[Latest developments in ultrasound of the liver]

Ultrasound-New Techniques Are Extending the Applications

BACKGROUND

Sonography is often the first imaging procedure to be used in diagnostic investigation of the abdomen. The aim of this article is to provide a new interdisciplinary overview of recent groundbreaking advances in this modality.

METHODS

A selective survey of the literature in PubMed was conducted. The literature search was carried out in 2021-2022 and included publications over the period 2004-2022.

RESULTS

The novel sonographic software techniques can be divided into algorithms that deal with conventional B-scan optimization and new programs that extend the scope of sonographic examination. The latter include elastography, contrast-enhanced sonography, and image fusion in combination with other cross-sectional imaging modalities. Elastography can be used to assess the presence of steatosis, fibrosis, or cirrhosis in patients with liver disease. One study reported diagnostic accuracy of 84-87% for the diagnosis of significant fibrosis (F2), 89-91% for the diagnosis of severe fibrosis (F3), and 92-93% for the diagnosis of liver cirrhosis (F4). Contrast-enhanced sonography is used for evaluation of tumors and trauma. A prospective multicenter study found sensitivity of 95.8% for the characterization of malignant lesions and specificity of 83.1% for benign lesions. Image fusion has the potential to improve the diagnostic assessment of parenchymatous organs, vascular conditions, and the prostate.

CONCLUSION

With continuous improvement of the B-scan and the development of high-frequency probes and novel investigation techniques, sonography has become established as an increasingly autonomous examination procedure.

Prospective evaluation of 4-D contrast-enhanced-ultrasound (CEUS) imaging in bladder tumors

PURPOSE

The evaluation of the potential clinical benefit of four-dimensional ultrasound (4D-US) in the assessment of bladder cancer (BC).

MATERIAL AND METHODS

20 patients with indication for cystoscopy for suspicion of bladder cancer were prospectively included in this study. All patients underwent two-dimensional ultrasound (2D-US), contrast enhanced ultrasound (CEUS) and real-time four-dimensional ultrasound (4D-US). All acquisitions were compared to each other in regard to image quality. This assessment was done using a 6 point scale (1 = best). All patients underwent subsequently cystoscopy with resection of the tumor (TURB), due a histopathological analysis was possible.

RESULTS

All examinations were performed successfully and no patient had to be excluded from the study. Patients acceptance of 4D-US was consistently good. No adverse events occurred. Image quality of real time 4D-US (score: 1.27±0.46) was significantly superior (p < 0.001) to both, conventional 2D-US (score: 2.33±0.62) and also to 2D-CEUS (score: 2.00±0.53). In terms of tumor detection no superiority was evident for 4D-US compared to 2D-US or in utilization of CEUS (sensitivity = 0.89; specificity = 1.00; positive predictive value = 1.00; negative predictive value = 0.50; AUC = 0.944; (95% CI: 07.43-0.998)).

CONCLUSION

The assessment of bladder cancer using real time 4D-US is feasible and improves the image quality and therefore also the precise anatomical consistency of intravesical tumor masses.

[Contrast-enhanced ultrasound (CEUS) and image fusion for procedures of liver interventions]

CLINICAL/METHODICAL ISSUE

Contrast-enhanced ultrasound (CEUS) is becoming increasingly important for the detection and characterization of malignant liver lesions and allows percutaneous treatment when surgery is not possible. Contrast-enhanced ultrasound image fusion with computed tomography (CT) and magnetic resonance imaging (MRI) opens up further options for the targeted investigation of a modified tumor treatment.

METHODICAL INNOVATIONS

Ultrasound image fusion offers the potential for real-time imaging and can be combined with other cross-sectional imaging techniques as well as CEUS.

PERFORMANCE

With the implementation of ultrasound contrast agents and image fusion, ultrasound has been improved in the detection and characterization of liver lesions in comparison to other cross-sectional imaging techniques. In addition, this method can also be used for intervention procedures. The success rate of fusion-guided biopsies or CEUS-guided tumor ablation lies between 80 and 100% in the literature.

ACHIEVEMENTS

Ultrasound-guided image fusion using CT or MRI data, in combination with CEUS, can facilitate diagnosis and therapy follow-up after liver interventions.

PRACTICAL RECOMMENDATIONS

In addition to the primary applications of image fusion in the diagnosis and treatment of liver lesions, further useful indications can be integrated into daily work. These include, for example, intraoperative and vascular applications as well applications in other organ systems.

Spleen thickness can predict significant liver pathology in patients with chronic hepatitis B with persistently normal alanine aminotransferase or minimally raised alanine aminotransferase: a retrospective study

OBJECTIVE

Liver biopsy is the gold standard test for assessment of liver pathology. This study was performed to assess the predictive value of spleen thickness for liver pathology and the role of routine follow-up procedures in significant liver pathology for patients with chronic hepatitis B (CHB) with persistently normal alanine aminotransferase (PNALT) or minimally raised alanine aminotransferase (ALT).

METHODS

Patients with CHB who underwent percutaneous liver biopsy were retrospectively reviewed. The relationship of liver pathology with age, ALT, hepatitis B e-antigen, and spleen thickness was statistically analyzed, and the predictive accuracy of spleen thickness was evaluated.

RESULTS

In total, 80.65% of patients had significant necroinflammation and/or fibrosis. Nearly 60% of patients had splenomegaly, of which 89.12% had a histopathological grade of ≥G2 and/or S2. Spleen thickness was predictive of liver pathology, and significant histological findings increased as the hepatitis B virus (HBV) DNA level increased.

CONCLUSIONS

Spleen thickness is an effective predictor of liver pathology in patients with PNALT or minimally raised ALT. Additionally, the prevalence of significant histological findings tended to increase as the HBV DNA level increased. Patients with CHB and splenomegaly and a high HBV DNA level should be treated early with antivirals to improve liver pathology.

[Possibilities of sonographic image fusion: Current developments]

CLINICAL/METHODICAL ISSUE

For diagnostic and interventional procedures ultrasound (US) image fusion can be used as a complementary imaging technique.

METHODICAL INNOVATIONS

Image fusion has the advantage of real time imaging and can be combined with other cross-sectional imaging techniques.

PERFORMANCE

With the introduction of US contrast agents sonography and image fusion have gained more importance in the detection and characterization of liver lesions.

ACHIEVEMENTS

Fusion of US images with computed tomography (CT) or magnetic resonance imaging (MRI) facilitates the diagnostics and postinterventional therapy control.

PRACTICAL RECOMMENDATIONS

In addition to the primary application of image fusion in the diagnosis and treatment of liver lesions, there are more useful indications for contrast-enhanced US (CEUS) in routine clinical diagnostic procedures, such as intraoperative US (IOUS), vascular imaging and diagnostics of other organs, such as the kidneys and prostate gland.

[Sonographic imaging of the prostate]

Accurate identification of the location of carcinoma in the prostate is essential for long-term therapeutic success, in particular for minimally invasive procedures. In recent years many new positive study results for prostate imaging have been reported which must be compared and evaluated and previous conservative assessments may need to be re-evaluated. In addition, combinations of different imaging techniques are increasingly being used in daily clinical routine. Due to technical advancements in sonographic imaging, such as elastography and contrast-enhanced ultrasound (CEUS), the detection rate of prostate cancer can be increased. An overview of the different imaging modalities and current literature are presented in this article.

Visualization, imaging and new preclinical diagnostics in radiation oncology

Innovative strategies in cancer radiotherapy are stimulated by the growing knowledge on cellular and molecular tumor biology, tumor pathophysiology, and tumor microenvironment. In terms of tumor diagnostics and therapy monitoring, the reliable delineation of tumor boundaries and the assessment of tumor heterogeneity are increasingly complemented by the non-invasive characterization of functional and molecular processes, moving preclinical and clinical imaging from solely assessing tumor morphology towards the visualization of physiological and pathophysiological processes. Functional and molecular imaging techniques allow for the non-invasive characterization of tissues in vivo, using different modalities, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, positron emission tomography (PET) and optical imaging (OI). With novel therapeutic concepts combining optimized radiotherapy with molecularly targeted agents focusing on tumor cell proliferation, angiogenesis, and cell death, the non-invasive assessment of tumor microcirculation and tissue water diffusion, together with strategies for imaging the mechanisms of cellular injury and repair is of particular interest. Characterizing the tumor microenvironment prior to and in response to irradiation will help to optimize the outcome of radiotherapy. These novel concepts of personalized multi-modal cancer therapy require careful pre-treatment stratification as well as a timely and efficient therapy monitoring to maximize patient benefit on an individual basis. Functional and molecular imaging techniques are key in this regard to open novel opportunities for exploring and understanding the underlying mechanisms with the perspective to optimize therapeutic concepts and translate them into a personalized form of radiotherapy in the near future.

[Modern imaging of kidney tumors]

If a renal mass is suspected on clinical examination or ultrasound the finding has to be confirmed by cross-sectional imaging. Methods that are used include multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI). Also contrast-enhanced ultrasound has been successfully implemented in renal imaging and now plays a major role in the differentiation of benign from malignant renal masses. In expert hands it can be used to show very faint vascularization and subtle enhancement. The MDCT technique benefits from the recently introduced dual energy technology that allows superior characterization of renal masses in a single-phase examination, thereby greatly reducing radiation exposure. For young patients and persons allergic to iodine MRI should be used and it provides excellent soft tissue contrast and visualizes contrast enhancement kinetics in multiphase examinations.This article aims at giving a comprehensive overview of these different imaging modalities, their clinical indications and contraindications, as well as a description of imaging findings of various renal masses.

Does contrast-enhanced cervical ultrasonography improve preoperative localization results in patients with sporadic primary hyperparathyroidism?

OBJECTIVE

Pre-operative localization studies are inevitable in patients with primary hyperparathyroidism (pHPT), who are eligible for focused or minimally invasive parathyroidectomy (MIP). High-resolution ultrasonography (US) in combination with planar (99m)Tc-Sestamibi-scintigraphy (MIBI) and additional single-photon emission computed tomography (SPECT) are the standard procedures to localize enlarged parathyroid glands. Our aim was to evaluate the practicability and significance of contrast-enhanced ultrasonography (CEUS) in patients with pHPT.

MATERIALS AND METHODS

All investigations were performed at the University Hospital Marburg. Totally, 25 patients with biochemical proven pHPT underwent preoperative US, MIBI/SPECT, and CEUS. For CEUS, a suspension of phospholipid-stabilized sulfur-hexafluoride (SF6) microbubbles in combination with a special 12 MHz linear US probe was used. All patients were investigated by two sonographers, who did not get to view the findings noted by the other. Finally, surgery was performed and histopathological results were obtained from 24 patients.

RESULTS

In 17 (68%) patients, US and MIBI/SPECT already raised suspicion of parathyroid lesions and all suspected lesions were reassessed by CEUS. However, no additional information was obtained using CEUS. Especially in eight patients with negative or inconsistent US and MIBI/SPECT results, CEUS did not provide additional information regarding the site of the suspected parathyroid adenoma. Overall, no side effects were observed using CEUS. Surgical cure was achieved in all patients.

CONCLUSION

In this limited cohort of patients, no additional information could be obtained using the costly CEUS compared to results of US and MIBI/SPECT.

[Preclinical imaging in animal models of radiation therapy]

CLINICAL/METHODICAL ISSUE

Modern radiotherapy benefits from precise and targeted diagnostic and pretherapeutic imaging.

STANDARD RADIOLOGICAL METHODS

Standard imaging modalities, such as computed tomography (CT) offer high morphological detail but only limited functional information on tumors.

METHODICAL INNOVATIONS

Novel functional and molecular imaging modalities provide biological information about tumors in addition to detailed morphological information.

PERFORMANCE

Perfusion magnetic resonance imaging (MRI) CT or ultrasound-based perfusion imaging as well as hybrid modalities, such as positron emission tomography (PET) CT or MRI-PET have the potential to identify and precisely delineate viable and/or perfused tumor areas, enabling optimization of targeted radiotherapy. Functional information on tissue microcirculation and/or glucose metabolism allow a more precise definition and treatment of tumors while reducing the radiation dose and sparing the surrounding healthy tissue.

ACHIEVEMENTS

In the development of new imaging methods for planning individualized radiotherapy, preclinical imaging and research plays a pivotal role, as the value of multimodality imaging can only be assessed, tested and adequately developed in a preclinical setting, i.e. in animal tumor models.

PRACTICAL RECOMMENDATIONS

New functional imaging modalities will play an increasing role for the surveillance of early treatment response during radiation therapy and in the assessment of the potential value of new combination therapies (e.g. combining anti-angiogenic drugs with radiotherapy).

[Ultrasound-guided image fusion with computed tomography and magnetic resonance imaging. Clinical utility for imaging and interventional diagnostics of hepatic lesions]

Abdominal ultrasound is often the first-line imaging modality for assessing focal liver lesions. Due to various new ultrasound techniques, such as image fusion, global positioning system (GPS) tracking and needle tracking guided biopsy, abdominal ultrasound now has great potential regarding detection, characterization and treatment of focal liver lesions. Furthermore, these new techniques will help to improve the clinical management of patients before and during interventional procedures. This article presents the principle and clinical impact of recently developed techniques in the field of ultrasound, e.g. image fusion, GPS tracking and needle tracking guided biopsy and discusses the results based on a feasibility study on 20 patients with focal hepatic lesions.