Q & A with a Neuroradiologist
Everyone with a brain tumour knows about MRI (Magnetic Resonance Imaging). This technology in the field of radiology has transformed the way we see our brains. It is essential in diagnosing someone with a brain tumour. And radiologists, like Dr. Thahn Nguyen, a two-time Brain Tumour Foundation of Canada grant recipient, are discovering new ways to better diagnose diseases using only pictures of our brain.
What interested you about radiology?
I could help patients by providing a diagnosis based on detailed images of their body. I also like that radiology is a multi-disciplinary field where one needs to know computer science, physics and medicine.
Does brain imaging differ from other areas of the body?
Yes. The function and anatomy of the brain are more complex than for any other organs. Of course, I am biased because I am a neuroradiologist. I think there are are so many things we do not know about the brain, but we will probably discover in the next few years using brain imaging.
What sorts of things can you see from an MR image of the brain (with or without contrast)?
First, we can have a detailed anatomy of brain. It is like having a Google map of the city. We can see the buildings. When we give contrast, we see areas where there is the brain-blood barrier is absent or disrupted such as in tumours of infection. This is key to help the neurosurgeon to decide if the tumour can be resected and what deficit(s) a patient might have following the surgery.
Recently, MRI can also provide a little bit more information about the function of the brain such as the white matter tract integrity or blood supply to each region of the brain. For example, we can determine before an operation if a tumour is more likely to be benign or malignant based on the amount of blood supply. In gliomas, the presence of high blood supply to the tumour implies a more malignant tumour.
What can’t you see or determine through an image of the brain?
In general, images of the brain allow us to know the anatomy of the brain in a patient but it is more difficult to learn about the functions. We can tell where the tumour is in the brain but it is more difficult to determine how the tumour alters the function of the adjacent neurons. If a tumour is located near the expected area for speech on an image, we can perform MRI to determine if that area of speech is still functional, but this is not 100% reliable.
Are brain tumours easily detectable with imaging?
Size matters. Large brain tumours are easily detectable but small tumours might be difficult to differentiate from other pathological processes such as stroke and infection.
What are the challenges when diagnosing a tumour this way?
We are trying to predict the tumour subtype using imaging but it is not easy. For example, we know gliomas with the isocitrate dehydrogenase mutation (IDH+) have a better prognosis than the ones which do not have this mutation. We can measure a metabolite (2-hydroxyglutarate) that is produced by the IDH+ gliomas using a special type of MR technique called MR spectroscopy. However, this technique has not been very accurate so far in our hands. In general, it is difficult to accurately measure tumour metabolites in the brain using MRS when those metabolites are in small concentration.
Do scar tissue and tumour look the same in an image?
They can look the same on anatomical(conventional) MRI images but we can differentiate between the two using more advanced MR imaging technique which look at the blood supply or the density of cells.
What is the largest brain tumour you have seen?
I think that I have seen tumours that are at least 5-7 cm in diameter.
What, if any, strange/ unusual or interesting things when looking at images of a brain?
Certain structures of the brain or pathologies look like familiar pictures that we see in our daily life. For example, the midbrain looks the face of Mickey Mouse with his two big ears. Radiation necrosis can have a ‘’swiss-cheese’’ appearance because they are many holes in the image that we see. We give use those terms to help us remember the picture.
Does everyone’s brain look different in an MR image?
Yes and no. All of us will have common elements: cortex, thalamus, white matter, etc…However, each brain might ‘’age’’ differently depending on the presence of or not of underlying systemic diseases such as hypertension, diabetes, etc…
Where do you see imaging going in the future?
There will be more and more images of our body. Artificial intelligence will help the physicians to provide better diagnosis. Computer-aided diagnosis will absolutely be necessary.
What’s next for you in your research?
I am working on developing some standard diagnostic criteria to differentiate between radiation-induced brain damage and tumour recurrence. This will help avoid unnecessary delay in the diagnosis of tumour recurrence or avoid unnecessary surgeries for radiation necrosis. Learn More
What information would you most want patients to know?
Decision and treatment of patients with brain tumours can sometimes be very difficult. Cancer Care Ontario strongly encourages the use of multi-disciplinary tumour board rounds to discuss those cases. Make sure that there is a CNS tumour board round at your institution.
Brain Tumour Foundation of Canada is currently accepting 2018 research grant applications. The deadline for submissions is April 27, 2018.