Ultrasound Image Encoding Dave Heaney A L I

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Ultrasound Image Encoding Dave Heaney A. L. I. Technologies, Inc. 12/4/2020 1

Ultrasound Image Encoding Dave Heaney A. L. I. Technologies, Inc. 12/4/2020 1

Two Types of IODs w. Ultrasound Image IOD for single frame images w. Ultrasound

Two Types of IODs w. Ultrasound Image IOD for single frame images w. Ultrasound Multi-frame Image IOD for multi-frame images such as cine and 3 D acquisition. 12/4/2020 2

Several Photometric Interpretation Options w Monochrome 2 w Palette Color w RGB w ARGB

Several Photometric Interpretation Options w Monochrome 2 w Palette Color w RGB w ARGB (retired) w YBR_FULL_422 w YBR_PARTIAL_422 12/4/2020 3

Several Transfer Syntax Options w Little Endian Implicit (default) w Little Endian Explicit w

Several Transfer Syntax Options w Little Endian Implicit (default) w Little Endian Explicit w Big Endian Explicit w Lossy JPEG (various) w Lossless JPEG (various) w Run Length Encoding 12/4/2020 4

US Image Data Elements 12/4/2020 5

US Image Data Elements 12/4/2020 5

US Image Data Elements (cont. ) 12/4/2020 6

US Image Data Elements (cont. ) 12/4/2020 6

US Image Data Elements (cont. ) 12/4/2020 7

US Image Data Elements (cont. ) 12/4/2020 7

US Image Data Elements (cont. ) In addition there can be the Palette Color

US Image Data Elements (cont. ) In addition there can be the Palette Color Elements of the LUT Module for Palette Color Images. These will be covered in the LUT presentation. 12/4/2020 8

Compression Types: 1. Lossy JPEG 2. Lossless JPEG 3. Run Length Encoding 12/4/2020 9

Compression Types: 1. Lossy JPEG 2. Lossless JPEG 3. Run Length Encoding 12/4/2020 9

Lossy JPEG Important Points: w Default lossy JPEG Transfer Syntax is JPEG Baseline 1:

Lossy JPEG Important Points: w Default lossy JPEG Transfer Syntax is JPEG Baseline 1: 1. 2. 840. 10008. 1. 2. 4. 50, as 8 bit only image data. w Data Elements must be encoded Little Endian Explicit. w YBR yields a better compression ratio than RGB. YBR FULL 422 is most used (as per Application Profile). w Photometric Interpretation, and other elements, must indicate last state of data prior to compression (YBR FULL 442 if RGB is converted prior to compression). w Lossy Image Compression must be set to 01 (VR of CS). w If image is later decompressed set the Derivation Description (0008, 2111) (i. e. “ 10: 1 JPEG Baseline 1 Q=90”). 12/4/2020 10

Lossless JPEG Important Points: w Default lossless JPEG Transfer Syntax is Process 14: 1.

Lossless JPEG Important Points: w Default lossless JPEG Transfer Syntax is Process 14: 1. 2. 840. 10008. 1. 2. 4. 70. w Data Elements must be encoded Little Endian Explicit. w Can be used for Palette Color pixel data. w Lossy Image Compression must be set to 00 (VR of CS). 12/4/2020 11

Run Length Encoding Important Points: w Data Elements must be encoded Little Endian Explicit.

Run Length Encoding Important Points: w Data Elements must be encoded Little Endian Explicit. w Can be used for Palette Color pixel data (8 and 16 bit). w YBR color data generally yields better compression than RGB data (grayscale pixel values reduce to a single channel). Conversion from RGB to YBR is slightly lossy however. w RLE is done on byte per byte basis even for 16 bit data. Thus for 16 bit Palette Color data the 1 st RLE segment will contain the most significant bytes and the 2 nd segment the least significant. VR of Pixel Data Element will thus always be OB for RLE data. w Size of the RLE Header is always 16 long words, 64 bits, regardless of number of segments. 12/4/2020 12

US Region Calibration Module Important Points: w Unlike most other IODs scaling and calibration

US Region Calibration Module Important Points: w Unlike most other IODs scaling and calibration do not have to uniform across an entire Ultrasound Image. The US Region Calibration Module allows this specification. w A sequence of one or more regions can be specified. w Important to include to allow auto-scaling on workstations. w Not only for scaling information, can be used for: w w w 12/4/2020 pixel component description mapping from Pixel Value to Parameter Value transducer frequency for a region doppler information m-line specification 13

Other Notes w Compressed pixel data is contained in the Pixel Data Element (7

Other Notes w Compressed pixel data is contained in the Pixel Data Element (7 FE 0, 0010) which has a VR of OB or OW. Even though the encoding of the compressed data is actually done as if the VR is SQ, SQ must not be specified. w Study Description (0008, 1030) is widely used for specifying “Exam Type” w Interchange of ‘cine’ images generally requires support for lossy JPEG encoding. w In Ultrasound images overlay data is generally ‘burned in’ with image data. Support for bit map overlays may not be widespread. 12/4/2020 14