Sonographic discrimination between benign and malignant breast lesions with use of disparity processing.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate whether a digital processing technique called disparity processing (DP) can improve the differentiation between benign and malignant breast masses at ultrasound (US) and, thus, reduce the number of benign lesions being sampled for biopsy. MATERIALS AND METHODS: During an US examination, a sonographer slightly varies the pressure of the probe on the breast surface. DP can be used to evaluate pairs of B scans that represent the different parts of this compression cycle. The apparent displacement of the tissue is measured with DP, and a new image, called a correlation map, is constructed. This new image illustrates the similarity between the speckle patterns around each point. The authors evaluated 25 solid lesions with DP. Results were compared with those from (a) histologic examination of specimens obtained with core or surgical biopsy or (b) cytologic examination of specimens obtained with fine-needle aspiration. RESULTS: All 25 lesions were correctly diagnosed with DP. There were no false-positive or false-negative findings. All malignancies demonstrated a relatively low-brightness halo around the lesion perimeter with evidence of discontinuity. All benign lesions were associated with relatively high-brightness, continuous halos. CONCLUSION: The results suggest that DP can help differentiate benign from malignant masses.

Occult scapholunate ganglion: a cause of dorsal radial wrist pain.

There are multiple causes for chronic dorsal wrist pain over the scapholunate ligament, including occult dorsal carpal ganglion cyst, scaphoid impaction syndrome, dorsal carpal capsulitis, distal posterior interosseous nerve syndrome, and dynamic scapholunate ligament instability. Patients with such pain often have normal x-rays. A retrospective study of 21 patients undergoing surgical exploration for chronic dorsal radial wrist pain who had no palpable cyst and normal x-rays revealed that 18 of the patients had occult scapholunate ganglion cysts or myxomatous degeneration within the scapholunate ligament. All had failed long-term conservative management. Surgery involved an approach through Langer's lines, resection of a large triangular portion of the capsule between the dorsal intercarpal and radiotriquetral ligaments, and tangential debridement of the area of myxoid degeneration proximal to the distal 2 to 3 mm of dorsal scapholunate interosseous ligament. None of the patients had scapholunate instability or scaphoid impacting syndrome. Of the 18 patients with histologically confirmed myxomatous changes in the scapholunate ligament, 16 had an excellent outcome as defined by rigorous criteria; 1 had a good outcome. There was 1 patient with a poor result. A compelling argument is made for surgical exploration of the scapholunate joint in patients with persistent dorsal radial wrist pain and scapholunate point tenderness.

Disparity mapping applied to sonography of the breast: technical note.

A two-dimensional sonoelastographic technique called "disparity mapping" was applied to breast sonographic examinations in eight patients to test discrimination between benign and malignant lesions. With probe compression, pairs of gray-scale sonographic scans were obtained about 1 second apart. The disparity mapping procedure calculated the apparent displacement of the speckle pattern about each point in the image and presented that information in the form of a disparity map. Findings were consistent with a firm lesion in two of the three cancers, were indistinguishable from normal tissue in all three fibroadenomas, were indistinguishable from normal findings in one cyst, and showed no disparity in one cyst because it had few internal echoes.

Ultrasparse, ultrawideband arrays.

This paper investigates the properties of highly thinned ultrawideband (UWB) arrays. The design aim is high resolution and very low side radiation levels (SL). One- and two-dimensional ultrasparse UWB arrays can be designed to achieve both. The minimum available pulse-echo SL is shown to approach N(-4) where N is the number of elements in the transmit and receive arrays. Periodic thinning is shown to be superior to random thinning, and amplitude taper is shown to raise the SL. Two-dimensional curvilinear deployment of elements are shown to outperform rectilinear designs, and different transmit and receive arrays in pulse-echo systems are shown to outperform systems that use the same array for transmit and receive. Very low SL is achievable in an ultrasparse UWB system with so few elements that echo signal-to-noise ratio (SNR) rather than SL becomes the constraint on the minimum number of elements required by the system for the array to be useful for imaging. For example, in ultrasonic pulse-echo breast imaging, SL approximately -70 dB is desired to distinguish small cysts from tumors. A 2-D randomly thinned array requires about 10,000 elements. A 2-D ultrasparse UWB periodic array requires less than 100 to satisfy SL, a reduction of 100:1, but provides insufficient SNR. A 500-element, 7.5 MHz array operating with 4 cm penetration depth satisfies both. Experimental results demonstrate the theory.

Correlation distance measurements of the female breast.

Ultrasonic waves propagating through soft tissue experience wavefront distortion. Adaptive wavefront compensation algorithms attempt to correct such distortion. A valuable design parameter is the isoplanatic patch size of the imaging medium. Its lateral extent is the FWHM of the correlation function. The range extent is defined similarly. The significance of the isoplanatic patch is that a new wavefront correction vector must be obtained whenever the ultrasound beam is moved a patch length. This paper reports measurements of wavefront correlation functions as well as statistics of the lateral correlation distance rho d (half the FWHM) within the female breast obtained from a population of 22 women (44 breasts) and measured at 3 and 4 MHz with a large acoustic aperture (9.6 cm). A set of complex wavefronts radiated from single pointlike sources was measured from the opposing side of the breast. The propagation distance was 12 cm. rho d is the distance between two sources at which the correlation between their wavefronts drops to 0.5. The mean value at 3 MHz was found to be less than 1.5 mm for the premenopausal dense breast, 2.5 mm for the premenopausal fatty breast, and 2.0 mm for the postmenopausal breast. The mean value dropped by a factor of 2 at 4 MHz for a group consisting of premenopausal fatty and postmenopausal breasts.

Clinical anatomy of the wrist and elbow.

For the orthopedist, the design and execution of surgical procedures requires a thorough understanding of anatomy. The goal of this article is to provide an overview of the pertinent surgical anatomy of the wrist and elbow. Operative techniques improve with advancing technologic breakthroughs and greater understanding of anatomy. Today's orthopedic surgeon is required to remain current on this expanding information base; this information will allow for a better understanding of common and overuse injuries of the wrist, forearm, and elbow.

Measurement and correction of ultrasonic pulse distortion produced by the human breast.

Ultrasonic wavefront distortion produced by transmission through breast tissue specimens was measured in a two-dimensional aperture. Differences in arrival time and energy level between the measured waveforms and references that account for geometric delay and spreading were calculated. Also calculated was a waveform similarity factor that is decreased from 1.0 by changes in waveform shape. For nine different breast specimens, the arrival time fluctuations had an average (+/- s.d.) rms value of 66.8 (+/- 12.6) ns and an associated correlation length of 4.3 (+/- 1.1) mm, while the energy level fluctuations had an average rms value of 5.0 (+/- 0.5) dB and a correlation length of 3.4 (+/- 0.8) mm. The corresponding waveform similarity factor was 0.910 (+/- 0.023). The effect of the wavefront distortion on focusing and the ability of time-shift compensation to remove the distortion were evaluated by comparing parameters such as the -30-dB effective radius, the -10-dB peripheral energy ratio, and the level at which the effective radius departs from an ideal by 10% for the focus obtained without compensation, with time-shift estimation and compensation in the aperture, and with time-shift estimation and compensation performed after backpropagation. For the nine specimens, the average -10-dB peripheral energy ratio of the focused beams fell from 3.82 (+/- 1.83) for the uncompensated data to 0.96 (+/- 0.18) with time-shift compensation in the aperture and to 0.63 (+/- 0.07) with time-shift compensation after backpropagation. The average -30-dB effective radius and average 10% deviation level were 4.5 (+/- 0.8) mm and -19.2 (+/- 3.5) dB, respectively, for compensation in the aperture and 3.2 (+/- 0.7) mm and -22.8 (+/- 2.8) dB, respectively, for compensation after backpropagation. The corresponding radius for the uncompensated data was not meaningful because the dynamic range of the focus was generally less than 30 dB in the elevation direction, while the average 10% deviation level for the uncompensated data was -4.9 (+/- 4.1) dB. The results indicate that wavefront distortion produced by breast significantly degrades ultrasonic focus in the low MHz frequency range and that much of this degradation can be eliminated using wavefront backpropagation and time-shift compensation.

Percutaneous Kirschner wire fixation through the snuff box: an anatomic study.

We undertook this study to better define the anatomy of the radial aspect of the wrist and to establish a zone of safety for the placement of Kirschner wires, cannulated screws, and arthroscopes within the anatomic snuff box. Twenty fresh frozen cadaver upper extremities underwent placement of three percutaneous Kirschner wires under fluoroscopic guidance through the anatomic snuff box. In each extremity, one Kirschner wire was placed into the radial styloid, one across the scaphocapitate joint, and one across the scapholunate joint. A safe zone of mean 0.68 sq cm was found deep to the subcutaneous tissue bordered by the radial styloid, the first dorsal compartment, the radial artery, and the superficial radial nerve. Kirschner wires placed distal, dorsal, or palmar to the borders of the safe zone were at great risk of injuring neurovascular structures. To minimize the risk of injury to adjacent structures, we advise a limited incision in the safe zone with blunt dissection to the wrist capsule. Though improved anatomic understanding, we established a new location for the arthroscopic 1,2 portal within the snuff box.

Wavefront amplitude distribution in the female breast.

Ultrasound measurements of a large population of wavefronts transmitted through female breasts at 3 and 4 MHz show that the wavefront amplitude distribution is close to Rayleigh. This finding is consistent with a fully developed scatter field, implying that the scatter energy removed from the coherent incident beam dominates the wavefront. The wavefront received from an inhomogeneous medium is the superposition of an incident wave plus a scattered wave. If the scattered field is weak, the received field is dominated by the incident field and the wavefront amplitude distribution is Rician. If the scattered field is strong, the received field is primarily the scattered field and the wavefront amplitude distribution is Rayleigh. If, in addition to scattering, refraction between bodies of different refractive indexes occurs, the total net effect on the wavefront amplitude distribution is the same as for strong scattering. This is what we have observed in the highly refractive female breast. This result has implications for the design of high lateral-resolution echo scanners that will incorporate adaptive phase deaberration algorithms. The published algorithms were developed for weak scattering and therefore may not be powerful enough. Alternatives have to be found to deaberrate the severe wavefront distortion in the breast.

Evaluation of limb compartment with suspected increased interstitial pressure. A noninvasive method for determining quantitative hardness.

Six compartments in four dogs and three compartments in three anatomic specimen limbs were injected with plasma, and the intracompartmental interstitial pressure and hardness of the compartments were measured. Six patients suspected of having compartment syndromes were also studied. Of the compartments evaluated in the dog and anatomic specimen limbs, the average correlation coefficient between measurements with the two methods was 0.95 (range, 0.87 to 0.99). In six patients suspected of having compartment syndromes, the ratios of quantitative hardness of the injured to uninjured limbs closely matched the intracompartmental interstitial pressure measurement ratios (correlation coefficient, 0.95). All correlation coefficients were significant (F test, p < 0.05). There was a close correlation between the direct measurement of intracompartmental interstitial pressure with the wick catheter and quantitative hardness in compartment syndrome models in dog and anatomic specimen limbs, and in patients suspected of having compartment syndromes. The determination of surface hardness of limb compartments, which appears accurate and reproducible, offers the advantages of being noninvasive and well suited for longer-term assessments of intracompartmental interstitial pressure.

Wavefront amplitude distortion and image sidelobe levels. I. Theory and computer simulations.

The quality of an imaging system is degraded by propagation anomalies that distort wavefronts propagating through the medium. Adaptive phase-deaberration algorithms compensate for phase errors in the wavefront. The algorithms suffer, however, when the wavefront is also significantly distorted. A theory which shows that the rise of image background level, which is the average sidelobe floor (ASF), in a single point-like source image is proportional to the amplitude distortion of the wavefront and inversely proportional to the effective number of array elements is derived. From the theory, the tolerance to the amplitude distortion, after the phasefront has been corrected by a deaberration algorithm, can be calculated based on the design requirement of the sidelobe floor for a given array. Computer simulations show good agreement with the theory.

Wavefront amplitude distortion and image sidelobe levels. II. In vivo experiments.

For part I, see ibid., vol.40, no.6, p.747-753 (1993). In vivo measurements of the rise of the sidelobe level in a single-source image obtained through the female breast as a function of the distortion of the wavefront amplitude are described. The measured sidelobe levels are the average sidelobe floor (ASF) and the peak sidelobe level (PSL). The ASF is shown to be proportional to the variance of the modulus of the wavefront normalized to the square of its mean value, with a proportionality constant close to the value predicted by theory. The PSL similarly increases linearly. The average ratio of PSL to ASF is 5 (7 dB).

A discussion of two wavefront aberration correction procedures.

This review paper discusses the basic properties of two adaptive signal processing procedures for dealing with weak scattering in a phased array transducer system. A fundamental improvement in the lateral resolution of ultrasonic echo scanners will result if the weight vector of a large phased array transducer can be modified to account for distortion in the propagation medium. Lateral resolution in most tissue is limited to a few mm by wavefront-distortion-induced sound-speed variations. One important wavefront-distortion source is scattering from local speed variations within large and reasonably homogeneous tissue beds such as the liver. Scattering disperses some energy from the beam and perturbs the wavefront, thereby distorting the image and limiting the resolution to the scale of the distortion. Often, such scattering is weak, meaning that most of the energy in the beam is unscattered. The total field at the receiving transducer is the vector sum of the unscattered and scattered fields. In weak scattering the unscattered field is dominant and the resultant field can be treated as the unscattered field plus a perturbation. The net effect is primarily a distorted phasefront, while the amplitude or modulus of the wavefront remains reasonably intact. Refraction and strong scattering effect the wavefront more severely and are less responsive to these algorithms.

Large-transducer measurements of wavefront distortion in the female breast.

Ultrasonic waves propagating through soft tissue experience wavefront distortion. Refraction occurs at boundaries between tissue beds having different sound speeds; scattering occurs within a tissue bed, caused by local impedance variations. This paper describes measurements of wavefront distortion in the human female breast that indicate that refraction is the dominant distortion mechanism when the ultrasonic phased array is very large. The determination that refraction dominates the wavefront distortion is based upon studies of multiple image artifacts that result from a single source radiated through in vivo breasts and breast phantoms. The receiving apertures used were 4.65 and 9.6 cm. Such image artifacts are repeatedly observed in the 10 young subjects reported in this paper, and also in older subjects. An understanding of the in vivo observations is obtained by phantom studies.

Digital beamforming in ultrasound.

The effects on array gain and sidelobe level of a practical digital beamforming (DBF) processor under the wideband conditions typical of ultrasound is discussed. It is concluded that a relatively simple design that replaces each analog delay line with a tapped, digital shift register (DSR) and a digital phase shift operation adjusted for midband will provide the desired performance, provided that the sampling rate of the signal at the input to the DSR is 4 to 10 times the bandwidth. More realistically, when nonidealized passbands are taken into account and the typical condition whereby the transducer frequency is about twice the bandwidth is considered, the rule of thumb for the sampling rate is that it must be 4 to 10 times the transducer frequency.

Epithelioid sarcoma in the upper extremity.

Eighteen patients who had epithelioid sarcoma in the upper extremity were divided into two groups on the basis of treatment: marginal resection of the tumor or wide or radical resection of the tumor. Historical, demographic, histological, and staging data were recorded and were correlated with the type of treatment and the outcome. Marginal resection (excision through the reactive zone or pseudocapsule surrounding the tumor, with confirmation of a negative margin by a pathologist), with or without adjuvant therapy, led to a dismal outcome in patients who had been treated in this manner initially or secondarily (fifteen failures after seventeen procedures). Disease-free survival at ten years was significantly improved when wide resection (intracompartmental en bloc excision with a cuff of normal tissue of more than three centimeters) or radical resection was either the initial or the secondary treatment; success then was noted in nine of thirteen operations. Of twelve patients in whom a marginal resection had been done initially, three had had a recurrence, three had had a metastasis, and five had died, at a mean follow-up of seven years (range, twenty-seven months to sixteen years). At a mean follow-up of six years (range, two to fifteen years), only one of five patients in whom a secondary lesion had been treated with marginal resection was free of disease. Of the six patients who had been treated with wide or radical resection initially, none had died, one had had a recurrence, and one had had a metastasis, at a mean follow-up of seven years (range, twenty-two months to fourteen years).(ABSTRACT TRUNCATED AT 250 WORDS)