At a constant grid ratio, these three parameters exhibited higher values at lower strip frequency (40 cm −1) than at higher strip frequency (60 cm −1). The grid selectivity, contrast improvement ratio, and grid exposure factor increased with higher grid ratios. Eight grids (four at 40 cm −1 strip frequency with grid ratios of 6:1, 8:1, 10:1, and 12:1, and four at 60 cm −1 strip frequency with grid ratios of 8:1, 10:1, 12:1, and 14:1) were used in this study. Applied irradiation fields were adjusted according to the simulated body parts. Various grids and acrylic phantoms of thicknesses 20 cm and 12 cm were used in this evaluation to simulate the pelvis and lumbar spine, and the cervical spine, respectively. This study effectively evaluates the image improvement factor and the conventional physical imaging properties, such as grid selectivity, contrast improvement ratio, and grid exposure factor. The film was then processed and the resulting radiograph can be seen on the slideshow below along with images of the grid alignment test process.Digital radiography (DR) is used to acquire digital images with a consistent image brightness under different exposures and in the presence of various anti-scatter grids. Each hole was exposed using 55 kVp, 2mAs and with the x-ray tube set at a 100 cm SID to the table bucky. An exposure is also required for the three holes at the end of the test tool. The grid alignment test was then performed by taking an exposure centered over each hole while the others were covered by lead strips. It was also important to ensure that the beam was centered to the bucky this was done with the help of the centering laser light on the x-ray tube. A 400 speed 8-inch by 10-inch film-screen cassette was also used in this experiment and was placed in the bucky mechanism. In this lab experiment, a moving focused grid was being used. 111).Īs shown on Figure 3, the test tool contains five holes which are evenly spaced apart and three smaller holes at one end to aid in determining the tool's orientation. Improper use of a grid however, can cause grid cutoff (which results in an underexposed radiograph) or grid artifacts such as grid lines (Papp, 2011, p. The grid is located between the patient and the image detector. The grid is designed to remove scatter radiation from the remnant beam (beam leaving the patient’s body) and to transmit only the remnant photons which carry useful information to the image receptor, as shown below in Figure 1. To eliminate this problem, a device called a radiographic grid is used to control scatter radiation. Rather, they cause the radiograph to appear gray and dull which reduces image contrast and thereby degrades image quality. Scattered x-rays that reach the detector add no diagnostic value to the image. X-rays can be deflected in any direction but scattered photons tend to scatter in a more forward direction which means that they have a higher chance of reaching the image receptor. This particular type of interaction results in a change in the x-ray direction and a reduction in x-ray energy (Bushong, 2013, p.

The scattering of the x-rays is due to an interaction called Compton scattering. When primary x-rays (x-rays leaving the tube) interact with the patient’s body, x-rays are scattered from the patient in all directions (Bushong, 2013, p.191).

Radiography grid types