| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
infoRAD |
1 From the Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N Caroline St, Baltimore, MD 21287. Presented as an infoRAD exhibit at the 2001 RSNA scientific assembly. Received December 21, 2001; revision requested February 13, 2002 and received March 15; accepted April 23. Address correspondence to F.M.C. (e-mail: fcorl@jhmi.edu).
 |
Abstract |
|---|
 Top Abstract IntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
© RSNA, 2002
Index Terms: Images, hard copy • Images, processing
|
Introduction |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
|
System Requirements |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
Other image manipulation programs are available for both Macintosh and Windows-based computers. Photoshop Elements (Adobe Systems) is a limited version of Photoshop and performs all of the basic functions discussed in this tutorial. PhotoDeluxe (Adobe Systems), Photo-Paint (Corel, Ottawa, Ontario, Canada), and Picture Publisher (Micrografx, Dallas, Tex) also perform many of the functions addressed herein. The important features to keep in mind when looking for image manipulation software is multiple layers support, sophisticated image adjustment tools (eg, brightness and contrast, levels, and color balance), and support of both TIFF (tagged image file format) and JPEG (Joint Photographic Experts Group) file formats.
The basic system requirements for both Macintosh and Windows-based computers are given in the Table. Although Photoshop needs only 64 Mbytes of RAM (random access memory) to run, it needs three times the amount of RAM as the opened image file to perform most efficiently (eg, a 40-Mbyte file needs 120 Mbytes of RAM). Computers such as the iMac (Apple Computer) or Presario (Compaq, Palo Alto, Calif) system, both priced under $1,000.00 each, run Photoshop effectively.
|
The most commonly used scanner is the high-resolution desktop flatbed scanner with a transparency adapter. This type of scanner can scan positive prints, transparencies such as radiographic film or slides, and negatives. Advantages of this type of scanner are its versatility and its ability to scan large images. We use a PowerLook 1100 scanner (UMAX, Fremont, Calif). Flatbed scanners are also available from companies such as Hewlett Packard (Palo Alto, Calif), Microtek (Redondo Beach, Calif), and Canon (Newport News, Va). The average size of a flatbed scanner bed is roughly 8.5 x 14 inches.
The second type of scanner is a desktop slide scanner. This scanner is limited to scanning slides and 35-mm film negatives. Advantages of using this type of machine are its simplicity, small size, fast scanning speed, and the automatic multiple slide feed function. We use a LS-2000 (Nikon, Melville, NY). Slide scanners are also available from companies such as Minolta (Osaka, Japan), Imacon (Redmond, Wash), and Polaroid (Cambridge, Mass).
Printers
Many types of printers are currently available at a wide variety of prices. There are three common types of desktop color printers capable of printing photographic quality radiologic images suitable for publication, presentation, and day-to-day clinical use: ink jet, color laser, and thermal.
Ink-jet printers are the most affordable of the desktop color printers. Many ink-jet printers from companies such as Epson (Long Beach, Calif), Canon, and Hewlett-Packard offer four- or six-color printers at a resolution of 1,440–2,880 dpi. These photographic quality ink-jet printers range in price from $200.00 to $500.00. Color laser printers are a less affordable option, and only the high-end, high-resolution models offer photographic quality prints. Thermal (dye sublimation) printers are the most costly of the desktop printers, but they yield the highest quality professional glossy photographic print. Although the price of thermal printers has declined over the past couple of years, they are still a large investment and cost between $5,000.00 and $8,000.00.
Another option is to send the images to a print shop or service bureau for printing. If you have low workload, this may be a good option. Many small print shops or university graphics departments offer printing services.
|
Image Digitization and Manipulation |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
Handling Reflective, Transparent, and Negative Media.— The flatbed scanner can read three types of media: reflective, transparent, and negative. A reflective medium is any page or object that is opaque and reflects the projected light from the lamp of the scanner, such as a sheet of paper or photograph. A transparent medium is anything that is transparent or translucent, such as radiographic film or slide. A negative medium is any photographic negative.
To scan a print or any reflective page, place the image side of the page down on the scanning window facing the sensor of the scanner, usually located in the bottom of the scanner (Fig 1). The scanning bed has guides or rulers outside the scanning window that will allow you to place your image on the window squarely. Select the size, resolution, and color mode desired and preview the image. The preview mode is actually a quick prescan that allows you to change the brightness and contrast and to crop your image before you actually take the time to scan it. After the image has been previewed and all of the adjustments have been made, scan the image.
|
|
Setting Scanning Parameters: Size, Resolution, and Color Mode.— Although different scanning software interfaces look different, the basic scanning parameters are similar for both flatbed and slide scanning software. The basic and most important functions the user needs to understand to properly scan an image are size, resolution, and color mode (Fig 3).
|
|
Increasing resolution of an image that has been scanned at a lower resolution will not improve image quality. For example, an image imported from a workstation into Photoshop that is 512 x 512 pixels at 72 ppi has a print dimension of 7.111 x 7.111 inches. Changing the resolution of the image to 300 ppi while leaving the print dimension set at 7.111 x 7.111 inches will spread only the original pixel data across a greater number of pixels. A 512 x 512-pixel image at 300 ppi has a print dimension of 1.707 x 1.707 inches because the same amount of pixels (512 x 512) are smaller and more closely placed. Changing the print dimensions of the latter image to 7.111 x 7.111 inches will also spread the original pixel data across a greater number of pixels.
A resolution of 300 ppi should be used if the user plans to print the image (Foerster J, personal communication, 1996). If the user plans to display the image only on a computer monitor or to use it in a computer presentation, the resolution should be 72 ppi. The resolution and dimensions of the image determine the file size and quality of the final printed or electronically displayed image. Two 5 x 7-inch images with different resolutions have different file sizes. The image with higher resolution has the larger file size. The file size of a 5 x 7-inch color image at 300 ppi is roughly 9 Mbytes. That same image with a resolution of 150 ppi is roughly 2.25 Mbytes, and a third version with a resolution of 72 ppi is 0.5 Mbyte (500 Kbytes).
Monitor resolution is measured by the number of pixels or dots per unit on the computer monitor, usually dots per inch. The standard resolution of a PC monitor is 96 dpi, and the standard resolution of a Macintosh monitor is 72 dpi. Photoshop converts image pixels to monitor pixels (3). Printer resolution is described by dots per inch. Dots per inch refers to the number of ink dots per inch that a printer produces when printing an image.
The color mode setting allows the scanner to save an image in a specific color mode or in gray scale. Both a gray-scale radiologic image and a color image can be displayed in gray scale by scanning the image in gray scale. Gray-scale images have smaller file sizes than color images. A color image that will be displayed in color should be scanned in RGB (red, green, and blue). Computer monitors display colors in RGB (4). If the user is sending digital image files to an outside print shop, service bureau, or journal to be printed, the RGB files may need to be converted to CMYK (cyan, magenta, yellow, and black). In some instances, a user may own a printer that requires CMYK files; in this case, the images should be converted from RGB or gray scale to CMYK to print. Photoshop allows for simple color mode conversions.
Setting Other Prescan Adjustments.— Other tools that can be used to adjust an image while scanning are brightness and contrast, color balance, and the crop tool. We recommend that the user adjust the image as best as he or she can during the scanning process. Although there may be adjustment limitations with many scanning software packages, the higher the quality of the original scanned image, the more image data there will be to edit or adjust with Photoshop. A good image cannot be created from an inferior scan. The brightness and contrast tool allows the user to adjust the brightness and contrast of the image before it is actually scanned (Fig 5). After the image is previewed, a thumbnail image (a small low-resolution image) will appear in the scanning window. The user can adjust the brightness and contrast of the image to closely approximate the original image. The color balance tool allows the user to adjust the color of the scanned image in the preview mode. This function usually has sliders or dials for changing the color of the scan. For example, if the scan is too red, the red in the color balance window can simply be lowered. The crop tool allows the user to place a crop box or crop marks around the image or part of an image so that the whole scanning window, page, or film does not become part of the scanned image. If unwanted data are cropped out, the final saved scan will have a smaller file size.
|
The scanned image should be saved as a .tif file (.tif is a file extension, and all file names should include a file extension, placed after the name of the file [eg, TUMOR_SLIDE.tif]). The file extension .tif represents TIFF (tagged image file format), which is a file type used to save graphic images. This file type is uncompressed and readily acceptable in graphics software programs such as Photoshop, PowerPoint (Microsoft), and many others.
Another popular option for saving scanned images is the JPEG format (file extension .jpg). However, we do not recommend saving scans as JPEG files. JPEG is a compression format that compresses the size of the image file but also reduces the quality of the image. A user will most likely open scanned images in Photoshop to edit them and then save them again as JPEG files. Each time a JPEG file is saved again as a JPEG file, it further compresses the image and degrades the quality. If the user needs to save an image as a JPEG file, he or she should wait until the image is edited in Photoshop and then save it once in JPEG format. The JPEG format is a good choice if a very small file size is needed, such as in Web graphics and PowerPoint presentations. The JPEG file compression reduces the file size.
Other file types accepted by Photoshop are Photoshop Document (file extension .psd) and PICT (file extension .pct). The Photoshop Document (PSD) file format does not compress an image, and it supports all embedded Photoshop information. PICT is a compression format that actually breaks the image down into specific colors or palettes. A PICT file can display an image you produced that uses thousands (or millions) of colors and display it as 256, 32, or 16 colors. PICT files are often used in CD-ROM multimedia presentations that use a limited 256-color palette. This limited palette lowers the file size and increases loading speed.
Step 2: Correcting the Image
Photoshop can be used for all image correction, adjustment, and manipulation after the scanning stage is complete (Fig 6). Photoshop is the industry standard image manipulation and painting program available for Macintosh and Windows-based computers. The specialized tools of the program allow the user to manipulate pixels with ease (Fig 7). In this article, the basic techniques for image manipulation are described and illustrated in terms of the Macintosh Photoshop software. Capitalization or italics are used for menu items and keyboard shortcuts.
|
|
|
|
Rotating and Cropping the Image.— After a scanned image has been opened, the user may notice that it is upside down, reversed (transparency, slide, or negative only), or crooked or that it needs to be cropped.
To rotate or flip an upside down or sideways image, go to the desktop and select Image to display the Image command menu (Fig 9). Select Rotate Canvas and select either 90° or 180° to rotate the image. If a transparent image has been scanned from the wrong side and is reversed, select either Flip Horizontal or Flip Vertical from the Rotate Canvas menu. If the image is not on the page straight, select the Measure tool (shift I) from the Tools palette. Click and drag this tool along the crooked edge of the image that needs to be 90°. Then, return to the Rotate Canvas menu and select Arbitrary. There will be a preset, but editable number in the display; leave this number as it is and click OK (Fig 9).
|
|
|
Correcting Color and Contrast.— The Image command menu contains functions that allow the user to adjust the brightness, contrast, and color of an image. To change the brightness or contrast, go to the Image menu and select Adjust to choose and display the Brightness/Contrast dialog box (Fig 10). Place the cursor on the sliders and move them to correct the brightness and contrast values of the image. To adjust the color balance, return to the Adjust menu and select Color Balance to display its dialog box (Fig 11). This tool allows the user to correct the color in the image. The user can change each color independently, as well as choose to adjust the color of the shadow, highlights, and midtones independently. This tool will not work if the image is in gray-scale mode.
|
|
Removing Unwanted Marks and Data.— The image may contain dust, scratches, or data such as patient information that must be removed. The Paintbrush and Rubber Stamp tools are two commonly used tools for removing unwanted marks.
To use the Paintbrush tool, go to the Tools palette, find the Measure tool, click on it and press Shift I to scroll through the tool options. Select the Eyedropper tool (I) and click with this tool directly on the image value or color with which you wish to paint. The Eyedropper tool will select the color from the image. Next, select the Paintbrush tool (B) and click and drag with the mouse or stylus tool to paint with the brush over the unwanted material.
The Rubber Stamp tool allows the user to remove text or marks that lie over the radiologic image by selecting the color and texture in one area and copying it to another area. Go to the Tools palette and select the Rubber Stamp tool (S). Pick a desired brush size from the tools option bar at the top of the desktop and place the brush over an area with the same value and texture as the area being replaced. Hold down the option key (Macintosh) or the alt key (PC) to select the texture directly from the image. Next, use the brush to paint with the selected texture over the unwanted material (Photoshop actually copies the texture and places it where you click). The brush size, hardness, shape, and opacity can all be edited within the tools options bar, which is displayed automatically across the top of the monitor.
Resizing the Image.— The size and resolution of the image can be changed with this function. The final use of the image will dictate the dimensions and the resolution of the image. To adjust image size, go to the Image menu and select Image Size to display a dialog box. The dialog box allows the user to enter the exact numerical measurements to resize the image (Fig 12).
|
Labeling and Adding Arrows.— The Text and Line tools allow the user to create text and arrows in any color and move them around freely without affecting the underlying image. To add a label, select the Text tool (T) from the Tools palette and click on the image. A flashing cursor will appear where you have clicked. Next, type text or paste text that was copied from an outside source. To edit the font size, font type, or color of the text, go to the Text tool options menu at the top of the desktop and select the desired attributes to change. To close the text box, press command return (Macintosh) or alt return (PC) (Fig 13).
|
|
Step 4: Saving the Image
Images that have been manipulated in Photoshop need to be saved in Photoshop after all changes have been made. The future use of the image dictates the file format used to save the Photoshop image.
If the user wishes to save all lines, arrows, and text information on separate layers for future editing, he or she should save the image as a Photoshop document (file extension .psd). All other file formats flatten the text and arrow layers and combine the text and radiologic data on one layer (5). Selecting the TIFF file format will save photographic images at full resolution without compression and will flatten all Photoshop layer information. If the user no longer needs labels and arrows on a separate layer, use of a TIFF format is ideal. Most print shops and slide printing facilities require TIFF files. Selecting the JPEG format will flatten the layer information and compress the image. JPEG files are an ideal compression format for Web use, PowerPoint use, and storing or archiving many large files.
There are many types of storage available with varying capacity to hold numerous high-resolution radiologic images. A single gray-scale, 5 x 7-inch, 300-ppi image saved as a TIFF file is roughly 3 Mbytes. A single RGB image with the same dimensions, resolution, and file type is roughly 9 Mbytes. These are large files and large-capacity storage devices are needed to store these type of images. Many new computers come with large internal hard drives that have more than 24 Gbytes of storage space. Another large-capacity device available is an external hard drive. Many external peripheral devices are available and can hold upward of 48 Gbytes. Other storage options that allow for mobility are Zip disks and Jaz disks. These disks usually use an external drive and store 100 Mbytes and 1 Gbyte, respectively. CD-R disks hold 650–870 Mbytes and use an internal or external CD-ROM writing device. The DVD R disks hold roughly 4.5 Gbytes of data and use an internal or external writing device.
Step 5: Producing the Final Output
The final display of radiologic images may vary. They can be used for print distribution in journals and posters, computer slide presentations, traditional slide presentations, or Web-based presentations.
To produce glossy photographic prints, go to the Image command menu and select Image Size to open its dialog box. Resize the images to 5 x 7 inches at 300 ppi to print these images. Most radiology journals ask for glossy 5 x 7-inch prints, and 300 ppi is the optimal resolution for high-quality photographic prints and will produce the best printed image. This resolution also uses more disk space than a lower resolution image. Users can experiment with resolution to find the best compromise between the quality and file size that suits their needs.
To produce traditional slides, return to the Image Size dialog box. Resize image dimensions to 6 x 9 inches and set the resolution to 150–300 ppi.
As previously discussed, images intended for computer display require only 72 ppi. To use the image in a PowerPoint multimedia presentation, go to the Image command menu and select Image Size to open its dialog box. Resize the image to 6 x 9 inches and 72 ppi. To create Web graphics, go to the Image Size dialog box and resize the image dimensions to the desired size and set the resolution to 72 ppi.
|
Acceptable Manipulation of a Radiologic Image |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
|
Conclusion |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
|
Footnotes |
|---|
See also the article by Caruso and Postel (pp 993–1002) in this issue.
|
References |
|---|
|
TopAbstractIntroductionSystem RequirementsImage Digitization and...Acceptable Manipulation of a...ConclusionReferences |
|---|
Related Article
This article has been cited by other articles:
|
|
 |
|
  C.-S. Yam, J. Kruskal, and M. Larson Creating Animated GIF Files for Electronic Presentations Using Photoshop Am. J. Roentgenol., May 1, 2007; 188(5): W485 - W490. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Hoa, A. Micheau, and G. Gahide Creating an Interactive Web-based e-Learning Course: A Practical Introduction for Radiologists RadioGraphics, November 1, 2006; 26(6): e25 - e25. [Abstract] [Full Text]
|
|
|
|
|
|
A. G. Ryan, L. J. Louis, and W. C. Yee Informatics in Radiology (infoRAD): HTML and Web Site Design for the Radiologist: A Primer RadioGraphics, July 1, 2005; 25(4): 1101 - 1118. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Lababede Digital Image Editing Using PowerPoint: Part 1, Introduction to the Image-Manipulation Commands Am. J. Roentgenol., September 1, 2004; 183(3): 847 - 851. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Lababede Digital Image Editing Using PowerPoint: Part 2, Practical Applications of the Image-Manipulation Commands Am. J. Roentgenol., September 1, 2004; 183(3): 853 - 858. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Sistrom and J. Honeyman-Buck A Simple Method for Importing Multiple Image Files into PowerPoint Am. J. Roentgenol., June 1, 2004; 182(6): 1591 - 1596. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Haider Extending PowerPoint with DICOM Image Support RadioGraphics, November 1, 2003; 23(6): 1683 - 1687. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Lababede Digital Image Manipulation RadioGraphics, September 1, 2003; 23(5): 1338 - 1340. [Full Text] [PDF]
|
|
|
|
|
|
E. J. Escott and D. Rubinstein Free DICOM Image Viewing and Processing Software for Your Desktop Computer: What's Available and What It Can Do for You RadioGraphics, September 1, 2003; 23(5): 1341 - 1357. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. A. Taylor Sharpening the Image Am. J. Roentgenol., July 1, 2003; 181(1): 43 - 45. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| RADIOGRAPHICS | RADIOLOGY | RSNA JOURNALS ONLINE |
