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Titolo:
SLIT CAMERA FOCAL SPOT MEASUREMENT ERRORS IN MAMMOGRAPHY
Autore:
TANG S; BARNES GT; TANNER RL;
Indirizzi:
SUNY HLTH SCI CTR,DEPT RADIOL,RADIAT PHYS SECT BROOKLYN NY 11203 UNIV ALABAMA HOSP & CLIN,DEPT RADIOL BIRMINGHAM AL 35233 UNIV TENNESSEE,MED CTR,DEPT RADIOL MEMPHIS TN 38163
Titolo Testata:
Medical physics
fascicolo: 11, volume: 22, anno: 1995,
parte:, 1
pagine: 1803 - 1814
SICI:
0094-2405(1995)22:11<1803:SCFSME>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Keywords:
FOCAL SPOT MEASUREMENT; MAMMOGRAPHY EQUIPMENT; SLIT CAMERA FOCAL SPOT MEASUREMENT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
9
Recensione:
Indirizzi per estratti:
Citazione:
S. Tang et al., "SLIT CAMERA FOCAL SPOT MEASUREMENT ERRORS IN MAMMOGRAPHY", Medical physics, 22(11), 1995, pp. 1803-1814

Abstract

Mammography x-ray tube focal spot sizes are routinely measured duringacceptance testing and annual performance audits. The National Electrical Manufacturers Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen-film imagereceptors, microscope magnification and reticule accuracy, and observer variation on slit camera focal spot measurements. Our results indicate that small rotational misalignment (<5 degrees) and tilt misalignment (<3 degrees) introduce insignificant error. Measured focal spot size increased slightly with image optical density, indicating that for consistent results the image optical density variations should be minimized. Also desirable for accurate field measurements is a high power microscope (25-50X) and a reticule with divisions of less than or equal to 0.02 mm. Screen-film imaging consistently resulted in a slightly smaller measured focal spot size than direct film. The greatest sourceof error was due to observer variation. Of interest is that reader variability showed a consistent pattern and variation between two measurements by the same observer was much smaller than between observer variation, suggesting that standardized criteria should be established and a method of reader training developed. The length of the focal spot is defined at a reference axis angle specified by the mammography unitmanufacturer. Presented is a tabulation of the focal spot geometry and reference axis angles for the majority of mammography units currently and recently marketed in North America.

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Documento generato il 15/07/20 alle ore 07:59:41