An X-ray table bucky holds the image receptor under the tabletop and, in most rooms, carries an anti-scatter grid that removes scattered radiation before it reaches the detector. The grid improves contrast on thicker body parts, but it also raises the dose and demands accurate alignment. This explainer covers grid ratio, focusing, when a grid is needed and what virtual grid software can and cannot do.
What a bucky and an anti-scatter grid do
When the beam passes through a patient, a large share of photons scatter and travel in other directions. Scatter fogs the image and lowers contrast, particularly in the abdomen, pelvis, lumbar spine and large patients. An anti-scatter grid, placed between the patient and the receptor, is a set of thin lead strips separated by interspace material that absorb most scattered photons while letting primary photons pass.
The bucky (Potter-Bucky) is the holder in the table or wall stand that positions the receptor and grid. Older grids moved during exposure to blur out the grid lines; with modern digital systems, stationary grids with a high line density are common, and software suppresses residual line patterns. Bucky radiography therefore means imaging through the table-mounted receptor with a grid in the beam path.
Grid ratio, line density and focusing
Grid ratio is the height of the lead strips divided by the width of the interspace. A higher ratio removes more scatter and gives better contrast, but absorbs more primary radiation, so the exposure must rise and positioning becomes less forgiving. Lower ratios are more tolerant and are used for lower kV techniques and for tube angulation.
Most grids are focused: the strips are angled to match the beam divergence at a defined source-to-image distance (SID). Using a focused grid at the wrong SID or off-centre causes grid cut-off, which shows as darkening at the edges. Line density, usually quoted in lines per centimetre, affects visibility of the grid pattern on digital detectors; always match the grid to the detector as the manufacturer recommends.
- Higher ratio: better scatter removal, higher dose, tighter alignment
- Lower ratio: more tolerant, suited to angulated or portable work
- Focused grid: use at the specified SID range and centred on the beam
- Line density: choose a grid that avoids moire patterns on your detector
When to use an X-ray table with grid, and when not to
A grid is generally used for thicker body parts and higher kV techniques, such as the abdomen, pelvis, lumbar spine and the chest of a large adult. For thin parts like hands, feet and paediatric examinations a grid is usually unnecessary and only raises dose. Each facility should define grid use per examination in its protocols.
Many modern systems make grid handling automatic. Villa's Chronos R/F system has an automatic dual anti-scatter grid; the Apollo DRF table offers automatic grid selection and grid removal for paediatric exams; and the Armonicus U-arm includes two removable grids. Removable and automatic grids help match the grid to the patient without extra work for the radiographer.
Virtual grid software in DR
Virtual grid or software grid processing estimates and reduces scatter in the digital image instead of using a physical grid. It is useful for portable examinations, where aligning a physical grid with the beam is difficult, and for examinations where a grid would add dose. Villa's Moviplan iC DR offers Software Grid as an option together with Bone Suppression and Boost Lines.
Virtual grids do not remove scatter before it reaches the detector, so the physical grid remains the reference for thick body parts in many protocols. Evaluate software on your own images, compare with and without a grid under supervision of the radiologist and physicist, and confirm that dose indicators remain acceptable.
What to check when buying a bucky table
Look at the table design as a whole. The floating tabletop of Villa's Moviplan iC has a smooth surface without protruding edges and is released with a photocell system, not footswitches, which helps patient transfer and workflow. Ask about grid ratio, focusing distance, line density, bucky travel, tabletop attenuation, and AEC chambers.
Review how the grid is changed, stored and cleaned, and how the table fits the room; our article on DR room configurations and the guide on X-ray table types add context. To compare tables for your department, request a consultation from Beckfinity.
Frequently asked questions
What is a bucky in radiography?
It is the holder in the table or wall stand that positions the image receptor and anti-scatter grid under the area being imaged.
What does grid ratio mean?
It is the height of the lead strips divided by the interspace width. Higher ratios remove more scatter but need more exposure and tighter alignment.
Do I always need an anti-scatter grid?
No. Thin body parts and many paediatric exams are done without one, because the grid raises dose.
Can a virtual grid replace a physical grid?
It helps in cases where a physical grid is impractical, but it does not remove scatter before the detector, so validate it on your own images.
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