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A real-time regional adaptive exposure method for saving dose-area product in x-ray fluoroscopy
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10.1118/1.4801908
/content/aapm/journal/medphys/40/5/10.1118/1.4801908
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/5/10.1118/1.4801908

Figures

Image of FIG. 1.
FIG. 1.

In a conventional system the image is formed by the projection of a single focal spot x-ray tube onto a large-area detector (left). In the SBDX system an image is formed by combining the projections of the multiple focal spots on a large-area x-ray tube onto a small detector (right).

Image of FIG. 2.
FIG. 2.

(a) Reconstructed image of the child-sized phantom acquired without adaptive exposure. (b) The detector-count matrix is calculated by integrating the detector counts for each collimator hole. The white outline in the count matrix image indicates the central region that was used to calculate the threshold. (c) The plot shows the integrated detector counts as function of the percentile (only taking collimator holes within the central region into account). The raw threshold is the value at the 30th percentile. (d) The plot shows how the rescan-dependent thresholds are related to the raw threshold. Lower and upper thresholds that are used in the hysteresis algorithm are also shown.

Image of FIG. 3.
FIG. 3.

Phantom family used in this study. The black phantom has an iodinated pig heart and is here shown with the additional fat layer (obese adult).

Image of FIG. 4.
FIG. 4.

Steps to calculate the noise array. The figure shows images for the child-sized phantom with standard acquisition (top row) and regional adaptive exposure (bottom row). (a) Reconstruction of one frame of the 100 frames taken for each mode. (b) The subtraction image is derived by subtracting two subsequent frames. For clarity we show here the normalized subtraction image that was derived by dividing by the sum of the two frames. (c) The regional noise matrix is derived by dividing the subtraction image into a grid of 15 × 15 pixel regions. For each region the mean is calculated and placed as an element in the noise matrix. (d) The noise array is derived from the noise matrix. The array consists of elements of the noise matrix that are sorted in descending order.

Image of FIG. 5.
FIG. 5.

Summary of the pediatric cases studied. For every case four plots are shown. Reconstructed image at isocenter without adaptive exposure (upper left) and with adaptive exposure (upper right). The white circles show the location of lowest performing regions (below the 5th percentile). Plot of the sorted noise array for the experiments with and without adaptive exposure (lower left). In addition the corrected (including regions below the 20th percentile) curve is shown. Exposure map used in the adaptive exposure experiments (lower right). White indicates eight rescans and black indicates 0 rescans; increasing gray levels indicate decreasing numbers of rescans.

Image of FIG. 6.
FIG. 6.

Summary of the adult cases studied. For every case four plots are shown. Reconstructed image at isocenter without adaptive exposure (upper left) and with adaptive exposure (upper right). The white circles show the location of lowest performing regions (below the 5th percentile). Plot of the sorted noise array for the experiments with and without adaptive exposure (lower left). In addition the corrected (including regions below the 20th percentile) curve is shown. Exposure map used in the adaptive exposure experiments (lower right). White indicates eight rescans and black indicates 0 rescans; increasing gray levels indicate decreasing numbers of rescans.

Image of FIG. 7.
FIG. 7.

Comparison of dose savings for the eight cases studied. Black indicates the measured dose saving and the white and gray bars show the dose saving after the data were corrected to include regions below the 10th, 20th, and 30th percentiles.

Image of FIG. 8.
FIG. 8.

Dose savings corrected at the 20th percentile level for different reconstruction heights (at isocenter and ±5 cm from isocenter).

Tables

Generic image for table
TABLE I.

Summary of phantom and exposure parameters.

Generic image for table
TABLE II.

Summary of results obtained in the eight cases studied.

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/content/aapm/journal/medphys/40/5/10.1118/1.4801908
2013-04-24
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A real-time regional adaptive exposure method for saving dose-area product in x-ray fluoroscopy
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/5/10.1118/1.4801908
10.1118/1.4801908
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