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D Rosenfeld

Publications and source records attributed to D Rosenfeld.

At least 37 records · Page 2Linked to original sources
PubMed1997

Design of selective adiabatic inversion pulses using the adiabatic condition

Adiabatic RF pulses play an important role in spin inversion due to their robust behavior in the presence of inhomogeneous RF fields. These pulses are characterized by the trajectory swept by the tip of the Beff vector and the rate of motion along it. In this paper, we describe a method by which optimized modulation functions can be constructed to render insensitivity to B1 inhomogeneity over a predetermined B1 range and over a wide band of frequencies. This is accomplished by requiring that the optimized pulse fulfill the adiabatic condition over this range of B1 inhomogeneity and over the desired frequency band for the complete duration of the pulse. A trajectory similar to the well-known sech/tanh adiabatic pulse, i.e., a half-ellipse, is used. The optimization process improves the slice profile by optimizing the rate of motion along this trajectory. The optimized pulse can be tailored to the specific design requirements; in particular, the transition sharpness may be traded off against the inverted bandwidth. Two design examples, including experimental results, demonstrate the superiority of the optimized pulses over the conventional sech/tanh pulse: in the first example, a large frequency band is to be inverted using a weak RF amplitude in a short time. In the second example, a pulse with a very sharp transition is required. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Surgical pancreatic complications induced by L-asparaginase.

Pancreatitis has been noted to be a potential complication in 2% to 16% of patients undergoing treatment with L-asparaginase for a variety of pediatric neoplasms, but rarely has surgical intervention been necessary. The authors present two fulminant cases of L-asparaginase-induced pancreatitis and review the current literature. The first patient is a 15-year-old boy who underwent induction chemotherapy with L-asparaginase for non-Hodgkin's lymphoma with bone marrow involvement. He presented with diffuse patchy necrosis of the pancreas as well as a large infected pancreatic pseudocyst. He subsequently required operative debridement of the pancreas and external drainage of the pseudocyst. He is currently doing well. The second patient is a 5-year-old boy who was treated with L-asparaginase for a diagnosis of acute lymphocytic leukemia. Within 3 weeks of initiation of therapy, fulminant pancreatitis developed, which progressed to multisystem organ failure. Computed tomography scan demonstrated extensive pancreatic necrosis involving 90% of the gland. He underwent surgical debridement of his necrotic pancreas and wide drainage of the lesser sac. Postoperatively he improved but subsequently multiple complications developed including erosion of his gastroduodenal artery with significant intraabdominal bleeding, which was controlled with angiographic embolization. Subsequently erosion of his endotracheal tube into the innominate vein developed, and he died. L-asparaginase-induced pancreatitis has been described after therapy for various pediatric neoplasms, and the reported cases have usually been self-limiting. However, our cases demonstrate potentially fatal sequelae of this complication and mandate early diagnosis with appropriate surgical intervention in this setting.

Adolescent↗
PubMed1996

A new adiabatic inversion pulse.

Adiabatic pulses play an important role in magnetization inversion in the presence of RF field inhomogeneity. In this work the authors present an efficient adiabatic inversion pulse that is able to selectively invert magnetization over a large frequency bandwidth in a short time. The pulse is constructed in two steps: (i) the optimal trajectory is determined and (ii) the optimal rate of motion along that trajectory is determined. The resulting pulse enables separately controlling and trading off the pulse duration against the transition width. The superiority of this pulse over the well known sech/tanh adiabatic pulse is demonstrated in a scenario where a large bandwidth should be inverted at a short time using limited B1 amplitude.

Algorithms↗
PubMed1996

Design of adiabatic selective pulses using optimal control theory.

Optimal control theory has been applied in the past for the design of RF pulses for selective excitation. This was the outcome of having established the controllability of the MR spin system for the selective excitation problem. "Minimum distance" was the main formulation used for the solution. Because of their robust behavior in the presence of inhomogeneous RF fields, adiabatic pulses play an important role in spin inversion and excitation. In this study, we present a method for incorporating adiabaticity into the optimal control problem by enhancing the cost functional with an appropriate term. Two different types of adiabatic terms are proposed. Furthermore, two methods are used to solve the optimal control problem, namely the Hamiltonian approach and the solution by mathematical programming. Design examples include both a frequency selective pulse for performing fat suppression by inversion and a regular inversion pulse. It is shown that, in the course of optimization, the pulse designer can trade-off slice resolution against pulse adiabaticity.

Humans↗
PubMed1996

Spontaneous biliary perforation: does external drainage constitute adequate therapy?

Spontaneous perforation of the biliary tract in infancy is rare; fewer than 100 cases have been reported. The authors report on two patients with spontaneous biliary perforation (SBP) who were treated during the past 5 years. One of the patients, a 10-month-old boy, presented with an extensive retroperitoneal mass, without jaundice. He was found to have a perforation in the pancreatic portion of the common bile duct (CBD). The second patient, a 6-week-old boy, had insidious onset of jaundice, abdominal distension, and acholic stools. He was found to have a perforation at the cystic duct/CBD junction and distal CBD stricture. Both patients initially underwent cholecystostomy and drainage. The second patient had a persistent external biliary fistula and high-grade stricture, and subsequently underwent CBD excision and Roux-en-Y hepaticojejunostomy, at age 12 weeks. The authors' findings do not support the widely held concepts proposing that (1) the diminished distal ductal caliber often associated with these lesions occurs secondary to the perforation rather than is a primary causative factor and (2) the distal biliary obstruction does not require treatment because it resolves with adequate drainage. In the absence of ductal abnormalities, the authors advocate external drainage. For SBP associated with an underlying stricture, prompt biliary intestinal bypass is necessary to avoid biliary cirrhosis and portal hypertension.

Bile Duct Diseases↗
PubMed1996

Is it necrotizing enterocolitis, microcolon of prematurity, or delayed meconium plug? A dilemma in the tiny premature infant.

Failure of a small premature newborn to adequately evacuate meconium for days or weeks has been attributed to "probable necrotizing enterocolitis (NEC)" or "microcolon of prematurity." The authors present an unusual type of "meconium plug syndrome" with the same clinical picture, seen in tiny premature babies (500 to 1,500 g), which required a contrast enema or Gastrografin upper gastrointestinal (UGI) series to evacuate the plugs. The obstruction resolved. Twenty babies (480 to 1,500 g) presented with the same clinical picture without any x-ray suggestion of NEC; contrast enemas were performed because of the suspicion of meconium plug syndrome. All 20 had extensive meconium plugs that were evacuated by the enema or by a Gastrografin UGI series. Most of them improved after the plugs were passed. These infants differ from typical full-term babies with meconium plug syndrome in a number of ways: (1) many of the mothers were on magnesium sulfate (MgSO4) or had eclampsia; (2) the plugs were diagnosed late rather than shortly after birth; and (3) the plugs were significant, extending to the right colon. The authors believe that when a tiny premature baby has findings consistent with meconium plug syndrome, the baby should be transported to radiology, for a Gastrografin enema, despite the difficulties involved. Delay postpones the start of feedings, and increases the number of radiographic studies.

Contrast Media↗
PubMed1995

Massive blood transfusion in a tertiary referral hospital. Clinical outcomes and haemostatic complications.

OBJECTIVE: To determine blood products used, clinical outcomes and frequency of haemostatic complications of massive blood transfusion. DESIGN AND SETTING: Retrospective review of the medical records of patients receiving more than 10 units of blood in 24 hours at a tertiary referral hospital in 1993. PATIENTS: Forty-three patients fulfilled this criterion. The major reasons for massive transfusion were trauma (46%; 20 patients), gastrointestinal bleeding (21%; nine patients) and leaking abdominal aortic aneurysm (14%; six patients). MAIN OUTCOME MEASURES: Blood products used, platelet count ( < 50 x 10(9)/L in first 48 h), prothrombin time (PT) and activated partial thromboplastin time (APTT) (twice normal in first 48 h), microvascular bleeding, and survival. RESULTS: The 43 patients used 824 units of packed cells 15.2% of the total used in 1993), 457 units of fresh frozen plasma (FFP) (17.1% of the 1993 total) and 370 units of platelets (14.8% of the 1993 total). Overall, these patients consumed 16% of the total number of units of blood product used in 1993 for 1478 transfusion episodes. The overall survival rate was 60%. Severe coagulopathy occurred in 19 patients (44%) (mortality rate, 74%), and 13 (31%) had severe thrombocytopenia ( < 50 x 10(9)/L). There was no significant correlation between the severity of coagulopathy/thrombocytopenia and total units transfused, or between the age of the units of blood and development of coagulopathy or microvascular bleeding. CONCLUSIONS: Severe coagulopathy is common after massive transfusions. In the absence of clear correlation with the number of units transfused, "formula" replacement with plasma and platelets is unlikely to avoid the problem. Duration of tissue hypoperfusion and platelet consumption are likely to be more important than simple haemodilution of coagulation factors.

Adolescent↗
PubMed1995

Radiology on the information superhighway.

PURPOSE: To explore the potential for the information superhighway to provide radiologists with new opportunities. MATERIALS AND METHODS: The Internet was used as the communication and distribution medium. MOSAIC, a graphical interface, provided access for clients, and a computer was used to serve text, images, sound, and cine onto the Internet. RESULTS: The system can be used to send reports and images to referring physicians or consulting radiologists; to provide a large database that is constantly available; to provide an increasing collection of teaching files; and to distribute interactive, multimedia teaching tools that can be used on any computer system. The use of the MOSAIC interface facilitates interaction, which allows users with limited computer experience to access the system. CONCLUSION: The Internet can dramatically expand the ways radiologists interact with their colleagues. These preliminary results indicate that there will be great challenges and opportunities for improving care and teaching in the future.

Computer Communication Networks↗
PubMed1995

A case study of lasers in cosmetic dentistry.

The dental laser offers revolutionary advantages over traditional cosmetic dental treatment for our patients. These advantages include precision, hemostasis, sterility, and minimal postoperative pain and swelling. The laser interacts with tissue to vaporize it in a predictable manner that produces predictable results. It is used in periodontal plastic surgery, gingivectomy, soft-tissue crown lengthening, crown and bridge gingival retraction, composite curing, biopsy, frenectomy, stage II implant recovery, and more. Fixed prosthetic impressions can be taken immediately following gingivoplasty and sutures and postoperative dressings are eliminated. This paper presents a case study in cosmetic dentistry to demonstrate many of these applications and summarizes current opinion regarding them. It also briefly describes what a laser is and how it works.

Adult↗
PubMed1994

The value of routine screening of female serum for antisperm antibodies in assisted reproductive technology cycles.

OBJECTIVE: To determine the effect of antisperm antibodies in the female serum on fertilization and pregnancy rates (PRs) in assisted reproductive technology (ART) cycles. DESIGN: Retrospective case control study. SETTING: Assisted reproductive technology program at North Shore University Hospital. PATIENTS, PARTICIPANTS: All patients undergoing an ART cycle in 1990 whose husbands did not have significant antisperm antibodies in the semen. Thirty-four female patients had significant antisperm antibodies level in the serum (antisperm antibodies-significant); 62 patients with no antibodies or nonsignificant levels constituted the control group (antisperm antibodies-negative). Incubation media were prepared with maternal serum in 37 of the antisperm antibodies-negative and in 10 of the antisperm antibodies-positive patients, whereas donor's serum (DS) was used for 25 and 24 patients, respectively. MAIN OUTCOME MEASURES: Fertilization rate and clinical PR, defined as an intrauterine sac by transvaginal ultrasonography, were recorded for each group. RESULTS: Analysis of variance showed a significant interaction between antisperm antibodies grouping and the type of media used, with fertilization rate in antisperm antibodies-significant patients significantly higher with maternal serum than with DS, whereas fertilization rate in antisperm antibodies-negative was quantitatively, though not statistically lower with maternal serum than with DS. When maternal serum was used, fertilization was higher in antisperm antibodies-significant than antisperm antibodies-negative. Of 29 clinical pregnancies, 11 were in antisperm antibodies-significant and 18 in antisperm antibodies-negative. In 10 of the pregnancies, maternal serum was used, whereas in 19 pregnancies DS was used. No variable was significantly predictive of pregnancy in the logistic regression analysis. CONCLUSIONS: [1] Female patients with significant levels of antisperm antibodies in the serum had similar fertilization rates as patients with nonsignificant levels if DS was used. [2] The use of maternal serum in antisperm antibodies-significant patients did not result in inferior fertilization rates or the occurrence of pregnancy. [3] These findings suggest that a female antisperm antibodies may not hinder fertilization in vitro. [4] This study questions the value of routine screening of female serum for antisperm antibodies in ART.

Adult↗
PubMed1994

Venous surgery in patients with congenital antithrombin III deficiency.

Congenital antithrombin III (ATIII) deficiency, although uncommon, is a condition of considerable surgical importance. Affected patients are at significant risk of venous thrombosis during a surgical illness and standard forms of prophylaxis may not be effective. In addition, sequelae of their thromboses may in turn make them a candidate for venous surgery. An ATIII concentrate is now available in Australia for clinical use. This report describes two patients who underwent surgery for postphlebitic limbs utilizing infusions of ATIII concentrate. The ATIII deficiency state is reviewed and a method is described that should allow safe surgery in these patients.

Adult↗
PubMed1992

A new two-dimensional phase unwrapping algorithm for MRI images.

The phase of an image obtained with many magnetic resonance imaging techniques is related to some physical variable of interest. This phase needs to be unwrapped, which is complicated by the presence of noise and multiple objects of irregular shape. A new two-dimensional phase unwrapping algorithm is presented, along with simulation results.

Algorithms↗
PubMed1992

Compression and reconstruction of MRI images using 2D DCT.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be compressed using the discrete cosine transform (DCT). We present here a method of treating the data that combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Fourier Analysis↗
PubMed1992

The central New Jersey neonatal brain haemorrhage study: design of the study and reliability of ultrasound diagnosis.

Over a 34-month period, 1105 newborns weighing between 501 and 2000 g at birth were enrolled in a prospective study of the aetiology and consequences of neonatal brain haemorrhage. The three participating hospitals care for approximately 85% of births in the study weight range in Middlesex, Monmouth and Ocean counties, New Jersey. Cranial ultrasonographic imaging through the anterior fontanelle was carried out a mean age of 4.9 +/- 2.2 hours, 25.5 +/- 4.8 hours and 7.2 +/- 0.8 days to detect haemorrhage and other brain lesions. In 93.2% of study infants, scans were read by two independent expert readers (blind to the clinical status of the child) with submission of the scan to a third reader in cases of disagreement. Confirmation of both presence or absence and, when present, scan of first diagnosis of germinal matrix and/or intraventricular haemorrhage (GM/IVH) by two independent readers was achieved in 76.3% of study infants. The first two readers agreed as to presence or absence of GM/IVH in 82.4% of infants (Kappa = 0.56). Interobserver agreement was affected by the reported scan quality and by the number of scans available, but not by the hospital of origin, race or birthweight of the infant.

Birth Weight↗
PubMed1992

Interinstitutional variability of follicle-stimulating hormone and estradiol levels.

OBJECTIVE: To evaluate the variability of follicle stimulating hormone (FSH) and estradiol (E2) results from different laboratories. DESIGN: Prospective analyses of sera separated and frozen, obtained from 15 female patients in the follicular phase. All kits used for radioimmunoassay (RIA) for FSH were from the Second International Reference Preparation (IRP). Four different kits were used for FSH and three for E2. SETTING: Sera obtained from each patient were separated into five test tubes and frozen. Analysis of all samples was done on the same day in each one of five participating hospital-based RIA laboratories (North Shore, Cornell, Yale, Mount Sinai, and Norfolk). PARTICIPANTS: Fifteen consecutive patients from the assisted reproductive technology program at North Shore University Hospital participated in the study. MAIN OUTCOME MEASURES: After FSH and E2 levels were tabulated for each laboratory, mean levels were calculated. RESULTS: Using the Bonferroni adjusted pairwise multiple comparisons analysis, significant differences were found between three groups of laboratories within the FSH results and three different groups within the E2 results. CONCLUSIONS: [1] Different results may be obtained on the same sera for FSH and E2 at different laboratories; [2] for FSH, even though the same IRP is used, different results are reached; [3] for E2, even when the same kits are used, results may be significantly different. These results suggest that specific FSH and E2 levels used to predict chances for achieving a viable pregnancy through in vitro fertilization should be interpreted with caution across institutions.

Estradiol↗
PubMed1992

An efficient algorithm for MR image reconstruction and compression.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Algorithms↗