Giorgio Rizzatto

Power Doppler sonography: General principles, clinical applications, and future prospects

Abstract. Power Doppler sonography (PD) is a technique that displays the strength of the Doppler signal, rather than the flow velocity and directional information. Its increased flow sensitivity and better vascular delineation have been used to document the presence and characteristics of flow in vessels that are poorly imaged with conventional color Doppler (CD), to identify areas of ischemia, to demonstrate inflammatory hyperemia or increased and irregular flow in tumors, as well as to assess serial vascular changes related to interval therapy. The present review reports the general principles of PD, portrays the results of clinical studies available in the literature, and suggests future trends of development.

High-resolution sonography of breast carcinoma

The use of broad band transducers determined a great increase in spatial, contrast and vascular resolution of ultrasound probes dedicated to breast studies. Providing better definition of normal as well as pathologic features, high resolution sonography improves the specificity of the diagnosis for the majority of malignant nodules and allows a better definition of both local and regional staging. The most impressive results have been achieved in the evaluation of multifocal and multicentric carcinomas, in determining the size of the tumor, its degree of invasion of the surrounding tissues and of the ducts. Color and power Doppler offer further characterization that may be particularly useful in evaluating tumor vascularity during therapies that are planned before surgery. These new staging possibilities must push the radiologists to adequate their instruments and their methods to provide up-to-date and more accurate informations to the surgeon.

Towards a more sophisticated use of breast ultrasound.

The diagnostic role of breast ultrasound has been expanded along with the improvement of high-frequency transducers and digital technology. Vascular assessment has progressed enough to depict normal vascular anatomy of the breast and the lymph nodes. Pathologic vessels are seen in almost all the tumors, thus improving US sensitivity for nonpalpable carcinomas. New contrast agents will recirculate enough to search for vascular foci during a thorough investigation of both breasts and nodal stations. The US role in screening might be now revised. Many factors are now in favor of targeted US screening in dense and complex breasts and in high-risk patients. Screening sensitivity is significantly increased. Most of these US-detected tumors are small enough to be curable. Mammography and sonography together are a unique problem-solving and cost-effective tool. They can easily guide fine aspirations or larger biopsies reducing the cost of unnecessary surgical procedures. Accurate US investigations facilitate the surgical approach to a very conservative and cosmetic operation. High-resolution sonography can demonstrate the intraductal spread of tumors and their multiple foci more easily than mammography, but US diagnosis is less sensitive than magnetic resonance mammography in the evaluation of the real tumoral extent. Ductal branching has a complex pattern; therefore, intraductal spread and multifocal nodes are better demonstrated by multiplanar analysis of 3D ultrasound data volumes. Sonography can easily explore the different nodal chains. Metastatic disease is indicated by an enlarged and round shape and the absence of the echogenic hilum. Irregularities in the cortex are a very useful sign in metastatic nodes without total replacement of lymphoid tissue by neoplastic cells. These signs are very specific. A time-consuming, radiation-emitting and costly sentinel biopsy may be avoided in one of every five clinically node-negative patients. But preoperative US assessment is also important as sonography is very sensitive in patients with extensive nodal involvement that might result negative at the sentinel node procedure. New technologies and contrast agents allow perfusional studies that enhance the contrast resolution and will increase the sensitivity of US for small nodal metastases.

Breast ultrasound and new technologies

Technological advances are opening new fields of investigation for breast ultrasound. Specificity and color Doppler, staging and extended clinical roles in benign conditions are reviewed according to the state-of-the-art technology. Annular arrays are the best technical choice but new broadband linear arrays approach their quality and allow to visualize very slow flows within the breast. Still limitations exist and ultrasound is not suitable for screening. Providing better definition of normal as well as abnormal features, high-resolution sonography improves the specificity of the diagnosis for the majority of nodules and allows a better definition of both local and regional staging in nodular and diffuse conditions. Color Doppler and contrast media are increasing ultrasound specificity and are particularly useful in evaluating vascularity during therapies. Impressive results are achieved in the study of multifocal and multicentric carcinomas, in determining the degree of tumoral invasion of the surrounding tissues and of the ducts. Local and regional staging are greatly improved; the information given to the surgeon is more precise and allows easier therapeutic decisions. The diagnostic role of high-frequency ultrasound is also convincing in most benign conditions like inflammations, traumas and duct ectasia. In most of these conditions sonography is the best imaging modality to study the disease type and extent. The ability to monitor treatment efficacy or the natural outcome makes ultrasound and color Doppler a gold standard for breast inflammations.

A new method to combine contrast-enhanced magnetic resonance imaging during live ultrasound of the breast using volume navigation technique: a study for evaluating feasibility, accuracy and reproducibility in healthy volunteers.

OBJECTIVES To evaluate feasibility, accuracy and reproducibility of combined US-MR of the breast using volume navigation technique. SUBJECTS AND METHODS Five healthy females underwent bilateral contrast-enhanced MR (CE-MR) of the breast in supine position, after positioning three couples of markers on the breast. After CE-MR data uploading in the ultrasound (US) database, manual co-registration was obtained during live US of the breast by means of an electromagnetic transmitter positioned near the subject under examination and two electromagnetic sensors were mounted on the transducer bracket. Transmitter and sensors were connected to a position-sensing unit embedded in the US equipment allowing to track probe position and orientation within the electromagnetic field. Live US image were co-registered to the previously loaded breast CE-MR volume by coupling markers. For each subject, two independent radiologists recorded the examination time and verified twice image alignment using five fixed checkpoints. Pair t Student test and Wilcoxon test were used for statistical analysis. RESULTS In all subjects US and CE-MR images were successfully combined. The examination time was 10±2 vs. 9±4 min, respectively (p=0.642; NS). A total of one hundred measurements of images misalignment were performed: the measurements recorded between the two operators were 0.42±0.32 cm and 0.58±0.41 cm (p=0.161; NS), and 0.50±0.32 cm and 0.56±0.52 cm (p=0.928; NS), respectively. DISCUSSION In our preliminary experience, volume navigation technique appears to be a accurate and reproducible method to combine CE-MR image during unilateral US of the breast.

Pancreatic cystadenocarcinoma: diagnostic problems

Eleven cases of pancreatic cystadenocarcinoma were studied with respect to the differential diagnosis from that of pancreatic pseudocysts, using diagnostic ultrasound as the initial investigative technique. Most of the cases presented an ultrasonic picture that correlated well with the gross pathology, but this correlation was not reliable enough to be considered characteristic in differentiating such masses from pseudocysts. The authors divide the cystadenocarcinomas of the pancreas into four echographic classes. In all but one of the classes, diagnostic ultrasound was insufficient by itself to render an accurate diagnosis. In such cases other techniques, i.e. CT, tissue biopsy, and especially angiography, were required for a reliable diagnosis.

The sonographic appearance of duodenal lesions.

The sonographic findings in 17 patients with duodenal tumors and in one patient with a benign ulcer and stricture of the duodenum were reviewed. An abdominal mass was detected sonographically in all patients; in 15 of 18 cases, such lesions presented high‐level central echoes and hypoechoic periphery. Identification of the duodenal origin of the disease was possible by sonography in only 16 of 18 patients: by evaluation of the relationship of the mass with abdominal vessels in eight patients; by demonstrating that the lesion was continuous with a normal duodenum in seven patients; or by demonstrating the mass within the duodenum itself in one patient. Signs and symptoms of duodenal tumors are usually nonspecific, and sonography can be used as the first imaging method in these cases. A careful analysis of the relationship of the tumor to surrounding structures may allow correct identification of its origin.

Ultrasonography of the normal adrenal glands: a study using linear-array real-time equipment

The adrenal glands were evaluated in 70 normal volunteers using linear-array real-time ultrasonography. All the scanning approaches described for manual B-scanning were used and, on the left side, longitudinal scans along the axillary lines were also performed. The right adrenal gland was imaged in 68 of the 70 volunteers and the left gland in 63. The dynamic capabilities of real-time equipment were of great help for proper localisation and identification of the glands. Changes in the scanning plane demonstrated variations in the adrenal morphology, because different portions of the gland were encountered by the scanning beam.

The value of the posterior oblique longitudinal scan in renal ultrasonography.

A new way of scanning the kidney by ultrasonography is the posterior oblique longitudinal scan. This provides new information about renal anatomy, especially the renal aspect of the parenchyma and the hilus in its vertical axis. It supplies useful diagnostic information particularly in pseudotumours, hydronephrosis, and lipomatosis.