Contour Expansion Research Articles

Seminal vesicle interfraction displacement and margins in image guided radiotherapy for prostate cancer

BackgroundTo analyze interfraction motion of seminal vesicles (SV), and its motion relative to rectal and bladder filling.Methods and MaterialsSV and prostate were contoured on 771 daily computed tomography “on rails” scans from 24 prostate cancer patients undergoing radiotherapy. Random and systematic errors for SV centroid displacement were measured relative to the prostate centroid. Margins required for complete geometric coverage of SV were determined using isotropic expansion of reference contours. SV motion relative to rectum and bladder was determined.ResultsSystematic error for the SV was 1.9 mm left-right (LR), 2.9 mm anterior-posterior (AP) and 3.6 mm superior-inferior (SI). Random error was 1.4 mm (LR), 2.7 mm (AP) and 2.1 mm (SI). 10 mm margins covered the entire left SV and right SV on at least 90% of fractions in 50% and 33% of patients and 15 mm margins covered 88% and 79% respectively. SV AP movement correlated with movement of the most posterior point of the bladder (mean R2 = 0.46, SD = 0.24) and rectal area (mean R2 = 0.38, SD = 0.21).ConclusionsConsiderable interfraction displacement of SV was observed in this cohort of patients. Bladder and rectal parameters correlated with SV movement.

Prostate Localization on Daily Cone-Beam Computed Tomography Images: Accuracy Assessment of Similarity Metrics

To evaluate different similarity metrics (SM) using natural calcifications and observation-based measures to determine the most accurate prostate and seminal vesicle localization on daily cone-beam CT (CBCT) images. CBCT images of 29 patients were retrospectively analyzed; 14 patients with prostate calcifications (calcification data set) and 15 patients without calcifications (no-calcification data set). Three groups of test registrations were performed. Test 1: 70 CT/CBCT pairs from calcification dataset were registered using 17 SMs (6,580 registrations) and compared using the calcification mismatch error as an endpoint. Test 2: Using the four best SMs from Test 1, 75 CT/CBCT pairs in the no-calcification data set were registered (300 registrations). Accuracy of contour overlays was ranked visually. Test 3: For the best SM from Tests 1 and 2, accuracy was estimated using 356 CT/CBCT registrations. Additionally, target expansion margins were investigated for generating registration regions of interest. Test 1-Incremental sign correlation (ISC), gradient correlation (GC), gradient difference (GD), and normalized cross correlation (NCC) showed the smallest errors (mu +/- sigma: 1.6 +/- 0.9 approximately 2.9 +/- 2.1 mm). Test 2-Two of the three reviewers ranked GC higher. Test 3-Using GC, 96% of registrations showed <3-mm error when calcifications were filtered. Errors were left/right: 0.1 +/- 0.5mm, anterior/posterior: 0.8 +/- 1.0mm, and superior/inferior: 0.5 +/- 1.1 mm. The existence of calcifications increased the success rate to 97%. Expansion margins of 4-10 mm were equally successful. Gradient-based SMs were most accurate. Estimated error was found to be <3 mm (1.1 mm SD) in 96% of the registrations. Results suggest that the contour expansion margin should be no less than 4 mm.

On the Convergence of Cluster Expansions for Polymer Gases

We compare the different convergence criteria available for cluster expansions of polymer gases subjected to hard-core exclusions, with emphasis on polymers defined as finite subsets of a countable set (e.g. contour expansions and more generally high- and low-temperature expansions). In order of increasing strength, these criteria are: (i) Dobrushin criterion, obtained by a simple inductive argument; (ii) Gruber-Kunz criterion obtained through the use of Kirkwood-Salzburg equations, and (iii) a criterion obtained by two of us via a direct combinatorial handling of the terms of the expansion. We show that for subset polymers our sharper criterion can be proven both by a suitable adaptation of Dobrushin inductive argument and by an alternative—in fact, more elementary—handling of the Kirkwood-Salzburg equations. In addition we show that for general abstract polymers this alternative treatment leads to the same convergence region as the inductive Dobrushin argument and, furthermore, to a systematic way to improve bounds on correlations.

Numerical simulation of detonation initiation in a contoured tube

The effect of the wall contours in an axisymmetric tube on the transition from the shock wave to the detonation wave is studied numerically. Qualitative features and quantitative characteristics of the detonation initiation mechanism realized in a tube with a parabolic segment of the wall contour and conical expansion are found. The calculated results are presented in the form of “detonation curves” (angle of inclination of the contoured segment versus the Mach number of the initial shock wave) for various levels of tube blockage ratio.

Level set segmentation of bovine corpora lutea in ex situ ovarian ultrasound images

BackgroundThe objective of this study was to investigate the viability of level set image segmentation methods for the detection of corpora lutea (corpus luteum, CL) boundaries in ultrasonographic ovarian images. It was hypothesized that bovine CL boundaries could be located within 1–2 mm by a level set image segmentation methodology.MethodsLevel set methods embed a 2D contour in a 3D surface and evolve that surface over time according to an image-dependent speed function. A speed function suitable for segmentation of CL's in ovarian ultrasound images was developed. An initial contour was manually placed and contour evolution was allowed to proceed until the rate of change of the area was sufficiently small. The method was tested on ovarian ultrasonographic images (n = 8) obtained ex situ. A expert in ovarian ultrasound interpretation delineated CL boundaries manually to serve as a "ground truth". Accuracy of the level set segmentation algorithm was determined by comparing semi-automatically determined contours with ground truth contours using the mean absolute difference (MAD), root mean squared difference (RMSD), Hausdorff distance (HD), sensitivity, and specificity metrics.Results and discussionThe mean MAD was 0.87 mm (sigma = 0.36 mm), RMSD was 1.1 mm (sigma = 0.47 mm), and HD was 3.4 mm (sigma = 2.0 mm) indicating that, on average, boundaries were accurate within 1–2 mm, however, deviations in excess of 3 mm from the ground truth were observed indicating under- or over-expansion of the contour. Mean sensitivity and specificity were 0.814 (sigma = 0.171) and 0.990 (sigma = 0.00786), respectively, indicating that CLs were consistently undersegmented but rarely did the contour interior include pixels that were judged by the human expert not to be part of the CL. It was observed that in localities where gradient magnitudes within the CL were strong due to high contrast speckle, contour expansion stopped too early.ConclusionThe hypothesis that level set segmentation can be accurate to within 1–2 mm on average was supported, although there can be some greater deviation. The method was robust to boundary leakage as evidenced by the high specificity. It was concluded that the technique is promising and that a suitable data set of human ovarian images should be obtained to conduct further studies.

SU‐GG‐J‐140: Online Re‐Planning Using Direct Machine Parameter Optimization: A Non‐Human Primate Lung Irradiation Study

Purpose: Establish the feasibility of CBCT‐based, online re‐planning using direct machine parameter optimization (DMPO) to irradiate the total lung parenchyma in non‐human primates (NHPs). A study of acute‐radiation‐exposure‐ induced pneumonitis in NHPs involves total lung irradiation (TLI) to 12.5 Gy in a single session, where acute radiation exposure may also lead to the lethal hematopoeitic and gastrointestinal subsyndromes. The latter syndromes occur at 7–8 Gy and at 12–14 Gy, respectively, 1 and 2 weeks after irradiation. Hence, high dose conformity is essential to spare bone marrow, cord and bowel. Method and Materials: An offline DMPO plan is created on a CBCT scan of the NHP several days prior to the TLI session; using seven, 6MV photon beams. TLI targets a PTV from a 1 cm expansion of lung contours, sparing tissues outside the PTV. On the day of the irradiation a new CBCT is acquired, loaded into the planning system, and contours and DMPO dose objectives are propagated from the offline plan. DMPO is executed online using the original off‐line plan as starting points and the resultant on‐line plan is compared to the offline plan, on a Philips Pinnacle 8.1v workstation. Results: Online‐ and offline‐planned DMPO plans achieve V95 &gt; 95% coverage of the PTV, and excellent bowel sparing. However, offline‐planned DMPO delivers &gt; 7 Gy to more than 50% of the cord volume, while online‐planned DMPO delivers &lt; 6 Gy to more than 50 % of the cord. Online DMPO re‐optimization from scanning to the start of irradiation takes less than 45 minutes. Conclusion: Online DMPO‐based re‐planning of NHP total lung irradiations is established in support of a study of radiation‐induced pneumonitis in non‐human primates. Online‐planning on NHPs is valuable experience prior to clinical implementation in human patients.

FLUORESCENT-SPECTROSCOPIC RESEARCH OF IN VIVO TISSUES PATHOLOGICAL CONDITIONS

The steady-state spectra of autofluorescence and the reflection coefficient on the excitation wavelength of some stomach tissues in vivo with various pathological conditions (surface gastritis, displasia, cancer) are measured under excitation by the nitrogen laser irradiation (λ ex =337.1 nm ). The contour expansion of obtained fluorescence spectra into contributions of components is conducted by the Gaussian–Lorentzian curves method. It is shown that at least 7 groups of fluorophores forming a total luminescence spectrum can be distinguished during the development of displasia and tumor processes. The correlation of intensities of flavins and NAD(P)·H fluorescence is determined and the degree of respiratory activity of cells for the functional condition considered is estimated. The evaluations of the fluorescence quantum yield of the tissue's researched are given.

A note on the renormalization group and contour expansions

We show how to apply the usual renormalization group prescription to some statistical mechanical systems that can be described in terms of a polymer model.

General theory of lee-yang zeros in models with first-order phase transitions

We present a general, rigorous theory of Lee-Yang zeros for models with first-order phase transitions that admit convergent contour expansions. We derive formulas for the positions and the density of the zeros. In particular, we show that, for models without symmetry, the curves on which the zeros lie are generically not circles, and can have topologically nontrivial features, such as bifurcation. Our results are illustrated in three models in a complex field: the low-temperature Ising and Blume-Capel models, and the q-state Potts model for large q.

Low-temperature phase diagrams of quantum lattice systems. I. Stability for quantum perturbations of classical systems with finitely-many ground states

Starting from classical lattice systems ind≥2 dimensions with a regular zerotemperature phase diagram, involving a finite number of periodic ground states, we prove that adding a small quantum perturbation and/or increasing the temperature produce only smooth deformations of their phase diagrams. The quantum perturbations can involve bosons or fermions and can be of infinite range but decaying exponentially fast with the size of the bonds. For fermions, the interactions must be given by monomials of even degree in creation and annihilation operators. Our methods can be applied to some anyonic systems as well. Our analysis is based on an extension of Pirogov-Sinai theory to contour expansions ind+1 dimensions obtained by iteration of the Duhamel formula.

QUANTITATIVE ANALYSIS OF RAT SEMINAL VESICLE STROMAL PROLIFERATION ASSOCIATED WITH E 2-17β : EXPERIENCE USING AN IMAGE ANALYZER SP 500 SYSTEM (OLYMPUS CO., LTD.)

We performed a quantitative analysis of rat seminal vesicle stromal proliferation with a computed image analyzer SP 500 system (Olympus Co., Ltd.). E 2-17β was administered to immature castrated rats and the seminal vesicles (SV) were removed. We studied Mallory stained maximum longitudinal sections of the SV. In measuring the area of the gland (epithelium and lumen) and the stroma, it was effective to use the “trace method” of the SP 500 system. “RGB color slice treatment” was effective in quantifying smooth muscle and collagen. In this condition, tissue eosinophil infiltration was seen to accompany the proliferation of the SV stroma. The granules of the tissue eosinophils were treated by “color extracting treatment”, “two value treatment” and “contour expansion treatment”. These treatments allowed single granules to be recognized as one eosinophil.The SP 500 system can be widely applied to histological and morphological analysis and is easy to operate.

Unusual osteoblastic metastases from carcinoid tumors.

Abstract Two cases of metastatic bronchial carcinoid tumors with two distinctive patterns of osteoblastic bony metastases are presented and discussed in context with the current literature. Osteoblastic lesions are characterized by (a) unusually discrete radiating spiculation, or (b) diffuse bony sclerosis with dramatic expansion of contours which may occur with metastases from primary carcinoid tumors arising in the bronchial tree or lower gastrointestinal tract. Primary metastatic carcinoid should be included in the differential of osteoblastic bony metastases, particularly when these two patterns are encountered.