[Sonographic imaging of the prostate]

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.

Contrast-enhanced ultrasound perfusion imaging of organs

In multimodal radiologic imaging, contrast-enhanced ultrasound (CEUS) is increasingly used. One of the advantages of CEUS is the possibility of repeated application of contrast media without decreasing renal function or affecting the thyroid gland. Small solid liver lesions can be diagnosed and detected with high accuracy. Moreover, solid lesions in other abdominal organs can also be characterized. Frequent applications for solid lesions in the near field concern thyroid tumors and lymph nodes. For prostate diagnostics, CEUS can be used with an endorectal probe and perfusion imaging. This review explains how the additional (semi-)quantitative perfusion analysis, especially time-intensity curve (TIC) analyses, and wash-in/wash-out kinetics of integrated or external perfusion software programs facilitate new options in dynamic assessment of microvascularization during tumor follow-up care and even minimally invasive tumor therapy.

[Imaging for initial diagnosis of localized prostate cancer]

The initial diagnosis of prostate cancer has been traditionally performed using systematic core biopsies with the use of magnetic resonance imaging (MRI) reserved to problem-solving scenarios. There is currently an ongoing paradigm shift towards the use of MRI prior to targeted biopsy as the standard approach. Prostate cancer therefore does not remain the last solid tumor entity diagnosed by non-targeted techniques but joins other solid tumor entities for which targeted diagnostic approaches have existed for a while. However, the complexity of the background tissue signal in the prostate makes lesion detection challenging. This article will provide an overview of the components of multiparametric prostate MRI and their interpretation using structured interpretation according to the current PI-RADSv2 (Prostate Imaging Reporting and Data System version 2) guidelines and of novel ultrasound techniques for primary diagnosis.

[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.