Sonographic twinkling artifact for renal calculus detection: correlation with CT.

King W., Kimme-Smith C., Winter J.

A series of in vitro experiments evaluated the effects of intervening tissue, B-mode processing algorithms, stone chemical composition, stone size, and reverberation artifacts on the acoustic shadows of renal stones. Stone size was found to be the most important variable; intervening tissue and focal zone placement also affected imaging. Reverberation artifacts may fill in an acoustic shadow, but can still provide information. The survey algorithm produced slightly clearer shadows than the static storage algorithm. Gray-scale map changes, increased power, and chemical composition of calculi did not affect shadowing.

Rahmouni A., Bargoin R., Herment A., Bargoin N., Vasile N.

PURPOSE To investigate a new color Doppler ultrasound (US) artifact that manifested as a rapidly changing mixture of red and blue behind a strongly reflecting structure. MATERIALS AND METHODS In 140 consecutive patients with parenchymal calcifications seen at US, the presence of color signal was assessed in calcified areas relative to adjacent noncalcified tissue. The artifact, called the twinkling color artifact, was stimulated with various strongly reflecting structures immersed in still water. RESULTS The artifact was found in 42 parenchymal calcifications. In vitro experiments showed that the twinkling artifact was present in granular structures, whereas no color signal was noted in smooth surfaces. The "twinkling sign" appeared to be generated by a strongly reflecting medium composed of individual reflectors. CONCLUSION The presence of a color signal close to calcifications should be interpreted with caution, and a flow spectrum should always be recorded to eliminate the twinkling artifact.

Kamaya A., Tuthill T., M. Rubin J.

The objective of our study was to evaluate the color Doppler sonographic effect known as twinkling artifact.Struvite (ammonium magnesium phosphate) stone fragments, wire mesh, and a flat surface were scanned in a water bath with a sonography scanner using a high-frequency linear array probe fixed in a ring clamp. Pulse repetition frequency, color-write priority, gray-scale gain, and spectral Doppler gain were varied. Color and spectral Doppler modes were used.Twinkling artifact and spectral broadening were seen most intensely behind struvite stone fragments, and both were seen more strongly behind wire mesh with greater surface roughness than behind wire mesh with less surface roughness or a flat surface. The appearance of the twinkling artifact is highly dependent on machine settings. System noise measured on a flat surface generates a band-limited Doppler shift on spectral displays with a mean frequency shift of 0 Hz and a mean (+/- SD) absolute fluctuation of 86 +/- 10 Hz over a pulse repetition frequency range of 1250-10,000 Hz. Rough surfaces increase the spectral bandwidth.The appearance of the twinkling artifact is highly dependent on machine settings and is likely generated by a narrow-band, intrinsic machine noise called phase (or clock) jitter. Surface roughness secondarily broadens the noise spectrum. With a strongly reflecting, rough surface such as a renal stone, the high amplitude, broadband signal appears as random motion in color Doppler sonography. Understanding of the twinkling artifact may result in better use of its clinical appearance.

Lee J.Y., Kim S.H., Cho J.Y., Han D.

The purpose of this study was to determine whether color and power Doppler twinkling artifacts could be considered an additional diagnostic sonographic feature of urinary stones.A prospective study was performed in 32 patients with 20 renal stones and 16 ureteral stones to assess how often urinary stones show twinkling artifacts on Doppler sonography. Gray-scale images and color, power, and spectral Doppler images were obtained in all patients. All sonographic examinations were performed with a 3.5- or 5-MHz curvilinear phased array probe. The images were then analyzed for the presence, appearance, and intensity of the artifacts. Phantom experiments were performed with various kinds of urinary stones with high-megahertz linear phased array probes. The effects on the artifacts of the composition of the stones, of the Doppler velocity scale, and of the focal zone were investigated.Thirty (83%) of 36 urinary stones showed color and power Doppler twinkling artifacts, which appeared as a rapidly changing color complex seen persistently behind stones like a comet's tail. Twenty-two of 30 stones with the twinkling artifacts showed strong intensity artifacts. Spectra with saturated amplitude were obtained from all 30 stones showing color Doppler artifacts. In phantom experiments, the artifacts originated from all stones. The velocity range did not affect the artifacts, whereas focal zone did.Color Doppler twinkling artifacts from urinary stones occur frequently and may be considered an additional sonographic feature of urinary stones. The observation of these artifacts may be helpful in determining the presence of urinary stones.

Tack D., Sourtzis S., Delpierre I., de Maertelaer V., Gevenois P.A.

This study is designed to assess the intraobserver and interobserver agreements and the diagnostic performances of low-dose unenhanced multidetector CT (MDCT) in patients with suspected renal colic.The study included 106 patients who underwent unenhanced MDCT with 4 x 2.5 mm collimation, 120 kVp, 30 mAs, and, if necessary, additional focused acquisitions at 60 or 120 mAs on areas with an equivocal ureteral stone or with significant image noise. The effective radiation dose was computer-simulated with software based on the Monte Carlo model and International Commission on Radiological Protection recommendations. CT scans were archived and independently reviewed by three radiologists during two interpretation sessions on a workstation with three dimensions functions. Intraobserver and interobserver agreements were calculated with the kappa statistics. Accuracy for detection of ureteral stone on low-dose MDCT was calculated by comparison with combined clinical (stone passage), surgical (stone retrieval, extracorporeal shock wave lithotripsy), biologic (urinalysis, urine culture), and other imaging (excretory urography, standard-dose MDCT, follow-up sonography, and abdominal radiography) findings or by evidence for an alternative diagnosis.Ureteral stones were present in 38 (36%) of 106 patients. Thirty-six of 38 ureteral stones were detected by low-dose MDCT. From reviewer to reviewer, the number of true-positive, false-positive, true-negative, and false-negative findings ranged, respectively, from 34 to 36, 1 to 4, 64 to 68, and 2 to 4. The corresponding sensitivity, specificity, and accuracy ranged from 89.5% to 94.7%, from 94.1% to 100%, and from 93.4% to 98.1%, respectively. The intraobserver and interobserver agreements were excellent, with kappa values ranging from 0.87 to 0.98. In 13 patients, an alternative diagnosis explaining the patient's symptoms was proposed by all reviewers using images obtained at 30 mAs. No additional or alternative diagnosis was found at standard dose. At 30 mAs, the mean effective dose was 1.2 mSv in men and 1.9 mSv in women. Additional acquisitions at 60 mAs, all focused on the lower pelvis, were acquired in 20 patients, but the corresponding images were needed by the reviewers for only six of them. The acquisitions at 60 mAs were responsible for an additional mean effective dose of 0.5 in men and 0.8 mSv in women.Our study shows that low-dose unenhanced MDCT is appropriate for the diagnosis of ureteral stones, and that it provides excellent intraobserver and interobserver agreements and does not obscure alternative diagnoses.

Worcester E.M., Coe F.L.

A 43-year-old man presents for evaluation of recurrent kidney stones. He passed his first stone 9 years earlier and has had two additional symptomatic stones. Analysis of the first and the last stones showed that they contained 80% calcium oxalate and 20% calcium phosphate. Analysis of a 24-hour urine collection while the patient was not receiving medications revealed a calcium level of 408 mg (10.2 mmol), an oxalate level of 33 mg (367 μmol), and a volume of 1.54 liters; the urine pH was 5.6. The patient had been treated with 20 to 40 mmol of potassium citrate daily since he passed his first stone. How should he be further evaluated and treated?

Jin D.H., Lamberton G.R., Broome D.R., Saaty H., Bhattacharya S., Lindler T.U., Baldwin D.D.

We determined the effect of reconstructed section width on sensitivity and specificity for detecting renal calculi using multidetector row computerized tomography.Three to 5 renal stones 2 to 4 mm in size were randomly placed into 14 human cadaveric kidneys and scanned by 16-row detector computerized tomography at 1.25 mm collimation and identical scanning parameters. After acquisition images were reconstructed with a section width of 1.25, 2.5, 3.75 and 5.0 mm, and reviewed independently by 2 blinded radiologists. Comparisons of sensitivity and specificity between different section widths were assessed with the McNemar test and Cochran's Q statistics.Specificity was not significantly affected by section width (94.6% to 97.7%). In contrast, sensitivity increased as stone size increased and as section width decreased. Sensitivity to detect all stones was 80.7%, 80.7%, 87.7% and 92.1% for 5.0, 3.75, 2.5 and 1.25 mm section widths, respectively. Interobserver agreement for stone detection was excellent (kappa 0.858). Although the 2.0 mm stone detection rate improved with thinner section widths (79.4% vs 52.9% for 1.25 vs 5.0 mm, p = 0.004), stones greater than 2.0 mm were similarly detected at different slice selections (p = 0.056 to 0.572).Independent of other scanning parameters reconstruction section width influences the ability to detect small renal calculi. It must be considered when creating computerized tomography protocols.

Shabana W., Bude R.O., Rubin J.M.

To assess the ability of the color Doppler twinkling artifact to detect renal stones relative to acoustic shadowing, we scanned seven uric acid calculi embedded in a tissue mimicking phantom and in sheep kidneys using a high frequency linear array and a standard curved linear array ultrasound scanheads (L12-5 and C5-2; Philips Ultrasound, Bothel, WA, USA). The stones were scanned in and out of focus. The scans were optimized for shadow formation in gray-scale imaging and for color twinkling in color Doppler imaging. The images were analyzed using Image J (http://rsb.info.nih.gov/ij/). We calculated the contrast to noise ratios (C/N) for the acoustic shadows and the color twinkling artifact compared with background. These measurements were then evaluated using a single factor analysis of variance (ANOVA) and paired two-tailed t tests. With these comparisons, the C/Ns for twinkling were significantly higher than for acoustic shadowing. On average, twinkling produced 19.2 dB greater C/Ns for stones in the phantom and 17.6 dB more for the stones in the kidneys. In addition, ANOVA showed that twinkling is resistant to focusing and scanning frequency differences. The results suggest that the twinkling artifact is a robust method for detecting the presence of renal calculi. The color signature is easier to detect than is acoustic shadowing. Twinkling may be relatively resistant to many of the problems that plague ultrasound examinations for renal stones, i.e., out-of-focus scans that might be caused by beam aberration effects due to patient body habitus.

Tchelepi H., Ralls P.W.

This article explores the circumstances under which the color comet-tail artifact occurs and illustrates the clinical value of the artifact.Subtle abnormalities on gray-scale sonograms often are better appreciated and understood when the color comet-tail artifact is present. This artifact often is helpful in situations in which gray-scale imaging does not provide adequate information for a conclusive diagnosis. Visualization of the color comet-tail artifact can improve diagnostic confidence in a wide spectrum of clinical conditions encountered in sonographic practice.

Turrin A., Minola P., Costa F., Cerati L., Andrulli S., Trinchieri A.

The aim of the study was to investigate the diagnostic value of the colour Doppler twinkling artefact (TA) in renal stone disease. To enhance the evidence of TA, a preliminary in vitro study was performed to optimise the setting of colour Doppler sonography. In the in vitro study, an oxen kidney was examined using an high-frequency (12.5 MHz) linear array probe in a water bath before and after the inoculation of an aliquot of powder obtained by fragmentation of a calcium oxalate stone. In the clinical study, 67 patients with diagnosis of urinary stone based on B-mode sonography and 67 matched control subjects were examined with colour Doppler sonography using a low-frequency (2.5 MHz) curvilinear phased array probe. In vitro, the injection of calcium oxalate powder in a bovine kidney sample induced the appearance of spots without any back shadowing appearance on B mode but with a large number of TA on colour Doppler. In vivo, TA was much more frequent in patients with stone disease (95.5%) compared to controls (9.0%) (P < 0.001). TA was highly associated to renal stone disease and was also present in renal areas where a stone was undetected with B mode approach suggesting its diagnostic role although further studies are needed to confirm its accuracy. The type of instrumentation and its setting is crucial to obtain reproducible results.

Curhan G.C.

Epidemiology has improved our understanding and management of stone disease. Epidemiologic studies, by quantifying patterns and burden of disease, have helped identify risk factors, leading to changes in clinical practice and providing insights into pathophysiologic processes related to stone formation. Because nephrolithiasis is a complex disease, an understanding of the epidemiology, particularly the interactions among different factors, may help lead to approaches that reduce the risk of stone formation.

Ulusan S., Koc Z., Tokmak N.

To determine the diagnostic accuracy values of sonography in the detection of renal stones using noncontrast CT as the gold standard. In addition, we correlated the accuracy of sonography with stone size, the kidney affected (right versus left), and body mass index (BMI).Fifty patients underwent 2 separate sonographic examinations performed by 2 radiologists. CT scans were evaluated by another 2 radiologists, and the diagnosis was made by consensus. We compared the sonograms and CT scans and the sonographic detection of stones in the left and right kidneys. All sonographic findings were correlated with the BMI groups.The sensitivity of sonography for any stone in a patient was 52-57% for the right kidney (radiologist 1 and 2) and 32-39% for the left kidney (radiologist 1 and 2). The overall accuracy of sonography in detecting a stone in the right kidney by radiologists 1 and 2 was 67% and 77%, respectively. The corresponding accuracy values for the left kidney were 53% and 54%, respectively.Sonography is of limited value for detecting renal stones. The sonographic detection of a renal stone is dependent on the side of the kidney involved but is independent of BMI.

Fowler K.A., Locken J.A., Duchesne J.H., Williamson M.R.

To determine the sensitivity and specificity of ultrasonography (US) for detecting parenchymal and renal pelvis calculi and to establish the accuracy of US for determining the size and number of calculi.A total of 123 US and computed tomographic (CT) examinations were compared retrospectively for the presence of renal calculi. The sensitivity of US was determined for individual calculi and at least one calculus per examination. Retrospective findings were compared with the original US interpretation. The sizes of calculi in longest axis were compared on US and CT images, and the US detection of calculi in the left and right kidneys was compared. The use of US for detecting the full extent of calculus burden was evaluated in patients with multiple calculi.US depicted 24 of 101 calculi identified at CT, yielding a sensitivity of 24% and a specificity of 90%. There was no substantial difference for the detection of calculi in the right and left kidneys. The sensitivity of US for any calculi in a patient was 44%, equal to that of the original US interpretation. US enabled identification of 39% of patients with multiple calculi and demonstrated all calculi in 17% of these patients. The mean size of calculi detected with US was 7.1 mm +/- 1.2 (95% CI); 73% of calculi not visualized at US were less than 3.0 mm in size. Calculus size based on US and CT measurements was concordant in 79% of cases and differed by a mean of 1.5 mm +/- 0.7.US is of limited value for detecting renal calculi.

Memarsadeghi M., Heinz-Peer G., Helbich T.H., Schaefer-Prokop C., Kramer G., Scharitzer M., Prokop M.

To assess prospectively the effect of section width in multi-detector row computed tomographic (CT) evaluation of patients with acute flank pain who are suspected of having or known to have urinary stone disease.This study was approved by the ethics committee of the authors' university, and written informed consent was obtained from all patients. One hundred forty-seven patients (age range, 11-101 years; mean, 51.4 years +/- 18.7 [standard deviation]) suspected of having urinary stone disease underwent unenhanced multi-detector row CT. CT was performed with four detector rows, a section thickness of 1.0 mm, an effective tube current-time product of 100 mAs, and a tube voltage of 120 kVp (CT dose index, 11.4 mGy). From these data, three sets of transverse images were reconstructed with section widths of 1.5, 3.0, and 5.0 mm and approximately 50% of overlap each. Scans were evaluated in varying random orders by two radiologists for the number, size, and location of uroliths and nephroliths and for the presence of phleboliths, renal cysts, and secondary signs of obstruction. The significance of differences between the numbers of detected calcifications and the numbers of associated abnormalities on the scans obtained with varying section widths was tested with the McNemar test at a P level of less than .05. Spearman rho rank correlation coefficients were calculated to assess the correlation between the presence of uroliths and the presence of secondary signs.Uroliths were found in 72 of 147 (49.0%) patients, and nephroliths were found in 16 patients (10.9%). There was no significant difference between section widths of 1.5 and 3.0 mm with regard to the number of detected stones (264 uroliths and 61 nephroliths for both protocols). Transverse sections 5.0-mm wide revealed significantly fewer uroliths (n = 231; P < .001) and nephroliths (n = 47; P < .016). The final diagnosis was changed in four of 72 patients. All missed renal and ureteral stones measured less than 3 mm in diameter.Overlapping 3-mm sections are sufficient for the detection of urinary stone disease. Small calculi (

Poletti P., Platon A., Rutschmann O.T., Schmidlin F.R., Iselin C.E., Becker C.D.

The purpose of our study was to compare a low-dose abdominal CT protocol, delivering a dose of radiation close to the dose delivered by abdominal radiography, with standard-dose unenhanced CT in patients with suspected renal colic.One hundred twenty-five patients (87 men, 38 women; mean age, 45 years) who were admitted with suspected renal colic underwent both abdominal low-dose CT (30 mAs) and standard-dose CT (180 mAs). Low-dose CT and standard-dose CT were independently reviewed, in a delayed fashion, by two radiologists for the characterization of renal and ureteral calculi (location, size) and for indirect signs of renal colic (renal enlargement, pyeloureteral dilatation, periureteral or renal stranding). Results reported for low-dose CT, with regard to the patients' body mass indexes (BMIs), were compared with those obtained with standard-dose CT (reference standard). The presence of non-urinary tract-related disorders was also assessed. Informed consent was obtained from all patients.In patients with a BMI < 30, low-dose CT achieved 96% sensitivity and 100% specificity for the detection of indirect signs of renal colic and a sensitivity of 95% and a specificity of 97% for detecting ureteral calculi. In patients with a BMI < 30, low-dose CT was 86% sensitive for detecting ureteral calculi < 3 mm and 100% sensitive for detecting calculi > 3 mm. Low-dose CT was 100% sensitive and specific for depicting non-urinary tract-related disorders (n = 6).Low-dose CT achieves sensitivities and specificities close to those of standard-dose CT in assessing the diagnosis of renal colic, depicting ureteral calculi > 3 mm in patients with a BMI < 30, and correctly identifying alternative diagnoses.

Edyedu I., Ugwu O.P., Ugwu C.N., Alum E.U., Eze V.H., Basajja M., Ugwu J.N., Ogenyi F.C., Ejemot-Nwadiaro R.I., Okon M.B., Egba S.I., Uti D.E., Aja P.M.

Pregnancy leads to a number of structural and functional changes in the urinary system, which makes females susceptible to urological complications. This review aims to discuss the epidemiology, complications and prevention and management of urinary tract infections (UTIs), kidney stones and bladder dysfunction in pregnancy. UTIs are the most common urological problem presenting in 10% of pregnant women; Escherichia coli is the most common causative organism. If left untreated, UTIs lead to acute pyelonephritis which occurs in about 2% of pregnant women and which has serious consequences for both the mother and the baby. Kidney stones, although rare, are hazardous, occurring in 1 in 200 to 1 in 1500 pregnancies, and may cause obstructive uropathy, and aggravation of “labor-like” pain. Urological complications are frequent in pregnancy; bladder dysfunction alone has been documented to affect 50% of the pregnant women. Urological complications can have severe consequences when not properly managed including preterm labor and renal dysfunction. In order to have the best pharmacological care, safe use of antibiotics for UTIs is needed along with other measures for kidney stones. This review highlights the importance of a team approach to patient management to optimize outcome and touches briefly on some of the ethical dilemmas that may be encountered when drug therapy in pregnancy is being considered. Therefore, it is feasible to enhance the health of women and the fetus during this period through patient focused care and innovative interventions.

Squires J.H., Chaudhry R., Miyashita Y., Sutherland R., Fordham L.A.

Urolithiasis is defined as a calculus, or urinary stone, located anywhere within the urinary tract, while the term “nephrolithiasis” is used to describe a calculus located within the renal collecting system. Abdominal or flank pain associated with urolithiasis is termed “renal colic.”

Alshamrani A.F., Alrehily F.A., Alhazmi F.H., Alharbi A.M., Almohammadi S.O.

Background: A routine ultrasound scan is used to assess a variety of renal pathological cases. Sonographers face a variety of challenges that may affect their interpretation. Understanding normal organ shapes, human anatomy, physical concepts, and artifacts is required for accurate diagnosis. Sonographers must understand how artifacts appear in ultrasound images in order to reduce errors and improve diagnosis. The purpose of this study is to assess sonographers' awareness and knowledge of artifacts in renal ultrasound scans. Methods: Participants in this cross-sectional study were asked to complete a survey containing different types of common artifacts in renal system ultrasound scans. An online questionnaire survey was used to collect the data. The questionnaire targeted radiologists, radiologic technologists, and intern students in Madinah hospitals in the ultrasound department. Results: The total number of participants was 99, with 9.1% being radiologists, 31.3% being radiology technologists, 6.1% being senior specialists, and 53.5% being intern students. There was a significant difference in the participants’ knowledge of ultrasound artifacts in the renal system with the total selection of the right artifact in senior specialists at 73% and intern students 45%. There was a direct relationship between age and years of experience in distinguishing artifacts in the renal system scan. A category of participants with the highest age and experience got 92% of the correct selection of artifacts. Conclusion: The study concluded that intern students and radiology technologists have limited knowledge of ultrasound scan artifacts, whereas senior specialists and radiologists have a high level of awareness of the artifacts. result: The total number of participants was 99, with 9.1 other: NA

Khandelwal S., Dhande R., Sood A., Parihar P., Mishra G.V.

Waelti S.L., Fandak J., Markart S., Willems E.P., Wildermuth S., Fischer T., Dietrich T.J., Matissek C., Krebs T.

Bioabsorbable magnesium-based alloy screws release gas upon resorption. The resulting findings in the adjacent soft tissues and joints may mimic infection. The aim of the study was to evaluate the ultrasound (US) findings in soft tissues and joints during screw resorption. Prospectively acquired US studies from pediatric patients treated with magnesium screws were evaluated for screw head visibility, posterior acoustic shadowing, twinkling artifact, foreign body granuloma, gas (soft tissue, intra-articular), alterations of the skin and subcutaneous fat, perifascial fluid, localized fluid collections, hypervascularization, and joint effusion. Sixty-six US studies of 28 pediatric patients (nfemale = 9, nmale = 19) were included. The mean age of the patients at the time of surgery was 10.84 years; the mean time between surgery and ultrasound was 128.3 days (range = 6–468 days). The screw head and posterior acoustic shadowing were visible in 100% of the studies, twinkling artifact in 6.1%, foreign body granuloma in 92.4%, gas locules in soft tissue in 100% and intra-articular in 18.2%, hyperechogenicity of the subcutaneous fat in 90.9%, cobblestoning of the subcutaneous fat in 24.2%, loss of normal differentiation between the epidermis/dermis and the subcutaneous fat in 57.6%, localized fluid collection in 9.9%, perifascial fluid in 12.1%, hypervascularization in 27.3%, and joint effusion in 18.2%. US findings in pediatric patients treated with magnesium screws strongly resemble infection, but are normal findings in the setting of screw resorption. Bioabsorbable magnesium-based alloy screws release gas during resorption. The resulting US findings in the adjacent soft tissues and joints in pediatric patients may mimic infection, but are normal findings. • Bioabsorbable magnesium-based alloy screws release gas upon resorption. • The resulting ultrasound findings in children’s soft tissues and joints closely resemble those of soft tissue infection or osteosynthesis-associated infection. • Be familiar with these ultrasound findings in order to avoid inadvertently misdiagnosing a soft tissue infection or osteosynthesis-associated infection.

Rokni E., Simon J.C.

Abstract Objective. Pathological mineralizations form throughout the body and can be difficult to detect using conventional imaging methods. Color Doppler ultrasound twinkling highlights ∼60% of kidney stones with a rapid color shift and is theorized to arise from crevice microbubbles as twinkling disappears on kidney stones at elevated pressures and scratched acrylic balls in ethanol. Twinkling also sometimes appears on other pathological mineralizations; however, it is unclear whether the etiology of twinkling is the same as for kidney stones. Approach. In this study, five cholesterol, calcium phosphate, and uric acid crystals were grown in vitro and imaged in Doppler mode with a research ultrasound system and L7-4 transducer in water. To evaluate the influence of pressure on twinkling, the same crystals were imaged in a high-pressure chamber. Then, the effect of surface tension on twinkling was evaluated by imaging crystals in different concentrations of surfactant (1%, 2%, 3%, 4%) and ethanol (10%, 30%, 50%, 70%), artificial urine, bovine blood, and a tissue-mimicking phantom. Main results. Results showed that all crystals twinkled in water, with cholesterol twinkling significantly more than calcium phosphate and uric acid. When the ambient pressure was increased, twinkling disappeared for all tested crystals when pressures reached 7 MPa (absolute) and reappeared when returned to ambient pressure (0.1 MPa). Similarly, twinkling across all crystals decreased with surface tension when imaged in the surfactant and ethanol (statistically significant when surface tension <22 mN m−1) and decreased in blood (surface tension = 52.7 mN m−1) but was unaffected by artificial urine (similar surface tension to water). In the tissue-mimicking phantom, twinkling increased for cholesterol and calcium phosphate crystals with no change observed in uric acid crystals. Significance. Overall, these results support the theory that bubbles are present on crystals and cause twinkling, which could be leveraged to improve twinkling for the detection of other pathological mineralizations.

Nabheerong P., Kengkla K., Saokaew S., Naravejsakul K.

The goal of this study was to perform a comprehensive meta-analysis to assess the overall diagnostic value of Doppler twinkling for the diagnosis of urolithiasis. We systematically searched the PubMed, EMBASE, and Cochrane Library databases from inception through May 31, 2021. Studies including patients with urolithiasis who underwent color flow Doppler sampling to highlight the twinkling artifact and computed tomography were included. Diagnostic test meta-analysis was performed with a bivariate model. We used summary receiver operating characteristic curves to summarize the overall diagnostic performance. The weighted sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were calculated. Sixteen studies involving 4572 patients were included in the systematic review and meta-analysis. The weighted sensitivity was 0.86 (95% confidence interval [CI] 0.72–0.94), specificity 0.92 (95% CI 0.75–0.98), positive likelihood ratio 11.3, negative likelihood ratio 0.2, and diagnostic odds ratio 75.5. The Doppler twinkling artifact has good diagnostic value for the diagnosis of urolithiasis and should be used as a complementary tool in the diagnosis of urolithiasis.

Gromov A.I., Sapozhnikov O.A., Kaprin A.D.

The twinkling artifact has been known to specialists in ultrasound diagnostics since 1996. However, until now there is no understanding of the reasons for its appearance, and the place of its application in diagnostics.Material and methods. Electronic databases (PubMed, E-library, Web of Science) were searched studies using the keyword – “twinkling artifact”. The scientific publications on the Doppler twinkling artifact from the moment of the first reports about its existence is systematized and analyzed. The authors' own developments on this topic are presented. Modern views on this phenomenon and its place in ultrasound diagnostics are described. An explanation of the physical mechanisms of this phenomenon is given.Results. Recommendations are formulated for practitioners on changing the settings of an ultrasound scanner in order to increase twinkling artifact detectability. The directions of using the artifact to obtain additional diagnostic signs of pathological changes, which currently include the diagnosis of nephro-, uretero- and choledocholithiasis, are determined.Conclusions. The high efficiency of the use of the twinkling artifact for the diagnosis of small kidney stones, comparable with the capabilities of computed tomography, has been shown.  

Iv Kyrazis C., Rajderkar D.

Pelvic pain may be caused by disorders of the reproductive, urinary, or gastrointestinal systems. In the pediatric population, pelvic pain is often first evaluated with ultrasonography, with other imaging modalities reserved for further workup or specific indications. Radiologists must be aware of the findings associated with common pelvic emergencies to allow prompt diagnosis and prevention of life-threatening complications. Although the range of pelvic pathology is extensive, this pictorial review presents ultrasound examples of common nontraumatic causes of pelvic pain encountered in the pediatric population, with a brief discussion about multimodality imaging features.

Ellison J.S., Thakrar P.

Children are at greater risk for deleterious effects of ionizing radiation than adults. Imaging strategies in children are therefore focused on obtaining the necessary clinical information using the minimum required dose of radiation. The appropriate imaging modality will depend upon the indication for evaluation. In the setting of suspected nephrolithiasis in children, ultrasound is generally regarded as the first-line modality. Computed tomography, especially with attention to dose modulation, may be useful in situations where the diagnosis is uncertain or ultrasound is unavailable. Cross-sectional imaging or adjunct imaging strategies such as abdominal radiography may be necessary in specific cases for preoperative planning. Following an acute presentation or surgical intervention, interval imaging should be timely and comparable to the initial imaging and should provide minimal additional radiation exposure. Surveillance imaging is generally performed using ultrasonography, although the appropriate interval for follow-up sonography remains undefined.

高 海.

Serrell E.C., Best S.L.

Radiological imaging techniques and applications are constantly advancing. This review will examine modern imaging techniques in the diagnosis of urolithiasis and applications for surgical planning.The diagnosis of urolithiasis may be done via plain film X-ray, ultrasound (US), or contrast tomography (CT) scan. US should be applied in the workup of flank pain in emergency rooms and may reduce unnecessary radiation exposure. Low dose and ultra-low-dose CT remain the diagnostic standard for most populations but remain underutilized. Single and dual-energy CT provide three-dimensional imaging that can predict stone-specific parameters that help clinicians predict stone passage likelihood, identify ideal management techniques, and possibly reduce complications. Machine learning has been increasingly applied to 3-D imaging to support clinicians in these prognostications and treatment selection.The diagnosis and management of urolithiasis are increasingly personalized. Patient and stone characteristics will support clinicians in treatment decision, surgical planning, and counseling.

Squires J.H., Chaudhry R., Miyashita Y., Sutherland R., Fordham L.A.

Urolithiasis is defined as a calculus, or urinary stone, located anywhere within the urinary tract, while the term “nephrolithiasis” is used to describe a calculus located within the renal collecting system. Abdominal or flank pain associated with urolithiasis is termed “renal colic.”

Kang J., Han K., Song I., Kim K., Jang W.S., Kim M.J., Yoo Y.

Detecting microcalcifications (MCs) in real time is important in the guidance of many breast biopsies. Due to its capability in visualizing biopsy needles without radiation hazards, ultrasound imaging is preferred over X-ray mammography, but it suffers from low sensitivity in detecting MCs. Here, we present a new nonionizing method based on real-time multifocus twinkling artifact (MF-TA) imaging for reliably detecting MCs. Our approach exploits time-varying TAs arising from acoustic random scattering on MCs with rough or irregular surfaces. To obtain the increased intensity of the TAs from MCs, in MF-TA, acoustic transmit parameters, such as the transmit frequency, the number of focuses and f-number, were optimized by investigating acoustical characteristics of MCs. A real-time MF-TA imaging sequence was developed and implemented on a programmable ultrasound research system, and it was controlled with a graphical user interface during real-time scanning. From an in-house 3D phantom and ex vivo breast specimen studies, the MF-TA method showed outstanding visibility and high-sensitivity detection for MCs regardless of their distribution or the background tissue. These results demonstrated that this nonionizing, noninvasive imaging technique has the potential to be one of effective image-guidance methods for breast biopsy procedures.

Park V.Y., Kang J., Han K., Song I., Kim K., Nam S.J., Kim G.R., Yoon J.H., Jang W.S., Yoo Y., Kim M.J.

Multifocal Doppler twinkling artifact (MDTA) imaging has shown high detection rates of microcalcifications in phantom studies. We aimed to evaluate its performance in detecting suspicious microcalcifications in comparison with mammography by using ex vivo breast cancer specimens. We prospectively included ten women with breast cancer that presented with calcifications on mammography. Both digital specimen mammography and MDTA imaging were performed for ex vivo breast cancer specimens on the day of surgery. Five breast radiologists marked cells that included suspicious microcalcifications (referred to as ‘positive cell’) on specimen mammographic images using a grid of 5-mm cells. Cells that were marked by at least three readers were considered as ‘consensus-positive’. Matched color Doppler twinkling artifact (CDTA) signals were compared between reconstructed US-MDTA projection images and mammographic images. The median detection rate for each case was 74.7% for positive cells and 96.7% for consensus-positive cells. Of the 10 cases, 90% showed a detection rate of ≥ 80%, with 50% of cases showing a 100% detection rate for consensus-positive cells. The proposed MDTA imaging method showed high performance for detecting suspicious microcalcifications in ex vivo breast cancer specimens, and may be a feasible approach for detecting suspicious breast microcalcifications with US.