...that is the question. We all learned (or are in the process of learning) in school to use a grid on anatomy over 10 cm in part thickness or on techniques that require more than 70 kVp. But when you get right down to it, most technologists are not using grids for their portable chest x-rays. Why could this be? I'm so glad you asked... most grids have the lead strips running along the long axis of the grid. If you practice angulation perpendicular to the sternum (see prior "Lordotic Much" post), then you will find yourself with tons of grid cutoff when performing a crosswise cassette/grid placement. Having tried this on Kodak and Fuji systems with a lengthwise cassette, I can honestly say that the images are quite better. I'll give you one guess which of the following images was taken non-grid vs. with an 8:1 grid:
I know what you're thinking... "so what do I do when I have a crosswise chest x-ray to perform?" Well, you're pretty much out of luck unless you can convince your radiology department to purchase a few SD (short dimension) grids. Some companies manufacture these, and as we all know, grids can be very expensive, so take extra special care of these. The grid lines are arranged along the short axis of the grid to allow for crosswise placement, and to give the technologist the ability to angle cephalic or caudal without having those unsightly grid lines on your finished radiograph.
On a special note to anybody planning on purchasing these grids, make sure to check two aspects of your CR equipment before purchasing them. First, you need to see how your cassettes are scanned by the image reader (the laser will most often scan the photostimulable phosphor plate perpendicular to the direction of travel). If the CR system scans along the short axis of the phosphor screen (the same axis as the SD grid), then you want to make sure that the grid frequency (not ratio) is slightly higher than the scan frequency. This will prevent an alaising/moire artifact shown here:
Be sure to check with your quality assurance team to ensure that you are purchasing the proper grids at the right grid frequency.