Does the Size of the Focal Spot in Digital Radiography Machines Affect Imaging Quality?


Compared to traditional X-ray machines, digital radiography (DR) machines, which use digital technology, offer a wide dynamic range and high exposure tolerance. This allows for high-quality imaging even under challenging exposure conditions and for objects with a wide range of thicknesses in a single exposure. Additionally, these devices feature high resolution, clear and detailed images. During the detection process, various image post-processing techniques, such as digital subtraction, can be employed to achieve the desired inspection results. Moreover, digital DR machines boast high detection efficiency, low pollution, reduced radiation doses, and easy image storage.

Currently, digital DR machines have become standard equipment in modern hospitals. Depending on the medical condition, DR machines can be used for examinations of multiple body parts, aiding in the diagnosis of various diseases. Examples include examinations of the skull, cervical spine, chest, lumbar spine, abdominal cavity, pelvic cavity, and limbs.

When hospitals procure digital DR machines, attention should be given to the focal spot size of the DR, as it significantly impacts imaging quality.

The X-ray tube, commonly known as the tube, is one of the core components of a digital DR machine, responsible for generating X-rays by converting electrical energy into X-rays. The focal spot of a digital DR machine refers to the nominal focal spot size of the X-ray tube.

The focal spot is the position where electrons strike the target surface, and the size of the focal spot is the area of contact where electrons hit the anode target surface. The size of the focal spot affects the clarity of the digital image: a larger focal spot results in more blurred image edges (i.e., more pronounced penumbra), whereas a smaller focal spot produces sharper image edges and clearer images.

Although a smaller focal spot provides clearer images, it has limited exposure doses, making a larger focal spot more reliable for imaging thicker areas. Additionally, a smaller focal spot concentrates higher energy, generating more heat and potentially causing the focal spot surface to melt. A larger focal spot can withstand higher current, generating brighter X-rays and shortening the imaging time.

Given these characteristics, many digital DR machines on the market now use dual focal spot technology, employing two different filament sizes to produce varying effective focal spot sizes. For example, Perlove Medical’s PLX8500 digital medical X-ray imaging system is equipped with a high-capacity tube and a high-power generator. Its flat panel and tube can achieve dual rotation. The rotating tube facilitates imaging of positions like the cervical spine and patella axis. For patients who are immobile or in wheelchairs, the rotating flat panel detector allows for easy imaging of upper and lower limbs. The detector can rotate ≥90° and the tube can rotate ≥180°, making clinical positioning more convenient and addressing various clinical positioning needs.


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