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To create a CT texture-based machine learning algorithm that distinguishes benign from potentially malignant cystic renal masses as defined by the Bosniak Classification version 2019. In this IRB-approved, HIPAA-compliant study, 4,454 adult patients underwent renal mass protocol CT or CT urography from January 2011 to June 2018. Of these, 257 cystic renal masses were included in the final study cohort. Each mass was independently classified using Bosniak version 2019 by three radiologists, resulting in 185 benign (Bosniak I or II) and 72 potentially malignant (Bosniak IIF, III or IV) masses. Six texture features: mean, standard deviation, mean of positive pixels, entropy, skewness, kurtosis were extracted using commercial software TexRAD (Feedback PLC, Cambridge, UK). Random forest (RF), logistic regression (LR), and support vector machine (SVM) machine learning algorithms were implemented to classify cystic renal masses into the two groups and tested with tenfold cross validations. Higher mean, standard deviation, mean of positive pixels, entropy, skewness were statistically associated with the potentially malignant group (P ≤ 0.0015 each). Sensitivity, specificity, positive predictive value, negative predictive value, and area under curve of RF model was 0.67, 0.91, 0.75, 0.88, 0.88; of LR model was 0.63, 0.93, 0.78, 0.86, 0.90, and of SVM model was 0.56, 0.91, 0.71, 0.84, 0.89, respectively. Three CT texture-based machine learning algorithms demonstrated high discriminatory capability in distinguishing benign from potentially malignant cystic renal masses as defined by the Bosniak Classification version 2019. If validated, CT texture-based machine learning algorithms may help reduce interreader variability when applying the Bosniak classification.

Computed tomography urography (CTU) has emerged as the modality of choice for imaging the urinary tract within the past few decades. It is a powerful tool that enables detailed anatomic evaluation of the urinary tract in order to identify primary urothelial malignancies, benign urinary tract conditions, and associated abdominopelvic pathologies. As such, there have been extensive efforts to optimize CTU protocol. This article reviews the published literature on CTU protocol optimization, including contrast bolus timing, dose reduction, reconstruction algorithms, and ancillary practices. There have been many advances in CTU techniques, which allow for imaging diagnosis of a wide spectrum of diseases while minimizing radiation dose and maximizing urinary tract distension and opacification.

PURPOSE: The aim of this pictorial essay is to demonstrate several cases where the diagnosis would have been difficult or impossible without the excretory phase image of CT urography. METHODS: A brief discussion of CT urography technique and dose reduction is followed by several cases illustrating the utility of CT urography. RESULTS: CT urography has become the primary imaging modality for evaluation of hematuria, as well as in the staging and surveillance of urinary tract malignancies. CT urography includes a non-contrast phase and contrast-enhanced nephrographic and excretory (delayed) phases. While the three phases add to the diagnostic ability of CT urography, it also adds potential patient radiation dose. Several techniques including automatic exposure control, iterative reconstruction algorithms, higher noise tolerance, and split-bolus have been successfully used to mitigate dose. The excretory phase is timed such that the excreted contrast opacifies the urinary collecting system and allows for greater detection of filling defects or other abnormalities. Sixteen cases illustrating the utility of excretory phase imaging are reviewed. CONCLUSIONS: Excretory phase imaging of CT urography can be an essential tool for detecting and appropriately characterizing urinary tract malignancies, renal papillary and medullary abnormalities, CT radiolucent stones, congenital abnormalities, certain chronic inflammatory conditions, and perinephric collections.

Background The purpose was to assess radiation dose, image quality, and diagnostic performance of reduced-dose scanning with iterative reconstruction (IR) compared with standard-dose with filtered back projection (FBP) with CT urography for detection of bladder tumor. This study was prospectively conducted on 21 patients with bladder masses. All patients were subjected to two scanning protocols: protocol A (standard dose with FBP) and protocol B (additional limited scan to the pelvis at delayed phase with low dose with IR). Based on body weight (< or > 80 kg), each protocol was subdivided into 2 protocols A1 (130 kVp) and A2 (130 kVp) and protocols B1 (80 kVp) and B2 (110 kVp). Radiation dose was assessed in terms of mean CT dose index (CTDI), Dose-length product (DLP) and effective dose (ED). Image quality and diagnostic accuracy were compared in both groups. Results Mean CTDI, DLP and ED were reduced by average 72.3 % in the 80 kVp protocol (B1) and by 36.3% in 110 kVp (B2) protocol compared to standard-dose protocols. There were significantly lower SNR (signal to noise ratio) between protocol A1 and B1 at aorta and psoas muscles. Subjective image quality analysis revealed no statistically significant differences between the protocol A2 and B2 whereas there were significant differences between protocol A1and B1 as regards to visual image noise and overall image quality. Diagnostic accuracy was identical among different protocols. Conclusion CT urography with IR scanning showed reduced radiation dose and no difference in detection of urothelial carcinomas from standard dose with FBP despite of degraded image quality in 80 kVp scanning.

Dual-energy CT is being increasingly used for abdominal imaging due to its incremental benefit of material characterization without significant increase in radiation dose. Knowledge of the different dual-energy CT acquisition techniques and image processing algorithms is essential to optimize imaging protocols and understand potential limitations while using dual-energy CT renal imaging such as urinary calculi characterization, assessment of renal masses and in CT urography. This review article provides an overview of the current dual-energy CT techniques and use of dual-energy CT in renal imaging.

To retrospectively evaluate the diagnostic performance of single-phase dual-energy CT (DECT) with virtual non-contrast CT (VNCT) compared with three-phase CT urography (CTU) in patients with haematuria. A total of 296 patients underwent three-phase CTU (NCT at 120 kVp; nephrographic phase and excretory phase DECTs at 140 kVp and 80 kVp) owing to haematuria. Diagnostic performances of CT scans were compared for detecting urothelial tumours and urinary stones. Dose-length product (DLP) was compared in relation to single-phase DECT and three-phase CTU Dose-length product (DLP) was compared in relation to single-phase DECT and three-phase CTU. Sensitivity and specificity for tumour were 95 % (19/20) and 98.9 % (273/276) on CTU, 95 % (19/20) and 98.2 % (271/276) on nephrographic phase DECT, and 90 % (18/20) and 98.2 % (271/276) on excretory phase DECT (P > 0.1). Of the 148 stones detected on NCT, 108 (73 %) and 100 (67.6 %) were detected on nephrographic phase and excretory phase VNCTs, respectively. The mean size of stones undetected on nephrographic and excretory VNCTs was measured as 1.5 ± 0.5 mm and 1.6 ± 0.6 mm, respectively. The mean DLPs of three-phase CTU, nephrographic phase DECT and excretory phase DECT were 1076 ± 248 mGy · cm, 410 ± 98 mGy · cm, and 360 ± 87 mGy · cm, respectively (P

To compare acetabular version angle measurements of CT scans in the prone and reformatted supine positions. CT acetabular version angle measurements have previously been done in the prone position to correct for pelvic tilt. With the advent of multidetector CT, recent studies have evaluated acetabular version angles measured in the supine position. To our knowledge, a comparison between these two approaches has not been performed. Case series in which consecutive CT urography studies of 49 adult patients performed in both prone and supine positions were retrospectively reviewed, and acetabular version angles of both hips measured. Retrospective review of 49 consecutive CT urography studies performed in both prone and supine positions was done, and acetabular version angles of both hips were measured. Two radiologists measured the acetabular version angles independently. Multiplanar reformation of the supine CT images was performed to compensate for pelvic tilt and rotation prior to angle measurements. There was excellent interobserver agreement between the two readers (ICC = 0.90). Acetabular version angle measurements from the prone CT images were larger compared to reformatted supine images (24.0 and 21.3°, respectively, p

To determine the yield of CT urography (CTU) in the surveillance of patients with bladder cancer following cystectomy. In this IRB-approved, HIPAA-compliant, retrospective study of 5,404 CT urograms performed at our institution between March 2000 and February 2011, 225 CT urograms were performed in 105 patients [79 men, 26 women; mean age 65 years (43–85)] following cystectomy for bladder cancer. Median follow-up after cystectomy was 63 months (range 1–234), median time between cystectomy and CTU was 39 months (range 0–229), median follow-up after CTU was 34 months (range 1–111). CTU examinations were reviewed by two radiologists in consensus and findings were categorized into those related to surgery, locoregional recurrence, metastases, or metachronous upper tract urothelial tumor (UTT). Findings were present in 69 (65.7 %) of 105 patients, including findings related to surgery in 60 (57.1 %) patients, locoregional recurrence or metastatic disease in 21 (20 %) patients, and UTT in 3 (2.9 %) patients. Of surgery-related findings, hydronephrosis (23/105, 21.9 %) and parastomal hernia (17/105, 16.2 %) were the most common findings. Visceral metastases (16/105, 15.2 %) and lymph node metastases (13/105, 12.4 %) were the most common manifestations of recurrent disease. CTU findings in the surveillance of patients with bladder cancer after cystectomy are common and include those related to surgery, spread of the disease, and metachronous tumors. Our study supports current published guidelines on the use of CTU in these patients.

Background Duplex kidney is a common anomaly that is frequently associated with multiple complications. Typical computed tomography urography (CTU) includes four phases (unenhanced, arterial, parenchymal and excretory) and has been suggested to considerably aid in the duplex kidney diagnosi. Unfortunately, regarding duplex kidney with prolonged dilatation, the affected parenchyma and tortuous ureters demonstrate a lack of or delayed excretory opacification. We used prolonged-delay CTU, which consists of another prolonged-delay phase (1- to 72-h delay; mean delay: 24 h) to opacify the duplicated ureters and affected parenchyma. Methods Seventeen patients (9 males and 8 females; age range: 2.5–56 y; mean age: 40.4 y) with duplex kidney were included in this study. Unenhanced scans did not find typical characteristics of duplex kidney, except for irregular perirenal morphology. Duplex kidney could not be confirmed on typical four-phase CTU, whereas it could be easily diagnosed in axial and CT-3D reconstruction using prolonged CTU (prolonged-delay phase). Results Between January 2005 and October 2010, in this review board-approved study (with waived informed consent), 17 patients (9 males and 8 females; age range: 2.5 ~ 56 y; mean age: 40.4 y) with suspicious duplex kidney underwent prolonged CTU to opacify the duplicated ureters and confirm the diagnosis. Conclusion Our results suggest the validity of prolonged CTU to aid in the evaluation of the function of the affected parenchyma and in the demonstration of urinary tract malformations.

To detail the utility of CT scan in detection of urinary stones induced by melamine tainted formula. A total of 1062 children fed with melamine-contaminated infant formula were screened for urinary stones in our institute from September through December 2008. Ultrasonography of the urinary tract system was performed in all these children. If the children with suspected stones or severe obstruction were presented after ultrasound examination, the multi-detector row CT urographic examination was advocated subsequently. Ultrasound examination in combination with multi-detector row CT urography could increase the diagnostic rate from 3.4% (36/1062) by ultrasound examination alone to 4.6% (49/1062). The specificity and sensitivity of the multi-detector row CT urographic examination is higher than ultrasonography.

To assess the effect of oral hydration and contrast-medium volume on renal enhancement and urinary tract opacification in multi-detector CT urography.A total of 192 patients were assigned to different protocols with varying doses of contrast agent with and without oral hydration. The attenuation was measured in the renal parenchyma in the unenhanced, nephrographic and excretory phase, and in the urinary tract in excretory phase imaging, respectively. Opacification of the urinary tract was graded on volume rendered images.Oral hydration did not significantly alter renal parenchymal enhancement in both the nephrographic and the excretory phase (p0.001), but significantly decreased mean attenuation of the urinary tract in the excretory phase (por = 0.001), and improved continuous opacification of all ureter segments (p0.01). Higher volumes of contrast medium improved renal parenchymal enhancement (por = 0.001) and continuous opacification of the urinary tract (por = 0.01).Oral hydration leads to lower attenuation values in the urinary tract but improves the continuous opacification of the tract. Increase in contrast medium volume leads to higher renal parenchymal enhancement as well as to an increased continuous opacification of the urinary tract. Decrease in contrast medium volume cannot be compensated for by oral hydration in terms of parenchymal enhancement.

Von der MDCT-Technik und ihrer mittlerweile weiten Verfugbarkeit hat auch die Bildgebung bei Nieren- und Hochdruckkrankheiten profitiert. In zunehmendem Mase kann die MDCT Indikationen der (invasiven) konventionellen Angiographie ubernehmen und die i.v.-Urographie vollstandig ersetzen. Zur Minimierung der Gesamtstrahlendosis ist fur jede Fragestellung ein masgeschneidertes Untersuchungsprotokoll anzuwenden. Soweit sinnvoll sollten Niedrigdosisprotokolle (z. B. zur Diagnostik der Urolithiasis) zur Anwendung kommen. Durch die Verbesserung der longitudinalen Auflosung (z-Achse) und der resultierenden isotropen Voxel stehen vielfaltige Moglichkeiten der Bildrekonstruktion zur Verfugung. Die Anfertigung von multiplanaren Rekonstruktionen, dunneren Schichten und/oder 3D-Rekonstruktionen kann in vielen Fallen hilfreich bei der Diagnosefindung sein. Grundlage einer aussagekraftigen Untersuchung ist nicht zuletzt eine gute Kommunikation zwischen klinisch tatigen Arzten und Radiologen.

A review of the literature on the diagnostic accuracy of multidetector computed tomography urography (MDCTU) and intravenous urography (IVU) reveals a lack of comparative studies. However, the available data indicate that MDCTU has a high diagnostic accuracy. MDCTU is also preferred by patients, as it does not require bowel preparation. Full acceptance of this technique by the urologist will depend on optimisation of the communication process with a careful selection of the images to be transmitted. MDCTU has a higher cost than IVU but allows some diagnostic algorithms to be simplified. The real concern potentially limiting the widespread use of MDCTU is its higher radiation dose when compared with IVU. Although low-dose protocols will soon be available, a substantial dose reduction can already be achieved by tailoring MDCTU to the clinical problem rather than using a standardised approach. Our analysis indicates that IVU will definitely lose any residual role it may still have. In our department, the last urographic procedure was performed in May 2006.

Excellent contrast resolution and lack of ionizing radiation make magnetic resonance urography (MRU) a promising technique for noninvasively evaluating the entire urinary tract. While MRU currently lags behind CT urography (CTU) in spatial resolution and efficiency, new hardware and sequence developments have contributed to a resurgence of interest in MRU techniques. By combining unenhanced sequences with multiphase contrast-enhanced and excretory phase imaging, a comprehensive assessment of the kidneys, ureters, bladder, and surrounding structures is possible with image quality rivaling that obtained with other techniques. At the same time, formidable challenges remain to be overcome and further clinical validation is necessary before MRU can replace other forms of urography. In this article, we demonstrate the current potential of MRU to demonstrate a spectrum of urologic pathology involving the kidneys, ureters, and bladder while discussing the limitations and current status of this evolving technique.

The aim was to develop clinical guidelines for multidetector computed tomography urography (CTU) by a group of experts from the European Society of Urogenital Radiology (ESUR). Peer-reviewed papers and reviews were systematically scrutinized. A summary document was produced and discussed at the ESUR 2006 and ECR 2007 meetings with the goal to reach consensus. True evidence-based guidelines could not be formulated, but expert guidelines on indications and CTU examination technique were produced. CTU is justified as a first-line test for patients with macroscopic haematuria, at high-risk for urothelial cancer. Otherwise, CTU may be used as a problem-solving examination. A differential approach using a one-, two- or three-phase protocol is proposed, whereby the clinical indication and the patient population will determine which CTU protocol is employed. Either a combined nephrographic-excretory phase following a split-bolus intravenous injection of contrast medium, or separate nephrographic and excretory phases following a single-bolus injection can be used. Lower dose (CTDIvol 5-6 mGy) is used for benign conditions and normal dose (CTDIvol 9-12 mGy) for potential malignant disease. A low-dose (CTDIvol 2-3 mGy) unenhanced series can be added on indication. The expert-based CTU guidelines provide recommendations to optimize techniques and to unify the radiologist's approach to CTU.

For decades, traditional IVU studies have been the mainstay in the investigation of urinary tract calculi and obstruction. However, they have been largely superseded by non-contrast CT in the present day. The use of contrast material further expands the utility of CT in the evaluation of urinary tract disease, allowing detection and characterization of renal masses and urothelial lesions. In this review article, we discuss the development and current role of CT urography as the complete imaging investigation in the genitourinary system. Conventional multiphasic protocols and split-bolus techniques for radiation dose reduction are considered. We then focus on how recent technological advances have allowed dual-energy CT to play a complementary role in CT evaluation of the genitourinary system, allowing stone and renal mass characterization, as well as creation of virtual unenhanced datasets. The use of associated post-processing software applications in the clinical context is illustrated.

The purpose of this study was to assess the role of multi-detector row CT urography (MDCTU), on a 16-row CT scanner in the evaluation of patients with painless hematuria, with emphasis placed in the detection of urothelial tumors. We retrospectively reviewed the MDCT urographies of 75 patients, referred for painless hematuria. The CT protocol included unenhanced images, obtained with a detector configuration of 16x1.5 mm and pitch of 1.2, nephrographic and excretory-phase images, obtained with a detector collimation of 16x0.75 mm and pitch of 1.2. Axial and coronal reformatted images were evaluated. Three-dimensional reformation of the excretory-phase images was performed using the volume-rendering technique. The standard of reference included clinical and imaging follow-up, cystoscopic, surgical and histologic findings. In 55 (73%) of 75 patients, the cause of hematuria was identified on MDCTU; the most common cause was urothelial cancer, including seven tumors with a diameter equal or smaller than 0.5 cm in diameter. Sixteen-row MDCTU provided satisfactory results in the investigation of patients with painless hematuria. The main advantage of the technique is its ability to detect uroepithelial malignancies. European Radiology

A novel ureter phantom was developed for investigations of image quality and dose in CT urography. The ureter phantom consisted of a water box (14 cm x 32 cm x 42 cm) with five parallel plastic tubes (diameter 2.7 mm) filled with different concentrations of contrast media (1.88-30 mg iodine/ml). CT density of the tubes and noise of the surrounding water were determined using two multidetector scanners (Philips MX8000 with four rows, Siemens Sensation 16 with 16 rows) with varying tube current-time product (15-100 mAs per slice), voltage (90 kV, 100 kV, 120 kV), pitch (0.875-1.75), and slice thickness (1 mm, 2 mm, 3.2 mm). Contrast-to-noise ratio as a parameter of image quality was correlated with dose (CTDI) and was compared with image evaluation by two radiologists. The CT densities of different concentrations of contrast media and contrast-to-noise ratio were significantly higher when low voltages (90 kV versus 120 kV, 100 kV versus 120 kV) were applied. Smaller slice thickness (1 mm versus 2 mm) did not change CT density but decreased contrast-to-noise ratio due to increased noise. Contrast phantom studies showed favourable effects of low tube voltage on image quality in the low dose range. This may facilitate substantial dose reduction in CT urography.

Imaging of the urinary tract with current computed tomography (CT) technology allows for the rapid detection of both symptomatic and asymptomatic stone disease. Unenhanced CT is more accurate and can be obtained more rapidly than intravenous urogram and has become the imaging modality of choice for the evaluation of nephrolithiasis.

Although patients with bladder cancer are at increased risk of developing upper tract urothelial carcinoma (UTUC), the overall incidence remains low. Serial CT urography is routinely performed in these patients to rule out UTUC, but its clinical value and cost-effectiveness are questionable, especially in patients with non-muscle-invasive disease.