Marc Regier, Presenter: Nothing to Disclose

Simon Veldhoen MD, Abstract Co-Author: Nothing to Disclose

Cyrus Behzadi, Abstract Co-Author: Nothing to Disclose

Frank Oliver Gerhard Henes MD, Abstract Co-Author: Nothing to Disclose

Chressen Catharina Remus MD, Abstract Co-Author: Nothing to Disclose

Azien Laqmani, Abstract Co-Author: Nothing to Disclose

Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose

The purpose of the presented study was to assess the diagnostic accuracy and image quality of sub-milisievert MDCT provided with the 4th generation IR technique iDoseTM for the detection of ureteric stone disease.

In 46 consecutive patients suspected of ureteral stone disease raw data of unenhanced 256 slice MDCT (120kV, 20mAs, mean CTDIvol: 0.9mGy; 29male, 17female; mean age, 42years) were reconstructed using iDose4TM. IR level settings were varied between 0 (filtered-back-projection (FBP)), 4 and 6. Images were reconstructed with a slice thickness of 3mm. Image analysis was independently performed by two blinded radiologists who assessed location and diameter of ureteral calculi. The level of confidence was recorded based on a 3-point scale (1, inconclusive; 3, confident). For evaluation of image quality a 4-point grading scale was applied regarding the depiction of anatomical details of the upper urinary tract and degree of artifacts (1, worst; 4, excellent). The signal-to-noise ratio (SNR) was assessed. Statistical evaluation included weighted kappa and Wilcoxon analysis.

A total of 26 ureteral stones was found ranging from 1 to 8 mm (mean, 3.2 mm). Sensitivity rates were equivalent for FBP and IR, regardless of the iteration level. The level of confidence was superior for data sets reconstructed with IR (FBP, 2.4; IR4, 2.6; IR6, 2.6; p>0.05). Compared to FBP (mean score, 2.78) a significant improve in image quality was assessed applying an IR level of 4 (mean score, 3.41; p,0.02). However, applying the highest iDoseTM level of 6 blotchy appearance of anatomical contours was observed limiting image quality (mean score, 3.16). Interrater agreement was excellent (Κ, 0.91; p<0.01). With increasing IR levels, reduction of streak artifacts was quantified by a decrease of image noise. Loss of anatomical information was not observed.

Ureteral stone disease can reliably be achieved by ultra low-dose MDCT at radiation doses in the submilisievert range. Whereas the application of IR does not affect the accuracy of stone detection, a slight improvement in diagnostic confidence and a significant increase in image quality can be reached applying IR level 4.

Applying IR of the 4th generation for submilisievert MDCT of the upper urinary tract remarkably improves image quality and allows for stone detection with higher confidence compared to filtered back projection.

Regier, M, Veldhoen, S, Behzadi, C, Henes, F, Remus, C, Laqmani, A, Adam, G, Ultra Low-dose MDCT for the Detection of Ureteric Stone Disease: Diagnostic Accuracy and Image Quality in Sub-milisievert MDCT Using 4th Generation Iterative Reconstruction for Noise Reduction.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014142.html