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Biomedical subjects

D L Collins

Publications and source records attributed to D L Collins.

At least 19 recordsLinked to original sources
PubMed1999

Structural maturation of neural pathways in children and adolescents: in vivo study.

Structural maturation of fiber tracts in the human brain, including an increase in the diameter and myelination of axons, may play a role in cognitive development during childhood and adolescence. A computational analysis of structural magnetic resonance images obtained in 111 children and adolescents revealed age-related increases in white matter density in fiber tracts constituting putative corticospinal and frontotemporal pathways. The maturation of the corticospinal tract was bilateral, whereas that of the frontotemporal pathway was found predominantly in the left (speech-dominant) hemisphere. These findings provide evidence for a gradual maturation, during late childhood and adolescence, of fiber pathways presumably supporting motor and speech functions.

Adolescent↗
PubMed1999

Pre-term and particularly pre-labor cesarean section to avoid complications of gastroschisis.

The marked advantages and merit of pre-term and particularly pre-labor (PTPL) cesarean section (C-section) in the avoidance, and indeed, virtual elimination of severely disabling gastroschisis (GS) complications in infants diagnosed prior to birth by ultrasound has unfortunately remained controversial in the 10 to 12 years since it was first reported and strongly recommended by numerous authors. During this period, GS has remained one of the four major causes of the short-gut syndrome (SGS) in infancy and childhood and a major cause of prolonged, costly, complicated, and hazardous neonatal intensive care unit stays with requirements for total parenteral nutrition (TPN). The most serious and frequent complications of GS in infants born without PTPL C-section are the occurrence of the "peel", which greatly enlarges and rigidifies the eviscerated gut, and of "complicated GS" (intestinal atresia/s, stenosis, necrosis, perforations) (CGS). The "peel" occurs in 100% of these cases and CGS in approximately 20%. "Peel" enlargement and rigidification of eviscerated intestine in the presence of a reduced peritoneal cavity causes great difficulty in covering the eviscerated, enlarged, and rigidified gut with abdominal wall, skin, a prosthesis, etc., and frequently produces gut ischemia from excessive pressure, which may lead to necrotizing enterocolitis (NEC) and SGS as well as prolonged hospital stays. The presence of a "peel" greatly complicates the hazards of dealing with cases of CGS, as resection and anastomosis are virtually impossible in the presence of a "peel." The authors report personal experience with 77 cases of GS dating as far back as 1951; 44 of the infants were born after the onset of labor by vaginal or C-section delivery and all had some degree of "peel" formation. Of 320 cases from the literature (including some of the cases reported here), 61 (19.1%) involved CGS. Of the 33 cases born PT, and especially PL, there were no cases of "peel" and only 1 case of CGS (3.0%). This infant had a single atresia associated with a very small (1 cm) defect in the abdominal wall and no labor-induced "peel," which was easily and successfully repaired by resection and anastomosis. The 6.4-fold reduction in the occurrence of CGS by PTPL C-section (3.0% vs 19.1%) was statistically significant by the chi-square test (P < 0.05), as was the 100% elimination of the disabling "peel." If the single case of CGS associated with a very small defect and no labor or labor-associated "peel" is eliminated, the incidence of CGS in the remaining PTPL group of 32 cases falls to 0 (0% versus 19.1%, P < 0.007). PT and especially PL C-section may be expected to virtually eliminate "peel" formation and CGS and to remove GS as one of the four major causes of SGS. The findings of this report that PT labor prior to PT C-section may result in both "peel" formation and CGS further solidifies the role of labor in the production of both the "peel" and the equally disabling CGS. Failure to appreciate the central role of labor in GS complications has doubtless contributed to the persistent controversy concerning the value and importance of PTPL C-section for gastroschisis diagnosed in utero. The pediatric surgeon has an important responsibility with the obstetrician to monitor the possible occurrence of occult labor in the waning weeks of pregnancy and be prepared to do a prompt C-section if it occurs and there is adequate lung maturity. The achievement of "peel"- and CGS-free gut would greatly facilitate the use of the new Bianchi technique of gut reduction without anesthesia. The combination of the use of epidural anesthesia for the elective PTPL C-section with the Bianchi approach would spare both mother and baby any untoward effects of general anesthesia and present the potential for massive reductions in hospital costs with minimal patient manipulation and disturbance. For infants born with labor-associated "peel," re-evaluation of the suitability and effectiv

Cesarean Section↗
PubMed1999

Automated extraction and variability analysis of sulcal neuroanatomy.

Systematic mapping of the variability in cortical sulcal anatomy is an area of increasing interest which presents numerous methodological challenges. To address these issues, we have implemented sulcal extraction and assisted labeling (SEAL) to automatically extract the two-dimensional (2-D) surface ribbons that represent the median axis of cerebral sulci and to neuroanatomically label these entities. To encode the extracted three-dimensional (3-D) cortical sulcal schematic topography (CSST) we define a relational graph structure composed of two main features: vertices (representing sulci) and arcs (representing the relationships between sulci). Vertices contain a parametric representation of the surface ribbon buried within the sulcus. Points on this surface are expressed in stereotaxic coordinates (i.e., with respect to a standardized brain coordinate system). For each of these vertices, we store length, depth, and orientation as well as anatomical attributes (e.g., hemisphere, lobe, sulcus type, etc.). Each arc stores the 3-D location of the junction between sulci as well as a list of its connecting sulci. Sulcal labeling is performed semiautomatically by selecting a sulcal entity in the CSST and selecting from a menu of candidate sulcus names. In order to help the user in the labeling task, the menu is restricted to the most likely candidates by using priors for the expected sulcal spatial distribution. These priors, i.e., sulcal probabilistic maps, were created from the spatial distribution of 34 sulci traced manually on 36 different subjects. Given these spatial probability maps, the user is provided with the likelihood that the selected entity belongs to a particular sulcus. The cortical structure representation obtained by SEAL is suitable to extract statistical information about both the spatial and the structural composition of the cerebral cortical topography. This methodology allows for the iterative construction of a successively more complete statistical models of the cerebral topography containing spatial distributions of the most important structures, their morphometrics, and their structural components.

Algorithms↗
PubMed1998

Design and construction of a realistic digital brain phantom.

After conception and implementation of any new medical image processing algorithm, validation is an important step to ensure that the procedure fulfills all requirements set forth at the initial design stage. Although the algorithm must be evaluated on real data, a comprehensive validation requires the additional use of simulated data since it is impossible to establish ground truth with in vivo data. Experiments with simulated data permit controlled evaluation over a wide range of conditions (e.g., different levels of noise, contrast, intensity artefacts, or geometric distortion). Such considerations have become increasingly important with the rapid growth of neuroimaging, i.e., computational analysis of brain structure and function using brain scanning methods such as positron emission tomography and magnetic resonance imaging. Since simple objects such as ellipsoids or parallelepipedes do not reflect the complexity of natural brain anatomy, we present the design and creation of a realistic, high-resolution, digital, volumetric phantom of the human brain. This three-dimensional digital brain phantom is made up of ten volumetric data sets that define the spatial distribution for different tissues (e.g., grey matter, white matter, muscle, skin, etc.), where voxel intensity is proportional to the fraction of tissue within the voxel. The digital brain phantom can be used to simulate tomographic images of the head. Since the contribution of each tissue type to each voxel in the brain phantom is known, it can be used as the gold standard to test analysis algorithms such as classification procedures which seek to identify the tissue "type" of each image voxel. Furthermore, since the same anatomical phantom may be used to drive simulators for different modalities, it is the ideal tool to test intermodality registration algorithms. The brain phantom and simulated MR images have been made publicly available on the Internet (http://www.bic.mni.mcgill.ca/brainweb).

Brain↗
PubMed1997

Imaging of axonal damage in multiple sclerosis: spatial distribution of magnetic resonance imaging lesions.

We performed magnetic resonance imaging and magnetic resonance spectroscopic imaging on 28 patients with multiple sclerosis stratified for disability and clinical course (relapsing with at least partial remissions or secondary progressive disease). Lesions were segmented on the conventional proton density and T2-weighted magnetic resonance images, and lesion distribution images were generated for, each patient. The conventional magnetic resonance and spectroscopic images were transformed into a standard brain-based stereotaxic coordinate space, allowing comparison of images from different patients on a voxel-by-voxel basis. The spatial distribution of lesions in the transformed magnetic resonance images did not differ significantly between the relapsing and the progressive disease groups. We then generated from the individual data sets, group lesion probability distribution images for the relapsing and the progressive disease groups. The spatial distribution of metabolites was characterized with respect to lesion distribution using the magnetic resonance spectroscopic images transformed into stereotaxic space and averaged. The neuronal marker N-acetylaspartate was diffusely lower in the multiple sclerosis patients than in normal control subjects. Comparison of the averaged metabolite and T2-weighted lesion probability images confirmed loss of N-acetylaspartate in regions of both high and low lesion probability. This suggests that diffuse axonal volume loss or dysfunction extends beyond the inflammatory lesions of multiple sclerosis, perhaps due to microscopic disease or wallerian degeneration along projection pathways of axons traversing the lesions.

Adult↗
PubMed1997

Incorporating prior knowledge into image registration.

The first step in the spatial normalization of brain images is usually to determine the affine transformation that best maps the image to a template image in a standard space. We have developed a rapid and automatic method for performing this registration, which uses a Bayesian scheme to incorporate prior knowledge of the variability in the shape and size of heads. We compared affine registrations with and without incorporating the prior knowledge. We found that the affine transformations derived using the Bayesian scheme are much more robust and that the rate of convergence is greater.

Adolescent↗
PubMed1996

Statistics for investigation of multimodal MR imaging data and an application to multiple sclerosis patients.

Magnetic resonance spectroscopy can image axonal damage specifically based on changes in N-acetyl aspartate (NAA), a neuronal marker. We have developed statistical methods for multimodal analysis of MR spectroscopic images. These methods, which are extensions of mixed-effect models, have allowed us to quantify differences in images from different subgroups of patients with multiple sclerosis (MS) and to determine the dependence of chemical pathology on clinical disability, duration of disease and lesions on T2-weighted MRI. Statistical power was improved by using all reliable resonance intensities in the spectroscopic images while taking into consideration the intra-subject correlations. We studied 17 normal subjects, 14 patients with relapsing remitting (RR) MS and 21 patients with chronic progressive (CP) MS. The ratio of resonance intensities of N-acetylaspartate over creatine (Cr) was found to be significantly lower than normal in normal appearing white matter (NAWM) of both RR and CP patients (19.6% in RR, 28.8% in CP), NAA/Cr was decreased even more in MS plaques than in NAWM (44.2% in RR, 17.7% in CP), NAA/Cr was correlated with clinical disability (p < 0.02) and disease duration (p < 0.1). Our results suggest that, in this setting, MRS reflects accumulated neuronal loss or damage and can be used as a measure of disease severity. The methods developed provide opportunities to evaluate the relationship between inflammation, demyelination, axonal loss and clinical disability in future studies.

Aspartic Acid↗
PubMed1996

Abdominal tuberculosis in children: review of 26 cases.

The protean clinical manifestations and varied complications of abdominal tuberculosis continue to challenge the diagnostic acumen and therapeutic skills of all physicians. Although abdominal tuberculosis in children has not been common in the United States over the past 2 decades, the authors found 26 case reports for the period 1980-1993. Three clinical patterns were evident: intestinal (13) peritoneal (9), and asymptomatic with incidental calcifications apparent on abdominal radiographs (4). The diagnosis was suspected for only 23% of these cases, which emphasizes the nonspecific symptomatology caused by this extrapulmonary manifestation and the need for a high index of suspicion to make a prompt diagnosis. In this study, 24 of the 26 (91%) were of Hispanic origin; the other two were indo-Chinese, another high-risk group. Most patients (88%) had a positive PPD skin test result. Mycobacteria were isolated from 15 of 21 (71.4%) cultures, with M bovis in 80% and M tuberculosis in 20%. Antituberculous chemotherapy is the mainstay of treatment; surgery is reserved for tissue diagnosis in cases of peritoneal tuberculosis and for the management of complications of intestinal tuberculosis. The response to chemotherapy usually is excellent, and long-term sequelae are uncommon. It appears that steroids do not decrease the incidence or degree of fibrosis in intestinal tuberculosis.

Adolescent↗
PubMed1996

Accurate, noninvasive diagnosis of human brain tumors by using proton magnetic resonance spectroscopy.

Although conventional proton magnetic resonance imaging has increased our ability to detect brain tumors, it has not enhanced to nearly the same degree our ability to diagnose tumor type. Proton magnetic resonance spectroscopy is a safe, noninvasive means of performing biochemical analysis in vivo. Using this technique, we characterized and classified tissue from normal brains, as well as tissue from the five most common types of adult supratentorial brain tumors. These six tissue types differed in their pattern across the six metabolites measured. 'Leaving-one-out' linear discriminant analyses based on these resonance profiles correctly classified 104 of 105 spectra, and, whereas conventional preoperative clinical diagnosis misclassified 20 of 91 tumors, the linear discriminant analysis approach missed only 1. Thus, we have found that a pattern-recognition analysis of the biochemical information obtained from proton magnetic resonance spectroscopy can enable accurate, noninvasive diagnosis of the most prevalent types of supratentorial brain tumors.

Adult↗
PubMed1996

Parents' and children's reactions to taking blood in a nutrition survey.

OBJECTIVE: To assess the reactions of parents and their children to the request for a blood sample and an attempt to take blood. METHODS: 1859 children aged 1.5-4.5 years took part in a national survey of diet and nutrition. A retrospective inquiry of the parents' and children's reported reactions was carried out six to 18 months later by postal questionnaire sent only to the 1157 who had given consent for an attempt to take blood. RESULTS: 866 questionnaires were returned; 790 were from parents of children in whom an attempt to take blood had been successful. Thirteen per cent said that their child had given blood previously. About 30% discussed the request with the family doctor or nurse. Some 90% said that they were given enough information and that the phlebotomist was sympathetic. Attempting to take blood caused upset in over 50%, which, in most, lasted for less than five minutes. A substantial minority were upset for up to 30 minutes and a few much longer. Bruising or bleeding occurred in 20-27%. Degree and duration of upset were both adversely associated with a failed attempt to obtain blood. CONCLUSION: The majority of preschool children experienced no more than a little upset of short duration after an attempt to take blood, but a substantial minority exhibited a greater degree of upset. These responses should be taken into account when assessing the benefits and risks of the procedure. The best equipment and expertise should be employed for taking blood as successful attempts are less upsetting.

Blood Specimen Collection↗
PubMed1994

Use of proton magnetic resonance spectroscopy for monitoring disease progression in multiple sclerosis.

Decreases in brain N-acetylaspartate are associated with neuronal loss or dysfunction. We report a longitudinal study in which changes in the N-acetylaspartate to creatine resonance intensity ratio measured by brain proton magnetic resonance spectroscopy were used to follow the progression of brain pathology in 7 patients with multiple sclerosis over an 18-month period. Four of the patients had a history of recurrent relapses and 3 had a secondary progressive course. All had clinical and magnetic resonance imaging evidence of persistent neurological abnormalities. At 6-month intervals proton magnetic resonance spectra were obtained and the N-acetylaspartate-creatine ratio was determined for each patient. The volumes of hyperintense signal from lesions on conventional magnetic resonance images and the Kurtzke Expanded Disability Status Scale scores were determined concurrently. At the onset of the study, the N-acetylaspartate-creatine ratio was significantly (p < 0.05) lower in the central brain volumes from the patients than in 13 normal control subjects. At 12 and 18 months of follow-up, the ratio had decreased further in all patients (p < 0.05), consistent with progressive accumulation of neuronal damage. In contrast to magnetic resonance spectra data, changes in lesion volume on magnetic resonance images or disability status did not reach significance over this period. Subgroup analysis showed that changes (increases or decreases) in the N-acetylaspartate-creatine ratio between consecutive 6-month examinations correlated significantly (r = -0.74, p < 0.005) with changes in lesion volume on magnetic resonance images in patients with a history of relapses.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspartic Acid↗
PubMed1993

Congenital nonprogressive myopathy with Möbius and Robin sequence--the Carey-Fineman-Ziter syndrome: a confirmatory report.

Recently, we evaluated a 27-month-old boy with congenital generalized nonspecific myopathy, Möbius sequence, Robin sequence, and failure to thrive. We think the child has the same entity described by Carey, Fineman, and Ziter in 1982 [J Pediatr 101:353-364] and as such represents only the third example of this unusual syndrome. Review of the large number of conditions in which the Robin sequence occurs supports heterogeneity. Our case strengthens the Möbius-Robin association and further defines the Carey-Fineman-Ziter syndrome as a viable entity. It is most likely inherited as an autosomal recessive trait.

Abnormalities, Multiple↗
PubMed1993

Chronic stress from the Goiania 137Cs radiation accident.

At the invitation of the Brazilian government, the authors conducted a multidisciplinary field study in Goiania, Brazil, 3 1/2 years after an accident involving 137Cs, a radioactive cesium isotope. They compared subjects exposed to low levels of ionizing radiation, subjects who experienced anticipatory stress from fear of radiation exposure, and a nonirradiated control group. Results indicated the presence of chronic stress, as measured by psychological, behavioral, and neuroendocrine indices, in subjects who were exposed as well as in subjects fearful of potential radiation exposure. Anticipatory stress associated with potential exposure to ionizing radiation resulted in a level of stress similar to that from actual exposure to ionizing radiation. These findings have implications for past and future radiation accidents.

Accidents↗
PubMed1992

Operative intervention for pediatric liver injuries: avoiding delay in treatment.

To identify the physiological and anatomic factors that characterize the need for operative management of blunt pediatric liver injuries, the case records of 106 pediatric trauma victims with liver injuries over a 6-year period were reviewed. Sixty-nine patients were managed without operation (nonoperative) and 37 underwent operation, 7 with penetrating and 30 with blunt liver injuries. Of these 30 patients, 21 underwent laparotomy due to blunt liver injuries (operative); the remaining 9 patients required operation due to associated intraabdominal injuries. Nine (45%) of the 21 operative patients had major hepatic vein or retrohepatic vena caval injuries, 7 of whom died. Overall mortality was 9.4% (10/106). When nonoperative and operative groups were compared, those who underwent laparotomy due to blunt liver injuries: (1) had significantly lower Champion and Pediatric Trauma Scores due to multisystem injury; (2) had 25% or greater lobar disruption with pelvic blood collections on computed tomography scan; (3) underwent early transfusion within 2 hours of admission (18/21); and (4) were frequently found to have a major hepatic vein or retrohepatic vena caval injury at the time of operation. Only one patient successfully managed without operation received greater than 30 mL/kg of blood products within 24 hours of admission. As selective nonoperative management of pediatric liver injuries gains widespread acceptance, the identification of factors that predict the need for operative intervention will limit the potential risks of delay in treatment.

Abdominal Injuries↗
PubMed1992

Behavioral differences of irradiated persons associated with the Kyshtym, Chelyabinsk, and Chernobyl nuclear accidents.

Three nuclear accidents besides Chernobyl have occurred in the former Soviet Union. The accidents occurred around Kyshtym and Chelyabinsk in the Ural Mountains between 1949 and 1967 and contaminated over one-half million people. The health ministries are now interested in the data previously collected on these irradiated populations in order to examine the health (e.g., psychological, hereditary, genome damage, etc.) implications of long-term radiation exposure.

Accidents↗
PubMed1991

Hepatic vein and retrohepatic vena caval injuries in children. Sternotomy first?

Major hepatic vein and retrohepatic vena caval injuries are often fatal because of massive uncontrollable hemorrhage. Children with these injuries can be identified by their unique and dramatic clinical presentation and the selective use of computed tomographic imaging. Volume resuscitation promotes abdominal wall tamponade and hemodynamic stability until the abdomen is opened, at which point there may be sudden exsanguination before vascular control can be obtained. An alternative approach is to open the sternum before opening the abdomen. Management in this sequence provides rapid vascular control and improves the efficiency of hepatic exclusion. To date, five children with major hepatic vascular injuries have been treated with the sternotomy-first approach and four have survived; an atriocaval shunt was used on two occasions. Although sternotomy before laparotomy improves the efficiency of hepatic exclusion and may offer improved survival, accurate preoperative case selection limits its routine use.

Adolescent↗
PubMed1991

Three-dimensional display of cortical anatomy and vasculature: magnetic resonance angiography versus multimodality integration.

We present two methods for acquiring and viewing integrated three-dimensional (3D) images of cerebral vasculature and cortical anatomy. The aim of each technique is to provide the neurosurgeon or radiologist with a 3D image containing information which cannot ordinarily be obtained from a single imaging modality. The first approach employs recent developments in MR which is now capable of imaging flowing blood as well as static tissue. Here, true 3D data are acquired and displayed using volume or surface rendering techniques. The second approach is based on the integration of x-ray projection angiograms and tomographic image data, allowing a composite image of anatomy and vasculature to be viewed in 3D. This is accomplished by superimposing an angiographic stereo-pair onto volume rendered images of either CT or MR data created with matched viewing geometries. The two approaches are outlined and compared. Results are presented for each technique and potential clinical applications discussed.

Brain↗