European journal of radiology
-
Color Doppler imaging (CD) has had a great impact on ultrasonography (US). This technique depicts local flow by encoding an estimate of the mean Doppler frequency shift at a particular position in color. However, the choice of the mean frequency shift as the parameter for representing flow in color Doppler is somewhat arbitrary. Power Doppler ultrasound is a technique that encodes the power in the Doppler signal in color. This parameter is fundamentally different from the mean frequency shift. The frequency is determined by the velocity of the red blood cells, while the power depends on the amount of blood present. Providing an image of a different property of blood flow, power Doppler has shown several key advantages over colour Doppler, including higher sensitivity to flow, better edge definition and depiction of continuity of flow. In this paper we review the results of power Doppler clinical studies. ⋯ Although the actual role of power Doppler in changing patient management has not been assessed yet, this technique can depict flow which was previously undetectable, and thus permits an easier and more confident diagnosis in body regions where the ultrasound signal is weak because blood vessels are small.
-
Since 1975-80, worldwide but mostly in Europe and Japan, sonography has become the imaging technique of choice for guiding percutaneous interventional procedures for diagnostic or therapeutic purposes. In the last 10 years, the most important advances in interventional ultrasound have occurred in therapeutic applications, fostering and facilitating the development of the so-called minimally-invasive techniques. Among all these new applications for the treatment of fluid collections, inflammatory diseases, benign and malignant tumors, the most recent dramatic advances have occurred in primary and secondary liver malignancies, which will be the focus of this review. ⋯ Multiple fibers (beam splitters) are usually required to achieve a sufficiently wide necrosis volume. The reported success rate (complete necrosis and local control of tumor growth) ranges 45-75%) of the lesions, mostly liver metastates from colorectal carcinoma. An equally low rate of complications is reported for interstitial laser photocoagulation as for radiofrequency ablation, that is no more than 2-3% of cases. (ABSTRACT TRUNCATED)
-
Transcranial color Doppler sonography permits the accurate assessment of intracranial arteries. The latest Doppler units, using the color and power techniques, can show even very small flow volumes (1 x 1 mm). Low frequency (2-2.5 MHz) and very focused transducers are used in transcranial color Doppler. The skull is a very strong barrier for ultrasounds, which requires the use of some acoustic windows like some thin portions of the skull bone or some natural skull foramina. The use of echocontrast agents in color Doppler seems to increase the applications of transcranial studies. ⋯ With reference to internal carotid stenoses, the main applications of transcranial color Doppler are the study of intracranial vessels, of intracranial arterial stenosis, of arteriovenous malformations and of Willis circle aneurysms, as well as the monitoring of blood flow velocity during carotid endarterectomy. Echocontrast agents play an important role in the visualization of intracranial vessels.
-
Sonography is well suited for breast studies. Adequate equipment is needed to acquire high quality images because several technical factors influence ultrasound images. Thus, the use of high frequency dynamic scanning probes, the ultrasound beam focusing corrected for the near field, the adjustment of the gain and image contrast may all interfere with ultrasound beam reflection and scattering, determined by the heterogeneity of the gland parenchyma. ⋯ In the last few years, several quality assurance programs have been introduced. Dedicated phantoms are generally used. Recently, computer systems have been also developed.
-
Radiography offers more information than any other imaging modality in the study of bone lesions and remains the cornerstone for the differential diagnosis of skeletal tumors and tumor-like lesions thanks to its higher specificity in detecting tumor morphologic hallmarks. the radiographic features that help the radiologist make the diagnosis of a bone tumor or tumor-like lesion, or at least narrow the diagnostic possibilities, include patterns of bone destruction (geographic, moth-eaten and permeated), lesion margins (from sclerotic rim to ill-defined margin), internal characteristics of the lesion (non-matrix producing tumors, non-mineralized matrix producing tumors, mineralized matrix producing tumors), type of host bone response (medullary or periosteal), location (femur, tibia, humerus, etc.), site (metaphysis, diaphysis or epiphysis), and position (central, eccentric or periosteal) of the lesion in the skeletal system and in the individual bone, soft tissue involvement, and single or multiple lesion nature. Patterns of bone destruction, margins, and reactive changes in the host bone clearly depict the growth rate of a bone lesion, that is its biologic activity; the matrix of the lesion, as well as lesion location, site and position may allow a specific diagnosis. This general information coupled with clinical information helps define whether the lesion is neoplastic or non-neoplastic, benign or malignant, primary or metastatic, and will help further direct the subsequent work-up. ⋯ The main role of MRI lies in local tumor staging, especially for planning limb-salving resections. Biopsy is the definitive diagnostic procedure and should be carried out only after the appropriate diagnostic and staging tests. Whenever a bone lesion is suspected, clinical-radiologic pathologic correlation is essential to make a more accurate diagnosis and to improve patient care.