Phase Inversion Tissue Harmonic Sonographic Imaging

Frequency-Dependent Spatial Coherence in Conventional and Chirp Transmissions

The development of adaptive imaging techniques is contingent on the accurate and repeatable characterization of ultrasonic image quality. Adaptive transmit frequency selection, filtering, and frequency compounding all offer the ability to improve target conspicuity by balancing the effects of imaging resolution, the signal-to-clutter ratio, and speckle texture, but these strategies rely on the ability to capture image quality at each desired frequency. We investigate the use of broadband linear frequency-modulated transmissions, also known as chirps, to expedite the interrogation of frequency-dependent tissue spatial coherence for real-time implementations of frequency-based adaptive imaging strategies. Chirp-collected measurements of coherence are compared to those acquired by individually transmitted conventional pulses over a range of fundamental and harmonic frequencies, in order to evaluate the ability of chirps to recreate conventionally acquired coherence. Simulation and measurements in a uniform phantom free of acoustic clutter indicate that chirps replicate not only the mean coherence in a region-of-interest but also the distribution of coherence values over frequency. Results from acquisitions in porcine abdominal and human liver models show that prediction accuracy improves with chirp length. Chirps are also able to predict frequency-dependent decreases in coherence in both porcine abdominal and human liver models for fundamental and pulse inversion harmonic imaging. This work indicates that the use of chirps is a viable strategy to improve the efficiency of variable frequency coherence mapping, thus presenting an avenue for real-time implementations for frequency-based adaptive strategies.

Current role of ultrasound in the diagnosis of hepatocellular carcinoma

Ultrasonography (US) is a major, sustainable hepatocellular carcinoma (HCC) surveillance method as it provides inexpensive, real-time, and noninvasive detection. Since US findings are based on pathological features, knowledge of pathological features is essential for delivering a correct US diagnosis. Recent advances in US equipment have made it possible to provide more information, such as malignancy potential and accurate localization diagnosis of HCC. Evaluation of malignancy potential is important to determine the treatment strategy, especially for small HCC. Diagnosis of blood flow dynamics using color Doppler and contrast-enhanced US is one of the most definitive approaches for evaluating HCC malignancy potential. Recently, a new Doppler microvascular imaging technique, superb microvascular imaging, which can detect Doppler signals generated by low-velocity blood flow, was developed. A fusion imaging system, another innovative US technology, has already become an indispensable technology over the last few years not only for US-guided radiofrequency ablation but also for the detection of small, invisible HCC. This article reviews the evidence on the use of ultrasound and contrast-enhanced ultrasound with Sonazoid for the practical management of HCC.

Imaging of suspected pulmonary embolism and deep venous thrombosis in obese patients

Obesity is a growing problem around the world, and radiology departments frequently encounter difficulties related to large patient size. Diagnosis and management of suspected venous thromboembolism, in particular deep venous thrombosis (DVT) and pulmonary embolism (PE), are challenging even in some lean patients, and can become even more complicated in the setting of obesity. Many obstacles must be overcome to obtain imaging examinations in obese patients with suspected PE and/or DVT, and to ensure that these examinations are of sufficient quality to diagnose or exclude thromboembolic disease, or to establish an alternative diagnosis. Equipment limitations and technical issues both need to be acknowledged and addressed. Table weight limits and scanner sizes that readily accommodate obese and even morbidly obese patients are not in place at many clinical sites. There are also issues with image quality, which can be substantially compromised. We discuss current understanding of the effects of patient size on imaging in general and, more specifically, on the imaging modalities used for the diagnosis and treatment of DVT and PE. Emphasis will be placed on the technical parameters and protocol nuances, including contrast dosing, which are necessary to refine and optimize images for the diagnosis of DVT and PE in obese patients, while remaining cognizant of radiation exposure. More research is necessary to develop consistent high-level evidence regarding protocols to guide radiologists, and to help them effectively utilize emerging technology.

An Adaptive Synthetic Aperture Method Applied to Ultrasound Tissue Harmonic Imaging

In recent years, the minimum variance (MV) beamformer has been highly regarded since it provides high resolution and contrast in B-mode ultrasound imaging compared with nonadaptive delay-and-sum (DAS) beamformer. However, the performance of MV beamformer is degraded in the presence of the noise due to inaccurate estimation of the covariance matrix resulting in low-quality images. The conventional tissue harmonic imaging (THI) offers multiple advantages over conventional pulse-echo ultrasound imaging, including enhanced contrast resolution and improved axial and lateral resolutions, but low signal-to-noise ratio (SNR) is a major problem facing this imaging method, which uses a fixed transmit focus and dynamic receive focusing (DRF). In this paper, a synthetic aperture method based on the virtual source, namely, bidirectional pixel-based focusing (BiPBF), has been combined with the MV beamformer and then applied to second-harmonic ultrasound imaging. The main objective is suppressing the noise level to enhance the performance of the MV beamformer in the harmonic imaging, especially in lower and deeper depths where the SNR is low. In addition, combining the BiPBF and MV weighting results in simultaneous improvement in imaging resolution and contrast, in comparison with the conventional methods: DRF (DAS), BiPBF (DAS), and DRF (MV). The performance of the proposed method is evaluated on simulated and experimental RF data. The THI is achieved using the pulse-inversion technique. The results of the simulated wire phantom demonstrate that the proposed beamformer can achieve the best lateral resolution, along different depths, compared with DRF (DAS), BiPBF (DAS), and DRF (MV) methods. The results of the simulated and experimental cyst phantoms show that the new beamformer improves the contrast ratio (CR) and contrast-to-noise ratio (CNR) of the resulting images. In results of simulated cyst phantom, in average, the new beamformer improves the CR and CNR of the cyst about (7.4 dB, 49%), (3.2 dB, 16%), and (5 dB, 26%) compared with DRF (DAS), BiPBF (DAS), and DRF (MV), respectively. In results of experimental cyst phantom, these relative improvements are about (4.2 dB, 22%), (1.7 dB, 7%), and (2.6 dB, 15%). In addition, BiPBF (MV) method offers improved edge definition of cysts in comparison with the other methods.

The diagnostic accuracy of ultrasonography for soft tissue lipomas: a systematic review

Background

Ultrasound has been used in the diagnosis of soft-tissue lesions for well over a decade. Lipomas are the most common, benign, soft-tissue tumor and comprise adipose tissue. The sensitivity and specificity of diagnosing lipomas on ultrasound vary greatly in the literature.

Purpose

To perform a systematic review on ultrasonography in soft-tissue lipomas to better ascertain the true diagnostic value of this test.

Material and Methods

A systematic review of the diagnostic value of ultrasound in lipomas was performed where possible in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search of the literature was conducted using several well-known databases Scopus®, PubMed®, Ovid® Medline, and Web of Science®.

Results

A total of 455 articles were identified in the initial literature search. Six papers were included in the final systematic review, which revealed an overall sensitivity and specificity of 86.87% (95% confidence interval [CI] = 82.14–90.73) and 95.95% (95% CI = 93.75–97.54), respectively.

Conclusion

Ultrasound is a useful tool in the diagnosis of superficial lipomas with good sensitivity and even better specificity and should continue to be the first line investigation in such cases.

Sonographic Detection of the Normal Appendix

The purpose of this study was to determine if the application of tissue harmonic imaging (THI) and real-time spatial compounding (RTSC) would result in a significant difference in the rate of detection and quality of visualization of the normal appendix. Subjects were scanned using the experimental method (the combination of THI and RTSC) and the conventional method (without THI and RTSC). The rate of detection was 85% with the experimental method and 66% with the conventional method. The quality of visualization was measured across three scales—visualized length, walls, and lumen—with a total score equal to the sum of the three scales. The experimental method demonstrated a significant difference in visualized length and total score. The mean score for length using the conventional method was 2.18 compared with 2.56 for the experimental method. The mean score for all three scales for the conventional method was 7.97 compared with 8.67 for the experimental method.

Focal hepatic lesions characterisation by different sonographic techniques: a prospective analysis

INTRODUCTION

Ultrasound is usually the first diagnostic investigation for the assessment of liver lesions. Apart from conventional sonography (CS), new grey-scale sonographic techniques have been developed which have increased the application of ultrasound in liver imaging. The present study was undertaken to compare image quality of CS, real-time compound sonography (RTCS), tissue harmonic sonography (THS) and tissue harmonic compound sonography (THCS) in focal liver lesions.

MATERIALS AND METHODS

100 patients with focal hepatic lesions were enroled. Lesions were divided into solid and cystic group. Solid lesions were evaluated for lesion conspicuity and elimination of artefacts. For cystic lesions, lesion conspicuity, posterior acoustic enhancement and internal echoes within the lesion were evaluated. Grading was done using 3-5-point scales. Overall image quality was assessed depending on the total points.

RESULTS

78 solid and 22 cystic liver lesions were included. THCS showed superior results for lesion conspicuity, elimination of artefacts and overall image quality in solid lesions. RTCS showed similar results as THCS for lesion conspicuity and overall image quality in solid lesions. THS gave better results in cystic lesions for all imaging parameters. Results of THCS though slightly inferior, showed no significant difference from THS, in cystic lesions. CS was found to have least diagnostic value in characterisation.

CONCLUSIONS

For evaluation of focal hepatic lesions, a combination of compound and harmonic sonography, i.e. THCS, is the preferred sonographic technique.

Current status of tissue harmonic imaging in endoscopic ultrasonography (EUS) and EUS-elastography in pancreatobiliary diseases

Endoscopic ultrasonography (EUS) has high spatial and contrast resolution, and is thought to be one of the most reliable and efficient diagnostic modalities for pancreatobiliary diseases. Recent progress in EUS, especially in the development of the electronic scanning method, has enabled the application of several utilities and software of a high-end transabdominal ultrasound apparatus as an image-enhanced EUS. Tissue harmonic imaging (THI) is a novel US acquisition method that provides better US images by using second harmonic signals. The potential advantages of THI are improved lateral resolution, reduced side lobe artifact and an increased signal-to-noise ratio. EUS-elastography is another novel technique that provides information about the distributed pattern of tissue hardness. Clinical benefits of EUS-elastography for the differential diagnosis of pancreatic tumors and the evaluation of pancreatic fibrosis have been reported. It is necessary to develop a unified and objective method of imaging and analysis to increase the use of EUS-elastography in the future.

The role of US in the evaluation of clinically suspected ulnar collateral ligament injuries of the thumb: spectrum of findings and differential diagnosis

Injury to the ulnar collateral ligament (UCL) complex of the thumb is a common traumatic lesion that requires prompt imaging evaluation for adequate treatment. In this article, we review the role of ultrasound in diagnosis and illustrate the spectrum of both static and dynamic findings related to the UCL injuries. We also describe a number of alternative diagnoses in the vicinity of the first metacarpophalangeal joint that may present clinically as pseudoligamentous lesions in a trauma setting.

Transmit beamforming for optimal second-harmonic generation

A simulation study of transmit ultrasound beams from several transducer configurations is conducted to compare second-harmonic imaging at 3.5 MHz and 11 MHz. Second- harmonic generation and the ability to suppress near field echoes are compared. Each transducer configuration is defined by a chosen f-number and focal depth, and the transmit pressure is estimated to not exceed a mechanical index of 1.2. The medium resembles homogeneous muscle tissue with nonlinear elasticity and power-law attenuation. To improve computational efficiency, the KZK equation is utilized, and all transducers are circular-symmetric. Previous literature shows that second-harmonic generation is proportional to the square of the transmit pressure, and that transducer configurations with different transmit frequencies, but equal aperture and focal depth in terms of wavelengths, generate identical second-harmonic fields in terms of shape. Results verify this for a medium with attenuation f1. For attenuation f1.1, deviations are found, and the high frequency subsequently performs worse than the low frequency. The results suggest that high frequencies are less able to suppress near-field echoes in the presence of a heterogeneous body wall than low frequencies.

Coded tissue harmonic imaging with nonlinear chirp signals

Coded tissue harmonic imaging with pulse inversion (CTHI-PI) based on a linear chirp signal can improve the signal-to-noise ratio with minimizing the peak range sidelobe level (PRSL), which is the main advantage over CTHI with bandpass filtering (CTHI-BF). However, the CTHI-PI technique could suffer from motion artifacts due to decreasing frame rate caused by two firings of opposite phase signals for each scanline. In this paper, a new CTHI method based on a nonlinear chirp signal (CTHI-NC) is presented, which can improve the separation of fundamental and harmonic components without sacrificing frame rate. The nonlinear chirp signal is designed to minimize the PRSL value by optimizing its frequency sweep rate and time duration. The performance of the CTHI-NC method was evaluated by measuring the PRSL and mainlobe width after compression. From the in vitro experiments, the CTHI-NC provided the PRSL of -40.6 dB and the mainlobe width of 2.1 μs for the transmit quadratic nonlinear chirp signal with the center frequency of 2.1 MHz, the fractional bandwidth at -6 dB of 0.6 and the time duration of 15 μs. These results indicate that the proposed method could be used for improving frame rates in CTHI while providing comparable image quality to CTHI-PI.

Advances and utility of diagnostic ultrasound in musculoskeletal medicine

Musculoskeletal ultrasound (US) can serve as an excellent imaging modality for the musculoskeletal clinician. Although MRI is more commonly ordered in the United States for musculoskeletal problems, both of these imaging modalities have advantages and disadvantages and can be viewed as complementary rather than adversarial. For diagnostic US, relative recent advances in technology have improved ultrasound’s ability to diagnose a myriad of musculoskeletal problems with enhanced resolution. The structures most commonly imaged with diagnostic musculoskeletal US, include tendon, muscle, nerve, joint, and some osseous pathology. This brief review article will discuss the role of US in imaging various common musculoskeletal disorders and will highlight, where appropriate, how recent technological advances have improved this imaging modality in musculoskeletal medicine. Additionally, clinicians practicing musculoskeletal medicine should be aware of the ability as well as limitations of this unique imaging modality and become familiar with conditions where US may be more advantageous than MRI.

Coded excitation for ultrasound tissue harmonic imaging

Coded excitation can improve the signal-to-noise ratio (SNR) in ultrasound tissue harmonic imaging (THI). However, it could suffer from the increased sidelobe artifact caused by incomplete pulse compression due to the spectral overlap between the fundamental and harmonic components of ultrasound signal after nonlinear propagation in tissues. In this paper, three coded tissue harmonic imaging (CTHI) techniques based on bandpass filtering, power modulation and pulse inversion (i.e., CTHI-BF, CTHI-PM, and CTHI-PI) were evaluated by measuring the peak range sidelobe level (PRSL) with varying frequency bandwidths. From simulation and in vitro studies, the CTHI-PI outperforms the CTHI-BF and CTHI-PM methods in terms of the PRSL, e.g., -43.5dB vs. -24.8dB and -23.0dB, respectively.

Mechanical and clinical performance of pulse-inversion tissue harmonic imaging in the superficial region

PURPOSE

To compare image quality between fundamental imaging (FI; transmitted and received frequencies 8.0 and 9.0 MHz, respectively) and pulse-inversion tissue harmonic imaging (PI-THI; transmitted frequencies 4.0 and 4.5 MHz, respectively) within 40 mm of the surface of the probe, we tested axial, lateral, and contrast resolution.

METHODS

The axial and lateral resolution were tested by use of a tissue-mimicking test object. For contrast resolution, milk agar blocks of different concentration were used for the comparison test.

RESULTS

The lateral resolution was significantly improved by use of PI-THI at a depth of 20 to 40 mm from the surface of the phantom. Axial resolution was not reduced by use of PI-THI compared with FI. The value of the contrast index was higher in PI-THI than in FI. The researchers also evaluated the two modes clinically, by comparing the visibility of 170 cervical lymph nodes (identification of lymph node, echogenic hilus, parenchymal echogenicity). The results revealed significant advantages of PI-THI over FI for three features.

CONCLUSION

This study suggests that PI-THI might be mechanically and clinically useful in the superficial region.

Musculoskeletal sonography of the normal foot

Traumatic, degenerative and rheumatological injuries of the foot are common and can be managed by an ever increasing number of treatments and surgical interventions. High-frequency sonography is inexpensive, portable and is unique in allowing true dynamic assessment of the ligamentous, muscular and tendinous structures. The ultrasound technique demonstrates a steep learning curve and requires detailed knowledge of the foot anatomy. Ultrasound assessment plays an important role in the diagnosis and management of injuries of these structures by guiding rehabilitation and surgical intervention without delay. However, intimate knowledge of the ultrasound appearances of the foot anatomy and normal variants is paramount to correctly identify pathological conditions. We describe the normal sonographic appearances of the foot musculoskeletal structures with MR correlation including joints and their ligaments, dorsal and plantar surfaces of the foot, and the arches of the foot and their supporting structures.

Tissue non-linearity

The propagation of acoustic waves is a fundamentally non-linear process, and only waves with infinitesimally small amplitudes may be described by linear expressions. In practice, all ultrasound propagation is associated with a progressive distortion in the acoustic waveform and the generation of frequency harmonics. At the frequencies and amplitudes used for medical diagnostic scanning, the waveform distortion can result in the formation of acoustic shocks, excess deposition of energy, and acoustic saturation. These effects occur most strongly when ultrasound propagates within liquids with comparatively low acoustic attenuation, such as water, amniotic fluid, or urine. Attenuation by soft tissues limits but does not extinguish these non-linear effects. Harmonics may be used to create tissue harmonic images. These offer improvements over conventional B-mode images in spatial resolution and, more significantly, in the suppression of acoustic clutter and side-lobe artefacts. The quantity B/ A has promise as a parameter for tissue characterization, but methods for imaging B/ A have shown only limited success. Standard methods for the prediction of tissue in-situ exposure from acoustic measurements in water, whether for regulatory purposes, for safety assessment, or for planning therapeutic regimes, may be in error because of unaccounted non-linear losses. Biological effects mechanisms are altered by finite-amplitude effects.

New technologies applied to ultrasound diagnosis of sports injuries

INTRODUCTION

The aim of this study was to compare the ultrasound images of different soft tissue lesions from two different portable sonography devices: a conventional portable sonography device (ultrasound [US]-A, Micromaxx model; Sonosite Inc., Bothell, WA, USA), and a recently marketed compact device (US-B, Logiq e; General Electric Healthcare, Wauwatosa, WI, USA). The US-B device uses the new technologies of tissue harmonic imaging, real-time compound ultrasound, panoramic view, three-dimensional imaging, and virtual convex imaging.

METHODS

We compared ultrasound images of six different types of soft tissue lesions (muscle contusion, muscle strain, patellar tendinosis, calcifying patellar tendinosis, rupture of the lateral internal ligament of the knee, and deep infrapatellar synovial bursa), from six different subjects. Analysis of images was performed by the same ultrasound specialist. In accordance with the classical criteria for ultrasound studies, the following quantitative indicators and parameters of ultrasound quality were used to evaluate the images: degree of echogenicity, size of the lesion area, aspect, shape, borders, and overall visualization.

RESULTS

In muscle lesions due to contusion, not only is the edematous area better visualized with the new system, but definition of hemorrhagic area borders and their content is especially increased. In lesions of the tendons, the new system affords better definition of the borders of the hypoechogenic area of tendinous degeneration and perfect visualization of the extension of the damaged area using a panoramic study. Sonographic study of ligaments with chronic lesions permits visualization of scar areas. Finally, use of the new system with a small synovial bursa shows the content of the bursa and thickness of the walls more clearly.

CONCLUSION

Overall, the quantitative indicators and parameters of image quality performed in this study of common sports lesions demonstrate the improvement in visualization of damaged soft tissues with the new technologies now incorporated into portable sonography devices.

European obesity and the radiology department. What can we do to help?

Obesity is a chronic disease that is now a global epidemic. The numbers of obese people are exponentially rising in Europe, and it is projected that in Europe by 2010 there will be 150 million obese people. The obesity-related health crisis does not only affect adults, with one in four European children now overweight. Radiologists, both adult and paediatric, need to be aware of the magnitude of the problem, and obese patients cannot be denied radiologic evaluation due to their size. Missed diagnosis, appointment cancellation and embarrassing situations for patients when they are referred for a radiological examination for which they are not suitable are all issues that can be avoided if careful provision is made to accommodate the needs of the obese patient requiring radiologic evaluation. This paper will discuss the epidemiology of obesity and the role of radiology in the assessment of obesity and disorders of fat metabolism. The limitations obesity poses to current radiological equipment and how the radiologist can optimise imaging in the obese patient will be described. Dose reference levels and dose control are discussed. Examples of how obesity both hinders and helps the radiologist will be illustrated. Techniques and pre-procedural preparation to help the obese patient in the interventional suite are discussed.

Phase inversion harmonic imaging improves assessment of renal calculi: a comparison with fundamental gray-scale sonography

PURPOSE

To compare phase inversion harmonic imaging (PIHI) with fundamental imaging (FI) in the evaluation of renal calculi.

METHODS

Thirty adult patients with renal calculi (17 men, 13 women; mean age 44 years [range, 25-71]) underwent transabdominal sonographic examination of the urinary system. Both kidneys and renal calculi were examined with PIHI and FI. Overall renal conspicuity, calculus visibility, and clarity of posterior shadowing were assessed subjectively using a 4-point scale (0 being the worst, 3 being the best). The maximum diameter of the calculi was measured using both techniques. The effect of body mass index on qualitative scoring and quantitative measurements was evaluated.

RESULTS

PIHI improved overall renal conspicuity compared with FI (p < 0.001). The visibility of the calculi and clarity of posterior shadowing were significantly better with PIHI than with FI (p < 0.001 for both parameters). The maximum diameter of calculi was larger with PIHI than with FI (p < 0.001). The superiority of PIHI over FI regarding overall conspicuity of the kidney, visibility of the calculus, and clarity of posterior shadowing scores increased in the obese group (p < 0.001 for all 3 parameters). The mean calculus diameter difference between the 2 techniques was significantly higher in the obese group.

CONCLUSION

The routine use of PIHI is recommended in the evaluation of renal calculi.

Comparing differential tissue harmonic imaging with tissue harmonic and fundamental gray scale imaging of the liver

OBJECTIVE

The purpose of this study was to compare fundamental gray scale sonography, tissue harmonic imaging (THI), and differential tissue harmonic imaging (DTHI) for depicting normal and abnormal livers.

METHODS

The in vitro lateral resolution of DTHI, THI, and sonography was assessed in a phantom. Sagittal and transverse images of right and left hepatic lobes of 5 volunteers and 20 patients and images of 27 liver lesions were also acquired. Three independent blinded readers scored all randomized images for noise, detail resolution, image quality, and margin (for lesions) on a 7-point scale. Next, images from the same location obtained with all 3 modes were compared blindly side by side and rated by all readers. Contrast-to-noise ratios were calculated for the lesions, and the depth of penetration (centimeters) was determined for all images.

RESULTS

In vitro, the lateral resolution of DTHI was significantly better than fundamental sonography (P = .009) and showed a trend toward significance versus THI (P = .06). In the far field, DTHI performed better than both modes (P < .04). In vivo, 450 images were scored, and for all parameters, DTHI and THI did better than sonography (P < .002). Differential tissue harmonic imaging scored significantly higher than THI with regard to detail resolution and image quality (P < .001). The average increase in penetration with THI and DTHI was around 0.6 cm relative to sonography (P < .0001). The contrast-to-noise ratio for DTHI showed a trend toward significance versus THI (P = .06). Side-by-side comparisons rated DTHI better than THI and sonography in 54% of the cases (P < .007).

CONCLUSIONS

Tissue harmonic imaging and DTHI do better than fundamental sonography for hepatic imaging, with DTHI being rated the best of the 3 techniques.

Ultrasonography of the pancreas. 2. Harmonic imaging

Tissue harmonic imaging (THI) is a relatively new ultrasonographic imaging modality which has been implemented in many modern scanners. As several previous studies have pointed out, THI can help to overcome some shortcomings of conventional B-mode ultrasonography (US). The aim of this article is to give a compact summary of the potentials of THI, focused on pancreatic imaging. Beginning with a recapitulation of the technical background of THI, the particularities and suitable applications of THI in US of the pancreas are discussed. Examination protocols and typical indications are presented together with example images. Finally, new trends and developments in B-mode sonography of the pancreas such as panorama US, compound imaging, and photopic US are mentioned.

Plain abdominal radiography with transabdominal native tissue harmonic imaging ultrasonography vs unenhanced computed tomography in renal colic

OBJECTIVE

To compare plain film kidney, ureter and bladder radiography (KUB) with transabdominal native tissue harmonic imaging ultrasonography (NTHI-US) vs unenhanced computed tomography (CT) for the diagnosis of urinary calculi in patients with acute flank pain.

PATIENTS AND METHODS

In all, 112 patients who presented to the urological department with clinical suspicion of ureteric calculi were included. These patients had KUB with NTHI-US and unenhanced CT. Of the 112 patients, 14 were lost to follow-up and therefore excluded. For the remaining 98 patients (53 men, 45 women; mean age 43.3 years, range: 19-74) the KUB with NTHI-US findings were compared with the CT findings, which served as the 'gold standard'.

RESULTS

In all, 75 patients were confirmed to have ureteric calculi. KUB with transabdominal NTHI-US detected 72 of the 75 patients with calculi (sensitivity 96%, specificity 91%, and accuracy 95%). Unenhanced CT detected urolithiasis in all 75 patients (sensitivity, specificity and accuracy of 100%). Both techniques showed further extra-urinary pathologies.

CONCLUSION

This prospective study shows that CT is the most accurate technique for detecting urolithiasis. However, KUB with transabdominal NTHI-US is an alternative to unenhanced CT with comparable results.

Aberration in nonlinear acoustic wave propagation

Theory and simulations are presented indicating that imaging at the second-harmonic frequency does not solve the problem of ultrasonic wave aberration. The nonlinearity of acoustic wave propagation in biological tissue is routinely exploited in medical imaging because the improved contrast resolution leads to better image quality in many applications. The major sources of acoustic noise in ultrasound images are aberration and multiple reflections between the transducer and tissue structures (reverberations), both of which are the result of spatial variations in the acoustic properties of the tissue. These variations mainly occur close to the body surface, i.e., the body wall. As a result, the nonlinearly generated, second harmonic is believed to alleviate both reverberation and aberration because it is assumed that the second harmonic is mainly generated after the body wall. However, in the case of aberration, the second harmonic is generated by an aberrated source. Thus the second harmonic experiences considerable aberration at all depths, originating from this source. The results in this paper show that the second harmonic experiences similar aberration as its generating source, the first harmonic.

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.

Role of tissue harmonic imaging in focal hepatic lesions: comparison with conventional sonography

BACKGROUND

The purpose of the present study was to compare iissue harmonic imaging (THI) and conventional sonography in focal hepatic lesions.

METHODS

Fifty patients with focal hepatic lesions were enrolled for study. Conventional grayscale and THI was performed in all the patients and two sets of images of the lesions were recorded (one each for THI and conventional) and assessed for fluid-solid differentiation, detail and overall image quality. These images were compared with conventional sonographic images and graded better, same or worse as per the case. Lesions were confirmed by fine-needle aspiration cytology (FNAC)/surgery/other modalities such as computed tomography (CT) or magnetic resonance imaging (MRI).

RESULTS

Out of 50 patients with focal hepatic lesions, 21 patients had metastatic lesions (two single; 19 multiple) five patients had hepatocellular carcinoma (HCC), five patients had hydatid cysts, nine had simple hepatic cyst whereas five patients had liver abscess, three had focal fatty infiltration; and lymphoma and hemangioma were seen in one patient each. The first observer ranked THI better than standard sonography in 40 patients (80%) for fluid-solid differentiation, in 38 (76%) for detail and in 39 (78%) for overall image quality. The second observer ranked THI better than standard sonography in 39 patients (78%) for fluid-solid differentiation, in 40 (80%) for detail and in 42 (84%) for overall image quality. Tissue harmonic imaging provided additional information in eight patients (16%) and resulted in treatment alteration in three patients (6%).

CONCLUSION

Tissue harmonic imaging was significantly better than conventional sonography for fluid-solid differentiation, detail and total image quality in focal hepatic lesions, especially in obese patients and patients with poor acoustic window.

Diagnostic value of tissue harmonic imaging compared with conventional sonography

The purpose of this study was to determine if tissue harmonic imaging (THI) produced diagnostic images more frequently than conventional sonography. A prospective study was performed on 33 patients, to compare the diagnostic value of THI with conventional sonography. Each examination was performed using THI (transmit frequency=2.0 MHz, receive frequency=4.0 MHz) and conventional sonography at 2.5 and 4.0 MHz. The different sonographic techniques were then graded as to whether they produced diagnostic images. THI produced diagnostic images in 33 of 33 examinations (100%), 2.5 MHz conventional sonography produced diagnostic images in 26 of 33 examinations (79%), and 4.0 MHz conventional sonography produced diagnostic images in 26 of 33 examinations (79%). THI produced diagnostic images significantly more frequently than 2.5 MHz conventional sonography (p=.0233) and 4.0 MHz conventional sonography (p=.0233). The THI technique produced diagnostic images more frequently than conventional sonography.

Transabdominal pulse inversion harmonic imaging improves assesment of ovarian morphology in virgin patients with PCOS: comparison with conventional B-mode sonography

OBJECTIVE

In virgin policystic ovary syndrome (PCOS) patients transabdominal sonography is the preferential method of the pelvic examination. The purpose of this study was to determine ovarian morphology by the transabdominal route by pulse inversion harmonic imaging (PIHI) in virgin PCOS patients and to compare the diagnostic image quality with conventional B-mode ultrasonography (CBU).

METHODS

Fifty-two ovaries in 26 virgin patients were evaluated by the transabdominal approach. Each ovary was examined using both PIHI and CBU. The sharpness of the follicular cysts walls, degree of internal echo definitions of the follicle cysts and overall ovarian conspicuity was assessed subjectively, using 4 point scoring (0, being worst; 3, being best score). The number of countable follicles, the size of largest and smallest ovarian follicle and ovarian volumes were assessed quantitively by both techniques. The effect of body mass index (BMI) on qualitative and quantitative scoring was evaluated.

RESULTS

The sharpness of the cyst wall and internal echo structure was significantly better with PIHI than with CBU (P < 0.001 P < 0.001 and P < 0.001, respectively). PIHI improved overall ovarian conspicuity in 41 (78.8%) of 52 examination. The number of countable follicles was significantly lower with CBU (P < 0.001). The maximum diameter of the largest follicle was larger with PIHI sonography to compared CBU (P < 0.001). Mean ovarian volume was significantly larger with CBU (P < 0.001). When data were analyzed separately according to BMI, number of non-diagnostic overall ovarian conspicuity scores with CBU was markedly high in obese patients (88% with CBU versus 3.8% with PIHI). On the other hand, mean number of countable follicles with CBU became much more lower in the obese group (P < 0.001).

CONCLUSION

In virgin PCOS patients, when compared to transabdominal CBU, PIHI significantly improved the detection of ovarian follicles, especially in high BMI obese subjects, through increased contrast sensitivity for cystic structures and decreased intrafollicular artifactual echoes. Transabdominal ultrasonographic examination by PIHI mode can contribute to the evaluation of ovaries.

[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.

Phase-inversion tissue harmonic imaging compared with conventional B-mode ultrasound in the evaluation of pancreatic lesions

The aim of this study was to compare the diagnostic sensitivity, specificity, and image quality of conventional B-mode US (BM) and phase-inversion tissue harmonic imaging (PTHI) regarding pancreatic pathology. In a prospective study, 107 patients, aged between 28 and 85 years, underwent US examinations of the pancreas with both BM and PTHI in a randomly chosen order. As diagnostic reference, either contrast-enhanced CT or MRI examinations of the upper abdomen were obtained in all patients. Sensitivity and specificity were evaluated using the Student's t test. Differences in overall image quality, lesion conspicuity, fluid-solid differentiation, and delineation of the pancreatic tail were analyzed using Wilcoxon's signed ranks test and Bowker's symmetry test. Sixteen of 107 examined patients (15%) were non-diagnostic and excluded due to technical limitations such as abdominal gas. A total of 60 pancreatic lesions (cysts, acute pancreatitis, dilatation of the pancreatic duct, calcifications, and solid tumors) were diagnosed by CT or MRI. Phase-inversion tissue harmonic imaging had a higher sensitivity of 70% (14 of 20) than BM (60%; 24 of 40) for the detection of pancreatic lesions; however, the difference was not statistically significant ( p=0.46). In the assessment of lesions <1 cm of size, PTHI had a sensitivity of 70% and BM 46.7%, whereby the difference again was not statistically significant. Phase-inversion tissue harmonic imaging proved to be superior to BM regarding overall image quality ( p<0.0001), lesion conspicuity ( p=0.0045), and fluid-solid differentiation ( p=0.0002), as well as the delineation of the pancreatic tail ( p<0.0001). These differences were statistically significant. The statistically significant improvement of image quality with regards to lesion conspicuity, fluid-solid differentiation, and delineation of the pancreatic tail favors the use of PTHI when evaluating the pancreas with US. Sensitivity for pancreatic lesions is increased with PTHI in comparison with conventional sonography (BM), especially in lesions <1 cm in diameter, although the difference was not statistically significant.

Comparison of conventional sonography, real-time compound sonography, tissue harmonic sonography, and tissue harmonic compound sonography of abdominal and pelvic lesions

OBJECTIVE

The purpose of this study was to compare conventional sonography, real-time spatial compound sonography, tissue harmonic sonography, and tissue harmonic sonography merged with compound sonography for overall image quality, lesion conspicuity, and elimination of artifacts. SUBJECTS AND METHODS. In this study, 150 lesions in 122 randomly selected patients with various abdominal and pelvic lesions were evaluated. For each lesion, sonograms were obtained with four techniques: conventional sonography, real-time spatial compound sonography, tissue harmonic sonography, and tissue harmonic compound sonography. All images were reviewed and graded independently by two observers for overall image quality, lesion conspicuity, and elimination of artifacts.

RESULTS

Statistical analysis showed that for overall image quality, lesion conspicuity, and elimination of artifacts, tissue harmonic compound sonography was significantly superior to all of the other techniques; real-time spatial compound sonography was better than tissue harmonic sonography; and conventional sonography was the least valuable of all (p < 0.001). When data were analyzed separately according to lesion types, tissue harmonic compound sonography was significantly superior for revealing stone diseases, liver cysts, gallbladder polyps, and uterine myomas. For the remainder of lesion groups, spatial compounding was superior to tissue harmonic sonography for all aspects of evaluation, and conventional sonography was the least valuable (p < 0.05).

CONCLUSION

In abdominal and pelvic scanning, tissue harmonic compound sonography provides the best overall image quality, best lesion conspicuity, and least artifacts of all the evaluated imaging modes. Spatial compound sonography is better than tissue harmonic sonography for the evaluation of lesions in general, despite some differences among lesion groups.

Suspected rotator cuff lesions: tissue harmonic imaging versus conventional US of the shoulder

PURPOSE

To compare tissue harmonic imaging (THI) of the shoulder with conventional ultrasonography (US) in patients suspected of having rotator cuff lesions.

MATERIALS AND METHODS

THI and conventional US images were obtained in 50 patients suspected of having rotator cuff lesions. Images were graded for visibility of acromioclavicular (AC) joint surfaces and rotator cuff tendon contours and substances: Grade 1 meant poor; grade 2, moderate; and grade 3, good visibility. Accuracy, sensitivity, and specificity of the diagnosis of AC joint osteoarthritis and accuracy of the diagnosis and rates of underestimation and overestimation of the extent of rotator cuff tears were evaluated. Visibility grade differences were evaluated with the Wilcoxon signed rank test. The McNemar test was used to assess differences in diagnoses. Magnetic resonance (MR) arthrography was the reference standard.

RESULTS

Mean visibility grades for readers 1 and 2, respectively, were as follows: for AC joint bone surfaces, 2.1 and 2.0 with THI and 1.7 (P =.010) and 1.7 (P =.16) with conventional US; for AC joint capsule surfaces, 2.2 and 1.9 with THI and 1.8 (P =.005) and 1.8 (P =.34) with US; for supraspinatus tendon contour, 2.6 and 2.2 with THI and 2.1 (P =.001) and 1.9 (P =.055) with US; for supraspinatus tendon substance, 2.2 and 1.9 with THI and 2.0 (P =.036) and 1.7 (P =.070) with US; for subscapularis tendon contour, 2.4 and 2.1 with THI and 2.2 (P =.07) and 2.0 (P =.25) with US; and for subscapularis tendon substance, 1.8 and 1.7 with THI and 2.0 (P =.86) and 1.7 (P =.91) with US. Diagnostic accuracies for the supraspinatus tendon for readers 1 and 2, respectively, were 84% and 74% with THI and 86% and 70% with US (P >.99 for both readers). Corresponding values for the subscapularis tendon were 78% and 72% with THI and 64% (P =.27) and 52% (P =.006) with US.

CONCLUSION

Joint and tendon surface visibility improves with THI, as compared with the visibility achieved with conventional US. THI is superior to conventional US for diagnosis of subscapularis tendon abnormalities.

A review of nonconventional ultrasound techniques and contrast-enhanced ultrasonography of noncardiac canine disorders

Modern ultrasound contrast media are gas-containing stabilized microbubbles that remain intact in the circulating blood for several minutes after intravenous injection and increase the intensity of the backscattered ultrasound. When the microbubbles disappear from the blood, they can be detected in the parenchyma of the liver and the spleen for about 30 more minutes (late liver- and spleen-specific phase). The insonated microbubbles produce second harmonic ultrasound frequencies, whose detection requires nonconventional ultrasound modalities such as pulsed inversion imaging. Nonconventional ultrasound techniques can also be used without microbubbles because second harmonics can be generated by ultrasound in tissues as well. The physical principles and advantages of nonconventional ultrasound techniques are described. The circulating microbubbles can be used not only to enhance weak Doppler signals, but also to perform dynamic contrast studies. Contrast-enhanced dynamic ultrasound studies--similar to contrast-enhanced CT and MRI examinations--have been used in humans to characterize lesions noninvasively (i.e., without biopsies) found during conventional ultrasound examinations. To map the distribution of contrast medium in a nodule or in an organ, specific scanning techniques such as stimulated acoustic emission have been developed. Stimulated acoustic emission occurs when high acoustic pressure ultrasonic waves disrupt the stationary or slowly moving microbubbles. This results in the release of a large amount of harmonic ultrasound frequencies. When the stimulated acoustic emission technique is used for dynamic studies, scanning must be interrupted several times to allow the microvasculature of the lesion to refill with microbubbles (interval delay imaging). The contrast patterns of malignant and benign hepatic nodules in humans have been the most intensively studied. Another type of dynamic study in humans measures the transit time of the contrast medium; that is, how fast the peripherally injected microbubbles reach the hepatic veins. Hepatic cirrhosis can be differentiated from other diffuse parenchymal liver diseases by a shorter transit time. Introducing nonconventional ultrasound techniques and ultrasound contrast media in veterinary diagnostic imaging may have potential value; however, intensive research should be carried out before ultrasound contrast agents can routinely be used in clinical practice.

A comparison of image quality between tissue harmonic imaging and fundamental imaging with an electronic radial scanning echoendoscope in the diagnosis of pancreatic diseases

BACKGROUND

The availability of an electronic radial scanning echoendoscope has facilitated the clinical use of tissue harmonic imaging. This study compares the quality of US images acquired by tissue harmonic imaging during electronic radial scanning EUS to those acquired by fundamental imaging.

METHODS

Electronic radial scanning EUS was performed in 108 patients with pancreatic lesions (58 cystic, 50 solid). US images acquired by fundamental imaging at a frequency of 7.5 MHz were compared with those acquired by tissue harmonic imaging by using transmitting and receiving frequencies of, respectively, 4.0 and 8.0 MHz at the same scanning plane. Cystic lesions were evaluated for boundary/septum and nodules, and solid lesions, for boundary and internal structure. US images acquired by tissue harmonic imaging and fundamental imaging during electronic radial scanning EUS were compared, by using a Likert scale for the respective evaluation criteria, by two independent endoscopists.

OBSERVATIONS

For cystic lesions, tissue harmonic images were significantly clearer than fundamental images for visualizing boundary and septum (p < 0.0001, both reviewers) and nodules (p = 0.0003, Reviewer 1; p = 0.0007, Reviewer 2). For solid lesions, tissue harmonic images were significantly clearer than fundamental images for visualizing boundary (p = 0.0003, Reviewer 1; p < 0.0001, Reviewer 2) and internal structures (p = 0.0003, Reviewer 1; p = 0.0009, Reviewer 2).

CONCLUSIONS

US images acquired by tissue harmonic imaging appear to be clearer compared with those acquired by fundamental imaging.

Original report. Sonographic evaluation of shoulder arthroplasty

OBJECTIVE

The objective of our study was to review our experience using sonography to evaluate the rotator cuff after arthroplasty. Diagnostic reliability, with respect to surgical findings, as well as subjective assessment of the examinations, including the usefulness of applications such as extended field-of-view imaging, photopic imaging, and tissue harmonic imaging, were reviewed.

CONCLUSION

We found sonography to be a useful method of imaging the rotator cuff after arthroplasty. Extended field-of-view imaging and tissue harmonic imaging aided in diagnosis by improving visualization of regional anatomic landmarks and increasing conspicuity of small tendon tears.