initiatives such as “calling stroke a national
priority” .
[35]

Another main hurdle in the implementation of an Air-MSU for acute stroke care in geographically large,
underserviced areas is the significant development necessary to integrate a CT scanner on board a flying
ambulance. Alternate imaging devices for diagnosis and differentiation of the different stroke subtypes
should, therefore, be considered and may be equally advantageous in acute stroke management.

ALTERNATIVE STROKE ASSESSMENT OPTIONS - AN ALTERNATIVE TO A CT SCANNER
In recent years intensive research has been undertaken to investigate new, lightweight, portable, and
affordable devices with the aim of making a fast and accurate on-site diagnosis. Pilot protypes of devices
being currently developed aim to reduce weight from around 500 kg to 50-100 kg. Many of these are newly
developed imaging devices with a focus on identification of intracranial changes after brain trauma, such as
subdural haematoma or deterioration due to brain edema hours to days after stroke symptom onset, when
[36]
structural changes are more easily detectable . Only few devices have been developed which have the
potential to differentiate ischaemic vs. haemorrhagic strokes within the first hour after symptom onset. This
differentiation is the most critical goal, given that administration of thrombolysis could be catastrophic in
intracerebral haemorrhage. One of these is using a microwave technique, which can detect changes in the
electrical properties of brain tissue due to change in blood flow, water content, and temperature with a high
sensitivity. In early clinical tests, the ability of microwaves to differentiate haemorrhagic stroke from
ischaemic stroke was described with an area under the curve of 0.85-0.88 . Further research is necessary to
[37]
increase the understanding and the potential area of usage for this novel diagnostic strategy and as to
whether the sensitivity and specificity are high enough for clinicians to confidently exclude the presence of
blood to enable thrombolysis remains to be seen.

The CT scanner currently used in most mobile stroke units weighs at least 500 kg. There is the potential for
the development of light-weight portable CT scanners using novel, non-thermionic nanotube technology.
This allows miniaturization of the scanner and has no moving parts. This is another exciting research
avenue for road and air transport platforms, to serve rural and remote populations .
[38]

It is well known that intracranial large vessel occlusions can be visualized with a transcranial ultrasound
technique . Special ultrasound devices combining artificial intelligence, robotics, and automated cerebral
[39]
[40]
ultrasound are under development to enable an operator-independent tool to identify acute stroke .
Mobile transcranial ultrasound has been shown to identify an acute anterior large vessel occlusion stroke
[41]
with a sensitivity of 78% and specificity of 98% .
Specific biomarker analysis is an alternative point-of-care blood test, which could be an ideal tool for a pre-
hospital stroke assessment. The STROKECheck device uses the identification of the biomarkers GFAP,
RBP-4, and NT-proBNP to differentiate ischaemic stroke including large vessel occlusion from
haemorrhagic strokes and stroke mimics. The device is currently being investigated in a pre-hospital trial
(Biomarkers for Initiating Onsite and Faster Ambulance Stroke Therapies, Bio-FAST, ClinicalTrials.gov
Identifier: NCT04612218) in southern Europe. First results of 90 participants showed that 84% of ischaemic
stroke patients could be identified with the biomarker device without incorrect identification of
intracerebral haemorrhage . Table 1 gives a summary of the above mentioned novel diagnostic tool with
[42]
available evidence and ongoing clinical trials.