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Computed DWI Plugin for OsiriX

If acquired data contains two b-value images in one single file, you have to separate it as two files that consist from single b-value images respectively (described later).

 

First, select two images (with “shift” button or “command” button). The example shows b=0 image (left) and b=999 image (right).

Second, start “Fusion” process as a standard OsiriX function. For that, click and hold the very small thumbnail, which locates the top of the image. You can start this process from both side; from low b-value image, or from high b-value image.

Then drag and drop it onto another image.

“Fusion” dialog will appear. Then, select “Computed DWI” function as shown in the figure.

Then, the control panel of cDWI will appear.

If “Computed DWI Plugin” can read the DICOM tag, b-values of the images are automatically displayed as the figure shows. If there is no value indicated, it means that “Computed DWI Plugin” cannot read the tag. Even in this case, you can input the b-values manually and get cDWI.

A b-value of the image can be changed interactively by moving slider (Figure). Alternatively, you can input the value you want into the box.
By the way, the signal intensity of the lesion should be changed dramatically by alteration of b-value, results in too dark or too bright, may cause difficulty of continuous observation of the lesion at arbitrary b-value. To avoid this inconvenience, “automatic window” function works to keep the signal intensity of the lesion with certain ADC value flat. The default value of the target ADC is 0.6✕10-3 mm2/s, and you can manipulate this value freely (described later).

In the initial setting, “Computed DWI Plugin” rejects to calculate the pixel with “negative” ADC value, which does not exist theoretically but exists in the actually acquired image. You can kill this function by check box off, but note that these pixels with negative ADC value appear as very high intensity spots (artifact).

In reality, the pixel with very small ADC value (such as ADC<0.4) is also rare. You can omit these pixels by changing ADC threshold slider. The figure shows an example at threshold of 0.4. This means the pixels with ADC value less than 0.4 will be disappear.

※ Additional preparation process for the case of two b-values in one single file

  1. Open the file by double click.
  2. Type “Command + E”. This is equivalent the process of “File”> “Export”>”Export as DICOM images”.
  3. In case of the images arranged with a manner of interleaved b-values, such as [b=0, 1000, 0, 1000, 0, 1000,,, and so on].

→ Set “Interval” as 2, and “From” as 1 for generation of b=0 images. Don’t forget to select “All images of the series, including”, instead of “Current images only”, as a default value. If you forget this, you will have only 1 image.

Then, set “Interval” as 2, and “From” as 2 for generation of b=1000 images.

In case of the images arranged with a manner of sequential b-values, such as [b=0,0,0,0,,, 1000, 1000, 1000,1000,,, and so on].

Set “interval” as 1, “from” as 1, and “To” as the half value of the number of the slices [Hf]  for generation of b=0 images. Then, set “interval” as 1, “from” as the next value of [Hf] , and “To” as the last number of the slices for generation of b=1000 images.

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