Total-body dynamic PET/CT imaging reveals kinetic distribution of [13N]NH3 in normal organs.

PURPOSE: To systematically investigate kinetic metrics and metabolic trapping of [13N]NH3 in organs. METHODS: Eleven participants performed total-body [13N]NH3 dynamic positron emission tomography (PET). Regions of interest were drawn in organs to obtain time-to-activity curves (TACs), which were fitted with an irreversible two-tissue compartment model (2TC) to investigate constant rates K1, k2 and k3, and to calculate Ki. Additionally, one-tissue compartment model using full data (1TCfull) and the first four minutes of data (1TC4min) were fitted to TAC data. K1 and k2 were compared among different models to assess [13N]NH3 trapping in organs. RESULTS: Kinetic rates of [13N]NH3 varied significantly among organs. The mean K1 ranged from 0.049 mL/cm3/min in the muscle to 2.936 mL/cm3/min in the kidney. The k2 and k3 were lowest in the liver (0.001 min- 1) and in the pituitary (0.009 min- 1), while highest in the kidney (0.587 min- 1) and in the liver (0.800 min- 1), respectively. The Ki was largest in the myocardium (0.601 ± 0.259 mL/cm3/min) while smallest in the bone marrow (0.028 ± 0.022 mL/cm3/min). Three groups of organs with similar kinetic characteristics were revealed: (1) the thyroid, the lung, the spleen, the pancreas, and the kidney; (2) the liver and the muscle; and (3) the cortex, the white matter, the cerebellum, the pituitary, the parotid, the submandibular gland, the myocardium, the bone, and the bone marrow. Obvious k3 was identified in multiple organs, and significant changes of K1 in multiple organs and k2 in most organs were found between 2TC and 1TCfull, but both K1 and k2 were comparable between 2TC and 1TC4min. CONCLUSION: The kinetic rates of [13N]NH3 differed among organs with some have obvious 13N-anmmonia trapping. The normal distribution of kinetic metrics of 13N-anmmonia in organs can serve as a reference for its potential use in tumor imaging.

SUVmean ratios of liver/muscle and lung/muscle from 13N-NH3 PET perfusion outperformed traditional myocardial viability parameters in predicting survival after CABG.

PURPOSE: Myocardial viability evaluation in predicting survival after coronary artery bypass graft (CABG) remains debatable. Thus, this study aimed to investigate the role of 13N-NH3/18F-FDG PET myocardial viability scan in predicting treatment outcomes and survival. METHODS: 90 patients with CABG and pre-surgical PET-based myocardial viability scan were retrospectively reviewed. Perfusion-metabolism features, myocardium motion parameters, and patient characteristics were recorded. Additionally, the SUVmean of blood pool, lung, liver, spleen, and muscle were measured and the SUVmean ratios were calculated. Factors associated with treatment outcomes and survival were analyzed by Logistic and Cox regressions. Nomogram models were subsequently established to predict ejection fraction (EF) improvement and survival outcomes. RESULTS: The mean EF of these 90 patients was 38.1 ± 9.5% and 46.0 ± 9.2% before and after CABG surgery, and 35 patients (38.9%) achieved EF improvement ≥ 10%. EF measurements by PET and echocardiogram showed a reasonable linear correlation (R = 0.752). Sex, pre-surgical EF, mismatch of the left ventricle, total perfusion deficit (TPD), and peak ejection rate (PER) were independent predictive factors of EF improvements. Surgery waiting time, valve damage, and SUVmean ratio of Liver/Muscle were independently predictive of event-free survival (EFS), while valve damage, together with SUVmean ratio of either Liver/Muscle or Lung/Muscle, were independently predictive of overall survival (OS). CONCLUSION: Although traditional cardiac parameters from PET-based myocardial viability can effectively predict EF improvements after CABG, SUVmean ratios of liver/muscle and lung/muscle from 13N-NH3 PET perfusion outperformed these parameters in predicting survival.

Quantification of myocardial blood flow and myocardial flow reserve by 13N-NH3 PET/CT is not significantly affected by pixel size.

PURPOSE: Myocardial blood flow (MBF) and myocardial flow reserve (MFR) are measurable by 13N-NH3 positron emission tomography (PET). MFR, which is the ratio of MBF under adenosine stress to MBF at rest, is prognostically valuable. The ASNC imaging guidelines/SNMMI procedure standards recommend using 2-3 mm pixels, and pixel size does differ between institutions. We sought to evaluate the effects of pixel sizes on the quantitative values calculated from 13N-NH3 PET images. METHODS: Thirty consecutive patients with ischemic heart disease who underwent 13N-NH3 PET were retrospectively enrolled. Dynamic images were quantified using PMOD's cardiac PET analysis tool (pixel sizes: 3.18, 2.03, and 1.59 mm). MBF under adenosine stress, MBF at rest, and MFR for the right coronary artery (RCA) region, left anterior descending artery region, and left circumflex coronary artery branch region innervation regions were calculated at each pixel size and compared. RESULTS: Quantitative values did not significantly differ according to pixel size in any of the regions. However, MFR values for the RCA fluctuated the most. Ischemic and non-ischemic regions remained visually discernible in qualitative images, with no variation in quantitative values, regardless of pixel size. CONCLUSIONS: Quantitative values were not significantly affected by pixel sizes within the recommended range of 2-3 mm. Values for the RCA region may have been overestimated, but this was true for all pixel sizes.

An automatic segmentation method with self-attention mechanism on left ventricle in gated PET/CT myocardial perfusion imaging.

OBJECTIVES: We aimed to propose an automatic segmentation method for left ventricular (LV) from 16 electrocardiogram (ECG) -gated 13N-NH3 PET/CT myocardial perfusion imaging (MPI) to improve the performance of LV function assessment. METHODS: Ninety-six cases with confirmed or suspected obstructive coronary artery disease (CAD) were enrolled in this research. The LV myocardial contours were delineated by physicians as ground truth. We developed an automatic segmentation method, which introduces the self-attention mechanism into 3D U-Net to capture global information of images so as to achieve fine segmentation of LV. Three cross-validation tests were performed on each gate (64 vs. 32 for training vs. validation). The effectiveness was validated by quantitative metrics (modified hausdorff distance, MHD; dice ratio, DR; 3D MHD) as well as cardiac functional parameters (end-systolic volume, ESV; end-diastolic volume, EDV; ejection fraction, EF). Furthermore, the feasibility of the proposed method was also evaluated by intra- and inter-observers with DR and 3D-MHD. RESULTS: Compared with backbone network, the proposed approach improved the average DR from 0.905 ± 0.0193 to 0.9202 ± 0.0164, and decreased the average 3D MHD from 0.4611 ± 0.0349 to 0.4304 ± 0.0339. The average relative error of LV volume between proposed method and ground truth is 1.09±3.66%, and the correlation coefficient is 0.992 ± 0.007 (P < 0.001). The EDV, ESV, EF deduced from the proposed approach were highly correlated with ground truth (r ≥ 0.864, P < 0.001), and the correlation with commercial software is fair (r ≥ 0.871, P < 0.001). DR and 3D MHD of contours and myocardium from two observers are higher than 0.899 and less than 0.5194. CONCLUSION: The proposed approach is highly feasible for automatic segmentation of the LV cavity and myocardium, with potential to benefit the precision of LV function assessment.

Assessment of left and right ventricular functional parameters using dynamic dual-tracer [13N]NH3 and [18F]FDG PET/MRI.

BACKGROUND: Cardiac positron emission tomography/magnetic resonance imaging (PET/MRI) can assess various cardiovascular diseases. In this study, we intra-individually compared right (RV) and left ventricular (LV) parameters obtained from dual-tracer PET/MRI scan. METHODS: In 22 patients with coronary heart disease (69 ± 9 years) dynamic [13N]NH3 (NH3) and [18F]FDG (FDG) PET scans were acquired. The first 2 minutes were used to calculate LV and RV first-pass ejection fraction (FPEF). Additionally, LV end-systolic (LVESV) and end-diastolic (LVEDV) volume and ejection fraction (LVEF) were calculated from the early (EP) and late-myocardial phases (LP). MRI served as a reference. RESULTS: RVFPEF and LVFPEF from FDG and NH3 as well as RVEF and LVEF from MRI were (28 ± 11%, 32 ± 15%), (32 ± 11%, 41 ± 14%) and (42 ± 16%, 45 ± 19%), respectively. LVESV, LVEDV and LVEF from EP FDG and NH3 in 8 and 16 gates were [71 (15 to 213 mL), 98 (16 to 241 mL), 32 ± 17%] and [50 (17 to 206 mL), 93 (13 to 219 mL), 36 ± 17%] as well as [60 (19 to 360 mL), 109 (56 to 384 mL), 41 ± 22%] and [54 (16 to 371 mL), 116 (57 to 431 mL), 46 ± 24%], respectively. Moreover, LVESV, LVEDV and LVEF acquired from LP FDG and NH3 were (85 ± 63 mL, 138 ± 63 mL, 47 ± 19%) and (79 ± 56 mL, 137 ± 63 mL, 47 ± 20%), respectively. The LVESV, LVEDV from MRI were 93 ± 66 mL and 153 ± 71 mL, respectively. Significant correlations were observed for RVFPEF and LVFPEF between FDG and MRI (R = .51, P = .01; R = .64, P = .001), respectively. LVESV, LVEDV, and LVEF revealed moderate to strong correlations to MRI when they acquired from EP FDG and NH3 in 16 gates (all R > .7, P = .000). Similarly, all LV parameters from LP FDG and NH3 correlated good to strongly positive with MRI (all R > .7, and P < .001), except EDV from NH3 weakly correlated to EDV of MRI (R = .54, P < .05). Generally, Bland-Altman plots showed good agreements between PET and MRI. CONCLUSIONS: Deriving LV and RV functional values from various phases of dynamic NH3 and FDG PET is feasible. These results could open a new perspective for further clinical applications of the PET examinations.

Comparison of left ventricle mechanical dyssynchrony parameters in ischemic and non-ischemic patients using 13N-NH3 PET/CT.

BACKGROUND-AIM: The relationship between perfusion pattern and stress-induced changes in Left Ventricular Mechanical Dyssynchrony (LVMD) has been previously described with controversial results using stress-rest perfusion imaging studies. The aim of this study was to assess the relationship between perfusion pattern and stress-induced changes in LVMD usingo regadenoson/rest13N-NH3 PET/CT. METHODS: There were 74 patients who underwent stress-rest 13N-NH PET/CT from January 2014 to October 2018 excluding patients with left bundle branch block, ventricular pacing and myocardial necrosis. The patients were divided into those with reversible perfusion defects at stress (Ischemic group, n = 18) and patients without reversible perfusion defects (non-ischemic group, n = 56). The LVMD parameters included: phase standard deviation (PSD) and phase histogram bandwidth (PHB), after stress and at rest. The ΔPSD (post-stressPSD-restPSD) and ΔPHB (post-stressPHB-restPHB) were calculated to measure stress-induced changes in LVMD. RESULTS: There were no significant differences in LVMD parameters between post-stress and at rest in both groups. The PSD post-stress, ΔPSD and PHB post-stress were significantly higher in the ischemic group. CONCLUSIONS: Using a vasodilator as a stress, the PSD and PHB post-stress and ΔPSD were significantly higher in the ischemic patients than the non-ischemic group, while there were no significant differences in each cohort between stress and rest indices.

Identify glioma recurrence and treatment effects with triple-tracer PET/CT.

BACKGROUND: Differential diagnosis of tumour recurrence (TuR) from treatment effects (TrE), mostly induced by radiotherapy and chemotherapy, is still difficult by using conventional computed tomography (CT) or magnetic resonance (MR) imaging. We have investigated the diagnostic performance of PET/CT with 3 tracers, 13N-NH3, 18F-FDOPA, and 18F-FDG, to identify TuR and TrE in glioma patients following treatment. METHODS: Forty-three patients with MR-suspected recurrent glioma were included. The maximum and mean standardized uptake values (SUVmax and SUVmean) of the lesion and the lesion-to-normal grey-matter cortex uptake (L/G) ratio were obtained from each tracer PET/CT. TuR or TrE was determined by histopathology or clinical MR follow-up for at least 6 months. RESULTS: In this cohort, 34 patients were confirmed to have TuR, and 9 patients met the diagnostic standard of TrE. The SUVmax and SUVmean of 13N-NH3 and 18F-FDOPA PET/CT at TuR lesions were significantly higher compared with normal brain tissue (13N-NH3 0.696 ± 0.558, 0.625 ± 0.507 vs 0.486 ± 0.413; 18F-FDOPA 0.455 ± 0.518, 0.415 ± 0.477 vs 0.194 ± 0.203; both P < 0.01), but there was no significant difference in 18F-FDG (6.918 ± 3.190, 6.016 ± 2.807 vs 6.356 ± 3.104, P = 0.290 and 0.493). L/G ratios of 13N-NH3 and 18F-FDOPA were significantly higher in TuR than in TrE group (13N-NH3, 1.573 ± 0.099 vs 1.025 ± 0.128, P = 0.008; 18F-FDOPA, 2.729 ± 0.131 vs 1.514 ± 0.141, P < 0.001). The sensitivity, specificity and AUC (area under the curve) by ROC (receiver operating characteristic) analysis were 57.7%, 100% and 0.803, for 13N-NH3; 84.6%, 100% and 0.938, for 18F-FDOPA; and 80.8%, 100%, and 0.952, for the combination, respectively. CONCLUSION: Our results suggest that although multiple tracer PET/CT may improve differential diagnosis efficacy, for glioma TuR from TrE, 18F-FDOPA PET-CT is the most reliable. The combination of 18F-FDOPA and 13N-NH3 does not increase the diagnostic efficiency, while 18F-FDG is not worthy for differential diagnosis of glioma TuR and TrE.

Longitudinal [18F]FDG and [13N]NH3 PET/CT imaging of brain and spinal cord in a canine hemisection spinal cord injury model.

To further understand the neurological changes induced by spinal cord injury (SCI) in its acute and subacute stages, we evaluated longitudinal changes in glucose and glutamate metabolism in the spinal cord and brain regions of a canine hemisection SCI model. [18F]FDG and [13N]NH3 positron-emission tomography (PET) with computed tomography (CT) was performed before SCI and at 1, 3, 7, 14, and 21 days after SCI. Spinal cord [18F]FDG uptake increased and peaked at 3 days post SCI. Similar changes were observed in the brain regions but were not statistically significant. Compared to the acute phase of SCI, [13N]NH3 uptake increased in the subacute stage and peaked at 7 days post SCI in all analyzed brain regions. But in spinal cord, no [13N]NH3 uptake was detected before SCI when the blood-spinal cord barrier (BSCB) was intact, then gradually increased when the BSCB was damaged after SCI. [13N]NH3 uptake was significantly correlated with plasma levels of the BSCB disruption marker, monocyte chemoattractant protein-1 (MCP-1). Overall, we showed that SCI induced in vivo changes in glucose uptake in both the spinal cord and the examined brain regions, and changes in glutamine synthetase activity in the latter. Moreover, our results suggest that [13N]NH3 PET may serve as a potential method for assessing BSCB permeability in vivo.

Changes of δ15N values during the volatilization process after applying urea on soil.

Ammonia (NH3) volatilized from soils plays an important role in N cycle and air pollution, thus it is important to trace the emission source and predict source contributions to development strategies mitigating the environmental harmful of soil NH3 volatilization. The measurements of 15N natural abundance (δ15N) could be used as a complementary tool for apportioning emissions sources to resolve the contribution of multiple NH3 emission sources to air NH3 pollution. However, information of the changes of δ15N-NH3 values during the whole volatilization process under different N application rates are currently lacking. Hence, to fill this gap, we conducted a 15-day incubation experiment included different urea-N application rates to determine δ15N values of NH3 during volatilization process. Results showed that volatilization process depleted 15N in NH3. The average δ15N value of NH3 volatilized from the 0, 20, 180, and 360 kg N ha-1 treatment was -16.2 ± 7.3‰, -26.0 ± 5.4‰, -34.8 ± 4.8‰, and -40.6 ± 5.7‰. Overall, δ15N-NH3 values ranged from -46.0‰ to -4.7‰ during the whole volatilization process, with lower in higher urea-N application treatments than those in control. δ15N-NH3 values during the NH3 volatilization process were much lower than those of the primary sources, soil (-3.4 ± 0.1‰) and urea (-3.6 ± 0.1‰). Therefore, large isotopic fractionation may occur during soil volatilization process. Moreover, negative relationships between soil NH4+-N and NH3 volatilization rate and δ15N-NH3 values were observed in this study. Our results could be used as evidences of NH3 source apportionments and N cycle.

Preliminary and Comparative Experiment Study Between 18F-Flurpiridaz and 13N-NH3·H2O Myocardial Perfusion Imaging With PET/CT in Miniature Pigs.

OBJECTVES: To comparatively explore the differences between 18F-Flurpiridaz and 13N-NH3·H2O PET/CT myocardial perfusion imaging in miniature pigs. METHODS: Ten Bama minipigs were divided into normal group and myocardial infarction group. The changes of the ratio of left ventricular myocardium to main organs with time were calculated and the best imaging time was confirmed for 18F-Flurpiridaz imaging in normal group. The image quality score, summed rest score(SRS), Extend, total perfusion deficit(TPD) and left ventricle ejection fraction(LVEF) were respectively compared for 18F-Flurpiridaz and 13N-NH3·H2O in infarction group. RESULTS: 18F-Flurpiridaz was rapid distributed in myocardium, and the background counts of cardiac cavity were very low, and no obvious interference extracardiac radioactivity was observed. The radioactive ratio of the left ventricular myocardium to cardiac blood pool and adjacent liver were high. Compared with 13N-NH3·H2O, there were no significant differences in functional parameters, including SRS, Extend, TPD and LVEF. CONCLUSION: The results preliminaryly show that 18F-FIurpiridaz is a promising positron MPI agent with good image quality, ability of accurately evaluating cardiac function, and also convenience for application.

Development, validation and regulatory acceptance of improved purification and simplified quality control of [13N] Ammonia.

BACKGROUND: [13N]Ammonia is a cyclotron produced myocardial perfusion imaging agent. With the development of high-yielding [13N]ammonia cyclotron targets using a solution of 5 mM ethanol in water, there was a need to develop and validate an automated purification and formulation system for [13N]ammonia to be in a physiological compatible formulation of 0.9% sodium chloride since there is no widely available commercial system at this time. Due to its short half-life of 10 min, FDA and USP regulations allow [13N]ammonia to be tested in quality control (QC) sub-batches with limited quality control testing performed on the sub-batches for patient use. The current EP and the original USP method for the determination of the radiochemical purity and identity of [13N]ammonia depended on an HPLC method using a conductivity detector and a solvent free of other salts. This HPLC method created issues in a modern cGMP high volume PET manufacturing facility where the HPLC is used with salt containing mobile phase buffers for quality control analysis of other PET radiopharmaceuticals. Flushing of the HPLC system of residual salt buffers which may interfere with the [13N]ammonia assay can take several hours of instrument time. Since there are no mass limits on [13N]ammonia, a simplified TLC assay to determine radiochemical identity and purity could be developed to simplify and streamline QC. RESULTS: We have developed and validated a streamlined automated synthesis for [13N]ammonia which provides the drug product in 8 mL of 0.9% sodium chloride for injection. A novel radio-TLC method was developed and validated to demonstrate feasibility to quantitate [13N]ammonia and separate it from all known radiochemical impurities. CONCLUSIONS: The process for automated synthesis of [13N]ammonia simplifies and automates the purification and formulation of [13N]ammonia in a cGMP compliant manner needed for high-throughput manufacture of [13N]ammonia. The novel radio-TLC method has simplified [13N]ammonia quality control (QC) and now enables it to be tested using the same QC equipment as [18F]fludeoxyglucose (FDA/USP recognized name for 2-[18F]fluoro-2-deoxy-D-glucose). Both the streamlined automated synthesis of [13N]ammonia and the novel radio-TLC method have been accepted and approved by the US Food and Drug Administration (FDA) for the cGMP manufacture of [13N]ammonia.

Chrysotile asbestos treated with phosphoric acid as an adsorbent for ammonia nitrogen.

The purpose of this study was to find an alternative application for chrysotile asbestos, given that there is a complete structure of extraction and production of this class of serpentine minerals, but its use is banned for many applications. The idea was to obtain a compound that could immobilize phosphate by triggering a reaction between the magnesium oxide and hydroxide contained in the mineral, without causing phosphate leaching. To this end, chrysotile (Mg3SiO5(OH)4) was treated with phosphoric acid (H3PO4) in a molar ratio of 1:3 in an aqueous medium at 85 °C until the solvent evaporated, resulting in two different solid compounds, which were prepared in a similar manner. The first compound (cri/H3PO4 1:3)1, was obtained by rinsing and then heat-treating it at 150 °C for 6 h, while the second one, (cri/H3PO4 1:3)2, was rinsed after the heat treatment. Compound (cri/H3PO4 1:3)1 underwent partial leaching, while compound (cri/H3PO4 1:3)2 showed a mass increase of 48%, with the formation of crystalline magnesium pyrophosphate mixed with amorphous SiO2. The latter compound adsorbed N-NH3 at pH 10, following the pseudo-first-order model (activation energy = 8329 ± 1696 J mol-1). Equilibrium experiments, which were performed following Hill's sigmoidal type S2 isotherm model, indicated that the adsorption phenomenon was governed by two processes, i.e., complexation up to the inflection point (KH between 10.0 mg L-1 at 40 °C and 13.6 mg L-1 at 25 °C) followed by adsorption. The qmax varied from 18.0 to 19.6 mgN g-1 and the adsorbent was reusable, maintaining its initial adsorbent capacity during its first reuse. This material, which was tested on real effluents, presented a N-NH3 removal rate similar to that shown by the test solutions. The treatment of chrysotile with H3PO4 conducts it to a composite that adsorbs ammoniacal nitrogen at pH 10 and it is reusable maintaining the adsorption capacity.

13N-NH3 PET/CT in oncological disease.

13N-Ammonia (13N-NH3) is widely used positron emission tomography/computed tomography (PET/CT) radiotracer for the measurement of myocardial blood perfusion; the possible role of 13N-NH3 PET or PET/CT in oncological disease is not yet clear. Aim of this review is to evaluate the diagnostic performances of 13N-NH3 PET in this field. A comprehensive computer literature search of the PubMed/MEDLINE, Scopus, and Embase databases was conducted including articles up to June 2019. Eighteen articles were finally included in the review. From the analyses of the selected studies, the following main findings could be drawn: (1) 13N-NH3 PET is useful in discriminating between gliomas and non-neoplastic brain lesions, and among gliomas between high-grade and low-grade gliomas; (2) 13N-NH3 PET have better diagnostic performance than 18F-FDG in studying gliomas; (3) a combination of 13N-NH3 PET and 18F-FDG PET may be useful to differentiate between several cerebral lesions (gliomas, cerebral lymphoma, meningioma); (4) only preliminary results about the positive impact in liver and prostate cancer.

Diagnostic accuracy of 13N-ammonia PET, 11C-methionine PET and 18F-fluorodeoxyglucose PET: a comparative study in patients with suspected cerebral glioma.

BACKGROUND: The treatment of patients with glioma depended on the nature of the lesion and on histological grade of the tumor. Positron emission tomography (PET) using 13N-ammonia (NH3), 11C-methionine (MET) and 18F-fluorodeoxyglucose (FDG) have been used to assess brain tumors. Our aim was to compare their diagnostic accuracies in patients with suspected cerebral glioma. METHODS: Ninety patients with suspicion of glioma based on previous CT/MRI, who underwent NH3 PET, MET PET and FDG PET, were prospectively enrolled in the study. The reference standard was established by histology or clinical and radiological follow-up. Images were interpreted by visual evaluation and semi-quantitative analysis using the lesion-to-normal white matter uptake ratio (L/WM ratio). RESULTS: Finally, 30 high-grade gliomas (HGG), 27 low-grade gliomas (LGG), 10 non-glioma tumors and 23 non-neoplastic lesions (NNL) were diagnosed. On visual evaluation, sensitivity and specificity for differentiating tumors from NNL were 62.7% (42/67) and 95.7% (22/23) for NH3 PET, 94.0% (63/67) and 56.5% (13/23) for MET PET, and 35.8% (24/67) and 65.2% (15/23) for FDG PET. On semi-quantitative analysis, brain tumors showed significantly higher L/WM ratios than NNL both in NH3 and MET PET (both P < 0.001). The sensitivity, specificity and the area under the curve (AUC) by receiver operating characteristic (ROC) analysis, respectively, were 64.2, 100% and 0.819 for NH3; and 89.6, 69.6% and 0.840 for MET. Besides, the L/WM ratios of NH3, MET and FDG PET in HGG all significantly higher than that in LGG (all P < 0.001). The predicted (by ROC) accuracy of the tracers (AUC shown in parentheses) were 86.0% (0.896) for NH3, 87.7% (0.928) for MET and 93.0% (0.964) for FDG. While no significant differences in the AUC were seen between them. CONCLUSION: NH3 PET has remarkably high specificity for the differentiation of brain tumors from NNL, but low sensitivity for the detection of LGG. MET PET was found to be highly useful for detection of brain tumors. However, like FDG, high MET uptake is frequently observed in some NNL. NH3, MET and FDG PET all appears to be valuable for evaluating the histological grade of gliomas.

Relationship Between Ktrans and K1 with Simultaneous Versus Separate MR/PET in Rabbits with VX2 Tumors.

BACKGROUND/AIM: To compare the relationship between Ktrans from DCE-MRI and K1 from dynamic 13N-NH3-PET, with simultaneous and separate MR/PET in the VX-2 rabbit carcinoma model. MATERIALS AND METHODS: MR/PET was performed simultaneously and separately, 14 and 15 days after VX-2 tumor implantation at the paravertebral muscle. The Ktrans and K1 values were estimated using an in-house software program. The relationships between Ktrans and K1 were analyzed using Pearson's correlation coefficients and linear/non-linear regression function. RESULTS: Assuming a linear relationship, Ktrans and K1 exhibited a moderate positive correlations with both simultaneous (r=0.54-0.57) and separate (r=0.53-0.69) imaging. However, while the Ktrans and K1 from separate imaging were linearly correlated, those from simultaneous imaging exhibited a non-linear relationship. The amount of change in K1 associated with a unit increase in Ktrans varied depending on Ktrans values. CONCLUSION: The relationship between Ktrans and K1 may be mis-interpreted with separate MR and PET acquisition.

Use of Nitrogen Isotope To Determine Fertilizer- and Soil-Derived Ammonia Volatilization in a Rice/Wheat Rotation System.

The nitrogen (N) isotope method reveals that application of fertilizer N can increase crop uptake or denitrification and leaching losses of native soil N via the "added N interaction". However, there is currently little evidence of the impact of added N on soil N losses through NH3 volatilization using (15)N methodologies. In the present study, a three-year rice/wheat rotated experiment with 30% (15)N-labeled urea applied in the first rice season and unlabeled urea added in the following five crop seasons was performed to investigate volatilization of NH3 from fertilizer and soil N. We found 9.28% of NH3 loss from (15)N urea and 2.88-7.70% declines in (15)N-NH3 abundance occurred during the first rice season, whereas 0.11% of NH3 loss from (15)N urea and 0.02-0.21% enrichments in (15)N-NH3 abundance happened in the subsequent seasons. The contributions of fertilizer- and soil-derived N to NH3 volatilization from a rice/wheat rotation were 75.8-88.4 and 11.6-24.2%, respectively. These distinct variations in (15)N-NH3 and substantial soil-derived NH3 suggest that added N clearly interacts with the soil source contributing to NH3 volatilization.

Intake and digestibility, rumen fermentation, and concentrations of metabolites in steers fed with peanut cake.

This study evaluated peanut cake as a replacement for soybean meal in the diet of steers. We used five castrated Holstein × Zebu steers, fistulated, with average live weight 550 kg, in a 5 × 5 Latin square design. The diets were composed of Tifton hay and ground corn with peanut cake (0, 25, 50, 75, and 100 %) as a replacement for soybean meal in the concentrate. Intake (kg/day) of dry matter, neutral detergent fiber, and crude protein were not affected by peanut cake, but ether extract intake increased linearly with the level of peanut cake in the diet. The digestibility of dry matter showed a quadratic effect, with a calculated maximum regression level of 56 % at 37 % replacement. There was no effect of the level of peanut cake on metabolizable energy intake and net energy, ammonia nitrogen, rumen pH, plasma urea, and glucose concentrations. We recommend replacing soybean meal in the concentrate with up to 40 % peanut cake.

The reproducibility of time-of-flight PET and conventional PET for the quantification of myocardial blood flow and coronary flow reserve with (13)N-ammonia.

BACKGROUND: This study aimed to validate the reproducibility of quantitative analysis using time-of-flight (TOF) and conventional PET with (13)N-ammonia ((13)N-NH3). METHODS AND RESULTS: Phantom images were reconstructed with and without TOF, and recovery coefficients (RCs) and the percent contrast of each sphere over the percent background variability were assessed. In the clinical study, 21 subjects underwent dynamic (13)N-NH3 PET scanning under stress and rest conditions. The dynamic acquisition images and intra- and inter-observer reproducibility of myocardial blood flow (MBF) and coronary flow reserve (CFR) were compared between reconstructions (with and without TOF). In the phantom study, RCs and the percent contrast of each sphere over the percent background variability was improved with TOF. In the clinical study, the noise of blood pool and myocardial images with TOF was less than that without TOF. Territorial and global intra- and inter-observer reproducibility of MBF and CFR values was excellent. Although segmental intra- and inter-observer reproducibility was excellent, there were larger variations in apex and the segment near the right ventricle (RV) without TOF. These variations became inconspicuous with TOF. CONCLUSION: Visual image quality, RCs, and percent contrast over percent background variability with TOF were better than that without TOF. Excellent correlations and good agreements in quantitative values were observed. TOF improved the variation of segmental values.

Decomposição, liberação e volatilização de nitrogênio em resíduos culturais de mucuna-cinza (Mucuna cinerea) / Decomposition, release and volatilization of nitrogen from velvet bean (Mucuna cinerea) residues

As leguminosas possibilitam a incorporação biológica de nitrogênio aos sistemas de produção. Contudo, existe pouco conhecimento sobre a decomposição, liberação e volatilização de nitrogênioassociados à diferentes doses de seus resíduos. Objetivouse, neste trabalho avaliar a decomposição, a liberação e a volatilização de nitrogênio de diferentes doses de mucuna-cinza (Mucuna cinerea Piper & Tracy). O experimento constou de tratamentos com 12 (C12) ou 25 (C25) Mg ha-1 de composto orgânico: C12AV0 (sem leguminosa); C12AV4 (4 Mg ha-1 de resíduo); C12AV8 (8 Mg ha-1); C12AV12 (12 Mg ha-1); C25; AV12 (12 Mg ha-1) e testemunha absoluta. Adotou-se o delineamento de blocos casualizados e cinco repetições. Foram determinadas as taxas de decomposição do adubo verde e liberação de N, o teor de N-mineral no solo e a volatilização de N-NH3. A liberação de N (t½=28 dias) foi mais rápida que a decomposição do resíduo (t½=38 dias). Essa liberação de N eleva rapidamente os teores de N-mineral do solo e resulta também em maior elevação da volatilização de N-NH3. O incremento das doses de 8 para 12 Mg ha-1 de mucuna resultou em aumento mais que proporcional da volatilização acumulada de N-NH3, atingindo 30 kg ha-1 após 30 dias.

The use of leguminous species allows the biological incorporation of nitrogen into cropping systems. Nevertheless, there is little knowledge about the decomposition, release and volatilization of nitrogen associated with the decomposition of different quantities of residues. The objective of this study was to evaluate the decomposition of the biomass, the release and volatilization of nitrogen from different doses of velvet bean (Mucuna cinerea Piper & Tracy) residues. The treatments were established either with 12 (C12) or 25 (C25) Mg ha-1 of organic compost: C12AV0 (without residue); C12AV4 (4 Mg ha-1 of residue); C12AV8 (8 Mg ha-1); C12AV12 (12 Mg ha-1); C25; AV12 (12 Mg ha-1) and a control. The randomized block design was adopted with five repetitions. Mass dry matter decomposition and N release rate, the soil N-mineral content and N-NH3 volatilization were determined. N mineralization (t ½= 28 days) was faster than the decomposition of dry matter (t ½=38 days). This mineralization rapidly increased the soil mineral-N content and resulted in higher N-NH3 volatilization. However, the increase from 8 to 12 Mg ha-1 of velvet bean mass resulted in an overproportional increase of N-NH3 volatilization, which reached 30 kg ha-1 after 30 days.

Frações nitrogenadas de silagens de milho "safrinha" sob diferentes tempos de exposição ao ar antes da ensilagem / Nitrogenous fractions of silages from a maize crop planted late in season, under different periods of air exposure previous to ensiling

Objetivou-se avaliar o efeito da maturidade dos grãos de milho e do tempo de exposição ao ar antes da ensilagem sobre o pH e os componentes nitrogenados de silagens de milho "safrinha". O experimento foi conduzido em delineamento completamente casualizado com arranjo fatorial 2 x 4, no qual foram testados dois estádios de maturidade (MA) ao corte (grão completamente leitoso (GL) ou grão ½ leitoso ½ farináceo (GF)) e quatro tempos de exposição ao ar (EX), sem compactação (0, 12, 24 e 36 horas) antes da ensilagem em minissilos. Houve efeito significativo (P<0,05) em relação aos MA e EX, para os teores de PB e NIDN, além de interação entre esses fatores para as variáveis pH, N-NH3 e NIDA. Devido à interação, a silagem feita no estádio GL produziu mais N-NH3 do que aquelas feitas no estádio GF. A interação entre os fatores MA e EX aumentam o valor médio de pH das silagens produzidas, porém com diferentes magnitudes. O manejo inadequado na ensilagem decorrente da demora no enchimento do silo aumenta a fração nitrogenada insolúvel, ou seja, diminui a degradabilidade protéica, porém afeta negativamente a digestibilidade e o valor nutritivo da silagem. Silagens de milho colhidas com grão leitoso comprometem a palatabilidade pelo maior teor de nitrogênio amoniacal.

This experiment was aimed at evaluating the effect of corn grain maturity and air exposure time prior to ensiling on the pH and nitrogenous fractions of corn silage from corn crop planted late in the season. A completely randomized 2 x 4 factorial arrangement was used to test the effect of two maturity stages at harvest (GL, milky kernel and GF, ½ milky ½ dough kernel) of maize crops and the effects of four periods of air exposure of chopped materials (zero, 12, 24 and 36 hours) previous to packing in mini-silos, on pH and N fractions of silages. There was a significant effect (P<0.05) related to stage of maturity and period of air exposure concerning the contents of crude protein and neutral detergent insoluble nitrogen, as well as an interaction between the main effects for ammonia nitrogen and acid detergent insoluble nitrogen. Due to the interaction, the maize silage harvested at the milky kernel stage resulted in higher pH value and ammonia nitrogen contents. A delayed packing procedure increases the insoluble nitrogen fractions and may affect negatively protein digestibility.