Characteristics of extrafocal radiation and its potential significance in pediatric radiology.

Thomas, Sylvia; Freshcorn, John E.; Krugh, K B; Henry, Gary C.; Kereiakes, J G; Kaufman, Robert A.

doi:10.1148/radiology.146.3.6828695

Cited by 4 publications

(1 citation statement)

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“…13-15͒ and decreases sharply below 60 kVp. 14 We therefore recommend the use of the lowest available kVp setting for the measurement of r. A 40 kVp setting is available on most radiographic systems. However, extrafocal radiation can still comprise as much as 5% of the total x-ray energy fluence at 40 kVp.…”

Section: Iiia Sensitivity To F 1 F 2 and Kvpmentioning

confidence: 99%

Nondestructive measurement of the grid ratio using a single image

Pasciak

Jones

2009

Medical Physics

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The antiscatter grid is an essential part of modern radiographic systems. Since the introduction of the antiscatter grid, however, there have been few methods proposed for acceptance testing and verification of manufacturer-supplied grid specifications. The grid ratio ͑r͒ is an important parameter describing the antiscatter grid because it affects many other grid quality metrics, such as the contrast improvement ratio ͑K͒, primary transmission ͑T p ͒, and scatter transmission ͑T s ͒. Also, the grid ratio in large part determines the primary clinical use of the grid. To this end, the authors present a technique for the nondestructive measurement of the grid ratio of antiscatter grids. They derived an equation that can be used to calculate the grid ratio from a single off-focus flat field image by exploiting the relationship between grid cutoff and off-focus distance. The calculation can be performed by hand or with included analysis software. They calculated the grid ratios of several different grids throughout the institution, and afterward they destructively measured the grid ratio of a nominal r8 grid previously evaluated with the method. They also studied the sensitivity of the method to technical factors and choice of parameters. With one exception, the results for the grids found in the institution were in agreement with the manufacturer's specifications and international standards. The nondestructive evaluation of the r8 grid indicated a ratio of 7.3, while the destructive measurement indicated a ratio of 7.53Ϯ 0.28. Repeated evaluations of the same grid yielded consistent results. The technique provides the medical physicist with a new tool for quantitative evaluation of the grid ratio, an important grid performance criterion. The method is robust and repeatable when appropriate choices of technical factors and other parameters are made.

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Section: Iiia Sensitivity To F 1 F 2 and Kvpmentioning

confidence: 99%

Nondestructive measurement of the grid ratio using a single image

Pasciak

Jones

2009

Medical Physics

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The influence of lead thyroid collars on cephalometric landmark identification

Wiechmann

Decker²,

Hohoff

et al. 2007

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, an

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Measurement of extrafocal radiation by computed radiography

Miettunen

1992

The British Journal of Radiology

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Measurement of radiation differences from image data is made possible by computed radiography (CR) based on storage phosphor imaging plates. The photostimulable luminescence (PSL) response is linear in a range greater than four orders of magnitude. Pinhole radiographs of focal and extrafocal radiation obtained by CR were quantitatively analysed using the technique originally introduced in recent scatter studies. No films or hard copies were used in the analysis. The material consisted of 54 images for measurement of the focal peak intensity, and a corresponding set of 54 images obtained at a 250 times greater operating sensitivity for the imaging of the extrafocal emission. The extrafocal-to-focal emission ratio was in the range of 0.001-0.006 depending on the off-focus distance. Because of the relatively large area of origin, exposure resulting from extrafocal radiation is estimated to reach up to 20% of the total radiation dosage. The results are in agreement with previous reports using other techniques and show that CR can also be used in a quantitative manner in this kind of comparative measurement.

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Characteristics of extrafocal radiation and its potential significance in pediatric radiology.

Cited by 4 publications

References 0 publications

Nondestructive measurement of the grid ratio using a single image

Nondestructive measurement of the grid ratio using a single image

The influence of lead thyroid collars on cephalometric landmark identification

Measurement of extrafocal radiation by computed radiography

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