Semi-X

Semi-X is one of the EDR options that can be selected on FUJI CR prior to image processing. You can select this after you have prescribed a specific projection/view, but prior to scanning the barcode for the cassette ID. In this example, I attempted an axillary view of the shoulder on our phantom in the lab:

When selecting the Semi-X option, you will be given a choice of cells (1-9) as seen on the prior post, but it is crucial to properly orient your cassette, and remember how your numbered regions correspond to the green orientation bar.

For my phantom images, I decided to perform a left axillary shoulder, so I placed my green orientation bar (on a crosswise 10 x 12 cassette) closest to the "patient's" neck. This changes the layout of my numbered regions as shown:


I decided to expose my first image without the use of the Semi-X option... the following image was taken on the default "Auto" setting, which forms a histogram based on either the entire image plate, or whatever pixels lie within the recognized collimated field. It is important to note that sometimes on actual patients, the greater the soft tissue density around the patient's shoulder, the more scatter will be produced... especially in comparison with my images from a phantom. The scatter could lead to software being unable to recognize the collimated borders, thus the inclusion of more data in your histogram than what was actually in the collimated field.

This image was shot at 60 kVp, 4.2 mAs, and the resulting S# was 280 on the Auto setting:



My second image utilized identical exposure factors, but I selected the Semi-X option and chose field #7, which should be aligned with the humeral head. This gave me a much more desirable image with an S# of 159, and much better contrast with less density than on the Auto setting:



My third image utilized identical exposure factors again, but I selected the Semi-X option and chose field #4, which should be aligned with the surgical neck and proximal humerus. This gave me an even better image with an S# of 132, and even more contrast with less slightly less density than image 2:



And just for kicks, I decided to perform one more image with the same exposure factors and simulated a common error - improper selection of the numbered region. This error would occur with either improper cassette orientation, or if there was any confusion of where the green orientation bar was located. The following was set to field 6, which is outside the original collimated border, with an S# of 2968. As you can tell, the software is attempting to equalize the histogram for that region on the cassette, allowing us to see the mottle pattern of the scatter, but preventing us from visualizing the anatomy itself... it's telling us that we're severely underexposed - and that would be true if we are trying to visualize something over #6.



All in all, this is a valuable tool to utilize with exams like axillary shoulder, cross-table hip, perhaps trauma and OR views and anything which would prevent you from placing the anatomy of interest in the center of the cassette. Just remember to always know where your green orientation bar is, and how the numbered regions lie in relationship to it.