Static Segmentations in Dynamic PET Images: The need for a new method

The Task Group 211 report of the American Association of Physicists in Medicine (AAPM) reviewed static segmentation techniques in nuclear positronemission tomography (PET) imaging used in nuclear medicine. These methods, when applied to a dynamic image, such as the ones obtained in pharmacokinetic analyses, fail to take into account the dynamic nature of the acquisitions. In this article, the leading hypothesis was that a static segmentation was not adequate in even the simplest dynamic PET images. To put this idea forward, a simple dynamic PET phantom was devised. Many dynamic acquisitions were obtained using FDG. To analyze them, different static segmentations were performed on each timeframe. These were followed by quantitative analyses to determine whether the segmentations were consistant between various timeframes of reference. The quantitative analytical tools used were the S{\o}rensen-Dice coefficients, the overlapping of the time-activity curves (TACs), and the pharmacokinetic parameters extracted from the images using the Dynesty Python package. In order to perform some of the analyses, an uncertainty had to be added to the TACs themselves: to do so, the individual segmentations were spatially displaced to estimate the sensibility of the TAC to the underlying segmentation. Using these analytical tools, we propose that static segmentations are not sufficient tools for segmenting dynamic images in a nuclear medicine context. The specific case of pharmacokinetic modelling is used to exemplify this idea. Further work could include a method of estimating uncertainties on segmentations or a novel method for dynamic segmentations in dynamic PET images.Comment: 15 pages, 5 figure

Investigation of the neurovascular coupling in positive and negative BOLD responses in human brain at 7T

Decreases in stimulus-dependent blood oxygenation level dependent (BOLD) signal and their underlying neurovascular origins have recently gained considerable interest. In this study a multi-echo, BOLD-corrected vascular space occupancy (VASO) functional magnetic resonance imaging (fMRI) technique was used to investigate neurovascular responses during stimuli that elicit positive and negative BOLD responses in human brain at 7 T. Stimulus-induced BOLD, cerebral blood volume (CBV), and cerebral blood flow (CBF) changes were measured and analyzed in ‘arterial’ and ‘venous’ blood compartments in macro- and microvasculature. We found that the overall interplay of mean CBV, CBF and BOLD responses is similar for tasks inducing positive and negative BOLD responses. Some aspects of the neurovascular coupling however, such as the temporal response, cortical depth dependence, and the weighting between ‘arterial’ and ‘venous’ contributions, are significantly different for the different task conditions. Namely, while for excitatory tasks the BOLD response peaks at the cortical surface, and the CBV change is similar in cortex and pial vasculature, inhibitory tasks are associated with a maximum negative BOLD response in deeper layers, with CBV showing strong constriction of surface arteries and a faster return to baseline. The different interplays of CBV, CBF and BOLD during excitatory and inhibitory responses suggests different underlying hemodynamic mechanisms

Telegram to Joseph T. Lawless from Daniel F. Cohalan, Aug 23, 1919

Hon Joseph T. Lawless Norfolk VA Would urge you go tot Richmond tomorrow to perfect arrangments regarding legislature and all other matter. Please phone Lynch tomorrow Fordham five eight eight extension nineteen eleven o clock or three Daniel F. Cohalanhttps://digitalcommons.georgiasouthern.edu/lawless/1043/thumbnail.jp

The stratigraphy and deformation history of the Daisy Milano gold deposit, Mt Monger, Western Australia

This thesis aims to understand the stratigraphy and deformation history of the Mt Monger Goldfield as well as the timing of its high-grade gold deposits. Whole rock geochemical analyses were carried out to precisely differentiate between the mafic and ultramafic units using REE spidergrams and La and Th v TiO2 ratios in particular. These ratios are compared to values established in the literature for regional stratigraphic units. It was found that each of the three mafic units near Daisy Milano have compositional equivalents in the Kambalda Sequence of the Kalgoorlie Terrane, which hosts many major gold deposits. The Lower Basalt, Wombola Dolerite and Mt Monger Sills near Daisy Milano are compositionally very similar to the Lunnon Basalt, Devon Consols Basalt and Paringa Basalt of the Kambalda Sequence, respectively, and correlate to Eastern Goldfields-wide basaltic groups. In contrast, the Daisy Milano Komatiite is compositionally distinct from the Kambalda Komatiite. Furthermore, the felsic to intermediate stratified clastic unit at Daisy Milano, below and intercalated with the komatiite unit, is stratigraphically lower than are stratified clastic units in the Kambalda Sequence. Structural analysis from surface exposures and oriented drillcore reveal evidence for an early N-S shortening event (D1) giving rise to low-angle thrust planes verging north preceding the Eastern Goldfields-wide ENE-WSW shortening event (D2) which produced the dominant NNW-trending steeply-dipping foliation at Daisy Milano. This was followed by a later dextral strike-slip deformation event along N-S oriented structures (D3). In the Wombola structural domain (west part of the Daisy Milano area), gold occurs in NE- to ENE-trending vertical quartz veins cross-cutting dolerite. These veins and the gold mineralisation are interpreted to be associated to the main ENE-WSW shortening event (D2). In the Daisy Milano structural domain (east part of the Daisy Milano area), gold occurs in N-S to NNW-SSE structures, usually along the contacts of felsic porphyritic dykes intruding these structures, and especially just below the stratigraphic level of the komatiite units. These mineralised structures are interpreted to have developed parallel to the axial planes of D2 folds resulting from ENE-WSW shortening and to have been reactivated during the later dextral strike-slip event (D3). Gold mineralisation in these structures is interpreted to be contemporaneous to, and controlled by, the later strike-slip event (D3) and possibly also by D2. The felsic porphyritic dykes were dated ~2676 and ~2687 Ma using zircon U-Pb geochronology by LA-ICP-MS. The orientation and structures of these dykes suggest that their emplacement was pre- and syn-D2. The combination of stratigraphic, geochronological and structural investigation has shed new light on the geologic controls of the deposits. It places them in a regional context allowing for easier comparison to other known deposits in the Eastern Goldfields which can lead to new exploration strategies

Letter to Joseph T. Lawless from Daniel F. Cohalan, Oct 6, 1921

This letter from Daniel F. Cohalan refers to a previous letter written to him by Lawless. Cohalan recognizes the events in the South and the significance of it. He requests Lawless to speak at the next meeting regarding Irishmen in the South. Cohalan also refers to an address given that discusses the similarities between the Irish and American revolutions.https://digitalcommons.georgiasouthern.edu/lawless/1139/thumbnail.jp

Telegram to Joseph T. Lawless from Daniel F. Cohalan, Aug 20,1919

Hon Joseph T. Lawless Wired Cochrane yesterday Bar Harbor Maine requesting him wire decision to yourself and O\u27Flaherty Daniel F. Cohalanhttps://digitalcommons.georgiasouthern.edu/lawless/1040/thumbnail.jp

Cerebral blood volume changes during human neuronal activation: a comparative study of VASO and VERVE

In this research, two techniques which measure hemodynamic changes during neuronal activation in humans were studied. The Vascular Space Occupancy (VASO) technique indirectly measures changes in total cerebral blood volume (CBV) by measuring the decrease in grey matter signal during activation, in images in which the blood signal is nulled. The Venous Refocusing for Volume Estimation (VERVE) technique measures changes in venous blood volume by exploiting the dependence of partially-deoxygenated blood's T2¬ on the refocusing interval τ180. Using a simultaneous visual and motor task, a (ΔCBV/CBVrest)total of 25.0 ± 13.9 % and a (ΔCBV/CBVrest)¬venous of 3.9 ± 1.6 % were measured using VASO and VERVE, respectively. Though the VASO technique has a high CNR and is simple to implement, its signal has contributions from many compartments other than grey matter. VERVE has fewer deleterious effects, but suffers from a higher power deposition. The activated regions in VERVE overlap better with BOLD activation than the VASO regions do, which, combined with VERVE's specificity to venous CBV changes, make it more appropriate in an investigation of the blood volume contribution to the BOLD signal.Deux techniques visant à mesurer les changements de volume sanguin cérébral durant l'activité neuronale sont étudiées. La première, Vascular Space Occupancy (VASO), mesure l'augmentation de l'ensemble du sang en mesurant la baisse du signal provenant de la matière grise, dans une image où la magnétisation du sang est nulle. La deuxième, Venous Refocusing for Volume Estimation (VERVE), mesure en particulier l'augmentation du volume sanguin veineux en exploitant la dépendance du T2 du sang partiellement deoxygéné sur l'intervalle de refocalisation τ180. Avec une tâche à la fois motrice et visuelle, un (ΔCBV/CBVrepos)totale de 25,0 ± 13,9 % et un (ΔCBV/CBVrepos)¬veineux de 3,9 ± 1,6 % ont été mesurés par VASO et VERVE, respectivement. La méthode VASO est facile à instrumenter, et jouit d'un ratio contraste-bruit plus élevé que VERVE, mais plusieurs compartiments autres que la matière grise contribuent à son signal. Moins d'effets gênants contribuent au signal de VERVE, mais celui-ci souffre d'un taux de puissance déposé élevé, parfois atteignant les limites imposées par la Commission Fédérale des Communications. Le volume activé de VERVE correspond mieux que le volume activé de VASO au volume activé de BOLD. Ce fait, et celui que VERVE mesure spécifiquement le volume veineux, prônent l'utilisation de cette technique dans une analyse de la contribution du volume sanguin au signal BOLD

Letter to Joseph T. Lawless from Daniel F. Cohalan, Oct 11, 1921

This letter confirms Lawless to speak at the quarterly meeting. Cohalan also briefly mentions the Panama Canal Tolls bill.https://digitalcommons.georgiasouthern.edu/lawless/1141/thumbnail.jp