7. APPENDIX A: IMAGE THUMBNAILS ADDED TO DICOM IMAGES 7.1 IMAGE THUMBNAIL PathSpeedâ"¢ PACS will create a thumbnail for each DICOM Image SOP Instance of the following Photometric Interpretation values: * MONOCHROME1 * MONOCRHOEM2 * RGB The thumbnail is derived from the original pixel data by downscaling the image size to 128 Ã- 128 pixels or less, and added to the original SOP Instance with a private sequence data element in the DICOM Image SOP Instance. One thumbnail is created per DICOM image. For a multi-frame image, only one thumbnail is created from the center frame. The number of the frame, which is used for the thumbnail creation is included in the Image SOP Instance (see Section 7.3). In PathSpeedâ"¢ PACS, the thumbnails are used by the PathSpeedâ"¢ Web display application for image navigation when browsing through a set of images. With the information published in this Appendix, a DICOM application receiving the images from PathSpeedâ"¢ PACS can also explore the thumbnail data encoded in the Image SOP Instances. 7.2 IMAGE THUMBNAIL COMPRESSION The thumbnail is compressed with 8 bits or 12 bits JPEG lossy compression format, depending on the stored pixel depth of the original images. For all Image SOP Instances with bits stored equal to or less then 8, the thumbnail image is stored one byte per pixel and compressed by JPEG 8-bits lossy compression. For all Image SOP Instances with bits stored equal to or less 12, the thumbnail image is stored two bytes per pixel and compressed by JPEG 12-bits lossy compression. For all Image SOP Instances with bits stored greater than 12, the pixel data of the thumbnail image id first shifted to fit into the 12 bits scope and then stored two bytes per pixel The thumbnail is compressed by JPEG 12-bits lossy compression. The bits shifted is saved in the GE Private Image Thumbnail Sequence, as specified in the next section. All thumbnails are represented in the unsigned format (either byte or two-bytes (12 bits) integer). If an Image SOP Instance contains a signed pixel data element, the thumbnail pixel data will be offset to the unsigned scope. The offset added is saved in the GE Private Image Thumbnail Sequence, as specified in the next section. Page 55 7.3 IMAGE THUMBNAIL ENCODING PathSpeedâ"¢ PACS adds a private sequence data element (GE Private Image Thumbnail Sequence) to an Image SOP Instance for the thumbnail encoding. There is no any change to the existing data attributes of the SOP Instance. The GE Private Image Thumbnail Sequence is specified in the following table. Data Element Tag VR VM Description Private Creator ID (0009,00xx) LO 1 GEIIS, Reserve xx00-xxFF of group 0009 in the SOP Instance. GE Private Image Thumbnail Sequence (0009,xx10) SQ 1 Always only one item present > Sample per Pixel (0028,0002) US 1 Copy from the original SOP Instance > Photometric Interpretation (0028,0004) CS 1 Thumbnail Photometric Interpretation. Enumerated Values: MONOCHROME1, MONOCHROME2, RGB > Planar Configuration (0028,0006) US 1 Thumbnail Planar Configuration. Always 0, if present. > Number of Frames (0028,0008) IS 1 Copy from the original SOP Instance. The thumbnail itself is always single frame. > Rows (0028,0010) US 1 Thumbnail Rows of Image Matrix, ≤ 128. > Columns (0028,0011) US 1 Thumbnail Columns of Image Matrix, ≤ 128. > Bits Allocated (0028,0100) US 1 Copy from the original SOP Instance > Bits Stored (0028,0101) US 1 Copy from the original SOP Instance. If this value is 8 or less, the thumbnail JPEG stream is 8 bits compressed, otherwise, it is 12 bits compressed. > High Bit (0028,0102) US 1 Copy from the original SOP Instance > Pixel Representation (0028,0103) US 1 Copy from the original SOP Instance > Largest Image Pixel Value (0028,0107) US/ SS 1 Copy from the original SOP Instance > Pixel Padding Value (0028,0120) US/ SS 1 Copy from the original SOP Instance > Window Center (0028,1050) DS 1-n Copy from the original SOP Instance Page 56 > Window Level (0028,1051) DS 1-n Copy from the original SOP Instance > Rescale Intercept (0028,1052) DS 1 Copy from the original SOP Instance > Rescale Slope (0028,1053) DS 1 Copy from the original SOP Instance > Private Creator ID (0029,0010) LO 1 â€"GEIIS“, Reserve 1000-10FF of group 0029 in this item. > Shift Count (0029,1010) UL 1 Number of bits pixel values were shifted down to get them into the 12 bits range before JPEG compression. > Offset (0029,1012) UL 1 Value added to pixel values to convert them from signed to unsigned values before JPEG compression. > Actual Frame Number (0029,1014) UL 1 Actual frame number of image the thumbnail was generated from. For multi-frame images, this should represent the center frame. Only one thumbnail is created for the entire multi-frame image. > Private Creator ID (7FD1,0010) LO 1 â€"GEIIS“, Reserve 1000-10FF of group 7FD1 in this item. > GE IIS Compression Type (7FD1,1010) UL 1 PathSpeedâ"¢ PACS internally used data compression code. Always 26 for thumbnail > Pixel Data (7FE0,0010) OB 1 8 bits or 12 bits JPEG lossy compressed thumbnail image pixel data stream. TABLE 7-1: SPECIFICATION OF GE PRIVATE IMAGE THUMBNAIL SEQUENCE The GE Private Image Thumbnail Sequence includes a number of standard data elements directly copied from the original Image SOP Instance, to which the sequence is added. These data elements are marked as Copy from the original SOP Instance in Table 7-1. These data elements provide the original pixel data context from that the thumbnail has been derived. Note that they do not contain the values specific to the thumbnail. The GE Private Image Thumbnail Sequence uses a number of standard data elements to describe the properties of the thumbnail pixel data. Note that these data elements in this sequence really contain the values specific to the thumbnail, but not to the original image pixel data