131 Reduced-Dose Dual-Source Coronary Computed Tomography Angiography (CCTA): Is Raw-Data-Based Iterative Reconstruction able to Maintain Diagnostic Confidence?

Abstract

PurposeTo evaluate image quality and diagnostic confidence of a raw-data-based iterative reconstruction technique (SAFIRE) in reduced-dose CCTA images in comparison with standard-dose filtered back projection (FBP) images.Materials and methods107 consecutive patients (72 males; 35 females), referred for a CCTA were prospectively included using a dual-source CT system in a high pitch (n = 51) or a sequential mode (n = 56) according to heart rate (mean DLP = 204.6 mGy.cm). From each acquisition, three series of images were reconstructed: standard-dose images reconstructed with FBP and considered as the reference standard (Group 1); and two series of reduced-dose images obtained with prototype software simulating a 30% dose reduction, and reconstructed with FBP (Group 2) or SAFIRE (Group 3). Two readers blindly evaluated each series for (a) objective noise and CNR; (b) coronary border sharpness, lesion severity; and (c) diagnostic confidence level using a 5-point scale.ResultsIn Group 2, there was a significant increase in noise compared to Group 1 (36.8 HU ±6.73 vs 30.4 HU ±5.20; p < 0.0001) and a CNR impairment (15.6 ± 4.3 vs 18.7 ± 4.5; p < 0.0001). In Group 3, despite the 30% dose reduction, SAFIRE restored the objective image quality: mean noise = 31.1 HU ±5.4 (p = 0.8) and CNR = 18.5 ± 5.0 (p = 0.7). However the diagnostic confidence was altered when compared with Group 1 (p < 0.0001), mainly rated as moderate with a blurred aspect of the coronary borders (81/107 [75.7%], p < 0.0001) and a significant number of artefactual non-flow-limiting soft plaques described in vessels considered as normal in Group 1 (105/428 [24.5%], p < 0.0001).ConclusionRaw-data-based iterative reconstruction allowed significant noise reduction but may be associated with blurring of the coronary luminal borders, which can decrease diagnostic confidence. When reporting reduced-dose CCTA with iterative reconstruction, false smooth plaque artefacts must be considered in diagnostic assessment and subsequent patient management.

Low-dose ultra-high-pitch computed tomography coronary angiography: identifying the optimum combination of iteration strength and radiation dose reduction strategies to achieve true submillisievert scans

“…Although different strengths of ADMIRE have been shown to deliver a better signal to noise ratio (SNR) and contrast to noise ratio (CNR) even for CTCA, the best strength of iteration that is optimal is still debated. This is because higher strengths of iteration can lead to excessive smoothening of the image which degrades subjective image quality (7). Another dose reduction strategy that can be used is the use of high pitch (>3) prospective ECG -triggered helical data acquisition (FLASH CTCA), wherein the complete volumetric dataset can be acquired within a fraction of a u n c o r r e c t e d p r o o f cardiac cycle.…”

“…This is because higher strengths of iteration can lead to an excessive smoothing of the image, which degrades subjective image quality. 7 …”