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E J Halpern

Publications and source records attributed to E J Halpern.

At least 37 records · Page 2Linked to original sources
PubMed1998

Comparison of Doppler US and CT angiography for evaluation of renal artery stenosis.

RATIONALE AND OBJECTIVES: The authors compared Doppler ultrasound (US) with computed tomographic (CT) angiography in the evaluation of stenosis of the main renal artery. MATERIALS AND METHODS: Fifty-six patients who had undergone conventional angiography of the renal arteries participated in a prospective comparison of Doppler US (45 patients) and CT angiography (52 patients). US evaluation included both the main renal artery and segmental renal arteries. RESULTS: There were 27 main renal arteries with at least 50% stenosis in 20 patients. In 36 patients, there was no significant stenosis. All cases of main renal artery stenosis detected with Doppler US of the segmental arteries were also identified with Doppler US of the main renal artery. The by-artery sensitivity (63%) of US of the main renal artery was greater than that (33%) of US of the segmental arteries. CT angiography was more sensitive (96%) than Doppler US (63%) in the detection of stenosis, but the specificity of CT (88%) was similar to that of US (89%). The difference in the area under the receiver operating characteristic curve (AUC) between CT (AUC = 0.94) and US (AUC = 0.82) was statistically significant (P = .038). CONCLUSION: Doppler US of the main renal artery is more sensitive than Doppler US of segmental arteries in the detection of stenosis. CT angiography is more accurate than Doppler US in the evaluation of renal artery stenosis.

Adult↗
PubMed1998

Effect of distal resistance on Doppler US flow patterns.

PURPOSE: To quantify the effect of distal resistance on arterial flow patterns. MATERIALS AND METHODS: Spectral Doppler tracings were obtained from the suprarenal aorta, infrarenal aorta, and proximal renal arteries of 10 volunteers and from the common, internal, and external carotid arteries (CCA, ICA, and ECA, respectively) of 31 volunteers. Early systolic acceleration (ESA), peak systolic velocity (PSV), end diastolic velocity (EDV), and waveform morphology were evaluated. An in vitro flow model of a compliant vessel in a branched pattern was created to simulate the renal and carotid circulations. RESULTS: ESA and PSV were significantly lower in the renal artery than in the suprarenal aorta (P < .01). ESA decreased significantly from the CCA to the ICA (P < .001) but only minimally from the CCA to the ECA (P > .20). EDV increased slightly from the CCA to the ICA but decreased substantially in the ECA. As distal resistance was increased in the in vitro model, ESA was more rapid, systole was shortened, EDV was decreased, and PSV was increased. CONCLUSION: As blood flows into the low-resistance renal artery or ICA, antegrade flow is shifted into the latter portion of the cardiac cycle, resulting in apparent prolongation of systole and forward flow throughout diastole. As blood flows into the higher-resistance ECA, diastolic flow is diminished. The in vitro model reproduces these Doppler flow patterns by means of manipulation of distal resistance.

Adult↗
PubMed1997

Spiral computed tomography for staghorn calculi.

OBJECTIVES: To assess the utility of spiral computed tomography (CT) with three-dimensional reconstruction for preoperative planning of percutaneous nephrostolithotomy in patients with complex branched calculi (full staghorns). METHODS: Patients with complex branched stones were imaged with spiral CT with three-dimensional reconstruction. These images were compared with standard imaging modalities, including excretory urography and plain radiographs, for planning percutaneous access for nephrostolithotomy. The utility of the scan was evaluated. RESULTS: Ten patients with branched calculi were studied. Anatomic abnormalities were present in 5 patients. Excellent three-dimensional images were obtained in all patients without any complications related to the study. In 1 patient with multiple calculi in a horseshoe kidney, the three-dimensional image indicated a branched stone. The spiral CT scan was not helpful in directing percutaneous access in any patient. In a single patient, residual fragments noted during nephrostolithotomy were located by reference to the spiral CT scan. CONCLUSIONS: Spiral CT scans with three-dimensional reconstruction provide three-dimensional imaging of branched renal calculi. This modality provides minimal additional information over that obtained from standard radiographic studies for guiding nephrostolithotomy and cannot be recommended as a routine preoperative study. It was helpful in 1 patient to locate a residual fragment.

Adult↗
PubMed1996

Comparison of receiver operating characteristic curves on the basis of optimal operating points.

RATIONALE AND OBJECTIVES: We developed a method of comparing receiver operating characteristic (ROC) curves on the basis of the utilities associated with their optimal operating points (OOPs). METHODS: OOPs were computed for paired ROC curves on the basis of isocost lines in ROC space with slopes ranging from 0.1 to 3.0. For each pair of OOPs corresponding to a single isocost slope, the difference in costs and the variance of this difference was computed. A sensitivity analysis was thus obtained for the difference between the two curves over a range of isocost slopes. Three published data sets were evaluated using this technique, as well as by comparisons of areas under the curves and of true-positive fractions at fixed false-positive fractions. RESULTS: The OOPs of paired ROC curves often occur at different false-positive fractions. Comparisons of ROC curves on the basis of OOPs may provide results that differ from comparisons of curves at a fixed false-positive fraction. CONCLUSION: ROC curves may be compared on the basis of utilities associated with their OOPs. This comparison of the optimal performance of two diagnostic tests may differ from conventional statistical comparisons.

Costs and Cost Analysis↗
PubMed1996

Effects of training and experience in interpretation of emergency body CT scans.

PURPOSE: To determine the effects of level of training and other factors on the rate of discrepant interpretation of emergency body computed tomographic (CT) scans by trainees and staff radiologists. MATERIALS AND METHODS: Five hundred ninety-eight consecutive emergency CT studies were prospectively interpreted by radiology residents or board-certified body imaging fellows over a 12-month period. Each interpretation was reviewed within 12 hours by an attending body CT radiologist. Major discrepancies between staff radiologists' and trainees' interpretations were defined and those with the potential to affect immediate patient therapy; minor discrepancies were defined ad those without such potential. The effects on discrepancy rates were examined for abnormal versus normal CT findings and trauma versus nontrauma cases. RESULTS: Major and minor discrepancy rates were 1.2% and 6.5%, respectively, between interpretations made by the trainee and the staff radiologist. Overall, fellows demonstrated statistically significantly lower discrepancy rates than did senior of junior residents (5.9%, 13.7%, and 13.3%, respectively). The discrepancy rate was higher when CT findings were abnormal than when they were normal (13.5% vs 2.6%). There were no differences between discrepancy rates for trauma and nontrauma cases. CONCLUSION: Experience appeared to decrease discrepancy rates. Trainees were more likely to miss findings than to read normal scans as abnormal.

Certification↗
PubMed1995

A test pattern for quality control of laser scanner and charge-coupled device film digitizers.

Although clinical images provide the ultimate test of diagnostic performance for a film digitizer, such images are not generally suitable for daily quality control (QC) purposes. However, a well-designed test pattern will provide a rapid, comprehensive, objective and reproducible assessment of image quality. This pattern should evaluate various parameters of image quality, including high contrast resolution, low contrast discrimination, linearity of gray scale, geometric distortion, and noise. Furthermore, the pattern should detect light leak and film slippage, two problems commonly associated with film digitizers. The test pattern described in this manuscript was designed to provide quantitative measures of performance for a film digitizer. As part of a regular QC routine for a laser scanner or charge-coupled device digitizer, this pattern provides a simple method to identify and quantify changes in digital image quality.

Artifacts↗
PubMed1995

Threshold selection for CT angiography shaded surface display of the renal arteries.

The purpose of this study was to define objective criteria to calculate a tissue segmentation threshold for shaded surface display (SSD) rendering of the renal arteries with computed tomography angiography. Contrast-enhanced spiral CT scans were obtained through the renal arteries of nine patients. Six sets of SSD images were rendered for each patient with lower threshold values ranging from 80 to 130 Hounsfield units (HU) by increments of 10 HU. Visceral organ enhancement was measured in the aorta, liver, spleen, pancreas, and kidney. The segmentation threshold for each patient was determined by evaluation of the SSD images alone as well as by comparison with conventional arteriograms. The ideal threshold, as shown by comparison with conventional arteriography, was better correlated with a threshold value selected by qualitative evaluation of SSD images alone (rs = .42), than with measured enhancement in visceral organs (rs = -.289 to .009). The degree of stenosis was overestimated in a single renal artery (1 of 18) because of an inappropriate threshold selected by evaluation of the SSD images alone. In comparison with a segmentation threshold calculated from measured enhancement of visceral organs, a segmentation threshold selected by qualitative evaluation of the resulting SSD images is more likely to approximate the ideal threshold. Given the subjective nature of such threshold selection, further evaluation is warranted to determine whether threshold selection may result in inaccurate grading of stenosis.

Adult↗
PubMed1995

Renal artery stenosis: should we study the main renal artery or segmental vessels?

PURPOSE: To compare the sonographic diagnosis of renal artery stenosis (RAS) with Doppler interrogation of the main renal artery versus Doppler ultrasonography of segmental vessels. MATERIALS AND METHODS: The main renal artery-to-aortic peak systolic velocity ratio (RAR) and early systolic acceleration in segmental arteries were obtained in 186 patients. Conventional arteriographic correlation was available for 42 kidneys in 21 patients. Paired receiver operating characteristic (ROC) analyses were performed to evaluate RAR and minimum, average, and maximum early systolic acceleration in these 42 kidneys. RESULTS: Minimum early systolic acceleration was a better test than RAR (P = .05). Minimum early systolic acceleration plus RAR resulted in improved sensitivity for detection of RAS, but this improvement was not significant (P = .16). CONCLUSION: Minimum early systolic acceleration is the ultrasonographic method of choice to screen for RAS. RAR may provide marginal improvement in sensitivity but is probably not warranted in most clinical situations.

Adult↗
PubMed1995

Superior hypogastric plexus block for chronic pelvic pain in the presence of endometriosis: CT techniques and results.

PURPOSE: To evaluate the use of superior hypogastric plexus block with computed tomographic (CT) guidance in patients with endometriosis and chronic pelvic pain. MATERIALS AND METHODS: Seven blocks were performed on an outpatient basis in five women with endometriosis and pelvic pain. In the first four patients, one or two 20-gauge, 15-cm needles were placed anterior to the spine at the common iliac bifurcation from a posterior approach. In the fifth patient, the block was performed from an anterior approach with a single needle. RESULTS: One procedure resulted in mild pain relief, three in considerable pain relief, one in complete midline pain relief with no change in the lateral pain, and one in complete pain relief. One procedure was terminated because anesthetic was injected into the peritoneal cavity. There were no other complications. CONCLUSION: CT-guided superior hypogastric plexus block is easily performed and can be used to assess whether chronic pelvic pain can be attenuated by blocking the superior hypogastric plexus.

Adult↗
PubMed1995

Normal renal artery spectral Doppler waveform: a closer look.

PURPOSE: To characterize the spectral Doppler tracing of the normal renal artery. MATERIALS AND METHODS: Doppler tracings were obtained from a phantom of a vessel with variable compliance and from the kidneys of 15 healthy volunteers. RESULTS: In the phantom, vascular compliance had the following effects on systolic flow velocity patterns: low compliance, little change in the sharp appearance of the systolic component of the transmitted pulse; mildly increased compliance, down-stream dampening of early systolic acceleration (ESA) with the appearance of a sharp early systolic transmitted peak and of a more rounded late systolic compliance peak; high compliance, delayed and diminished transmitted peak that eventually disappeared within the enlarging down-stream compliance peak. Healthy subjects with compliant vessels had greater ESA and more frequently visualized early systolic peaks in the renal hilum than in the renal sinus. CONCLUSION: Absence of a discrete early systolic peak is a normal finding in young patients, especially in the more distal interlobar arteries. Loss of the early systolic peak may be explained on the basis of vascular compliance.

Acceleration↗
PubMed1995

Normal interval fetal growth rates based on obstetrical ultrasonographic measurements.

Analyzing fetal interval growth may improve detection of growth abnormalities. This study establishes normal limits for growth rates of fetal biparietal diameter, abdominal diameter, abdominal circumference, and femur length. Fetal measurements were obtained during 1450 obstetrical sonographic examinations in 510 patients with normal-weight term deliveries. Using a random-effects model for longitudinal data, cubic curves of size versus mean gestational age were fitted using a restricted maximum likelihood technique. Quadratic growth rate curves were then calculated as derivatives of the fitted curves. The growth rate equations are as follows: Biparietal diameter growth rate = 2.59 + 0.127 (MGA) - 0.000447 (MGA)2; abdominal diameter growth rate = 3.61 + 0.0325 (MGA) - 0.0017 (MGA)2; abdominal circumference growth rate = 11.3 + 0.102 (MGA) - 0.00534 (MGA)2; and femur length growth rate = 5.49 - 0.17 (MGA) + 0.00181 (MGA)2. Rates are expressed in mm/wk and mean gestational age in wk. Because standard deviations depend on the time interval between examinations, separate growth rate tables are provided for intervals of 4, 6, 8, and > or = 10 weeks.

Crown-Rump Length↗
PubMed1994

CT done 4-6 hr after CT arterial portography: value in detecting hepatic tumors and differentiating from other hepatic perfusion defects.

OBJECTIVE: Nontumorous perfusion defects occur during CT arterial portography (CTAP) as normal variants or in cirrhosis, focal fatty infiltration, and portal vein obstruction. The purpose of this study was to determine whether delayed CT 4-6 hr after CTAP improves sensitivity to hepatic tumors and differentiates them from other hepatic perfusion defects. SUBJECTS AND METHODS: CTAP was done at 1-cm increments on 26 patients for evaluation of hepatic tumors. Delayed CT scans were obtained 4-6 hr later in all patients. Two observers retrospectively reviewed the CT scans obtained during CTAP and recorded size, shape, and location of suspected hepatic tumors. Confidence levels were assigned for each tumor. The delayed CT scan was then interpreted in conjunction with the CT scans obtained during CTAP, and confidence levels were reassigned. Surgical correlation was obtained for all patients. In the 26 patients, 86 masses were found at surgery. The sensitivity and number of false-positives for both CTAP alone and CTAP combined with delayed CT were compared with a two-tailed Student t-test. Receiver-operating-characteristic analysis also was performed. RESULTS: CTAP detected 73 (85%) of the 86 hepatic masses. Delayed CT had no effect on the sensitivity of CTAP. However, adding delayed CT decreased the total number of false-positives by 11, a statistically significant difference (p < .05). Receiver-operating-characteristic analysis revealed a significantly greater (p < .05) area under the curve (Az index) of 0.927 +/- 0.025 for CTAP combined with delayed CT compared with 0.886 +/- 0.032 for CTAP alone. Delayed CT was most useful for larger (> 1 cm) wedge-shaped perfusion defects and least useful for smaller (< 1 cm) round defects. CONCLUSION: Delayed CT has no effect in detecting tumors but may be useful for differentiating tumors from other hepatic perfusion defects seen on CTAP. The greatest benefit of delayed CT is in evaluating regions obscured by large wedge-shaped perfusion defects on CT scans obtained during CTAP.

Colorectal Neoplasms↗
PubMed1994

Sonographic evaluation of fetal growth: growth rate variability as a function of the interval between examinations.

OBJECTIVE: Fetal growth rates determined on the basis of findings at two separate sonographic examinations can be used to detect growth abnormalities. This article determines the relationship between the length of the interval between examinations and the associated variability in measured fetal growth rates. MATERIALS AND METHODS: We analyzed 1479 fetal measurements of the biparietal diameter, average abdominal diameter, and femur length from 539 normal pregnancies. Mean growth rates were computed as functions of gestational age. The standard deviation of the growth rate was computed as a function of the interval between examinations. RESULTS: The standard deviation of fetal growth rates is relatively constant when the interval between examinations is 8-10 weeks or more, but increases substantially when the interval is fewer than 6 weeks. CONCLUSION: From a purely statistical point of view, the optimal interval for assessment of fetal growth rates is 8-10 weeks or more. Shorter intervals, however, usually are mandated by the clinical situation. Correction factors can be used to determine the standard deviations and associated confidence intervals for fetal growth measured over a period of fewer than 10 weeks.

Embryonic and Fetal Development↗
PubMed1993

Effect of focal zone on a curved array transducer.

RATIONALE AND OBJECTIVES: This study investigates the effect of electronic focusing of a linear array transducer on received ultrasound signal. METHODS: Two tissue-mimicking phantoms of known attenuation were imaged with a focal distance that was varied from 2 to 12 cm. Received signal was processed by Fourier analysis to compute average frequency and power as functions of depth within the phantom. RESULTS: Average received frequency increases dramatically over the first centimeter from the transducer and then decreases linearly to 8 to 11 cm with a slope proportional to the phantom's attenuation. Average frequency from greater depths decreases more rapidly and is dependent on the focal zone. Received power peaks at approximately the focal depth and decays exponentially beyond that level; the decay constant is proportional to the phantom's attenuation but independent of focusing. CONCLUSIONS: The frequency and power of received ultrasound signal are altered by electronic focusing in ways that may significantly influence both tissue characterization and clinical imaging applications.

Fourier Analysis↗