Analysis of ASL Images with ExploreASL

[ANINDITA BHATTACHARJEE Res. Scholar, School of Biomed. Engg. IIT (BHU)]

Hello Jan,

Let me introduce myself; I am a Ph.D. research scholar at the Indian Institute of Technology (IIT), BHU University campus, Varanasi city (located in the state adjoining the capital, New Delhi, India). I am trying to do a multi-modal imaging study of aging and the neurodegenerative process.  

For my research purpose, I am working with PET and MRI images. For PET imaging, I have analyzed PET images (OASIS database) to calculate the amyloid load using the Clinica Clinica Documentation (inria.fr) platform. Regarding MRI images, I am using the OASIS image bank, and with the help of the ExploreASL toolbox, I am trying to calculate the cerebral blood flow of those patients, whose amyloid load I already calculated earlier.

Fortunately, using ExploreASL, I got CBF values for one image from the OASIS database (first link), and, thereafter I worked on 30 images. 

  https://drive.google.com/drive/folders/1D_Yn9Iq6RmpVGQoI-sFxsHgV-w7rqdpa?usp=sharing  

From my experience, I can see ExploreASL can perform CBF estimation on 5-6 images in a group. I am sharing the folder with you (second link).

  https://drive.google.com/drive/folders/1C7YA_hEcO-o-ZCDeLqqHJvBeI1IxjJAO?usp=sharing  

 I will greatly appreciate it if you kindly give some feedback on whether these results obtained by Explore ASL are acceptable. 

The values that I have obtained for CBF using ExploreASL are:

(1) Grey Matter:  42.72 ± 1.14 ml/100g/min.  

(2) White Matter: 7.92 ± 2.75 ml/100g/min (values of some cases are negative such as - 2.78 or - 0.36, as you can see in the attached folder).

Furthermore, I am attaching one paper, Pantano et al, containing standard CBF values. Here, these authors used a different method (PET radionuclide imaging). This paper estimates the values as (these values also corroborate approximately to the "gold standard" CBF values obtained invasively in the human brain by other authors):

(1) Grey Matter:  50.7 ±10.3 ml/100g/min.  

(2) White Matter: 24.5±4.1 ml/100g/min..

As you can see, the CBF values of Grey Matter that I derived using ExploreASL, closely matches the Grey matter CBF values measured by Pantano’s radionuclide perfusion paper.

However there is no correspondence between (i) my White Matter CBF values derived using ASLExplore, vis-à-vis (ii) White matter CBF values obtained by Pantano’s PET Perfusion paper (sometimes my ExploreASL calculation gives “negative” values for White Matter CBF).  

I would be most grateful if you could kindly let me know why these two different results (Grey Matter, as contrasted to White Matter) are happening. Would you be so kind as to let me know how I can derive positive values for White Matter’s CBF.

As you are aware OASIS and ADNI imaging data banks are large international enterprises now, many governments have invested much public money in them, and many researchers across many countries work on these valuable mines of information. For example, ADNI programs are running in numerous regions, like the USA, Canada, Europe, Australia, U.K., China, and Japan.

As a Ph.D. student, I shall be most obliged to you for kind help.

I await your needful, please.

With best regards,

Sincerely,

Anindita Bhattacharjee

School of Biomedical Engineering,

Indian Institute of Technology (BHU),

Varanasi, India