A H Sobel | PubMed Health

PubMed1997

Processes involved in reading imaging studies: workflow analysis and implications for workstation development.

Software development for imaging workstations has lagged behind hardware availability. To guide development and to analyze work flow involved in interpretation of cross-sectional imaging studies, we assessed the cognitive and physical processes. We observed the performance and interpretation of body computed tomography (CT) scans and recorded the events that occurred during this process. We studied work flow using a bottleneck analysis. Twenty-four of a total of 54 cases (44%) involved comparing the images with those of prior scans. Forty-seven of 54 scans (87%) were viewed using windows other than soft tissue, or compared with precontrast scans. In 46 cases (85%), the interpretation stopped to return to a previous level for review. Measurement of lesions was performed in 24 of 54 (44%) cases, and in 15 (63%) of these cases, measurements were taken of lesions on old studies for comparison. Interpretation was interrupted in 14 of 54 cases (26%) by referring clinicians desiring consultation. The work flow analysis showed film folder retrieval by the film room to be the bottleneck for interpretation by film. For picture archiving and communication system (PACS) reading, the CT examination itself proved to be the bottleneck. We conclude that workstations for CT interpretation should facilitate movement within scans, comparison with prior examinations, and measuring lesions on these scans. Workstation design should consider means of optimizing time currently not used between interpretation sessions, minimizing interruptions and providing more automated functions currently requiring physician interaction.

Cross-Sectional Studies↗

PubMed1997

Accuracy and precision of CT angiography in a model of carotid artery bifurcation stenosis.

PURPOSE: To determine optimal acquisition parameters and measurement techniques for CT angiography of the carotid bifurcation. METHODS: Anatomic phantoms were created in which the diameter of the carotid artery stenoses ranged from 15% to 95%. Initially, we compared the accuracy of stenosis determination obtained by using various values of section collimation and table pitch. Subsequently, applying the combination of collimation and pitch that yielded the greatest longitudinal coverage without degradation in accuracy, we compared the accuracy of measurements performed with various display algorithms, including axial, magnified axial, maximum intensity projection (MIP), and shaded surface display (SSD) images. Last, we determined the effect on accuracy of varying both window and level settings. The standard of reference for all measurements was considered to be caliper measurements made of the models at the time of their construction. RESULTS: CT angiography was highly accurate for determining the percentage of stenosis; the average difference between CT angiographic measurements and the standard of reference was less than 1% for all parameter combinations and measurement techniques. Precision varied among the measurement techniques. Magnified axial images provided more precise measurements than either the MIP or SSD images. Although there was a trend toward improved precision with the use of magnified versus unmagnified axial images and MIP versus SSD images, neither of these comparisons reached statistical significance. Systematic error was produced by changing the level setting from that halfway between the luminal density and vessel wall density. Random error was introduced by using window settings greater than zero. CONCLUSION: CT angiography was highly accurate and precise for determining percentage of stenosis. The highest precision was attained by using magnified axial images with the level halfway between luminal density and vessel wall density and with the window set to zero.

Carotid Arteries↗