Basics,principles, techniques and modern methods in paediatric ultrasonography

Ultrasonography (US) is the mainstay of paediatric Radiology. This review aims at revisiting basic US principles, to list specific needs throughout childhood, and to discuss the application of new and modern US methods. The various sections elude to basic US physics, technical requisites and tips for handling, diagnostically valuable applications of modern techniques, and how to properly address hazards, risks and limitations. In conclusion, US holds vast potential throughout childhood in almost all body regions and many childhood specific queries – helping to reduce the need for or to optimize more invasive or irradiating imaging. Make the most of US and offerings a dedicated paediatric US service throughout the day, the week and the year thus is and will stay a major task of Paediatric Radiology.     

Fast MR imaging techniques: Impact in the abdomen

The increased efficiency of MRI data acquisition has had a substantial impact on clinical MRI of the abdomen. Five particular applications that have thus been affected include breath-hold imaging of liver lesions (including detection, characterization, and biopsy), MR cholangiopan- creatography, practical chemical shift imaging (including liver and adrenal glands), dynamic imaging after contrast media injection, and MR angiography.     

Recent technical advances in MR imaging of the abdomen

MRI of the abdomen has been under development for well over a decade. In the past, considerable work was directed toward identification and suppression of the artifacts caused by motion. However, within the last several years, image quality has further improved, particularly as various fastscan techniques have been adapted for abdominal imaging. The purpose of this work is to review these technical developments. Specific methods include adaptation of the acquisition time to breath-holding, acquisition over multiple respiratory cycles, adjustment of the contrast of various sequences, and development of more sensitive receiver coils and faster gradient systems. Opportunities for future development are also identified, including improved slice sampling, increased in-plane spatial resolution, real-time means for monitoring respiration, and expanded applications. As these technical advances are implemented, it is expected that the overall sensitivity and specificity of abdominal MRI will further improve.     

Feasibility of MR urography in neonates and infants with anomalies of the upper urinary tract

The aim of this study was to evaluate the feasibility and diagnostic potential of dynamic MR urography (MRU) in neonates and infants with sonographically detected abnormalities of the upper urinary tract. Thirty infants (age range 5 days to 3 years, mean age 7.9 months; male:female: 22:8) underwent MRU using T2 and contrast-enhanced dynamic T1-weighted sequences. The results were compared with the findings of ultrasound ( n=30), intravenous urography (IVU, n=19) and/or scintigraphy ( n=25) based on the criteria suggestive of obstructive uropathy. Oral sedation was sufficient to perform MRU with diagnostic quality in 20 of 21 patients younger than 1 year; 9 older patients needed intravenous sedation. Diagnosis of the 66 renal units (58 kidneys, 29 successful examinations) included normal systems (contralateral units), duplex systems, vesico-ureteral reflux, obstructive megaureter, ureteropelvic junction obstruction and accompanying renal parenchymal disease, with complex pathology in 10 patients. Magnetic resonance urography demonstrated anatomy better than IVU, particularly the renal parenchyma, (ectopic) ureters, and poorly functioning dilated systems. Magnetic resonance urography was superior to US in showing ureteral pathology. Tiny cysts in dysplastic kidneys were better seen by US. Gadolinium-enhanced dynamic MRU allowed accurate assessment of obstruction applying IVU criteria. Here MRU matched IVU results, and most of the scintigraphic findings. Magnetic resonance urography can be performed in young infants with diagnostic quality using oral sedation. Magnetic resonance urography correctly depicts anatomy and allows assessment of the urinary tract better than US and IVU, with additional functional information. Magnetic resonance urography thus has the potential to replace IVU for many indications.     

Role of MR renography in the evaluation of acute upper urinary tract obstruction

Purpose

To present the role of MR renography in diagnosis of upper urinary tract obstruction (UTO) with evaluation of diagnostic criteria for acute obstruction.

Material and methods

Thirty consecutive patients with obstructive anuria were included in our study. For identification of the cause of obstruction, all patients were subjected to plain abdominal X-ray (KUB), gray scale ultrasonography, non-contrast CT for the abdomen and pelvis (NCCT). There were five patients with bilateral obstruction and 25 with obstructed solitary functioning kidney, so the study included 35 units. All patients were subjected to radioisotope diuretic renography and magnetic resonance renography (MRR) before relief of obstruction and 3 days after drainage. Of the 30 patients included, 20 were men and 10 women.

Results

Among our patients the mean serum creatinine at time of presentation was 7 ± 4.5 mg/dl (range 2.4–12) and GFR ranged from 33 to 48 ml/min (mean ± SD; 38 ± 4.2). All the renal units have hydronephrosis. The mean pre drainage SI values 133 ± 22 (range 120–180). The mean time to peak (TP) for each unit was 171.6 ± 78 s and at isotope renography it was 320 ± 66 s. There was good corticomedullary differentiation (CMD) in 31 units and the remaining 4 showed loss of CMD differentiation. The CMD crossing time was 163.6 ± 70.4 s. Post kidney drainage the parenchymal SI was increased in 30 units, in 3 units there was drop and no change in 2 (r = 0.29). There is relative reduction in the time to peak, it becomes 67 ± 79 s after drainage (r = 0.76).

Conclusion

MR renography is a clinically valuable technique that provides diagnostic criteria to diagnose the acute urinary obstruction and allows follow up of renal function.     

MRI of the marrow in the paediatric skeleton

Magnetic resonance imaging (MRI) has greatly advanced evaluation of marrow diseases of the paediatric skeleton. As with many other aspects of paediatric radiology it is important to recognize the normal variations in the appearance of the marrow that occur in the growing child. These normal variations need to be differentiated from diseases and conditions that affect the marrow. This review describes the normal changes that occur in children with age, and the appearances of the pathological changes seen in infection, infiltration, haematological disorders, transplantation and radiation therapy.     

Cystography in infants and children: a critical appraisal of the many forms with special regard to voiding cystourethrography

The aim of this study was to describe and discuss the various forms of cystography and their clinical value. Conventional fluoroscopic voiding cystourethrography (VCU), radionuclide cystography and the various sonographic cystographic approaches, including echo-enhanced cystosonography (EECS), are described. Their indications, potential, benefit and setbacks/restrictions are discussed with regard to the literature and the constantly changing clinical demand. With the introduction of EECS a new and reliable tool has been established to be useful for follow-up and screening for vesico-ureteral reflux (VUR); however, with the growing importance of functional disturbances a reliable method to evaluate both function and anatomy/VUR as offered by modified VCU is mandatory, and thus VCU remains to play a major part in evaluating children with urinary tract infection, suspected VUR, hydronephrosis or functional bladder disturbances. While EECS offers a new method for certain indications, such as follow-up examinations in VUR or screening, VCU remains an irreplaceable tool for evaluating anatomy (particularly the male urethra) and bladder function (if performed using the modified technique). Electronic Publication     

Ferucarbotran (Resovist): a new clinically approved RES-specific contrast agent for contrast-enhanced MRI of the liver: properties,clinical development,and applications

Ferucarbotran (Resovist) is the second clinically approved superparamagnetic iron oxide developed for contrast-enhanced MRI of the liver. The purpose of this review is to provide an overview on the properties, clinical development, and application of ferucarbotran. Safety data obtained during clinical phases I–III revealed a total of 162 adverse events within 1053 patients, of which 75 were classified as possibly, probably, or definitely drug related. The majority of events occurred within the first 3 h (73 of 75) and was of mild intensity. The agent significantly improves the detection of hypovascular focal liver lesions with a comparable sensitivity in lesion detection to CTAP but without a relevant loss in specificity. Furthermore, ferucarbotran leads to a significant improvement of the sensitivity for lesion classification and characterization of the most frequent liver lesions. Contrast-enhanced MRA is not feasible and the angiographic effect is not sufficient to allow for postprocessing of data into maximum intensity projections. Intraindividual studies at low-field (0.2 T) and high-field (1.5 T) showed similar rates for lesion detection. The time window for contrast-enhanced MRI of the liver is at least 1 day up to 4 days. The compound can be regarded as safe and well tolerated. Even bolus injections caused no cardiovascular side effects, lumbar back pain, or clinically relevant laboratory changes. The examination time can be kept short with T1- and T2-weighted pre-contrast sequences, dynamic MRI over 10 min, and finally accumulation phase T2-weighted MRI. Patients who may benefit in particular are surgical candidates for resection, transplantation, or interventional therapies, and patients with liver cirrhosis and/or suspected hepatocellular carcinoma to either exclude malignancy or to define the extent of disease, the location of lesions, and the type of newly detected lesions. Electronic Publication     

Ultrasound of the paediatric urogenital tract

Pathology in the urinary tract is one of the most frequent queries when children are referred for an ultrasound examination. Comprehensive ultrasound examinations can answer most clinical questions of the urogenital tract with minimal patient preparation and without the use of ionising radiation. Therefore, optimised imaging protocols should be available in all radiology departments where children are examined. This review suggests a preferred imaging protocol for urogenital imaging in children and gives an overview of the different structures of the urogenital tract, the normal age-related sonographic anatomy, and gives examples of the most commonly encountered diseases of the urogenital system in children.     

MR imaging of the gastro-intestinal tract in children

MR imaging (MRI) is an established method for the evaluation of particularly inflammatory bowel disease in adults, as well as for acute abdominal pain in pregnant women. Despite the fact that MRI is ideally suited for the evaluation of children the method is still not established in these patients. The value of MRI in Crohn's disease, ulcerative colitis and appendicitis as well as intestinal tumors and malformations has been documented in children. There will be more indications in the future depending on the development of new imaging techniques, faster sequences, stronger gradients and increasing availability. Furthermore, the radiologist's attention must be drawn to decrease the radiation burden in children and to replace ionizing techniques especially in chronic disease with the need for repeated follow-up studies and in younger children. This review will discuss some general considerations for the use of MRI in evaluating the paediatric gastro-intestinal tract.     

Potential applications of three-dimensional ultrasound in the pediatric urinary tract: pictorial demonstration based on preliminary results

The aim of this study was to describe the potential of three-dimensional ultrasound (3DUS) in the urinary tract of neonates, infants, and children. The potential applications are illustrated based on our experience in 80 patients using two different 3DUS techniques. Various disease entities throughout the neonatal and pediatric age have been evaluated. The potential of 3DUS is discussed based on comparison with conventional 2DUS or other imaging (as clinically indicated), focused on the potentially improved renal parenchymal volume assessment. In our experience, 3DUS is feasible in neonates, infants, and children without sedation. It reduces imaging time, improves demonstration of complex anatomy and allows for evaluation of anatomy/pathology in any plane. The 3DUS improves volume assessment and follow-up comparison by offering an improved standardization and documentation. Rendered views of the dilated collecting system enable a comprehensive demonstration of hydronephrosis similar to intravenous urography or MR urography images. Additionally, 3DUS offers an ideal tool for training and education. Yet, limitations have to be acknowledged: areas inaccessible for 2DUS; poor quality of the original 2DUS acquisition; limited resolution; patient motion and breathing; cardiac pulsation creating artifacts and misregistration; equipment cost; lack of 3D DICOM standards creating problems with data storage; as well as system-inherent technical limitations. Nevertheless, the 3DUS holds the potential to become a valuable additional imaging tool for sonographic evaluation of the pediatric urinary tract.     

Patterns of peritoneal spread of tumor in the abdomen and pelvis

The spread of tumor in the peritoneum can be understood, although it is a complex organ. A study of its embryology, anatomy and function is of clear benefit. It is formed from a network of folds, reflections, and potential spaces produced by the visceral and parietal peritoneum. These folds and reflections begin as a dorsal and ventral mesentery, supporting the primitive gut in early embryologic development. The dorsal mesentery connects the stomach and other organs to the posterior abdominal wall, while the ventral mesentery connects the stomach to the ventral abdominal wall. As the embryo develops, there is further organ growth, elongation, cavitation and rotation. The dorsal and ventral mesentery also develops along with the viscera, forming ligaments, mesenteries, omenta and potential spaces from the resulting reflections and folds. These ligaments, mesenteries, and omenta, support and nurture the organs of the peritoneum, providing a highway for arteries, veins, nerves and lymphatics. The potential spaces created from these folds and reflections of the visceral and parietal peritoneum are also important to realize. For example, the transverse mesocolon divides the peritoneal cavity into a supramesocolic and inframesocolic space in the abdomen and paravesicular spaces within the pelvis. The falciform ligament is well known in the supramesocolic space, dividing it further into a left and right compartment. Knowledge of the peritoneal vascular anatomy is beneficial in locating the spaces and ligaments about the peritoneum. For example, identifying the left gastric artery or vein will lead to the gastrohepatic ligament, which is part of the supramesocolic space. Besides serving a life sustaining role, the multiple compartments, ligaments, mesenteries and omenta within the peritoneum can also facilitate the spread of disease. Tumors can spread directly from one organ to another, seed metastatic deposits in the peritoneal cavity, and travel through the lymphatic or hematogenous route to invade other organs in the peritoneum.     

CT灌注成像在脑梗死前期局部低灌注中的应用价值

目的: 探讨脑梗死前期局部低灌注的CT灌注成像的价值.材料和方法: 分析15例临床诊断为脑局部缺血CT平扫和CT增强扫描,常规MRI、MRA及CT灌注成像的表现.结果: 15例CT平扫和增强扫描均未发现新的脑梗死灶,CT灌注成像发现脑梗死前期脑局部低灌注I1期4例、I2期7例、II2期3例,MRI发现缺血灶14个,MRA发现一侧大脑中动脉狭窄2例,一侧大脑中动脉闭塞1例.结论: 脑梗死前期局部低灌注,常规CT,MRI无异常发现.CT灌注成像可超早期发现脑组织局部血流动力学异常,并可分期区分低灌注的脑局部微循环的病理生理学状态,对临床治疗有重要价值.     

The gamut of abdominal and pelvic cystic masses in children

The gamut of abdominal and pelvic cystic masses in children is long with lesions affecting the urogenital tract and retroperitoneum, gastrointestinal tract and mesentery, hepatobiliary tract, and spleen. The goal of this pictorial review is to display the radiological manifestations of these disorders. The radiologist will learn, from this review of the differential diagnosis, how to reach a diagnosis after analyzing the characteristic findings using the appropriate imaging diagnostic studies among the various modalities available in his armamentarium, and the optimal management of these conditions. Received: 21 December 1999 Revised: 10 April 2000 Accepted: 14 April 2000     

多层螺旋CT血管成像技术在腹部扫描中的应用

目的 探讨多层螺旋CT扫描方法及三维重建技术在腹部血管成像中的应用。方法 6例肝占位病变患者，15例肝移植患者进行CT扫描检查，三维重建技术应用最大密度投影法(M1P)和表面遮蔽法(SSD)。结果 所有患者均一次顺利完成检查，19例清晰显示血管分支与走行。结论 MSCTA是目前一种分辨率高、快速、准确，无创性血管成像方法。     

The MRI of extraadrenal pheochromocytoma in the abdominal cavity

The purpose of this study was to summarize the MR appearances of extraadrenal pheochromocytoma in the abdominal cavity and evaluate the capabilities of MRI in diagnosis of the tumor. Eleven consecutive patients with an extraadrenal pheochromocytoma in abdominal cavity who underwent preoperative 0.5 T (n=5) or 1.5 T (n=6) superconductor MRI and had a surgical resection were enrolled in the study. The MR scanning protocol included axial T(2)-weighted imaging with or without fat-suppressed sequences, axial and coronal uncontrast and contrast T(1)-weighted sequences with or without fat suppression. The extraadrenal pheochromocytomas were found in retroperitoneum (n=5), the urinary bladder (n=1), the pelvis (n=1), the right prerenal area (n=1), the renal hilus (n=1), the left paramusculus psoas major (n=1) and liver (n=1). The mean maximal diameter of tumors was 55.9 mm (range 17.8-162.2 mm). The high signal intensity was seen on T(2)-weighted imaging in all tumors compared to muscle or liver, especially with fat suppression. The intratumoral septa and capsules were shown in 63.6% and 72.7% of cases, respectively, which had low signal intensity on T(2)-weighted imaging. These relative characteristics may be helpful for qualitative diagnosis of extraadrenal pheochromocytomas with MRI. Other usefulness of MRI was to locate the position, to decide the range of tumors and to show well the relationship between the tumor and near structures.     

Potential of three-dimensional ultrasound in neonatal and paediatric neurosonography

The aim of this study was to describe the potential of three-dimensional ultrasound (3D US) in paediatric and neonatal neurosonography. The potential applications are illustrated based on our experience in 150 patients using three different 3D US techniques at two different sites. Various disease entities throughout the paediatric age have been evaluated. The potential of 3D US, including 3D US of the cerebral vessels based on colour Doppler data, is discussed based on comparison with conventional 2D US or other imaging (as available), and with regard to the literature. In our experience, 3D US is feasible in neonatal and paediatric neurosonography. It reduces imaging time, improves demonstration of complex anatomy and vasculature, and allows for evaluation of anatomy/pathology in any plane. The 3D US furthermore improves volume assessment (e.g. in hydrocephalus), and comparison with CT, MRI and during follow-up, with a potentially improved standardisation and documentation. The 3D US additionally offers an ideal modality for training and education, as the brain and the neonatal spine can be virtually rescanned at the workstation. Yet, limitations such as areas inaccessible to 2D US, limited resolution and motion artefacts have to be acknowledged. Three-dimensional US has the potential to become a valuable additional imaging tool in paediatric neurosonography.