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Sharpening the Image

¹ Department of Radiology, Children's Hospital, 300 Longwood Ave., Boston, MA 02115.

View larger version (101K): [in a new window]   Fig. 1A. —Use of "Unsharp Mask" tool in Photoshop (Adobe Systems, Mountain View, CA). Original coronal sonogram of newborn with postinfectious hydrocephalus is shown on right. "Sharpen" is selected by clicking "Filter" menu bar (Filter Sharpen Unsharp Mask), as shown in upper left corner. "Unsharp Mask" dialogue window is shown in lower left. Note "Amount," "Radius," and "Threshold" sliders have been moved to left end of bars (arrows).

View larger version (102K): [in a new window]   Fig. 1B. —Use of "Unsharp Mask" tool in Photoshop (Adobe Systems, Mountain View, CA). Select the settings for "Amount," "Radius," and "Threshold" using sliders (arrows). Move "Amount" slider to right to setting of 100%, move "Radius" slider to setting of 2 pixels, and move "Threshold" slider to left at setting of 0 levels. Click "OK." Resulting sharpened sonogram image is shown on right.

View larger version (100K): [in a new window]   Fig. 1C. —Use of "Unsharp Mask" tool in Photoshop (Adobe Systems, Mountain View, CA). Example of oversharpened image. "Amount" slider has been set at 150%, and "Radius" slider (arrows) at 5 pixels. Resulting image on right is coarse and noisy.

View larger version (100K): [in a new window]   Fig. 2A. —Use of "High-Pass" filter in Photoshop (Adobe Systems, Mountain View, CA). Original unsharpened sonogram of newborn with postinfectious hydrocephalus is shown on right. Open "Layers" window (Window Show Layers), and duplicate background layer by dragging it to "Bent Page" icon at the bottom of "Layers" window (black arrow), as shown in left upper corner. Select "High-Pass" filter by clicking "Filter" menu bar (Filter Other High Pass) as shown in left lower corner. Click on background copy layer (white arrow).

View larger version (70K): [in a new window]   Fig. 2B. —Use of "High-Pass" filter in Photoshop (Adobe Systems, Mountain View, CA). Baseline "High-Pass" filter dialogue window is shown in left upper corner. Note "Radius" setting is at minimal setting of 0.1 pixels (upper arrow). "Radius" slider is moved to setting of 1.9 pixels (lower arrow). Resulting background copy layer image on right shows all nonedge areas have turned to neutral gray, and edges are barely visible.

View larger version (101K): [in a new window]   Fig. 2C. —Use of "High-Pass" filter in Photoshop (Adobe Systems, Mountain View, CA). Blending mode in "Layers" window is changed from "Normal" to either "Overlay" (black arrow) or "Soft Light." Resulting image blended image is shown on right. Image layers are merged by clicking on arrowhead on top marquee of "Layers" window (white arrow) and choosing "Flatten Image."

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