Tomosynthesis , also digital thomosynthesis , is a method for performing high-resolution angular boundary tomography at radiation dose levels proportional to projection radiography. It has been studied for a variety of clinical applications, including vascular imaging, dental imaging, orthopedic imaging, mammography imaging, musculoskeletal imaging, and chest imaging.
Video Tomosynthesis
Histori
The concept of tomosynthesis comes from the work of Ziedses des Plantes, which developed the method of reconstructing a number of planes from a series of projections. Although this idea was displaced by the emergence of computed tomography, tomosynthesis then gained attention as an alternative to low-dose tomography for CT.
Maps Tomosynthesis
Reconstruction
The reconstruction algorithm of Tomosythesis is similar to the reconstruction of CT, where they are based on performing reverse Radon transformations. Because of partial data sampling with very little projection, an approximation algorithm should be used. The filtered back projection and the iterative expectation and expectations algorithm have been used to reconstruct the data.
The reconstruction algorithm for tomosynthesis differs from conventional CT because conventionally filtered projection algorithms require a complete set of data. Iterative algorithms based on expected expectations are most commonly used, but are computationally intensive. Some manufacturers have produced practical systems using off-the-shelf GPUs to perform reconstruction in a few seconds.
Differences from other imaging modalities
Digital tomosynthesis combines digital image capture and processing with simple tube/detector movements such as those used in conventional computed tomography (CT). However, although there are some similarities with CT, it is a separate technique. In CT, the source/detector makes at least 180 degrees of complete rotation about the subject obtaining a complete set of data from which images can be reconstructed. Digital tomosynthesis, on the other hand, uses only a limited rotational angle (eg, 15-60 degrees) with a lower number of discrete exposures (eg, 7-51) than CT. This incomplete projection set is digitally processed to produce images similar to conventional tomography with limited field depth. Due to the processing of digital images, a series of slices at different depths and with different thicknesses can be reconstructed from the same acquisition. However, since fewer projections are needed than CT to do reconstruction, radiation exposure and cost are both reduced.
Apps
Breast
Tomosynthesis is a Food and Drug Administration (FDA) approved for use in breast cancer screening. By 2016 it is unclear whether its use in screening women at normal risk is beneficial or harmful.
Digital breast tyrosynthesis (DBT) can provide higher diagnostic accuracy than conventional mammography. In DBT, like conventional mammography, compression is used to improve image quality and reduce radiation dose. The laminographic imaging technique dates from the 1930s and includes geometric or linear tomography categories.
Since the data obtained are 85-160 microns of typical resolution, much higher than CT, DBT can not offer narrow wedge widths that offer CT (typically 1-1.5 mm). However, the higher resolution detector allows very high resolution in the plane, although the Z-axis resolution is less. The main interest in DBT is in breast imaging, as an extension to mammography, where it offers better detection rates with a slight increase in radiation.
Musculoskeletal imagery
Tomosynthesis has a much more limited depth of field than CT. For this reason, it is unlikely that it will be able to replace CT for deeper organ evaluation. However, since bones are often located near the skin, several musculoskeletal applications of thomosynthesis have been studied, most of which have been largely used in research with limited use in day-to-day practice.
Fracture evaluation
Tomosynthesis has been compared with radiography and CT for evaluation of healing fractures, especially in the presence of hardware. In a study of patients with wrist fractures, digital tomosynthesis was shown to allow for more fracture detection of radiographs while simultaneously providing lower metal artifacts than radiography.
Evaluation of erosion in rheumatoid arthritis
Tomosythesis has been compared with radiography, with CT as a standard, to detect erosions associated with rheumatoid arthritis. The dose of digital tomosynthesis radiation is very close to the radiography. However, tomosynthesis showed sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 80%, 75%, 78%, 76%, and 80%, compared to radiography were 66%, 81%, 74%, 77% and 71%. Little digital Tomosynthesis benefits in this application may or may not justify a slight increase in modal cost compared to radiography.
References
External links
- Digital Tomosynthesis: Advanced Breast Cancer Imaging Technique, by Max Wiedmann, UCSB
Source of the article : Wikipedia
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