SU-GG-I-98: Using MTF to Assess the Influence of X-Ray Focal Spot Blur on the Resolution of Fluoroscopic Imaging Systems

Fetterly, Kenneth A.; Magnuson, Dixon J.; Hindal, Mark D.; Schueler, Beth A.

doi:10.1118/1.3468131

Cited by 2 publications

(3 citation statements)

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“…It is well known that, for focal spot size ∼1 mm, increased focal spot penumbral blur associated with increasing SID can adversely affect image quality (Rossmann 1970, Doi 1974, Fetterly et al 2010, Dance 2014, Dehairs et al 2020. This penumbral blur effect was not addressed herein but must be considered for practical application of these results to cine angiography imaging of adult patients.…”

Section: Discussionmentioning

confidence: 97%

Influence of anatomical structure on antiscatter grid performance in 2D: application to x-ray angiography and a prototype 29:1 ratio grid

Fetterly,

Bernhardt,

Schueler

2024

Phys. Med. Biol.

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Objective. The use of uniform phantoms to assess the influence of x-ray scatter and antiscatter grids on x-ray angiography and fluoroscopy image quality disregards the influence of spatially variable x-ray attenuation of patients. The purpose of this work was to measure scatter to primary ratio (SPR) and antiscatter grid SNR improvement factor (K SNR) using experimental conditions which better mimic patient imaging conditions. Approach. Three adult-sized anthropomorphic phantoms were used. AP and lateral projection images of the thorax and abdomen were acquired with and without an antiscatter grid. Grids with ratio 15:1 and 29:1 (r15, r29) and x-ray fields of view 20, 25 (thorax) and 32, 42 cm (abdomen) were tested. Combined with a-priori measurements of grid scatter and primary transmission fractions, these images were used to calculate 2D SPR and K SNR maps. Main results. Results demonstrated that measurements by uniform phantom do not describe the complex 2D SPR and K SNR distributions associated with anthropomorphic phantoms. The regions of the images with the lowest primary x-ray intensity (greatest attenuation) had the highest SPR and the highest K SNR attributable to the grids. Considering all conditions, the 95th percentile of the SPR maps was in the range 42%–185% greater than the median values and that of the K SNR maps was 4%–20% higher than the median values. The combined influences of SID 120 vs. 107 cm and r29 vs. r15 grid resulted in K SNR in the range 1.05–1.49. Significance. Performance of anti-scatter grids using anatomically complex phantoms highlights the substantial variation of SPR and K SNR within 2D images. Also, this work demonstrates the benefit of the prototype r29 grid for thoracic and abdominal angiography imaging conditions is substantial, especially for large patients and radiodense image regions.

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Section: Discussionmentioning

confidence: 97%

Influence of anatomical structure on antiscatter grid performance in 2D: application to x-ray angiography and a prototype 29:1 ratio grid

Fetterly,

Bernhardt,

Schueler

2024

Phys. Med. Biol.

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“…It is recognized that variable geometric magnification realized by changing SID affects x-ray system blur and spatial resolution (Fetterly et al 2010a, 2010b, Dehairs et al 2020. In this context, it may be anticipated that use of the large versus small focal spot and SID 120 cm versus 105 cm may result in penumbral blur which degrades image quality.…”

Section: Discussionmentioning

confidence: 99%

“…Previous work demonstrated that the median effective water equivalent thickness of adult patients undergoing invasive cardiac procedures was 28 cm (5th to 95th percentile 21-36 cm, max. 42 cm) (Fetterly et al 2010a(Fetterly et al , 2010b. Therefore, Plastic Water ® LR 15 keV-8 MeV (CIRS, Norfolk, VA) phantoms with area 30× 30 cm 2 and thickness in the range 20-44 cm (4 cm increments) were used to attenuate the primary beam and create scatter.…”

Section: Methodsmentioning

confidence: 99%

Technical evaluation of a prototype ratio 29:1 grid for adult patient cardiovascular angiography imaging conditions

et al. 2021

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The purpose of this work was to assess technical performance of a prototype high-ratio (r29), 80 line cm−1 grid for imaging conditions which mimic those for adult cardiovascular angiography. The standard equipment r15, 80 line cm−1 grid was used as a reference. Plastic Water® LR phantoms with thickness in the range 20–44 cm were used to simulate adult patient attenuation and scatter. Grids were tested using x-ray field of view 20 and 25 cm and x-ray source to detector distance (SID) 107 and 120 cm. The primary transmission fraction (TP ) was measured using both narrow beam geometry and a lead beam stop (BS) technique. Scatter transmission (TS ) was measured with the lead BS technique. The quantum signal to noise ratio improvement factor (K SNR) was used to describe relative grid performance. The experimental conditions required revised theory to assess grid performance. Theory to account for the detector glare and underestimation of scatter intensity by the lead BS method was developed. Also, novel K SNR theory was developed to allow direct comparison of two grids operated at different SID. Mean TP was modestly lower for the r29 versus r15 grid (0.69 versus 0.75). When tested under equivalent scatter condition, TS of the r29 grid was approximately ½ that of the r15 grid (0.18 versus 0.34). K SNR of the r29 grid at SID 120 cm compared to the r15 grid at SID 107 cm increased linearly with phantom thickness (range 1.0 to ∼1.16). Findings of this work indicate that the r29 grid used at SID 120 cm is expected to provide improved image quality (or reduced patient radiation dose) when compared to the r15 grid used at SID 107 cm for adult cardiovascular patients and that the potential benefit of the r29 grid increases with patient thickness >20 cm.

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SU-GG-I-98: Using MTF to Assess the Influence of X-Ray Focal Spot Blur on the Resolution of Fluoroscopic Imaging Systems

Cited by 2 publications

References 0 publications

Influence of anatomical structure on antiscatter grid performance in 2D: application to x-ray angiography and a prototype 29:1 ratio grid

Influence of anatomical structure on antiscatter grid performance in 2D: application to x-ray angiography and a prototype 29:1 ratio grid

Technical evaluation of a prototype ratio 29:1 grid for adult patient cardiovascular angiography imaging conditions

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