EACH FRAME POINT RESTORATION ERROR BASED SUPER-RESOLUTION METHOD

В работе предложен метод повышения пространственного разрешения по серии кадров низкого разрешения, использующий для формирования результирующего изображения значения погрешностей восстановления в точке каждого кадра. Метод объединяет в себе результаты многолетних исследований автора в области повышения качества изображений и видеозаписей. Предложенный метод разрабатывался для решения прикладных задач криминалистической экспертизы видеозаписей и предназначен для повышения визуального качества плоского локального объекта, находящегося близко к центру кадра. Метод состоит из трех этапов. Первый этап - процедура сверхразрешающего восстановления в каждом кадре с учетом непрерывно-дискретной модели наблюдения сигнала с сохранением сведений об ошибке такого восстановления в дополнительный канал обработки изображения. Второй – геометрическое согласование восстановленных кадров с применением геометрического преобразования к дополнительному каналу обработки. Третий – взвешенное оптимальное по критерию минимизации среднеквадратической ошибки комплексирование кадров. Преимуществами предлагаемого метода являются оценка погрешности восстанавливаемого изображения в каждой точке, а также учет искажений изображений в непрерывной области. В работе проведено экспериментальное исследование ошибки восстановления предлагаемого метода, полученные результаты сравнивались со случаем, не использующим авторские находки предлагаемого метода, - усредняющим комплексированием линейно интерполированных кадров. Линейная интерполяция была взята, поскольку она также вписывается в фильтровую модель восстановления изображения на первом этапе работы метода. Полученные результаты демонстрируют превосходство предлагаемого метода. In this paper, a method for multi-frame superresolution is proposed. It exploits the values ​​of the recovery errors at the point of each frame to form the resulting high-resolution image. The method combines the results of many years of author's research in the field of image and video processing. The proposed method aims to apply to forensic tasks of video analysis. The method improves the visual quality of a flat local object located close to the center of the frame. The method consists of three stages. The first stage is the procedure of optimal super-resolution recovery of each frame with the use of the continuous-discrete observation model. During this stage, the recovery errors are stored in an additional image channel. The second stage is the frames registration. A geometric transformation is also applied to the additional channel during this stage. The final stage is the weighted optimal fusing. The advantages of the proposed method are the estimation of the error of the restored image at each point and taking into account the image degradations in the continuous domain. Experimental research of the reconstruction error of the method was carried out. The results were compared with the case that does not use the novel features of the proposed method - averaging fusing of linear interpolated frames. Linear interpolation was chosen as it also fits into the filtering model of image recovery of the method's first stage. The obtained results show that the proposed method outperforms the other one.

Animal remains from the Late Medieval kitchen of the Esztergom archdiocese, Hungary - the benefits of screening

Medieval animal remains from the Esztergom archbishopric (Hungary) were screened using 5 mm and 2 mm mesh sizes, aimed at the high-resolution study of fish and bird remains and helping to achieve better comparisons with documentary sources. This is the first medieval assemblage in Hungary recovered using screening. A total of 7,294 animal remains are studied here, representing the 14th and 15th century. The screening resulted in quantities of fish and bird bones. The large find numbers also multiplied the taxonomic diversity. In addition to the remains of new, small-bodied species, bones of young fish showed a diachronic increase in the contribution of carp and young pike to the diet. This seems consonant with the expansion of medieval fish farming. Remains of juvenile birds could also be identified. Some worked bones recovered by screening indicate the manufacturing or reparation of crossbows at the site. Thanks to these details, our material stands out among other contemporaneous animal bone assemblages from the Carpathian Basin. Comparisons between sites, however, must be done with caution, as our data are qualitatively different from others. Large bones of livestock and the near absence of those from large game may be interpreted in the light of other hand-collected samples, while fish and bird remains and even the abundance of brown hare need to be seen in part as a product of high-resolution recovery. The newly discovered spectrum of animal remains could be profitably interpreted in the light of late 15th century accounting books of the archbishop. Although these documentary sources slightly post-date our material, they shed light on the complexities of meat procurement between possibly local production and trade.

Positron emission tomography PET/CT harmonisation study of different clinical PET/CT scanners using commercially available software

Objectives: Harmonisation is the process whereby standardised uptake values from different scanners can be made comparable. This PET/CT pilot study aimed to evaluate the effectiveness of harmonisation of a modern scanner with image reconstruction incorporating resolution recovery (RR) with another vendor older scanner operated in two-dimensional (2D) mode, and for both against a European standard (EARL). The vendor-proprietary software EQ•PET was used, which achieves harmonisation with a Gaussian smoothing. A substudy investigated effect of RR on harmonisation. Methods: Phantom studies on each scanner were performed to optimise the smoothing parameters required to achieve successful harmonisation. 80 patients were retrospectively selected; half were imaged on each scanner. As proof of principle, a cohort of 10 patients was selected from the modern scanner subjects to study the effects of RR on harmonisation. Results: Before harmonisation, the modern scanner without RR adhered to EARL specification. Using the phantom data, filters were derived for optimal harmonisation between scanners and with and without RR as applicable, to the EARL standard. The 80-patient cohort did not reveal any statistically significant differences. In the 10-patient cohort SUVmax for RR > no RR irrespective of harmonisation but differences lacked statistical significance (one-way ANOVA F(3.36) = 0.37, p = 0.78). Bland-Altman analysis showed that harmonisation reduced the SUVmax ratio between RR and no RR to 1.07 (95% CI 0.96–1.18) with no outliers. Conclusions: EQ•PET successfully enabled harmonisation between modern and older scanners and against the EARL standard. Harmonisation reduces SUVmax and dependence on the use of RR in the modern scanner. Advances in knowledge: EQ•PET is feasible to harmonise different PET/CT scanners and reduces the effect of RR on SUVmax.

Evaluation of Left Ventricular Volumes and Ejection Fraction From Gated Myocardial Perfusion SPECT Processed with “Myovation Evolution”: Comparison of three Automated Software Packages Using Cardiac Magnetic Resonance as Reference

Backgound: The development of resolution recovery (RR) algorithms has made it possible to preserve good quality of cardiac images in spite of reduced number of counts during study acquisition. Objective: Our purpose was to evaluate the performance of three different software packages in the quantification of left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) from gated perfusion SPECT, applying a resolution recovery (RR) algorithm (GE Myovation Evolution), respect to cardiac MRI (cMRI) as gold standard. Methods: We retrospectively enrolled 21 patients, with suspected or known coronary heart disease. Images at rest were reconstructed by filtered back projection (FBP) and by an iterative protocol with the RR algorithm. EDV, ESV and LVEF were automatically computed employing Quantitative gated SPECT (QGS), Myometrix (MX) and Corridor 4DM (4DM). Any difference in EDV, ESV and LVEF calculation between cMRI and the three packages (with FBP and iterative reconstruction with RR) was tested using Wilcoxon or paired t-test, with assumption of normality assessed using ShapiroWilk test. Agreement between imaging reconstruction algorithms and between gated-SPECT software packages and cMRI was studied with Pearson’s (r) or Spearman’s (R) correlation coefficients and Lin’s concordance correlation coefficient (LCC). Results: Intra-software evaluation always revealed very strong correlation coefficients (R, r ≥ 0.8) and excellent LCC coefficients (LCC > 0.95), except for LCC coefficient between MX-FBP and MX-RR in EDV evaluation, nevertheless considered very good (LCC = 0.94). EDV and ESV had significantly lower value when calculated with RR algorithm respect to FBP reconstruction in QGS and MX. LVEF estimation did not show significant differences for QGSFBP, QGS-RR, MX and 4DM-RR with respect to cMRI. Results: Intra-software evaluation always revealed very strong correlation coefficients (R, r ≥ 0.8) and excellent LCC coefficients (LCC > 0.95), except for LCC coefficient between MX-FBP and MX-RR in EDV evaluation, nevertheless considered very good (LCC = 0.94). EDV and ESV had significantly lower value when calculated with RR algorithm respect to FBP reconstruction in QGS and MX. LVEF estimation did not show significant differences for QGSFBP, QGS-RR, MX and 4DM-RR with respect to cMRI. Conclusion: All reconstruction methods sistematically understimate EDV and ESV, with higher underestimation applying only the RR. No significant differences were observed between 4DM -RR and 4DM-FBP, for each parameter, when 4DM package was used.

Longitudinal mouse-PET imaging: a reliable method for estimating binding parameters without a reference region or blood sampling

Longitudinal mouse PET imaging is becoming increasingly popular due to the large number of transgenic and disease models available but faces challenges. These challenges are related to the small size of the mouse brain and the limited spatial resolution of microPET scanners, along with the small blood volume making arterial blood sampling challenging and impossible for longitudinal studies. The ability to extract an input function directly from the image would be useful for quantification in longitudinal small animal studies where there is no true reference region available such as TSPO imaging. Methods Using dynamic, whole-body 18F-DPA-714 PET scans (60 min) in a mouse model of hippocampal sclerosis, we applied a factor analysis (FA) approach to extract an image-derived input function (IDIF). This mouse-specific IDIF was then used for 4D-resolution recovery and denoising (4D-RRD) that outputs a dynamic image with better spatial resolution and noise properties, and a map of the total volume of distribution (VT) was obtained using a basis function approach in a total of 9 mice with 4 longitudinal PET scans each. We also calculated percent injected dose (%ID) with and without 4D-RRD. The VT and %ID parameters were compared to quantified ex vivo autoradiography using regional correlations of the specific binding from autoradiography against VT and %ID parameters. Results The peaks of the IDIFs were strongly correlated with the injected dose (Pearson R = 0.79). The regional correlations between the %ID estimates and autoradiography were R = 0.53 without 4D-RRD and 0.72 with 4D-RRD over all mice and scans. The regional correlations between the VT estimates and autoradiography were R = 0.66 without 4D-RRD and 0.79 with application of 4D-RRD over all mice and scans. Conclusion We present a FA approach for IDIF extraction which is robust, reproducible and can be used in quantification methods for resolution recovery, denoising and parameter estimation. We demonstrated that the proposed quantification method yields parameter estimates closer to ex vivo measurements than semi-quantitative methods such as %ID and is immune to tracer binding in tissue unlike reference tissue methods. This approach allows for accurate quantification in longitudinal PET studies in mice while avoiding repeated blood sampling.