EMS CT scanner?

[scubanurse]

How can ultrasound see anything through the skull? I thought EMS U/S was more for abdominal injuries?

[Arctickat]

How can ultrasound see anything through the skull?

With the exception of infants U/S can't.

[fakingpatience]

Hmmm... I heard that behind the ear (where the scull is thinner I guess?) it was able to, of course this is all just what I was told. I'll do some research and see if I can find anything

[scubanurse]

Even in the infants I've seen U/S used, they go through the fontanelle...even their skulls are thick enough to block the U/S...

[fakingpatience]

So, I found studies showing the use of transcranial doppler ultrasound to evaluate intercerebral blood flow.

"Cerebral angiography shows acute occlusion in 76% of acute MCA territory infarcts within 6 h of stroke onset.⁴ Follow up studies show spontaneous recanalisation in the majority by the end of 48 h and in up to 86% by 2 weeks.⁵ TCD can detect these angiographic occlusions with high sensitivity and specificity, and has a high positive predictive value.⁶

TCD has a specificity of 90% in demonstrating MCA occlusions in patients with acute MCA stroke within 5 h. Alexandrov et al have shown major arterial occlusions in 69% of patients with acute hemispheric stroke, who may be eligible for thrombolytic treatment.⁷ Recanalisation can be inferred by TCD by the appearance of flow in the vessel or an improvement in the flow, with or without reduction in the PI in the proximal segments of the vessel. Thus, in the setting of acute ischaemic stroke, TCD can reveal the presence of arterial occlusion and it can also show whether recanalisation has occurred following intravenous thrombolysis."

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2659960/

And from JEMS:

Diagnostic Ultrasound in Stroke Therapy
Ultrasound use is an area where EMS may be able to make a significant difference in stroke assessment and care. The use of ultrasound in stroke therapy is a relatively new practice. In 1981, Rune Aaslid, MD, created the first Transcranial Doppler machine (TCD), the “UrDoppler” at the then new vascular laboratory of the Neurosurgical Department of Inselspital in Bern, Switzerland. It’s still in use today. With the recent advent of cheaper, smaller and more user friendly machines, TCD is becoming more commonplace.

Although a CT scan is a powerful tool to detect the presence of bleeding in the brain, it’s limited in its ability to detect a blood clot. The opposite could be said of TCD: Although it’s unable to easily detect a head bleed, it’s readily able to find a clot. TCD was recently compared to CTA (a special type of CT with contrast) and found to have an overall accuracy of 89.4% in detecting embolic stroke, the most common type of stroke.⁸ When diagnosing stroke, it’s important to rule out a hemorrhagic stroke (head bleed) before administering clot busters because this could cause the patient to bleed out and die.

There are only two major types of stroke, embolic and hemorrhagic. The presentation of a patient with both embolic and hemorrhagic stroke is extremely rare. So if you can rule out one, then you can generally rule in the other.¹⁰ In essence, the diagnosis of the occlusion of a cerebral artery via TCD could possibly be enough evidence to allow for the administration of tPA in the prehospital environment. But that would mean paramedics would have to perform TCD in the field.

http://www.jems.com/ultrasound-in-stroke

How does transcranial Doppler ultrasound work?

Transcranial Doppler ultrasound works the same way as carotid Doppler ultrasound, except it is done on the head instead of the neck. A small hand-held device (called a probe) is placed lightly on your head, where it gives off ultrasound waves that pass into the body and bounce off the arteries and the red blood cells moving through them, like an echo. The echo from the moving blood is detected by the device. A computer converts the echoes into moving images of the insides of the blood vessels in the brain. Colors in the graphs may be used to show the speed and direction of blood flow.

http://www.hearthealthywomen.org/tests-diagnosis/index-tests/transcranial-ultrasound.html

[scubanurse]

Doppler is a different technique and will asses blood flow interruptions thought the skull.. U/S will visualize arteries. They are two different techniques I believe.

[fakingpatience]

Different techniques, but using the same machine though correct?

[scubanurse]

In my experience, the dopplers are separate machines but that is in the hospital. There are u/s machines that will show blood flow but I have only seen them as big machines. Dopplers are small hand held devices that do not show any images just transmit sounds.

[ERDoc]

An ultrasound can be used to produce a doppler image. An ultrasound just uses ultrasonic waves to bounce off structures of different types to create an image. Doppler imaging is based on the doppler affect. It uses ultrasonic waves to detect the change in the velocity of a fluid to determine the direction and rate of flow (velocity). Kate, the doppler you are thinking of is the one used just to get an audible confirmation of flow where actually visualizing it doesn't matter (fetal heart tones, presence of a peripheral pulse). It works on the same principles as a color doppler but does not produce an image.

[scubanurse]

What is EMS using? One of the articles has an image that looks like they are using the same as the hospital ones, but I imagine it is too large for the ambulance?