The use of grids can improve image quality and diagnosis in chest X-rays
The use of grids can improve image quality and diagnosis in chest X-rays.
For many years, grids have been associated positively with an improvement in radiographic contrast and negatively with an increase in patient dose.
As radiographers, we know that the whole purpose of using grids in radiography is to reduce scatter radiation, thereby increasing radiographic contrast. Thus, using grids with higher ratios and higher frequencies cleans up more scatter radiation, which increases contrast more than low-ratio and low-frequency grids. Yet, higher grid ratios require more technique to penetrate, which increases the overall patient dose. What is the benefit that outweighs the risk in this cycle of increased dose versus improvement in image quality?
First, let’s take a look at two chest x-rays. Image A was not used with a grid, which is apparent due to its lack of contrast and overall reduction in image quality. When comparing Image A to Image B, it is obvious that Image B–which was taken with the use of a grid–has increased contrast and better detail.
At University of Virginia (UVA) Hospital, Charlottesville, Va., Rich Hooper, RT(R)(CV), UVA Medical Center manager for diagnostic radiology, consulted with several seasoned radiologists on ways to improve chest imaging for more accurate medical diagnosis. After looking at a large population of chest images, the group decided that mandating the use of grids with all chest X-rays would improve image quality to the degree that more accurate diagnoses would result for patients–a benefit that would far outweigh the risk.
There are many possible reasons that a patient would get a chest X-ray, typically driven by what the respiratory therapist, radiologist or ordering physician would look for when reviewing it to assess the cause of symptoms ranging from bronchitis to congestive heart failure. “Making the decision to mandate the use of grids with all chest X-rays was made in order to improve the diagnosis and overall medical care of all of our patients,” Hooper affirms. “We did not intend to increase dose to patients. It’s about saving lives every day. If we can improve image quality enough so that even the smallest pathology does not go undetected, then we have improved the chance of survival to the patients in our community.”
At Piedmont Virginia Community College (PVCC), also located in Charlottesville, we strive to educate radiography students that grid use is essential to improve image quality for patients receiving chest X-rays for medical diagnosis. Courses in radiation sciences and radiation physics, both required classes for student radiographers, highlight the concepts of grid use for medical imaging. Classroom knowledge is translated into hands-on action at UVA, the biggest clinical affiliate for PVCC student radiographers. Jason Gaviria, senior radiography student and president of his class, comments, “We have learned the benefit of slightly increasing technique when using a grid for chest X-rays instead of having to repeat an exposure due to poor image quality.” What about portable chest X-rays? There are a lot of UVA patients who currently have chest tubes in place for different medical conditions or post-surgical care for heart and lung procedures. These patients need chest X-rays routinely every morning until their lungs are healthy enough to warrant removing the chest tube. For many years, UVA mandated the use of grids on all portable chest X-rays. However, this practice created a problem; normal grid lines run longitudinally, but portable equipment required technologists to turn the cassette crosswise, resulting in unsightly grid lines that made diagnosis difficult. To solve the problem, Hooper purchased short-axis grids that allow for crosswise placement and give technologists the ability to angle the tube without resulting in unsightly grid lines on the finished radiograph.
At UVA, the radiology department provided its technologists with gridded cassettes used with computed radiography (CR) imaging, which are lighter in weight and easier to manipulate. These grids also have grid lines that run along the short axis. This past year, UVA has gone a step further to include digital portable X-ray machines. Fortunately, these machines have such superior recorded detail that we don’t have to use the grid on chest X-rays of smaller patients, thereby decreasing dose as an added bonus to the improvement of accurate medical diagnosis.
I look forward to the future of medical imaging and educating radiography students that using tools like the grid to improve diagnose is an important, lifesaving instrument in preserving the future of our patient community.
Nicole Winkler, MEd, RT(R), is assistant professor and radiography program director at Piedmont Virginia Community College.