CT colonography at low tube potential: using iterative reconstruction to decrease noise

Advanced CT Techniques for Decreasing Radiation Dose, Reducing Sedation Requirements, and Optimizing Image Quality in Children

CT is an invaluable diagnostic tool for pediatric patients; however, concerns have arisen about the potential risks of ionizing radiation associated with diagnostic imaging in young patients, particularly for pediatric populations that may require serial CT examinations. Recent attention has also been focused on the immediate and long-term risks of administration of anesthetic medications to infants and young children who require sedation to undergo imaging examinations. These concerns can be mitigated with use of advanced CT techniques that can decrease scan time and radiation dose while preserving image quality. In this article, current state-of-the-art CT acquisition techniques are reviewed as part of a comprehensive strategy to reduce radiation dose, decrease sedation needs, and optimize image quality in infants and young children. Three imaging strategies are discussed, including (a) dual-energy CT (DECT), (b) imaging with a low tube potential, and (c) rapid scanning. Consolidating multiphase imaging protocols into a single phase with virtual nonenhanced imaging on DECT scanners, as well as use of low tube voltage, can reduce the radiation dose while increasing the conspicuity of contrast material-enhanced structures with a reduced volume of iodinated contrast material and a reduced rate of injection. Rapid scanning techniques with either ultrahigh pitch at dual-source CT or with wide-area detector single-source CT facilitate scanning without the need for sedation in many children. ^©RSNA, 2019 See discussion on this article by Szczykutowicz .

An open label, prospective, multicenter, non-interventional study of iodixanol 270 mg I/mL for use in individuals undergoing computed tomography angiography in real-world clinical practice

BACKGROUND

Concern about radiation exposure is leading to an increasing interest in low-concentration contrast medium administration.

PURPOSE

To evaluate the image quality and safety profile after administration of iodixanol 270 mg I/mL at 100-kVp tube voltage with iterative reconstruction in subjects undergoing computed tomography angiography (CTA).

MATERIAL AND METHODS

Patients who completed CTA examination using iodixanol 270 mg I/mL and 100-kVp tube voltage along with iterative reconstruction for coronary, aortic, head and neck, renal, or pulmonary arteries were included. Image quality was qualitatively and quantitatively evaluated. Incidence of adverse events (AEs) and adverse drug reactions (ADRs) within seven days and radiation dose were also analyzed.

RESULTS

A total of 4513 individuals in 42 centers in China were enrolled, among which 4367 were included in efficacy analysis. The mean image quality score was 4.8 ± 0.45 across all arteries (all above 4.6) and 99.7% of the individuals' images were classified as evaluable. The CT attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in the regions of interest (ROIs) were 431.79 ± 99.018, 18.29 ± 11.947, and 28.21 ± 19.535 HU, respectively. Of all the participants, 68 (1.5%) and 65 (1.4%) experienced AEs and ADRs, respectively. No serious AEs or AEs leading to discontinuation occurred. The average effective radiation dose was 3.13 ± 2.550 mSv.

CONCLUSION

Iodixanol 270 mg I/mL in combination with 100-kVp tube voltage and iterative reconstruction could be safely applied in CTA and yield high-quality and evaluable images with reduced radiation dose.

Low-Dose Computed Tomography Colonography Technique

Significant anxiety has been expressed by some over the radiation risks associated with computed tomography (CT), particularly when it applies to a screening examination such as CT colonography. These theoretic risks are far outweighed by the significant benefits colorectal cancer screening offers. Regardless of how significant the theoretic risk of CT radiation is in the older population, the ALARA principle maintains that radiation dose should be reduced to As Low As Reasonably Achievable. This article will discuss various strategies that may be utilized to reduce radiation dose and mitigate any increase in image noise that may occur.

CTC technique: methods to ensure an optimal exam

CT colonography (CTC) has demonstrated equivalent accuracy to optical colonoscopy in the detection of clinically relevant polyps and tumors but this is only possible when technique is optimized. The two most important features of a high-quality CTC are a well-prepared colon and a distended colon. This article will discuss the dietary, bowel preparation, and fecal/fluid tagging options to best prepare the colon. Strategies to optimally distend the colon will also be discussed. CT scan techniques including patient positioning and radiation dose optimization will be reviewed. With proper technique which includes sufficient bowel preparation, fecal/fluid tagging, bowel distension, and optimized scan technique, high-quality CTC examinations should become more feasible, easier to interpret, and more consistently reproducible leading to increased utilization and increased referrals.