Christopher R.B. Merritt

Elastography : Imaging the Elastic Properties of Soft Tissues with Ultrasound

Elastography is a method that can ultimately generate several new kinds of images, called elastograms. As such, all the properties of elastograms are different from the familiar properties of sonograms. While sonograms convey information related to the local acoustic backscatter energy from tissue components, elastograms relate to its local strains, Youngs moduli or Poissons ratios. In general, these elasticity parameters are not directly correlated with sonographic parameters, i.e. elastography conveys new information about internal tissue structure and behavior under load that is not otherwise obtainable. In this paper we summarize our work in the field of elastography over the past decade. We present some relevant background material from the field of biomechanics. We then discuss the basic principles and limitations that are involved in the production of elastograms of biological tissues. Results from biological tissues in vitro and in vivo are shown to demonstrate this point. We conclude with some observations regarding the potential of elastography for medical diagnosis.

ULTRASOUND AS A COMPLEMENT TO MAMMOGRAPHY AND BREAST EXAMINATION TO CHARACTERIZE BREAST MASSES

This study was designed to determine if complementary ultrasound (US) imaging and Doppler could decrease the number of biopsies for benign masses. A total of 761 breast masses were sequentially scored on a level of suspicion (LOS) of 1-5, where 1 represented low, and 5 was a high suspicion of malignancy, for mammography, US, and color flow with pulse Doppler (DUS). After biopsy, the results were analyzed using 2 x 2 contingency tables and ROC analysis, for mammography alone and in combination with US and DUS. The addition of US increased the specificity from 51.4% to 66.4% at a prevalence of 31.3% malignancy. ROC analysis showed that the addition of US significantly improved the performance over mammography alone in women < 55 years old (p = 0.049); > 55 years old (p = 0.029); masses < 1 cm (p = 0.016) and masses > 1 cm (p = 0.016). These results show that the addition of US to mammography alone could substantially reduce the number of breast biopsies for benign disease.

American Institute of Ultrasound in Medicine consensus report on potential bioeffects of diagnostic ultrasound: Executive summary

The continued examination of potential biological effects of ultrasound and their relationship to clinical practice is a key element in evaluating the safety of diagnostic ultrasound. Periodically, the American Institute of Ultrasound in Medicine (AIUM) sponsors conferences bringing experts together to examine the literature on ultrasound bioeffects and to develop conclusions and recommendations related to diagnostic ultrasound. The most recent effort included the examination of effects whose origins were thermal or nonthermal, with separate evaluations for potential effects related to fetal ultrasound. In addition, potential effects due to the introduction of ultrasound contrast agents were summarized. This information can be used to assess risks in comparison to the benefits of diagnostic ultrasound. The conclusions and recommendations are organized into 5 broad categories, with a comprehensive background and evaluation of each topic provided in the corresponding articles in this issue. The following summary is not meant as a substitute for the detailed examination of issues presented in each of the articles but rather as a means to facilitate further study of this consensus report and implementation of its recommendations. The conclusions and recommendations are the result of several rounds of deliberations at the consensus conference, subsequent review by the Bioeffects Committee of the AIUM, and approval by the AIUM Board of Governors.

The Risk of Exposure to Diagnostic Ultrasound in Postnatal Subjects Thermal Effects

This review evaluates the thermal mechanism for ultrasound‐induced biological effects in postnatal subjects. The focus is the evaluation of damage versus temperature increase. A view of ultrasound‐induced temperature increase is presented, based on thermodynamic Arrhenius analyses. The hyperthermia and other literature revealed data that allowed for an estimate of a temperature increase threshold of tissue damage for very short exposure times. This evaluation yielded an exposure time extension of the 1997 American Institute of Ultrasound in Medicine Conclusions Regarding Heat statement (American Institute of Ultrasound in Medicine, Laurel, MD) to 0.1 second for nonfetal tissue, where, at this exposure time, the temperature increase threshold of tissue damage was estimated to be about 18°C. The output display standard was also evaluated for soft tissue and bone cases, and it was concluded that the current thermal indices could be improved to reduce the deviations and scatter of computed maximum temperature rises.

Acoustic output upper limits proposition: Should upper limits be retained?

From the Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois (W.D.O.); Philips Medical Systems– Ultrasound, Bothell, Washington (J.G.A.); Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland (M.E.St., G.R.H.); Sonic Tech, Inc, Fort Washington, Pennsylvania (M.E.Sc.); Department of Obstetrics and Gynecology, University of Cincinnati College of Medicine, Cincinnati, Ohio (T.A.S.); Thomas Jefferson University Hospital, Philadelphia, Pennsylvania (C.R.B.M.); Medical Physics Department, Royal United Hospital, Bath, England (F.A.D.); and Peripheral Vascular Diagnostic Center, William Beaumont Hospital, Royal Oak, Michigan (P.J.B.). Address correspondence to William D. O’Brien, Jr, PhD, Bioacoustics Research Laboratory, Department of Electrical and Computer Engineering, University of Illinois, 405 N Mathews, Urbana, IL 61801. Abbreviations AIUM, American Institute of Ultrasound in Medicine; ALARA, as low as reasonably achievable; FDA, Food and Drug Administration; NEMA, National Electrical Manufacturers Association; ODS, output display standard t the American Institute of Ultrasound in Medicine (AIUM) 2002 Annual Convention in Nashville, Tennessee, a point/counterpoint categorical course was presented on the topic of acoustic output upper limits. The course organizers were William D. O’Brien, Jr, PhD, John G. Abbott, PhD, and Mel E. Stratmeyer, PhD. The published course objective was as follows:

AIUM Standard for the Performance of an Ultrasound Examination of the Abdomen or Retroperitoneum

The American Institute of Ultrasound in Medicine (AIUM) is an educational, scientific, and professional society concerned with the advancement of the art and science of ultrasound in medicine and research. To promote this mission, the AIUM is pleased to publish, in conjunction with the American College of Radiology (ACR), the updated Standard for Performance of an Ultrasound Examination of the Abdomen or Retroperitoneum. We are indebted to the many volunteers who contributed their time, knowledge, and energy to bringing this document to completion.

Unusual “To-and-Fro” Doppler Spectral Waveform in Lymph Node Metastasis

We present a case of a lymph node metastasis in which duplex Doppler imaging showed diastolic flow reversal. Traditionally, this vascular flow pattern is not expected in tumors; therefore, our case shows an unusual Doppler finding, which underscores the complex, multivariable nature of tumor vascularity.