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Biomedical subjects

L Linetsky

Publications and source records attributed to L Linetsky.

5 recordsLinked to original sources
PubMed1993

Chest "gestalt" and detectability of lung lesions.

Image perception in chest radiography is thought to occur on two levels, (a) a fast global response based on learned templates ("gestalt") and, (b) a slower systematic scan process. The relative importance of "gestalt" on the detection of nodular lung cancers was studied by disturbing the "gestalt" through rotation of the radiograph but not actually diminishing the image content available for viewing. Sixty chest radiographs (20 normals, 21 with subtle lung cancers, 19 with obvious lung cancers) were presented to three readers in normal and abnormal (rotated randomly in 90 degree increments) orientation for varying durations (0.25 s, 1 s, 4 s and unlimited viewing time). The results indicate that the detectability of obvious and subtle lung lesions was degraded by the disturbed "gestalt" for both short and long viewing times. The readers did not significantly increase their unlimited viewing time when faced with rotated images (4.4 +/- 3.4 s) as opposed to non-rotated images (4.0 +/- 3.2 s). We conclude that the detection of lung lesions relies heavily on the chest "gestalt" and that systematic scanning cannot fully compensate for an impaired global response due to a disturbed "gestalt."

Humans↗
PubMed1988

Lung lesions: correlation between viewing time and detection.

The influence of viewing time on the detectability of subtle and obvious lung cancers was studied. Frontal chest radiographs of 40 patients with subtle cancers, 40 patients with obvious cancers, and 40 healthy control subjects were shown to four observers for four different viewing times (0.25 second, 1 second, 4 seconds, and unlimited time). Receiver operating characteristic analysis was used to compare the detectability of lesions. Performance was degraded as viewing time decreased. The true-positive fractions for subtle and obvious cancers were 30% and 70% at 0.25 second and 74% and 98% at unlimited viewing time, respectively, for a given false-positive fraction of 20%. Thus, even with unlimited viewing time, the false-negative fraction for subtle cancers was 26%. The difference in detectability between subtle and obvious lung cancers was exaggerated at 1.0 second compared with 4 seconds and unlimited viewing time. The following conclusions were reached: (a) a substantial proportion of subtle lung lesions are missed, even with unlimited viewing time; (b) a large proportion of obvious lung cancers are detected with flash viewing; (c) the detectability of lesions decreases considerably as viewing time becomes less than 4 seconds; and (d) differences in detectability are exaggerated by short viewing times.

False Negative Reactions↗
PubMed1988

Comparison of two screen-film combinations in contact and magnification mammography: detectability of microcalcifications.

A new dual-screen, dual-emulsion-film combination that allows a decrease in radiation dose of approximately 66% was compared with a widely used single-screen, single-emulsion-film system in contact and magnification mammography. Clustered microcalcifications randomly superimposed on a breast phantom were detected, and the location and number of individual calcifications were determined by four observers. The detectability of calcifications, determined with a receiver operating characteristic (ROC) analysis area, was 0.92 for magnification and 0.82 for contact mammography with the single-emulsion-film system, compared with 0.84 and 0.72, respectively, with the dual-emulsion-film system. More clusters were correctly located and more individual calcifications were counted with magnification than with contact mammography. The dual-emulsion-film system with the magnification technique performs as well as the single-emulsion-film system with the contact technique, while retaining a decrease in required dose of approximately 40%.

Breast Diseases↗
PubMed1987

Localization of breast lesions identified on only one mammographic view.

Occasionally, a breast lesion is visible in only one mammographic projection. A simplified method of using parallax in a dedicated mammographic system has been devised to locate accurately lesions that are not visible in two orthogonal projections. In eight patients, a parallax approach from essentially a single mammographic position was used to place a hookwire preoperatively at nonpalpable suspicious abnormalities detected by mammography. Needles were inserted parallel to the chest wall while the breast was compressed in the mammographic unit. In each case, the tissue containing the lesion was pierced by a needle chosen to be longer than the distance from the skin to the abnormality. Simple geometric ratios were used to determine the position of the lesion along the needle shaft after slightly changing the mammographic projection and viewing the needle obliquely. In all cases, this parallax approach permitted accurate localization of the lesion.

Breast Diseases↗