Kenneth Alan Fetterly PhD, Presenter: Nothing to Disclose

Dixon Magnuson MS, RT, Abstract Co-Author: Nothing to Disclose

Mark Hindal RT, Abstract Co-Author: Nothing to Disclose

For interventional x-ray imaging, increased patient thickness results in increased skin radiation dose rate and decreased image quality. Imaging for cardiac catheterization procedures routinely includes left/right and cranial/caudal x-ray beam angles which increase the effective patient thickness. The purpose of this work is to measure the influence of x-ray beam angle on effective patient thickness and skin dose rate during cardiac catheterization procedures.

Cine acquisition images of water equivalent phantoms of thickness 14 cm to 42 cm were acquired and x-ray technical parameters (kVp, current, pulse width, filter thickness) recorded. For each real patient cine acquisition image, the water equivalent patient thickness was measured radiographically through comparison of the x-ray technical parameters of the patient images to the equivalent parameters from the phantom images. For patient images, the cine dose rate (mGy/frame) and left/right and cranial/caudal angles were also recorded. Data were summarized in 20° increments and the influence of beam angle on effective patient thickness and radiation skin dose rate was analyzed.

Data from 5125 images of 470 consecutive adult patients was included. Median patient body mass index was 30 kg/m2 and 65% of the procedures were performed on male patients. X-ray system angles ranged from 92° left to 95° right and 45° caudal to 46° cranial. Considering all images, effective patient thickness was in the range 15 cm to 42 cm. While the median AP patient thickness (dose rate) was 21 cm (0.24 mGy/frame), the median thickness considering all angles was 28 cm (0.43 mGy/frame). Caudal angles were associated with greater effective thickness and dose rate than the equivalent cranial angles. Angular coordinates of the most commonly used projection (12%) were 20° right and 40° cranial.

X-ray system angle has a substantial influence on effective patient thickness and radiation dose rate in the cardiac catheterization lab. To minimize patient radiation skin dose and also staff dose, steep cranial and especially caudal angles should be avoided whenever possible.

Understanding the influence of x-ray beam angle on effective patient thickness and radiation skin dose will precipitate dose-efficient use of x-ray imaging in the cardiac interventional labs.

Fetterly, K, Magnuson, D, Hindal, M, Influence of X-ray Beam Angle on Effective Patient Thickness and Radiation Dose Rate in Interventional Cardiology.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9011669.html