Within the EXPLORER Consortium, the construction of the world's first total-body PET/CT scanner has recently been completed. The 194-cm axial field of view of the EXPLORER PET/CT scanner is ...sufficient to cover, for the first time, the entire human adult body in a single acquisition in more than 99% of the population and allows total-body pharmacokinetic studies with frame durations as short as 1 s. The large increase in sensitivity arising from total-body coverage as well as increased solid angle for detection at any point within the body allows whole-body
F-FDG PET studies to be acquired with unprecedented count density, improving the signal-to-noise ratio of the resulting images. Alternatively, the sensitivity gain can be used to acquire diagnostic PET images with very small amounts of activity in the field of view (25 MBq, 0.7 mCi or less), with very short acquisition times (∼1 min or less) or at later time points after the tracer's administration. We report here on the first human imaging studies on the EXPLORER scanner using a range of different protocols that provide initial evidence in support of these claims. These case studies provide the foundation for future carefully controlled trials to quantitatively evaluate the improvements possible through total-body PET imaging.
Parametric imaging has been shown to provide better quantitation physiologically than SUV imaging in PET. With the increased sensitivity from a recently developed total-body PET scanner, whole-body ...scans with higher temporal resolution become possible for dynamic analysis and parametric imaging. In this paper, we focus on deriving the parameter k1 using compartmental modeling and on developing a method to acquire whole-body 18F-FDG PET parametric images using only the first 90 s of the postinjection scan data with the total-body PET system. Methods: Dynamic projections were acquired with a time interval of 1 s for the first 30 s and a time interval of 2 s for the following minute. Image-derived input functions were acquired from the reconstructed dynamic sequences in the ascending aorta. A 1-tissue-compartment model with 4 parameters (k1, k2, blood fraction, and delay time) was used. A maximum-likelihood–based estimation method was developed with the 1-tissue-compartment model solution. The accuracy of the acquired parameters was compared with the ones estimated using a 2-tissue-compartment irreversible model with 1-h-long data. Results: All 4 parametric images were successfully calculated using data from 2 volunteers. By comparing the time–activity curves acquired from the volumes of interest, we showed that the parameters estimated using our method were able to predict the time–activity curves of the early dynamics of 18F-FDG in different organs. The delay-time effects for different organs were also clearly visible in the reconstructed delay-time image with delay variations of as large as 40 s. The estimated parameters using both 90-s data and 1-h data agreed well for k1 and blood fraction, whereas a large difference in k2 was found between the 90-s and 1-h data, suggesting k2 cannot be reliably estimated from the 90-s scan. Conclusion: We have shown that with total-body PET and the increased sensitivity, it is possible to estimate parametric images based on the very early dynamics after 18F-FDG injection. The estimated k1 might potentially be used clinically as an indicator for identifying abnormalities.
Background
Recently, the randomized EINSTEIN‐Jr study showed similar efficacy and safety for rivaroxaban and standard anticoagulation for treatment of pediatric venous thromboembolism (VTE). The ...rivaroxaban dosing strategy was established based on phase 1 and 2 data in children and through pharmacokinetic (PK) modeling.
Methods
Rivaroxaban treatment with tablets or the newly developed granules‐for‐oral suspension formulation was bodyweight‐adjusted and administered once‐daily, twice‐daily, or thrice‐daily for children with bodyweights of ≥30, ≥12 to <30, and <12 kg, respectively. Previously, these regimens were confirmed for children weighing ≥20 kg but only predicted in those <20 kg. Based on sparse blood sampling, the daily area under the plasma concentration–time curve AUC(0‐24)ss and trough Ctrough,ss and maximum Cmax,ss steady‐state plasma concentrations were derived using population PK modeling. Exposure‐response graphs were generated to evaluate the potential relationship of individual PK parameters with recurrent VTE, repeat imaging outcomes, and bleeding or adverse events. A taste‐and‐texture questionnaire was collected for suspension‐recipients.
Results
Of the 335 children (aged 0‐17 years) allocated to rivaroxaban, 316 (94.3%) were evaluable for PK analyses. Rivaroxaban exposures were within the adult exposure range. No clustering was observed for any of the PK parameters with efficacy, bleeding, or adverse event outcomes. Results were similar for the tablet and suspension formulation. Acceptability and palatability of the suspension were favorable.
Discussion
Based on this analysis and the recently documented similar efficacy and safety of rivaroxaban compared with standard anticoagulation, we conclude that bodyweight‐adjusted pediatric rivaroxaban regimens with either tablets or suspension are validated and provide for appropriate treatment of children with VTE.
•Fate of 26 PPCPs in 13 full-scale nitrogen removing biofilters (NRBs) was studied.•The innovative onsite wastewater system, NRB, removed 58 to >99% of PPCPs.•19 of the PPCPs were removed by 50 to ...>99% within the oxic layer of the NRBs.•NRBs performed as well as or better than conventional wastewater treatment systems.
The presence of pharmaceuticals and personal care products (PPCPs) in the environment is primarily the result of discharge of waste, including from onsite wastewater treatment systems (OWTSs) which are employed by 25% of homes in the United States. However, the occurrence and removal of PPCPs in OWTSs is not well understood, particularly given the large diversity in PPCP compounds as well as in OWTS designs. In this study, we monitored 26 different PPCPs in 13 full-scale nitrogen removing biofilters (NRBs), an innovative/alternative type of OWTS that utilizes an overlying sand layer and an underlying woodchip/sand layer to simultaneously remove nitrogen and other wastewater-derived contaminants. The specific objectives of this study were (i) to measure the occurrence of PPCPs in septic tank effluent (STE) that served as an influent to NRBs, (ii) to quantify PPCP removal in three types of NRB configurations (n = 13), and (iii) to evaluate PPCP removal with depth and environmental conditions in NRBs. Aqueous samples were taken during 42 separate sampling events during 2016 – 2019 and analyzed by liquid chromatography tandem mass spectrometry. Analysis of the STE samples yielded detection of 23 of the 26 PPCPs, with caffeine being the most abundant and frequently detected compound at 52,000 ng/L (range: 190 – 181,000 ng/L), followed by acetaminophen and paraxanthine at 47,500 ng/L (190 – 160,000 ng/L), and 34,300 ng/L (430 – 210,000 ng/L), respectively. Cimetidine, fenofibrate, and warfarin were the only compounds not detected. The average removal of PPCPs by NRBs ranged from 58% to >99% for the various compounds. PPCP removal as a function of depth in the systems showed that 50 to >99% of the observed removal was achieved within the top oxic layer (0 - 46 cm) of the NRBs for 19 analytes. Seven of the compounds had >85% removal by the same depth. These results indicate that NRBs are effective at removing PPCPs and that a large portion of the removal is achieved within the oxic nitrifying layer of the NRBs. Overall, the removal of PPCPs in NRBs was comparable (n = 8) or better (n = 15) than that observed for conventional wastewater treatment plants.
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Difficulties in direct measurement of drug concentrations in human tissues have hampered the understanding of drug accumulation in tumors and normal tissues. We propose a new system analysis modeling ...approach to characterize drug distribution in tissues based on human positron emission tomography (PET) data. The PET system analysis method was applied to temozolomide, an important alkylating agent used in the treatment of brain tumors, as part of standard temozolomide treatment regimens in patients. The system analysis technique, embodied in the convolution integral, generated an impulse response function that, when convolved with temozolomide plasma concentration input functions, yielded predicted normal brain and brain tumor temozolomide concentration profiles for different temozolomide dosing regimens (75-200 mg/m(2)/d). Predicted peak concentrations of temozolomide ranged from 2.9 to 6.7 microg/mL in human glioma tumors and from 1.8 to 3.7 microg/mL in normal brain, with the total drug exposure, as indicated by the tissue/plasma area under the curve ratio, being about 1.3 in tumor compared with 0.9 in normal brain. The higher temozolomide exposures in brain tumor relative to normal brain were attributed to breakdown of the blood-brain barrier and possibly secondary to increased intratumoral angiogenesis. Overall, the method is considered a robust tool to analyze and predict tissue drug concentrations to help select the most rational dosing schedules.
A phase I trial was performed with combretastatin A4 phosphate (CA4P), a novel tubulin-binding agent that has been shown to rapidly reduce blood flow in animal tumors.
The drug was delivered by a ...10-minute weekly infusion for 3 weeks followed by a week gap, with intrapatient dose escalation. Dose escalation was accomplished by doubling until grade 2 toxicity was seen. The starting dose was 5 mg/m2.
Thirty-four patients received 167 infusions. CA4P was rapidly converted to the active combretastatin A4 (CA4), which was further metabolized to the glucuronide. CA4 area under the curve (AUC) increased from 0.169 at 5 mg/m2 to 3.29 micromol * h/L at 114 mg/m2. The mean CA4 AUC in eight patients at 68 mg/m2 was 2.33 micromol * h/L compared with 5.8 micromol * h/L at 25 mg/kg (the lowest effective dose) in the mouse. The only toxicity that possibly was related to the drug dose up to 40 mg/m2 was tumor pain. Dose-limiting toxicity was reversible ataxia at 114 mg/m2, vasovagal syncope and motor neuropathy at 88 mg/m2, and fatal ischemia in previously irradiated bowel at 52 mg/m2. Other drug-related grade 2 or higher toxicities seen in more than one patient were pain, lymphopenia, fatigue, anemia, diarrhea, hypertension, hypotension, vomiting, visual disturbance, and dyspnea. One patient at 68 mg/m2 had improvement in liver metastases of adrenocortical carcinoma.
CA4P was well tolerated in 14 of 16 patients at 52 or 68 mg/m2; these are doses at which tumor blood flow reduction has been recorded.
Stereotactic ablative radiotherapy (SABR) offers an alternative treatment for pancreatic cancer, with the potential for improved tumour control and reduced toxicity compared with conventional ...therapies. However, optimal dose planning and delivery strategies are unelucidated and gastro-intestinal (GI) toxicity remains a key concern.
Patients with inoperable non-metastatic pancreatic cancer who received CyberKnife® SABR (18-36 Gy) in three fractions as primary, adjuvant, consolidation or re-treatment options were studied. Patient individualised planning and delivery variables were collected and their impact on patient outcome examined. Linear-quadratic (LQ) radiobiology modelling methods were applied to assess SABR parameters against a conventional fractionated radiotherapy schedule.
In total 42 patients were included, 37 (88%) of whom had stage T4 disease. SABR was used > 6 months post-primary therapy to re-treat residual disease in 11 (26.2%) patients and relapsed disease in nine (21.4%) patients. SABR was an adjuvant to other primary therapy for 14 (33.3%) patients and was the sole primary therapy for eight (19.0%) patients. The mean (95% CI) planning target volume (PTV), prescription isodose, percentage cover, minimum dose to PTV and biological effective dose (BED) were 76.3(63.8-88.7) cc, 67.3(65.2-69.5)%, 96.6(95.5-97.7)%, 22.3(21.0-23.6) Gy and 50.3(47.7-53.0) Gy, respectively. Only 3/37 (8.1%) patients experienced Grade 3 acute toxicities. Two (4.8%) patients converted to resectable status and median freedom-from-local-progression (FFLP) and overall survival (OS) were 9.8 and 8.4 months, respectively. No late toxicity was experienced in 27/32 (84.4%) patients; however, four (12.5%) patients - of whom two had particularly large PTV, two had sub-optimal number of fiducials and three breached organ-at-risk (OAR) constraints-showed Grade 4 duodenal toxicities. Longer delivery time, extended treatment course and reduced percentage coverage additionally associated with late toxicity, likely reflecting parameters typically applied to riskier patients. Larger PTV size and longer treatment course associated with OS. Comparator regimen LQ modelling analysis indicated 50% of patients received minimum PTV doses less potent than a conventional radiotherapy regimen, indicating scope for dose escalation.
The results demonstrate the value of SABR for a range of indications in pancreatic cancer. Dose escalation to increase BED may improve FFLP and OS in inoperable, non-metastatic disease: however concomitant enhanced stringency for duodenal protection is critical, particularly for patients where SABR is more challenging.
Venous thromboembolism (VTE) is a relatively rare condition in childhood with treatment mainly based on extrapolation from studies in adults. Therefore, clinical trials of anticoagulation in children ...require novel approaches to deal with numerous challenges. The EINSTEIN-Jr program identified pediatric rivaroxaban regimens commencing with in vitro dose finding studies followed by evaluation of children of different ages through phase I and II studies using extensive modeling to determine bodyweight-related doses. Use of this approach resulted in drug exposure similar to that observed in young adults treated with rivaroxaban 20 mg once-daily.
EINSTEIN-Jr phase III is a randomized, open-label, study comparing the efficacy and safety of rivaroxaban 20 mg-equivalent dose regimens with those of standard anticoagulation for the treatment of any types of acute VTE in children aged 0-18 years.A total of approximately 500 children are expected to be included during the 4-year study window. Flexibility of treatment duration is allowed with study treatment to be given for 3 months with the option to continue treatment in 3-month increments, up to a total of 12 months. However, based on most common current practice, children younger than 2 years with catheter-related thrombosis will have a main treatment period of 1 month with the option to prolong treatment in 1-month increments, up to a total of 3 months.
EINSTEIN-Jr will compare previously established 20 mg-equivalent rivaroxaban dosing regimens with standard anticoagulation for the treatment of VTE in children. Demonstration of similarity of disease, as well as equivalent rivaroxaban exposure and exposure-response will enable extrapolation of efficacy from adult trials, which is critical given the challenges of enrollment in pediatric anticoagulation trials.
Clinicaltrials.gov NCT02234843, registered on 9 September 2014.
Three distinct septic systems designed for onsite removal of nitrogen (N) from residential wastewater were installed at the Massachusetts Alternative Septic System Test Center (MASSTC) and at homes ...across Suffolk County (SC), New York. All configurations featured nitrifying sand beds coupled with denitrifying biofilters composed of 1) a lined, saturated sand and woodchip layer, 2) a saturated box filled with woodchips, or 3) an unlined, unsaturated sand and woodchip layer. Total N (TN) in final effluent discharge from the three systems at MASSTC over more than two years were 7.1 ± 7.8, 4.3 ± 4.2, and 6.9 ± 8.4 mg N L−1, respectively representing TN reductions of 83%, 87%, and 84% from influent TN. Systems at MASSTC also removed on average 90.0–99.9% of 10 of 11 organic contaminants in pharmaceutical and personal care products, microbes indicative of pathogens, and biochemical oxygen demand. Over periods up to 16 months from start-up, effluent from three lined, one woodchip box, and three unlined systems in SC averaged 8.3 ± 9.2, 5.3 ± 3.7, and 8.7 ± 4.9 mg-TN L−1 representing removal rates of 90%, 94%, and 88%, respectively. For all systems, wastewater N was effectively nitrified year-round; N removal varied seasonally as denitrification attenuated in winter. Substantial quantities of TN were removed in the sand beds, likely due to denitrification in anoxic micro-zones. While elevated levels of carbon leached from the wood-based biofilters installed at MASSTC during the first 60 days of operation, no substantial decline in dissolved organic carbon or N removal was observed between the first 15 months of operation and the following 12 months. Collectively, the performance of these non-proprietary, passive systems suggest they may be a useful alternative septic system for protection of groundwater from elevated levels of N, organic contaminants, and pathogens.
Non-invasive imaging of angiogenesis could ease the optimization of antiangiogenesis treatments for cancer. In this study, we evaluated the role of VEGF-PET as a biomarker of dynamic angiogenic ...changes in tumors following treatment with the kinase inhibitor sunitinib. The effects of sunitinib treatment and withdrawal on the tumor was investigated using the new VEGF-PET tracer (89)Zr-ranibizumab as well as (18)F-FDG PET, and (15)O-water PET in mouse xenograft models of human cancer. The obtained imaging results were compared with tumor growth, VEGF plasma levels and immunohistologic analyzes. In contrast to (18)F-FDG and (15)O-water PET, VEGF-PET demonstrated dynamic changes during sunitinib treatment within the tumor with a strong decline in signal in the tumor center and only minimal reduction in tumor rim, with a pronounced rebound after sunitinib discontinuation. VEGF-PET results corresponded with tumor growth and immunohistochemical vascular- and tumor- markers. Our findings highlight the strengths of VEGF-PET imaging to allow serial analysis of angiogenic changes in different areas within a tumor.
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