Backfitting and Related Procedures for Non-Parametric Smoothing Regression in Competition

In this paper we relate backfitting to the standard iterative procedures, i.e. Jacobi and Gauss-Seidel, developed for solving linear equation systems with non-singular system matrices. Aspects of improving the performance of these methods through relaxation are also considered. When fitting additive regression models non-parametrically by linear scatterplot smoothers, we are confronted with a singular system matrix of a certain block structure. Backfitting commonly applied, although not designed for this situation, is examined. A simulation experiment is carried out applying cubic smoothing splines in a simple additive model. The behaviour of the iterative procedures is studied by comparing the obtained results with those from a non-iterative Tichonow method. The Jacobi iteration turns out to be superior to the other procedures when speed and precision are considered simultaneously. Relaxation is of minor importance in Jacobi iteration. 1 Introduction The term backfitting is due to ..

Quantitative-evaluation of melanoma cell invasion in 3-dimensional confrontation cultures in vitro using automated image-analysis

Tumor invasion is a crucial feature of tumor growth in vivo. Confrontation cultures of multicellular melanoma spheroids and embryonic chick heart fragments provide a model for invasive growth in vitro. We have developed an image analysis method, which facilitates the objective measurement of tumor cell invasion in this model. Cryostat sections of confrontation cultures were immunohistochemically stained with an antiserum directed against the stromal component for automated recognition of the stroma tissue. The slides were automatically processed by a grey level based computerized image analysis system. On Spearman's rank correlation test, 25 out of 39 parameters correlated with the reference value of invasion, which was derived from the subjective evaluation of five independent observers. Two parameters combining the stroma margin and the total amount of stroma tissue completely reproduced the judgement of the morphologists in our test set. The quantitative evaluation of tumor invasion in vitro by automated image analysis may be helpful in pharmacologic and pathogenetic studies of tumor growth

Ganglionic Local Opioid Analgesia at the Superior Cervical Ganglion: MRI-Verified Solution Spread

Abstract Introduction Ganglionic local opioid analgesia (GLOA) at the superior cervical ganglion (SCG) is performed for pain control and is known to be an effective procedure. In this study, we evaluated the spread of the injectate in the area of the SCG. Our expectation was that there would be a correlation between the area and volume of the injectate spread and post-procedural outcome measures. Methods This was a retrospective blinded review of magnetic resonance imaging (MRI) scans. Assessors evaluated the anatomical area of fluid spread, the furthermost spread from midline, any hampered spread and contact of contrast fluid with other structures. The efficacy of GLOA and complications were estimated. Results The main solution spread reached from the C1 to C3 vertebrae. The furthest spread in the lateral and sagittal planes was 21.2 and 15.2 mm, respectively. The furthest craniocaudal spread was 63.5 mm. In 53.3% and 33% of interventions, the solution was found in the parapharyngeal space and in its “medial compartment,” respectively. A correlation was found between pain relief and both solution spread and volume of solution spread. No hampered spread was recorded. A negative correlation between pain reduction and number of GLOA was observed. Higher pre-procedural pain intensity was correlated with higher pain reduction. We estimated pain relief in 93% of procedures correctly. No correlation between post-procedural Numerical Rating Scale (NRS) scores and different needle approaches was found. Conclusion For the transoral blocking technique, a strict laterodorsal needle direction is recommended to prevent possible block failures. A total volume of 2 ml injected into the parapharyngeal space and its “medial compartment” is recommended. Higher volumes may lead to uncontrolled distribution patterns. Trial registration Clinicaltrials.gov identifier NCT05257655; date of registration 2022-02-25; patient enrollment date from 2023-01-09 to 2023-08-31