The diagnostic value of magnetic resonance urography for detecting ureteric obstruction: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the diagnostic accuracy of magnetic resonance urography (MRU) and determine its value for detecting ureteric obstruction. METHODS: The electronic databases, including PubMed, Embase and the Cochrane library, were systematically searched for studies published throughout September 2018. The summary of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and receiver operating characteristic (ROC) curves was assessed to evaluate the diagnostic accuracy of MRU. Subgroup analyses were conducted based on the mean age of the included patients (adults or children). RESULTS: Eight studies with a total of 594 patients were included. The summary of the sensitivity and specificity of MRU for diagnosing ureteric obstruction was 0.94 and 0.87, respectively. Furthermore, the pooled PLR and NLR were 7.33 and 0.07, respectively. The DOR of MRU for detecting ureteric obstruction was 95.12. In addition, the summary of the area under the ROC of MRU was 0.96. Finally, the specificity, PLR and area under the ROC of MRU for diagnosing ureteric obstruction in adults were higher than children, while the sensitivity of MRU in adults was lower than children. CONCLUSIONS: These findings suggested a relatively high diagnostic value of MRU for detecting ureteric obstruction. Moreover, the diagnostic accuracy of MRU in adults was higher than in children. KEY MESSAGE Magnetic resonance urography (MRU) in detecting ureteric obstruction has relatively better sensitivity, specificity, PLR, NLR, DOR and AUC. The diagnostic value, including specificity, PLR and AUC of MRU in adults, was higher than in children, while the sensitivity of MRU in adults was lower than in children.

Image quality and pathology assessment in CT Urography: when is the low-dose series sufficient?

BACKGROUND: Our aim was to compare CT images from native, nephrographic and excretory phases using image quality criteria as well as the detection of positive pathological findings in CT Urography, to explore if the radiation burden to the younger group of patients or patients with negative outcomes can be reduced. METHODS: This is a retrospective study of 40 patients who underwent a CT Urography examination on a 192-slice dual source scanner. Image quality was assessed for four specific renal image criteria from the European guidelines, together with pathological assessment in three categories: renal, other abdominal, and incidental findings without clinical significance. Each phase was assessed individually by three radiologists with varying experience using a graded scale. Certainty scores were derived based on the graded assessments. Statistical analysis was performed using visual grading regression (VGR). The limit for significance was set at p = 0.05. RESULTS: For visual reproduction of the renal parenchyma and renal arteries, the image quality was judged better for the nephrogram phase (p < 0.001), whereas renal pelvis/calyces and proximal ureters were better reproduced in the excretory phase compared to the native phase (p < 0.001). Similarly, significantly higher certainty scores were obtained in the nephrogram phase for renal parenchyma and renal arteries, but in the excretory phase for renal pelvis/calyxes and proximal ureters. Assessment of pathology in the three categories showed no statistically significant differences between the three phases. Certainty scores for assessment of pathology, however, showed a significantly higher certainty for renal pathology when comparing the native phase to nephrogram and excretory phase and a significantly higher score for nephrographic phase but only for incidental findings. CONCLUSION: Visualisation of renal anatomy was as expected with each post-contrast phase showing favourable scores compared to the native phase. No statistically significant differences in the assessment of pathology were found between the three phases. The low-dose CT (LDCT) seems to be sufficient in differentiating between normal and pathological examinations. To reduce the radiation burden in certain patient groups, the LDCT could be considered a suitable alternative as a first line imaging method. However, radiologists should be aware of its limitations.

Determination of optimal imaging settings for urolithiasis CT using filtered back projection (FBP), statistical iterative reconstruction (IR) and knowledge-based iterative model reconstruction (IMR): a physical human phantom study.

OBJECTIVE: The purpose of this study was to compare CT image quality for evaluating urolithiasis using filtered back projection (FBP), statistical iterative reconstruction (IR) and knowledge-based iterative model reconstruction (IMR) according to various scan parameters and radiation doses. METHODS: A 5 × 5 × 5 mm(3) uric acid stone was placed in a physical human phantom at the level of the pelvis. 3 tube voltages (120, 100 and 80 kV) and 4 current-time products (100, 70, 30 and 15 mAs) were implemented in 12 scans. Each scan was reconstructed with FBP, statistical IR (Levels 5-7) and knowledge-based IMR (soft-tissue Levels 1-3). The radiation dose, objective image quality and signal-to-noise ratio (SNR) were evaluated, and subjective assessments were performed. RESULTS: The effective doses ranged from 0.095 to 2.621 mSv. Knowledge-based IMR showed better objective image noise and SNR than did FBP and statistical IR. The subjective image noise of FBP was worse than that of statistical IR and knowledge-based IMR. The subjective assessment scores deteriorated after a break point of 100 kV and 30 mAs. CONCLUSION: At the setting of 100 kV and 30 mAs, the radiation dose can be decreased by approximately 84% while keeping the subjective image assessment. ADVANCES IN KNOWLEDGE: Patients with urolithiasis can be evaluated with ultralow-dose non-enhanced CT using a knowledge-based IMR algorithm at a substantially reduced radiation dose with the imaging quality preserved, thereby minimizing the risks of radiation exposure while providing clinically relevant diagnostic benefits for patients.

Ultra low-dose VCUG in children using a modern flat detectorunit.

OBJECTIVES: To assess dose area products (DAP) and effective doses (ED) of voiding cystourethrography (VCUG) in children using optimized protocols on a modern flat detector unit. METHODS: DAP and ED were evaluated in 651 VCUG (316 girls, median age: 2.25 years) between 2009 and 2012. DAP was analyzed in relation to patient characteristics (gender, age, presence of pathological findings) and experience of performing physician using analysis of variance. ED values were estimated using adapted conversion factors from the literature. Diagnostic image quality was validated by two experienced physicians using a 3-point scale. RESULTS: Median DAP/ED was 0.5 cGycm(2)/4.56 µSv (boys: 0.6 cGycm(2)/6.16 µSv; girls: 0.4 cGycm(2)/3.54 µSv). In 300 studies without pathologic findings DAP was 0.35 cGycm(2), whereas 351 studies with pathologic findings had a median DAP of 0.7 cGycm(2). No significant relationship between DAP and experience of radiologist was observed. Image validation resulted in an overall good to excellent rating. CONCLUSIONS: DAP and ED can be markedly reduced in paediatric VCUG performed with optimized protocols on modern equipment without a noticeable decrease in diagnostic image quality. KEY POINTS: • Voiding cystourethrography is a comprehensive examination in diagnosing vesicoureteral reflux (VUR). • Radiation reduction is achieved in VCUG through modern equipment and optimized protocols. • Low-dose VCUG is possible without noticeable decrease in diagnostic image quality.

Diagnostic imaging of lower urinary tract disease.

Diagnostic imaging is routinely performed in small animals with lower urinary tract disease. Survey radiographs allow identification of radiopaque calculi, gas within the urinary tract, and lymph node or bone metastases. Cystography and urethrography remain useful in the evaluation of bladder or urethral rupture, abnormal communication with other organs, and lesions of the pelvic or penile urethra. Ultrasonography is the modality of choice for the diagnosis of most disorders. Computed tomography and magnetic resonance imaging are useful in evaluating the ureterovesical junction and intrapelvic lesions, monitoring the size of lesions, and evaluating lymph nodes and osseous structures for metastases.

Computed tomography urography 1: techniques and technology.

Contrast-enhanced computed tomography urography has become possible because of the development of multidetector technology, which has evolved to try and increase its diagnostic efficacy and reduce the radiation exposure. This review highlights important aspects of computed tomography urography as an imaging technique.

CT of urolithiasis: comparison of image quality and diagnostic confidence using filtered back projection and iterative reconstruction techniques.

RATIONALE AND OBJECTIVES: To compare the image quality and diagnostic confidence of low-dose computed tomography (CT) of urololithiasis using filtered back projection (FBP) and iterative reconstruction techniques (IRT). MATERIALS AND METHODS: A 4.8 × 4.3 × 5.2 mm(3) uric acid ureteral stone was placed inside an anthropomorphic Alderson phantom at the pelvic level. Fifteen scans were performed on a 64-row dual-source CT system using different tube voltages (80, 100, and 120 kV) and current-time products (8, 15, 30, 70, and 100 mAs). Image reconstruction using FBP and IRT (iterative reconstruction in image space) resulted in 30 data sets. Objective image quality was evaluated by noise measurements. Effective doses were estimated for each data set with use of an established dosimetry program. Subjective image quality and confidence level were rated by two radiologists. RESULTS: Noise was systematically lower for images reconstructed with IRT compared to FBP (55 ± 30 vs 65 ± 26 Hounsfield units; P = .004) for volume CT dose index values above about 0.6 mGy (or an effective dose of about 0.4 mSv for both sexes). For the 14 scans rated to have diagnostic image quality, the estimated effective doses ranged from 0.3 to 2.5 mSv for males and from 0.4 to 3.1 mSv for females. Subjective image quality and diagnostic confidence for IRT was not significantly better than those for FBP. CONCLUSIONS: In a phantom study for CT of urolithiasis, IRT improves objective image quality compared to FBP above a certain dose threshold. However, this does not translate into improved subjective image quality or a higher degree of confidence for the diagnosis of high-contrast urinary stones.

Influence of endourological devices on 3D reconstruction image quality using the Uro Dyna-CT.

PURPOSE: The urological Dyna-CT (Uro Dyna-CT) was established in clinical use for classical imaging as well as for interventional surgery. To evaluate whether irradiation artefacts may occur during interventional surgery, we analysed the impact of different instruments on 3D reconstruction in the Uro Dyna-CT. MATERIALS AND METHODS: Ten different endourological instruments [ureterorenoscope (URS)-fibrescope, percutaneous nephrolithotomy (PCNL) working sheath] and accessory equipments such as ureteral catheter, guide wires and stents (DJ, MJ) were introduced in a porcine renal pelvis either retrograde via the ureter or transparenchymally. Subsequently, digital fluoroscopy, standard X-ray and an Uro Dyna-CT were performed. Three colleagues evaluated the image quality independent from each other. RESULTS: There were basically no limitations regarding image quality in digital fluoroscopy and standard X-ray. In the Uro Dyna-CT, only with the URS fiberscope and the PCNL working sheath, small artefacts and irradiations were detected, whereas ureteric catheter with and without wire, as well as the hydrophilic guide wire, showed no artefacts at all. The remaining material demonstrated minimal artefacts, which did not affect the image quality. CONCLUSIONS: The Uro Dyna-CT can be used for all interventional endourological procedures using the common armamentarium and instruments without significant limitation of image quality. There are only minor limitations according a PCNL working sheath and the rigid URS. These instruments should be removed out of the examination field before performing the computed tomography and be replaced afterwards by using a safety wire.

[The urological Dyna-CT. Urological cross-sectional imaging on a newly developed urological intervention table]. / Das urologische Dyna-CT. Urologische Schnittbildgebung auf einem neu entwickelten urologischen Interventionstisch.

BACKGROUND: The development of a new urological intervention table now enables the application of an Artis zee ceiling Dyna-CT (Siemens, Erlangen, Germany) for interventional cross-sectional imaging and 3-D reconstruction of the urinary tract in the prone and supine positions (urological Dyna-CT). MATERIALS AND METHODS: We tested the feasibility of the urological Dyna-CT with the newly developed urological intervention table. The system was moved five times to enable 3-D reconstruction of the urinary tract of a test person in the prone and in supine positions. RESULTS: Handling of the free floating table is easily possible during the intervention. We found no limitation of imaging system movement in any position of the test person. CONCLUSION: Apart from standard urological imaging such as fluoroscopy, intravenous pyelography or plain abdominal X-ray the urological Dyna-CT enables further imaging of the urinary tract. Fluoroscopy sequences can be stored as videos, and 3-D reconstructions of the urinary tract are possible with permanent patient access for any intervention. Extensive tests led to the technical approval of the system in urology.

Dual-energy CT with single- and dual-source scanners: current applications in evaluating the genitourinary tract.

Several promising clinical applications for dual-energy computed tomography (CT) in genitourinary imaging have been reported. Dual-energy CT not only provides excellent morphologic detail but also can supply material-specific and quantitative information that may be particularly useful in genitourinary imaging. Dual-energy CT has unique capabilities for characterizing renal lesions by quantifying iodine content and helping identify the mineral contents of renal stones, information that is important for patient care. Virtual unenhanced images reconstructed from dual-energy CT datasets can be useful for detecting calculi within the iodine-filled urinary collecting system, potentially reducing the need for an unenhanced scanning phase at CT urography. Although the underlying principles of dual-energy CT are the same regardless of scanner type, single-source dual-energy scanners with fast kilovoltage switching differ from dual-source dual-energy scanners both in image data acquisition and in processing methods; an understanding of these differences may help optimize dual-energy CT genitourinary protocols. Dual-energy CT performed with a dual-source scanner or with a single-source scanner with fast kilovoltage switching also has some important limitations. Further advances in scanning protocols and refinement of processing techniques to reduce image noise may lead to more widespread use of dual-energy CT.

Digital tomosynthesis--a new lease of life for the intravenous urogram?

OBJECTIVES: Digital tomosynthesis is a new digital technique based on conventional X-ray tomography. It acquires multiple low-dose projections during a single sweep of the X-ray tube, which are reassembled to provide high-resolution slices at different depths. Suggested uses include visualisation of pulmonary nodules, mammography, angiography, dental imaging and delineation of fractures. This study aims to evaluate its potential role as part of an intravenous urogram (IVU) by assessing the diagnostic quality in imaging the kidneys in clinical practice. METHODS: 100 renal units from consecutive traditional IVU studies were retrospectively compared with 101 renal units imaged using digital tomosynthesis. These were scored for visualisation of the renal outline and collecting system, presence of a renal cyst or mass and overall diagnostic quality. Radiation doses were calculated. RESULTS: 46.5% of traditional IVUs were found to be of diagnostic quality. The IVUs with digital tomosynthesis were of diagnostic quality in 95.5%. This represents a highly statistically significant difference (p<0.0001). There was also a statistically significant dose reduction, with a mean reduction of 56%, for the samples studied. CONCLUSION: Digital tomosynthesis offers a significant increase in the percentage of diagnostic quality tests for assessing renal pathology, compared with traditional IVU, and significantly reduces radiation. It also offers considerable advantages in ease and speed of imaging. For these reasons, in any situation where IVU is still being used to assess the kidneys, digital tomosynthesis is likely to be of considerable benefit in improving diagnostic quality.

Urine sensor device for fluoroscopy time reduction in pediatric voiding cystourethrography.

PURPOSE: We evaluated the feasibility of a using urine sensor for voiding cystourethrography (VCUG) and its implications for fluoroscopy time reduction. MATERIALS AND METHODS: Institutional Review Board approved the study protocol. Study population included children less than 5 years old referred to our institution for VCUG. Patients with known vesicoureteral reflux or any pacing device were excluded from the study. The urine sensor consists of an electrode that senses the fluid, an electrical circuit and an indicator to provide visual signal. The urine sensor electrode was placed on the medial thigh in the proximity of the catheter close to the urethral opening, but without direct contact to it. A standard VCUG examination was performed with retrograde filling of the urinary bladder. Once the bladder was full, fluoroscopy of the voiding stage was initiated when the indicator blinked. Peak kV and fluoroscopy time were recorded. RESULTS: Seven patients underwent VCUG with urine sensor and 22 patients without urine sensor. The urine sensor provided a reliable indication of voiding onset. The fluoroscopy time was significantly shorter with urine sensor use (1.99 min) than without urine sensor use (4.33 min) (p=0.001). In patients with normal VCUG, fluoroscopy time was also significantly shorter with urine sensor use (2.13 min) than without urine sensor use (4.39 min) (p<0.001). CONCLUSION: VCUG studies with the help of the urine sensor are feasible and its use may result in significant reduction in fluoroscopy time.

MR imaging guided percutaneous nephrostomy using a 1.0 Tesla open MR scanner.

PURPOSE: The purpose of this study was to assess the safety and feasibility of MR-guided percutaneous nephrostomy (PCN) using a 1.0 Tesla open MR-scanner with fast dynamic imaging. METHODS: Twenty-five patients with failed ultrasonographic insertion due to various reasons, such as nondilated pelvic systems, obesity, and parapelvic cysts, were investigated. RESULTS: In summary, 35 nephrostomy procedures were performed; 15 patients received monolateral and 10 patients bilateral placement. For guidance and monitoring, fast T2w single-shot-TSE imaging in a fluoroscopic mode in two orthogonal planes was used to guide the insertion of the needle into a predetermined calyx in freehand technique. Nephrostomy was inserted via Seldinger-technique. The procedure was regarded as technically successful if the placement of the catheter provided adequate drainage of the collecting system. Demonstration of an intrapelvic position of the catheter was verified by antegrade pyelography using T1w GRE imaging after injection of diluted Gd-DTPA into the collecting system. Under the experimental conditions of the study, the time for the complete procedure was 30 (range, 23-39) min. Puncture and placement of the nephrostomy was performed in 5 (range, 3-10) min on average. CONCLUSIONS: Our results demonstrated a pinpoint puncture of the pelvic system in a reasonable timeframe even in patients with difficult conditions, suggesting that MR-guided PCN using the open 1 Tesla system can be assessed as a reliable, fast, and safe method applicable in the clinical routine setting.

Optimisation of tube voltage for conventional urography using a Gd2O2S:Tb flat panel detector.

With the increasing use of computed tomography (CT) for urography examinations, the indications for 'conventional' projection urography have changed and are more focused on high-contrast details. The purpose of the present study was to optimise the beam quality for urography examinations performed with a Gd(2)O(2)S:Tb flat-panel detector for the new conditions. Images of an anthropomorphic phantom were collected at different tube voltages with a CXDI-40G detector (Canon Inc., Tokyo, Japan). The images were analysed by radiologists and residents in a visual grading characteristics (VGCs) study. The tube voltage resulting in the best image quality was 55 kV, which therefore was selected for a clinical study. Images from 62 patients exposed with either 55 or 73 kV (original tube voltage) at constant effective doses were included. The 55-kV images underwent simulated dose reduction to represent images collected at 80, 64, 50, 40 and 32 % of the original dose level. All images were included in a VGC study where the observers rated the visibility of important anatomical landmarks. For images collected at 55 kV, an effective dose of approximately 85 % resulted in the same image quality as for images collected at 73 kV at 100 % dose. In conclusion, a low tube voltage should be used for conventional urography focused on high-contrast details. The study indicates that using a tube voltage of 55 kV instead of 73 kV for a Gd(2)O(2)S:Tb flat-panel detector, the effective dose can be reduced by approximately 10-20 % for normal-sized patients while maintaining image quality.

[Sonographic bladder volumetry in children: comparison of conventional B-mode sonography and automatic volumetry with a handheld scanning device without imaging]. / Sonografische Harnblasenvolumetrie bei Kindern: vergleichende Beurteilung von konventioneller B-Bild-Sonografie und automatisierter Volumetrie mit einem sonografischen Handgerät ohne Bildgebung.

PURPOSE: Evaluation of a handheld sonographic tool for the automatic estimation of bladder volume in comparison with conventional sonography in children under clinical conditions. MATERIALS AND METHODS: 139 children (age: 30 days - 17 years) were examined with both conventional sonography and the handheld scanning device BVI 6200. For conventional sonography two different formulas were used to calculate the bladder volume. RESULTS: The mean error of the three methods was 22.4 % for the handheld tool, 37.4 % for the most frequently used prolate ellipsoid formula in conventional sonography, and 23 % for an alternative formula recommended in the literature. In 19 cases the first automated sonography scan showed a false-negative result (empty bladder), while the automatically calculated volumes were between 17 and 60 ml in 5 cases of empty bladder. In one of these cases a megaureter and in another an ovarian cyst were detected by conventional ultrasound. CONCLUSION: Since pathologies are not visualized and can be misinterpreted as a nonempty bladder, the automated method should only be used in follow-up studies. In every case automated volumetry should be performed repeatedly to avoid false-negative results.

Low-dose MDCT urography: feasibility study of low-tube-voltage technique and adaptive noise reduction filter.

OBJECTIVE: The purpose of this study was to investigate the feasibility of performance of MDCT urography with low tube voltage and an adaptive noise reduction filter. SUBJECTS AND METHODS: Thirty-one patients underwent excretory phase (300 seconds after administration of 100 mL of iopamidol) 40-MDCT of the urinary tract at 120 and 80 kVp. The 80-kVp images were postprocessed with an adaptive noise reduction filter. Using a 3-point scale for homogeneity of the urinary tract and sharpness of contour, streak artifacts, and overall image quality, two radiologists evaluated coronal multiplanar reconstruction images generated from 120-kVp, unfiltered 80-kVp, and filtered 80-kVp images. Attenuation values of the abdominal aorta, renal pelvis, renal cortex, psoas muscle, vertebral body, and retroperitoneal fat and image noise of the psoas muscle were measured. The effective radiation dose was estimated for each patient. RESULTS: At visual evaluation of images of the upper urinary tract, the quality of filtered 80-kVp images was comparable with that of 120-kVp images. At evaluation of images of the lower urinary tract, however, filtered 80-kVp images were of inferior quality. Except for those of fat tissue, attenuation values were significantly higher on 80-kVp than on 120-kVp images (paired Student's t test, p < 0.01). Noise values did not differ significantly between 120- and filtered 80-kVp images (Dunnett test, p = 0.37). The mean effective doses for 120- and 80-kVp scans were 7.0 and 2.9 mSv. CONCLUSION: MDCT urography is feasible with a low-tube-voltage technique and an adaptive noise reduction filter. The technique allows reduction in radiation dose without marked degradation of image quality and can be used in clinical assessment of the renal collecting system and upper ureter. For evaluation of the pelvic ureter and urinary bladder, however, image quality is not sufficient, and a compensatory increase in tube current may be necessary.

Urethrography in the male: the clamp method.

BACKGROUND: Retrograde urethrography is considered the gold standard for evaluating stenosis or urethral disease. PURPOSE: To describe the clamp method for optimizing retrograde urethrography (RUG) using a perfected device and a drip infusion system. material and methods: RUG was performed in 42 patients with a mean age of 63.4+/-16.5 years suspected of having urethral stenosis. The modifications to the device are shown, and the steps of the technique described. The intensity of pain from both catheterization and external compression was measured on a visual analog scale (VAS). RESULTS: All the RUG examinations were conducted satisfactorily. The use of the drip infusion system enabled visualization of the posterior urethra in 97.6% of cases, and bladder repletion was achieved in 95.2% of cases. The urethrograms revealed images of stenosis in 31 patients. With catheterization the mean pain intensity registered by VAS was 0.7+/-0.6 (SD), whereas with external compression the mean pain intensity was 0.06+/-0.02 (SD). CONCLUSION: The clamp method and drip infusion system used in this study are efficient and reduce patient discomfort. The procedure makes it possible to assess cases with stenosis close to the meatus that are difficult to manage with the conventional method.

What technical barriers exist for real-time fluoroscopic and video image overlay in robotic surgery?

BACKGROUND: A hypothetical advantage of the da Vinci console is its ability to integrate multiple visual data sources. Current platforms for augmented reality surgery fuse pre-operative radiographic studies but are limited with their ability to update with intra-operative imaging. The aim of our study was to evaluate the feasibility of real-time radiographic image overlay with current technology. METHODS: S-video composite output from a fluoroscopic C-arm was superimposed onto the video output of the da Vinci device. Image superimposition disparity measurements were evaluated in a bench model. The feasibility of robotic dissection assisted by real-time cholangiogram and intravenous pyelogram was evaluated. RESULTS: Image alignment resulted in a radiographic blind spot and image disparity with severely limited application in an in vivo model. CONCLUSIONS: External collisions of the robotic device and visual disparity in multiple planes negate the current implementation of fluoroscopic overlay and will require more elegant methods of computer-assisted registration.