Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Segmentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1986

Turnover of palmitate, arachidonate and glycerol in phospholipids of rat rod outer segments.

Rat retinas were intravitreally labeled with [3H]palmitic acid, [3H]arachidonic acid or [3H]glycerol to study the turnover of the component parts of the major phospholipids in rod outer segments at times ranging from 2 hr to 12 days post injection. Rod outer-segment and retinal debris fractions were extracted and the major phospholipids separated by two-dimensional thin-layer chromatography. In darkness, [3H]glycerol rapidly labeled phosphatidylinositol in both rod outer-segment and retinal debris fractions. The label in phosphatidylinositol subsequently decreased dramatically, demonstrating a rapid turnover of phosphatidylinositol with a half-life of less than 1 day. Phosphatidylcholine and phosphatidylethanolamine were maximally labeled by glycerol in the retinal debris at the 2-hr time-point and were maximally labeled in rod outer segments between 1 and 5 days post injection, with somewhat longer residence times in the rod outer segments. Phosphatidylserine showed a lag in initial labeling in both rod outer-segment and retinal debris fractions indicating that this phospholipid is not a major precursor of phosphatidylcholine and phosphatidylethanolamine in rat retinas. [3H]Palmitate and [3H]arachidonate labels were rapidly incorporated into outer-segment phospholipids by 1-2 hr post injection. Eighty per cent of the palmitate label was initially associated with phosphatidylcholine at 2 hr. The total amount of palmitate label in rod outer-segment phosphatidylcholine did not change for 12 days post injection. Outer-segment phosphatidylethanolamine steadily increased in palmitate label throughout the 12-day period, suggesting that phosphatidylethanolamine may be utilized for recapture of palmitate released from breakdown of palmitate esters of rhodopsin or vitamin A or from phospholipids. Arachidonate primarily labeled phosphatidylinositol and phosphatidylcholine of both rod outer segments and retinal debris. The arachidonate label did not decrease dramatically during the first day in phosphatidylinositol as did the glycerol label, indicating that arachidonic acid is reutilized by the retina. Turnover of the individual phospholipids, as measured by a decrease in glycerol labeling of the phospholipid backbone, is more rapid than the loss of palmitate label, indicating that there is extensive reutilization of palmitate in both phosphatidylcholine and phosphatidylethanolamine of the rod outer segment. The data indicate that palmitate derived from many sources could be used by the photoreceptor to acylate rhodopsin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Lactose promotes organized photoreceptor outer segment assembly and preserves expression of photoreceptor proteins in retinal degeneration.

PURPOSE: We have previously shown that lactose promotes the proper assembly of photoreceptor outer segments in the absence of the retinal pigment epithelium (RPE). The purpose of this study was to determine if the difference between organized and disorganized membranes was a variation in the amounts of two structural proteins, opsin and rds/peripherin. METHODS: Eye rudiments were dissected from Xenopus laevis embryos and the RPE was removed prior to culturing in the following media: Niu-Twitty medium; Niu-Twitty with mannose; Niu-Twitty with lactose. Controls included retinas that matured in vitro with an adherent RPE. Photoreceptor ultrastructure was evaluated with emphasis on outer segment membrane organization. The relative amounts of opsin and rds/ peripherin, two outer segment-specific proteins, were determined, as were their immunolabeling patterns. RESULTS: In control retinas, outer segments were composed of stacked, flattened membranous saccules. Opsin labeling of rod outer segments was very dense, indicative of normally organized disc membranes, and rds/peripherin labeling was heavy at the outer segment disc periphery and incisures. In the absence of the RPE, a whorl-like profile of outer segments is present in what would be the sub-retinal space. Opsin immunolabeling was patchy and disorganized. Immunolabeling of rds/peripherin was present, but in a disorderly array. Mannose showed no protective effect. In contrast, lactose promoted the formation of organized outer segments and allowed for near normal expression of both photoreceptor markers. In retinas with disorganized outer segments, the expression of opsin is downregulated while the expression of rds/peripherin is maintained or upregulated. CONCLUSIONS: Lactose protects against the retinal degeneration induced by RPE removal by preserving the outer segment structure and the photoreceptor immunolabeling patterns. It also maintains constant the relative amounts of opsin and rds/peripherin. It is possible that in degenerating retinas, photoreceptors upregulate rds/peripherin expression in attempt to provide additional support for the proper folding of nascent membranes, however this is insufficient to permit organization of the photoreceptor outer segments. Our results suggest that rescue-effect of lactose is mediated by a non-rds/peripherin related mechanism.

Animals↗
PubMed1998

Altered patterns of gene expression in Tribolium segmentation mutants.

Embryos homozygous for the godzilla, jaws, or kraken mutations of Tribolium castaneum have characteristic defects in segmentation. Here, we examine the expression of Tribolium genes homologous to Drosophila segmentation genes in these mutants to define similarities and differences in the process of segmentation in the two insects. The godzilla mutation disrupts segmentation and alters the expression of Even-skipped (Eve) throughout the germ band. godzilla, therefore, acts at an early step in the segmentation gene hierarchy; the evidence suggests it could be the Tribolium homologue of the eve gene. The jaws mutation causes deletion of most of the abdomen; this defect appears to be correlated with the failure of Eve to resolve into a striped pattern of expression, jaws also causes homeotic transformations in the thorax and the first abdominal segment; this transformation is accompanied by ectopic expression of the homeotic gene maxillopedia in the transformed segments. The kraken mutant disrupts patterning within each segment and, like Drosophila segment polarity mutants, disrupts the maintenance of the normal expression domain of Engrailed. This analysis suggests that late stages of segmentation are similar in Tribolium and Drosophila, although there are clear differences in early steps of segmentation in the two insects.

Animals↗
PubMed1995

Collagen fibrillogenesis in situ: fibril segments undergo post-depositional modifications resulting in linear and lateral growth during matrix development.

Elucidating how collagen fibril growth is regulated is important in determining how tissues are assembled. Fibrils are deposited as segments. The growth of these segments is an important determinant of tissue architecture, stability, and mechanical attributes. Fibril segments were isolated from developing tendons and their structure characterized. The post-depositional changes leading to linear and lateral growth of fibrils also were examined. Segments extracted from 14-day chicken embryo tendons had a mean length of 29 microns. The segments were asymmetric, having a short and a long tapered end. Most of the segments were centrosymmetric with respect to molecular packing. Segments extracted from 12- to 16-day tendons had the same structure, but mean segment length increased incrementally due to the addition of an increasingly large population of longer segments. At 17 days of development there was a precipitous increase in segment length. The morphological data indicate that the increase in length was the result of lateral associations among adjacent segments. Analysis demonstrated that this fibril growth was associated with a significant decrease in fibril associated decorin. Using immunoelectron microscopy, decorin was seen to decrease significantly at 18 days of development. When decorin content was biochemically determined, a decrease also was observed. Decorin mRNA also decreased relative to fibrillar collagen mRNA during the same period. These data support the hypothesis that a decrease in fibril-associated decorin is necessary for fibril growth associated with tissue maturation. Growth through post-depositional fusion allows for appositional and intercalary growth and would be essential for normal development, growth, and repair.

Animals↗
PubMed2005

The centipede Strigamia maritima: what it can tell us about the development and evolution of segmentation.

One of the most fundamental features of the body plan of arthropods is its segmental design. There is considerable variation in segment number among arthropod groups (about 20-fold); yet, paradoxically, the vast majority of arthropod species have a fixed number of segments, thus providing no variation in this character for natural selection to act upon. However, the 1000-species-strong centipede order Geophilomorpha provides an exception to the general rule of intraspecific invariance in segment number. Members of this group, and especially our favourite animal Strigamia maritima, may thus help us to understand the evolution of segment number in arthropods. Evolution must act by modifying the formation of segments during embryogenesis. So, how this developmental process operates, in a variable-segment-number species, is of considerable interest. Strigamia maritima turns out to be a tractable system both at the ecological level of investigating differences in mean segment number between populations and at the molecular level of studying the expression patterns of developmental genes. Here we report the current state of play in our work on this fascinating animal, including our recent finding of a double-segment periodicity in the expression of two Strigamia segmentation genes, and its possible implications for our understanding of arthropod segmentation mechanisms in general.

Animals↗
PubMed1991

Segment-specific modifications of a neuropeptide phenotype in embryonic neurons of the moth, Manduca sexta.

We have studied differences in the development of segmentally homologous neurons to identify factors that may regulate a neuropeptide phenotype. Bilaterally paired homologs of the peripheral neuron L1 were identified in the thoracic and abdominal segments in embryos of the moth Manduca: each bipolar neuron arises at a stereotyped location and, at 40% of embryogenesis, projects its major process within the transverse nerve of its own segment. Shortly after the initiation of axonogenesis (approximately 41%), L1 homologs in all but the prothoracic segment (T1) were labelled specifically by an antiserum to the molluscan neuropeptide Phe-Met-Arg-Phe-NH2 (authentic FMRFamide). Levels of peptide-immunoreactivity (IR) were comparable in all such segmental homologs up to the approximately 60% stage of embryogenesis, whereupon two distinct levels of peptide IR were displayed: homologs in the three most rostral segments (T2, T3, and A1; [abdominal segment 1]) showed high levels and were called Type I L1 neurons; homologs in the more caudal segments (A2-A8) typically showed low levels of IR and were called Type II L1 neurons. This segment-specific difference represented mature differentiated states and was retained in postembryonic stages. Intracellular dye fills of embryonic L1 neurons revealed that the morphogenesis of the Type I and II L1 neuron homologs was similar until approximately 48% of embryogenesis; thereafter it differed in two salient ways: (1) the cell bodies of Type II L1 neurons migrated approximately 150 microns laterally from their point of origin, and (2) the distal processes of the Type II L1 neurons contacted the heart, whereas those of Type I L1 neurons did not. Ultrastructural studies of both mature and developing L1 homologs showed that the FMRFamide-like antigen(s) localized specifically to secretory granules. Further, whereas the secretory granules in segmental homologs appeared similar initially (i.e., at approximately 50% of development), following the establishment of segment-specific differences, secretory granules found in mature Type I and II L1 neurons were cell type-specific.

Animals↗
PubMed2004

Longitudinal health-related quality of life after mandibular resection for oral cancer: a comparison between rim and segment.

BACKGROUND: Mandibular resection for oral cancer is often necessary to achieve an adequate margin of tumor clearance. Segmental mandibulectomy has been associated with a poor health-related quality of life (HRQOL), particularly before composite free tissue transfer to reconstruct the defect. Little is published in the literature contrasting the subjective deficit of segmental compared with rim resection. The aim of this study was to use a validated head and neck HRQOL questionnaire to compare rim and segmental mandibular resection in patients having primary surgery for oral cancer. METHOD: There were 224 consecutive patients between 1995 and 1999 who were treated by primary surgery for oral squamous cell carcinoma. One hundred twenty-tree had no mandibular resection, 44 had a rim resection, and 57 had a segmental resection. The University of Washington Quality of life questionnaire (UW-QOL) was administered before treatment, at 6 months, 12 months and after 18 months. RESULTS: Preoperatively, patients undergoing segmental resection reported significantly more pain, chewing problems, and a lower composite UW-QOL score. Postoperatively, the segment group tended to score worse at all time points, particularly in appearance, swallowing, recreation, and chewing; however, the difference between rim and segment was only seen in smaller resections without adjuvant radiotherapy. Little difference was seen between rim or segment for tumors < 4 cm with radiotherapy and between rim and segments for tumors > 4 cm. CONCLUSION: After segmental mandibulectomy and reconstruction using composite free tissue transfer, the UW-QOL scores were relatively good. The only 2 difference between rim and segments was noted in the small resections without radiotherapy, and some of this was reflected in differences at baseline.

Aged↗
PubMed1992

Biomechanical effect of a two-segment anterior cruciate ligament graft with separate femoral attachments and differing levels of prescribed load sharing.

The objective of this study was to analyze the biomechanical effect of varying the level of prescribed load sharing between two segments of an anterior cruciate ligament (ACL) graft, and of separating the femoral attachments of these segments. Total anterior-posterior (AP) laxity was measured using an instrumented spatial linkage. Forces in graft segments were measured using buckle transducers. The two-segment graft was formed using the middle third of the patellar tendon with bone blocks and a synthetic augmentation device. Proximal fixation was obtained using a fixture which allowed changing the individual locations of the femoral attachments of the tendon and augmentation segments. Distal fixation was achieved using a force-setting device which allowed the loads in each segment to be set to prescribed levels. Total graft force, load sharing, and total AP laxity were recorded during the application of 100-N AP tibial loads at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 110 degrees flexion, for various combinations of load sharing set at extension and locations of femoral attachment sites. The load sharing, total graft force, and AP laxity during AP loading at the five test flexion angles were not significantly affected by changing the prescribed level of load sharing set at extension for a given femoral attachment configuration. However, varying the separate hole locations of the graft segments for a given level of load sharing significantly affected load sharing, total graft force, and AP laxity. If the tendon graft was located posteriorly (on the medial surface of the lateral femoral condyle) and the augmentation segment proximally, the augmentation carried a greater portion of the total force in flexion. If the augmentation segment was changed to a more posterosuperior location and the tendon posteroinferior, the tendon carried a higher percentage of the total force in flexion. AP laxity in most reconstruction states was significantly greater than in the normal joint with an intact ACL. The nature of the load sharing between the graft segments under AP tibial load over the flexion range can be controlled by the appropriate choice of the segments' femoral attachment locations.

Analysis of Variance↗
PubMed1984

The tail flattening reflex in Lumbricus: reconstitution after tail amputation and modifications in segmental nerve roots.

On stimulation of the head, the caudal 20-30 segments of intact earthworms exhibit a marked dorso-ventral flattening reflex which is an element of the escape response. When the tail is removed this reflex is reconstituted gradually in segments anterior to the amputation level without regeneration of new tail segments. It takes longer to reestablish the flattening if larger parts of the body are cut off, but after 60 days p.o. all animals regained the full response independent of the number of segments amputated. Extirpation of three consecutive ganglia from the ventral nerve cord also suffices to develop flattening anterior to the operated segments, but the reaction is less pronounced and appears later than after tail amputation. Moreover, it vanishes at the same time the normal tail flattening is observed again, presumably after regeneration across the gap in the cord. In different regions of the body, area and perimeter distributions of transversely sectioned axons in the three pairs of segmental nerves (SN I-III) of the cord were measured. Characteristic changes along the length of the animal were found for SN I and SN III. In tail segments the axonal size distributions are more variable than "typical" segments. The flattening reflex is mediated by axons in SN III (Pallas and Drewes, 1981). In body segments having reconstituted behavioral characteristics of the lost tail segments, the area of the largest axons and the general size distribution in SN III approximate those found in normal tail segments.

Animals↗
PubMed1984

Differentiation of the segmented tubular nephron and excretory duct during lamprey metamorphosis.

The tubular portion of the adult lamprey nephron differentiates into various morphologically distinct segments during the seven stages of metamorphosis. At stage 1, a rudimentary nephron unit (RNU) originates from a nephrogenic mass attached to the peritoneum and elongates to become associated at its distal end with the archinephric (excretory) duct. The rapidly dividing cells show little sign of differentiation. Separation of the RNU from the peritoneum in stage 2 is first accompanied by widening of lateral intercellular spaces and then eventually by the formation of a small lumen at the proximal end. Cells surrounding a portion of this lumen show early signs of ciliogenesis and hence are located in the position of the presumptive neck segment. The distal end of the stage 2 RNU contains an electron-dense material in an enlarged intercellular space and the cells make non-junctional contact with the archinephric duct. The larval cells of the latter structure are either lost during degeneration and desquamation or are transformed into adult cells. By the end of stage 3 replication of basal bodies and formation of cilia has resulted in the appearance of a ciliated neck segment while numerous microvilli extending into a narrow lumen mark the position of the proximal segment. Furthermore, most of the distal portion of the newly formed tubule possesses a lumen containing a compact mass of material likely secreted by the cells during lumen formation. This presumptive distal segment terminates in the transforming epithelium of the archinephric duct as a presumptive connecting or collecting segment. Fully differentiated neck and proximal segments are present in stage 4 with the latter having a complete apparatus for endocytosis but the distal segment shows only early signs of differentiation of the smooth tubular network. This network appears to arise as an expanded surface area of the plasma membrane. Stage 5 is characterized by elongation of the proximal portion of the tubule, expansion of the tubular network in distal cells, and the identification of a collecting segment. The last two stages show no further major differentiation of the segments. The early differentiation of tubular segments in the adult lamprey nephron likely reflects the immediate physiological needs of this organism as the larval kidney undergoes regression. The potential of the developing kidney of adult lampreys as a source of information on morphogenesis of microvilli, the endocytotic apparatus, mitochondria, and a smooth tubular network is discussed. It appears that the archinephric duct and non-nephrogenic mesenchyme may play some role in tubulogenesis in lampreys.

Animals↗
PubMed1983

Effects of muscle model parameter dispersion and multi-loop segmental interaction on the neuromuscular system performance.

The effects of parameter dispersion among motor units on the neuromuscular system performance as well as interaction between muscle segments and spinal cord mechanisms are investigated. Elementary components of the system are modeled to simulate with simple models their input-output characteristics. A leaky SS-IPFM encoder with a time-dependent threshold simulates the motor-neuron encoding characteristics. An amplitude and time dependent nonlinear model represent the motor unit mechanical output to neuronal input relationship. The dispersion of parameters in the components of the whole muscle control model is investigated in the open loop mode. It is shown that the dispersion of parameters in the multi-efferent channels converging on a common tendon provides a spatial filtration generating a smoother muscle force in addition to extending the linear dynamic range compared to a similar system having identical motor units. Muscle segmental interaction is investigated in this distributed model by closing the loop through a coupling matrix, representing afferent-motorneuron interaction on the spinal cord level. A diagonal matrix represents no segmental interaction and a uniform matrix represents a uniform interaction between segments through the muscle spindles and Golgi tendon feedback elements. The close loop simulation studied shows that (a). The type of segmental interaction has little effect on the overall system performance, i.e., range of linerity and stability, which is the result of having a muscle system with a large number of motor units. (b) There are only minor differences in results between the uniform and normal parameter distributions tested. (c) A loop gain of 4 divided by 8 in the distributed model can provide linearity through the full physiological force range. (d) Type of segmental interaction has significant effects on the individual segment. A uniform matrix provides a more stable segment due to the spatial filtration resulting from the segmental interaction, while the diagonal noninteracting matrix shows instabilities on the local segmental level despite global stability. The more realistic exponentially decaying spatial interaction matrix yields both global neuromuscular and local segmental stability with the same linear dynamic range generated with the uniform or diagonal matrices.

Animals↗
PubMed1999

Intraoperative detection of segmental wall motion abnormalities with transesophageal echocardiography.

PURPOSE: To compare two methods of analysis of regional wall-motion (RWM) using transesophageal echocardiography (TEE). METHODS: Thirty patients undergoing coronary artery bypass surgery were studied. The transgastric short axis view at the mid-papillary level was recorded before and after cardiopulmonary bypass. All images were reviewed by an anesthesiologist trained in TEE and an echocardiographer. Regional wall motion was graded: 1 normal, 2 hypokinetic, 3 akinetic, and 4 dyskinetic. The left ventricle was evaluated according to the guidelines of the American Society of Echocardiography using 6-segment, and 4-segment models. Agreement between observers (interobservers), and for one observer at two different moments (intraobservers), for grading each segment was defined as RWM abnormality scores within 1 grade. A wall-motion score index (WMSI), which is the sum of individual scores divided by the number of segments visualized, was calculated. A Bland Altman analysis was used to assess interobserver variability. RESULTS: Agreement between observers occurred in 96% and 94% of the examined segments, using 4- and 6-segment models respectively. Intraobserver agreement was 99% and 97% for the 4- and 6-segment models. The mean differences (bias) of the interobserver variability in grading the segments were 0.04 +/- 0.79 and 0 +/- 0.72 using a 4- or 6-segment model. The mean difference of the interobserver variability in WMSI were -0.05 +/- 0.42 and 0.05 +/- 0.37 using a 4- or a 6-segment model. CONCLUSION: Both methods, using either a 4- or a 6-segment model, result in a high intraobserver and interobserver agreement, and a low interobserver variability.

Coronary Artery Bypass↗
PubMed1997

The influence of movement segment difficulty on movements with two-stroke sequence.

Arm movements in the horizontal plane consisting of two segments were examined to determine whether the difficulty of the second segment influenced the kinematic characteristics of the first segment. The direction of the first segment was an elbow extension movement away from the trunk and remained constant throughout the experiment. The direction of the second segment varied between forearm extension and flexion movements. Based on Fitts' law, two different indexes of difficulty (ID) of the second segment were utilized by changing target size and movement amplitude. The effects of changing ID were examined for two different movement amplitudes. All movements were single-joint movements employing elbow flexion/extension and were recorded by an x-y digitizer. Variations in the ID of the second segment produced context-dependent kinematic changes in the performance of the initial segment. Movement duration increased when the ID was increased by reducing target size for both extension-extension sequence and extension-flexion sequences. Peak velocity also decreased for higher ID targets in the extension-flexion sequence. However, there was an interaction between the ID and movement amplitude in the extension-flexion sequence. In this sequence the duration of movement for the high ID/large movement amplitude condition increased substantially compared with the low ID/small movement amplitude condition. In addition, changing ID of the second segment influenced the time between the two segments (intersegment interval) in the extension-flexion sequence. Collectively, these data suggest that the planning of complex movements is based in part on the accuracy demands of multiple segments of the sequence.

Adult↗
PubMedDate not supplied

Glutamine synthetase activity in rat urine as sensitive marker to detect S3 segment-specific injury of proximal tubule induced by xenobiotics.

The possibility of detecting segment-specific injury of the proximal tubule by means of urinary enzymes was investigated in rats. Urinary glutamine synthetase, an enzyme exclusively localized in the S3 segment, and N-acetyl-beta-D-glucosaminidase, prevalently a S1-S2, but S3 enzyme also, were determined after single treatment with 100 mg/kg body wt. of hexachloro-1:3-butadiene (HCBD; i.p.), toxic for the S3 segment, or 25 mg/kg body wt. of potassium dichromate (s.c.), toxic for the S1-S2 segments. Excretion of total urinary proteins was also measured. In addition, a dose-response relationship was determined between three doses (50, 100 and 200 mg/kg body wt.) of HCBD and glutamine synthetase activity in urine. Glutamine synthetase activity, measured according to a new assay for urine based on modification of methods developed for organs, increased in the urine only when the S3 segment of the proximal tubule was damaged, as demonstrated by histological findings of the kidneys. HCBD caused early excretion of the enzyme related to the necrosis of the S3 segment, whereas potassium dichromate caused a slight increase only when the resulting lesion to this segment (vacuolization) began to develop. On the contrary, N-acetyl-beta-D-glucosaminidase activity showed the peak of excretion 24 and 34 h after treatment with HCBD or potassium dichromate, respectively, according to the histological findings of necrosis of the S3 segment (the former) and vacuolization of the S1-S2 segments (the latter). Excretion of total urinary proteins reached the peak 24 h (HCBD) and 48 h (potassium dichromate) after treatment. HCBD at 200 mg/kg body wt, caused a peak of glutamine synthetase activity in urine 10 h after injection, whereas the peak caused by doses of 50 and 100 mg/kg body wt. occurred 24 h following treatment. The peak of enzyme activity in urine significantly increased with the dose. The results suggest that the measurement of urinary activity of S3 segment-specific enzyme as glutamine synthetase allows us to detect early S3 segment-specific injury of the proximal tubule. In addition, the method for urinary enzyme activity appears sensitive, simple and fast.

Acetylglucosaminidase↗
PubMed2005

Diagnostic usefulness of segmental and linear enhancement in dynamic breast MRI.

The aim of this study was the evaluation of the diagnostic usefulness of ductal or segmental enhancement in dynamic breast MRI. Segmental and ductal enhancement have been established as the breast MRI hallmarks of intraductal breast cancer (DCIS); however, the positive predictive value of this imaging finding is still unknown. In our study, we analysed the overall prevalence of a segmental or a linear enhancement pattern on breast MRI for an unselected cohort of patients. The aim was to evaluate the diagnostic usefulness of segmental or linear enhancement. Second, we asked whether biopsy was necessary also in the absence of mammographic findings suggestive of DCIS. Prospective, consecutive evaluation of 1,003 patients undergoing bilateral dynamic breast MRI. Studies were interpreted by two experienced breast radiologists. A diagnostic or screening two-view mammogram was available for all patients. Biopsy or short-term breast MRI follow-up was recommended for patients showing a segmental or a linear enhancement pattern on breast MRI. The patients' final diagnoses were established by imaging guided excisional or core biopsy or by clinical plus conventional imaging follow-up for a period of 2 years. The prevalence of segmental or linear enhancement was determined for patients with a final diagnosis of benign breast disease compared with those with a diagnosis of breast cancer. One hundred twenty patients had invasive breast cancer, 24 patients had DCIS and 859 patients had unsuspicious breast MRI or benign breast disease. A segmental or a linear enhancement pattern was found for 50/1,003 (5%) patients (17 DCIS, 33 benign breast diseases). Accordingly, the positive predictive value of segmental and linear enhancement is 34% (17/50); the specificity of this criterion is 96% (826/859). For 4/24 (17%) patients, DCIS was visible as segmental or linear enhancement on dynamic breast MRI, whereas no abnormalities were visible on the corresponding mammogram. The overall prevalence of a ductal or a segmental enhancement pattern on breast MRI is low. But this finding has a high specificity and a moderate positive predictive value for intraductal neoplastic changes. We conclude that if segmental or linear enhancement is identified on breast MRI further work-up is necessary. We recommend either direct MR-guided vacuum-assisted core biopsy or short-term follow-up breast MRI within 3 months. If ductal enhancement then persists, MR-guided biopsy should be recommended even in the absence of mammographically visible signs of DCIS.

Biopsy↗
PubMed1997

Segmentation of moving images by the human visual system.

New segments appearing in an image sequence or spontaneously accelerated segments are band limited by the visual system due to a nonperfect tracking of these segments by eye movements. In spite of this band limitation and acceleration of segments, a coarse segmentation (initial segmentation phase) can be performed by the visual system. This is interesting for the development of purely automatic segmentation algorithms for multimedia applications. In this paper the segmentation of the visual system is modelled and used in an automatic coarse initial segmentation. A suitable model for motion processing based on a spectral representation is presented and applied to the segmentation of synthetic and real image sequences with band limited and accelerated moving foreground and background segments.

Algorithms↗
PubMed2006

Residual mobility of instrumented and non-fused segments in thoracolumbar spine fractures.

The surgical management of thoracolumbar fractures presents potential benefits. However, the surgery solve the instability by fusion of mobile segments. We incorporate in our treatment algorithms, the use of restricted arthrodesis at injured levels, regardless of longer instrumentations, as well as the use of non-fused transitory stabilizations, based on the conviction that in non-fused segments without traumatic disc injury, mobility persists once the instrumentation is removed. The goals of this study were to compare the mobility of non-fused segments after hardware removal to a normal range of motion and to find prognostic pre-op imaging patterns. We reviewed 21 consecutive patients who underwent surgery with preservation of mobile segments (non-fused segments included in the construction) in order to recover mobility after removal of instrumentation, performed between 1995 and 2001. All patients were treated by indirect reduction with posterior transpedicular instrumentation. Clinical and radiological outcome was analyzed after an average follow-up of 46.6 months. Satisfactory subjective outcome results were obtained in 94.7%. The dynamic radiological follow-up study showed 75% (21 segments) with normal or decreased range of motion (ROM) and 25% (7 segments) without mobility. The non-fused segments with hardware removal before 10 months of evolution presented a normal or decreased mobility in 83.2% while the segments with hardware removal after 10 months showed 68.8% of mobility. The intervertebral disc (IVD)'s with normal initial MRI morphology preserved their mobility in 81.9%. Complications occurred in four patients: two superficial wound infections and two patients presented a late fracture of one USS Schanz. The results of this study prove that in thoracolumbar fractures, non-fused spinal segments included in pedicular instrumentation maintained mobility in a high percentage once the hardware is removed. 75% of the segments presented a normal or decreased ROM.

Adult↗
PubMed1987

ST segment changes in exercise body surface mapping after myocardial infarction in patients with isolated left anterior descending coronary artery disease.

To investigate the clinical significance of exercise-induced ST segment elevation and ST segment depression after myocardial infarction (MI), we performed 87-lead ECG mapping after previous anterior infarction in 24 patients with isolated left anterior descending coronary artery disease before and 1.5 minutes after treadmill exercise. Thirteen patients showed ST segment elevation only, seven patients showed both ST segment elevation and depression, and four patients showed ST segment depression only. ST segment elevation most frequently occurred in the left anterior chest leads corresponding to the QS area, and ST segment depression developed in the left lower chest and left lower back leads. There was good correlation between the number of lead points showing ST segment elevation (nSTe) after exercise and the number of lead points showing QS waves (nQS) before exercise (r = 0.65). nSTe was also correlated with the asynergy index (r = 0.43). These findings suggest that ST segment elevation is mainly the result of aggravation of wall motion abnormalities of the infarcted myocardium. Body surface distribution of ST segment depression was similar to that in effort angina pectoris without MI. We conclude that exercise-induced ST segment depression in MI mainly reflects the ischemia of the surviving myocardium of small infarcts or the peripheral area of large infarcts.

Adult↗