Use of tissue harmonic imaging in pediatric echocardiography

Recent advances in ultrasound technology

Technical improvements have made profound changes in diagnostic ultrasound imaging. Some of these changes, such as encoded pulses and receive focusing, occur in the background and are essentially nonadjustable. Others, including harmonics and compounding, are real-time options and are adjustable by the imager. New technologies that offer great promise for improved characterization of lesions include contrast ultrasound and elastography. This article will attempt to update the small animal imager on the clinical applications of these newer technologies.

Harmonic US imaging of appendicitis in children

BACKGROUND

Harmonic imaging (HI), a relatively new ultrasound modality, was initially reported to be of use only in obese adult patients. HI increases the contrast and spatial resolution resulting in artefact-free images, and has been shown in adults to significantly improve abdominal sonography. Regarding its application in paediatric patients, just a handful reports exist and these do not encompass its use in intestinal sonography.

OBJECTIVE

To compare the sonomorphological image quality of HI and fundamental imaging (FI, conventional grey-scale imaging) in the diagnosis of histologically confirmed appendicitis in children.

MATERIALS AND METHODS

For this prospective comparative study, 50 children (male/female 25/25; mean age 9.9 years) suspected of having appendicitis were recruited. In all patients US examination of the appendix and periappendiceal region was performed preoperatively and appendectomy carried out. The final diagnosis was based on histological examination of the appendix. Both FI and HI were used in the US examination (tissue harmonic imaging, THI; Sonoline Elegra, Siemens; 7.5 MHz linear transducer). A detailed comparison of the images from FI and HI was performed using a scoring system. The parameters compared included delineation of the appendiceal contour, wall, mucosa, contents of the appendix and surrounding tissues. Furthermore, periappendiceal findings such as mesenteric echogenicity, free fluid, lymph nodes and adjacent bowel wall thickening were compared.

RESULTS

In 43 children (86%) acute appendicitis was histologically confirmed. The inflamed appendix could be depicted in the HI and FI modes in 93% and 86%, respectively. HI was found to be significantly better for the depiction of the outer contour, wall, mucosa and contents of the appendix (P<0.01). This was also true for the demonstration of free fluid, mesenteric lymph nodes, adjacent bowel walls and mesenteric echogenicity.

CONCLUSION

HI should be the preferred modality for scanning the right lower abdomen in suspected acute appendicitis. The diagnosis of acute appendicitis can then be more definitely ascertained.

Moderne Ultraschalltechniken und ihre Anwendungen am kindlichen Harntrakt

In children ultrasound plays a central role in the diagnostic imaging of the urinary tract. It is used most frequently and as a primary diagnostic option. Consequently, innovations in ultrasound technology and ultrasound contrast media have major impact on pediatric urosonography. Harmonic imaging is a modality that produces artifact-free images with high resolution. It has been shown that harmonic imaging is superior to fundamental mode in many urosonographic indications. Color Doppler is an established imaging modality, but its application for diagnosis of stones in the urinary tract, especially in children, is relatively new. The so-called twinkling sign, a color Doppler artifact at the site where one normally expects the acoustic shadow to be, enhances the conspicuity of the stone. A further development is three-dimensional (3D) ultrasound. It offers better volume measurement of the bladder and kidneys than 2D ultrasound. Contrast-enhanced voiding urosonography has already proven to be a valuable alternative in the diagnosis of vesicoureteral reflux. Thus, a significant decrease of radiation exposure has become possible as it replaces the radiological methods. With the introduction of contrast-specific ultrasound imaging modalities, further improvements in voiding urosonography are emerging.

Safety and efficacy of intravenous contrast imaging in pediatric echocardiography

This study was performed to determine the safety and efficacy of intravenous contrast echocardiography in children attending a tertiary cardiac center. This was a prospective study to evaluate the use of Optison contrast agent in children with severely limited transthoracic echocardiographic windows. Twenty children (median age, 15 years; range, 9-18) underwent fundamental imaging (FI), harmonic imaging (HI), and HI with intravenous contrast (Optison FS-069). Endocardial border delineation was determined based on a visual qualitative scoring system (0, none: 4, excellent). Endocardial border definition was significantly improved in all patients using contrast echocardiography (FI vs Optison, p < 0.001 for each). Improved border definition was most dramatic in the apical and left ventricular (LV) free wall regions. Left ventricular ejection fraction (LVEF) was measurable in 20 patients (100%) using contrast compared to 11 (55%) with FI or HI (p < 0.05). The echocardiographic diagnosis was correctly delineated in 1 patient with a severely dyskinetic LV segment only with use of intravenous contrast and HI. No patients suffered adverse hemodynamic effects, changes in taste, or flushing episodes. Three patients experienced transient headaches. Intravenous contrast echocardiography offers an additional tool in evaluating children with very poor transthoracic echocardiographic windows. Such a strategy increases diagnostic accuracy and allows accurate LVEF determination. Adverse hemodynamic effects related to intravenous contrast are exceedingly rare.

Harmonic versus conventional ultrasound imaging of the urinary tract in children

BACKGROUND

Harmonic imaging (HI) is a relatively new US method. Its usefulness in children has yet to be determined.

OBJECTIVE

To evaluate the value of HI in urinary tract imaging of infants and children.

MATERIALS AND METHODS

The bladder and kidneys of 29 unselected patients, aged 2 months to 12.8 years (mean, 6.8 years), were examined from ventral and dorsal approaches using conventional (= fundamental) imaging (FI) (6.5 and 3.4 MHz) and HI (3.3 MHz). In addition to global image quality, visualization of bladder wall, retrovesical space, renal contrast to liver/spleen, the pelvicalyceal systems, and the difference between cortex and medulla were assessed. Parameters were rated by two independent examiners and statistical analysis was performed.

RESULTS

There were significant differences between the three imaging settings for all parameters studied (P<0.003). With the dorsal approach, HI was superior to FI for all parameters analysed (P<0.05). Using the ventral approach, a significant improvement of imaging with HI was found for the bladder and the renal pelvis (P<0.02).

CONCLUSIONS

HI is a useful additional tool for imaging the urinary tract in children of all ages. The method particularly improves visualization of the bladder and the kidney from a dorsal approach.

[Advances in pediatric sonography]

Advances in the field of ultrasound technology and ultrasound contrast media over the past few years have also brought major improvements to pediatric sonography. Accordingly, contrast-enhanced voiding urosonography has become a valuable alternative in the diagnosis of vesicoureteral reflux. It is possible to achieve significant reduction in radiation exposure replacing the conventional radiologic methods used for reflux diagnosis with contrast-enhanced ultrasound. Through the introduction of harmonic imaging, an ultrasound scanning modality with high spatial and contrast resolution has become available. The modality was initially propagated as one to be applied in difficult-to-scan adults. However, initial experiences in pediatric applications are demonstrating the significant improvement it can bring in the ultrasound image quality, for example, in intestinal ultrasound. A further development is three-dimensional [3D] imaging using ultrasound. 3D-ultrasound not only offers an improvement in diagnosis but also in the acceptance of ultrasound in interdisciplinary work and teaching. The first applications of 3D-ultrasound in pediatrics are focusing on brain ultrasound and volume measurement of the kidneys.