An X-ray grid is a device used in radiographic imaging to improve the contrast of the image by
reducing the amount of scattered radiation that reaches the image receptor. It consists of a
series of lead strips that are angled to allow primary X-rays to pass through while absorbing
scattered X-rays that may degrade the quality of the image.
While seen as essential in some clinical cases, X-ray grids come with various drawbacks. These
drawbacks have prevented the widespread adoption of dual-energy technologies, as they usually need a grid. However, KA Imaging has addressed these limitations with a new approach to dual-energy imaging using the Reveal 35C and SpectralDR® technology. Keep reading to learn about modern uses of X-ray grids and how dual-energy X-ray has evolved to not need a grid.
When is it necessary to use an X-ray grid?
An X-ray grid is typically used when performing X-ray examinations of thicker body parts (generally greater than 10 cm) or when the imaging involves high radiation doses. They are particularly useful in the following situations:
- When imaging parts of the body with significant thickness (such as the abdomen or pelvis).
- When high-quality images are required, such as for chest X-rays or orthopedic studies.
- In cases where scatter radiation is likely to be high, such as using higher kilovolt peak (kVp) settings.
How does an X-ray grid improve contrast?
A grid, when properly aligned, will improve contrast in the final X-ray image by blocking scatter
radiation and ensuring more primary X-ray photons reach the detector, which can positively
impact the image’s quality and contrast.
What is grid cut-off in radiology?
Grid cut-off refers to the reduction of the useful radiation that reaches the image receptor. This is usually due to improper alignment of the grid or using the wrong type of grid for the X-ray technique. This misalignment can lead to areas of the image being underexposed or having decreased contrast. There are three distinct types of grid cut-off that can occur when using an X-ray grid:
- Lateral (off-center): When the X-ray beam is not centered to the grid.
- Angled (off-level): When the X-ray beam is angled relative to the grid strips.
- Distance: When the source-to-grid distance (SID) is not appropriate for the type of grid being used.
What is the main effect of grid cut-off?
The main effect of grid cut-off is the primary X-ray beam being “cut off” by the grid lines, and the misaligned grid lines absorbing the primary X-rays needed for high image quality and contrast. Some of the effects that result from X-ray grid cut-off is:
- Uneven image density (underexposure)
- Uneven exposure
- Increased motion and visual artifacts
- Insufficient image contrast, which makes it harder for radiologists to differentiate between tissues. This can sometimes lead to the image not being viable for diagnosis.
How does the use of a grid affect radiation exposure to the patient?
Since the grid will absorb some of the X-rays, additional radiation is needed so that enough primary X-rays reach the detector to produce a diagnostic-quality image.
Grid cut-off is one of the most prominent drawbacks that come with the use of a grid. Since the use of a grid requires a higher radiation dosage, repeat imaging isn’t always an option and must be carefully considered. Many clinical settings will prioritize limiting patient radiation exposure.
Which X-rays require a grid?
Grids are commonly used in the following imaging techniques:
- Chest X-rays: Especially in patients with larger body habitus.
- Abdominal X-rays: Due to the thickness of the abdomen and higher risk of scatter.
- Pelvic X-rays: Also comes with a higher risk of X-ray scatter.
Do I need a grid for dual-energy X-ray imaging?
- In traditional dual-exposure dual-energy X-ray — yes, an X-ray grid is needed for maintaining image quality and contrast in the subtracted images.
- But with the Reveal 35C single exposure dual-energy X-ray, a grid is not essential. Reveal 35C can produce high-quality, high-contrast X-ray images in fixed or portable applications with or without the use of a grid. Portable applications especially are vulnerable to grid cut-off and have, in the past, not been feasible with traditional dual-exposure dual-energy X-ray.
However, Reveal 35C’s SpectralDR technology uses a triple-layer design that makes it capable of taking three X-ray images at different energy levels in a single exposure, without the need for a second radiation exposure. It captures a traditional DE image, as well as a soft tissue image that subtracts out the calcium containing bone, and a bone image that subtracts out the water containing soft tissue.
SpectralDR is designed to produce high-quality images while minimizing motion artifacts and reducing repeat X-ray or CT scans, all while being portable and retrofittable.
This can streamline mobile imaging workflows, particularly useful in emergency departments and ICUs where repositioning patients is difficult.