Computed Tomography | CT

Computed Tomography (CT) is a form of X-ray imaging technology that produces three-dimensional representations of structures inside the body. The process involves generating a series of two-dimensional axial images (or “slices”) made along a specified axis, which are then computationally assembled to construct a comprehensive 3D image.

Modern CT scanners, often referred to by their “generation,” have significantly advanced in speed and imaging capabilities. The latest generation CTs, such as 4th, 5th, and even 6th generation scanners, are capable of acquiring multiple axial slices simultaneously due to key innovations such as rotation speed, size/sophistication of the multidetectors, and the introduction of helical acquisition. This high-speed acquisition has enabled dynamic studies, such as CT angiography and cardiac CT, to be performed efficiently.

These later-generation CT scanners also incorporate advanced features like multi-detector rows, faster rotation times, dual energy CT, and iterative reconstruction algorithms, which can provide higher resolution images with less radiation exposure. The high-resolution, volumetric images allow for more precise diagnostic interpretations and enhanced visualization of complex anatomical structures and disease processes.

Further advancements include spectral (or dual-energy) CT scanning, which adds an additional layer of information about tissue composition based on different energy levels, and Cone Beam CT, which uses a cone-shaped X-ray beam and two-dimensional detector to create 3D images, commonly used in dental and maxillofacial imaging.

These advancements, while improving diagnostic capabilities and patient care, also increase the complexity of the CT data and pose significant challenges for encoding using the DICOM standard. The encoding of multi-phase, multi-spectral, and volumetric data may require new or complex DICOM structures. Furthermore, with higher resolution and greater numbers of slices, file sizes can become very large, leading to issues with storage and transmission.

Moreover, additional metadata associated with these advanced CT modalities, such as different energy levels used in spectral imaging, specific scanner settings, and post-processing steps, may not fit neatly within the existing DICOM framework. These challenges require the continuous evolution of the DICOM standard and careful planning and management of DICOM encoding in order to accurately represent, store, and transmit the wealth of information contained within modern CT scans.

Lastly, while DICOM aims to standardize the encoding and transmission of imaging data, variations among different manufacturers’ implementations of the DICOM standard can lead to compatibility issues, making it even more challenging to uniformly encode, exchange, and interpret the increasingly complex CT data.