Biomedical subjects
G Rizzatto
Publications and source records attributed to G Rizzatto.
Evolution of ultrasound transducers: 1.5 and 2D arrays.
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Power Doppler sonography: general principles, clinical applications, and future prospects.
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.
Ultrasound transducers.
Sonography is facing a new technological revolution. Recent advances in ultrasound technology are increasing spatial, contrast and vascular resolution. Transducers play an important role in achieving these improvements; their technology is widely reviewed in this paper. Physics and technology relate to image quality and its clinical potentials. Large annular arrays made the progression of imaging quality; they are still a very good choice for scanning superficial structures. New broadband linear arrays approach their quality and allow to visualize the flow within very small vessels; they permit new harmonic imaging that reduces image noise and clutter caused by the body wall. New advances include digital beamformers that work at their best when coupled with broadband technology. New multi-layer and multi-array scanheads improve the signal-to-noise ratio and increase the transmitted energy. New transducers and imaging algorithms allow real-time acquisition of large fields of view and even of three-dimensional volumes. Further refinement of two-dimensional matrix transducers will produce high-definition volumetric images. Evolution in transducers technology permits to interrogate the vessels with higher Doppler frequencies extending the anatomical perception and opening new fields of investigation.
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.
[Contrast media in ultrasonography. Breasts].
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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.
Percutaneous US-guided radio-frequency tissue ablation of liver metastases: treatment and follow-up in 16 patients.
PURPOSE: To determine the potential efficacy of radio-frequency (RF) ablation of liver metastases during long-term follow-up. MATERIALS AND METHODS: Sixteen patients with 31 hepatic metastases were treated with percutaneous, ultrasound-guided RF ablation. RF was applied to monopolar electrodes (2-3-cm tip exposure) either individually or within a multiprobe array (two to four probes) for 6 minutes at 90 degrees C over one to four treatment sessions per metastasis. RESULTS: In only one of 75 sessions, a moderate complication, self-limited intraperitoneal hemorrhage, was observed. Four patients (four lesions) underwent surgical resection 15-60 days after RF treatment. Residual, viable tumor was seen in all of these patients. The remaining 12 patients were followed up for 9-29 months (mean, 18.1 months). In these patients, 18 of 27 lesions remained stable or decreased in size and showed no enhancement at computed tomography and/or magnetic resonance imaging for at least 9 months. Two patients died of disseminated disease at 13 months and one at 16 months. Disease-free survival was achieved in eight patients. CONCLUSIONS: RF ablation appears to be a simple, safe, and potentially effective treatment for selected patients with liver metastases and may become a less invasive alternative to surgical therapy.
[Power Doppler: physical and constructive principles and comparison with Doppler color].
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Pyogenic liver abscesses: 13 years of experience in percutaneous needle aspiration with US guidance.
PURPOSE: To determine the efficacy of percutaneous needle aspiration (PNA) with antibiotic therapy in treatment for pyogenic liver abscess (PLA). MATERIALS AND METHODS: One hundred fifteen patients (59 male; 56 female; age range, 16-86 years; mean age, 45.3 years) with 147 PLAs (mean diameter, 6.8 cm; range, 3-16 cm) underwent PNA with ultrasound (US) guidance and antibiotic therapy. Needle caliber (22-16 gauge) was tailored to PLA volume. If necessary, PNA was repeated every 3-7 days. RESULTS: Three hundred one PNAs were performed (range, 1-4 per patient; mean, 2.2 per patient). A single puncture was sufficient in 57 patients. Cure (normalization of clinical and laboratory parameters and resolution of hepatic lesions) was achieved in 113 patients (98.3%). Two patients with large PLAs required surgery. Patients were hospitalized 7-24 days (mean, 9 days). In the last eight patients, all abscesses were evacuated in one session. Neither complications nor deaths ensued. Recurrence of PLA was not observed in any patient during follow-up (6-36 months). CONCLUSION: US-guided PNA with antibiotic therapy in treatment for PLA is a valid alternative to prolonged catheter drainage.
Color Doppler sonography of salivary glands.
OBJECTIVE: We used color Doppler sonography to evaluate the vascular anatomy of the salivary glands and to analyze physiologic changes that occur during salivary stimulation in normal subjects and the flow alterations that occur in diseased glands. SUBJECTS AND METHODS: The vascular appearance of the three major salivary glands was examined in healthy volunteers (n = 24); in patients with chronic autoimmune diseases, including Sjögren's syndrome (n = 23) and salivary sarcoidosis (n = 2); and in a variety of benign (n = 49) and malignant (n = 13) nodules. Physiologic changes were assessed in healthy volunteers by means of a stimulation test with lemon and were quantified with color images and spectral analysis. Tumor vascularity was graded on a four-step analog scale of 0 to (+3) and classified as either peripheral or hilar, depending on the distribution of vessels. RESULTS: In the control subjects, color Doppler imaging accurately reflected the complex vascular anatomy of the salivary glands and showed dramatic changes occurring in parenchymal vessels during lemon stimulation as a result of the intense hyperemia associated with the secretion of saliva. Sjögren's syndrome and sarcoidosis showed a diffuse hypervascular pattern when morphologic changes of salivary parenchyma were seen on gray-scale sonograms. Benign tumors showed a lower grade of vascularity than did malignant tumors. All but one of the hypovascular nodules graded as 0 (n = 8) and + (n = 23) were benign. Conversely, eight of 11 nodules labeled with the highest grade of tumor vascularity (+3) were malignant. When the pattern of tumor flow signals was peripheral, it could be considered specific enough to aid in diagnosing pleomorphic adenoma. Peak systolic velocities greater than 60 cm/sec were never detected in benign tumors and were seen in only 44% of malignant tumors. CONCLUSION: Color Doppler sonography is a promising technique for analyzing the vascularity of the salivary glands and for characterizing some pathologic conditions. Our experience suggests that color Doppler sonography can provide additional diagnostic information in patients with chronic inflammatory diseases or suspected malignant tumors and can help in differentiating pleomorphic adenomas from other salivary gland tumors.
Carotid body tumors: US evaluation.
The ultrasound (US) findings in 20 patients with 23 carotid-body chemodectomas were reviewed. Twenty-two of 23 tumors could be seen at US; the remaining lesion could not be differentiated from surrounding enlarged lymph nodes resulting from thyroid cancer. The lesions were solid, slightly heterogeneous masses that ranged in size from 1.2 to 5.0 cm and were located within the carotid bifurcation. Pulsed Doppler analysis of blood flow within the tumor mass was possible in eight patients with nine chemodectomas, and low-resistance waveforms were obtained from multiple sites within the mass in all cases. The diagnostic possibility of a chemodectoma has to be considered when a solid mass is detected within the carotid bifurcation. On the basis of these findings, as US diagnosis was possible in 18 of 20 patients in the authors' series. Doppler analysis of the mass to evaluate intratumor blood flow is helpful in differentiating chemodectomas from other solid, nonhypervascular masses.
[A multicenter study for the evaluation of the diagnostic efficiency of mammography and echography in nonpalpable breast neoplasms].
The Breast Section of the Italian Society of Radiology set up a cooperative study which included 17 Departments of Radiology and Breast Diagnosis in order to evaluate the diagnostic accuracy of US versus mammography in nonpalpable breast lesions. From January 1, 1989 to december 31, 1990, 400 nonpalpable breast lesions (142 benign lesions, 59 in situ and 199 infiltrating carcinomas) were detected by mammography and/or US; they had questionable/suspicious findings which called for further investigation by means of cytology and/or histology. US proved much less sensitive in non-palpable carcinomas than mammography (49.2% vs 93.8%), also in younger women, and failed to detect 50% of the benign/malignant nonpalpable lesions identified by mammography. US sensitivity was directly related to lesion diameter and probe frequency: 38.7% in infiltrating carcinomas < or = 5 mm vs 56.8% in those > 10 mm; 12% in the patients examined with a 5-MHz probe vs 57.7% in those examined with a > or = 7.5-MHz probe. Furthermore, the most significant US patterns of nonpalpable lesion were irregular contours, posterior attenuation and irregular internal echoes, while an irregular skin line and Cooper ligaments had no significant relation with carcinoma. Thus, breast US cannot be used as a screening test on asymptomatic patients not even on young women with radiologically dense breasts. On the contrary, US performed with high-frequency probes is useful in the assessment of nonpalpable lesions identified by mammography, and allows, in many cases, US-guided cytology and preoperative localization.
[Contrast media in echography].
In medical US, the use of specific contrast media to increase the echogenicity of structures and organs changes their absorption of the US beam, and modifies the through-transmission velocity. This can be of great diagnostic value. Contrast media can help depict vessels and cavities, increase the sensitivity of Doppler examination, and make the differentiation of normal and pathologic tissues easier. The products which are currently available do not completely fulfill the needs of clinical researchers. The first papers reporting on some clinical applications of these contrast media in humans are now appearing in literature. Contrast media for diagnostic US can be classified in five groups: 1) free gas bubbles; 2) stabilized gas bubbles; 3) colloidal suspensions; 4) emulsions; 5) aqueous solutions. These agents are quite different, as to both chemical and physical features and distribution within living tissues. Different clinical applications are thus possible for each of them; a unique contrast medium which will meet all the needs of the various clinical situations seems inconceivable at present. Most probably, a variety of products will develop, each with its own application field; in clinical practice, it seems likely that different products will be used, according to the specific clinical needs.
[Color-Doppler instruments: their design principles and modes of use].
The use of color-Doppler US equipment allows the clinician to evaluate, at the same time and within the same image, both shape and structure of the examined organs and the flow patterns in the vessels within them. Such information as direction and velocity of blood flow are displayed with a variety of intravascular colors, according to a conventional code. Moreover, this diagnostic method can provide physiological and anatomical pieces of information in the same image and is therefore widely used in medical imaging. However, the images obtained by means of color-Doppler units are not always easy to understand and diagnostic misinterpretations may occur. In this paper we will summarize the physical and technological principles on which such units are based. In the first half of paper, the problems relative to acquisition and construction of the images are presented, together with the different technical approaches used to obtain flow velocity information. Moreover, the relationships between the "black-and-white" and the "color" parts of the images are described. The principles according to which color is assigned to vessels are reported, together with the patterns exhibited by a vessel according to the type of transducer used to examine it. The non-linear correlation between the color scale and flow velocities is also discussed. The second half of the paper deals with technical parameters of color-Doppler scanning, discussing the criteria of choice of transducers, the determination of Doppler angle, the setting of both wall filters and scanning depth. The problem of pulse repetition frequency (PRF) setting is also addressed; this parameter is especially critical in color-Doppler studies. The authors believe that careful setting of all examination parameters and the good knowledge of the physical and technological factors underlying color-Doppler images are the basis for a correct and useful approach to this fascinating technique.
Sonographic appearance of primary retroperitoneal cysts.
The sonographic findings observed in four patients with primary retroperitoneal cysts were reviewed. All lesions presented as fluid-filled masses with anechoic content and regular margins; all increased through transmission. Preoperative location of the cysts within the retroperitoneal space was possible in all cases by either real-time ultrasound (US) analysis of the different relationships of the kidneys and the cysts during respiratory movements or the anterior displacement of surrounding structures. A differential diagnosis among retroperitoneal lesions containing fluid is difficult and cannot be obtained with imaging methods alone. However, preoperative knowledge of both the retroperitoneal location of the disease process and its fluid content may help to narrow the diagnostic possibilities, thus allowing the surgeon to more accurately plan the therapeutic approach to the patient.
[Role of ultrasonics in the diagnosis of subclinical carcinoma of the breast].
The authors report the results of a retrospective multicentric study concerning the sonographic diagnosis of subclinical breast cancer, 11,254 patients were examined by means of mammography, with last-generation mammographic equipment, and by means of real-time US with 7.5-10 MHz transducer. Fifty-seven subclinical breast cancers were identified and histologically confirmed. US detected 30/57 neoplastic lesions, versus mammography 47/57; in particular, US identified 10 cancers missed at mammography, while the latter detected 27 malignant lesions missed at US. Mammographic accuracy in the early detection of breast cancers was 82.4%, while US accuracy was 52.6%. Mammographic false negatives were due to opacity of the glandular parenchyma. US false negatives presented at mammography as microcalcifications (67%), lesions less than 1 cm phi (22%), and indirect signs (11%). The results of this study demonstrate the important role of US in women with radiographically-dense parenchymal patterns, but confirm the superiority of mammography in the detection of subclinical breast cancer.
Normal anatomy and pathologic changes of the small bowel mesentery: US appearance.
The ultrasonographic (US) appearance of the normal small bowel mesenteric leaves was evaluated in two in vitro studies and in 30 patients. Such structures had an elongated shape, echogenic surfaces, and small vessels in their center and could be recognized in 28 of the 30 patients. They did not show active movements, and at their distal end, the small bowel loops could be seen and peristalsis detected. Doppler signals were obtained from the small vascular structures in their center in three additional cases. On the basis of these anatomic findings, pathologic changes such as lymphoma, desmoid tumor, metastatic lesions, dilated vessels, and edema could be detected in 15 patients. When examining with US patients with diseases prone to involve the mesentery, careful attention should be given to this structure, since useful information about the abdominal spread of the disease can be obtained.