Week 6!

Hi everyone and welcome to week 6 of SRP!

This week I spent more of my time with Dr. Silva interpreting images as opposed to sitting with the MR techs and watching the images being produced like I have been the last few weeks. I started of this week in the reading room watching the doctors go through scans and recording their observations about them. I was with them for about an hour before I realized they were interpreting CT scans and not MRI scans. CT’s are different from MRI’s because they take about a minute to scan the patient whereas MRI’s take around 30-45 minutes. Not only are they faster but they are much cheaper and more comfortable for the patient. However, CT scans are mostly useful for bone injuries while MRI’s are useful for soft tissue evaluation such as ligament and tendon injuries, brain tumors, and, pertinent to my project, prostate cancer.

In the CT scans I saw the doctors diagnosing, they were looking specifically for kidney stones. The stones appeared bright white on the scans since calcium shows up white. This is also why bone is very white in the CT scan below.  

The tiny white circle indicates the kidney stone and many times the stones are so small they are not detected by the doctors.

After spending some time interpreting the CT scans, I moved on to researching more about the prostate itself since the answer to my research question is backed up with evidence regarding the prostate and prostate cancer. I learned that there are two main parts to the prostate that shows up on MR scans.

The central gland and peripheral zone are the two parts that are examined to see whether or not the patients has prostate cancer. As suggested by the name, the peripheral zone surrounds the central gland and is seen as bright white on the picture above. The cancer is mostly in the peripheral zone which is why the zone is so enlarged in the picture. On a cancer-free patient, a prostate MRI would look like in the image below.

Dr. Silva taught me that the appearance of the peripheral zone and central gland on certain MRI series and the brightness or darkness of certain areas is a big indicator of whether or the patient has cancer. However, sometimes there are false positives and in the case of false positives, doctors must rely on some scans more than other. I will go into this more next week and I hope to see you then!

Week Five!

Hi everyone!

This week on the fifth week of my internship, I explored the differences between MRI machines themselves. The Scottsdale campus of Mayo Clinic has around four MRI’s with a power of 1.5 Tesla while the Phoenix campus has around seven 1.5 Tesla MRI’s and a few more MRI’s with powers of 3 Tesla. Without going too much into the physics of it, a Tesla is the standard unit of magnetic flux density and is equivalent to one kilogram per second squared per ampere.

But what’s the distinction between the 1.5T vs. 3T? Is a 3T MRI twice as good as a 1.5T MRI? Sure, as far as the magnetic field strength is concerned. Price-wise a 3T MRI is also usually double the cost of a 1.5T. However, a 3T MRI is not necessarily twice as adept as the 1.5T. There are many drawbacks to a 3T even if its stronger magnetic field will allow for better image clarity. For example the scan times for a 3T are much longer and as my project explores, the longer the time the scans take, the more likely patients are to quit the scans unfinished, causing an inaccurate diagnosis or other problems.

A 1.5T MRI is adequate for the majority of scan that are done on all MRI’s today so there isn’t much of a necessity for the 3T’s. But since the stronger magnetic field of the 3T increases the signal available which is what actually creates the image, the definition of the scans produced on the 3T are actually better. However, they are better at a cost and that cost is the increased scan times.

In every MRI scan there is always image noise. While image noise is not actually a sound, it interferes with the signals given out to create images and actually comes from the patient’s body and other electronics inherent in the MRI. Ideally, there would be no noise present but this isn’t possible so the goal is to have more signal in making the image than noise which can affect the quality of the image. The 3T and 1.5T both achieve this but in different ways. A 3T MRI gives out more signal or more molecules that are resonating in the greater magnetic field strength and it drowns out the image noise. The 1.5T, on the other hand, uses multi-channel phased array coils that gets closer to the part of the body that is being scanned to create an image that isn’t as “noisy”.

Below are images of the average 1.5T MRI vs the 3T MRI and as you can see there are differences on the outward appearance and not just the internal workings of the two scanners.

I hope to explore more on the image interpretation side of things next week at Mayo Clinic and I’ll see you all then!

Week Four!

Hi guys!

So in week 4 of SRP, similar to last week, I spent a lot more time with the MR techs than the radiologists. However, this week the MR techs scanned a MRE which is a specific type of MRI that combines MRI imaging with sound waves to create a visual map which shows the stiffness of body tissues.  Interestingly, MRE was invented at Mayo Clinic and is available there and at various other centers. Just as doctors feel around the abdomen to check for rigidness, the visual map of the MRE shows the hardness of certain areas. Blue signifies that the area is soft tissue while a red would mean severe stiffness and green would indicate an in-between of the two colors. An MRI scan is shown on the left and the MRE scan is on the right.

Knowing the stiffness of tissues is important because it is useful in diagnosis of a patient as a excessive stiffness would indicate disease or a tumor. MRE’s are usually used in diagnosis of liver cancer and today we compared a patient’s MRE from before and after treatment and the difference in hardness shown on the before and after MRE’s showed a dramatic change! The amount of stiffness or “red” on the scan had drastically decreased.

When I went in today to the clinic, I was hoping to witness a prostate scan which is what I’m specifically researching within MRI’s but the previous patients’ scans had all been delayed and I had to leave for work by the time of the actual prostate scan came around. However I did see a spinal scan and a breast scan in its place and learned more MRI terminology. The first thing I had to freshen up on was the different planes in which the scans are shown: sagittal, coronal, and axial.

These three planes are often abbreviated and written in the series of protocols to give the technicians an idea of how the patient is being scanned. Few more terms which I came to learn the meaning of were T1 and T2. T1 and T2 are imaging techniques that differ in the way liquid and fat in the body are shown on scans. In T1 scans, compartments with liquid such as cerebrospinal fluid (CSF) will appear dark and tissues with high fat content will show up bright whereas in T2 scans, the liquid will appear bright and the fat will be dark. You can see below the contrast between the two.

Learning the new terms certainly helped me understand how the series in protocols worked and how it ties into my project and it is something I will delve into in my next blog post! Stay tuned till then!