Contrast-enhanced ultrasound liver imaging reporting and data system: clinical validation in a prospective multinational study in North America and Europe

BACKGROUND AND AIMS

The objective of this study is to determine the diagnostic accuracy of the American College of Radiology Contrast-Enhanced Ultrasound (CEUS) Liver Imaging Reporting and Data System LR-5 characterization for HCC diagnosis in North American or European patients.

APPROACH AND RESULTS

A prospective multinational cohort study was performed from January 2018 through November 2022 at 11 academic and nonacademic centers in North America and Europe. Patients at risk for HCC with at least 1 liver observation not previously treated, identified on ultrasound (US), or multiphase CT or MRI performed as a part of standard clinical care were eligible for the study. All participants were examined with CEUS of the liver within 4 weeks of CT/MRI or tissue diagnosis to characterize up to 2 liver nodules per participant using ACR CEUS Liver Imaging Reporting and Data System. Definite HCC diagnosis on the initial CT/MRI, imaging follow-up, or histology for CT/MRI-indeterminate nodules were used as reference standards. A total of 545 nodules had confirmed reference standards in 480 patients, 73.8% were HCC, 5.5% were other malignancies, and 20.7% were nonmalignant. The specificity of CEUS LR-5 for HCC was 95.1% (95% CI 90.1%-97.7%), sensitivity 62.9% (95% CI 57.9%-67.7%), positive predictive value 97.3% (95% CI 94.5%-98.7%), and negative predictive value 47.7% (95% CI 41.7%-53.8%). In addition, benign CEUS characterization (LR-1 or LR-2) had 100% specificity and 100% positive predictive value for nonmalignant liver nodules.

CONCLUSIONS

CEUS Liver Imaging Reporting and Data System provides an accurate categorization of liver nodules in participants at risk for HCC.

Diagnostic Performance of Quantitative Ultrasound Parameters in Non-alcoholic Fatty Liver Disease

RATIONALE AND OBJECTIVES

Marked liver steatosis, steatohepatitis, and significant fibrosis are risk factors for unfavorable outcomes in non-alcoholic fatty liver disease (NAFLD). In this study, the diagnostic performance of attenuation coefficient (AC), liver stiffness (LS), and dispersion slope (DS) was evaluated separately and combined in the diagnosis of liver steatosis and fibrosis in NAFLD suspects using biopsy or magnetic resonance imaging (MRI) as a reference standard.

MATERIALS AND METHODS

Seventy-four NAFLD suspects were prospectively imaged with an Aplio i800 ultrasound scanner (Canon Medical Systems, Tustin, CA). AC, LS, and DS measurements were obtained from the right liver lobe.

RESULTS

Thirty-four patients underwent liver biopsy, and 40 had MRI. There were 32 patients (43%) with liver steatosis and fibrosis (S + F), 22 (30%) with steatosis (S), 5 (7%) with fibrosis (F), and 15 (20%) with normal liver (N). Mean ACs were significantly higher in steatotic livers (n = 54) than in non-steatotic livers (n = 20) (P < 0.0001). LS and DS were significantly higher in patients with liver fibrosis (n = 37) compared to non-fibrotic livers (n = 37) (P = 0.0004 and P = 0.0002, respectively). In detecting (S + F), the area under the receiver operating characteristic curve (AUROCC) was 0.87 for combined ultrasound parameters of LS and AC (negative predictive value [NPV]: 75%, positive predictive value [PPV]: 77%, P < 0.0001). In detecting patients with liver steatosis and fibrosis stage ≥2, LS had an AUROCC of 0.93 (NPV: 87%, PPV: 82%, P < 0.0001). In the biopsy group, 32% (11/34) were diagnosed with non-alcoholic steatohepatitis (NASH). DS values showed a significant difference among patients with (n = 23) or without (n = 11) hepatocellular ballooning (P = 0.02). AUROCC was 0.87 for combined ultrasound parameters of AC, LS, and DS with body mass index (BMI) in detecting NASH (NPV: 80%, PPV: 87%, P = 0.0006).

CONCLUSION

AC and LS showed high diagnostic value in detecting liver steatosis and fibrosis, respectively. The combined AC and LS values further improved the diagnostic accuracy in detecting NAFLD and high-risk NAFLD patients.

Contrast-enhanced US Evaluation of Hepatocellular Carcinoma Response to Chemoembolization: A Prospective Multicenter Trial

Background Contrast-enhanced (CE) US has been studied for use in the detection of residual viable hepatocellular carcinoma (HCC) after locoregional therapy, but multicenter data are lacking. Purpose To compare two-dimensional (2D) and three-dimensional (3D) CE US diagnostic performance with that of CE MRI or CT, the current clinical standard, in the detection of residual viable HCC after transarterial chemoembolization (TACE) in a prospective multicenter trial. Materials and Methods Participants aged at least 21 years with US-visible HCC scheduled for TACE were consecutively enrolled at one of three participating academic medical centers from May 2016 to March 2022. Each underwent baseline 2D and 3D CE US before TACE, 2D and 3D CE US 1-2 weeks and/or 4-6 weeks after TACE, and CE MRI or CT 4-6 weeks after TACE. CE US and CE MRI or CT were evaluated by three fellowship-trained radiologists for the presence or absence of viable tumors and were compared with reference standards of pathology (18%), angiography on re-treatment after identification of residual disease at 1-2-month follow-up imaging (31%), 4-8-month CE MRI or CT (42%), or short-term (approximately 1-2 months) CE MRI or CT if clinically decompensated and estimated viability was greater than 50% at imaging (9%). Diagnostic performance criteria, including sensitivity and specificity, were obtained for each modality and time point with generalized estimating equation analysis. Results A total of 132 participants were included (mean age, 64 years ± 7 [SD], 87 male). Sensitivity of 2D CE US 4-6 weeks after TACE was 91% (95% CI: 84, 95), which was higher than that of CE MRI or CT (68%; 95% CI: 58, 76; P < .001). Sensitivity of 3D CE US 4-6 weeks after TACE was 89% (95% CI: 81, 94), which was higher than that of CE MRI or CT (P < .001), with no evidence of a difference from 2D CE US (P = .22). CE MRI or CT had 85% (95% CI: 76, 91) specificity, higher than that of 4-6-week 2D and 3D CE US (70% [95% CI: 56, 80] and 67% [95% CI: 53, 78], respectively; P = .046 and P = .023, respectively). No evidence of differences in any diagnostic criteria were observed between 1-2-week and 4-6-week 2D CE US (P > .21). Conclusion The 2D and 3D CE US examinations 4-6 weeks after TACE revealed higher sensitivity in the detection of residual HCC than CE MRI or CT, albeit with lower specificity. Importantly, CE US performance was independent of follow-up time. Clinical trial registration no. NCT02764801 © RSNA, 2023 Supplemental material is available for this article.

Diagnostic Performance Comparison Between Ultrasound Attenuation Measurements From Right and Left Hepatic Lobes for Steatosis Detection in Non-alcoholic Fatty Liver Disease

RATIONALE AND OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) is currently diagnosed by liver biopsy or MRI proton density fat fraction (MRI-PDFF) from left hepatic lobe (LTHL) and/or right hepatic lobe (RTHL). The objective of this study was to compare the diagnostic value of ultrasound attenuation coefficients (ACs) from RTHL and LTHL in detecting hepatic steatosis using biopsy or MRI-PDFF as a reference standard.

MATERIALS AND METHODS

Sixty-six patients with suspected NAFLD were imaged with an Aplio i800 ultrasound scanner (Canon Medical Systems, Tustin, CA). Five AC measurements from RTHL and LTHL were averaged separately and together to be compared with the reference standard.

RESULTS

Forty-seven patients (71%) were diagnosed with NAFLD. Mean ACs were significantly higher in fatty livers than non-fatty livers (RTHL: 0.73 ± 0.10 vs. 0.63 ± 0.07 dB/cm/MHZ; p < 0.0001, LTHL: 0.78 ± 0.11 vs. 0.63 ± 0.06 dB/cm/MHz; p < 0.0001, RTHL & LTHL: 0.76 ± 0.09 vs. 0.63 ± 0.05 dB/cm/MHz; p < 0.0001). Biopsy steatosis grades (n =31) were better correlated with the mean ACs of RTHL & LTHL (r = 0.72) compared to LTHL (r = 0.67) or RTHL (r = 0.61). Correlation between MRI-PDFF (n = 35) and mean ACs was better for LTHL (r = 0.69) compared to the RTHL & LTHL (r = 0.66) or RTHL (r = 0.45). Higher diagnostic accuracy was shown for the mean ACs of RTHL & LTHL (AUC 0.89, specificity 94%, sensitivity 78%) compared to LTHL (AUC 0.89, specificity 88%, sensitivity 82%) or RTHL (AUC 0.81, specificity 89%, sensitivity 68%).

CONCLUSION

Ultrasound ACs from RTHL and LTHL showed comparable diagnostic values in detection of hepatic steatosis with the highest diagnostic accuracy when they were averaged together.

Identification of sentinel lymph nodes in esophageal cancer patients using contrast-enhanced EUS with peritumoral injections

Objectives

The objective of this pilot study was to compare the performance of contrast-enhanced EUS (CE-EUS)-guided fine-needle aspiration (FNA) with EUS-FNA for lymph node (LN) staging in esophageal cancer.

Methods

Thirty-seven subjects with esophageal cancer undergoing EUS staging were enrolled, and 30 completed this institutional review board-approved study. A Prosound F75 US system (Hitachi Medical Systems, Tokyo, Japan) with harmonic contrast imaging software and GF-UCT180 curvilinear endoscope (Olympus, Tokyo, Japan) was utilized. All LNs identified by standard EUS were first noted. Sonazoid (dose: 1 mL; GE Healthcare, Oslo, Norway) was administered peritumorally, and all enhanced LNs were recorded. Fine-needle aspiration was performed on LNs considered suspicious by EUS alone, as well as LNs enhanced on CE-EUS. Performance of each modality was compared using FNA cytology as reference standard.

Results

A total of 132 LNs were detected with EUS, of which 59 showed enhancement on CE-EUS. Fifty-three LNs underwent FNA, and 22 LNs were determined to be malignant. Among the latter, 10 were considered suspicious by EUS, whereas the other 12 LNs underwent FNA only because of CE-EUS enhancement. Contrast-enhanced EUS showed enhancement in 19 of the 22 malignant LNs. The rate of metastatic node identification from EUS was 45% (10/22), and it was 86% (19/22; P = 0.008) for CE-EUS. Eight subjects (8/30 [27% of study total]) had nodal status upgraded by the addition of CE-EUS, which influenced LN staging and clinical management.

Conclusions

Fine-needle aspiration of LNs identified by CE-EUS may increase metastasis positive rate by ruling out LNs not associated with the tumor drainage pattern. In addition, CE-EUS seems to identify more metastatic LNs that would not be biopsied under the standard EUS criteria.

Comparison of Magnetic Resonance-Based Elastography and Ultrasound Shear Wave Elastography in Patients With Suspicion of Nonalcoholic Fatty Liver Disease

ABSTRACT

This study investigated the correlation between magnetic resonance elastography (MRE) and shear wave ultrasound elastography (SWE) in patients with clinically diagnosed or suspected nonalcoholic fatty liver disease (NAFLD). Subjects with or at risk of NAFLD identified by magnetic resonance imaging (MRI) proton density fat fraction (PDFF) were prospectively enrolled. For each patient, 6 valid 2-dimensional SWE measurements were acquired using a Logiq E10 scanner (GE HealthCare, Waukesha, WI). A reliability criterion of an interquartile range to median ratio of ≤15% was used for SWE to indicate quality dataset. Magnetic resonance elastography, and MR-fat quantification data were collected the same day as part of the patient's clinical standard of care. Magnetic resonance imaging PDFF was used as a reference to quantify fat with >6.4% indicating NAFLD. Pearson correlation and t-test were performed for statistical analyses. A total of 140 patients were enrolled, 112 of which met SWE reliability measurement criteria. Magnetic resonance elastography and 2-dimensional SWE showed a positive correlation across all study subjects ( r = 0.27; P = 0.004). When patients were grouped according to steatosis and fibrosis state, a positive correlation was observed between MRE and SWE in patients with fibrosis ( r = 0.30; P = 0.03), without fibrosis ( r = 0.27; P = 0.03), and with NAFLD ( r = 0.28; P = 0.02). No elastography technique correlated with liver fat quantification ( P > 0.52). Magnetic resonance elastography was significantly different between patients with and without fibrosis ( P < 0.0001). However, this difference was not apparent with SWE ( P = 0.09). In patients with suspected or known NAFLD, MRE, and SWE demonstrated a positive correlation. In addition, these noninvasive imaging modalities may be useful adjunct techniques for monitoring NAFLD.

Improved Tumor Control Following Radiosensitization with Ultrasound-Sensitive Oxygen Microbubbles and Tumor Mitochondrial Respiration Inhibitors in a Preclinical Model of Head and Neck Cancer

Tumor hypoxia (oxygen deficiency) is a major contributor to radiotherapy resistance. Ultrasound-sensitive microbubbles containing oxygen have been explored as a mechanism for overcoming tumor hypoxia locally prior to radiotherapy. Previously, our group demonstrated the ability to encapsulate and deliver a pharmacological inhibitor of tumor mitochondrial respiration (lonidamine (LND)), which resulted in ultrasound-sensitive microbubbles loaded with O₂ and LND providing prolonged oxygenation relative to oxygenated microbubbles alone. This follow-up study aimed to evaluate the therapeutic response to radiation following the administration of oxygen microbubbles combined with tumor mitochondrial respiration inhibitors in a head and neck squamous cell carcinoma (HNSCC) tumor model. The influences of different radiation dose rates and treatment combinations were also explored. The results demonstrated that the co-delivery of O₂ and LND successfully sensitized HNSCC tumors to radiation, and this was also enhanced with oral metformin, significantly slowing tumor growth relative to unsensitized controls (p < 0.01). Microbubble sensitization was also shown to improve overall animal survival. Importantly, effects were found to be radiation dose-rate-dependent, reflecting the transient nature of tumor oxygenation.

Longitudinal ultrasound imaging and network modeling in rats reveal sex-dependent suppression of liver regeneration after resection in alcoholic liver disease

Liver resection is an important surgical technique in the treatment of cancers and transplantation. We used ultrasound imaging to study the dynamics of liver regeneration following two-thirds partial hepatectomy (PHx) in male and female rats fed via Lieber-deCarli liquid diet protocol of ethanol or isocaloric control or chow for 5–7 weeks. Ethanol-fed male rats did not recover liver volume to the pre-surgery levels over the course of 2 weeks after surgery. By contrast, ethanol-fed female rats as well as controls of both sexes showed normal volume recovery. Contrary to expectations, transient increases in both portal and hepatic artery blood flow rates were seen in most animals, with ethanol-fed males showing higher peak portal flow than any other experimental group. A computational model of liver regeneration was used to evaluate the contribution of physiological stimuli and estimate the animal-specific parameter intervals. The results implicate lower metabolic load, over a wide range of cell death sensitivity, in matching the model simulations to experimental data of ethanol-fed male rats. However, in the ethanol-fed female rats and controls of both sexes, metabolic load was higher and in combination with cell death sensitivity matched the observed volume recovery dynamics. We conclude that adaptation to chronic ethanol intake has a sex-dependent impact on liver volume recovery following liver resection, likely mediated by differences in the physiological stimuli or cell death responses that govern the regeneration process. Immunohistochemical analysis of pre- and post-resection liver tissue validated the results of computational modeling by associating lack of sensitivity to cell death with lower rates of cell death in ethanol-fed male rats. Our results illustrate the potential for non-invasive ultrasound imaging to assess liver volume recovery towards supporting development of clinically relevant computational models of liver regeneration.

Ultrasound-Based Machine Learning Approach for Detection of Nonalcoholic Fatty Liver Disease

OBJECTIVES

Current diagnosis of nonalcoholic fatty liver disease (NAFLD) relies on biopsy or MR-based fat quantification. This prospective study explored the use of ultrasound with artificial intelligence for the detection of NAFLD.

METHODS

One hundred and twenty subjects with clinical suspicion of NAFLD and 10 healthy volunteers consented to participate in this institutional review board-approved study. Subjects were categorized as NAFLD and non-NAFLD according to MR proton density fat fraction (PDFF) findings. Ultrasound images from 10 different locations in the right and left hepatic lobes were collected following a standard protocol. MRI-based liver fat quantification was used as the reference standard with >6.4% indicative of NAFLD. A supervised machine learning model was developed for assessment of NAFLD. To validate model performance, a balanced testing dataset of 24 subjects was used. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy with 95% confidence interval were calculated.

RESULTS

A total of 1119 images from 106 participants was used for model development. The internal evaluation achieved an average precision of 0.941, recall of 88.2%, and precision of 89.0%. In the testing set AutoML achieved a sensitivity of 72.2% (63.1%-80.1%), specificity of 94.6% (88.7%-98.0%), positive predictive value (PPV) of 93.1% (86.0%-96.7%), negative predictive value of 77.3% (71.6%-82.1%), and accuracy of 83.4% (77.9%-88.0%). The average agreement for an individual subject was 92%.

CONCLUSIONS

An ultrasound-based machine learning model for identification of NAFLD showed high specificity and PPV in this prospective trial. This approach may in the future be used as an inexpensive and noninvasive screening tool for identifying NAFLD in high-risk patients.

Improving diagnostic accuracy of ultrasound texture features in detecting and quantifying hepatic steatosis using various beamforming sound speeds

Objective.While ultrasound image texture has been utilized to detect and quantify hepatic steatosis, the texture features extracted using a single (conventionally 1540 m s-1) beamforming speed of sound (SoS) failed to achieve reliable diagnostic performance. This study aimed to investigate if the texture features extracted using various beamforming SoSs can improve the accuracy of hepatic steatosis detection and quantification.Approach.Patients with suspected non-alcoholic fatty liver disease underwent liver biopsy or MRI proton density fat fraction (PDFF) as part of standard of care, were prospectively enrolled. The radio-frequency data from subjects' right and left liver lobes were collected using 6 beamforming SoSs: 1300, 1350, 1400, 1450, 1500 and 1540 m s-1and analyzed offline. The texture features, i.e. Contrast, Correlation, Energy and Homogeneity from gray-level co-occurrence matrix of normalized envelope were obtained from a region of interest in the liver parenchyma.Main results.Forty-three subjects (67.2%) were diagnosed with steatosis while 21 had no steatosis. Homogeneity showed the area under the curve (AUC) of 0.75-0.82 and 0.58-0.81 for left and right lobes, respectively with varying beamforming SoSs. The combined Homogeneity value over 1300-1540 m s-1from left and right lobes showed the AUC of 0.90 and 0.81, respectively. Furthermore, the combined Homogeneity values from left and right lobes over 1300-1540 m s-1improved the AUC to 0.94. The correlation between texture features and steatosis severity was improved by using the images from various beamforming SoSs. The combined Contrast values over 1300-1540 m s-1from left and right lobes demonstrated the highest correlation (r= 0.90) with the MRI PDFF while the combined Homogeneity values over 1300-1540 m s-1from left and right lobes showed the highest correlation with the biopsy grades (r= -0.81).Significance.The diagnostic accuracy of ultrasound texture features in detecting and quantifying hepatic steatosis was improved by combining its values extracted using various beamforming SoSs.

Ultrasound quantitative assessment of ventral finger microvasculopathy in systemic sclerosis with Raynaud's phenomena: a comparative study

OBJECTIVE

To assess the finger vascularity of systemic sclerosis patients with Raynaud's phenomenon (RP-SSc) using various ultrasound techniques.

METHODS

All fingers (except thumbs) of 18 RP-SSc patients and 18 controls were imaged at room temperature using four ultrasound vascular imaging techniques. The percent vascular area was quantified by counting blood flow pixels in a 25 mm² square centred at the nail fold for the dorsal side and in 25 mm² and 100 mm² square from the fingertip for the ventral side. The mean vascular intensity was calculated from the corresponding areas for dorsal and ventral sides.

RESULTS

The percent vascular areas and mean vascular intensities in RP-SSc were significantly lower than those in controls for both dorsal and ventral sides (p<0.01). The mean vascular intensities showed slightly higher area under the curve (AUC) than the percent vascular areas (0.53-0.91 vs 0.53-0.90) regardless of imaging technique and assessment side. For each imaging technique, the ventral side vascularity showed a higher AUC (0.74-0.91) compared with the dorsal side (0.53-0.81). Moreover, ventral side abnormalities were associated with a history of digital ulcers.

CONCLUSIONS

Ultrasound demonstrated potential to quantify finger vascularity of RP-SSc. The ventral side of the fingers showed a higher accuracy in detecting RP-SSc than the dorsal side.

A Comprehensive Motion Compensation Method for In-Plane and Out-of-Plane Motion in Dynamic Contrast-Enhanced Ultrasound of Focal Liver Lesions

Contrast-enhanced ultrasound (CEUS) acquisitions of focal liver lesions are affected by motion, which has an impact on contrast signal quantification. We therefore developed and tested, in a large patient cohort, a motion compensation algorithm called the Iterative Local Search Algorithm (ILSA), which can correct for both periodic and non-periodic in-plane motion and can reject frames with out-of-plane motion. CEUS cines of 183 focal liver lesions in 155 patients from three hospitals were used to develop and test ILSA. Performance was evaluated through quantitative metrics, including the root mean square error and R2 in fitting time-intensity curves and standard deviation value of B-mode intensities, computed across cine frames), and qualitative evaluation, including B-mode mean intensity projection images and parametric perfusion imaging. The median root mean square error significantly decreased from 0.032 to 0.024 (p < 0.001). Median R2 significantly increased from 0.88 to 0.93 (p < 0.001). The median standard deviation value of B-mode intensities significantly decreased from 6.2 to 5.0 (p < 0.001). B-Mode mean intensity projection images revealed improved spatial resolution. Parametric perfusion imaging also exhibited improved spatial detail and better differentiation between lesion and background liver parenchyma. ILSA can compensate for all types of motion encountered during liver CEUS, potentially improving contrast signal quantification of focal liver lesions.

Volumetric Quantitative Contrast-enhanced Ultrasonography Evaluation of Complex Renal Cysts: An Adjunctive Metric to the Bosniak Classification System to Predict Malignancy

BACKGROUND

Management of complex renal cysts is guided by the Bosniak classification system, which may be inadequate for risk stratification of patients for intervention. Fractional tumor vascularity (FV) calculated from volumetric contrast-enhanced ultrasound (CEUS) images may provide additional useful information.

OBJECTIVE

To evaluate CEUS and FV calculation for risk stratification of patients with complex renal cysts.

DESIGN, SETTING, AND PARTICIPANTS

This was a pilot prospective study with institutional review board approval involving patients undergoing surgery for Bosniak IIF-IV complex renal cysts. CEUS was performed preoperatively on the day of surgery with two-dimensional (2D) and three-dimensional (3D) imaging and sulfur hexafluoride lipid-type A microspheres as the ultrasound contrast agent.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

A custom MATLAB program was used to select regions of interest on CEUS scans. FV was calculated according to FV = 1 - (total nonenhancing area/total lesion area). We assessed the ability of 2D- and 3D-derived percentage FV (2DFV%, and 3DFV%) and Bosniak classification schemes (pre-2019 [P2019B] and post-2019 [B2019]) to predict malignancy, aggressive histology, and upstaging on surgical pathology. Performance was assessed as area under the receiver operating characteristic curve (AUC).

RESULTS AND LIMITATIONS

Twenty eligible patients were included in final analysis, of whom 85% (n = 17) had Bosniak IV cysts and 85% (n = 17) had malignant disease on final pathology. Four (24%) of the malignant lesions were International Society of Urological Pathology grade 3-4. The AUC for predicting malignancy was 0.980, 0.824, 0.863, and 0.824 with P2019B, B2019, 2DFV%, and 3DFV%, respectively. When the Bosniak classification was combined with FV%, three models had an AUC of 1, while the combined 2DFV% + B2019 model had AUC of 0.980.

CONCLUSIONS

FV is a novel metric for evaluating complex cystic renal masses and enhances the ability of the Bosniak classification system to predict malignancy. This metric may serve as an adjunct in risk stratification for surgical intervention. Further prospective evaluation is warranted.

PATIENT SUMMARY

Cysts in the kidney are currently classified using a scheme called the Bosniak system. We assessed measurement of the percentage of vascular tissue (called fractional vascularity) in cysts on a special type of ultrasound scan. This promising test adds information when combined with the Bosniak system and can help in guiding appropriate treatment.

Ultrasound Pressure Estimation for Diagnosing Portal Hypertension in Patients Undergoing Dialysis for Chronic Kidney Disease

OBJECTIVES

Hepatic venous pressure gradient (HVPG) is considered the standard in quantifying portal hypertension, but can be unreliable in dialysis patients. A noninvasive ultrasound technique, subharmonic-aided pressure estimation (SHAPE), may be a valuable surrogate of these pressure estimates. This study compared SHAPE and HVPG with pathology findings for fibrosis in dialysis patients.

METHODS

This was a subgroup study from an IRB-approved trial that included 20 patients on dialysis undergoing SHAPE examinations of portal and hepatic veins using a modified Logiq 9 scanner (GE, Waukesha, WI), during infusion of Sonazoid (GE Healthcare, Oslo, Norway). SHAPE was compared to HVPG and pathology findings using the Ludwig-Batts scoring system for fibrosis. Logistic regression, ROC analysis, and t-tests were used to compare HVPG and SHAPE with pathological findings of fibrosis.

RESULTS

Of 20 cases, 5 had HVPG values corresponding to subclinical and clinical portal hypertension (≥6 and ≥10 mmHg, respectively) while 15 had normal HVPG values (≤5 mmHg). SHAPE and HVPG correlated moderately (r = 0.45; P = .047). SHAPE showed a trend toward correlating with fibrosis (r = 0.42; P = .068), while HVPG did not (r = 0.18; P = .45). SHAPE could differentiate between mild (stage 0-1) and moderate to severe (stage 2-4) fibrosis (-10.4 ± 4.9 dB versus -5.4 ± 3.2 dB; P = .035), HVPG could not (3.0 ± 0.6 mmHg versus 4.8 ± 0.7 mmHg; P = .30). ROC curves showed a diagnostic accuracy for SHAPE of 80%, while HVPG reached 76%.

CONCLUSION

Liver fibrosis staging in dialysis patients evaluated for portal hypertension appears to be more accurately predicted by SHAPE than by HVPG; albeit in a small sample size.

Activation of Phase Change Contrast Agents Using Ionizing Radiation

The feasibility of activating phase change contrast agents (PCCA) made from Definity (Lantheus Medical Imaging) using X-rays was investigated. A 10 mL of Definity PCCA (0.1 mL PCCA/mL) were injected into gelatin phantoms and irradiated using doses of 0, 30, 50, and 100 Gy. Size distribution and PCCA activation were measured after irradiation. Definity PCCAs were activated at a threshold of 50 Gy. Changes were visible with microscopy, visual inspection of T-flasks, and ultrasound imaging of gelatin phantoms. Moreover, increasing the radiation dose above 50 Gy appeared to further activate PCCA. These results indicate Definity PCCAs may be useful for ultrasound-based radiation dosimetry.

Improved Sensitivity of Ultrasound-Based Subharmonic Aided Pressure Estimation Using Monodisperse Microbubbles

OBJECTIVES

Subharmonic aided pressure estimation (SHAPE) has been shown effective for noninvasively measuring hydrostatic fluid pressures in a variety of clinical applications. The objective of this study was to explore potential improvements in SHAPE sensitivity using monodisperse microbubbles.

METHODS

Populations of monodisperse microbubbles were created using a commercially available microfluidics device (Solstice Pharmaceuticals). Size distributions were assessed using a Coulter Counter and stability of the distribution following fabrication was evaluated over 24 hours. Attenuation of the microbubble populations from 1 to 10 MHz was then quantified using single element transducers to identify each formulation's resonance frequency. Frequency spectra over increasing driving amplitudes were investigated to determine the nonlinear phases of subharmonic signal generation. SHAPE sensitivity was evaluated in a hydrostatic pressure-controlled water bath using a Logiq E10 scanner (GE Healthcare).

RESULTS

Monodisperse lipid microbubble suspensions ranging from 2.4 to 5.3 μm in diameter were successfully created and they showed no discernable change in size distribution over 24 hours following activation. Calculated resonance frequencies ranged from 2.1 to 6.3 MHz and showed excellent correlation with microbubble diameter (R²  > 0.99). When investigating microbubble frequency response, subharmonic signal occurrence was shown to begin at 150 kPa peak negative pressure, grow up to 225 kPa, and saturate at approximately 250 kPa. Using the Logiq E10, monodisperse bubbles demonstrated a SHAPE sensitivity of -0.17 dB/mmHg, which was nearly twice the sensitivity of the commercial polydisperse microbubble currently being used in clinical trials.

CONCLUSIONS

Monodisperse microbubbles have the potential to greatly improve the sensitivity of SHAPE for the noninvasive measurement of hydrostatic pressures.

Development of a Dual Drug-Loaded, Surfactant-Stabilized Contrast Agent Containing Oxygen

Co-delivery of cancer therapeutics improves efficacy and encourages synergy, but delivery faces challenges, including multidrug resistance and spatiotemporal distribution of therapeutics. To address these, we added paclitaxel to previously developed acoustically labile, oxygen-core, surfactant-stabilized microbubbles encapsulating lonidamine, with the aim of developing an agent containing both a therapeutic gas and two drugs acting in combination. Upon comparison of unloaded, single-loaded, and dual-loaded microbubbles, size (~1.7 µm) and yield (~2 × 10⁹ microbubbles/mL) (~1.7) were not statistically different, nor were acoustic properties (maximum in vitro enhancements roughly 18 dB, in vitro enhancements roughly 18 dB). Both drugs encapsulated above required doses calculated for head and neck squamous cell carcinoma, the cancer of choice. Interestingly, paclitaxel encapsulation efficiency increased from 1.66% to 3.48% when lonidamine was included. During preparation, the combination of single drug-loaded micelles gave higher encapsulation (µg drug/g microbubbles) than micelles loaded with either drug alone (lonidamine, 104.85 ± 22.87 vs. 87.54 ± 16.41), paclitaxel (187.35 ± 8.38 vs. 136.51 ± 30.66). In vivo intravenous microbubbles produced prompt ultrasound enhancement within tumors lasting 3–5 min, indicating penetration into tumor vasculature. The ability to locally destroy the microbubble within the tumor vasculature was confirmed using a series of higher intensity ultrasound pulses. This ability to locally destroy microbubbles shows therapeutic promise that warrants further investigation.

Contrast-Enhanced Ultrasound in Small Intestinal Ischemia: Proof of Concept

BACKGROUND

Small intestinal ischemia is a challenging diagnosis to make, even with the combination of imaging, laboratory analysis, and physical exam. This pilot study investigated the role of CEUS in evaluating small bowel wall vascularity in participants with suspected ischemia.

METHODS

In this IRB-approved pilot study, CEUS using perflutren lipid microspheres (DEFINITY®; Lantheus Medical Imaging Inc., N. Billerica, MA) was performed on participants determined by the clinical surgical team to have concerns for small intestinal ischemia. CEUS interpretations were performed at both the bedside and later by a blinded radiologist and compared to clinical imaging, surgical findings, or long-term clinical outcomes.

RESULTS

Fifteen CEUS examinations were performed on 14 participants. Five of the participants underwent exploratory laparotomy. Of these, one had small intestinal ischemia (without necrosis). Point of care CEUS demonstrated no evidence of bowel necrosis in any case, and delayed enhancement (indicative of intestinal ischemia) in three cases, resulting in a sensitivity of 100% (95% CI 2.5-100%) and specificity of 85.7% (95% CI 57.2-98.2%). CEUS correctly ruled out ischemia in 91.7% of cases with CT suspicion of small bowel obstruction and 60% of cases that underwent surgical intervention. Additionally, the rate of agreement between bedside interpretation and later radiologist read was high (93%).

CONCLUSIONS

CEUS is uniquely positioned for evaluating the small intestine, because of its high temporal resolution and immediacy of results. Combined with multi-sectional imaging for focal areas of ischemia and/or clinical suspicion for pan ischemia, CEUS may be a useful rule out test for small intestinal ischemia.

Evaluation of Suspected Small Bowel Ischemia Using Contrast-Enhanced Ultrasound with Computed Tomography Fusion

Small bowel ischemia can lead to fatal complications such as necrosis, perforation, and sepsis. Clinical examinations and laboratory tests are usually inconclusive in critically ill patients. The need for surgical exploration is decided based on imaging, examination, and clinical judgment. The decision to operate is time-critical and can be lifesaving, but surgical intervention has the potential to cause additional morbidity, especially in unstable patients. Contrast-enhanced computed tomography (CECT) is the study of choice in suspected small bowel ischemia but has poor specificity. Contrast-enhanced ultrasound (CEUS) provides real-time visualization of the bowel wall vascularity. In this case report, we used a CEUS with CT fusion examination to rule out small bowel ischemia in a critically ill patient with suspected closed loop small bowel obstruction on CECT and in whom surgical exploration would have not been well tolerated. The patient's condition later improved, and an abdominal CT showed no evidence of obstruction.

A Noninvasive Ultrasound Based Technique to Identify Treatment Responders in Patients with Portal Hypertension

RATIONALE AND OBJECTIVE

Subharmonic aided pressure estimation (SHAPE) is based on the inverse relationship between the subharmonic amplitude of ultrasound contrast microbubbles and ambient pressure. The aim of this study was to verify if SHAPE can accurately monitor disease progression in patients identified with portal hypertension.

MATERIALS & METHODS

A modified Logiq 9 scanner with a 4C curvi-linear probe (GE, Waukesha, WI) was used to acquire SHAPE data (transmitting and receiving at 2.5 and 1.25 MHz, respectively) using Sonazoid (GE Healthcare, Oslo, Norway; FDA IND 124,465). Twenty-one (median age 59 years; 12 Males) of the 178 patients enrolled in this institutional review board approved study (14F.113) were identified as having clinically significant portal hypertension based on their hepatic venous pressure gradient results ≥ 10 mmHg. Repeat SHAPE examinations were done every 6.2 months. Liver function tests and clinical indicators were used to establish treatment response.

RESULTS

Of the 21 portal hypertensive subjects, 11 had successful follow up scans with an average follow up time of 6.2 months. There was a significantly larger SHAPE signal reduction in the group who were classified as treatment responders (n = 10; -4.01±3.61 dB) compared to the single nonresponder (2.33 dB; p < 0.001). Results for responders matched the corresponding clinical outcomes of improved model for end stage liver disease (MELD) scores, improvement in underlying cause of portal hypertension, improved liver function tests and reduced ascites.

CONCLUSION

SHAPE can potentially monitor disease progression in portal hypertensive patients and hence, may help clinicians in patient management. A larger study would further validate this claim.

Predicting Long-Term Hepatocellular Carcinoma Response to Transarterial Radioembolization Using Contrast-Enhanced Ultrasound: Initial Experiences

Conventional cross-sectional imaging done shortly after radioembolization of hepatocellular carcinoma (HCC) does not reliably predict long-term response to treatment. This study evaluated whether quantitative contrast-enhanced ultrasound (CEUS) can predict the long-term response of HCC to yttrium-90 (Y-90) treatment. Fifteen patients underwent CEUS at three time points: immediately following treatment and 1 and 2 wk post-treatment. Response 3-6 mo after treatment was categorized on contrast-enhanced magnetic resonance imaging by two experienced radiologists using the Modified Response Evaluation Criteria in Solid Tumors. CEUS data were analyzed by quantifying tumor perfusion and residual fractional vascularity using time-intensity curves. Patients with stable disease on magnetic resonance imaging had significantly greater fractional vascularity 2 wk post-treatment (65.15%) than those with partial or complete response (13.8 ± 9.9%, p = 0.007, and 14.9 ± 15.4%, p = 0.009, respectively). Complete responders had lower tumor vascularity at 2 wk than at post-operative examination (-38.3 ± 15.4%, p = 0.045). Thus, this pilot study suggests CEUS may provide an earlier indication of Y-90 treatment response than cross-sectional imaging.

Selecting the optimal parameters for sonoporation of pancreatic cancer in a pre-clinical model

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in the modern world, in part due to poor delivery of chemotherapeutics. Sonoporation can be used to enhance the efficacy of standard of care therapies for PDAC. Using xenograft models of PDAC we investigate sonoporation using four ifferent ultrasound contrast agents (UCAs) and two ultrasound regimens to identify the ideal parameters to increase therapeutic efficacy. MIA-PaCa2 xenografts in over 175 immunodeficient mice were treated with gemcitabine and paclitaxel and subjected to low or high power ultrasound (60 and 200 mW/cm² respectively) in conjunction with one of four different UCAs. The UCAs investigated were Definity®, SonoVue®, Optison™ or Sonazoid™. Tumor volumes, vascularity, hemoglobin, and oxygenation were measured and compared to controls. High power treatment in conjunction with Sonazoid sonoporation led to significantly smaller tumors when started early (tumors ~50mm³; p = .0105), while no UCAs significantly increased efficacy in the low power cohort. This trend was also found in larger tumors (~250mm³) where all four UCA agents significantly increased therapeutic efficacy in the high power group (p < .01), while only Definity and SonoVue increased efficacy in the low power cohort (p < .03). Overall, the higher power ultrasound treatment modality was more consistently effective at decreasing tumor volume and increasing vascularity characteristics. In conclusion, Sonazoid was the most consistently effective UCA at decreasing tumor volume and increasing vascularity. Thus, we are pursuing a larger phase II clinical trial to validate the increased efficacy of sonoporation in conjunction with chemotherapy in PDAC patients.

US-triggered Microbubble Destruction for Augmenting Hepatocellular Carcinoma Response to Transarterial Radioembolization: A Randomized Pilot Clinical Trial

Background US contrast agents are gas-filled microbubbles (MBs) that can be locally destroyed by using external US. Among other bioeffects, US-triggered MB destruction, also known as UTMD, has been shown to sensitize solid tumors to radiation in preclinical models through localized insult to the vascular endothelial cells. Purpose To evaluate the safety and preliminary efficacy of combining US-triggered MB destruction and transarterial radioembolization (TARE) in participants with hepatocellular carcinoma (HCC). Materials and Methods In this pilot clinical trial, participants with HCC scheduled for sublobar TARE were randomized to undergo either TARE or TARE with US-triggered MB destruction 1-4 hours and approximately 1 and 2 weeks after TARE. Enrollment took place between July 2017 and February 2020. Safety of US-triggered MB destruction was evaluated by physiologic monitoring, changes in liver function tests, adverse events, and radiopharmaceutical distribution. Treatment efficacy was evaluated by using modified Response Evaluation Criteria in Solid Tumors (mRECIST) on cross-sectional images, time to required next treatment, transplant rates, and overall survival. Differences across mRECIST reads were compared by using a Mann-Whitney U test, and the difference in prevalence of tumor response was evaluated by Fisher exact test, whereas differences in time to required next treatment and overall survival curves were compared by using a log-rank (Mantel-Cox) test. Results Safety results from 28 participants (mean age, 70 years ± 10 [standard deviation]; 17 men) demonstrated no significant changes in temperature (P = .31), heart rate (P = .92), diastolic pressure (P = .31), or systolic pressure (P = .06) before and after US-triggered MB destruction. No changes in liver function tests between treatment arms were observed 1 month after TARE (P > .15). Preliminary efficacy results showed a greater prevalence of tumor response (14 of 15 [93%; 95% CI: 68, 100] vs five of 10 [50%; 95% CI: 19, 81]; P = .02) in participants who underwent both US-triggered MB destruction and TARE (P = .02). Conclusion The combination of US-triggered microbubble destruction and transarterial radioembolization is feasible with an excellent safety profile in this patient population and appears to result in improved hepatocellular carcinoma treatment response. © RSNA, 2020.

Diagnosing Portal Hypertension with Noninvasive Subharmonic Pressure Estimates from a US Contrast Agent

Background The current standard for assessing the severity of portal hypertension is the invasive acquisition of hepatic venous pressure gradient (HVPG). A noninvasive US-based technique called subharmonic-aided pressure estimation (SHAPE) could reduce risk and enable routine acquisition of these pressure estimates. Purpose To compare quantitative SHAPE to HVPG measurements to diagnose portal hypertension in participants undergoing a transjugular liver biopsy. Materials and Methods This was a prospective cross-sectional trial conducted at two hospitals between April 2015 and March 2019 (ClinicalTrials.gov identifier, NCT02489045). This trial enrolled participants who were scheduled for transjugular liver biopsy. After standard-of-care transjugular liver biopsy and HVPG pressure measurements, participants received an infusion of a US contrast agent and saline. During infusion, SHAPE data were collected from a portal vein and a hepatic vein, and the difference was compared with HVPG measurements. Correlations between data sets were determined by using the Pearson correlation coefficient, and statistical significance between groups was determined by using the Student t test. Receiver operating characteristic analysis was performed to determine the sensitivity and specificity of SHAPE. Results A total of 125 participants (mean age ± standard deviation, 59 years ± 12; 80 men) with complete data were included. Participants at increased risk for variceal hemorrhage (HVPG ≥12 mm Hg) had a higher mean SHAPE gradient compared with participants with lower HVPGs (0.79 dB ± 2.53 vs -4.95 dB ± 3.44; P < .001), which is equivalent to a sensitivity of 90% (13 of 14; 95% CI: 88, 94) and a specificity of 80% (79 of 99; 95% CI: 76, 84). The SHAPE gradient between the portal and hepatic veins was in good overall agreement with the HVPG measurements (r = 0.68). Conclusion Subharmonic-aided pressure estimation is an accurate noninvasive technique for detecting clinically significant portal hypertension. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kiessling in this issue.

Superb Microvascular Imaging Improves Detection of Vascularity in Indeterminate Renal Masses

OBJECTIVES

Vascular assessment of indeterminate renal masses (iRMs) remains a crucial element of diagnostic imaging, as the presence of blood flow within renal lesions suggests malignancy. We compared the utility of Superb Microvascular Imaging (SMI; Canon Medical Systems, Tustin, CA), a novel Doppler technique, to standard color Doppler imaging (CDI) and power Doppler imaging (PDI) for the detection of vascularity within iRMs.

METHODS

Patients undergoing contrast-enhanced ultrasound (CEUS) evaluations for iRMs first underwent a renal ultrasound examination with the following modes: CDI, PDI, color Superb Microvascular Imaging (cSMI), and monochrome Superb Microvascular Imaging (mSMI), using an Aplio i800 scanner with an i8CX1 transducer (Canon Medical Systems). After image randomization, each mode was assessed for iRM vascularity by 4 blinded readers on a diagnostic confidence scale of 1 to 5 (5 = most confident). The results were compared to CEUS as the reference standard.

RESULTS

Forty-one patients with 50 lesions met inclusion criteria. Relative to the other 3 modalities, mSMI had the highest sensitivity (63.3%), whereas cSMI had the highest specificity (62.1%). Both cSMI and mSMI also had the highest diagnostic accuracy (0.678 and 0.680, respectively; both P < 0.001) compared to CDI (0.568) and PDI (0.555). Although the reader-reported confidence interval of mSMI (mean ± SD, 3.6 ± 1.1) was significantly lower than CDI (4.1 ± 1.0) and PDI (4.0 ± 1.0; P < 0.001), the confidence level of cSMI (4.1 ± 0.9) was not (P > 0.173).

CONCLUSIONS

Preliminary data suggest that SMI is a potentially useful modality in detecting microvasculature in iRMs compared to standard Doppler techniques. Future studies should aim to compare the efficacy of both SMI and CEUS and to assess the ability of SMI to characterize malignancy in iRMs.

A Sonographer’s Step-by-Step Approach for Preventing Transmission of COVID-19

The 2019 novel coronavirus, known as COVID-19, has greatly affected the way sonographers care for their patients. Sonography can be a useful imaging tool for surveillance and diagnosis of various conditions associated with COVID-19 patients or patients under investigation (PUIs). Currently, there are limited resources and protocols for preventing the transmission of COVID-19 from ultrasound equipment. Our institution has created a detailed protocol for scanning COVID-19 patients or PUIs to address this important issue.

Characterization of Adnexal Masses Using Contrast-Enhanced Subharmonic Imaging: A Pilot Study

OBJECTIVES

This pilot study evaluated whether contrast-enhanced subharmonic imaging (SHI) could be used to characterize adnexal masses before surgical intervention.

METHODS

Ten women (with 12 lesions) scheduled for surgery of an ovarian mass underwent an SHI examination of their adnexal region using a modified LOGIQ E9 scanner (GE Healthcare, Waukesha, WI) with an endocavitary transducer, in which digital clips were acquired by pulse destruction-replenishment SHI across the lesions. Time-intensity curves were created offline to quantitatively evaluate SHI parameters (fractional tumor perfusion, peak contrast intensity, time to peak contrast enhancement, and area under the time-intensity curve), which were compared to pathologic characterizations of the lesions.

RESULTS

Of the 12 masses, 8 were benign, and 4 were malignant. A qualitative analysis of the SHI images by an experienced radiologist resulted in diagnostic accuracy of 70%, compared to 56% without contrast, whereas an inexperienced radiologist improved from 50% to 58% accuracy, demonstrating the benefit of SHI. A quantitative analysis of SHI parameters produced diagnostic accuracy as high as 81%. Peak contrast intensity was significantly greater in malignant than benign masses (mean ± SD, 0.109 ± 0.088 versus 0.046 ± 0.030 arbitrary units; P = .046). Malignant masses also showed significantly greater perfusion than benign masses (24.79% ± 25.34% versus 7.62% ± 6.50%; P = .045). When the radiologist reads were combined with the most predictive quantitative SHI parameter (percent perfusion), diagnostic accuracy improved to 84% for the experienced radiologist and 96% for the novice radiologist.

CONCLUSIONS

Results indicate that SHI for presurgical characterization of adnexal masses may improve the determination of malignancy and diagnostic accuracy, albeit based on a small sample size.

Breast Cancer Brain Metastasis Response to Radiation After Microbubble Oxygen Delivery in a Murine Model

OBJECTIVES

Hypoxic cancer cells have been shown to be more resistant to radiation therapy than normoxic cells. Hence, this study investigated whether ultrasound (US)-induced rupture of oxygen-carrying microbubbles (MBs) would enhance the response of breast cancer metastases to radiation.

METHODS

Nude mice (n = 15) received stereotactic injections of brain-seeking MDA-MB-231 breast cancer cells into the right hemisphere. Animals were randomly assigned into 1 of 5 treatment groups: no intervention, 10 Gy radiation using a small-animal radiation research platform, nitrogen-carrying MBs combined with US-mediated MB rupture immediately before 10 Gy radiation, oxygen-carrying MBs immediately before 10 Gy radiation, and oxygen-carrying MBs with US-mediated MB rupture immediately before 10 Gy radiation. Tumor progression was monitored with 3-dimensional US, and overall survival was noted.

RESULTS

All groups except those treated with oxygen-carrying MB rupture and radiation had continued rapid tumor growth after treatment. Tumors treated with radiation alone showed a mean increase in volume ± SD of 337% ± 214% during the week after treatment. Tumors treated with oxygen-carrying MBs and radiation without MB rupture showed an increase in volume of 383% ± 226%. Tumors treated with radiation immediately after rupture of oxygen-carrying MBs showed an increase in volume of only 41% ± 1% (P = 0.045), and this group also showed a 1 week increase in survival time.

CONCLUSIONS

Adding US-ruptured oxygen-carrying MBs to radiation therapy appears to delay tumor progression and improve survival in a murine model of metastatic breast cancer.

Multiscale quantification of tumor microarchitecture for predicting therapy response using dynamic contrast-enhanced ultrasound imaging

Hepatocellular carcinoma (HCC) is the most common liver cancer with 1 million cases globally. A current clinical challenge is to determine which patients will respond to transarterial chemoembolization (TACE) as effective delivery of the embolic material may be influenced by the tumor vascular supply. The purpose of this study is to develop a novel image processing algorithm for improved quantification of tumor microvascular morphology features using contrast-enhanced ultrasound (CEUS) images and to predict the TACE response based on these biomarkers before treatment. A temporal sequence of CEUS images was corrected from rigid and non-rigid motion artifacts using affine and free form deformation models. Subsequently, a principal component analysis based singular value filter was applied to remove the clutter signal from each frame. A maximum intensity projection was created from high-resolution images. A multiscale vessel enhancement filter was first utilized to enhance the tubular structures as a preprocessing step before segmentation. Morphological image processing methods are used to extract the morphology features, namely, number of vessels (NV) and branching points (NB), vessel-to-tissue ratio (VR), and the mean vessel length (VL), tortuosity (VT), and diameter (VD) from the tumor vascular network. Finally, a support vector machine (SVM) is trained and validated using leave-one-out cross-validation technique. The proposed image analysis strategy was able to predict the patient outcome with 90% accuracy when the SVM was trained with the three features together (NB, NV, VR). Experimental results indicated that morphological features of tumor microvascular networks may be significant predictors for TACE response. Reliable prediction of the TACE therapy response may help provide effective therapy planning.

Ultrasonography in Undergraduate Medical Education: A Systematic Review

OBJECTIVES

The purpose of this study was to conduct a systematic review of the evidence of educational outcomes associated with teaching ultrasonography (US) to medical students.

METHODS

A review of databases through 2016 was conducted for research studies that reported data on teaching US to medical students. Each title and abstract were reviewed by teams of 2 independent abstractors to determine whether the article would be ordered for full-text review and subsequently by 2 independent authors for inclusion. Data were abstracted with a form developed a priori by the authors.

RESULTS

Ninety-five relevant unique articles were included (of 6936 identified in the databases). Survey data showed that students enjoyed the US courses and desired more US training. Of the studies that assessed US-related knowledge and skill, most of the results were either positive (16 of 25 for knowledge and 24 of 58 for skill) or lacked a control (8 of 25 for knowledge and 27 of 58 for skill). The limited evidence (14 of 95 studies) of the effect of US training on non-US knowledge and skill (eg, anatomy knowledge or physical examination skill) was mixed.

CONCLUSIONS

There is ample evidence that students can learn US knowledge and skills and that they enjoy and want US training in medical school. The evidence for the effect of US on external outcomes is limited, and there is insufficient evidence to recommend it for this purpose at this time.