Haha true. I try to make the videos better every time. I think the audio is better on later ones and I'll keep improving.

Haha, you're definitely right. Sometimes they have a point too. If I'm tired or lose enthusiasm my voice probably drops a register and I mumble. I try to do better these days, so hopefully it's better on the newer videos

@@LearnNeuroradiology Don't change your voice it's lovely.

Omg true, eventhough my primary purpose is to learn this for my test, I kinda find your voice an asmr :))

Thx for this good presentation ..

Thank you!

Great suggestion! We are always working on new content so we'll keep these in mind!

Glad you enjoyed it

Glad to hear that!

Thanks for checking it out!

Welcome!

Thanks a lot

Hi! Thanks for the question. We are a mostly Siemens site. It is beyond the scope of our discussion here what all the parameters for each sequence are, as it would be a lot of technical details that are usually provided by the scanner manufacturer. Plus, those parameters are available elsewhere. Some useful places to start are: radiopaedia.org/articles/mri-sequence-parameters?lang=us mriquestions.com/mra-parameters.html mrimaster.com/PLAN%20MRV%20BRAIN.html

Thanks for watching!

Most welcome

There is actually a variation of MR angiography designed to look at veins called MR venography (or MRV). Conventional MRA does not assess the veins well.

The posterior communicating arteries are very small, so it is a balance. Time of flight MRA depends on flow to generate signal, and small arteries quantitatively don't have that much flow. Plus they are smaller than the resolution of the method, so they can be hard to see. You can decrease the voxel size (thinner slices, smaller voxels) but then you have less signal in each voxel, so you may have to image longer. MRA at 7 Tesla is substantially better than 3 Tesla, and can see much smaller vessels for this reason. However, it probably doesn't matter. Any aneurysm big enough to cause a 3rd nerve palsy is probably going to be seen on an MRA (more than 95% of the time). If you still had concerns you would have to get a CTA or a catheter angiogram.

That's correct. MRAs image arteries. You won't see the veins on an MRA. There are MR venograms, or MRVs, for this purpose. However, symptoms from dural venous or jugular narrowing are quite uncommon except in a few specific diseases. Venous narrowing or obstruction has been blamed for many diseases over the years but few have been proven true.

​@@LearnNeuroradiologyI very much appreciate your response. I seem to have a chronic ear infection so that's why I suspect it could have spread to the veins, I get checked out next week so I guess I'll find out then. I will try and see if maybe the ENT could give me some more insight, as I know CVST is a rare complication of untreated ear infections. If I have any interesting updates I'll let you know!

Most of the time you can get similar information from an MRA without contrast. You should talk to your doctor about whether that's a good option for you. Additionally, depending on the severity of your reaction, you can often take some steroids and antihistamine the day before the exam and limit your risk of another reaction, so that's another option. Good luck.

Hi Doctor, Thank you for your response, really appreciate it. The Doctor gave me a referral for MRI non-contrast. The MRI result came back normal. This made me happy despite the symptom in my ear. The symptom is only present when I lay down but not in all positions. The Doctor stated that he recommends a CT scan of the temporal bones. This would require an injection and also exposure to radiation. Does the MRI show the temporal bones? I would rather do another MRI with injection instead of a CT scan. I have a referral to a specialist too and will book an appointment soon. Thank you very much Doctor and sorry for the long response. Kind Regards

@@DT-mw3ge The CT will show the bones better, and the amount of radiation is quite low. It is appropriate given your symptoms. Similarly, CT contrast is very low risk and worth it given the symptoms that you are having.

Hi Doctor, I hope you are well. Thank you for encouraging me to do the CT scan. After I had my MRI head that came back normal I wanted to give some time to see if the symptoms would disappear before I went for ct and put myself under radiation. To my surprise it only took few minutes and I expected to be under the machine longer than that. I finally went and had CT Temporal Bones. The report came back normal stating things like no mass lesion, no vascular dehiscence, no Sigmund sinus dehiscence and no destructive skull base mass etc. This is very good except that I still hear this pulse sound when I lay down, more noticeable on the left side than the right side. As I have done so many tests including MRI Head, CT Temporal Bones, ECG, Carotid arteries ultrasound, Chest MRI, Hearing test and ear cleaning I am left with few options. Apart from this pulse sound I also have some chest discomfort but the scan never shows anything. I had blood tests few months ago and it showed everything fine but iron level 8/10 but ferritin normal. My last two options are the blood test which I've done this morning looking into more details like full blood count, inflammation etc and the second is to have chest blood vessels angiogram. I never had chest angiogram, only MRI Chest that never says anything about my blood vessels. Because I have chest discomfort maybe my ear is picking on the internal sound. I dont know if something like that is possible but I know that I've done so many tests with no explanation and still have chest discomfort and still hear this pulse. I am 34, don't take any medications and no vitamins right now. I am able to exercise and do so 3-4 times a week when my busy life allows me to do so. I eat well too. I am doing all I can yet the pulse is still there when I lay down but chest discomfort I feel through the day too. Mind you, the pulse isn't very loud but can hear it. I am still able to fall asleep in certain positions and on the right side as my right ear is better and it doesn't wake me up through the night. Doctor, if you have any recommendations on any other test I could do please let me know. Thank you so much. Kind Regards.

Yes, I have seen MRAs on patients with meningitis and encephalitis. Most of the time they are normal. However, sometimes meningitis precipitates a reactive vasculitis (because the infection is in the subarachnoid space around the vessels). In those cases, the patient can have infarcts and abnormal MRA with areas of nodular vessel narrowing (just like other vasculitis). It's not mandatory, but I would say nearly every MRA of the head or neck in the US will have them. Most of the time they are generated by the technologists. I think the reimbursement may be slightly higher if there are 3D reformats.

LearnNeuroradiology Thank you.. so much information!!!. Do you know if injection dye is safe with brain bleeds? I enjoyed the videos man

IV contrast, either for CT or MRI, is generally safe in patients with hemorrhage.

LearnNeuroradiology thank you for your knowledge and wisdom

Thanks 😊

Yes. Many times you can see areas of narrowing or occlusion before a stroke. In those cases, the brain is still getting enough blood flow, either through the narrowing or from collaterals, that the brain doesn't have ischemia.

@@LearnNeuroradiology Hi, thanks for this. I had an MRI scan and I'm definitely no expert, but the images did not show much clarity for my vessels (the report came back fine). I suspect I have a blood clot and am getting and MRA/MRV. Is it possible that a normal contrast MRI of brain could miss blood clots which only MRA/MRV could pick up? Or is there some overlap, as in, maybe depending on the clot. I am getting my MRA/MRV scan done and was curious

An MRA is much more geared towards evaluating areas of narrowing or clot, and most MRIs without an MRI would not necessarily see a clot. I think you probably have to talk to your doctor about what symptoms make you concerned you have a clot so that it can be clear that you're getting the right kind of scan. If they need to, they can talk to the radiologist and ask what is the best way to evaluate a specific problem.

It is an individual decision, but the vascular neurosurgeons at our institution use MRA extensively for follow-up evaluation of treated aneurysms. They have found that it is just as good as an angiogram in most cases, and can avoid a lot of patients having a procedure. In these cases, we do special MRAs of the brain that do have a contrast injection to see any aneurysm filling better. (you can read more about it here: www.ncbi.nlm.nih.gov/pubmed/24994828). Sometimes, if we don't see it well we still recommend angiograms. Some neurosurgeons may not be familiar with this technique, or it might not be available at your institution. Catheter angiograms (DSA) are the classic gold standard and they may prefer it. Overall, it is a decision that you should make with the doctors treating you. In this case there is not a single answer that is 100% correct.

@@LearnNeuroradiology thank you for your time, very much appreciated. I understand your points, and the doctors treating me seem to rely mostly on MRA exams as well - I already had one a few months ago and the results showed what the doctors wanted to see. Another interesting read I stumbled upon is here: jnis.bmj.com/content/11/10/1009 Once again, thank you for your time and all the best for the future!

An MRA is designed to look at arteries and an MRV is designed to look at veins. You can achieve this by changing the direction of flow you are looking for, or by changing the contrast timing.

Congratulations on getting a covid vaccination! Thanks for committing to keeping yourself and those around you safe from the virus. Although it's not studied, the coronavirus vaccine will not affect your brain in any way on an MRI or MRA. You can get your scan right away, although you might feel tired a day or two after your shot, so you might delay it by a day or two just so you can be more comfortable.

@@LearnNeuroradiology Thank you so much for your prompt response, I will proceed with my scan. I have subscribed to your site to learn more about radiology. I will also recommend my friends to this site. Regards and good day.

@@LearnNeuroradiology If it has been studies, it will be prudent to say "may not" instead of being so definitive "will not." There should still be some common scientific sense and logics to equip real science believers with open-mind to all possibilities, which is the only way to propel science to move forward instead of falling into a massive maniac mentality like in "cult".

@@vickysongjnvickysongjn8881 Having read many brain MRIs on patients both vaccinated and unvaccinated, I can confidently say there are no effects of the Covid vaccine seen on brain MRI.

I definitely understand. I'm working on getting some new audio equipment which hopefully will help. Thanks for watching

I'd have to look it up, but my guess is 25%

​@@LearnNeuroradiologydoes it effect posterior circulation

Hey, thanks for checking in. I appreciate the comment. At least you tried to be positive about it. Thanks for the tip!

I usually don't think the posts making fun of my voice are that great, but yours is original and funny, so I'll give it to you!

I'm not really sure what you mean. Are you saying it would be helpful to have a written version? Or you have trouble understanding like some other comments?

It's cool how many voice experts there are on the internet. Thanks for watching the videos, lol

@@LearnNeuroradiology Sorry should have also mentioned I enjoyed the vid!

You should try watching at 1.5x speed. Maybe you would like it.

Seems to be a common comment around here that people don't like my voice.

Trolls these days are so lazy. Back in my day I would have at least looked up what the presenter looked like and made fun of his face.