Mean Percentage Difference Research Articles

Management strategies differentially affect root functional trait expression in cocoa agroforestry systems

In tree-based agroecosystems, environmental heterogeneity can be high and resource acquisition strategies among individual plants can be expected to vary. This poses a challenge for appropriate nutrient prescriptions. We used a novel trait-based approach to measure in situ fine root phenotypic response of cocoa (Theobroma cacao) to fertilization. Two levels of NPK fertilizer were applied to cocoa in agroforestry, with shade trees Entandrophragma angolense or Terminalia ivorensis, or in monoculture. Four months following fertilization, cocoa fine roots were extracted from ingrowth cores and analyzed for a suite of traits positively associated with resource acquisition: fine root production, ratio of absorptive to transport roots, specific root length, specific root area, specific root tip abundance, and root nitrogen content, as well as traits positively associated with longer-lived root organs (resource conservative): root tissue density, average root diameter, and root carbon to nitrogen ratio. In surface soils (0 to 10 cm), fertilization largely stimulated roots to express resource conservative strategies compared to unfertilized cocoa roots (up to 70% mean percent difference among all root traits) but with limited measurable differences in root trait response between the two fertilization levels. In subsurface soils (10 to 20 cm), however, inconsistent cocoa root responses to fertilization and shade trees suggested increasing complexity in nutrient acquisition strategies with soil depth. At both depths, we detected coordination among cocoa root trait variation including a resource acquisition to conservation axis explaining ~ 45% of total trait variation, yet an individual cocoa plant’s position on these coordinated trait axes was predominately affected by the shade tree rather than fertilization level. This study provides some of the first insights into intraspecific root functional trait expression to fertilization in multispecies agriculture. We show that a trait-based approach can be used to improve diagnostics and prescriptions of nutrient amendments in agroforestry systems.

Ingesting a 12% Carbohydrate-Electrolyte Beverage Before Each Half of a Soccer Match Simulation Facilitates Retention of Passing Performance and Improves High-Intensity Running Capacity in Academy Players.

This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed, and high-intensity running capacity. Eighteen elite academy (age: 18 ± 2 years) soccer players ingested two 250-ml doses (pre-exercise and at halftime) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomized cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing, and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean percentage difference [95% confidence interval, CI]: 9 [3, 15]) and nondominant (mean percentage difference [95% CI]: 13 [6, 20]) feet was better maintained during the SMS on CHO-E (p < .05), with passing speed better maintained in the nondominant foot (mean percentage difference [95% CI]: 5.3 [0.7, 9.9], p = .032). High-intensity running capacity was greater in CHO-E versus placebo (mean percentage difference [95% CI]: 13 [6, 20], p = .010). Capillary blood glucose concentration was higher in CHO-E than placebo at halftime (CHO-E: 5.8 ± 0.5mM vs. placebo: 4.1 ± 0.4mM, p = .001) and following the high-intensity running capacity test (CHO-E: 4.9 ± 0.4mM vs. placebo: 4.3 ± 0.4mM, p = .001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the nondominant foot, and improves subsequent high-intensity running capacity.

The Relative Contribution of Food Groups to Macronutrient Intake in Children with Cystic Fibrosis: A European Multicenter Assessment

BackgroundOptimal nutrition for children with cystic fibrosis (CF) improves prognosis and survival, but an increased caloric intake recommendation for this population raises concerns about the nutrient profile of their diets. ObjectiveOur aim was to assess the relative contribution of food groups to the total macronutrient intake of European pediatric patients with CF. DesignWe conducted a cross-sectional study in which the participants recorded dietary intake from 2016 to 2017. Specifically developed nutritional composition databases were used to obtain nutritional data, including macronutrients and food groups, according to previously standardized criteria. Participants/settingTwo hundred and seven pediatric patients with CF from six European centers were involved in the My App for Cystic Fibrosis self-management project. Main outcome measuresParticipants reported dietary intake with a detailed 4-day food record. Statistical analysis performedDescriptive analyses of nutrient intake, food group consumption, and dietary origin of macronutrients were conducted with R software. ResultsSimilar patterns were found in nutrient and food group intake; both sugar and saturated fatty acids contributed >10% each to the total daily energy intake in all the centers. Large mean and median percent differences were observed in the intake of other nutrient and food groups, because sweets and snacks were consumed once or twice a day, and fruit and vegetables were consumed two or three times a day. Milk, meat, sweets and snacks, and oils were the main sources of fat in all centers. ConclusionsStudy findings indicated less than optimal nutrient profiles, especially for sugars and saturated fatty acids, resulting from the high consumption of meat, dairy, and processed products and low consumption of fish, nuts, and legumes. These results can serve as a basis for future tailored interventions that target improved adherence to nutritional recommendations for patients with CF.

Audiology Telemedicine Evaluations: Potential Expanded Applications.

There is underutilization of cochlear implants with delays in implantation linked to distance from implant centers. Telemedicine could connect cochlear implant specialists with patients in rural locations. We piloted telemedicine cochlear implant testing in a small study, largely composed of normal-hearing volunteers to trial this new application of teleaudiology technology. Thirteen subjects (8 with normal hearing and 5 with hearing loss ranging from mild to profound) underwent a traditional cochlear implant evaluation in person and then via telemedicine technology. Routine audiometry, word recognition testing, and Arizona Biological Test (AzBio) and consonant-nucleus-consonant (CNC) testing were performed. Mean (SD) percent difference in AzBio between in-person and remote testing was 1.7% (2.06%). Pure tone average (PTA), speech reception threshold (SRT), and word recognition were similar between methods. CNC testing showed a mean (SD) difference of 6.8% (10.2%) between methods. Testing conditions were acceptable to audiologists and subjects. Further study to validate this method in cochlear implant candidates and a larger population is warranted.

3D Tibia Reconstruction Using 2D Computed Tomography Images.

Skeletal stress fracture of the lower limbs remains a significant problem for the military. The objective of this study was to develop a subject-specific 3D reconstruction of the tibia using only a few CT images for the prediction of peak stresses and locations. Full bilateral tibial CT scans were recorded for 63 healthy college male participants. A 3D finite element (FE) model of the tibia for each subject was generated from standard CT cross-section data (i.e., 4%, 14%, 38%, and 66% of the tibial length) via a transformation matrix. The final reconstructed FE models were used to calculate peak stress and location on the tibia due to a simulated walking load (3,700 N), and compared to the raw models. The density-weighted, spatially-normalized errors between the raw and reconstructed CT models were small. The mean percent difference between the raw and reconstructed models for peak stress (0.62%) and location (-0.88%) was negligible. Subject-specific tibia models can provide even great insights into the mechanisms of stress fracture injury, which are common in military and athletic settings. Rapid development of 3D tibia models allows for the future work of determining peak stress-related injury correlates to stress fracture outcomes.

The impact of intra-fractional bladder filling on "Plan of the day" adaptive bladder radiotherapy.

A retrospective audit on the "Plan of the day" (POD) selection and intra-fractional bladder fillings were carried out on twenty adaptive bladder radiotherapy patients at a single institution. Treatment time, differences in bladder volume and displacement of outer bladder wall expansion over the treatment fraction were analysed. Average treatment time was 8.9 min. The mean percentage difference in bladder volume pre and post treatment was 13.7%, resulting in expansion of the bladder predominately in the superior and anterior directions. This audit confirmed that the institution's POD process sufficed without being significantly affected by the intra-fractional bladder filings.

Using shallow groundwater modeling to frame the restoration of a wet prairie in the Oak Openings Region, Ohio, USA: GSSHA model implementation

The hydrologic characteristics of the Oak Openings Region in northwest Ohio, USA, a globally rare ecosystem are not well understood. Currently, the Oak Openings supports globally rare oak savanna and wet prairie habitats. The wet prairies in the region have been drained by ditches and encroached by invasive plants, which have altered the natural flow making it an unusually variable and artificial system. A shallow groundwater model was implemented using the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) software to simulate continuous, long-term groundwater and surface water interaction in a small subwatershed in the Oak Openings Region. The implemented GSSHA model simulates physical processes such as infiltration, evapotranspiration, snowmelt, overland flow, and interaction of groundwater with ditches. The model was calibrated using a time series of water table elevations collected in the field. Although the model tends to slightly underestimate water table elevations (mean and standard deviation percent differences of less than 1%), statistical analysis indicate a good fit between observed and simulated water table elevations (Nash Sutcliffe Efficiency Index of 0.78). The model would be a useful tool for the preservation of natural areas such as wet prairies.

Development of a core collection in Iranian walnut (Juglans regia L.) germplasm using the phenotypic diversity

Persian walnut (Juglans regia L.) is a very important nut crop with increasingly attention in the world. It was among the fruit tree species that has been propagated sexually, up to some decades ago. So, there were no or limited cultivars and the breeding works are usually new. In order to release new cultivars, a walnut improvement program started in Iran in 1980s. There was established a walnut collection, with selection of some superior genotypes from the orchards together with some introductions. As, the comprehensive characterization of germplasm is necessary in the breeding programs, in this study a collection of 104 Persian walnut accessions has been evaluated especially in order to create a core or breeding collection with reduced number of accessions and keeping maximum variability. To carry out this work, 18 walnut important traits were evaluated during 2014 and 2015 in the walnut collection of Horticultural Science Research Institute, Karaj, Iran. A wide variation was observed for several important characteristics such as leafing date (from March, 5 to April, 27), nut weight (6.60–15.33 g), kernel weight (2.67–8.21 g), and kernel percentage (35.39–71.09%). Significant correlations were observed between traits. Factor analysis showed that the six major factors affecting traits were explaining 79.9% of the total variance. The analysis, using maximization strategy through a heuristic algorithm, determined a core collection consisted of 27 accessions with similar variability respect to primary collection (mean difference percentage = 9.88% and coincidence rate of range = 95.05%). The parameters showed that this core includes 100% coverage of the primary diversity. According to result the F-test revealed no-significant differences for all traits. In this paper, for the first time, a walnut core collection was established from a primary collection. Conservation of this core collection could be more economic and better manageable for breeding purposes.

Free-Living Comparison of Physical Activity and Sleep Data from Fitbit Activity Trackers Worn on the Dominant and Nondominant Wrists

ABSTRACTDespite proprietary algorithms to account for differences, output from activity trackers worn on different wrists may not be comparable because individuals vary in their reliance on each hand during free-living activities.Participants (n = 48) wore Fitbit Flex or Flex2 monitors on each wrist for three days. T tests, equivalence tests, and correlations were used to compare steps, Calories, distance, active minutes, and sleep duration recorded by dominant and nondominant wrist-worn monitors and effect sizes and mean absolute and percent difference were calculated.The nondominant Flex2 monitor was not equivalent to the dominant wrist-worn monitor and recorded significantly more steps/day (absolute difference = 708), miles/day (0.3), and active minutes/day (7.9) than the dominant Flex2 monitor. For all variables, nondominant and dominant output was correlated (r>0.75).Nondominant and dominant Flex2 monitors are significantly different, but there were small differences for Flex monitors. Research should investigate effects on behavior and replicate findings using other monitors.

Sensitivity of optimized transient storage model parameters to spatial and temporal resolution

The transient storage model is a popular tool for modelling solute transport along rivers. Its use requires values for the velocity and shear flow dispersion coefficient in the main channel of the river together with two exchange rates between the main channel and transient storage zones, which surround the main channel. Currently, there is insufficient knowledge to enable these parameters to be predicted from the type of hydraulic variables that may typically be available. Hence, recourse is made to tracer experiments, which provide temporal solute concentration profiles that can be used to estimate the parameters by optimizing model output to observations. The paper explores the sensitivity of such parameters to the spatial and temporal resolutions used in the optimization of the model. Data from 25 tracer experiments covering a river flow rate range of 300–2250 L/s in a single reach of the river Brock in north-west England were used. The shear flow dispersion coefficient was found to be the most sensitive parameter; the velocity was found to be the least sensitive parameter. When averaged over all the experiments, mean percentage differences in parameter values between a coarse resolution case and a fine resolution case were of the order of 2% for the velocity, 70% for the shear flow dispersion coefficient and 30% and 20% for the two exchange rates. Since the shear flow dispersion coefficient was found to be small, both in numerical terms and in comparison with an estimate of the total dispersion in the reach, it is suggested that it may be viable to omit the shear flow dispersion term from the model.

Change in Bone Density and Reduction in Fracture Risk: A Meta-Regression of Published Trials

Meta-analyses conducted >15 years ago reported that improvements in bone mineral density (BMD) were associated with reduction in vertebral and nonvertebral fractures in osteoporosis trials. Numerous studies have been conducted since then, incorporating new therapies with different mechanisms of action and enrolling many more subjects. To extend these prior analyses, we conducted a meta-regression of 38 placebo-controlled trials of 19 therapeutic agents to determine the association between improvements in BMD and reductions in fracture risk. We used a linear model to examine the relationship between mean percent difference in BMD change between treatment and placebo groups and the logarithm of the relative risk. We found that greater improvements in BMD were strongly associated with greater reductions in vertebral and hip fractures but not nonvertebral fractures. For vertebral fracture, the r2 values for total hip, femoral neck, and lumbar spine BMD change were 0.56, 0.54, and 0.63, respectively (p ≤ 0.0002). For a 2% or 6% improvement in total hip BMD, we might expect a 28% or 66% reduction, respectively, in vertebral fracture risk. For hip fracture, the r2 values for total hip, femoral neck, and lumbar spine BMD change were 0.48 (p = 0.01), 0.42 (p = 0.02), and 0.22 (ns), respectively. For a 2% or 6% improvement in total hip BMD, we might expect a 16% or 40% reduction in hip fracture risk. In conclusion, our results extend prior observations that larger improvements in dual-energy X-ray absorptiometry (DXA)-based BMD are associated with greater reductions in fracture risk, particularly for vertebral and hip fractures. Although these results cannot be directly applied to predict the treatment benefit in an individual patient, they provide compelling evidence that improvements in BMD with osteoporosis therapies may be useful surrogate endpoints for fracture in trials of new therapeutic agents. © 2019 American Society for Bone and Mineral Research.

Impact of segmentation density on spectral domain optical coherence tomography assessment in Stargardt disease.

Automated spectral domain optical coherence tomography (SD-OCT) segmentation algorithms currently do not perform well in segmenting individual intraretinal layers in eyes with Stargardt disease (STGD). We compared selective B-scan segmentation strategies for generating mean retinal layer thickness and preserved area data from SD-OCT scans in patients with STGD1. Forty-five eyes from 40 Stargardt patients were randomly selected from the ongoing Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study. All eyes underwent SD-OCT using a standard macular volume consisting of 1024 × 49 equally spaced B-scans within a 20 × 20 degree field centered on the fovea. All 49 B-scans were segmented manually to quantify total retina, outer nuclear layer (ONL), photoreceptor inner segments, photoreceptor outer segments (OS), and retinal pigment epithelial layer (RPE). Mean thickness and total area were generated using all 49 B-scans (spaced 122μm apart), 25 B-scans (every other B-scan, spaced 240μm apart), 17 B-scans (every third scan, 353μm apart), and 13 B-scans (every fourth scan, 462μm apart), as well as by using an "adaptive" method where a subset (minimum 25 B-scans) of B-scans that the grader deemed as significantly different from adjacent B-scans were utilized. Mean absolute and percentage errors were calculated for macular thickness and area of different retinal layers for the different B-scan subset selection strategies relative to using all 49 B-scans, which was considered the reference or ground truth. Mean thickness and area measurements were significantly different for any regularly spaced reduction in B-scan density relative to the ground truth. When an adaptive approach was applied using a minimum of half the scans, the differences relative to ground truth were no longer significantly different. The mean percent differences for the area and thicknesses of the various layers ranged from 0.02 to 33.66 (p < 0.05 for all comparisons) and 0.44 to 7.24 (p > 0.05) respectively. Manual segmentation of a subset of B-scans using an adaptive strategy can yield thickness and area measurements of retinal sublayers comparable to the reference ground truth derived from using all B-scans in the volume. These results may have implications for increasing the efficiency of SD-OCT grading strategies in clinical trials for STGD and other related macular degenerative disorders.

Addition of magnetic resonance imaging to real time trans-rectal ultrasound-based treatment planning for prostate implants.

PurposeThe greater soft tissue contrast of magnetic resonance imaging (MRI) allows improved accuracy in prostate contouring compared to transrectal ultrasound (TRUS) and helps in identifying specific regions within the prostate. This study attempts to evaluate the potential benefit of MRI-TRUS fusion in treatment planning for more accurate prostate contouring and tumor dose escalation.Material and methods14 patients with previous MRI-guided prostate biopsy and an low-dose-rate (LDR) permanent prostate seed implant have been selected. The prostate and tumor (5 patients) were contoured on the MRI images by a radiologist. The prostate was also contoured on TRUS images during LDR procedure together by a urologist and radiation oncologist. MRI and TRUS images were rigidly fused to compare prostate contours in MRI and TRUS. Prostate was then re-contoured by the radiation oncologist using this fusion. Moreover, V100, V150, and D90 differences were evaluated for localized tumor compared to prostate with negative values indicating cold tumor regions. These cases were re-planned to simulate dose escalation.ResultsThe prostate volume was contoured 8 ±10% smaller in TRUS images, compared to MRI images. The mean percent difference in tumor (compared to prostate) V100 was 0.3 ±–0.4%, V150 was –0.7 ±–24.8%, and D90 was 0.2 ±–12.1%. For the posteriorly located tumors (2 cases), V100 was 0.0 ±–0.3%, D90 was 9.5 ±–3.0%, and V150 was 26.1 ±–5.4%. For anteriorly located tumors (3 cases), V100 was 0.4 ±–0.4%, D90 was –6.0 ±–11.9%, and V150 was –18.5 ±–14.4% (became 15.6 ±14.6% after re-plan).ConclusionsThe MRI-TRUS image fusion is a feasible tool for the visualization of the prostate gland, particularly at the apex and base of the gland. Tumor identification presents the potential for dose escalation using fusion, especially for anteriorly located tumors.

Effect of different definitions of prescription point “A” in high dose rate brachytherapy for cervical cancer

This study intended to compare the dosimetric parameters using different definitions of prescription point A in high dose rate (HDR) brachytherapy of cervical cancer patients. Manchester point A has been widely used for prescribing dose in brachytherapy. However, due to certain limitations of this point, a new definition of point A has been recommended by the American Brachytherapy Society (ABS). We retrospectively investigated 55 computed tomography-based plans of 20 cervical cancer patients treated with Ir-192-based intracavitary HDR brachytherapy. The dose of 7 Gy in 3 fractions each was prescribed to point A using revised Manchester definition of point A (AMAN) and ABS guideline definition (AABS). The effect of both definitions on various parameters including dose to point A and 90% of tumor volume (D90), dose received by 2cc volume of bladder, rectum and small bowel and treatment volume receiving 100% of prescription dose (V100) was analyzed. Mean percentage difference of point AMAN dose and AABS dose with respect to prescription dose was 1.25% ± 1.43% and 1.21% ± 1.01%, respectively. Mean V100 was 80.4 ± 20.45cc and 88.47 ± 16.78cc for AMAN and AABS plans, respectively, while mean percentage difference between prescribed dose and D90 was found to be -37.90% ± 25.06% and -30.47% ± 25.50% respectively for both the definitions. Doses to both Manchester point A and ABS point A may be recorded during the transition period. However, ABS point A can be preferred over the Manchester point A as it conforms better with the desired dosimetric outcome and is found to be more static.

Multicenter Survey of the Display Air Kerma and Actual Measured Values in IVR X-ray Apparatus

We conducted a multicenter study to investigate the current status of difference between the actual values at the patient entrance reference point (PERP) and display air kerma. We exposure dose and fluoroscopy dose were measured by 32 apparatuses at 32 member institutions of the Japanese Society of Circulation Imaging Technology (CITEC) under unified conditions, and the actual measured values and display air kerma were compared. We entrance doses during fluoroscopy and imaging were measured at the PERP, with focus detector distance (FDD) 110 cm, a copper plate of 3.5 mm in thickness adhered to the front face of flat panel detector (FPD) as absorber, field-of-view (FOV) 18 cm, and the frame rate of 15 f/s, excluding the bed. Display air kerma were recorded at the same time. JIS (Z 4751-2-43: 2012) specify "The reference air kerma rate and the cumulative reference air kerma shall not deviate from their respective display air kerma by more than ±35% over the range of 6 mGy/min and 100 mGy to the maximum value." The number of apparatuses display air kerma deviated from this condition and its percentage were obtained. The mean difference percentage between actual measured values and display air kerma in 32 apparatuses was approximately 15.6%, with some apparatuses showing substantially different display air kerma. In order to estimate patients' skin exposure dose from display air kerma more accurately, it is necessary to perform calibration of the apparatus by regular dose measurement or convert values.

Validity, reliability and minimum detectable change of COSMED K5 portable gas exchange system in breath-by-breath mode.

PurposeThis study aimed to examine the validity, reliability and minimum detectable change (MDC) of the Cosmed K5 in breath by breath (BxB) mode, against VacuMed metabolic simulator. Intra and inter-units reliability was also assessed.MethodsFourteen metabolic rates (from 0.9 to 4 L.min-1) were reproduced by a VacuMed system and pulmonary ventilation (VE), oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured by two different K5 units. Validity was assessed by ordinary least products (OLP) regression analysis, Bland-Altman plots, intraclass correlation coefficients (ICC), mean percentage differences, technical errors (TE) and MDC for VE, VO2, and VCO2. Intra- and inter-K5 reliability was evaluated by absolute percentage differences between measurements (MAPE), ICCs, TE, and MDC.ResultsValidity analysis from OLP regression data and Bland- Altman plots indicated high agreement between K5 and simulator. ICC values were excellent for all variables (>0.99). Mean percentage differences in VE (-0.50%, p = 0.11), VO2 (-0.04%, p = 0.80), and VCO2 (-1.03%, p = 0.09) showed no significant bias. The technical error (TE) ranged from 0.73% to 1.34% (VE and VCO2 respectively). MDC were lower than 4% (VE = 2.0%, VO2 = 3.8%, VCO2 = 3.7%). The intra and inter K5 reliability assessment reveled excellent ICCs (>0.99), MAPE <2% (no significant differences between trials), TE < or around 1%, MDC <or around 3%.ConclusionsK5 in BxB mode is a valid and reliable system for metabolic measurements. This is the first study assessing the MDC accounting only for technical variability reporting intra- and inter-units MDCs <3.3%.

Clinical validation of smartphone-based activity tracking in peripheral artery disease patients

Peripheral artery disease (PAD) is a vascular disease that leads to reduced blood flow to the limbs, often causing claudication symptoms that impair patients’ ability to walk. The distance walked during a 6-min walk test (6MWT) correlates well with patient claudication symptoms, so we developed the VascTrac iPhone app as a platform for monitoring PAD using a digital 6MWT. In this study, we evaluate the accuracy of the built-in iPhone distance and step-counting algorithms during 6MWTs. One hundred and fourteen (114) participants with PAD performed a supervised 6MWT using the VascTrac app while simultaneously wearing an ActiGraph GT9X Activity Monitor. Steps and distance-walked during the 6MWT were manually measured and used to assess the bias in the iPhone CMPedometer algorithms. The iPhone CMPedometer step algorithm underestimated steps with a bias of −7.2% ± 13.8% (mean ± SD) and had a mean percent difference with the Actigraph (Actigraph-iPhone) of 5.7% ± 20.5%. The iPhone CMPedometer distance algorithm overestimated distance with a bias of 43% ± 42% due to overestimation in stride length. Our correction factor improved distance estimation to 8% ± 32%. The Ankle-Brachial Index (ABI) correlated poorly with steps (R = 0.365) and distance (R = 0.413). Thus, in PAD patients, the iPhone’s built-in distance algorithm is unable to accurately measure distance, suggesting that custom algorithms are necessary for using iPhones as a platform for monitoring distance walked in PAD patients. Although the iPhone accurately measured steps, more research is necessary to establish step counting as a clinically meaningful metric for PAD.

Comparison of four clinically validated testosterone LC-MS/MS assays: Harmonization is an attainable goal

IntroductionImmunoassays and liquid chromatography-tandem mass spectrometry assays are commonly employed in clinical laboratories for measurement of total testosterone in serum. Results obtained from either of these methodologies compare poorly due to differences in calibration and/or inadvertent detection of interfering substances by the immunoassays. Standardization efforts are underway, but recent studies indicate that accuracy remains an issue. MethodsThis study compares the results from four independently developed and validated LC-MS/MS assays for total testosterone. The calibration for each assay was verified using National Institute of Standards and Technology Standard Reference Material 971. ResultsInitially, one of the four assays had a mean percent difference of +11.44%, compared to the All Method Mean, but following re-verification of all five non-zero calibrator concentrations with the NIST SRM 971, the mean percent difference decreased to −4.88%. Subsequently, the agreement between all four assays showed a mean bias of <5% across the range of all testosterone concentrations (0.13–38.10 nmol/L; 3.7–1098 ng/dL), including at low concentrations of <1 nmol/L (<29 ng/dL). ConclusionsExcellent agreement between four independently developed LC-MS/MS assays demonstrates that harmonization using standard reference material is attainable. However, as we found in this study, to ensure accurate calibration it is critical to validate the concentrations of new lots of calibrators.

142. DoseFX: A software for dosimetry of organs and lesions in molecular radiotherapy

PurposeThe primary objective was to validate the software DoseFX developed by Comecer for organ level dosimetry. Residence times (τ) and absorbed doses (D) to organs were compared to the quantities obtained with OLINDA1.1 and VoxelMed2.0 (voxel/organ-level dosimetry software). Methods and materialsSPECT/CT sequential dosimetry scans acquired in a PRRT trial were considered. Every patient was scanned 5 times after a therapeutic administration of 177Lu-DOTATOC. Two different clinical studies were performed. Study (A): the same activity values for the organs were used for the calculation of τ and D with DoseFX and OLINDA1.1 in a sample of 25 patients. Study (B): the same activity values for the organs were used with DoseFX and VoxelMed_Organ in a sample of 20 patients, while VoxelMed_Voxel works directly on images. For this study we did not calculate τ with OLINDA1.1, but we used τ calculated with VoxelMed_Organ. The Wilcoxon test was used (p-values in plots). ResultsThe mean percentage differences (PD) between DoseFX and OLINDA1.1 for the study (A) were (τ;D): −1.1;−1.3 liver, 0.1;0.1 kidney and −1.3;−1.3 spleen. For the study (B) mean PD between DoseFX and OLINDA1.1 were (τ;D): 5.4;4.2 liver, 0.0;2.7 kidney and 4.8;10.0 spleen; between DoseFX and VoxelMed2.0 were (τ;D): −0.7;9.8 liver, 0.6;13.8 kidney and 1.4;17.9 spleen. Data distribution in box plots.The study (A) showed a good agreement between DoseFX and OLINDA1.1 both for τ and for D, with mean PD smaller than 1%. In study (B) larger PDs were observed between DoseFX and VoxelMed, making them significantly different. This is most likely due to the different calculation modality of τ and D. ConclusionThe main conclusion is that DoseFX is a tool for organ dosimetry as safe as OLINDA1.1 in PRRT. Particular attention should be paid to the differences in the dosimetry calculation techniques implemented in available tools.

285. Dose indices in direct digital mammography: Evaluation on phantom and on a patient sample compared with the structured dose report values

Purpose In DR mammography, comparison of the Entrance Skin Dose (ESD) and the Average Glandular Dose (AGD) data provided by the structured dose report (SR) with the measures performed on phantom and on patient. Methods Two identical mammography systems, Amulet (Fujifilm), working in AEC with W/Rh spectrum and voltage range of 26–32 kV, were taken into account. For a PMMA phantom (18 × 24 cm2, thickness of 20–70 mm) and for a sample of 21 patients, both ESD and AGD were estimated. The X-ray output was measured, while Compressed Breast Thickness (CBT), age, tube loading and voltage were taken from the SR. The analysed images are 83, grouped by patient age and CBT. The backscatter factor for the ESD is 1.08. The AGD was estimated according to the “European guidelines for quality assurance in breast cancer screening and diagnosis” (2006 and updates) [1] . In the phantom case, the breast equivalent thickness was considered. In the patient case, the average output of the two systems was used. Results The table summarises estimated mean, SD and average percentage difference between SR and estimated values for ESD and AGD by patient age and CBT. In the graph, the percentage differences are reported as a function of CBT for both PMMA and patients. In the latter case, the data were separated by age range. Conclusions Both PMMA and patient ESD from the SR are an overestimation of the calculated value of at least 20% for all the CBT considered. Percentage differences of AGD are comprised within ±15% for CBT greater than 40 mm, while for smaller thicknesses an overestimation results in the range of 15%-25%. The split of the patient AGD curve may come from the mammography systems, which may not consider the patient age in the dose calculation (hypothesis to verify with the systems producer). Download : Download high-res image (161KB) Download : Download full-size image