A non invasive way to measure icp this application

  • No School
  • AA 1
  • 360

This preview shows page 219 - 221 out of 360 pages.

a non-invasive way to measure ICP, this application continues to receive attention. Technique Probe selection Because the structures being imaged here are so superficial, the linear high- frequency probe should be used. Several ultrasound companies make probes specifically for ocular ultrasound that have a very small footprint and an even higher frequency than the standard vascular range ( > 10 MHz, as opposed to the standard 7–10 MHz). However, this special probe is not necessary for acquiring adequate images for the diagnostic applica- tions described here (although the higher the frequency, the more detailed the image). There is literature describing a coronal technique in which a small- footprint probe is placed in the temporal window over the temporal bone [ 14 , 15 ]. The eye is directed toward the probe and a cross-section of the sheath and the nerve is observed. There is evidence that this technique shows improved inter-rater reliability and does not have the same challenge of imaging through the lens which may distort distal imaging [ 14 , 15 ]. However, this technique has not been correlated with invasive measurements or Diagnostic ultrasound 205 Ocular ultrasound
Image of page 219

Subscribe to view the full document.

non-invasive surrogates for increased ICP, and as normal images appear to be smaller than those obtained with the linear probe, the nomogram for normal and abnormal images has not been defined. Moreover, this technique is optimized when a patient can direct his or her gaze toward the probe; this is not always possible in patients with increased ICP, and so it may not be a feasible alternative. Views When imaging the eye, it is prudent to apply a clear film adhesive strip or Tegaderm over the closed lid of the eye before applying the gel, to prevent contamination of the conjunctiva. In addition, it should be obvious that this exam is contraindicated in anyone with open ocular trauma or periorbital wounds, or in anyone in whom applied pressure could cause further injury. To perform the exam, the linear probe is rested gently on the orbital rim, with the gel providing the interface with the globe itself. Caution should be used when applying pressure on the globe from the probe. Occasionally, patients can have a vagal-type response to the increased pressure being applied to the globe (oculocardiac reflex). In rare cases, this stimulus can be enough to cause bradycardia and syncope. As with all imaging, it is standard to acquire images in two planes, transverse and longitudinal, to ensure true diameters are being measured. Scanning tips No nerve sheath shadow seen? ± For the nerve sheath shadow to be seen, the ultrasound beam or plane needs to transect the nerve, which enters the orbit at a slight angle. With gentle rocking of the probe or moving slightly to the lateral edge of the globe, the nerve sheath will usually come into view.
Image of page 220
Image of page 221
  • Fall '19

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes