Manjiri Dighe

High-Intensity Focused Ultrasound : Current Potential and Oncologic Applications

OBJECTIVE The objective of this article is to introduce the reader to the principles and applications of high-intensity focused ultrasound (HIFU). CONCLUSION Although a great deal about HIFU physics is understood, its clinical applications are currently limited, and multiple trials are underway worldwide to determine its efficacy.

Differential Diagnosis of Thyroid Nodules with US Elastography Using Carotid Artery Pulsation

PURPOSE To explore the sensitivity and specificity of ultrasonographic (US) elastography using carotid arterial pulsation as the compression source for differential diagnosis of thyroid nodules. MATERIALS AND METHODS This HIPAA-compliant study was approved by the ethics committee of the institution, and all patients provided written informed consent. Fifty-eight patients (13 men and 45 women [mean age, 51 years; range, 20-76 years]) were enrolled. A short US examination and elastography with pulsation of the carotid artery used as the thyroid compression source were performed before fine-needle aspiration. Baseband US data were downloaded for off-line analysis. Elastographic maps and the thyroid stiffness index were calculated. The Kruskal-Wallis nonparametric rank sum test was used to assess equality of population medians among the different types of thyroid nodules; the R software environment was used for statistical computing and graphics (http://www.r-project.org/). RESULTS Thyroid stiffness index calculated with elastography using carotid arterial pulsation as the compression source was effective in helping distinguish between papillary carcinomas (n = 10) and other lesions (n = 43) because papillary carcinomas were stiffer than other lesions (P < .0039). CONCLUSION It is possible to distinguish between papillary carcinomas and other lesions with the thyroid stiffness index calculated from US elastography using carotid arterial pulsation.

Ultrasound Thyroid Elastography Using Carotid Artery Pulsation Preliminary Study

The purpose of this study was to evaluate the feasibility of ultrasound thyroid elastography using carotid artery pulsation as the compression source and its potential for differential diagnosis of thyroid nodules.

Congenital Lung Abnormalities: Embryologic Features, Prenatal Diagnosis, and Postnatal Radiologic-Pathologic Correlation

Congenital lung abnormalities are being detected more frequently at routine high-resolution prenatal ultrasonography. The most commonly encountered anomalies include lung agenesis-hypoplasia complex (pulmonary underdevelopment), congenital pulmonary airway malformations, congenital lobar overinflation, bronchial atresia, bronchogenic cysts, congenital high airway obstruction syndrome, scimitar syndrome, and bronchopulmonary sequestration. Recognizing the antenatal and postnatal imaging features of these abnormalities is necessary for optimal prenatal counseling and appropriate peri- and postnatal management. Supplemental material available at http://radiographics.rsna.org/lookup/suppl/doi:10.1148/rg.306105508/-/DC1.

Fetal brain lesions after subcutaneous inoculation of Zika virus in a pregnant nonhuman primate

We describe the development of fetal brain lesions after Zika virus (ZIKV) inoculation in a pregnant pigtail macaque. Periventricular lesions developed within 10 d and evolved asymmetrically in the occipital–parietal lobes. Fetal autopsy revealed ZIKV in the brain and significant cerebral white matter hypoplasia, periventricular white matter gliosis, and axonal and ependymal injury. Our observation of ZIKV-associated fetal brain lesions in a nonhuman primate provides a model for therapeutic evaluation.

Imaging in Pregnant Patients: Examination Appropriateness

A recurring source of contention between clinicians and radiologists continues to be examination appropriateness when imaging pregnant patients. With the multitude of references on potential radiation risks to the fetus, radiologists tend to be cautious and hesitant about exposing the fetus to radiation. This tendency is often interpreted by referring physicians as intrusion into and delay in the care of their patients. The risk burden of radiation exposure to the fetus has to be carefully weighed against the benefits of obtaining a critical diagnosis quickly and using a single tailored imaging study. In general, there is lower than expected awareness of radiation risks to the fetus from imaging pregnant patients. Modalities that do not use ionizing radiation, such as ultrasonography and magnetic resonance imaging, should be the preferred examinations for evaluating an acute condition in a pregnant patient. However, no examination should be withheld when an important clinical diagnosis is under consideration. Exposure to ionizing radiation may be unavoidable, but there is no evidence to suggest that the risk to the fetus after a single imaging study and an interventional procedure is significant. All efforts should be made to minimize the exposure, with consideration of the risk versus benefit for a given clinical scenario.

Fetal Skeletal Dysplasia: An Approach to Diagnosis with Illustrative Cases

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. These conditions are caused by widespread disturbance of bone growth, beginning during the early stages of fetal development and evolving throughout life. Despite recent advances in imaging, fetal skeletal dysplasias are difficult to diagnose in utero due to a number of factors, including the large number of skeletal dysplasias and their phenotypic variability with overlapping features, lack of precise molecular diagnosis for many disorders, lack of a systematic approach, the inability of ultrasonography (US) to provide an integrated view, and variability in the time at which findings manifest in some skeletal dysplasias. US of suspected skeletal dysplasia involves systematic imaging of the long bones, thorax, hands and feet, skull, spine, and pelvis. Assessment of the fetus with three-dimensional US has been shown to improve diagnostic accuracy, since additional phenotypic features not detectable at two-dimensional US may be identified. The radiologist plays a major role in making an accurate diagnosis; however, representatives of other disciplines, including clinicians, molecular biologists, and pathologists, can also provide important diagnostic information.

Ultrasound-Based Elastography: A Novel Approach to Assess Radio Frequency Ablation of Liver Masses Performed With Expandable Ablation Probes A Feasibility Study

Objective. The purpose of this study was to evaluate the technical feasibility of ultrasound‐based elastography as a tool for assessing the size and shape of the coagulation necrosis caused by radio frequency ablation (RFA) probes using expandable electrodes ex vivo as well as in a patient with a liver metastasis. Methods. A commercially available expandable RFA probe was used to create a 3‐cm ablation in a piece of bovine liver. The ablation probe was used in situ to induce tissue deformation for elastography before and after ablation. Ultrasonic radio frequency data were processed to generate elasticity strain images. The appearance of the ablation zone was compared with magnetic resonance imaging and a gross section specimen. One patient with malignant metastatic disease to the liver and a clinical indication for RFA was investigated for the feasibility of percutaneous elastography of RFA using the same technique. Sonographic strain images were compared with the appearance of the nonenhancing ablation zone on contrast‐enhanced computed tomography. Results. Ex vivo, the ablation zone on ultrasound‐based elastography was represented by an area of increased stiffness and was well demarcated from the nonablated surrounding tissue. The size and shape of the ablated zone on the strain image correlated well with the gross specimen and the magnetic resonance imaging appearance. Strain images obtained from the patient showed results similar to those of the ex vivo experiment and correlated well with the nonenhancing area of ablation on contrast‐enhanced computed tomography. Conclusions. Ultrasound‐based elastography may be a promising tool for displaying the ablation zone created by expandable RFA probes.

Thyroid nodule classification using ultrasound elastography via linear discriminant analysis.

The non-surgical diagnosis of thyroid nodules is currently made via a fine needle aspiration (FNA) biopsy. It is estimated that somewhere between 250,000 and 300,000 thyroid FNA biopsies are performed in the United States annually. However, a large percentage (approximately 70%) of these biopsies turn out to be benign. Since the aggressive FNA management of thyroid nodules is costly, quantitative risk assessment and stratification of a nodules malignancy is of value in triage and more appropriate healthcare resources utilization. In this paper, we introduce a new method for classifying the thyroid nodules based on the ultrasound (US) elastography features. Unlike approaches to assess the stiffness of a thyroid nodule by visually inspecting the pseudo-color pattern in the strain image, we use a classification algorithm to stratify the nodule by using the power spectrum of strain rate waveform extracted from the US elastography image sequence. Pulsation from the carotid artery was used to compress the thyroid nodules. Ultrasound data previously acquired from 98 thyroid nodules were used in this retrospective study to evaluate our classification algorithm. A classifier was developed based on the linear discriminant analysis (LDA) and used to differentiate the thyroid nodules into two types: (I) no FNA (observation-only) and (II) FNA. Using our method, 62 nodules were classified as type I, all of which were benign, while 36 nodules were classified as Type-II, 16 malignant and 20 benign, resulting in a sensitivity of 100% and specificity of 75.6% in detecting malignant thyroid nodules. This indicates that our triage method based on US elastography has the potential to substantially reduce the number of FNA biopsies (63.3%) by detecting benign nodules and managing them via follow-up observations rather than an FNA biopsy.

Utility of the Ultrasound Elastographic Systolic Thyroid Stiffness Index in Reducing Fine-Needle Aspirations

Objective. The purpose of this study was to evaluate whether ultrasound elastography performed by using carotid pulsation as a compression source and generating the systolic thyroid stiffness index (STSI) can be used as a pre–fine‐needle aspiration (FNA) screening tool. Method. Ultrasound data previously acquired from 62 thyroid nodules in 59 patients who underwent a thyroid FNA were used. Pulsation from the carotid artery was used as the compression source, and the strain was calculated offline. A metric called the STSI was computed for each nodule during systole. On the basis of the derived STSI value, thyroid nodules were retrospectively classified into 2 types: I, no FNA (observation only); and II, FNA. Results. The STSI value of malignant nodules (n = 12) was significantly higher than that of benign nodules (n = 39; P < .00002). Using an STSI cutoff value of 10, 31 nodules were classified as type I, all of which were benign, whereas 20 nodules were classified as type II, 12 malignant and 8 benign, with sensitivity of 100% and specificity of 79.4%. This suggests that ultrasound elastography could have screened out 31 type I nodules, reducing the number of FNAs by 60.8%. Conclusion. Thyroid ultrasound elastography has the potential to substantially reduce the number of FNA biopsies by detecting type I benign nodules. Patients with suspicious type II nodules would be referred for an FNA. Future prospective studies are needed to confirm the efficacy of thyroid ultrasound elastography as a triage tool to FNA.