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October 29, 2014

What Causes the Knocking Sound in an MRI Scanner?

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Anybody who has undergone an MRI scan can tell you that other than the claustrophobia of being in an enclosed cylinder, the other bothersome part is the knocking sound that occurs. Here's a video (see below) that localizes where and why that knocking sound occurs.

The bottom line is that the sound is due to a helium pump that disperses liquid helium in order to cool the wires that control the magnets down to -269.1 degrees Celsius. MRI machines work by generating a very large magnetic field using a super conducting magnet and many coils of wires through which a current is passed. Maintaining a large magnetic field requires a lot of energy. By cooling the wires with liquid helium down to as close to -269 degrees Celsius as possible, the resistance in the wires is almost zero allowing for highly efficient maintenance of a high magnetic field. A typical MRI scanner uses almost two tons of liquid helium.

On a related note, check out this video of what happens inside a CT Scanner!


October 28, 2014

How Does a CT Scanner Work? [video]

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In medicine, we order a LOT of CT scans... but ever wonder exactly how it works? All we see is the donut shaped thing that patients go through the center of. Take a look at this video (see below) that shows what is happening on the INSIDE of the CT scanner as a patient goes through the center!

On a related note, ever wonder what that knocking sound is during an MRI scan? Read this blog article.


September 27, 2014

Video of Epley to Treat BPPV (Posterior Canal)

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This is the third in a series of videos our practice is producing on inner ear dizziness. This video demonstrates how the Epley maneuver is performed to treat posterior canal BPPV. Also demonstrated is what happens within the inner ear when the maneuver is performed correctly. The first video was on how the inner ear balance system works which can be watched here.

Soon to come are two more videos specifically regarding treatment of superior and lateral canal BPPV.

September 22, 2014

New Video on Tonsillectomy and Adenoidectomy (Re-mastered and in HD)

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Back in 2007, I uploaded a video on tonsillectomy and adenoidectomy which may have been cutting age at the time, but much has changed in the YouTube world including the usage of high definition and wide-screen format. I also purchased a new microphone since than so narration does not quite sound like I'm yelling all the time.

You can watch the "old" version tonsillectomy and adenoidectomy.

And here are the two new videos refreshed for 2012 that have been remastered and in HD:



September 21, 2014

Video on How the Dix-Hallpike Maneuver Diagnoses BPPV Dizziness

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This is the second in a series of videos our practice is producing on inner ear dizziness. This video demonstrates how the Dix-Hallpike maneuver is performed to diagnose BPPV. Also demonstrated are the different types of eye-twitching (nystagmus) that suggests what type of BPPV a patient may have. The first video was on how the inner ear balance system works which can be watched here.

Soon to come are videos specifically regarding treatment of BPPV. Watch this video!

September 20, 2014

Steroids Helpful After Tonsillectomy?

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Pain is perhaps the most common dreaded fear patients have when considering tonsillectomy surgery.  After pain, bleeding is perhaps the 2nd greatest concern patients have. With both these issues, steroids play a key role by helping with one at the expense of the other.

In the 2011 Clinical Practice Guideline: Tonsillectomy in Children, the authors strongly recommend giving a single large dose of steroids to help with not just pain, but also nausea and vomiting after surgery. It is not just in kids... Steroids also help with pain control in adults.

So if steroids are so helpful, why is only a single dose recommended? Why not give more?

Although there is little evidence that a single dose of steroids significantly increases the risk of bleeding in the post-operative period, there is concern that the same may not hold true if too much is administered. As such, routinely giving more than one dose of steroids is NOT recommended.

However, even with a single dose of steroids, there is still persistent concern for bleeding in children as a recent 2014 study found. As such, the (?nominal) bleeding risks need to be weighed against the definite positive benefit patients have in terms of reduced pain, nausea, and vomiting.

Given this background, the vast majority of ENTs who routinely perform tonsillectomy do give a single dose of intra-operative steroids given it is felt that the benefit does far outweigh the risks.

Another steroid dose "may" be given orally if pain suddenly increases 5-7 days after surgery, but certainly not something that is recommended to be done routinely and best to be avoided if possible.

References:
Clinical Practice Guideline Tonsillectomy in Children. Otolaryngol Head Neck Surg January 2011 vol. 144 no. 1 suppl S1-S30

Impact of Systemic Steroids on Posttonsillectomy Bleeding: Analysis of 61 430 Patients Using a National Inpatient Database in Japan. JAMA Otolaryngol Head Neck Surg. 2014 Sep 18. doi: 10.1001/jamaoto.2014.2009. [Epub ahead of print]

Effects of oral prednisolone on recovery after tonsillectomy. Laryngoscope DOI: 10.1002/lary.24958

Perioperative dexamethasone administration and risk of bleeding following tonsillectomy in children: a randomized controlled trial. JAMA. 2012 Sep 26;308(12):1221-6.

Dexamethasone and risk of nausea and vomiting and postoperative bleeding after tonsillectomy in children: a randomized trial. JAMA. 2008 Dec 10;300(22):2621-30. doi: 10.1001/jama.2008.794.

Steroids for improving recovery following tonsillectomy in children. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003997. doi: 10.1002/14651858.CD003997.pub2.

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