Practical mini-PACS based on a hybrid video and digital network.
The Department of Radiology of the Shinshu University Hospital is presently in the process of developing a new type of mini-PACS with a hybrid architecture consisting of a video and a digital image archiving network. The video block consists of a server station with a video write-once optical disk (LD) and three workstations which are connected to two ultrasound imaging devices and an MRI device. The video images from any of these imaging devices are transferred immediately onto an LD. The examiner can observe the archived images immediately without any interruption of the examination. The image transmission time, including the record and play-back, is within 3 s. The digital block consists of a personal computer server and various workstations linked to the ETHERNET. This digital system supports database management, and archives digital images. This prototype system was used for daily clinical examinations from February 1989 to January 1990 and 31,366 images from 1561 patients were stored on the video disk. This one year experience suggests that a hybrid mini-PACS system is practical for total image archiving when the image matrix is less than 512 x 512 and selected digital image archiving.
Liquid crystal displays for the evaluation of dental
We assessed whether dental x-ray images observed on a liquid crystal display (LCD) could be applied to diagnosis. A 13-inch TFT (thin film transistor) display was utilized in this study. Fifty x-ray films of radiographically diagnosed periapical lesions and fifty normal films were digitized at 300 DPI.These sample images were randomized and evaluated by five observers who compared them with the original films using a continuously distributed confidence rating method. The data were analyzed with a Receiver Operating Characteristics (ROC) analysis. The CRT images were evaluated in the similar way.The results showed no statistically significant differences between the original dental x-ray films, images on the TFT display and the CRT regarding the diagnosis of periapical lesions.We conclude that a TFT-type liquid display provides sufficient detail for the diagnostic observation of dental radiographs. Thus, such displays may be useful for dental clinics.
Compression of radiological images with 512, 1,024, and 2,048 matrices.
A comprehensive study was performed using the full-frame bit-allocation compression technique on 78 radiological images, including digitized radiographs, computed radiographs, and computed tomography images. Each radiograph was digitized to 2,048 X 2,048 X 10, 1,024 X 1,024 X 10, and 512 X 512 X 10 matrices, respectively, with a laser scanner. Five compression ratios were used to compress each image, and reconstructed images from each compressed data set were obtained. Altogether, the authors studied 842 images, including the original and compressed-reconstructed images and the images obtained from the difference between the original and the reconstructed images. The results indicate that acceptable compression ratios for 2,048, 1,024, and 512 matrices are 25:1, 20:1, and 10:1, respectively, based on a mean-square error of 0.02%.