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 901 records · Page 50Linked to original sources
PubMed2000

Latitudinal cline in segment number in an arthropod species, Strigamia maritima.

Arthropods vary more than 30-fold in segment number. The evolutionary origins of differences in segment number among species must ultimately lie in intraspecific variation. Yet paradoxically, in most groups of arthropods, the number of segments is fixed for each species and shows no intra- or interpopulation variation at all. Geophilomorph centipedes are an exception to this general rule, and exhibit intraspecific variation in segment number, with differences between individuals being determined during embryonic development and hence independent of population age structure. Significant differences in segment number between different geographical populations of the same species have been previously reported, but insufficient sampling has been conducted to reveal any particular geographical pattern. Here, we reveal a latitudinal cline in segment number in the geophilomorph species Strigamia maritima: segment number in British populations decreases with distance north. This is the first such cline to be reported for any centipede species; indeed as far as we are aware it is the first such cline reported for any arthropod species. In vertebrates, fish are known to exhibit a latitudinal cline in segment number, but interestingly, this is in the opposite direction; fish add segments with increasing latitude, centipedes subtract them.

Animals↗
PubMed1992

Strain-specific selection of genome segments in avian reovirus coinfections.

To determine whether selection of genome segments in coinfections is strain-specific, chicken embryo fibroblasts were coinfected with avian reovirus strain 883 and one of three other avian reovirus strains (176, S1133 and 81-5). Viral progeny from each coinfection (883 x 176, 883 x S1133 or 883 x 81-5) was serially passaged at a low m.o.i. The electropherotypes of the coinfection progeny and those of the plaque-derived clones obtained from passages 1 and 20 were analysed. Two 883 segments (M2 and S2) were found to be selected in the 883 x 176 coinfection, three 883 segments (M2, M3 and S2) in the 883 x S1133 coinfection, and only one 883 segment (M3) in the 883 x 81-5 coinfection, i.e. different 883 genome segments were selected in the three coinfections. It was, therefore, concluded that selection of genome segments in a coinfection of a given cell line is virus strain-specific. The selection of genome segments in coinfections was shown to be due to enhanced infectivity of the reassortants that were formed in the coinfections. In addition, defective interfering particles that lack the S1 segment were identified in the 883 x 81-5 coinfection progeny following serial passage. Selection of genome segment(s) in coinfections as described herein may have potential importance on the effect and production of divalent or multivalent vaccines.

Animals↗
PubMed2002

Effects of nonuniform segment deformation on the constitutive relation of polymeric solids.

A polymeric solid is modeled as a network of beads and strings. Beads in the polymer are divided into bead groups represented by the segment end points. Based on the equation of motion for each bead in the system, a macroscopic equation of motion for the polymer is derived. Velocity fluctuations of beads result in a pressure, the isotropic component of the stress, in the polymer. Interaction forces transmitted through segments connected to bead groups are the major source of the stress in the polymer. The tendency of segments to achieve their minima in Helmholtz free energy results in thermal elasticity of the polymer. Compared to the time scale of these segment interactions, other interactions among beads groups are short in time, therefore, result in a viscous stress. The motion of an average segment is modeled as an elastic spring immersed in a viscous fluid. The inertia of the segment is neglected because the viscous force is much larger than the inertial force. The governing equation for the deformation of the average segment is found to be a diffusion equation representing the balance between the viscous force and the elastic force in the segment. If the time scale of the macroscopic deformation is short compared to that of the deformation diffusion, the application of forces at both ends results in nonuniform deformation of the segment, which diffuses from the ends toward the center. This diffusion leads to relaxation of the macroscopic stress which we represent by a history integral. The kernel in the integral is asymptotic to 1/sqrt[t] for a short time t, and is asymptotic to an exponentially decaying function for a long time t, in which t is the elapsed time from initiation of the deformation. This theoretically predicted kernel is observed in experiments conducted at constant temperature.

Journal Article↗
PubMed1999

Elastic model-based segmentation of 3-D neuroradiological data sets.

This paper presents a new technique for the automatic model-based segmentation of three-dimensional (3-D) objects from volumetric image data. The development closely follows the seminal work of Taylor and Cootes on active shape models, but is based on a hierarchical parametric object description rather than a point distribution model. The segmentation system includes both the building of statistical models and the automatic segmentation of new image data sets via a restricted elastic deformation of shape models. Geometric models are derived from a sample set of image data which have been segmented by experts. The surfaces of these binary objects are converted into parametric surface representations, which are normalized to get an invariant object-centered coordinate system. Surface representations are expanded into series of spherical harmonics which provide parametric descriptions of object shapes. It is shown that invariant object surface parametrization provides a good approximation to automatically determine object homology in terms of sets of corresponding sets of surface points. Gray-level information near object boundaries is represented by 1-D intensity profiles normal to the surface. Considering automatic segmentation of brain structures as our driving application, our choice of coordinates for object alignment was the well-accepted stereotactic coordinate system. Major variation of object shapes around the mean shape, also referred to as shape eigenmodes, are calculated in shape parameter space rather than the feature space of point coordinates. Segmentation makes use of the object shape statistics by restricting possible elastic deformations into the range of the training shapes. The mean shapes are initialized in a new data set by specifying the landmarks of the stereotactic coordinate system. The model elastically deforms, driven by the displacement forces across the object's surface, which are generated by matching local intensity profiles. Elastic deformations are limited by setting bounds for the maximum variations in eigenmode space. The technique has been applied to automatically segment left and right hippocampus, thalamus, putamen, and globus pallidus from volumetric magnetic resonance scans taken from schizophrenia studies. The results have been validated by comparison of automatic segmentation with the results obtained by interactive expert segmentation.

Algorithms↗
PubMed2005

Spatiotemporal video segmentation based on graphical models.

This paper proposes a probabilistic framework for spatiotemporal segmentation of video sequences. Motion information, boundary information from intensity segmentation, and spatial connectivity of segmentation are unified in the video segmentation process by means of graphical models. A Bayesian network is presented to model interactions among the motion vector field, the intensity segmentation field, and the video segmentation field. The notion of the Markov random field is used to encourage the formation of continuous regions. Given consecutive frames, the conditional joint probability density of the three fields is maximized in an iterative way. To effectively utilize boundary information from the intensity segmentation, distance transformation is employed in local objective functions. Experimental results show that the method is robust and generates spatiotemporally coherent segmentation results. Moreover, the proposed video segmentation approach can be viewed as the compromise of previous motion based approaches and region merging approaches.

Algorithms↗
PubMed2004

Performance-based classifier combination in atlas-based image segmentation using expectation-maximization parameter estimation.

It is well known in the pattern recognition community that the accuracy of classifications obtained by combining decisions made by independent classifiers can be substantially higher than the accuracy of the individual classifiers. We have previously shown this to be true for atlas-based segmentation of biomedical images. The conventional method for combining individual classifiers weights each classifier equally (vote or sum rule fusion). In this paper, we propose two methods that estimate the performances of the individual classifiers and combine the individual classifiers by weighting them according to their estimated performance. The two methods are multiclass extensions of an expectation-maximization (EM) algorithm for ground truth estimation of binary classification based on decisions of multiple experts (Warfield et al., 2004). The first method performs parameter estimation independently for each class with a subsequent integration step. The second method considers all classes simultaneously. We demonstrate the efficacy of these performance-based fusion methods by applying them to atlas-based segmentations of three-dimensional confocal microscopy images of bee brains. In atlas-based image segmentation, multiple classifiers arise naturally by applying different registration methods to the same atlas, or the same registration method to different atlases, or both. We perform a validation study designed to quantify the success of classifier combination methods in atlas-based segmentation. By applying random deformations, a given ground truth atlas is transformed into multiple segmentations that could result from imperfect registrations of an image to multiple atlas images. In a second evaluation study, multiple actual atlas-based segmentations are combined and their accuracies computed by comparing them to a manual segmentation. We demonstrate in both evaluation studies that segmentations produced by combining multiple individual registration-based segmentations are more accurate for the two classifier fusion methods we propose, which weight the individual classifiers according to their EM-based performance estimates, than for simple sum rule fusion, which weights each classifier equally.

Algorithms↗
PubMed2006

Validation of bone segmentation and improved 3-D registration using contour coherency in CT data.

A method is presented to validate the segmentation of computed tomography (CT) image sequences, and improve the accuracy and efficiency of the subsequent registration of the three-dimensional surfaces that are reconstructed from the segmented slices. The method compares the shapes of contours extracted from neighborhoods of slices in CT stacks of tibias. The bone is first segmented by an automatic segmentation technique, and the bone contour for each slice is parameterized as a one-dimensional function of normalized arc length versus inscribed angle. These functions are represented as vectors within a K-dimensional space comprising the first K amplitude coefficients of their Fourier Descriptors. The similarity or coherency of neighboring contours is measured by comparing statistical properties of their vector representations within this space. Experimentation has demonstrated this technique to be very effective at identifying low-coherency segmentations. Compared with experienced human operators, in a set of 23 CT stacks (1,633 slices), the method correctly detected 87.5% and 80% of the low-coherency and 97.7% and 95.5% of the high coherency segmentations, respectively from two different automatic segmentation techniques. Removal of the automatically detected low-coherency segmentations also significantly improved the accuracy and time efficiency of the registration of 3-D bone surface models. The registration error was reduced by over 500% (i.e., a factor of 5) and 280%, and the computational performance was improved by 540% and 791% for the two respective segmentation methods.

Algorithms↗
PubMed2005

Color clustering and learning for image segmentation based on neural networks.

An image segmentation system is proposed for the segmentation of color image based on neural networks. In order to measure the color difference properly, image colors are represented in a modified L*u* v* color space. The segmentation system comprises unsupervised segmentation and supervised segmentation. The unsupervised segmentation is achieved by a two-level approach, i.e., color reduction and color clustering. In color reduction, image colors are projected into a small set of prototypes using self-organizing map (SOM) learning. In color clustering, simulated annealing (SA) seeks the optimal clusters from SOM prototypes. This two-level approach takes the advantages of SOM and SA, which can achieve the near-optimal segmentation with a low computational cost. The supervised segmentation involves color learning and pixel classification. In color learning, color prototype is defined to represent a spherical region in color space. A procedure of hierarchical prototype learning (HPL) is used to generate the different sizes of color prototypes from the sample of object colors. These color prototypes provide a good estimate for object colors. The image pixels are classified by the matching of color prototypes. The experimental results show that the system has the desired ability for the segmentation of color image in a variety of vision tasks.

Algorithms↗
PubMed2006

Context-based segmentation of image sequences.

We describe an algorithm for context-based segmentation of visual data. New frames in an image sequence (video) are segmented based on the prior segmentation of earlier frames in the sequence. The segmentation is performed by adapting a probabilistic model learned on previous frames, according to the content of the new frame. We utilize the maximum a posteriori version of the EM algorithm to segment the new image. The Gaussian mixture distribution that is used to model the current frame is transformed into a conjugate-prior distribution for the parametric model describing the segmentation of the new frame. This semisupervised method improves the segmentation quality and consistency and enables a propagation of segments along the segmented images. The performance of the proposed approach is illustrated on both simulated and real image data.

Algorithms↗
PubMed1985

Investigations into the possible regulation of negative gravitropic curvature in intact Avena sativa plants and in isolated stem segments by ethylene and gibberellins.

Using Avena sativa L. cv. Victory oat seedlings and excised p-1 stem segments (including the p-1 and p-2 internodes) the effect of exogenously supplied ethylene and the removal of ethylene on internodal extension and gravitropic bending was assessed. Similarly, the ability of the excised system to respond to gravistimulation was assessed in the presence of inhibitors of ethylene action (AgNO3) and ethylene synthesis (3,5-diiodo-4-hydroxybenzoic acid and benzyl isothiocyanate; BITC). The production of ethylene from both intact and excised systems was also measured from 0 to 48 h after gravistimulation, relative to vertical controls. Although gravitropic curvature is initiated, and indeed enters the most rapid phase of upward bending during the first 6 h, there is no difference in ethylene production between vertical and geostimulated plants during this period. The ethylene production of gravistimulated plants rises sharply to a maximum at 24 h, then decreases steeply to almost the control level by 48 h, at which time the rate of upward curvature is diminishing. Neither the addition nor removal of ethylene, nor the addition of inhibitors affecting ethylene-action (AgNO3) or synthesis (DIHB) influence gravitropic bending or internodal extension in excised segments. Although the ethylene synthesis inhibitor BITC slowed down the rate of upward bending, this effect could not be reversed by addition of ethylene. We conclude that the burst in ethylene production that develops in leaf-sheath bases (pulvini) after they have started to curve upwards is not primary to the induction of curvature. We further suggest that ethylene has no major effect or role in the induction of upward bending after gravistimulation. The metabolism of high specific activity gibberellin A1 ([3H]-GA1) in the excised system was assessed during 1, 2 and 4 h of gravistimulation. Changes in endogenous GAs and GA metabolism have been shown previously to be correlated (at the later stages) with gravistimulated bending in intact Avena shoots. The excised segments "leaked" free [3H]-GAs and [3H]-GA glucosyl conjugate-like substances into the bathing medium, and this was a confounding factor. Nevertheless, gravistimulated stem segments, and especially the bottom half of the segment, were significantly less leaky then vertical segments. Thus, just 1 h after gravistimulation, bottom segment halves retained 22% more precursor [3H]-GA1, 36% more free [3H]-GA-like metabolites, and 48% more [3H]-GA glucosyl conjugate-like metabolites than vertical segments. In contrast, the 1 h gravistimulated top halves retained slightly less (1-4%) precursor [3H]-GA1 and free [3H]-GA metabolites, but 21% more [3H]-GA glucosyl conjugate-like radioactivity than vertical segments.

Avena↗
PubMed2006

Inertial properties of hominoid limb segments.

Quantitative, accurate data regarding the inertial properties of body segments are of paramount importance when developing musculo-skeletal locomotor models of living animals and, by inference, their ancestors. The limited number of available primate cadavers, and the destructive nature of the post-mortem, result in such data being very rare for primates. This study builds on the work of Crompton et al. (Am. J. Phys. Anthropol. 1996, 99, 547-570) and reports inertial properties of the body segments of gorillas, chimpanzees, orangutans and gibbons. Segment mass, centre of mass and the radius of gyration of five ape cadavers were measured using a complex-pendulum technique and compared with the results derived from external measurements of segment lengths and diameters on the same animals. With additional data from external measurements of eight more hominoid cadavers, and published data, intergeneric differences between the inertial properties and the distribution of mass between limb segments are analysed and related to the locomotor habits of the species. We found that segment inertial properties show extensive overlap between ape genera as a result of large interindividual variation. Segment mass distribution also overlaps between apes and humans, with the exception of the shank segment. However, owing to a different distribution of mass between the limb segments, the centre of mass of both the arms and the legs is located more distally in apes than in humans, and the natural pendular period of ape forelimbs is larger than that of the hindlimbs. This suggests that, in contrast to the limbs of cursorial mammals and cercopithecoid primates, hominoid limbs are not optimized for efficiency in quadrupedal walking, but rather reflect a compromise between various locomotor modes. Common chimpanzees may have secondarily evolved a more efficient quadrupedal gait.

Animals↗
PubMedDate not supplied

Expression of estrogen-receptor related receptors in amphioxus and zebrafish: implications for the evolution of posterior brain segmentation at the invertebrate-to-vertebrate transition.

Summary The evolutionary origin of vertebrate hindbrain segmentation is unclear since the amphioxus, the closest living invertebrate relative to the vertebrates, possesses a hindbrain homolog that displays no gross morphological segmentation. Three of the estrogen-receptor related (ERR) receptors are segmentally expressed in the zebrafish hindbrain, suggesting that their common ancestor was expressed in a similar, reiterated manner. We have also cloned and determined the developmental expression of the single homolog of the vertebrate ERR genes in the amphioxus (AmphiERR). This gene is also expressed in a segmented manner in a region considered homologous to the vertebrate hindbrain. In contrast to the expression of amphioxus islet (a LIM-homeobox gene that also labels motoneurons), AmphiERR expression persists longer in the hindbrain homolog and does not later extend to additional posterior cells. In addition, AmphiERR and one of its vertebrate homologs (ERRalpha) are expressed in the developing somitic musculature of amphioxus and zebrafish, respectively. Altogether, our results are consistent with fine structural evidence suggesting that the amphioxus hindbrain is segmented, and indicate that chordate ERR gene expression is a marker for both hindbrain and muscle segmentation. Furthermore, our data support an evolution model of chordate brain segmentation: originally, the program for anterior segmentation in the protochordate ancestors of the vertebrates resided in the developing axial mesoderm which imposed reiterated patterning on the adjacent neural tube; during early vertebrate evolution, this segmentation program was transferred to and controlled by the neural tube.

Amino Acid Sequence↗
PubMed1981

Effects of malalignment of teeth in the anterior segments on plaque accumulation.

The importance of malposition of teeth and plaque accumulation is still not established. The purpose of this study was to measure plaque accumulation on individual malpositioned teeth for comparison with contralateral nonmalpositioned teeth. Furthermore, the distribution of plaque in the anterior segments was measured and compared between aligned and nonaligned segments and the total mouth plaque score. Plaque scores and contact point indices were recorded from a total of 87 subjects of which 20 were drawn from dental and ancillary students and 67 from randomly chosen patients. For anterior teeth, in both groups significantly more plaque accumulated on malpositioned teeth compared with contralateral nonmalpositioned teeth. For the right-handed subjects (83), mean plaque scores for malpositioned teeth were greater than for nonmalpositioned teeth whether the malpositioned tooth was on the right or left of the anterior segment. This difference was significant in the patient group. The contact point index of the anterior segments correlated only with plaque accumulation in those subjects with a plaque index of less than 1. Upper and lower anterior segment plaque scores correlated with total mouth scores in both groups. However, the upper anterior segment scores had significantly less plaque than the total mouth score irrespective of the presence or absence of tooth malalignment, whereas the lower anterior segment always had significantly higher plaque scores than the total mouth score, irrespective of the presence or absence of malalignment. Finally, lower segments, whether aligned or malaligned, had significantly more plaque than upper anterior segments which were aligned or malaligned.

Adolescent↗
PubMed1978

Histochemical enzyme activity correlated to the structural segmentation of the proximal convoluted tubule in salt-depleted and salt-loaded rat kidneys.

In salt-depleted and salt-loaded rat kidneys a study was made of the structural segmentation of the proximal convoluted tubule (PCT) and the histochemical activity of non-specific acid and alkaline phosphatases and succinate dehydrogenase in the same segments. No quantitative structural or segmental alterations were observed, but significant changes in enzyme activity occured. These comprised: 1) A decrease in activity of acid phosphatase in segment 1 and the transitional zone in salt-depleted kidneys, and an increase in enzyme activity in segment 2 in salt-loaded kidneys. 2) a decrease in alkaline phosphatase activity in segment 2 in both salt-depleted and salt-loaded kidneys and 3) a decrease in succinate dehydrogenase activity in segment 2 in salt-depleted kidneys, and an increase in activity in the same segment in salt-loaded kidneys. Thus long-term variation in sodium intake are followed by segment-correlated variations in the activity of acid and alkaline phosphatase and succinate dehydrogenase in the PCT.

Acid Phosphatase↗
PubMed1991

Dyssynchrony of segment shortening in the anterior wall of the feline left ventricle.

Non-uniformity of regional contraction may be both spatial and temporal. This study was undertaken to deal with the temporal aspects of shortening and to quantify non-uniformity with regard to timing. Nine cats were anaesthetized and artificially ventilated. Two pairs of ultrasonic crystals were situated in the anterior midwall of the left ventricle to measure regional shortening. One pair, longitudinal segment, was oriented to align with midwall fibres. The other pair, transverse segment, was placed perpendicular to the first one. Registrations in control state, during caval occlusion, and during aortic constriction were carried out with and without isoprenaline infusion. Cyclic events were analysed in terms of phase angle, 0-2 pi representing one heart cycle. Transverse segments showed marked shift of duration of shortening, from 1.19 pi +/- 0.06 pi (mean +/- SEM) in the control state to 0.40 pi +/- 0.14 pi during caval occlusion with isoprenaline infusion. Duration of shortening of longitudinal segments showed less prominent shift with mean values between 1.38 pi and 1.11 pi. Regional uniformity of timing, expressed as synchronization index, varied markedly with interventions (P less than 0.0005). Dyssynchrony was most prominent during caval occlusion with mean values less than 0.6. A simple model of force generation for the two segments visualizes that segment shortening of the transverse segment is of shorter duration than the longitudinal segment and a common mechanism for temporal and spatial non-uniformity within a region could be elaborated. This study quantifies both the time course of shortening and temporal non-uniformity of two cross-oriented segments within the same myocardial region.

Animals↗
PubMed1997

Solar UVB dosimetry by amplification of short and long segments in phage lambda DNA.

DNA UVB dosimeters, consisting of minidots of dried bacteriophage DNA placed on a UV-transparent polymer film, were analyzed by polymerase chain reactions (PCR). Ultraviolet-B dosimetry obtained with amplification of phage lambda DNA of segments of 1.08 kilobase pairs (kbp) and 2.24 kbp was compared with that obtained with amplification of a 0.5 kbp segment (H. Yoshida and J. D. Regan, 66, 82-88, Photochem. Photobiol. 1997). The number of lesions in each segment induced by UV radiation is proportional to the size of the amplified segments; thus, the average lesion frequency per unit dose was greatest in the 2.24 kbp and least in the 0.5 kbp segment. The average lesion frequency per unit dose was approximately 3.5 x 10(-2) and approximately 11.9 x 10(-2) m2 kJ-1 for 1.08 kbp and 2.24 kbp, respectively, compared to that for 0.5 kbp of approximately 1.7 x 10(-2) m2 kJ-1 at 50 ng DNA. Dependability of DNA dosimeters, containing 50 ng and 100 ng, was tested by placing the DNA dosimeters for a time period of either 1 or 2 days outdoors on 8-12 January at Melbourne, FL. The daily dose was obtained directly with amplification of the 2.24 kbp segment and the 2 day continuous dose was obtained with amplification of the 1.08 kbp segment. Although the average lesion frequencies were different, both 50 ng and 100 ng DNA dosimeters provided about the same UVB dose, equivalent to the dose applied with a solar UVB simulator. The total UVB dose for 4 days obtained by amplification of the 1.08 and 2.24 kbp segments was 19.4-20.8 kJ m-2, which is within experimental error with the 4 day continuous dose obtained with 0.5 kbp segments. The average daily dose obtained by 0.5 kbp and 1.08 kbp agreed with the average daily dose directly obtained with 2.24 kbp.

Bacteriophage lambda↗
PubMed2002

Ultrafast flow quantification with segmented k-space magnetic resonance phase velocity mapping.

Magnetic resonance (MR) phase-velocity mapping (PVM) is routinely being used clinically to measure blood flow velocity. Conventional nonsegmented PVM is accurate but relatively slow (3-5 min per measurement). Ultrafast k-space segmented PVM offers much shorter acquisitions (on the order of seconds instead of minutes). The aim of this study was to evaluate the accuracy of segmented PVM in quantifying flow from through-plane velocity measurements. Experiments were performed using four straight tubes (inner diameter of 5.6-26.2 mm), under a variety of steady (1.7-200 ml/s) and pulsatile (6-90 ml/cycle) flow conditions. Two different segmented PVM schemes were tested, one with five k-space lines per segment and one with nine lines per segment. Results showed that both segmented sequences provided very accurate flow quantification (errors<5%) under both steady and pulsatile flow conditions, even under turbulent flow conditions. This agreement was confirmed via regression analysis. Further statistical analysis comparing the flow data from the segmented PVM techniques with (i) the data from the nonsegmented technique and (ii) the true flow values showed no significant difference (all p values>>0.05). Preliminary flow measurements in the ascending aorta of two human subjects using the nonsegmented sequence and the segmented sequence with nine lines per segment showed very close agreement. The results of this study suggest that ultrafast PVM has great potential to measure blood velocity and quantify blood flow clinically.

Aged↗
PubMed2002

A quality and efficiency analysis of the IMFAST segmentation algorithm in head and neck "step & shoot" IMRT treatments.

The performance of segmentation algorithms used in IMFAST for "step & shoot" IMRT treatment delivery is evaluated for three head and neck clinical treatments of different optimization objectives. The segmentation uses the intensity maps generated by the in-house TPS PLANUNC using the index-dose minimization algorithm. The dose optimization objectives include PTV dose uniformity and dose volume histogram-specified critical structure sparing. The optimized continuous intensity maps were truncated into five and ten intensity levels and exported to IMFAST for MLC segments optimization. The MLC segments were imported back to PLUNC for dose optimization quality calculation. The five basic segmentation algorithms included in IMFAST were evaluated alone and in combination with either tongue and groove/match line correction or fluence correction or both. Two criteria were used in the evaluation: treatment efficiency represented by the total number of MLC segments and optimization quality represented by a clinically relevant optimization quality factor. We found that the treatment efficiency depends first on the number of intensity levels used in the intensity map and second the segmentation technique used. The standard optimal segmentation with fluence correction is a consistent good performer for all treatment plans studied. All segmentation techniques evaluated produced treatments with similar dose optimization quality values, especially when ten-level intensity maps are used.

Algorithms↗