 We're talking pulsing sequences, basic-basic, T1, fat-weighted imaging, anatomy imaging on MRI. What are the strengths of the T1 and what projection should you use? Well, you should probably avoid the sagittal projection for a T1 because it doesn't really show the internal character of the uterus. So that's really reserved for the T2-FASPINECO. Your choices, therefore, are orthogonal or oblique axial and orthogonal or oblique coronal. The obliquity will depend on what you're looking for. If it's a standard exam, you'll do orthogonal. If it's an anomaly where you have to see a septum in the uterus, then you're going to have an oblique axial or an oblique coronal, which I will show you how to do. So here's the axial orthogonal T1 and a paired, as a reference, axial orthogonal T2. So the T1 being fat-weighted, you see an excellent fat-uterine interface. You see the sidewall of the uterus, the sidewall of the pelvis. Any infiltration there would be easy to discern. You'll also use the T1 as an anatomy image to look for lymph nodes. You might use it to look for deep vein thrombosis. Here are the round ligaments of the uterus, by the way. You'll also use the T1-weighted image as a characterizer. So let's say you see a fluid collection on T2. There's a fluid collection. You go over here and you say, OK, what does that fluid collection look like on the T1-weighted image? If it's truly fluid, it should look like cerebrospinal fluid, or vitreous humor, or urine. It should be dark on a T1-spinneco-fat-weighted image. It's not. It's bright. Therefore, it's got to be either protonaceous or hemorrhagic fluid from a hemorrhaged corpus luteal cyst. Or you could postulate an endometrium, which this patient doesn't have. Now let's go back to the ovaries. We've got several high-single-intensity foci on T2. We go over to the T1. Are they pure CSF-like in character? No, they're not. But are they bright on T1? No, they're not. So they're protonaceous cysts. Similarly, this one right here is a protonaceous cyst. It's low, but not as low as CSF, and high on T2. On the other hand, what about this one next to it, right there? The one with this thick rim around it? That thick rim is a combination of ciderotic change and fibrosis for this mass, or this quote-unquote cyst, is bright on T2 and bright on T1. Therefore, it's a hemorrhagic cyst. Now how could you prove that? One way to prove it would be to do fat suppression. If it completely suppressed out, you might consider a small dermoid. It didn't. It's a hemorrhagic cyst, and these type of cysts give rise to hemorrhagic fluid collections. So you're going to use the T1-weighted image for anatomic purposes, including looking at the bone marrow, and you're also going to use it to characterize abnormalities as being fatty, protonaceous, or simple fluid-like in their nature. Now let me put up the sagittal T2 image for a minute and show you how you might get an axial or coronal oblique if the patient has an anomaly. Now this patient has bent the uterus forward, antiverted, or antiflexed perfectly so that the axial that's going to go right down the barrel of the endometrium is going to be right here. If the uterus was flexed down a little bit more, then you would go this way. You always want to be along the longest axis of the uterus parallel to the endometrial stripe. So if the uterus was standing up like this, your paraxial or paracoronal would go this way. Your cervix would be back here, and your vaginal vault would be down here. So this is showing you how you would acquire in the paraxial or paracoronal projection the proper plane of imaging if you are searching for an anomaly such as a uterus with a delfus or a septate uterus or a bicornuit uterus. Let's move on from the T1 as a pulsing sequence for the pelvis.