Robust Initialization of Active Shape Models for Lung Segmentation in CT Scans: A Feature-Based Atlas Approach

Model-based segmentation methods have the advantage of incorporating a priori shape information into the segmentation process but suffer from the drawback that the model must be initialized sufficiently close to the target. We propose a novel approach for initializing an active shape model (ASM) and apply it to 3D lung segmentation in CT scans. Our method constructs an atlas consisting of a set of representative lung features and an average lung shape. The ASM pose parameters are found by transforming the average lung shape based on an affine transform computed from matching features between the new image and representative lung features. Our evaluation on a diverse set of 190 images showed an average dice coefficient of 0.746 ± 0.068 for initialization and 0.974 ± 0.017 for subsequent segmentation, based on an independent reference standard. The mean absolute surface distance error was 0.948 ± 1.537 mm. The initialization as well as segmentation results showed a statistically significant improvement compared to four other approaches. The proposed initialization method can be generalized to other applications employing ASM-based segmentation

Structural fumigation efficacy against Tribolium castaneum in flour mills

Structural fumigations of food processing plants to manage stored-product insects have been a major component of pest management programs, but limited information on field efficacy is available. Efficacy, based on pheromone trapping data, consists of initial reduction in captures after treatment and recovery in trap captures over time after treatment (i.e., rebound). Patterns of Tribolium castaneum reduction and rebound were evaluated after 21 fumigations in two flour mills. Influence of time of year fumigation occurred, environmental conditions, and impact of other pest management tactics on efficacy was determined as well. Information generated can be used to guide fumigation decisions, including the development of risk thresholds for levels of pheromone trap captures. Keywords: Tribolium castaneum, Fumigation, Flour mills, Efficacy, Methyl bromid

Rapid axonal transport in focally demyelinated sciatic nerve

Focal demyelination was produced in rat sciatic nerve by unilateral intraneural injection of anti-galactocerebroside serum. A functional lesion was confirmed by the presence of nerve conduction block. Histologically, this corresponded to demyelination of 50-70% of the fibers in nerve cross sections; axonal structures appeared intact. At the time of maximal demyelination (7 d), 35S-methionine or 3H-fucose was injected bilaterally into the spinal cord ventral horn. At later times (5 hr-7 d), the sciatic nerve was removed and radioactivity in successive nerve segments was quantitated. The transport rates (approximately 260 mm/d) and the composition of transported proteins and glycoproteins (separated on 7-15% polyacrylamide gradient gels) were not altered in lesioned nerves relative to contralateral control nerves. Light microscopic autoradiographic analysis revealed a similar localization of axonally transported and deposited glycoproteins in demyelinated and control fibers. Initially (8 hr), the majority of label was over axons. Labeled glycoproteins remaining in the nerve after 1 week were retained mainly in axolemmal regions. We conclude that acute focal primary demyelination does not lead to major alterations in the transport or deposition of newly synthesized macromolecules

Retrograde axonal transport of endogenous phospholipids in rat sciatic nerve

Anterograde axonal transport of phospholipids occurs at a rate of several hundred millimeters per day. However, although labeled precursors are incorporated into phospholipids in the neuronal cell bodies within several hours, these newly synthesized phospholipids are committed to transport over a much longer period of time. Thus, maximal accumulation of radioactive lipids in axons and nerve endings does not occur for several days (e.g., 4 to 7 days in rat optic tract and sciatic nerve). We have now investigated the retrograde axonal transport of endogenous phospholipid molecules in sensory neurons of rat sciatic nerve. Labeled phospholipids were delivered to axons and nerve endings of these cells by anterograde axonal transport following injection of [2-3H] glycerol into the L5 dorsal root ganglion. At various times following precursor injection two ligatures, 9 mm apart, were applied to the mid-thigh region of the sciatic nerve. Animals were sacrificed 3 to 48 hr after nerve ligation, nerves were dissected and sectioned into 5-mm segments, and phospholipid radioactivity in each segment was determined. The time-dependent accumulation of labeled phospholipids distal to the distal ligature demonstrated their retrograde axonal transport. The time course of retrograde transport for these phospholipids was more prolonged and peaked several days later than the time course for the anterograde transport phase. Further information regarding the relationship between radioactive phospholipids arriving at the nerve endings by anterograde transport, and their subsequent "turn-around" and retrograde transport back to the nerve cell bodies, was obtained by analyzing the phospholipid class label distribution of both of these transport phases at various times following precursor injection.(ABSTRACT TRUNCATED AT 250 WORDS

Deposition and transfer of axonally transported phospholipids in rat sciatic nerve

Radioactive glycerol, ethanolamine, or choline injected into the vicinity of the cell bodies of rat sciatic nerve sensory fibers is incorporated into phospholipid. Some newly synthesized ethanolamine and choline phosphoglycerides are subsequently committed to transport down the sciatic nerve axons at a rate of several hundred millimeters per day. Most labeled choline phosphoglycerides move uniformly down the axons; in contrast, the crest of moving ethanolamine phosphoglycerides is continually attenuated. These data, as well as differences in the clearance of these phospholipids distal to a nerve ligature, suggest that various classes of labeled phospholipids are differentially unloaded from the transport vector (possibly by exchange with unlabeled lipid in stationary axonal structures) during movement down the axons. The extent of unloading appears to be defined by the base moiety; both diacyl and plasmalogen species of ethanolamine phosphoglycerides exchange extensively with stationary axonal lipids, while most choline phosphoglycerides continue down the axons. Autoradiographic studies with 3H-choline and 3H-ethanolamine demonstrated that most unloaded phospholipid is initially deposited in axonal structures; some of this unloaded lipid is subsequently transferred to the axon/myelin interface (axolemma?) and then to myelin. Although transported ethanolamine phosphoglycerides exchange more extensively with lipids in stationary axonal structures than do choline phosphoglycerides, at early times more label from 3H-choline is found in myelin. A model to resolve this seeming discrepancy is proposed, wherein a differential topographic localization of phospholipid classes in the membrane of the transport vector allows for a preferential extensive exchange of transported ethanolamine phosphoglycerides with lipids in stationary axonal structures, while choline phosphoglycerides become available for rapid transfer to myelin by a process involving vesicle fusion with axolemma

Purine metabolism during strenuous muscular exercise in man

This study was designed to examine the influence of exercise on purine metabolism in man. In 15 men, the plasma uric acid concentration increased from 6.9 to 8.5 mg/dl following a 5000-m race and from 6.2 to 7.9 mg/dl in 11 men following a 42-km marathon. During a progressive exercise test on a cycle ergometer, the plasma uric acid concentration did not change significantly in 11 subjects. However, the plasma oxypurines increased from 19 [mu]M at rest to 50 [mu]M at exhaustion and the urinary excretion of oxypurines increased from 140 to 400 [mu]mol/g creatinine. Intracellular ATP decreased from 5.17 to 2.91 [mu]mol/g and ADP and AMP increased from 0.85 to 1.29 and from 0.12 to 0.15 [mu]mol/g wet weight, respectively. These observations suggest that there is an accelerated degradation of purine nucleotides to the precursors of uric acid in skeletal muscle during vigorous exercise.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23305/1/0000243.pd