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Medical Imaging

人工智慧在醫學影像的分析與應用·AI for Medical Image Analysis·2022S

Yenchuan Oi (胡彥川)

MeDA Lab || Department of Mathematics�National Taiwan University

2022/03/08

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Slide Credits

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Alphabetical Order in Last Name�Tinghui Wu�MeDA Lab, National Taiwan University

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Outline

  • Image Structure
  • Medical Imaging
  • Medical Image File Format
    • DICOM
    • NIfTI

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Image Structure

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Grayscale / RGB

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https://medium.com/@ageitgey/machine-learning-is-fun-part-3-deep-learning-and-convolutional-neural-networks-f40359318721

https://e2eml.school/convert_rgb_to_grayscale.html

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Pixels / Voxels

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https://pubmed.ncbi.nlm.nih.gov/25945121/

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Mask

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  • Same size as the image
  • Purpose
    • Remove unimportant information
    • Perform segmentation

https://help.apple.com/assets/5D6EB1CB094622CB34375CC7/5D6EB1D4094622CB34375CDC/en_US/bfc313b52ddd704c03eac92d5e60e76a.png

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Mask

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https://www.independent.co.uk/news/world/americas/monkey-selfie-david-slater-photographer-peta-copyright-image-camera-wildlife-personalities-macaques-a7941806.html

0000000000000000000000001111111111110000000000000

00000000000000000000011111111111111111110000000000

00000000000000000011111111111111111111111100000000

000000000000000111111111111111111111111111100000000

000000000000011111111111111111111111111111110000000

000000000001111111111111111111111111111111110000000

0000000011111111111111111111111111111111111110000000

0000001111111111111111111111111111111111111110000000

0000011111111111111111111111111111111111111110000000

00111111111111111111111111111111111111111111110000000

11111111111111111111111111111111111111111111110000000

11111111111111111111111111111111111111111111110000000

11111111111111111111111111111111111111111111110000000

11111111111111111111111111111111111111111111100000000

11111111111111111111111111111111111111111111100000000

11111111111111111111111111111111111111111111000000000

Image

Mask

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Medical Imaging

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Computed Tomography Scan

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https://www.ipfradiologyrounds.com/_images/image-reconstruction-planes.png

Coronal

Axial

Sagittal

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Computed Tomography Scan

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  • Hounsfield Unit (HU) Scale
    • Linear transformation of the attenuation coefficient measurement
    • HU value of water = 0 / air = -1000
    • Frequently used in CT images

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Window width / Window level

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https://erj.ersjournals.com/content/34/1/42.figures-only

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Window width

Window level

Abdomen soft tissue

400

50

Liver

150

30

Bone

1800

400

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Window width / Window level

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Image Spacing

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https://dicom.innolitics.com/ciods

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Image Spacing

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(0.68, 0.68, 1)(mm)

(0.59, 0.59, 5)(mm)

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X-ray / MRI

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Medical Image File Format

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Medical Image File Formats

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  • Medical image file consist of:
    • Image data: numerical values of image pixels or voxels
    • Metadata: information that describe the image

https://www.researchgate.net/figure/DICOM-object-with-metadata-and-image-The-header-is-zoom-in-right-hand-side-and-it_fig2_260374716

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DICOM

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  • Digital Imaging and Communications in Medicine (.dcm)
    • standardizes the images generated by diagnostic modalities
    • contains DICOM tags which describe metadata of images
    • often holds a single 2D image data
  • List of DICOM tags

https://www.dicomlibrary.com/dicom/dicom-tags/

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NIfTI

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  • Neuroimaging Informatics Technology Initiative (.nii or .nii.gz)
    • aims to facilitate and strengthen post-processing analysis
    • contains NIfTI fields which are similar to DICOM tags
    • often holds a 3D image data
  • Some of the NIfTI fields

https://brainder.org/2012/09/23/the-nifti-file-format/

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Thank You

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