Our aim was to evaluate if there is a benefit in diagnostic accuracy and efficiency of viewing breast tomosynthesis (BT)
image volumes presented horizontally oriented, but also to evaluate the use of a systematic search strategy where the
breast is divided, and analyzed consecutively, into two sections. These image presentations were compared to regular
vertical image presentation. All methods were investigated using viewing procedures consisting of free scroll volume
browsing, and a combination of initial cine loops at three different frame rates (9, 14, 25 fps) terminated upon request
followed by free scroll volume browsing if needed. Fifty-five normal BT image volumes in MLO view were collected.
In these, simulated lesions (20 masses and 20 clusters of microcalcifications) were randomly inserted, creating four
unique image sets for each procedure. Four readers interpreted the cases in a random order. Their task was to locate the
lesions, mark and assign a five level confidence scale. The diagnostic accuracy was analyzed using Jackknife Free
Receiver Operating Characteristics (JAFROC). Time efficiency and visual search behavior were also investigated using
eye tracking. Results indicate there was no statistically significant difference in JAFROC FOM between the different
image presentations, although visual search was more time efficient when viewing horizontally oriented image volumes
in medium cine loops.
The purpose of this study was to evaluate four different viewing procedures as part of improving viewing conditions of
breast tomosynthesis (BT) image volumes. The procedures consisted of free scroll volume browsing, and a combination
of initial cine loops at three different frame rates (9, 14 and 25 fps) terminated upon request followed by free scroll
volume browsing. Fifty-five normal BT image volumes in MLO view were collected. In these, simulated lesions (20
masses and 20 clusters of microcalcifications) were randomly inserted, creating four unique image sets for each
procedure. Four readers interpreted the cases in a random order. Their task was to locate a lesion, mark and assign a five
level confidence scale. The diagnostic accuracy was analyzed using Jackknife Free Receiver Operating Characteristics
(JAFROC). Time efficiency and visual search behavior were also investigated using eye tracking. The results indicate
that there was no statistically significant difference in JAFROC FOM between the different viewing procedures,
however the medium cine loop speed seemed to be the preferred viewing procedure in terms of total analyze time and
dwell time.
Earlier studies have shown that while free-viewing images people tend to gaze at regions with a high local density of bottom up features such as contrast and edge density. In particular, this tendency seems to be more emphasized during the first few fixations after image onset. In this paper, we present a new method to investigate how gaze locations are chosen by introducing varying image resolution, and measure how it affects eye-movement behavior during free viewing. Results show that gaze density overall is shifted toward regions presented in high resolution over those degraded in resolution. However, certain image regions seem to attract early fixations regardless of display resolution. These results suggest that top-down control of gaze guidance may be the dominant factor early in visual processing.
Gaze coordinates are recorded from naive subjects watching a number of video clips. These are used to derive volumes of interest (VOIs) representing the mutual visual interest of the tested subjects. Video frames are then processed in variable resolution contingent on the VOI shapes to produce off-line foveated video. We report on bit rate savings between 30 and 54% due to off-line foveation proir to encoding with H.264. Subjective tests with a new set of subjects showed that off-line foveation in two of the three tested video clips had a positive effect on the experienced quality compared to unfoveated videos compressed with the same quality factor. We conclude that, in disagreement with previous works, it is advantageous to use off-line foveation to improve the performance of current state-of-art video compression technology.
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