US Measurements Research Articles

Reliability of Doppler ultrasound in follow-up studies.

To evaluate the reliability of repeat Doppler US measurements. Nine radiologists conducted two sets of Doppler US measurements on a healthy volunteer, with a time interval of 9 months. Peak systolic velocity (PSV), resistance index (RI), and pulsatility index (PI) were measured 10 times in 4 arteries. There was considerable intra- and inter-observer variation both at baseline and 9 months later. The PSV values from the carotid artery varied from 0.27 m/s to 1.95 m/s in February and from 0.22 m/s to 1.38 m/s in November. The RI values from the renal artery ranged from 0.44 to 0.71 in February and from 0.41 to 0.67 in November. The results of the 9-month follow-up varied markedly too. Best reproducibility was achieved by highly experienced radiologists both at baseline and 9 months later. The short-term and long-term reliability of Doppler US was poor when the measurements were performed by a heterogeneous group of radiologists. The RI and PI measurements were somewhat more reliable than the PSV measurements and are recommended for use in follow-up studies.

Doppler US measurement of portal venous flow: variability in healthy fasting volunteers.

To describe the intrinsic sampling variability of measurements of portal venous flow in healthy volunteers and to estimate the variability attributable to the sonographer, the subject, and the measurement. In a randomized controlled fashion, nine sonographers measured portal venous flow in five subjects. Each sonographer measured portal venous flow in each volunteer during three separate sessions with three measurements per session. Analysis of variance was used to estimate the contribution of several factors to the observed variability. Overall mean portal venous flow was 390 mL/min +/- 234 (range, 18-1,511 mL/min). The estimated variance components were 1.1 (3%), 2.5 (7%), 7.2 (21%), and 24.0 (69%) for the subject, the sonographer, the interaction between subject and sonographer, and the measurement or intrinsic variability. Similar results were obtained when the analysis of variance was fit by using the rank and median of the measurements. Substantial variability exists in measurement of portal venous flow. Variability attributed to inherent differences in repeat measurements contributes more to overall variability than that attributed to either sonographers or subjects.

Are current hydrophone low frequency response standards acceptable for measuring mechanical/cavitation indices?

The purpose of this paper is to determine the error introduced by ultrasonic hydrophones used to measure current or proposed Mechanical (MI) and Cavitation (CI) Indices, assuming that the hydrophones meet bandwidth specifications contained in US and IEC measurement standards. These indices are based on the peak rarefactional pressure, pr. Since the portion of the pressure waveform where pr occurs is dominated by low frequency components, attention was placed on the low frequency hydrophone response specifications. Both simulated and actual diagnostic pressure pulses (with center frequency fc) were subjected to single-pole high-pass filtering for a range of -3 dB cut-off frequencies (fa). The error in the indices introduced by this filtration was evaluated. At both fa = 0.5fc (the US requirement) and fa = 0.86fc (calculated from the IEC -6dB bandwidth specification at 0.5fc), results showed that errors exceeding -30% could be expected. Furthermore, to reduce errors to less than 5%, the low frequency hydrophone response should extend at least an order of magnitude below the center frequency of the pressure wave. For example, for a 3.5 MHz transducer, the hydrophone should have a lower cut-off frequency of less than 350 kHz, which at present constitutes a challenge because of the lack of commercial hydrophones calibrated below 1 MHz.

Reproducibility of Doppler ultrasound measurements.

The reproducibility of Doppler ultrasound measurements was studied in a group of radiologists with different experience of such measurements. The 12 participating radiologists measured peak systolic velocity (PSV), resistance index (RI), and pulsatility index (PI) from 3 arteries and PSV alone in one artery of a healthy person under standardized circumstances. Each participant repeated the measurements 10 times. Significant (p < 0.005) interobserver variation was seen in all of the variables, with an up to 14-fold difference in the PSV values measured and most variation resulting from differences between observers. The reproducibility of RI was better, most variation being within observers. Experience improved the reproducibility of the Doppler US measurements. Significant difference (p < 0.05) in Doppler US measurements was seen between the 3 experience groups. The difference was marked between the highly experienced and the medium experienced group when the variances of the measured values of PSV, RI, and PI from all 4 arteries were combined. The reproducibility of Doppler ultrasound measurements is poor. The value of the method is questionable.

Renal resistive indexes: variability in Doppler US measurement in a healthy population.

To determine the variability in resistive index (RI) in normal kidneys, possible causes of variability, and consequences of reporting a single value. Doppler ultrasound RI measurements were obtained in the upper, middle, and lower regions of 118 kidneys in 58 healthy subjects (aged 24-70 years; 35 women, 23 men) who subsequently underwent angiography. The effects of sampling a particular parenchymal region, vascular territory, or kidney were assessed. Kidney region, vascular territory, and right versus left kidney had no consistently significant effect (P < or = .05) on RI. Age had a statistically significant effect. RI readings were highly correlated with each other both within a subject and within a kidney. The probability that a single RI value would exceed 0.70 in a healthy 45-year-old subject was 6%; this decreased to 3% when three readings were averaged. The variability of RI measurements in a kidney suggests that a number of RI readings should be averaged before a single representative value is reported.

キンギョのシドマン型回避におけるフィードバック刺激の機能 フィードバック（情報）仮説対安全信号（恐怖制止）仮説

The present goldfish experiments in the shuttlebox were attempted to separate and test the feedback (informational) and safety-signal (fear inhibition) hypotheses, both of which may account for the reinforcing effects of the FS in avoidance conditioning. In Experiment I, four groups of goldfish (N=48) were trained with (or without) response contingent FS and with (or without) shock contingent FS in a Sidman avoidance schedule (S-S=R-S=30s). The shock contingent FS tended to facilitate acquisition only in the response measure. The response contingent FS, on the other hand, facilitated acquisition only in the US measure. In Experiment II, four groups of goldfish (N=48) were trained with (or without) response contingent FS and with a fixed (30 s) or variable (15-45 s) R-S interval in a Sidman avoidance schedule (S-S=30 s). The results showed that, in both response and US measures, the FS facilitated avoidance acquisition, whereas variable R-S deteriorated it. As a whole, the results of the present experiments were considered to support the safety-signal (fear inhibition) hypothesis.

Splenic Artery and Superior Mesenteric Artery Blood Flow: Nonsurgical Doppler US Measurement in Healthy Subjects and Patients with Chronic Liver Disease

Splenic Artery and Superior Mesenteric Artery Blood Flow: Nonsurgical Doppler US Measurement in Healthy Subjects and Patients with Chronic Liver Disease

EFFECT OF STAGE OF LACTATION AND DIET ON SERUM INSULIN LEVEL AND MONONUCLEAR LEUKOCYTE INSULIN RECEPTOR CHARACTERISTICS IN DAIRY COWS

Blood was collected from and measurements were made of body weight and ultrasonic backfat (US) in ten 2–6 yr old Holstein cows at 8 wk prepartum, 3 d postpartum and at 4, 6 and 12 wk of lactation. Cows were fed a low-fat (LF) total mixed ration containing 3.0% either extract and 13.6% acid detergent fiber ad libitum until day 15 postpartum when some of the diet concentrate was replaced by whole sunflower seeds (four cows) or sunflower seed hulls, sunflower seed meal and tallow (two cows) to yield diets high in fat (6.7 and 6.9%, respectively) and acid detergent fiber (18.1 and 17.9%, respectively). All diets were formulated to have a NE1 of 7.07 MJ kg−1 dry matter and were isonitrogenous. Milk yield and composition were measured daily during each week of blood collection. Radioimmunoassay for insulin was performed on eight serum samples collected at 0.5-h intervals commencing at 0730 h. Specific cell binding (SB) of insulin as well as number of and affinity constants for high affinity (N1, K1, respectively) and low affinity (N2, K2, respectively) insulin receptors were determined on mononuclear leukocytes (MNL) isolated from 250 mL of whole blood. Throughout the trial the US measurement in cows on the LF diet was greater than in cows on the high-fat (HF) diets. Body weight, dry matter intake and milk yield were similar in HF and LF fed cows. Serum insulin concentration was lower 3 d postpartum than prepartum and had increased by 4 wk of lactation. The increase was greater with HF feeding. Insulin SB to MNL was negatively correlated to body weight and N1 was positively correlated to US measurement. Percent insulin SB to MNL at 12 wk of lactation (8.4 ± 1.6) was lower than that found for all other stages of lactation. There was no effect of diet or stage of lactation on K1 and K2 values. At 4 wk of lactation N2 (1.44 ± 0.15 × 104 sites cell−1) was 100 and 50% greater than at 6 and 12 wk of lactation, respectively. Prepartum N2 (1.21 ± 0.17 × 104) did not differ from N2 at any other stage of lactation. At 4 wk of lactation N1 (5.79 ± 0.73 × 102 sites cell−1) tended (P &lt; 0.056) to be greater than that found for all other stages of lactation. There was no significant (P ≥ 0.05) effect of diet on N1, N2, K1, K2 or SB. Key words: Insulin, receptor, mononuclear leukocyte, lactation, dairy cow

Splenic artery and superior mesenteric artery blood flow: nonsurgical Doppler US measurement in healthy subjects and patients with chronic liver disease.

The accuracy of the duplex Doppler ultrasound system in the measurement of blood flow in the splenic artery and the superior mesenteric artery was evaluated in seven anesthetized dogs by comparing blood flow recordings obtained simultaneously with the electromagnetic flowmeter, with those obtained with the combination of B-mode and M-mode scanning. Various flow rates were produced by the infusion of dopamine. Splenic artery blood flow and superior mesenteric artery blood flow measured with the duplex system exhibited significant correlations with corresponding values obtained with electromagnetic flow measurements (r = .93 and r = .93, respectively). Changes in splanchnic circulation with the progression of chronic liver disease in humans were then investigated with the use of the duplex system. Splenic artery blood flow and superior mesenteric artery blood flow were significantly increased in patients with cirrhosis compared with patients with chronic hepatitis and healthy subjects. These results indicate that a hyperdynamic circulatory state may develop in the splanchnic circulation of the intestine and spleen in cirrhotic patients.

Cohesion: The Human Element in Combat.

Abstract : This book discusses The Significance of Military Cohesion, Measuring Military Power, Why Soldiers Fight, Characteristics of a Cohesive Army, Organizational Characteristics, Small Group and Unit Characteristics, and Leadership Characteristics. The Author Compares Cohesion in the North Vietnamese, US, Soviet, and Israeli Armies and Measures Societal Group Effects on Cohesion. Leadership in Cohesive Units is also very important.

Carbohydrate metabolism and electrolyte changes in human muscle tissue during heavy work.

Carbohydrate metabolism and electrolyte changes in human muscle tissue during heavy work.