A Comparison of an Air Gap and a Grid in Roentgenography of the Chest

Ed, Trout; Jp, Kelley; Vl, Larson

doi:10.2214/ajr.124.3.404

Cited by 15 publications

(4 citation statements)

References 5 publications

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“…Suitable image quality could be produced from lower E at OID=0cm than at OID=15 and 30cm (Table 4). Although in agreement with other studies 5,30 , the findings from this study are in contradiction to Trout et al 27 , who suggested that images of similar quality can be produced at 0 and 15cm OIDs from the same E by adjusting SID to a long setting. This contradiction might be because those authors considered image contrast, rather than a visual scale, as a tool for identifying suitable image quality.Therefore, their conclusion is questionable, because they were not looking for diagnostic criteria in their image quality definition.…”

Section: Oid or Air Gapsupporting

confidence: 67%

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A systematic procedure to optimise dose and image quality for the measurement of inter-vertebral angles from lateral spinal projections using Cobb and superimposition methods

Qaroot

Hogg

Twiste

et al. 2014

Journal of X-Ray Science and Technology: Clinical Applications

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Background: Patients with vertebral column deformations are exposed to high risks associated with ionising radiation exposure. Risks are further increased due to the serial X-ray images that are needed to measure and asses their spinal deformation using Cobb or superimposition methods. Therefore, optimising such X-ray practice, via reducing dose whilst maintaining image quality, is a necessity.Objectives: With a specific focus on lateral thoraco-lumbar images for Cobb and superimposition measurements, this paper outlines a systematic procedure to the optimisation of X-ray practice.Methods: Optimisation was conducted based on suitable image quality from minimal dose. Image quality was appraised using a visual-analogue-rating-scale, and Monte-Carlo modelling was used for dose estimation. The optimised X-ray practice was identified by imaging healthy normal-weight male adult living human volunteers.Results: The optimised practice consisted of: anode towards the head, broad focus, no OID or grid, 80kVp, 32mAs and 130cm SID. Conclusion: Images of suitable quality for laterally assessing spinal conditions usingCobb or superimposition measurements were produced from an effective dose of 0.05mSv, which is 83% less than the average effective dose used in the UK for lateral thoracic/lumbar exposures. This optimisation procedure can be adopted and use for optimisation of other radiographic techniques.

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Section: Oid or Air Gapsupporting

confidence: 67%

“…OID=30cm. The latter 2 OIDs were chosen as they have been reported appropriate for vertebral column imaging 11,12,27 .…”

Section: Oid and Air Gapmentioning

confidence: 99%

A systematic procedure to optimise dose and image quality for the measurement of inter-vertebral angles from lateral spinal projections using Cobb and superimposition methods

Qaroot

Hogg

Twiste

et al. 2014

Journal of X-Ray Science and Technology: Clinical Applications

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“…Early studies on air gap methods concentrated on chest radiographs 12,13 . These studies indicate that images acquired with air gap technique can provide contrast similar to images acquired using conventional grids, in particular for the posterior–anterior projection 12 with no increase in the patient exposure.…”

Section: Introductionmentioning

confidence: 99%

Air gap technique is recommended in axiolateral hip radiographs

Kivistö

Kotiaho

Henner

et al. 2020

J Applied Clin Med Phys

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Purpose To investigate the replacement of conventional grid by air gap in axiolateral hip radiographs. The optimal air gap distance was studied with respect to radiation dose and image quality using phantom images, as well as 26 patient axiolateral hip radiographs. Methods The CDRAD phantom, along with polymethylmethacrylate slabs with thicknesses of 10.0, 14.6, and 20.0 cm was employed. The inverse image quality index and dose area product (DAP), as well as their combination, so called figure‐of‐merit (FOM) parameter, were evaluated for these images, with air gaps from 20 to 50 cm in increments of 10 cm. Images were compared to those acquired using a conventional grid utilized in hip radiography. Radiation dose was measured and kept constant at the surface of the detector by using a reference dosimeter. Verbal consent was asked from 26 patients to participate to the study. Air gap distances from 20 to 50 cm and tube current‐time products from 8 to 50 mAs were employed. Exposure index, DAP, as well as patient height and weight were recorded. Two radiologists evaluated the image quality of 26 hip axiolateral projection images on a 3‐point nondiagnostic — good/sufficiently good — too good scale. Source‐to‐image distance of 200 cm and peak tube voltage of 90 kVp were used in both studies. Results and conclusion Based on the phantom study, it is possible to reduce radiation dose by replacing conventional grid with air gap without compromising image quality. The optimal air gap distance appears to be 30 cm, based on the FOM analysis. Patient study corroborates this observation, as sufficiently good image quality was found in 24 of 26 patient radiographs, with 7 of 26 images obtained with 30 cm air gap. Thus, air gap method, with an air gap distance of 30 cm, is recommended in axiolateral hip radiography.

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“…The air gap technique is a common alternative to the grid method for high performance scatter rejection [1,4,[15][16][17][18][19][20]. Most works involving the air gap technique had been performed using comparatively small air gap distances such as 10 to 20 cm.…”

Section: Introductionmentioning

confidence: 99%

Scatter removal using modified air gap method: spectral composition technique

1993

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A new scatter rejection technique using the modified air gap method is presented. Two x-ray cassettes are used per exposure. One cassette (front cassette) was placed immediately behind the object. The other (back cassette) was positioned 60 cm behind the object. Thefront radiograph has good spatial resolution but includes a relatively large amount of scatter. The back radiograph has poor high frequency resolution but little scatter due to the air gap. The spectral composition technique extracts highfrequency informationfrom thefront radiograph and combines it with the lowfrequency information of the back radiograph to produce an improved composite synthesized image. No artifacts due to the spectral composition technique were observed. In the lung and heart regions, the modified air gap method resulted in comparable or superior scatter rejection performance as compared to the conventional grid technique.

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A Comparison of an Air Gap and a Grid in Roentgenography of the Chest

Cited by 15 publications

References 5 publications

A systematic procedure to optimise dose and image quality for the measurement of inter-vertebral angles from lateral spinal projections using Cobb and superimposition methods

A systematic procedure to optimise dose and image quality for the measurement of inter-vertebral angles from lateral spinal projections using Cobb and superimposition methods

Air gap technique is recommended in axiolateral hip radiographs

Scatter removal using modified air gap method: spectral composition technique

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