High-end Ultrasound Research Articles

Ultrasound evaluation of kidney and liver involvement in Bardet–Biedl syndrome

BackgroundBardet–Biedl syndrome (BBS) is a rare autosomal-recessive ciliopathy with pathogenic variants in 26 BBS genes. It affects multiple organs, including the kidney and liver, with varying degrees regarding extent and time of first manifestation. Structural renal anomalies are an early feature and end-stage kidney disease (ESKD) cumulates to 25% in adulthood. Early-onset hyperphagia-associated obesity is another major symptom and contributes to liver pathology, presenting as steatosis/fibrosis. Aim of this study is the evaluation of high-end ultrasound (US) technologies in BBS patients regarding their potential to discriminate liver and kidney tissue pathology at an early stage.Materials and methodsPatients with genetically proven BBS were recruited from the University Children’s Hospital of Essen and from BBS patient days hosted in Germany. Acute illness was an exclusion criterion. Clinical and laboratory data were extracted from patients’ digital records or medical letters. High-resolution ultrasound (US) imaging was utilized, including attenuation imaging (ATI), shear wave elastography (SWE) and dispersion (SWD) of liver tissue.Results49 BBS patients (24/49 male; 1.1–51.0 years, mean 17.8 years) were included in the study. Mean body weight (SDS 2.13 ± 1.33) and BMI (SDS 2.64 ± 1.18) were increased. Structural kidney abnormalities (dysplasia, cysts) were present in 75% (36/48), and persistent fetal lobulation in 44% (21/48). Renal function was impaired in 27% (13/49) of whom 3 had ESKD (kidney transplantation (n = 2), hemodialysis (n = 1)). Elevation of liver enzymes was detected in 38% (16/42). In 51% (25/49) ATI of liver tissue was increased, indicating hepatic steatosis, and correlated with BMI SDS, liver size, and enzymes. SWE was elevated in 61% (30/49), suggesting hepatic fibrosis, and it correlated with BMI and GGT. Patients with pathogenic variants in BBS10 showed a tendency towards higher ATI, reduced GFR, and higher BMI SDS.ConclusionsWe detected kidney and liver abnormalities in a higher percentage of BBS patients than previously reported, indicating a high sensitivity and diagnostic yield of the evaluated high-end US applications. ATI detected liver pathology early (partially prior to liver enzymes) and revealed differences related to the affected genes. Evidence of tissue pathology at an early stage may improve diagnostics and the evaluation of therapeutic approaches.

Hardware-Independent Deep Signal Processing: A Feasibility Study in Echocardiography.

Deep learning (DL) models have emerged as alternative methods to conventional ultrasound (US) signal processing, offering the potential to mimic signal processing chains, reduce inference time, and enable the portability of processing chains across hardware. This paper proposes a DL model that replicates the fine-tuned BMode signal processing chain of a high-end US system and explores the potential of using it with a different probe and a lower-end system. A deep neural network was trained in a supervised manner to map raw beamformed in-phase and quadrature component data into processed images. The dataset consisted of 30,000 cardiac image frames acquired using the GE HealthCare Vivid E95 system with the 4Vc-D matrix array probe. The signal processing chain includes depth-dependent bandpass filtering, elevation compounding, frequency compounding, and image compression and filtering. The results indicate that a lightweight DL model can accurately replicate the signal processing chain of a commercial scanner for a given application. Evaluation on a 15 patient test dataset of about three thousand image frames gave a structural similarity index measure of 98.56 ± 0.49. Applying the DL model to data from another probe showed equivalent or improved image quality. This indicates that a single DL model may be used for a set of probes on a given system that targets the same application, which could be a cost-effective tuning and implementation strategy for vendors. Further, the DL model enhanced image quality on a Verasonics dataset, suggesting the potential to port features from high-end US systems to lower-end counterparts.

Prospective Comparison of Handheld Ultrasound Devices from Different Manufacturers with Respect to B-Scan Quality and Clinical Significance for Various Abdominal Sonography Questions.

Handheld ultrasound (HHUS) devices have chiefly been deployed in emergency medicine, where they are considered a valid tool. The data situation is less clear in the case of internal questions in abdominal sonography. In our study, we investigate whether HHUS devices from different manufacturers differ in their B-scan quality, and whether any differences are relevant for the significance of an internal ultrasound examination. The study incorporated eight HHUS devices from different manufacturers. Ultrasound videos of seven defined sonographic questions were recorded with all of the devices. The analogue recording of the same findings with a conventional high-end ultrasound (HEUS) device served as an evaluation criterion. Then, the corresponding findings were played side by side and evaluated by fourteen ultrasound experts using a point scale (5 points = very good; 1 point = insufficient). The HHUS devices achieved relatively good results in terms of both the B-scan quality assessment and the ability to answer the clinical question, regardless of the manufacturer. One of the tested HHUS devices even achieved a significantly (p < 0.05) higher average points score in both the evaluation of B-scan quality and in the evaluation of clinical significance than the other devices. Regardless of the manufacturer, the HHUS devices performed best when determining the status/inferior vena cava volume and in the representation of ascites/free fluid. In various clinical abdominal sonography questions, HHUS systems can reliably reproduce findings, and are-while bearing their limitations in mind-an acceptable alternative to conventional HEUS systems. Irrespective of this, the present study demonstrated relevant differences in the B-scan quality of HHUS devices from different manufacturers.

Construct Validity and Reproducibility of Handheld Ultrasound Devices in Carotid Artery Diameter Measurement.

The construct validity and reproducibility of three commonly used handheld ultrasound (US) devices in measuring carotid arterial diameter was evaluated: Telemed MicrUs EXT-1H (Telemed, Vilnius, Lithuania), Butterfly iQ (Butterfly Network, Inc., Guilford, CT, USA) and Philips Lumify (Philips Healthcare, Best, The Netherlands). An in vitro setup was built to evaluate construct validity, compared with high-end US, and intra-observer variability of handheld US devices. Handheld devices showed a mean difference of 0.023 ± 0.030 cm, 0.012 ± 0.037 cm and 0.009 ± 0.046 cm for, respectively, Telemed, Butterfly and Lumify in comparison with high-end US devices. Intraclass agreement with the high-end system as well as intra-observer variability for handheld US devices was classified as excellent, with all values greater than 0.95. Subsequently, inter-observer variability of handheld US devices was investigated in an in vivo setup with 20 healthy volunteers. Inter-observer variability was classified as excellent for Telemed (0.901), good for Lumify (0.827) and moderate for Butterfly (0.684) with a difference of, respectively, 0.005 ± 0.031 cm, 0.020 ± 0.050 cm and -0.003 ± 0.033 cm. In conclusion, handheld US devices demonstrated an excellent construct validity and intra-observer variability. Additionally, excellent-to-good inter-observer variability for Telemed and Lumify was observed, and Butterfly demonstrated a moderate inter-observer agreement. These results indicate that handheld US devices are effective for measuring carotid arterial diameter.

Intrauterine Pregnancy Detection and Gestational Age Assessment During Early Pregnancy by a Handheld Point-Of-Care Ultrasound Device Compared to a High-End Ultrasound System. An Accuracy and Reliability Study.

Objective: The main objective of this study is the evaluation of the accuracy and reliability of a handheld point of care ultrasound device (POCUS-hd) for intrauterine pregnancy (IUP) detection compared to comprehensive reference transabdominal ultrasound (TU). The secondary objectives were to evaluate POCUS-hd for intrauterine pregnancy (IUP) detection compared to transabdominal and transvaginal ultrasound (TUTV), evaluate the inter-device agreement and inter-rater reliability of gestational age during early pregnancy. Methods: It is an observational transverse study with consecutive patient recruitment. Two blinded operators systematically used POCUS-hd and reference transabdominal ultrasound for IUP diagnosis. The accuracy of POCUS-hd for IUP diagnosis was expressed as sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV). The gestational age (GA) was assessed based on the crown-rump length. The reliability and agreement of gestational age evaluation were assessed by Bland-Altman plots, kappa statistic, and intraclass correlation coefficients (ICC). Results: POCUS-hd compared to TU had a sensitivity of 95-100%, a specifcity of 90-100%, PPV of 95-100% and NPV of 90-100%. Inter-rater agreement for IUP detection using POCUS-hd was very good, kappa=1.0; CI95% [0.9-1.0]. The inter-device agreement limits (mean difference ± 2SD) for GA were: -3 to +2.3 days by Operator 1, -3.4 to +3.3 days by Operator 2 for POCUS-hd vs. TU and -3.1 to +2.3 days for POCUS-hd versus TUTV. Conclusion: This handheld POCUS device is an accurate and reliable diagnostic tool that can be used for IUP positive findings and GA assessment during early pregnancy by clinicians in family planning settings or general practice.

The Point-of-Care Ultrasound (POCUS) by the Handheld Ultrasound Devices (HUDs) in the COVID-19 Scenario: a Review of the Literature.

The use of portable ultrasound (US) devices is increasing, due to its accessibility, versatility, non-invasiveness, and its significant support in the patient management, extending the traditional physical examination through the POCUS (point-of-care ultrasound). The pocket-size or handheld ultrasound devices (HUDs) can easily perform focused exams, not aiming to substitute for the high-end US systems (gold standard), since the HUDs usually have more limited functions. The HUDs are promising tools for the diagnosis, prognosis, and monitoring of the COVID-19 infection and its related disorders. In conclusion, the routine use of HUDs may ameliorate the management of COVID-19 pandemic, according to the guidelines for the POCUS approach and the procedures for the protection of the patients and the professionals.

124 Comparison of First-Pass Peripheral Intravenous Cannulation Using a Handheld Ultrasound Device to Using a Traditional High-End Ultrasound System: A Randomized Controlled Trial

As handheld ultrasound (US) devices have become more commonplace in the practice of emergency medicine (EM), this study aimed to compare the efficacy of a novel handheld ultrasound device (HHUD), the Butterfly IQ (Butterfly Network Inc., Guilford, CT), to that of a traditional high-end ultrasound system (HEUS), the Mindray TE7 (Mindray North America, Mahwah, NJ), in gaining peripheral intravenous (PIV) access on first attempt at an EM residency program.

Intraoperative Characterization of Pancreatic Tumors Using Contrast-Enhanced Ultrasound and Shear Wave Elastography for Optimization of Surgical Strategies.

To evaluate intraoperative contrast-enhanced ultrasound (IoCEUS) and intraoperative shear wave elastography (IoSWE) for characterization of focal pancreatic lesions (FPLs) in correlation with postoperative histologic results. Thereby, the impact of intraoperative ultrasound (US) on pancreas surgery was evaluated. Intraoperative CEUS and SWE data from 54 patients, who underwent pancreas surgery between 2017 and 2019, were analyzed retrospectively. Ultrasound examinations were performed with multifrequency linear/T-shaped transducers (3-9 MHz) on a high-end US device (LOGIQ E9; GE Healthcare, Chicago, IL). To analyze FPL stiffness by SWE, regions of interest were placed to measure the shear wave speed (meters per second) and stiffness (kilopascals). After intravenous bolus injections of 2.4 to 10 mL of sulfur hexafluoride microbubbles, a dynamic analysis of FPL microvascularization from arterial to late phases was performed using IoCEUS considering hypoenhancement/irregular vascularization of macrocystic/small solid FPL malignancy criteria. Ultrasound findings were correlated with postoperative histologic results. The impact of intraoperative US on surgery was documented in each case. Of 54 FPLs, IoCEUS could correctly characterize 39 of 39 malignant and 6 of 15 benign FPLs; IoSWE 29 of 39 as malignant and 7 of 15 as benign. Intraoperative CEUS's sensitivity was 100%; specificity, 40%; accuracy, 83.3%; positive predictive value, 81.3%; and negative predictive value, 100% (P < .05). Applying cutoff values of 3 m/s and 28.7 kPa, SWE's sensitivity was 74.4%; specificity, 46.7%; accuracy, 66.7%; positive predictive value; 78.4%; and negative predictive value, 41.2% for cancer detection (P < .05). The combined use of both techniques showed an accuracy rate of 76%, sensitivity of 74.4%, and specificity of 33.3%. In 29.6%, US results had an immediate impact on surgery. Intraoperative SWE and CEUS are highly valuable techniques for intraoperative characterization of FPLs. Although IoCEUS proved to be superior to IoSWE, the combined use can be helpful in particular cases.

Cardiac point-of-care to cart-based ultrasound translation using constrained CycleGAN.

The emerging market of cardiac handheld ultrasound (US) is on the rise. Despite the advantages in ease of access and the lower cost, a gap in image quality can still be observed between the echocardiography (echo) data captured by point-of-care ultrasound (POCUS) compared to conventional cart-based US, which limits the further adaptation of POCUS. In this work, we aim to present a machine learning solution based on recent advances in adversarial training to investigate the feasibility of translating POCUS echo images to the quality level of high-end cart-based US systems. We propose a constrained cycle-consistent generative adversarial architecture for unpaired translation of cardiac POCUS to cart-based US data. We impose a structured shape-wise regularization via a critic segmentation network to preserve the underlying shape of the heart during quality translation. The proposed deep transfer model is constrained to the anatomy of the left ventricle (LV) in apical two-chamber (AP2) echo views. A total of 1089 echo studies from 841 patients are used in this study. The AP2 frames are captured by POCUS (Philips Lumify and Clarius) and cart-based (Philips iE33 and Vivid E9) US machines. The dataset of quality translation comprises a total of 441 echo studies from 395 patients. Data from both POCUS and cart-based systems of the same patient were available in 122 cases. The deep-quality transfer model is integrated into a pipeline for an automated cardiac evaluation task, namely segmentation of LV in AP2 view. By transferring the low-quality POCUS data to the cart-based US, a significant average improvement of 30% and 34mm is obtained in the LV segmentation Dice score and Hausdorff distance metrics, respectively. This paper presents the feasibility of a machine learning solution to transform the image quality of POCUS data to that of high-quality high-end cart-based systems. The experiments show that by leveraging the quality translation through the proposed constrained adversarial training, the accuracy of automatic segmentation with POCUS data could be improved.

Evaluation of tablet ultrasound for routine abdominal interventional procedures

The aim of the study was to establish if a novel tablet ultrasound (US) may replace a high-end US machine during routine interventional radiology activities. Thirty consecutive patients were evaluated by two operators comparing the performance of the new US tablet system (VISIQ, Philips Healthcare) against a high-end US system (iU22, Philips Healthcare) using a curved probe (C5-2). A structured questionnaire was used to rank on a 4-point scale the ability of each system to locate a target as detected by previous examinations and visualize needles and path during an interventional procedure. Necessity for conversion from the tablet US to the high-end US system was registered; body mass index (BMI) was annotated for each patient. Agreement between the operators was found for every patient. Mean patient BMI was 25 (range 17-34). Image quality of the tablet US was considered insufficient in 1 case to visualize the target and in another case to visualize the needle. Mean target image quality was superior with the high-end US system, while needle visibility scored higher with the tablet US. Conversion to the high-end system was registered in 40% of cases: in most cases (66.6%) the decision was due to the absence of a dedicated needle guide for the tablet US. The novel tablet US was found to provide sufficient image quality for the majority of routine interventional procedures. Dedicated accessories and additional experience with this new generation US device may be needed to replace bulky high-end US systems.

Hand-Carried and High-End Ultrasound Systems are Equally Inferior to Abdominal Radiography and Multidetector Computed Tomography in the Diagnosis of Pneumoperitoneum

Pneumoperitoneum (PP) is a severe finding in emergency departments. Its quick and correct diagnosis is indispensable for the further treatment of patients. The aim of this study was to analyze the clinical value of abdominal ultrasound performed with a modern hand-carried ultrasound (HCU) device as well as with a high-end ultrasound (HUS) system in the diagnosis of PP in patients with acute abdominal pain. 31 patients with acute abdominal pain were enrolled in this study irrespective of their underlying disease, and examination with a latest generation HCU and a newest generation HUS was performed. Diagnosis of PP was based on findings of multidetector computed tomography (MDCT) and abdominal radiography (AR) as the standard of reference. The study was carried out by two independent and experienced examiners unaware of the diagnosis made by MDCT or AR. In five (16 %) patients PP was identified by MDCT and AR. Examination with HCU was calculated with a sensitivity and specificity of 80 % and 81 %, respectively. Examination with HUS yielded a sensitivity and specificity of 80 % and 89 %, respectively. PP can be detected by HCU and HUS with almost equal accuracy in patients with acute abdominal pain but both methods are inferior compared to MDCT and AR. However, HCU and HUS can accelerate the triage of patients and help to make decisions regarding the necessity of further examinations without the need for radiation and while reducing economic and logistic resources. 1. Pneumoperitoneum (PP) is a severe finding in emergency departments. 2. Hand-carried (HCU) and high-end (HUS) ultrasound systems can be helpful in detecting PP. 3. Abdominal radiography (AR) and multidetector computed tomography (MDCT) are superior in detecting PP. 4. HCU and HUS can accelerate the triage of patients. 5. HCU and HUS can be helpful when making decisions regarding the necessity of further examinations.

Physician‐performed ultrasound can accurately screen for a vulnerable intercostal artery prior to chest drainage procedures

Laceration of the intercostal artery during pleural procedures is a rare but serious complication. This study evaluates the utility of thoracic ultrasound (US) to screen for a vulnerable vessel compared with the gold standard computed tomography (CT). Before undergoing contrast-enhanced CT chest, thoracic US was performed on 50 patients with a high-end and portable machine, and an attempt made to visualize the vessel at three positions across the back to the axilla. These positions were labelled with radio-opaque fiducial markers. On both US and CT images, the location of the vessel at each position, relative to the overlying rib, was calculated and compared. The vessel was unshielded by a rib according to CT in 114 of the 133 positions. The sensitivity, specificity and negative predictive value of portable US to image the vessel, when it was within the intercostal space on CT, was 0.86, 0.30 and 0.27 respectively. The performance of a high-end machine was not significantly different. The median time required for a pulmonologist to locate the vessel was 42 s and 18 s for the portable and high-end US respectively. US can be used to screen for a vulnerable vessel prior to pleural procedures, in a time amenable to use in clinical practice. Further, it is achievable by a pulmonologist using a portable US machine. If thoracentesis or chest tube insertion is being performed on a patient at increased risk of bleeding, screening for a vulnerable vessel with US prior to beginning the procedure is recommended.

THU0428 Validity and reliability of 3D us for detection of erosions in patients with rheumatoid arthritis using MRI as gold standard

BackgroundUse of ultrasound (US) in rheumatology has increased over the last decade. Until recently, the only US modality used was 2D, which has been shown to be more sensitive for...

Reproducibility of phantom-based quality assurance parameters in real-time ultrasound imaging

In a large radiological center, the ultrasound (US) quality assurance (QA) program involves several professionals. Although the operator and the parameters utilized can contribute to the results, the selected QA parameters should still reflect the quality of the US scanner, not the measuring process. To evaluate the reproducibility of recommended phantom-based US QA parameters in a realistic environment. Six sonographers measured six high-end US scanners with 20 transducers using a general purpose phantom. Every transducer was measured altogether seven times, using one frequency per transducer. The QA parameters studied were homogeneity, visualization depth, vertical and horizontal distance measurements, axial and lateral resolution, and the correct visibility of anechoic and high-contrast masses. The evaluation of the homogeneity was based on visual observations. Inter-observer interquartile ranges were computed for the grading of the masses. For the other QA parameters, the mean inter- and intra-observer coefficients of variation (CoV) were calculated. In addition, the symmetry of the reverberations when imaging air with a clean transducer was checked. The mean inter-observer CoVs were: visualization depth 11 ± 4%, vertical distance 1.7 ± 0.4%, horizontal distance 1.4 ± 0.6%, axial resolution 22 ± 7%, and lateral resolution 16 ± 8%. The mean intra-observer values were about half of these values with similar standard deviations. The visual evaluation of the homogeneity and the symmetry of the reverberations produced false-positive findings in 5% of the cases, but were found useful in detecting a defective transducer. The grading of the masses had mean interquartile ranges of 20-30% of the grading scale. The inter-observer variability in measuring phantom-based QA parameters can be relatively high. This should be considered when implementing a phantom-based QA protocol and evaluating the results.

Ultrasound Doppler Score Correlates with OMERACT RAMRIS Bone Marrow Oedema and Synovitis Score in the Wrist Joint of Patients with Rheumatoid Arthritis

MRI is considered the standard of reference for advanced imaging in rheumatoid arthritis (RA). However, in daily clinical practice ultrasound (US) imaging with Doppler information is more versatile and often used for fast and dynamic assessment of joint inflammation. The aim was to compare low-field MRI scores with the US Doppler measurements in the wrist joint of patients with RA. Fifty consecutive patients with RA (46 women & 4 men) completed both low-field dedicated extremity MRI (E-scan®, Esaote) and a high-end US (Sequioa®, Siemens) imaging of the wrist before initiating either biological treatment (n=26) or intraarticular injection of Depomedrole® (n=24). Mean age was 56 years (range 21-83 years); mean disease duration 87.2 months (range 4-349 months), mean DAS 28 4,8 (range 2-7). MRI was scored according to the OMERACT RAMRIS recommendations and US Doppler colour-fractions were determined. Using Spearman's rho, we found a relatively good to moderate correlation between the US colour-fraction and the total OMERACT bone marrow oedema and synovitis scores on MRI (r=0.6; p<0.001 and r=0.4; p<0.006 respectively). There was a trend but no significant correlation with the total OMERACT erosion score (r=0.3; p=0.06). Within limits, the OMERACT RAMRIS scores of inflammation in RA patients (bone marrow oedema and synovial enhancement) are comparable to the US colour-fraction measurements using a high-end US scanner. Both imaging modalities detect inflammation although showing different aspects of the inflammatory process in the wrist joint. The higher correlation between US colour-fractions and MRI bone marrow oedema indicates a potential importance of US Doppler in monitoring inflammatory disease changes in RA.

Vascular Endothelial Growth Factor Receptor 2-Specific Microbubbles for Molecular Ultrasound Detection of Prostate Cancer in a Rat Model

To investigate whether rat prostate cancer can be detected by means of molecular ultrasound (US) using target-specific microbubbles versus a nonspecific contrast agent. A total of 20 Copenhagen rats were randomly examined 75 to 104 days after orthotopic implantation of G-Dunning rat prostatic tumor cells was using a high-end US system and either 1.2 mL/kg of the nonspecific agent A or 0.1 mL/kg of the target-specific agent B, containing vascular endothelial growth factor receptor 2 binding peptide. Contrast inflow (areas under the curve analysis) was determined during the first 30s, and all microbubbles were destroyed in the scan plane by means of the flash technique 20 minutes after intravenous administration to investigate specific accumulation of individual bubbles in tumors. Differences between normal prostate tissue and tumor were analyzed using luminance images. Sonographically determined tumor localization and extent were compared with magnetic resonance imaging and histology. The median tumor size in the 20 rats determined on US (2.3 mm) and magnetic resonance imaging (2.4 mm) showed a very high correlation (r = 0.92, P = 0.01). Both agent A and agent B demonstrated higher vascularization of tumor periphery compared with normal prostate (P < 0.05) based on contrast inflow and areas under the curve analysis. Twenty minutes after administration, luminance for agent B in the tumor was significantly higher (P = 0.003) compared with nonspecific agent A (11.8-0.1). In consensus reading, the increase in signal intensity of the tumor compared with normal prostate tissue was significantly higher for agent B (P = 0.005), whereas no significant difference was found for agent A (P = 0.180). The target-specific contrast agent was superior to the unspecific US contrast agent both with regard to early inflow analysis and specific accumulation in prostate cancer after 20 minutes.

Non-Invasive Central Venous Pressure Measurement by Compression Ultrasound—A Step Into Real Life

In a Swiss intensive care unit, 50 patients' central venous pressures (CVP) were compared using non-invasive and invasive techniques. The non-invasive technique consisted of compression ultrasound (CU) of a patient's forearm vein. The forearm was chosen for the non-invasive measurement as studies have found that when a patient is in a supine position, pressures are nearly the same in the cephalic, basilic, and brachial veins compared to the superior vena cava. The researchers investigated: 1) how feasible and accurate CVP measurements by vascular ultrasound were done by physicians with only a short training course; 2) simple ultrasound vs. a high-end duplex ultrasound system for measuring CVP; and 3) CU's ability to detect respiratory changes in CVP. Four different investigators took part in this study. The first investigator was a vascular expert with a high-end ultrasound system. The second investigator was a medical student with a high-end ultrasound system. The third investigator was a vascular expert with a portable ultrasound system, and the final investigator was an intensive care specialist with a portable ultrasound. The study was subdivided into two groups. The first one was the TeachPort study. This looked at the four investigators measuring CVP after the short training course. Four analyzers first went through three 1-h training sessions in which their technique was compared to experienced vascular ultrasonographers. Their technique was then adjusted until they obtained adequate results. Three of the four investigators then moved on to the surgical intensive care unit, where they were “blinded” for CVP, clinical diagnosis, therapy, and volume status. The fourth investigator was “blinded” only to current CVP values. The non-invasive measurement was done on the contralateral side of the subclavian catheter measuring the invasive CVP. A distal, superficial forearm vessel was examined for the CU part of the study. The second part of the study examined the influence of respiratory cycle on CVP measurement. The researchers used SPSS (SPSS Inc., Chicago, IL) to analyze the results. The study found that the ability to perform the ultrasound was comparable between the four investigators (88% and 92%). The average length of time to obtain the result was 4 min. There was a significant, linear correlation between non-invasive CVP measurements and invasive CVP measurements (r = 0.58–0.68; p < 0.001). There was no difference found between high-end ultrasounds and portable ultrasounds or between experts and trainees doing the measurements. Finally, CU was able to show differences in CVP during respiration.

Ultrasonic Imaging of Organ Perfusion with SH U 563A

Ultrasound (US) diagnosis uses B-mode images to provide anatomic information and uses Doppler analysis to measure the velocity of blood flow. It has recently been discovered that the active acoustic response of US contrast agents, acoustic emission, allows detection of some contrast agents in the microvascular compartment and even as stationary contrast with color Doppler imaging (1–3). The underlying phenomenon is the complex interaction between the incident ultrasound wave and microbubbles. The incident ultrasound can drive the microbubbles into oscillation, and depending on the size of the microbubbles and the properties of their shells, that oscillation can become resonant. As the microbubbles undergo nonlinear oscillation, they emit signals containing harmonic components of the fundamental frequency as well as broadband signal components. In principle, the microbubbles act as an active sound source within the US field (4). The signals originating from microbubbles due to stimulated acoustic emission can be used for specific detection of the US contrast agent with different techniques: conventional color Doppler imaging; and more complex pulse sequences, such as wideband harmonic imaging (5,6), in new high-end US equipment. With color Doppler imaging, the induced acoustic emissions are detected as signals with a random value, resulting in a peculiar mosaic pattern varying with time. The underlying mechanism is that color Doppler flow mapping depends on the correlation between successive pulses. This is infringed by the nonlinear response of SH U 563A (Schering, Berlin, Germany) resulting in a loss of correlation of the pulses during the destruction of the microbubble. Because this technique is not using color Doppler imaging in its original fashion, it may also be described as “loss of correlation” (LOC) imaging, to distinguish this technique from vascular color Doppler imaging. Although the same technique, color Doppler imaging, is used, the image content is changed from a flow image based on correlation to a map of the contrast distribution based on LOC and destruction of the microbubbles during the scanning process (1). The contrast agent distribution, the localization map, is generated by the presence of the random color spots, with varying color in the image and between subsequent images. The information on tissue perfusion during the vascular phase and the distribution of active reticuloendothelial system (RES) cells after uptake is provided by this map. It gives a direct image of the microvascular compartment and the RES compartment, independent of flow velocity. SH U 563A is a novel polymeric US contrast agent, optimized for this nonlinear acoustic response. Due to the durability of the polymer shell, no degradation is observed during the capillary passage in the vascular phase, allowing a complete delineation of the microvascular compartment. Therefore, SH U 563A may be considered as an ideal perfusion tracer, demonstrating, in theory, the blood volume distribution. Acad Radiol 2002; 9(suppl 1):S46–S51