Comparison of entrance exposure and signal-to-noise ratio between an SBDX prototype and a wide-beam cardiac angiographic system

Abstract

The scanning-beam digital x-ray (SBDX) system uses an inverse geometry, narrow x-ray beam, and a 2-mm thick CdTe detector to improve the dose efficiency of the coronary angiographic procedure. Entrance exposure and large-area iodine signal-to-noise ratio (SNR) were measured with the SBDX prototype and compared to that of a clinical cardiac interventional system with image intensifier (II) and charge coupled device (CCD) camera (Philips H5000, MRC-200 x-ray tube, 72 kWp max). Phantoms were 18.6-35.0 cm acrylic with an iohexol-equivalent disk placed at midthickness (35 mg/cm2 iodine radiographic density). Imaging was performed at 15 frame/s, with the disk at mechanical isocenter and an 11-cm object-plane field width. The II/CCD system was operated in cine mode with automatic exposure control. With the SBDX prototype at maximum x-ray output (120 kVp, 24.3 kWp), the SBDX SNR was 107%-69% of the II/CCD SNR, depending on phantom thickness, and the SBDX entrance exposure rate was 10.7-9.3 R/min (9.4-8.2 cGy/min air kerma). For phantoms where an equal-kVp imaging comparison was possible (> or = 23.3 cm), the SBDX SNR ranged from 47% to 69% of the II/CCD SNR while delivering 6% to 9% of the II/CCD entrance exposure rate. From these measurements it was determined that the relative SBDX entrance exposure at equal SNR would be 31%-16%. Results were consistent with a model for relative entrance exposure at equal SNR, which predicted a 3-7 times reduction in entrance exposure due to SBDX's comparatively low scatter fraction (5.5%-8.1% measured, including off-focus radiation), high detector detective quantum efficiency (66%-73%, measured from 70 to 120 kVp), and large entrance field area (1.7x - 2.3x, for the same object-plane field width). With improvements to the system geometry, detector, and x-ray source, SBDX technology is projected to achieve conventional cine-quality SNR over a full range of patient thicknesses, with 5-10 times lower skin dose.

Feasibility of low‐dose single‐view 3D fiducial tracking concurrent with external beam delivery

“…Narrow beam scanning drastically reduces image scatter levels relative to conventional fluoroscopy, which in turn allows a desired image quality to be obtained with fewer primary x-rays and lower patient dose. 24 Entrance dose is further reduced because x-rays are spread over a larger area at the patient entrance, compared to conventional cone beam imaging. This study also indicates that significant integral dose reduction could be obtained in the case of single object tracking, by modifying the active portion of the scan pattern so that only the area around the object is illuminated.…”

“…23,24 The x-ray source has a focal spot that is rasterscanned over an array of positions on a transmission-style target [ Fig. 1(a)].…”

A real‐time regional adaptive exposure method for saving dose‐area product in x‐ray fluoroscopy

“…An extended discussion on the method and the imaging performance has been published, [17][18][19] and here we highlight only some of the unique features of the SBDX technology. Refer to Fig.…”

X-ray Dose Reduction through Adaptive Exposure in Fluoroscopic Imaging

“…We have shown that radiation dose can be significantly reduced in adult cardiac procedures by using our scanning beam digital x-ray (SBDX) system 4 --a fluoroscopic imaging system that employs an inverse imaging geometry 5,6 ( Figure 1, Movie 1 and Figure 2). Instead of a single focal spot and an extended detector as used in conventional systems, our approach utilizes an extended X-ray source with multiple focal spots focused on a small detector.…”

“…Pediatrics procedures are in general much more complex than those performed on adults and thus are on average four to eight times longer 1 . Furthermore, children can undergo up to 10 fluoroscopic procedures by the age of 10, and have been shown to have a three-fold higher risk of developing fatal cancer throughout their life than the general population 2,3 .We have shown that radiation dose can be significantly reduced in adult cardiac procedures by using our scanning beam digital x-ray (SBDX) system 4 --a fluoroscopic imaging system that employs an inverse imaging geometry 5,6 ( Figure 1, Movie 1 and Figure 2). Instead of a single focal spot and an extended detector as used in conventional systems, our approach utilizes an extended X-ray source with multiple focal spots focused on a small detector.…”