الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Urolithiasis is a prevalent health problem with high recurrence rate, with as many as 75% of those with a single-stone episode experiencing a recurrence during their lifetime. With complications such as hydronephrosis and consecutive kidney malfunction, urlithiasis demands a quick diagnostic procedure.
Non-contrast computed tomography (CT) remains the diagnostic imaging gold standard for urolithiasis due to its higher sensitivity and specificity (>95% and >96%, respectively) for the detection of stones compared with alternative imaging techniques.
However, CT exposes the patient to substantial ionizing radiation. The lifetime cancer risk from cumulative radiation exposure is elevated further in young patients, who often require multiple CT examinations during treatment and follow up, therefore, efforts have been made to lower CT dose with the scanning parameter selection namely tube voltage and tube current.
However, low-radiation-dose abdominal CT was shown to be associated with decrease in image quality due to the excessive image noise when conventional image reconstruction algorithm filtered back-projection (FBP) is used, potentially causing a decrease in diagnostic performance and confidence.
Recently, several vendors have released tools using iterative reconstruction (IR) techniques as alternative to the conventional image reconstruction algorithm filtered back-projection (FBP).The aim of those tools is a reduction of tube voltage and exposure settings resulting in a lower radiation dose without a concomitant loss of image quality due to an increase of image noise.
Our study aimed at evaluating the image quality and diagnostic performance of non enhanced abdominal computed tomography (CT) with iterative reconstruction (IR) compared to filtered back-projection (FBP) in assessment of urolithiasis.
40 patients with suspected or known urinary stone disease, with age ranged from 22 to 75 years and body mass index (BMI) <35 were scheduled for clinically indicated non-enhanced abdominal CT at the radiology department of Alexandria main university hospital and were included in this study. 20 patients underwent non-contrast abdominal CT using a standard dose protocol (SDCT) using tube voltage of 110 kV and exposure of 250 mA, the other 20 patients underwent non-contrast abdominal CT using low dose protocol (LDCT) using tube voltage of 80 kV and exposure of 180 mA.
CT image volumes were reconstructed for each dose group using standard FBP technique and SAFIRE with vendor recommended strength of 3/5
Prior to analysis of CT images, all data were anonymized and randomized.
Dose-length product (DLP), effective dose, Image noise N, contrast to noise ratio CNR and signal to noise ratio SNR were recorded for each case.
Two consultant experienced radiologists who were blinded to the patients’ technical scanning parameters independently evaluated the randomized FBP and SAFIRE images on an imaging work station and subjectively graded the image’s quality, noise, and the reviewer’s confidence in each image set according to the previously reported 3 or 5 point scale.
Reduction of tube voltage and tube current led to significant dose reduction with a percentage of 71.9% (P < 0.001).
In the same dose protocol, SAFIRE images showed significantly lower objective image N and significantly higher SNR and CNR than in FBP images (P < 0.001).
In standard dose protocol, according to both readers, subjective quality scores were significantly higher in SAFIRE images than in FBP images (P = 0.007 for reader 1 and 0.011 for reader 2). The subjective noise scores were significantly lower in SAFIRE images than in FBP images (P < 0.001 for both readers).
In low dose protocol, according to both readers, the subjective N scores were significantly lower in SAFIRE images than in FBP images (P <0.001 for both readers). Reader 1 found no significant difference in subjective quality between SAFIRE images and FBP images (P= 0.825) while reader 2 found SAFIRE images of significantly higher quality than FBP (P= 0.029).