#How to read mri images how to#

muscle: intermediate signal intensity (grey).urine, CSF): low signal intensity (black) The dominant signal intensities of different tissues are: T1 weighted sequences are part of almost all MRI protocols and are best thought of as the most 'anatomical' of images, resulting in images that most closely approximate the appearances of tissues macroscopically, although even this is a gross simplification. Again many use these words as if they are absolute terms and this leads to confusion (more on this issue here). When describing diffusion weighted sequences, we also use the term intensity but additionally we use the words restricted diffusion and facilitated diffusion to denote whether water can move around less easily (restricted) or more easily (facilitated) than expected for that tissue. NB: the word density is for CT, and there are few better ways to show yourself as an MRI noob than by making this mistake. 'the lesion is hyperintense to the adjacent spleen'. Does this denote a lesion darker than CSF or than the adjacent brain?ДЄs such it is preferable to either use absolute terminology or, if using relative terms, to acknowledge the comparison tissue e.g. In many other situations however use of relative terms leads to potential confusion.В Imagine a lesion within the ventricles of the brain described as 'hypointense'. In some instances this does not lead to any problems В for example, a hyperintense lesion in the middle of the liver is clearly hyperintense compared to the surrounding liver parenchyma. hypointense = darker than the thing we are comparing it toДЄnnoyingly these relative terms are used without reference to the tissue being used as the comparison.isointense = same brightness as the thing we are comparing it to.hyperintense = brighter than the thing we are comparing it to.Often we refer to the appearance by relative terms: When describing most MRI sequences we refer to the shade of grey of tissues or fluid with the word intensity, leading to the following absolute terms: This leads to a broad categorization as follows: A number of 'optional add-ons' can also be considered, such as fat or fluid attenuation, or contrast enhancement. This leads to a division of all sequences into proton density (PD) weighted,В T1 weighted, T2 weighted, diffusion weighted, flow sensitive and 'miscellaneous'. ItBe ItDy BidDy BaBy DooDoo, now line these up into the following table based on the appearance of T1 & T2.The simplest way to think about the multitude of sequences available on modern scanners is to divide them according to the dominant influence on the appearance of tissues. GBM: iso-hypo intense on T1, hyperintense on T2/FLAIR & surrounded by vasogenic edema (white area typically tracking an irregular pattern through the surrounding white matter), no diffusion restrictionДЄnd finally, Blood.The appearance of blood varied with age, but fortunately there is a mnemmonic to help. Here is an example of a Left MCA distribution stroke.Д¬NS lymphoma: iso-hypointense on T1, hyperintense on T2, enhances homogenously with contrast These sequences wonвЂ™t look super-crisp like T1. In AIS, the affected are will be white on the DWI images and black on the ADC as in the image below.

#How to read mri images how to#

In this post, letвЂ™s take a look at the basics of how to read a brain MRI, because it often canвЂ™t wait until the radiologist gets in in the morning.ДЇirst, acute ischemic stroke (AIS).The 2 series you will want to pull up next to each other are the DWI (diffusion weighted image) & ADC (apparent diffusion coefficient).