Department of Animal Health, Smithsonian National Zoological Park, Washington, DC, USA
Digital radiography consists of two different technologies: computed radiography (CR) and direct digital radiography (DR). Although the two systems produce equal images, DR does not require cassettes or plates so it can be three times quicker than CR. This reduced processing time shortens anesthesia times. However, DR can be up to $25,000 more expensive than CR depending on the brand, model and options chosen.
In August 2005, this institution converted from a traditional radiography system (300HF Generator AMRAD Classic ST Stationary Table System) to a CR system donated by Fujifilm Medical Systems USA, which is used with the pre-existent machine. It consists of:
1. The SmartCR unit with a compact reader unit for imaging plate scanning and erasure (FCR XG4)
2. The flash image and information processor console (Flash Lite IIP console) for patient ID, image preview, reprocessing and transmission for communication and archiving (PACS)
3. Barcode reader
4. 15” flat panel LCD display (1024 × 768)
5. Fuji type C cassettes.
Most of the unit is located within the radiology suite and allows for a variety of image manipulations, including adjustment of brightness and contrast, magnification, inverting black and white and cropping of images. The workstation (Flash Lite IIP) is located in the adjacent treatment room and houses the central software (Synapse® 3.0-veterinary-specific PACS) where the patient database entry (accession number, species, name, primary clinician, body part imaged) is performed before the radiographic study is completed. The workstation has two 15” high-resolution flat-panel LCD displays in vertical position so the primary clinician can review the images during the procedure. A second workstation, consisting of two 17” high-resolution flat-panel LCD displays in horizontal position, is located in the hospital’s conference room where images are reviewed and discussed by all the clinicians. A Fuji Medical Dry Imager (DRYPIX 3000) prints hard copies of the digital images, which are useful when technical problems with the computer system arise.
Since the acquisition of the new system until March 2006, over 320 clinical cases have been radiographed, with a minimum of two images for each study. CR has reduced retakes due to overexposure or slight underexposure by using the image-management software to adjust the overall image. Because of this feature, bone and soft tissue detail can be obtained in the same image. However, as it is not possible to adjust a markedly underexposed image without repeating the image, a consistent increase in radiograph exposure intensity has been observed in this practice. This approach is a disadvantage when compared to traditional radiography where potential radiation dose to the patient and personnel can be collimated and controlled.
Prior to CR acquisition, each imaging required 7 min. With CR, 5 min is needed for each view. Before the imaging study, it is necessary to enter the patient information into the software which requires less than 1 min. The time from radiograph exposure to display on screen for manipulation is approximately 45 sec. Printing the image takes 2 min 23 sec. This total time is considered acceptable because radiographic studies are typically performed at the beginning of the anesthesia.
Another obvious advantage of CR when compared with traditional radiography is elimination of stocking and purchase of chemical developers. The system is therefore more environmentally friendly with less chemical disposal and ultimately, more cost-efficient per film.
Digital storage of CR has allowed easy review, retrieval, transferability via email (.jpg images) to consultants and reproduction of images. Although with this system all the images for one case can be compared, this system it is not capable of comparing images from different individuals of the same species on one screen.
Computer radiography offers substantial advantages to traditional radiology technology in a zoo setting. Although considered older technology than DR, the CR system is more affordable and can be used with existing radiographic equipment, decreasing the budget to digitally convert from a traditional radiography system.