Search PubMed⌕ Search

Biomedical subjects

J M Rubin

Publications and source records attributed to J M Rubin.

At least 73 records · Page 4Linked to original sources
PubMed1995

Prostate cancer: diagnosis with color Doppler sonography with histologic correlation of each biopsy site.

PURPOSE: To correlate the findings at prostate color Doppler sonography (CDS) with those of site-specific transrectal core biopsy. MATERIALS AND METHODS: Forty-three patients underwent prostate transrectal ultrasonography (US) and biopsy. CDS was performed at all biopsy sites before US-guided core biopsy. Vascularity at CDS was prospectively graded on a scale of 0-2 (0 = no visible peripheral zone [PZ] flow, 2 = markedly increased PZ vascularity). CDS results were correlated with histologic findings from 220 separate biopsy sites that included 27 focal lesions. RESULTS: Of 34 grade 2 biopsy sites, 21 revealed carcinoma, eight revealed prostatitis, and five were negative. CDS depicted at least one focus of carcinoma in seven patients with no gray-scale abnormality. CDS had a sensitivity of 49%, specificity of 93%, and positive predictive value of 62%. CONCLUSION: Focal PZ hypervascularity at CDS is associated with an increased likelihood of prostate cancer or inflammation at biopsy, often without a focal gray-scale abnormality. CDS may help identify an appropriate site for biopsy. A negative CDS scan, however, should not preclude biopsy, as CDS has a limited sensitivity in the detection of all sites of cancer.

Aged↗
PubMed1995

Hepatic artery resistance changes in portal vein thrombosis.

PURPOSE: To determine if portal vein thrombosis (PVT) is associated with changes in the hepatic artery resistive index (RI) at Doppler ultrasonography (US). MATERIALS AND METHODS: In 35 patients with findings suspicious for PVT, prospective hepatic artery RIs were obtained before angiographic proof of portal vein status. RIs were also obtained from 27 age-matched patients with liver disease (without PVT) and from eight patients with PVT (without occlusion). RESULTS: Twenty-seven of the 35 patients had proved PVT and a significantly lower (P < .01) mean hepatic artery RI than did patients in any other group studied. Twelve of these 27 patients had RI values of .50 or less, while none of the patients in any other group studied had an RI value this low (specificity, 100%). CONCLUSION: A reduction in hepatic artery RI accompanies PVT and may be a helpful secondary sign to determine this venous abnormality.

Adolescent↗
PubMed1995

Hepatic artery resistance before and after standard meal in subjects with diseased and healthy livers.

PURPOSE: To assess fasting and postprandial resistive index (RI) in subjects with healthy and diseased livers. MATERIALS AND METHODS: Subjects with healthy (n = 10) and diseased (n = 33) livers underwent fasting and postprandial Doppler ultrasonography of the hepatic artery. Findings were compared with parameters for liver disease and Child class A-C and Child score of 5-15. RESULTS: The mean postprandial RI increase in healthy subjects was 42% (all, > or = 20%) and in patients with liver disease was 7% (six, > or = 20%). Patients with class A disease (n = 12) had a significantly greater increase in post-prandial RI (13%) than those with class B or C disease (3%) (P < .05). All patients with class C disease (n = 9) had an increased postprandial RI of less than 10%. The 13 patients with at least 10% increase in postprandial RI had less severe liver disease (Child score, 6.1 +/- 1.3 [standard deviation]) than the 20 patients with less than 10% increase (Child score, 8.4 +/- 1.7) (P < .01). CONCLUSION: A normal marked increase in postprandial RI is generally not seen in patients with severe liver disease.

Adult↗
PubMed1995

Fractional moving blood volume: estimation with power Doppler US.

PURPOSE: To estimate the fraction of moving blood in tissue with power Doppler ultrasound (US). MATERIALS AND METHODS: Power Doppler US measurements of moving scatterers in a flow tube were made as a function of successive dilutions of the perfusate. Measurements were normalized relative to the maximum Doppler power in the center of the flow tube at the highest concentration and were used to calculate the fractional dilution of the perfusate for each run with each dilution used to represent increasing amounts of non-moving soft tissue in the sample volume. The technique was also applied to two clinical examples. RESULTS: Successive dilutions of the perfusate in the flow experiment showed a monotonic, linear decrease in the Doppler power as a function of dilution. CONCLUSION: The power Doppler US technique has the potential to more accurately estimate alterations in blood flow and has the advantage of being a continuous parameter that can be depth normalized.

Blood Circulation↗
PubMed1994

Quantitative assessment of surface roughness using backscattered ultrasound: the effects of finite surface curvature.

We have previously described a technique to quantify surface fibrillatory changes in osteoarthritic articular cartilage. In that study, the angular distribution of the scattered acoustic field from an insonifying source directly related to the distribution of surface fibrillatory changes. In the current study, we demonstrate a more sensitive method to quantify surface roughness, the effect of global surface curvature in estimating surface roughness and the utility of using focused transducers in circumventing this potential problem for in vivo work. Phantoms composed of acrylic rods with and without sandpaper grit (about 15 to 72 microns, mean particle size) applied to the surface were scanned. A more robust angular scattering technique to measure the angle dependent data was employed, in which the integrated squared pressure amplitude over a finite time window (mean power) was measured as a function of incident acoustic angle for varying surface roughnesses and radii of curvature. We show that the potential dynamic range for making roughness discriminations diminishes with decreasing radius of curvature of the acrylic rod phantoms using an unfocused transducer. This effect is minimized with use of a focused transducer. Roughness effects are most evident at sufficiently large angles where incoherent scattering dominates. We conclude that the roughness of cylindrically curved surfaces can be quantitatively assessed using a focused ultrasound beam at sufficiently large incident angles, given that the focal spot size is sufficiently smaller than the radius of curvature of the surface.

Cartilage, Articular↗
PubMed1994

Effect of furosemide and intravenous normal saline fluid load upon the renal resistive index in nonobstructed kidneys in children.

Recent literature has shown that relative to baseline the renal resistive index remains unchanged in nonobstructed kidneys and increases in obstructed kidneys after administration of furosemide. To our knowledge the effect upon the renal resistive index of furosemide administered in conjunction with intravenous normal saline fluid load has not been reported. We evaluated the renal resistive index in 13 nonobstructed kidneys in 8 children 6 to 18 years old before and after furosemide and intravenous normal saline fluid load. The mean resistive index decreased from baseline (mean decrease was 0.06 +/- 0.06 standard deviation), with the observation of a resistive index decrease significant to p < 0.005). It appears likely that the combination of an intravenous normal saline fluid load and furosemide caused the resistive index decrease, since a decrease was not observed with furosemide alone; however, these results cannot exclude the possibility that the resistive index decrease was due to the intravenous normal saline fluid load alone. Nonetheless, these data are important since they may provide the foundation for the development of a pharmacologically challenged Doppler sonographic examination using furosemide and intravenous normal saline fluid load to evaluate better potentially obstructed kidneys.

Adolescent↗
PubMed1994

The use of ultrasound mean acoustic attenuation to quantify bone formation during distraction osteogenesis performed by the Ilizarov method. Preliminary results in five dogs.

RATIONALE AND OBJECTIVES: Management of distraction during Ilizarov limb lengthening remains primarily clinical and empirical. Estimates of tissue acoustic attenuation were evaluated for their ability to quantify bone formation within the distraction gap. METHODS: Five dogs had tibias lengthened by the method of Ilizarov. Mean acoustic attenuation measurements at multiple positions across the distraction gap were compared with corresponding x-ray computed tomography attenuation measurements. RESULTS: Computed tomography and ultrasound attenuation displayed similar quantitative behavior across the gap. Linear correlation between them ranged from R2 = .878 to R2 = .131. Fibrous interzone width estimates based on computed tomography and ultrasound attenuation measurements were correlated, based on our preliminary data with R2 = .519. These estimates are independent of the width of distraction. CONCLUSIONS: Ultrasound parallels computed tomography as a measure of bone formation within the distraction gap. Future studies are needed to improve acoustic attenuation data acquisition techniques and to evaluate their potential as a tool for optimizing early distraction rates in patients at risk for rate-related complications.

Acoustics↗
PubMed1994

Spectral Doppler US.

Doppler ultrasonography (US) is used to measure blood velocity by means of the Doppler frequency shift of the echoes received from red blood cells. The two most common types of equipment for measuring Doppler shifts are continuous-wave (CW) Doppler and pulsed, or range-gated, Doppler. A CW Doppler transducer has a separate receiver and transmitter because it transmits continuously. Because of its continuous transmission, there is no depth resolution. CW Doppler systems, however, have high sensitivity and are not susceptible to aliasing. Pulsed Doppler systems transmit a pulse and measure the Doppler shift of the received echo signals from an operator-selectable depth interval (range gate). The ultrasound Doppler shifts occur in the audible range and are displayed in spectral form, with Doppler frequency shifts on the vertical axis and time on the horizontal axis so that the time-history of the blood flow is presented. The amplitude of the Doppler signal (proportional to the number of red blood cells at each velocity) is represented by the monitor gray-scale. The gray-scale image serves as a road map for range-gate placement. Pulsed Doppler US is not as sensitive as CW Doppler US, and aliasing can occur when high velocities are being measured.

Blood Flow Velocity↗
PubMed1994

Diabetic nephropathy: evaluation with renal duplex Doppler US.

PURPOSE: To compare Doppler ultrasonography (US) with conventional clinical and laboratory tests in evaluation of diabetic renal disease. METHODS: Ninety-eight patients with diabetes mellitus underwent renal Doppler (resistive index [RI] measurement) US examination. US data were compared with clinical variables and follow-up data. RESULTS: Thirty-four diabetic patients without nephropathy had a mean RI of 0.62 +/- 0.09, which was not significantly different from the mean RI of 0.64 +/- 0.09 in 23 patients with early diabetic nephropathy. Patients with established nephropathy had a mean RI of 0.83 +/- 0.11, which was significantly (P < .001) higher than in the other two groups. Renal RI correlated highly with serum creatinine concentration (r = .64) and creatinine clearance rate (r = .80). An elevated RI (> or = 0.70) was associated with impaired renal function, increased proteinuria at 24 hours, and poor outcome. Absent diastole (RI = 1.0), observed in 7% of patients, was an ominous sign: Five of seven patients underwent dialysis or transplantation shortly after US. CONCLUSION: RI is typically elevated in established nephropathy but is often normal in the early clinical stages of disease. Renal Doppler US provides an accurate indication of renal function in diabetic nephropathy but does not offer a great advantage over conventional tests.

Adolescent↗
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

Relative magnitude and asynchrony of directional components of contraction in sedated dog left ventricle.

The purpose of this study was to quantitate the temporal relationships and the extent and speed of shortening in segments of myocardium responsive to contraction in circumferential, longitudinal, and oblique fiber groups. Measurements were made in five sedated dogs (morphine, diazepam) with and without alterations in preload and afterload (nitroprusside, phenylephrine). The measurement interval was the phase of rapid contraction, determined by differentiation of the segment length vs. time. In the control state, percentage segment shortening was greater in circumferential than in longitudinal [15.2 +/- 0.24 (SE) vs. 10.5 +/- 0.80%; P = 0.0020] and in the subepicardial oblique than in the subendocardial oblique fiber directions (16.6 +/- 0.65 vs. 9.7 +/- 0.36%; P = 0.0010). Shortening was proportional to both maximum speed and duration of shortening (r = 0.735 +/- 0.015 and 0.757 +/- 0.017, respectively). Duration of shortening was significantly longer in circumferential than in longitudinal (mean difference 39.3 +/- 6.6 ms; P = 0.0039) and in subepicardial oblique than in subendocardial oblique directions (mean difference 27.7 +/- 5.5 ms; P = 0.0072). Velocities of up to 3.0 segment lengths/s were attained in response to nitroprusside. These data reveal the local anisotropy and asynchrony of contraction in the myocardium; however, they also support the concept of the myocardium as a functional continuum. The dominance of circumferential over longitudinal and subepicardial over subendocardial oblique contractile components indicates their relative contributions to the constriction of the midmyocardial shell.

Animals↗
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↗