Paul Fisher

Impact of image size on effectiveness of digital imaging systems

Radiologists detect small diagnostic signals in radiographic film images by altering the distance between the eye and the image, effectively zooming in on a particular detail. Details thus enlarged are more perceptible to the viewer. Considering that conventional film images are nearly life-size, the potential for increasing the detection of small signals in this manner is high. Digital images, however, presented in video format are usually smaller than life-size, sometimes more than 50% smaller. While local enlargements using computer-based imaging systems are extremely useful, the radiologist cannot examine a whole, life-size image. The importance of the latter in the diagnostic process is revealed in detection studies using the same images of a chest phantom with small nodular inclusions, in different size formats. A clear positive correlation exists between overall image size and the detection of signals that are of a diagnostically-relevant size. While it is widely accepted that image fidelity is an important determinant in the clinical acceptability of digital radiography, digital image displays should also be large enough to display life-size images.

Digital image display station performance requirements based on physician experience with a prototype system

The authors report on observations of, and interviews with, physicians using a prototype digital image display and reporting station. While the users generally agree that image quality is clinically satisfactory they are unanimous in their opinion that improvements in the man-machine interface are required before case review by this mechanism is clinically acceptable in a production environment. A model image and information user interface is presented. It was developed in answer to the needs of radiologists and referring physicians operating in the imaging department of a community acute care facility. In such an environment images and related information must be communicated quickly and often simultaneously to different parts of the department and hospital. The user interface to the management system and the management system itself must address the varied functions and the needs of both the medical and clerical staff that perform them. Image enhancement processes, for example, must be restricted to those which quickly provide significantly more perceivable diagnostic information. Little used processes that may occupy significant portions of the display and the consoles computing power must be trimmed or eliminated.

Signal detection in digital chest-phantom images acquired with an image intensifier

Signal detection performance was evaluated on the basis of ROC analysis using both digital and conventional images of a humanoid chest phantom. Simulated focal (coin) lesions were the target pathology. Digital images were acquired using a 57-cm image intensifier, digitized to 1024×1024×10 bits, and compared, in both video and laser-printed film formats, with conventional 14×17-inch chest films. Signal detection using digital video and laser printed images, of the same image polarity as conventional images, was found not to differ significantly from that achieved using conventional images, despite the smaller size of the digital images.

Digital image display station performance requirements based on physician experience with a prototype system.

The authors report on observations of and interviews with physicians using a prototype digital image display and reporting station. While the users generally agree that image quality is clinically satisfactory, they are unanimous in their opinion that improvements in the man-machine interface are required before case review by this mechanism is clinically acceptable in a production environment. A model image and information user interface is presented. It was developed in answer to the needs of radiologists and referring physicians operating in the imaging department of a community acute-care facility. In such an environment images and related information must be communicated quickly and often simultaneously to different parts of the department and hospital. The user interface with the management system and the management system itself must address the varied functions and the needs of both the medical and clerical staff. Image enhancement processes, for example, must be restricted to those that quickly provide significantly more perceivable diagnostic information. Little-used processes that may occupy significant portions of the display and the console’s computing power must be trimmed or eliminated.

Performance of a partial PACS and its application to the development of a fully integrated digital medical imaging department in a community hospital

Victoria General Hospital, which is a part of the Greater Victoria Hospital Society, is a 443 bed community hospital with a full-service medical imaging department that includes MRI. In August 1987, four rooms (chest radiography, GI fluorography, CT, and cardiac angiography) were connected to a Picture Archive and Communications System (PACS). We present the experience gained from two years of study with this prototype PACS and briefly describe its hardware and software configuration. Reported in detail is the measured image transfer performance of the PACS for each of the four image sources. Conventional films require more than 150 seconds from exposure to film availability for reporting. Using PACS, chest and GI images take 77 seconds per image from exposure to viewing, 31 secs for CT, and 40 secs for general angiography. The elapsed times with PACS between the various software processes for each modality, and those needed to set up image archive folders are detailed. The present imaging equipment at VGH, a typical community hospital, is specified and is to be integrated into a department-wide PACS. Required PACS performance levels relative to the clinical demands are described, and compared with the current PACS. The information and experience acquired by testing the VGH PACS has been used in the planning of the full implementation of PACS at VGH (ref. 10. Fisher et al). The next phase (3C) of PACS implementation is described.

Comprehensive computerized medical imaging: interim hypothetical economic evaluation

The 422-bed Victoria General Hospital (VGH) and Siemens Electric Limited have since 1983 been piloting the implementation of comprehensive computerized medical imaging, including digital acquisition of diagnostic images, in British Columbia. Although full PACS is not yet in place at VGH, experience to date habeen used to project annual cost figures (including capital replacement) for a fully-computerized department. The resulting economic evaluation has been labelled hypothetical to emphasize that some key cost components were estimated rather than observed; this paper presents updated cost figures based on recent revisions to proposed departmental equipment configuration which raised the cost of conventional imaging equipment by

Digital Chest Imaging Using a 57-cm Image Intensifier: A Receiver-Operating Characteristic Study of User Performance

0.3 million* and lowered the cost of computerized imaging equipment by

Digital Radiography of the Wrist Using a 33 cm Image Intensifier

0.8 million. Compared with conventional diagnostic imaging, computerized imaging appears to raise overall annual costs at VGH by nearly

Interfacing a radiology information system and a picture archiving and communication system

0.7 million, or 11.6%; this is more favourable than the previous results, which indicated extra annual costs of

Evaluation of a generic RIS-PACS interface

1 million (16.9%). Sensitivity analysis still indicates that all reasonable changes in the underlying assumptions result in higher costs for computerized imaging than for conventional imaging. Computerized imaging offers lower radiation exposure to patients, shorter waiting times, and other potential advantages, but as yet the price of obtaining these benefits remains substantial.