title: Feasibility of reduced-dose three-dimensional/four-dimensional-digital subtraction angiogram using a weighted edge preserving filter.
abstract: A conventional three-dimensional/four-dimensional (3D/4D) digital subtraction angiogram (DSA) requires two rotational acquisitions (mask and fill) to compute the log-subtracted projections that are used to reconstruct a 3D/4D volume. Since all of the vascular information is contained in the fill acquisition, it is hypothesized that it is possible to reduce the x-ray dose of the mask acquisition substantially and still obtain subtracted projections adequate to reconstruct a 3D/4D volume with noise level comparable to a full-dose acquisition. A full-dose mask and fill acquisition were acquired from a clinical study to provide a known full-dose reference reconstruction. Gaussian noise was added to the mask acquisition to simulate a mask acquisition acquired at 10% relative dose. Noise in the low-dose mask projections was reduced with a weighted edge preserving filter designed to preserve bony edges while suppressing noise. Two-dimensional (2D) log-subtracted projections were computed from the filtered low-dose mask and full-dose fill projections, and then 3D/4D-DSA reconstruction algorithms were applied. Additional bilateral filtering was applied to the 3D volumes. The signal-to-noise ratio measured in the filtered 3D/4D-DSA volumes was compared to the full-dose case. The average ratio of filtered low-dose SNR to full-dose SNR was 0.856 for the 3D-DSA and 0.849 for the 4D-DSA, indicating that the method is a feasible approach to restoring SNR in DSA scans acquired with a low-dose mask. The method was also tested in a phantom study with full-dose fill and 22%-dose mask.
authors.affiliation: University of Wisconsin-Madison , Department of Biomedical Engineering, 1415 Engineering Drive, Madison, Wisconsin 53706, United States.
authors.forename: Erick L
authors.initials: EL
authors.lastname: Oberstar
authors.affiliation: University of Wisconsin-Madison, Department of Medical Physics, 1111 Highland Avenue #1005, Madison, Wisconsin 53705, United States; University of Wisconsin-Madison, Department of Medicine, 1685 Highland Avenue, Madison, Wisconsin 53792, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Speidel
authors.affiliation: University of Wisconsin-Madison , Department of Biomedical Engineering, 1415 Engineering Drive, Madison, Wisconsin 53706, United States.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Davis
authors.affiliation: University of Wisconsin-Madison , Department of Radiology, 600 Highland Avenue, Madison, Wisconsin 53792, United States.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Strother
authors.affiliation: University of Wisconsin-Madison, Department of Biomedical Engineering, 1415 Engineering Drive, Madison, Wisconsin 53706, United States; University of Wisconsin-Madison, Department of Medical Physics, 1111 Highland Avenue #1005, Madison, Wisconsin 53705, United States; University of Wisconsin-Madison, Department of Radiology, 600 Highland Avenue, Madison, Wisconsin 53792, United States.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Mistretta
keywords: digital subtraction angiogram; dose reduction; edge preservation; four-dimensional; noise estimation; reconstruction artifacts; signal to noise ratio; three-dimensional bilateral filtering