Using the anti-correlation between oxy and deoxy hemoglobin for NIRS data quality

46 sec read

Back in 2009 we published a paper titled “Functional near infrared spectroscopy (NIRS) signal improvement based on negative correlation between oxygenated and deoxygenated hemoglobin dynamics“. In a nutshell, we found the oxy- and deoxy-Hb are negatively correlated when noise level is low. When noise level increases, their correlation becomes more and more positive.

Correlation between oxy and deoxy-Hb
Correlation between oxy and deoxy-Hb

Based on this phenomenon we can check the noise level of a channel using the correlation. Below is the script. You simply input the hbo and hbr data (both matrix), and the output is the bad channels.

function badChannels = checkDataQuality(hbo,hbr)

% function badChannels = checkDataQuality(hbo,hbr)
% Check data quality using correlation between hbo and hbr as indicator
% if the correlation is strictly -1, then bad channel
% if the correlation is > 0.5, then bad channel
% Input: hbo and hbr are NxM matrix, N is number of scan, and M number of
% channels
% output: array of bad channels
%
% Xu Cui
% 2009/11/25

n = size(hbo,2);
for ii=1:n
    tmp = corrcoef(hbo(:,ii), hbr(:,ii));
    c(ii) = tmp(2);
end

pos = find(c==-1);
if ~isempty(pos)
    disp(['Channels with -1 correlation: ' num2str(pos)])
end

pos2 = find(c>0.5);
if ~isempty(pos2)
    disp(['Channels with >0.5 correlation: ' num2str(pos2)])
end

badChannels = [pos pos2];



写作助手,把中式英语变成专业英文


Want to receive new post notification? 有新文章通知我

第四十九期fNIRS Journal Club通知2024/02/24, 10am 高倩博士

竞技比赛中,特别是需要注意高度集中的射击项目中,如何保持稳定的注意控制对运动员的表现至关重要。近期的一项研究调查了赛前短时正念练习是否对运动员在射击比赛中的注意控制具有提升作用。来自北京体育大学心理学
Wanling Zhu
9 sec read

第四十八期fNIRS Journal Club视频 赵楠博士

Youtube: https://youtu.be/GgBR22PuJ0M优酷:https://v.youku.com/v_show/id_XNjMyNzU5ODYyNA==.html 随着人们逐渐依
Wanling Zhu
13 sec read

第四十八期fNIRS Journal Club通知2024/01/06, 10am 赵楠博士

随着人们逐渐依赖“线上”开展的教育、社交和旅行。探究实时“线下”和“线上”(网络摄像头)面部注视模式之间有怎样的差异是十分必要的。面孔加工的特征选择模型认为两者呈现的基本特征相同,因此无特异加工通路。
Wanling Zhu
9 sec read

10 Replies to “Using the anti-correlation between oxy and deoxy hemoglobin for…”

  1. @Gu Yue
    Good question! I however do not know the answer. You can try it and see if it increase your data quality. I’d love to know the result.

  2. Dear Cui,

    I’m wondering how to deal with these bad channels. Can I use the interpolation method which has been frequently employed in processing EEG data? I mean used the average value of whole channels to replace the bad channels Or just delete data on the bad channels?

    I’m looking forward to hearing from you!

    Yafeng Pan

  3. Dear Pan,
    Have you used the average value of whole channels to replace the bad channels of fNIRS? could you tell me your article name? thank you

    wenfeng Wu

  4. Dear Xu Cui,

    How/why did you choose the threshold of 0.5 (if if the correlation is > 0.5, then bad channel)? I read your paper but I could not figure out why 0.5 should be the right value, but I am very curious to know! Thank you.

    Kind regards,
    Carly

    1. Carly,

      The threshold 0.5 is arbitrarily chosen based on our observation. There is no theoretical basis. Please feel free to use your own threshold.

      Xu

  5. I was wondering if the code you gave is used then should we use the original signal or the filtered and de-headed signal?

      1. Hi Xu Cui,

        I believe the questions is whether any preprocessing should be performed before calculation of the correlation. For example, should the data be band-pass filtered and then we calculate the correlation?

        As a second question, I was wondering if having a longer block would affect the negative correlation bet oxy and deoxy hemoglobin, considering that during the plateau blocks, the anticorrelation decreases. Up to what block length would you expect that the negative correlation assumption holds true?

        Kind regards,
        Paulo

Leave a Reply

Your email address will not be published. Required fields are marked *