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Biomedical subjects

R S Adler

Publications and source records attributed to R S Adler.

At least 55 records · Page 3Linked to original sources
PubMed1994

Automated segmentation of regions of interest on hand radiographs.

Most radiologists do not use texture information contained in the trabecular patterns of hand radiographs to diagnose erosive changes and demineralization due to systemic inflammatory diseases that affect the skeletal system. However, high-resolution digitization achievable by a laser digitizer now makes it possible to access texture information that may not be perceived visually. We are studying the feasibility of computer-assisted early detection of these processes with particular attention to patients with hyperparathyroidism. In this paper the methods used to extract a region of interest (ROI) for texture analysis are discussed. The techniques include multiresolution sensing, automatic adaptive thresholding, detection of orientation angle, and projection taken perpendicular to the line of least second moment. The methods were tested on a database of 50 pairs of hand radiographs. We segmented the middle and the index fingers with an average success rate of 83% per hand. For the segmented finger strips, we located ROIs on both the middle and the proximal phalanges correctly over 84% of the times. Texture information was collected in the form of a concurrence matrix within the ROI. This study is a prelude to evaluating the correlation between classification based on texture analysis and diagnosis made by experienced radiologists.

Automation↗
PubMed1994

Pulsus tardus: its cause and potential limitations in detection of arterial stenosis.

PURPOSE: To determine, with hydrodynamic experiments, the true cause of pulsus tardus, a Doppler waveform alteration that often occurs distal to an arterial stenosis. MATERIALS AND METHODS: A flow phantom was constructed with a pulsatile pump, interchangeable stenoses of varying degree, and interchangeable poststenotic segments of tubing with various degrees of compliance. With the transstenotic pressure drop held constant for each stenosis, Doppler waveforms were obtained before and after stenosis, while the degree of poststenotic vessel compliance was varied. RESULTS: The degree of pulsus tardus increased as the compliance of the poststenotic segment of vessel increased, independent of the transstenotic pressure drop. CONCLUSION: Poststenotic pulsus tardus is caused by the compliance of the poststenotic vessel wall in conjunction with the stenosis, which produces the tardus effect by damping the high-frequency components of the arterial waveform. This information will allow prediction of conditions that may produce false-positive or false-negative results when the tardus phenomenon is used to predict substantial upstream stenosis.

Blood Flow Velocity↗
PubMed1994

Power Doppler US: a potentially useful alternative to mean frequency-based color Doppler US.

PURPOSE: The authors present a preliminary report to demonstrate a new color Doppler (CD) ultrasonography (US) technique called power Doppler (PD), which displays the total integrated Doppler power in color, and to compare PD with CD imaging, which generally displays an estimate of the mean Doppler frequency shift. MATERIALS AND METHODS: Two standard commercial US scanners that encode the integrated power in the Doppler signal in color were used to demonstrate PD. A standard nonflow-containing US phantom, a normal right kidney, and a torsive and normal contralateral testis were scanned in the power mode. In the phantom and kidney, results with CD and PD were directly compared. RESULTS: PD does not alias, is relatively angle independent, and displays background noise in a way that increases the usable dynamic range of a US scanner. This extended dynamic range should increase machine sensitivity and may demonstrate increased flow in certain circumstances. CONCLUSION: PD is a new CD imaging imaging mode that might be superior to CD in some cases.

Humans↗
PubMed1994

Power versus conventional color Doppler sonography: comparison in the depiction of normal intrarenal vasculature.

PURPOSE: To compare power Doppler sonography with color Doppler sonography in the depiction of normal intrarenal vasculature. MATERIALS AND METHODS: Twenty kidneys in 10 healthy, nonobese subjects were studied with color Doppler and power Doppler sonography at 3.5 MHz and a pulse repetition frequency of 800 Hz. The color gain was increased until "noise" first became perceptible. To standardize comparison, an ultrasound phantom was scanned with both techniques at the mean depth of each kidney. RESULTS: Power Doppler sonography demonstrated a diffuse "blush" of either the entire or almost the entire cortex in 18 of 20 kidneys and in approximately half the cortex of the two other kidneys. Color Doppler sonography did not depict a cortical blush in any kidney. In addition, subjective comparison showed that power Doppler sonography demonstrated the intrarenal vasculature better than color Doppler sonography in all kidneys. CONCLUSION: Power Doppler sonography was superior to color Doppler sonography in the demonstration of normal intrarenal vasculature.

Adolescent↗
PubMed1994

The effect of poststenotic vessel wall compliance upon the pulsus tardus phenomenon.

Recent studies have investigated the detection of significant arterial stenoses through identification of the "pulsus tardus" phenomenon in Doppler waveforms obtained distal to the stenosis. The etiology of this phenomenon, however, has not yet been determined. Using an in vitro model based upon an electrical circuit analogy, the authors had as their objective to determine whether the compliance of the vessel wall immediately distal to a stenosis, in conjunction with the stenosis, is the cause of pulsus tardus. For a constant stenosis, it was found that the degree of pulsus tardus, as quantitated by the acceleration index, increased as the compliance of the poststenotic segment increased. It is concluded that pulsus tardus distal to an arterial stenosis is likely due to the compliance of the normally distensible artery, in conjunction with the stenosis. Pathological conditions that alter the compliance of the poststenotic segment may affect the degree of pulsus tardus, perhaps limiting its usefulness for upstream stenosis detection.

Arterial Occlusive Diseases↗
PubMed1994

Diagnosis of Achilles tendon xanthoma in patients with heterozygous familial hypercholesterolemia: MR vs sonography.

OBJECTIVE: The purpose of this study was twofold: (1) to determine the characteristic MR appearance of the xanthomatous tendons of heterozygous familial hypercholesterolemia and (2) to determine which of two imaging techniques, high-frequency linear-array sonography or MR imaging, is better for detection of xanthomas. SUBJECTS AND METHODS: Sonography and MR imaging were performed to evaluate the Achilles tendons in 10 patients (20 tendons) with heterozygous familial hypercholesterolemia. For sonography, 7.5- (nine patients) and 10.0- (one patient) MHz transducers were used. T1-weighted, proton density-weighted, and T2-weighted MR images were obtained at 0.5 T (four patients) and 1.5 T (six patients), including fat-suppressed (six patients) and water-suppressed (one patient) T1-weighted images at 1.5 T. Tendon abnormalities detected with both techniques were noted, and the results were compared. RESULTS: In all tendons, sonograms showed focal hypoechoic lesions compatible with xanthomas. MR images did not show focal lesions. Instead, all pulse sequences showed a diffuse speckled or reticulated pattern or both on axial images. This speckled or reticulated appearance was more obvious on fat-suppressed T1-weighted images and much less evident on water-suppressed T1-weighted images. Contrast resolution was subjectively better on sonograms than on MR images in all cases. CONCLUSION: The speckled or reticulated appearance is a characteristic, if not pathognomonic, MR feature of xanthomatous tendons and probably is due to edema or inflammation, not intratendinous lipid. However, localized lipid deposits detected on sonograms are more readily quantified than are the lesions seen on MR images. Therefore, we think sonography, rather than MR imaging as performed in our study, is the technique of choice for detecting xanthomas.

Achilles Tendon↗
PubMed1994

Detection of soft-tissue hyperemia: value of power Doppler sonography.

OBJECTIVE: Power Doppler sonography is a new technique that offers extended dynamic range over that provided by conventional color Doppler imaging, thereby facilitating measurement of tissue perfusion. We evaluated the efficacy of power Doppler sonography in depicting soft-tissue hyperemia in musculoskeletal inflammatory conditions. SUBJECTS AND METHODS: Twenty-three patients with predominantly unifocal musculoskeletal symptoms were evaluated with conventional gray-scale imaging and power Doppler sonography. The shoulder was evaluated in 14 patients, the elbow in three, and various other sites in six. For comparison purposes, the contralateral asymptomatic joint or site was examined in 17 cases. Fluid collections were aspirated in seven patients. RESULTS: Soft-tissue hyperemia was seen on power Doppler sonograms at the symptomatic site(s) in 22 of 23 cases studied, with an appearance ranging from frank tissue blush to large, isolated peritendinous/peribursal vessels. Findings associated with hyperemia included rotator cuff tendinitis and/or tear, bursitis, and symptomatic wrist ganglia. Findings on power Doppler sonograms were normal in one patient who had a small, sterile hip joint effusion, and findings on subsequent scintigrams, pelvic radiographs, and CT scans were normal. CONCLUSION: Power Doppler sonography consistently shows hyperperfusion associated with musculoskeletal inflammatory disease. As such, it represents a useful adjunct to gray-scale sonography in these settings, particularly as findings on conventional sonograms in inflammatory conditions can be nonspecific.

Adult↗
PubMed1993

Heterozygous familial hypercholesterolemia: detection of xanthomas in the Achilles tendon with US.

Prospective sonographic evaluation of 44 Achilles tendons in 22 patients with heterozygous familial hypercholesterolemia (FH) was performed with linear-array transducers with high frequency and high resolution. Intratendinous hypoechoic regions believed to represent xanthomas, ranging from single hypoechoic nodules to diffusely enlarged tendons that were heterogeneously hypoechoic, were seen in 40 of the 44 tendons (91%) and 21 of the 22 patients (95%). In addition, focal xanthomas were seen in two of three patients whose Achilles tendons were either normal or questionably abnormal at palpation. The direct visualization of xanthomas in most of these patients contrasts with findings from previously published studies, in which sonographically detected involvement was based on secondary tendon enlargement alone. The improved sonographic visualization of tendon xanthomas in FH, rather than the secondary tendon enlargement caused by them, therefore, suggests a new role for ultrasound in the early diagnosis and follow-up of these cases.

Achilles Tendon↗
PubMed1992

Usefulness of an acoustic edge artifact in assessment of the Ilizarov corticotomy interval.

Thirty-three ultrasound examinations of the corticotomy interval of patients undergoing Ilizarov procedures were retrospectively evaluated for the presence or absence of an acoustic edge artifact. This artifact, consisting of a fine anechoic band, has been previously described in phantom models and is presumed to be due to phase cancellation effects. We demonstrated this artifact in 8 of 33 examinations. The artifact proved helpful in identifying the location of the corticotomy margin, even when this margin was obscured by the presence of developing periosteal new bone. Attention to technical factors is, however, important. We believe that this artifact may have a useful role in the routine monitoring of the Ilizarov patient.

Adolescent↗
PubMed1992

Case report 725. Posterior displacement of proximal end of the right radius and capitulum with supracondylar fracture causing a displaced fracture rather than a fracture dislocation.

An 11-month-old boy with a swollen, painful right elbow demonstrated a supracondylar fracture on plain film radiographic studies. Sonography was subsequently performed to exclude dislocation of the elbow and demonstrated the supracondylar fracture as well as a normal relationship of the capitulum and radius, signifying a displaced fracture without associated dislocation. A bone dislocation would generally require dosed reduction alone, whereas distal humeral epiphyseal separation usually requires open reduction or percutaneous (pin) fixation. This case demonstrates the utility of ultrasound in the evaluation of physeal disruption and dislocation in the elbow prior to ossification of the secondary centers of ossification.

Diagnosis, Differential↗
PubMed1992

Quantitative assessment of cartilage surface roughness in osteoarthritis using high frequency ultrasound.

Osteoarthritis (OA) is a common disease which affects nearly 50% of people over age 60. Histologic evaluation suggests that fibrillations approximately 20-150 microns are among the earliest changes in the articular cartilage. We propose a technique to quantify these surface fibrillatory changes in osteoarthritic articular cartilage by considering the angular distribution of the envelope-detected backscattered pressure field from an incident 30-MHz focused transducer. The angular distribution of the scattered acoustic field from an inosonifying source will directly relate to the distribution of surface fibrillatory changes. Data are presented for three different grades (400, 500 and 600 grit) of commercially available emory paper and three samples of osteoarthritic femoral head articular cartilage, which were visually assessed as having smooth, intermediate and rough surfaces, respectively. Our preliminary results indicate a probable monotonic relationship between articular cartilage roughening and the degree of broadening in the angle-dependent pressure amplitude. When applied to the emory paper, the technique indicates sensitivity to differences as small as approximately 5-10 microns in mean roughness. This procedure may provide an extremely sensitive and reproducible means of quantifying and following the cartilage changes observed in early osteoarthritis.

Cartilage, Articular↗
PubMed1992

Laminar submerged jets by color Doppler ultrasound. A model of the ureteral jet phenomenon.

RATIONALE AND OBJECTIVES: The authors developed and tested a technique to noninvasively measure ureterovesical junction (UVJ) pressure gradients. Such a technique could be used to evaluate ureteral reflux and obstruction. METHODS: Color Doppler ultrasound measurements of an in vitro model of the ureteral jet were performed. RESULTS: The authors show that the orificial rate of momentum transfer of the ureteral jet (from which the intraluminal pressure in the ureter can be calculated) can be determined to within 45% to 94% of its true value depending primarily on the flow sensitivity of the color flow imager. Marked improvement in the momentum calculation (> 80%) is achieved when a low-flow sensitivity is used. CONCLUSION: Such noninvasive measurements could replace more invasive techniques (eg, the Whitaker test or cystoscopy with or without ureteral cannulation), which seriously perturb the system of interest.

Humans↗
PubMed1991

Phase cancellation: a cause of acoustical shadowing at the edges of curved surfaces in B-mode ultrasound images.

Acoustical shadowing occurring at the edges of curved objects is one of the most frequently observed artifacts in ultrasound imaging. This artifact has been generally ascribed to refraction and reflection effects at the boundary between the curved object and the surrounding tissues. However, the shadowing that would be produced by pure refraction and reflection may not correspond in all circumstances to what is most often seen clinically, i.e., a sharp, discrete shadow projecting down from the edge. We used a tissue-mimicking contrast detail phantom, speed of sound (SOS) 1477 m/s, containing cylindrically shaped wells to investigate the origin of these shadows. Using solutions of relatively high SOS (20% ethylene glycol), approximately equivalent SOS (distilled water), and low SOS (70% isopropyl alcohol), the phantom was scanned with the scanhead face oriented perpendicular to and parallel to the central axes of the cylinders. Shadowing could be produced in both cases when there was a SOS difference between the contents of the cylinders and the phantom. When scanning perpendicular to the cylinders, refraction and reflection effects could have contributed to any shadowing produced, but when the scan planes were oriented parallel to the central axes of the cylinders, neither refraction nor reflection could be occurring to a significant degree. The shadowing produced in these circumstances could be better explained by a phenomenon well known in transmission ultrasonography called phase cancellation. Phase cancellation would produce shadowing independent of scan plane orientation, and could contribute to the shadowing generated in clinical imaging.

Acoustics↗
PubMed1991

Clean and dirty shadowing at US: a reappraisal.

Clean and dirty shadowing are common phenomena in ultrasound (US) imaging. Clean shadowing is thought to be produced by sound-absorbing materials (ie, stones), and dirty shadowing is thought to be produced by sound-reflecting materials (ie, abdominal gas), but these properties are not consistent. To evaluate the characteristics of shadows behind different objects at US, the authors scanned two renal stones and a bovine femur (each of which had part of its surface artificially smoothed or roughened) and a tissue-mimicking phantom comprising air-containing cylinders of different radii of curvature. The rougher and/or smaller the radius of curvature of the surface insonified by the sound beam, the cleaner was the shadow, independent of the composition of the underlying reflecting medium. Clean and dirty shadowing were primarily related to the properties of the surface of the shadowing object and provided little information about the structural nature of the object.

Animals↗