Evolution in Computed Tomography

Abstract

The advent of computed tomography (CT) has revolutionized radiology. Starting as head-only scanners, modern CT systems are now capable of performing whole-body examinations within a couple of seconds in isotropic resolution. Technical advancements of scanner hardware and image reconstruction techniques are reviewed and discussed in their clinical context. These improvements have led to a steady increase of CT examinations in all age groups for a number of reasons. On the one hand, it is very easy today to obtain whole-body data for oncologic staging and follow-up or for trauma imaging. On the other hand, new examinations such as cardiac imaging, virtual colonoscopy, gout imaging, and whole-organ perfusion imaging have widened the application profile of CT. The increasing awareness of risks associated with radiation exposure triggered the development of a variety of dose reduction techniques. Effective dose values below 1 mSv, less than the annual natural background radiation (3.1 mSv/year on average in the United States), are now routinely possible for a number of dedicated examinations, even for coronary CT angiography.

Relationship between low tube voltage (70 kV) and the iodine delivery rate (IDR) in CT angiography: An experimental in-vivo study

“…For a single CTA, however it is certainly possible to achieve similar noise levels. It has been demonstrated previously, that 70 kVp CTA allows for significant radiation dose savings with comparable SNR and CNR [20], and iterative reconstruction techniques are commonly employed to further reduce image noise [6]. In contrast to dynamic CTA without table movement, the temporal resolution of dynamic spiral acquisition with continuous table movement back and forth is reduced and the time interval between two measurements at the same slice position is not identical except at the central z-position.…”

“…Previously, the use of low-kV protocols in fast thoraco-abdominal CTA was restricted to children and patients with a low body mass index because of insufficient tube output capacity [5], but the latest CT systems mitigate this problem with more powerful x-ray tubes [2, 6–9]. When the scan time of a body CTA is on the order of 5 s or less, the traditional CM injection protocols need to be reconsidered and short and compact injection protocols should be preferred to those protocols that are optimized to provide a long and stable plateau phase of enhancement [10].…”

Alterations of MicroRNA Expression in the Liver, Heart, and Testis of Mice Upon Exposure to Repeated Low-Dose Radiation

“…To approximate the dose delivered in medical examinations, 28 mGy, which is equivalent to a whole-body computed tomography examination, was selected as the LDR dose. 11 A Gammacell 40 Exactor (Nordion Intl Inc, Canada) was used to deliver the whole-body LDR at a dose rate of 0.84 Gy/min.…”

Image quality, diagnostic accuracy, and potential for radiation dose reduction in thoracoabdominal CT, using Sinogram Affirmed Iterative Reconstruction (SAFIRE) technique in a longitudinal study

“…To overcome these limitations and improve image quality in reduced-dose (RD) CT, iterative reconstruction techniques, as a rather old method for image optimization [8], are increasingly applied in clinical routine. Each CT vendor has introduced a different iterative reconstruction technique [9]. Sinogram-affirmed iterative reconstruction (SAFIRE, Siemens Healthcare, Forchheim, Germany) is an algorithm applied on Siemens CT systems without Stellar detectors.…”