Improved visual delineation of the intimal flap in Stanford type A and B dissections at 3rd generation dual-source high-pitch CT angiography.

OBJECTIVE: Evaluation of the intimal flap visibility comparing 2nd and 3rd generation dual-source high-pitch CT. METHODS: Twenty-five consecutive patients with aortic dissection underwent CT angiography on a second and third generation dual-source CT scanner using prospective ECG-gated high-pitch dual-source CT acquisition mode. Contrast material, saline flush and flow rate were kept equal for optimum comparability. The visibility of the intimal flap as well as the delineation of the different vascular structures was evaluated. RESULTS: In 3rd generation dual-source high-pitch CT we could show a significant improvement of intimal flap visibility in aortic dissection. Especially, the far end of the dissection membrane could be better evaluated in 3rd generation high-pitch CT, reaching statistical significance (P < 0.01). CONCLUSION: 3rd Generation high-pitch CT angiography shows a better delineation of the aortic intimal flap in a small patient cohort, especially in the far ends of the dissection membrane. This might be due to higher tube power in this CT generation. However, to generalise these findings larger trials are needed.

Evaluation of different keV-settings in dual-energy CT angiography of the aorta using advanced image-based virtual monoenergetic imaging.

To compare quantitative image quality in dual-energy CT angiography (DE-CTA) studies of the aorta using different virtual monoenergetic imaging (MEI) and advanced image-based virtual monoenergetic (MEI+) settings at varying kiloelectron volt (keV) levels. Fifty consecutive patients with clinically-indicated CT of the whole aorta to evaluate suspected aortic disease underwent DE-CTA on a third-generation dual-source CT scanner. Quantitative image quality indices were assessed. Contrast material, saline flush and flow rate were kept equal for optimum comparability. DE-CTA MEI and MEI+ series ranging from 40 to 100 keV (10-keV intervals) were reconstructed. Signal intensity, noise, signal-to-noise ratio and contrast-to-noise ratio (CNR) of multiple aortic segments were evaluated. Comparisons between the different MEI and MEI+ datasets were performed. Three-hundred aortic segments total were evaluated. In the MEI+ series the 40, 50 and 100 keV MEI+ showed superior noise and CNR levels (+84, +58, +103 % on average; all p < 0.05) compared to MEI. However, signal intensity between MEI+ and MEI at nearly all aortic segments showed no significant difference (p > 0.1). MEI+ shows lower image noise compared to MEI, resulting in superior quantitative image quality, in particular at low keV levels (40 or 50 keV).

Low-dose CT pulmonary angiography on a 15-year-old CT scanner: a feasibility study.

BACKGROUND: Computed tomography (CT) low-dose (LD) imaging is used to lower radiation exposure, especially in vascular imaging; in current literature, this is mostly on latest generation high-end CT systems. PURPOSE: To evaluate the effects of reduced tube current on objective and subjective image quality of a 15-year-old 16-slice CT system for pulmonary angiography (CTPA). MATERIAL AND METHODS: CTPA scans from 60 prospectively randomized patients (28 men, 32 women) were examined in this study on a 15-year-old 16-slice CT scanner system. Standard CT (SD) settings were 100 kV and 150 mAs, LD settings were 100 kV and 50 mAs. Attenuation of the pulmonary trunk, various anatomic landmarks, and image noise were quantitatively measured; contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) were calculated. Three independent blinded radiologists subjectively rated each image series using a 5-point grading scale. RESULTS: CT dose index (CTDI) in the LD series was 66.46% lower compared to the SD settings (2.49 ± 0.55 mGy versus 7.42 ± 1.17 mGy). Attenuation of the pulmonary trunk showed similar results for both series (SD 409.55 ± 91.04 HU; LD 380.43 HU ± 93.11 HU; P = 0.768). Subjective image analysis showed no significant differences between SD and LD settings regarding the suitability for detection of central and peripheral PE (central SD/LD, 4.88; intra-class correlation coefficients [ICC], 0.894/4.83; ICC, 0.745; peripheral SD/LD, 4.70; ICC, 0.943/4.57; ICC, 0.919; all P > 0.4). CONCLUSION: The LD protocol, on a 15-year-old CT scanner system without current high-end hardware or post-processing tools, led to a dose reduction of approximately 67% with similar subjective image quality and delineation of central and peripheral pulmonary arteries.