Analytical and experimental FWHM of a gamma camera: theoretical and practical issues

It is well known that resolution on a gamma camera varies as a function of distance, scatter and the camera\u2019s characteristics (collimator type, crystal thickness, intrinsic resolution etc). Manufacturers frequently provide only a few pre-calculated resolution values (using a line source in air, 10\u201315 cm from the collimator surface and without scattering). However, these are typically not obtained in situations resembling a clinical setting. From a diagnostic point of view, it is useful to know the expected resolution of a gamma camera at a given distance from the collimator surface for a particular setting in order to decide whether it is worth scanning patients with \u201csmall lesion\u201d or not. When dealing with absolute quantification it is also mandatory to know precisely the expected resolution and its uncertainty in order to make appropriate corrections. Aim. Our aims are: to test a novel mathematical approach, the cubic spline interpolation, for the extraction of the full width at half maximum (FWHM) from the acquisition of a line source (experimental resolution) also considering measurement uncertainty; to compare it with the usually adopted methods such as the gaussian approach; to compare it with the theoretical resolution (analytical resolution) of a gamma camera at different distances; to create a web-based educational program with which to test these theories. Methods. Three mathematical methods (direct calculation, global interpolation using gaussian and local interpolation using splines) for calculatingFWHMfroma line source (planar scintigraphy) were tested and compared. A NEMA Triple Line Source Phantom was used to obtain static images both in air and with different scattering levels. An advanced, open-source software (MATLAB/Octave and PHP based) was created \u201cad hoc\u201d to obtain and compareFWHMvalues and relative uncertainty. Results and Conclusion. Local interpolation using splines proved faster and more reliable than the usually-adopted Gaussian interpolation. The proposed freely available software proved effective in assessing bothFWHMand its uncertainty

Oversampling errors in multimodal medical imaging are due to the Gibbs effect

To analyse multimodal 3-dimensional medical images, interpolation is required for resampling which - unavoidably - introduces an interpolation error. In this work we consider three segmented 3-dimensional images resampled with three different neuroimaging software tools for comparing undersampling and oversampling strategies and to identify where the oversampling error lies. The results indicate that undersampling to the lowest image size is advantageous in terms of mean value per segment errors and that the oversampling error is larger where the gradient is steeper, showing a Gibbs effect

The Role of Positron Emission Tomography in Clinical Management of Intraductal Papillary Mucinous Neoplasms of the Pancreas

Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas represent a heterogeneous group of tumors, increasingly diagnosed in clinical practice. An early differential diagnosis between malignant and benign lesions is crucial to patient management and the choice of surgery or observation. The therapeutic approach is currently based on a patient's clinical, biochemical, and morphological characteristics. The latest published International Consensus Guidelines (ICG) make no mention of the role of metabolic assessments of IPMNs. The aim of this study was to review the current literature, examining the role of 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) in IPMN management. An extensive literature review was conducted according to the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and 10 articles were analyzed in detail, focusing on the value of PET as opposed to other standard imaging criteria. Data were retrieved on 419 patients. The 18-FDG-PET proved more sensitive, specific, and accurate than the ICG criteria in detecting malignant IPMNs (reaching 80%, 95%, and 87% vs. 67%, 58%, and 63%, respectively). Metabolic assessments may be used as an additional tool for the appropriate management of patients with doubtful imaging findings

Effect of intracanal medication on the bond strength of root canal sealer to dentin

Objetivo: Este estudo teve como objetivo avaliar a influência da medicação intracanal na resistência de união de um cimento obturador endodôntico à dentina radicular. Métodos: Foram utilizadas 24 raízes bovinas unirradiculares que foram submetidas ao preparo químico-cirúrgico e divididas aleatoriamente em 4 grupos da seguinte forma: G1, (controle), sem medicação; G2, Hidróxido de Cálcio (Ca(OH)2) + Clorexidina (CHX); G3, bolinha de algodão embebida em Formocresol; e, G4, bolinha de algodão embebida em Paramonoclorofenol Canforado. As amostras ficaram armazenadas em temperatura ambiente e 100% de umidade por 1 semana. Logo após, foram obturadas com cimento endodôntico AH Plus e cones de guta-percha. Os dentes foram então fatiados transversalmente e o teste de push-out foi realizado. Os dados foram tabulados e submetidos à Análise de Variância. Resultados: As médias e seus respectivos desvios-padrão foram: G1, 2,42 (±1,45) ; G2, 1,81 (±1,04); G3, 2,21 (±1,14); e, G4, 2.63 (±1.32). Os resultados mostraram que não houve diferença estatisticamente significante entre os grupos em estudo. Conclusão: Pode-se concluir que as medicações intracanal utilizadas neste estudo não influenciaram na resistência de união do cimento obturador AH Plus à dentina radicular. Objective: The aim of this study was to investigate the influence of intracanal medication on the bond strength of root canal sealer to dentin. Methods: The root canals of 24 bovine incisor were prepared and randomly divided into 4 groups as follows: G1, (control group) no intracanal medication; G2, calcium hydroxide (Ca(OH)2) + chlorhexidine; G3, cotton with Formocresol; and, G4, cotton with camphorated paramonochlorophenol. The samples were stored at temperature of 37 degrees and 100% humidity for 1 week. After, they were sealed with AH Plus sealer and gutta-percha. All roots were sectioned transversely, and the push-out test was performed. The bond strength means were analyzed by analysis of variance. Results: The mean values for the bond strength test and standard deviations were: G1, 2.42 (±1.45); G2, 1.81 (±1.04); G3, 2.21 (±1.14); e, G4, 2.63 (±1.32). The results showed no statistically significant difference between the groups. Conclusion: It can be concluded that intracanal medications used in this study did not influence on the bond strength of AH Plus root canal sealer to dentin

Correction to: The role of molecular imaging in the frame of the revised dementia with Lewy body criteria

In the article mentioned above all authors were assigned affiliation 14, which is wrong. Affiliation 14 belongs only to author Agostino Chiaravalloti

Influence of Tempering Conditions on Shot-Peened Tool Steel Components In-Depth Residual Stress Profiles

Tool steel (X155CrVMo121KU in the following UK15) samples were analyzed to determine the in-depth residual stress profile and to study modifications in the microstructure, induced by a shot-peening treatment. The influence of different tempering temperatures was studied. Residual stress and dislocation density profiles were measured using standard laboratory X-ray diffraction (XRD) residual stress analysis with progressive chemical layer removal. Dislocation density profiles where obtained using a Whole Powder Pattern Modeling (WPPM) procedure

The evidence-based role of catecholaminergic PET tracers in Neuroblastoma. A systematic review and a head-to-head comparison with mIBG scintigraphy

Background: Molecular imaging is pivotal in staging and response assessment of children with neuroblastoma (NB). [123I]-metaiodobenzylguanidine (mIBG) is the standard imaging method; however, it is characterised by low spatial resolution, time-consuming acquisition procedures and difficult interpretation. Many PET catecholaminergic radiotracers have been proposed as a replacement for [123I]-mIBG, however they have not yet made it into clinical practice. We aimed to review the available literature comparing head-to-head [123I]-mIBG with the most common PET catecholaminergic radiopharmaceuticals. Methods: We searched the PubMed database for studies performing a head-to-head comparison between [123I]-mIBG and PET radiopharmaceuticals including meta-hydroxyephedrine ([11C]C-HED), 18F-18F-3,4-dihydroxyphenylalanine ([18F]DOPA) [124I]mIBG and Meta-[18F]fluorobenzylguanidine ([18F]mFBG). Review articles, preclinical studies, small case series (< 5 subjects), case reports, and articles not in English were excluded. From each study, the following characteristics were extracted: bibliographic information, technical parameters, and the sensitivity of the procedure according to a patient-based analysis (PBA) and a lesion-based analysis (LBA). Results: Ten studies were selected: two regarding [11C]C-HED, four [18F]DOPA, one [124I]mIBG, and three [18F]mFBG. These studies included 181 patients (range 5-46). For the PBA, the superiority of the PET method was reported in two out of ten studies (both using [18F]DOPA). For LBA, PET detected significantly more lesions than scintigraphy in seven out of ten studies. Conclusions: PET/CT using catecholaminergic tracers shows superior diagnostic performance than mIBG scintigraphy. However, it is still unknown if such superiority can influence clinical decision-making. Nonetheless, the PET examination appears promising for clinical practice as it offers faster image acquisition, less need for sedation, and a single-day examination

Theranostics in Neurooncology: Heading Toward New Horizons

Therapeutic approaches to brain tumors remain a challenge, with considerable limitations regarding delivery of drugs. There has been renewed and increasing interest in translating the popular theranostic approach well known from prostate and neuroendocrine cancer to neurooncology. Although far from perfect, some of these approaches show encouraging preliminary results, such as for meningioma and leptomeningeal spread of certain pediatric brain tumors. In brain metastases and gliomas, clinical results have failed to impress. Perspectives on these theranostic approaches regarding meningiomas, brain metastases, gliomas, and common pediatric brain tumors will be discussed. For each tumor entity, the general context, an overview of the literature, and future perspectives will be provided. Ongoing studies will be discussed in the supplemental materials. As most theranostic agents are unlikely to cross the blood-brain barrier, the delivery of these agents will be dependent on the successful development and clinical implementation of techniques enhancing permeability and retention. Moreover, the international community should strive toward sufficiently large and randomized studies to generate high-level evidence on theranostic approaches with radioligand therapies for central nervous system tumors