New Semi-Quantification Approach for Dopamine Transporter Scan: Quantification of Accumulation by Examining the Approximate Image

BackgroundSemi-quantitative analysis is used to evaluate the degree of tracer binding to the striatum in dopamine transporter (DaT) single-photon emission computed tomography (SPECT). In DaT SPECT, it is difficult to evaluate the accurate tracer accumulation due to the partial volume effect (PVE). In this study, we propose a novel semi-quantitative approach for measuring the amount of accumulation by examining the approximate image. Using the striatal phantom, we verified the validity of a newly proposed method that can accurately evaluate the tracer accumulations in the caudate and putamen, separately.MethodsThe left and right caudate/putamen regions, and the whole brain region as the background (BG) region were identified in computed tomography (CT) images obtained by SPECT/CT imaging, and the positional information of each region was obtained. The SPECT-like images were generated by assigning assumed accumulation amounts to the left and right caudate/putamen and BG regions based on the positional information. By changing the assumed accumulation amounts assigned to each region, the SPECT-like image, which was approximated to the image obtained by the SPECT imaging, was examined. The accumulation amounts assumed, when the generated SPECT-like image approximated the most to the image actually obtained by the SPECT imaging, were determined as the accumulation amounts in each region. We evaluated the correlation between the count density calculated by the proposed method and the actual count density of 123I solution filled into the striatal phantom, and verified the validity of the proposed method. In addition, the specific binding ratio (SBR) and caudate-putamen ratio (CPR) computed by the proposed method were compared with the theoretical SBR and CPR calculated by the count density of the 123I solution filled into the striatal phantom.ResultsThe count density calculated by the proposed method and the count density of 123I solution filled in the striatal phantom had an extremely strong positive correlation (r=0.997, p < 0.001). The SBRs computed by the proposed method were overestimated. However, the obtained CPRs were very similar to the theoretical CPRs.ConclusionsThe proposed method was able to compute the accurate accumulation amounts in the caudate and putamen, considering the PVE.

Different radial growth rate effects on outerwood properties of coastal Douglas-fir in healthy trees vs. trees impacted by Swiss Needle Cast

A common belief is that rapid growth in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) results in decreased outerwood quality. In Oregon, the opposite pattern has been reported for stands with Swiss Needle Cast, in which a native fungus causes pre-mature needle drop and an increase in latewood proportion (LW%), wood density, stiffness (MOE), and strength (MOR). Using a combination of new and existing data, we compared properties of outerwood of about 25 yrs age from 18 healthy and 14 diseased stands with direct tests (6-8 beams from 7-12 trees/stand, 2 614 beams total) and indirect SilviScanII tests (1 sample for each of the 366 trees). As seen before, diseased stands showed a decrease in wood quality with growth rate: ring count was strongly and positively correlated with density, MOE, and MOR (r2 = 0.74, 0.65, and 0.63), and LW% was positively correlated with ring count, density, MOE, and MOR (r2=0.50, 0.62, 0.30, and 0.44). In contrast, healthy stands had no significant effect of ring count on density, MOE, or MOR. LW% was weakly and significantly correlated with MOE (r2=0.25) but not with ring count, density, or MOR. Among healthy stands, growth acceleration had no adverse effects on outerwood properties.

Challenges and Opportunities in Thermal Management of Multi-Chip Packages

Multi-chip packages (MCPs) based solutions are becoming increasingly adopted as it results in higher signal count, density and enables increasing bandwidth demands and allows for heterogeneous integration [1,2]. However, manufacturing tolerances impose a variability in these stacks which results in new requirements for thermal interface materials. This paper describes the thermal, mechanical, and reliability challenges associated with MCP packages, and highlights need for novel thermal interface materials.

Ventilation/perfusion SPECT/CT in patients with pulmonary emphysema

SummaryThe purpose of this study was to evaluate the reproducibility of a new software based analysing system for ventilation/perfusion single-photon emission computed tomography/ computed tomography (V/P SPECT/CT) in patients with pulmonary emphysema and to compare it to the visual interpretation. Patients, material and methods: 19 patients (mean age: 68.1 years) with pulmonary emphysema who underwent V/P SPECT/CT were included. Data were analysed by two independent observers in visual interpretation (VI) and by software based analysis system (SBAS). SBAS PMOD version 3.4 (Technologies Ltd, Zurich, Switzerland) was used to assess counts and volume per lung lobe/per lung and to calculate the count density per lung, lobe ratio of counts and ratio of count density. VI was performed using a visual scale to assess the mean counts per lung lobe. Interobserver variability and association for SBAS and VI were analysed using Spearman's rho correlation coefficient. Results: Interobserver agreement correlated highly in perfusion (rho: 0.982, 0.957, 0.90, 0.979) and ventilation (rho: 0.972, 0.924, 0.941, 0.936) for count/count density per lobe and ratio of counts/count density in SBAS. Interobserver agreement correlated clearly for perfusion (rho: 0.655) and weakly for ventilation (rho: 0.458) in VI. Conclusions: SBAS provides more reproducible measures than VI for the relative tracer uptake in V/P SPECT/CTs in patients with pulmonary emphysema. However, SBAS has to be improved for routine clinical use.

Robust fixed-count density estimation with virtual plots

Fixed-count sampling (plotless) remains attractive for forest inventories in difficult terrains and for their control of the number (k) of trees to measure. Although recent fixed-count estimators of density (PDE) are less biased than older ones, the risk of a nontrivial bias remains a deterrent. A recently published PDE based on a generic algorithm for predicting distances to the k + m nearest tree (m = 1, 2, ...) has attractive properties in terms of average bias and average root mean squared errors across a wide spectrum of spatial point patterns. However, the risk of a sizeable bias remains an issue. Sensitivity to spatial patterns is seen as its main weakness. It is hypothesized that a new PDE with robust properties will mitigate the bias issue and encourage wider use. To this end, a new PDE estimator is proposed. It builds on a mixture of observed and predicted distances to a set of k + m nearest trees to generate counts of actual and virtual trees inside a circle with a data-driven fixed radius. The proposed new robust fixed-count density estimator achieved an average absolute bias of 1.2% when tested across a wide range of point patterns (54 actual and four simulated). The maximum absolute bias was 4.4%, a significant reduction when compared with otherwise attractive alternative PDEs. Root mean squared errors and coverage of 95% confidence intervals were also encouraging. The deterrent bias issue in PDEs has been sharply reduced with the proposed estimator.