Biomedical subjects

E F Halpern

Publications and source records attributed to E F Halpern.

66 records · Page 4Linked to original sources

PubMed1994

MR imaging of the liver at 1.5 T: value of signal averaging in suppressing motion artifacts.

OBJECTIVE: Prior reports have suggested that signal averaging is not as effective as phase reordering for suppressing motion-related artifacts on T1-weighted spin-echo MR imaging of the liver at high field strengths. We hypothesized that with shorter TEs, signal averaging could be effective, and therefore undertook this study to compare signal averaging with phase reordering at 1.5T. SUBJECTS AND METHODS: Thirty consecutive patients underwent MR imaging of the liver at 1.5 T with two T1-weighted spin-echo pulse sequences. In one sequence we used signal averaging and in the other we used phase reordering as the primary motion suppression techniques. For each patient, the order in which these sequences were performed was randomized; TR (400-500 msec), TE (11-12 msec), and field of view (32-34 cm) remained constant. Images were analyzed quantitatively for liver signal-to-noise ratio (SNR), liver-spleen contrast-to-noise ratio (CNR), and liver-lesion CNR (in 16 patients with focal liver lesions), as well as qualitatively (three observers, blinded to technique) for overall image quality. RESULTS: Signal averaging resulted in images with significantly greater liver SNR, liver-spleen CNR, and liver-lesion CNR than did phase reordering (p = .0001, .002, and .02, respectively). All observers showed a preference for the signal-averaged images. For one observer, this preference was statistically significant; for the others, it was not. CONCLUSION: Signal averaging can be an effective means of suppressing motion-related artifacts on T1-weighted MR images of the liver obtained at 1.5 T.

Artifacts↗

PubMed1993

Multicenter trial of ionic versus nonionic contrast media for cardiac angiography. The Iohexol Cooperative Study.

Contrast agents used for cardiac angiography are different in regard to ionicity, osmolality and physiologic effects. The nonionic contrast media have been shown to have less toxic effects and a better safety profile than do higher osmolar agents. To better assess this risk, clinically stable patients undergoing cardiac angiography were stratified according to the presence of diabetes mellitus, and level of serum creatinine, and then randomized to receive either iohexol (Omnipaque 350) or sodium meglumine diatrizoate (Renografin 76). All adverse events that occurred during and immediately after angiography were tabulated. A multivariate model was used to identify patients at increased risk for adverse outcome. The 1,390 patients were randomized to iohexol (n = 696) or diatrizoate (n = 694). Significant differences were found in the number of patients with contrast media-related adverse (iohexol vs diatrizoate: 10.2 vs 31.6%; p < 0.001) and cardiac adverse (7.2 vs 24.5%; p < 0.001) events. Severe reactions and the need for treatment were more frequent with diatrizoate than with iohexol, but there was no difference in the incidence of death. The presence of New York Heart Association classification 3 or 4 and serum creatinine > or = 1.5 mg/dl predicted a higher incidence of adverse events as a result of contrast media alone. Use of iohexol is associated with a lower incidence of all types of adverse events during cardiac angiography than is diatrizoate.

Adult↗

PubMed1993

Mammographically detected breast cancer: location in women under 50 years old.

The mammograms of 86 women under the age of 50 years with mammographically detected cancers were reviewed. Sixty-three of these cancers (73%) were found at the periphery of the breast as defined by a zone 1 cm wide beneath the subcutaneous fat or anterior to the retromammary fat. This finding is likely due to the geometric configuration of the breast. If the breast is hemispheric, then more than 50% of the volume of breast tissue lies within this zone in a large percentage of women. Furthermore, the contrasting adjacent fat likely improves the ability to perceive an abnormality. Interaction of the terminal ducts with chemicals contained within or produced by the fat is a much less likely reason for the high percentage of cancers in this zone. Radiologists should be aware of this phenomenon and pay particular attention to this zone.

Adipose Tissue↗

PubMed1993

Hemostatic protein polymer sheath: improvement in hemostasis at percutaneous biopsy in the setting of platelet dysfunction.

To study the effectiveness of the protein polymer sheath (PPS), a device intended to limit hemorrhage caused by percutaneous biopsy, in the setting of platelet dysfunction (which may be an important cause of such hemorrhage), percutaneous biopsies were performed in eight anesthetized pigs: four control pigs and four pigs treated with the experimental aspirinlike drug venopirin. These biopsies were performed with (a) a cutting needle only, (b) the cutting needle equipped with the PPS, and (c) the cutting needle equipped with a thrombin-coated PPS. Needle configuration and biopsy site were randomized. Blood loss associated with each needle configuration was measured and compared with that associated with the other configurations. Venopirin caused a statistically significant increase in blood loss with all needle configurations. The PPS significantly reduced blood loss in both the control pigs and those treated with venopirin (P < .05); thrombin coating was a statistically significant factor only in the venopirin-treated pigs.

Animals↗

PubMed1993

Cystic neoplasms of the pancreas: evaluation with endoscopic retrograde pancreatography.

Images from endoscopic retrograde pancreatography performed in 38 patients with cystic pancreatic neoplasms were reviewed to determine whether they might allow differentiation of malignant from benign lesions. Twenty-three patients had histologically proved benign lesions; 15 had frankly malignant lesions. Images were classified into four groups on the basis of the appearance of the pancreatic duct: (a) normal, (b) showing narrowing or draping; (c) showing communication with a cystic space, and (d) showing obstruction. Of the 23 patients with benign lesions, eight had normal studies, 11 had studies showing narrowing or draping, three had studies showing communication, and one had a study showing obstruction. Of the 15 patients with malignant lesions, one had a normal study, three had studies showing narrowing or draping, two had studies showing communication, and nine had studies showing obstruction. Overall, there was a significant difference in the rates of pancreatographic findings for benign and malignant tumors (P = .001). Although no finding proved to be an absolute indicator of benign or malignant disease, obstruction occurred with 60% of malignant tumors and was seen with only one benign lesion (4%).

Adenoma, Islet Cell↗

PubMed1991

Comparison of the rates of adverse drug reactions. Ionic contrast agents, ionic agents combined with steroids, and nonionic agents.

The influence of ionic agents alone, of diatrizoate plus two oral doses of methylprednisolone premedication, and of a nonionic agent (iohexol) upon the frequency and severity of adverse drug reactions (ADRs) was compared in ten hospitals during three separate time periods from 1985 to 1989. Nonionic agents were found to reduce significantly total ADRs; 52 of 8857 patients receiving nonionic agents experienced reactions, versus 263 of 6006 patients for ionics (P less than .0001). The frequency of reactions classed as mild (2.9% for ionic agents versus 0.476 for nonionic agents: P less than .001), moderate (1.2% versus 0.1%; P less than .001), or severe (0.37% versus 0.01%; P less than .001), also favored nonionic agents. Steroid premedication provided some protection, but iohexol was significantly better with respect to mild reactions (2.9% versus 0.4%, P less than .001), moderate reactions (0.9% versus 0.1%, P less than .01), and severe reactions (0.25% versus 0.01%, P less than .01). The contrast medium was the greatest risk factor for adverse reaction (odds ratio 7.3), while prior contrast reaction (odds ratio 6.25), and hay fever (odds ratio 2.3) were found to be significant independent risks. We conclude that nonionic agents are safer for intravenous use than ionic agents given alone or with corticosteroid premedication.

Diatrizoate Meglumine↗

PubMed1991

Anticoagulant effects of nonionic versus ionic contrast media in angiography syringes.

To determine whether nonionic contrast media present a clotting hazard when plastic or glass injection syringes are contaminated with aspirated blood, we evaluated two nonionic (iohexol and iopamidol) and two ionic (ioxaglate and diatrizoate) contrast agents. We used a blood:contrast media ratio of 2 mL:5 mL and ten normal donors, each studied at 10, 20, 30, and 60 minutes, a parallel study of clotting and fibrinopeptide A (FPA) generation in plastic tubes, and life table analysis to estimate more accurately donor-based early clotting probabilities. While ionic contrast media are stronger anticoagulants, both nonionic and ionic media retard clotting in plastic tubes, and clotting in plastic and glass angiography syringes in comparison to saline controls. A clotting probability of 1% for nonionic agents in plastic syringes was not reached until a time (mean +/- SD) of 21.5 +/- 3.2 minutes. This contrasts with a time of 8.7 +/- 2.5 minutes for saline control. With plastic syringes, no clotting at all was observed at 10 and 20 minutes with either class of agents. Neither class of agents hastened the generation of FPA. We found no evidence, therefore, that nonionic agents either cause clots or are procoagulant.

Angiography↗

PubMedDate not supplied

Ultrafast MR imaging of water mobility: animal models of altered cerebral perfusion.

"Single shot" magnetic resonance (MR) diffusion imaging was used to study the details of signal decay curves in experimental perturbations of cerebral perfusion induced by hypercapnia or death. Despite large perfusion increases observed with dynamic susceptibility-contrast MR imaging, no correlation with these changes was seen in either the diffusion coefficient or any other intravoxel incoherent motion (IVIM) model parameters in dog gray matter as arterial carbon dioxide pressure increased. Non-monoexponential signal decay in cat gray matter was seen both before and after death. In addition, cat gray matter demonstrated a steady decrease in the diffusion coefficient after death. These data are strong evidence that the fast component of the non-monoexponential diffusion-related signal decay is not due solely to perfusion. The authors believe that a second compartment of nonexchanging spins, most likely cerebrospinal fluid, accounts for the non-monoexponential decay.

Animals↗

PubMedDate not supplied

Measurement of stroke volume and cardiac output within a single breath hold with echo-planar MR imaging.

The measurement of cardiac output and ejection fraction is useful in the treatment of diverse cardiac and cardiopulmonary disease states. Although several techniques are available for accurate measurement of left ventricular parameters, assessment of the right ventricle is less well represented. No single method is overwhelmingly superior, each having different strengths and weaknesses. In the present study, the applicability of an echo-planar magnetic resonance (MR) imaging method in which a complete volumetric measurement of the right and left ventricles may be obtained during 12 heart-beats is demonstrated. This rapidity permits imaging during a 15-second breath hold. The authors show in 12 volunteers that breath-hold echo-planar volume measurements of both ventricles were consistent with results obtained with conventional MR imaging methods.

Adult↗

PubMedDate not supplied

Measurement of renal transit of gadopentetate dimeglumine with echo-planar MR imaging.

Times of peak gadolinium concentration ([Gd]) after intravenous (IV) and left ventricular (LV) bolus injection of gadopentetate dimeglumine were determined in renal cortex and medulla in normal rabbits and in rabbits after saline load (overhydration) or hemorrhage (dehydration). Magnetic resonance images were obtained with echo-planar inversion-recovery sequences, and signal intensity-versus-time curves in cortical and medullary regions of interest were converted to [Gd]-versus-time curves. Cortical perfusion measured with microspheres demonstrated that the three physiologic states were significantly different. There were three separate [Gd] peaks in both the cortex and medulla as the bolus moved from one anatomic compartment to the next. The first cortical peak occurred sooner after LV than after IV bolus injection (P < .05) and later in dehydrated than in normal and overhydrated rabbits (P < .05). The first medullary peak always followed the first cortical peak by about 6-10 seconds and mirrored the cortical patterns. The second and third cortical peaks were consistent with proximal and distal tubular transit. These peaks similarly showed faster response to LV than IV injection and were delayed by hemorrhage. The authors conclude that quantitative physiologic information can be obtained with dynamic contrast-enhanced MR imaging of the kidney.

Animals↗

PubMedDate not supplied

Mammographic appearance of ductal carcinoma in situ does not reliably predict histologic subtype.

Histologic subtypes of ductal carcinoma in situ (DCIS) have been correlated with disease prognosis. There are conflicting reports on whether the grade of DCIS can be predicted by the morphology of calcifications seen on mammography. We undertook this study to determine whether the grade of DCIS can be reliably and accurately determined by mammography prior to excisional biopsy. Ninety consecutive cases of DCIS from 1993 to 1996 were identified, of which 75 cases had mammograms available for review. Any lesion with invasion was excluded. The mammogram showed only a mass in 10 of 75 cases, a mass and calcifications in 3 of 75 cases, and calcifications alone in 62 of 75 cases. Three board-certified radiologists with special expertise in mammography reviewed and categorized the mammographic findings as well, intermediate or poorly differentiated DCIS without knowledge of the histologic diagnosis. Histologic grading was performed without knowledge of the mammographic finding. Receiver operating curves (ROCs) were computed for each of the radiologists. For microcalcifications, the ROC comparisons of the radiologists' opinions of tumor grade and random chance were not significantly different. In those cases with available magnification views, the grade assessment did not change significantly. If only a mass was present on mammography, well-differentiated DCIS was the predominant histologic subtype. A histologic grade of DCIS cannot accurately be determined prospectively based on the mammographic appearance of microcalcifications. However, if only a mass is present, this is more likely to represent well-differentiated DCIS.

Breast Neoplasms↗

PubMedDate not supplied

Representing both first- and second-order uncertainties by Monte Carlo simulation for groups of patients.

Actual implementation of probabilistic sensitivity analysis may lead to misleading or improper conclusions when it is applied to groups of patients rather than individual patients. The practice of combining first- and second-order simulations when modeling the outcome for a group of more than one patient yields an erroneous marginal distribution whenever the parameter values are randomly sampled for each patient while the results are presented as simulated means for the group of patients. This practice results in underrepresenting the second-order uncertainty. It may also distort the shape (especially the symmetry or extent of the tails) in the simulated distribution. As a result, it may lead to premature or incorrect conclusions of superiority. It may also result in inappropriate estimates of the value of further research to inform parameter values.

Confidence Intervals↗