Publications by authors named "Michael Casey"

85 Publications

Estimating cellular redundancy in networks of genetic expression.

Math Biosci 2021 Nov 22;341:108713. Epub 2021 Sep 22.

Mathematical Sciences, University of Southampton, UK; Institute of Life Sciences, University of Southampton, UK.

Networks of genetic expression can be modeled by hypergraphs with the additional structure that real coefficients are given to each vertex-edge incidence. The spectra, i.e. the multiset of the eigenvalues, of such hypergraphs, are known to encode structural information of the data. We show how these spectra can be used, in particular, in order to give an estimation of cellular redundancy, a novel measure of gene expression heterogeneity, of the network. We analyze some simulated and real data sets of gene expression for illustrating the new method proposed here.
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http://dx.doi.org/10.1016/j.mbs.2021.108713DOI Listing
November 2021

Musical components important for the Mozart K448 effect in epilepsy.

Sci Rep 2021 09 16;11(1):16490. Epub 2021 Sep 16.

Department of Neurology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.

There is growing evidence for the efficacy of music, specifically Mozart's Sonata for Two Pianos in D Major (K448), at reducing ictal and interictal epileptiform activity. Nonetheless, little is known about the mechanism underlying this beneficial "Mozart K448 effect" for persons with epilepsy. Here, we measured the influence that K448 had on intracranial interictal epileptiform discharges (IEDs) in sixteen subjects undergoing intracranial monitoring for refractory focal epilepsy. We found reduced IEDs during the original version of K448 after at least 30-s of exposure. Nonsignificant IED rate reductions were witnessed in all brain regions apart from the bilateral frontal cortices, where we observed increased frontal theta power during transitions from prolonged musical segments. All other presented musical stimuli were associated with nonsignificant IED alterations. These results suggest that the "Mozart K448 effect" is dependent on the duration of exposure and may preferentially modulate activity in frontal emotional networks, providing insight into the mechanism underlying this response. Our findings encourage the continued evaluation of Mozart's K448 as a noninvasive, non-pharmacological intervention for refractory epilepsy.
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http://dx.doi.org/10.1038/s41598-021-95922-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8446029PMC
September 2021

Endovascular Management of Distal Anterior Cerebral Artery Aneurysms: A Multicenter Retrospective Review.

World Neurosurg 2021 Oct 18;154:e421-e427. Epub 2021 Jul 18.

Department of Neurosurgery, Division of Neuroendovascular Surgery, Medical University of South Carolina, Charleston, South Carolina, USA.

Introduction: Distal anterior cerebral artery aneurysms (DACAA) are a rare and difficult entity to manage. Endovascular treatment has evolved for safe and durable treatment of these lesions. The objective of this study is to report the safety, efficacy, and outcomes of endovascular treatment of DACAA.

Methods: A retrospective review of DACAA endovascularly treated at 5 different institutions was performed. Data included demographics, rupture status, radiographic features, endovascular technique, complication rates, and long-term angiographic and clinical outcomes. A primary endpoint was a good clinical outcome (modified Rankin scale 0-2). Secondary endpoints included complications and radiographic occlusion at follow-up.

Results: A total of 84 patients were reviewed. The mean age was 56, and 64 (71.4%) were female. Fifty-two (61.9%) aneurysms were ruptured. A good functional outcome was achieved in 59 patients (85.5%). Sixty (71.4%) aneurysms were treated with primary coiling, and the remaining 24 were treated with flow diversion. Adequate occlusion was achieved in 41 (95.3%) aneurysms treated with coiling, and 17 (89.5%) with flow diversion. There were total 11 (13%) complications. In the flow diversion category, there were 2, both related to femoral access. In the coiling category, there were 9: 5 thromboembolic, 3 ruptures, and 1 related to femoral access.

Conclusion: Endovascular treatment, and in particular, flow diversion for DACAA, is safe, feasible, and associated with good long-term angiographic and clinical outcomes.
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http://dx.doi.org/10.1016/j.wneu.2021.07.055DOI Listing
October 2021

Hypertension and obesity in living kidney donors.

World J Transplant 2021 Jun;11(6):180-186

Department of Medicine, Division of Nephrology, Medical University of South Carolina, Charleston, SC 29425, United States.

Over the past few decades, the shortage in the kidney donor pool as compared to the increasing number of candidates on the kidney transplant waitlist led to loosening of kidney donors' acceptance criteria. Hypertension and obesity represent risk factors for chronic kidney disease, both in native kidneys and those in kidney transplant recipients. While great progress has been made in kidney transplantation from living donors to benefit the recipient survival and quality of life, progress has been slow to fully risk-characterize the donors. This review critically reassesses the current state of understanding regarding the risk of end-stage kidney disease in those donors with obesity, hypertension or both. Accurate risk assessment tools need to be developed urgently to fully understand the risk glomerular filtration rate compensation failure in the remaining kidney of the donors.
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http://dx.doi.org/10.5500/wjt.v11.i6.180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8218343PMC
June 2021

Association of High Burden of End-stage Kidney Disease With Decreased Kidney Transplant Rates With the Updated US Kidney Allocation Policy.

JAMA Surg 2021 Jul;156(7):639-645

Division of Transplant Surgery, Department of Surgery, Medical University of South Carolina, Charleston.

Importance: The Organ Procurement and Transplantation Network (OPTN) approved changes to the US kidney allocation system in 2019. The potential effects of this policy change using transplant rates normalized to end-stage kidney disease (ESKD) incidence have not been investigated.

Objective: To estimate how the OPTN kidney allocation policy will affect areas of the US currently demonstrating low rates of kidney transplant, when accounting for the regional burden of ESKD.

Design, Setting, And Participants: This cross-sectional population-based economic evaluation analyzed access of patients with ESKD to kidney transplant in the US. Participants included patients with incident ESKD, those on the kidney transplant wait list, and those who received a kidney transplant. Data were collected from January 1 to December 31, 2017, and were analyzed in 2019.

Main Outcomes And Measures: The probability of a patient with ESKD being placed on the transplant wait list or receiving a deceased donor kidney transplant. States and donor service areas (DSAs) were compared for gains and losses in rates of transplanted kidneys under the new allocation system. Transplant rates were normalized for ESKD burden.

Results: A total of 122 659 patients had incident ESKD in the US in 2017 (58.2% men; mean [SD] age, 62.8 [15.1] years). The probability of a patient with ESKD receiving a deceased donor kidney transplant varied 3-fold across the US (from 6.36% in West Virginia to 18.68% in the District of Columbia). Modeling of the OPTN demonstrates that DSAs from New York (124%), Georgia (65%), and Illinois (56%) are estimated to experience the largest increases in deceased donor kidney allocation. Other than Georgia, these states have kidney transplant rates per incident ESKD cases above the mean (of 50 states plus the District of Columbia, New York is 16th and Illinois is 24th). In contrast, DSAs from Nevada (-74%), Ohio (-67%), and North Carolina (-61%)-each of which has a transplant rate per incident ESKD cases significantly below the mean-are estimated to experience the largest decreases in deceased donor allocation (of 50 states plus the District of Columbia, North Carolina is 34th, Ohio is 38th, and Nevada is 47th).

Conclusions And Relevance: The new OPTN-approved kidney allocation policy may result in worsening geographic disparities in access to transplants when measured against the burden of ESKD within a particular region of the US.
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http://dx.doi.org/10.1001/jamasurg.2021.1489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8156168PMC
July 2021

40-Hz auditory stimulation for intracranial interictal activity: A pilot study.

Acta Neurol Scand 2021 Aug 24;144(2):192-201. Epub 2021 Apr 24.

Department of Neurology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA.

Objectives: To study the effects of auditory stimuli on interictal epileptiform discharge (IED) rates evident with intracranial monitoring.

Materials And Methods: Eight subjects undergoing intracranial EEG monitoring for refractory epilepsy participated in this study. Auditory stimuli consisted of a 40-Hz tone, a 440-Hz tone modulated by a 40-Hz sinusoid, Mozart's Sonata for Two Pianos in D Major (K448), and K448 modulated by a 40-Hz sinusoid (modK448). Subjects were stratified into high- and low-IED rate groups defined by baseline IED rates. Subject-level analyses identified individual responses to auditory stimuli, discerned specific brain regions with significant reductions in IED rates, and examined the influence auditory stimuli had on whole-brain sigma power (12-16 Hz).

Results: All subjects in the high baseline IED group had a significant 35.25% average reduction in IEDs during the 40-Hz tone; subject-level reductions localized to mesial and lateral temporal regions. Exposure to Mozart K448 showed significant yet less homogeneous responses. A post hoc analysis demonstrated two of the four subjects with positive IED responses had increased whole-brain power at the sigma frequency band during 40-Hz stimulation.

Conclusions: Our study is the first to evaluate the relationship between 40-Hz auditory stimulation and IED rates in refractory epilepsy. We reveal that 40-Hz auditory stimuli may be a noninvasive adjunctive intervention to reduce IED burden. Our pilot study supports the future examination of 40-Hz auditory stimuli in a larger population of subjects with high baseline IED rates.
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http://dx.doi.org/10.1111/ane.13437DOI Listing
August 2021

Genome Reduction Is Associated with Bacterial Pathogenicity across Different Scales of Temporal and Ecological Divergence.

Mol Biol Evol 2021 04;38(4):1570-1579

Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.

Emerging bacterial pathogens threaten global health and food security, and so it is important to ask whether these transitions to pathogenicity have any common features. We present a systematic study of the claim that pathogenicity is associated with genome reduction and gene loss. We compare broad-scale patterns across all bacteria, with detailed analyses of Streptococcus suis, an emerging zoonotic pathogen of pigs, which has undergone multiple transitions between disease and carriage forms. We find that pathogenicity is consistently associated with reduced genome size across three scales of divergence (between species within genera, and between and within genetic clusters of S. suis). Although genome reduction is also found in mutualist and commensal bacterial endosymbionts, genome reduction in pathogens cannot be solely attributed to the features of their ecology that they share with these species, that is, host restriction or intracellularity. Moreover, other typical correlates of genome reduction in endosymbionts (reduced metabolic capacity, reduced GC content, and the transient expansion of nonfunctional elements) are not consistently observed in pathogens. Together, our results indicate that genome reduction is a consistent correlate of pathogenicity in bacteria.
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http://dx.doi.org/10.1093/molbev/msaa323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8042751PMC
April 2021

US State Government Crisis Standards of Care Guidelines: Implications for Patients With Cancer.

JAMA Oncol 2021 02;7(2):199-205

Division of Population Sciences, Dana-Farber Cancer Institute, Boston, Massachusetts.

Importance: State crisis standards of care (CSC) guidelines in the US allocate scarce health care resources among patients. Anecdotal reports suggest that guidelines may disproportionately allocate resources away from patients with cancer, but no comprehensive evaluation has been performed.

Objective: To examine the implications of US state CSC guidelines for patients with cancer, including allocation methods, cancer-related categorical exclusions and deprioritizations, and provisions for blood products and palliative care.

Design, Setting, And Participants: This cross-sectional population-based analysis examined state-endorsed CSC guidelines published before May 20, 2020, that included health care resource allocation recommendations.

Main Outcomes And Measures: Guideline publication before or within 120 days after the first documented US case of coronavirus disease 2019 (COVID-19), inclusion of cancer-related categorical exclusions and/or deprioritizations, provisions for blood products and/or palliative care, and associations between these outcomes and state-based cancer demographics.

Results: Thirty-one states had health care resource allocation guidelines that met inclusion criteria, of which 17 had been published or updated since the first US case of COVID-19. States whose available hospital bed capacity was predicted to exceed 100% at 6 months (χ2 = 3.82; P = .05) or that had a National Cancer Institute-designated Comprehensive Cancer Center (CCC; χ2 = 6.21; P = .01) were more likely to have publicly available guidelines. The most frequent primary methods of prioritization were the Sequential Organ Failure Assessment score (27 states [87%]) and deprioritizing persons with worse long-term prognoses (22 states [71%]). Seventeen states' (55%) allocation methods included cancer-related deprioritizations, and 8 states (26%) included cancer-related categorical exclusions. The presence of an in-state CCC was associated with lower likelihood of cancer-related categorical exclusions (multivariable odds ratio, 0.06 [95% CI, 0.004-0.87]). Guidelines with disability rights statements were associated with specific provisions to allocate blood products (multivariable odds ratio, 7.44 [95% CI, 1.28-43.24). Both the presence of an in-state CCC and having an oncologist and/or palliative care specialist on the state CSC task force were associated with the inclusion of palliative care provisions.

Conclusions And Relevance: Among states with CSC guidelines, most deprioritized some patients with cancer during resource allocation, and one-fourth categorically excluded them. The presence of an in-state CCC was associated with guideline availability, palliative care provisions, and lower odds of cancer-related exclusions. These data suggest that equitable state-level CSC considerations for patients with cancer benefit from the input of oncology stakeholders.
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http://dx.doi.org/10.1001/jamaoncol.2020.6159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7716254PMC
February 2021

Benefit of Improved Performance with State-of-the Art Digital PET/CT for Lesion Detection in Oncology.

J Nucl Med 2020 11 20;61(11):1684-1690. Epub 2020 Mar 20.

Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania; and.

The latest digital whole-body PET scanners provide a combination of higher sensitivity and improved spatial and timing resolution. We performed a lesion detectability study on two generations of Biograph PET/CT scanners, the mCT Flow and the Vision, to study the impact of improved physical performance on clinical performance. Our hypothesis was that the improved performance of the Vision would result in improved lesion detectability, allowing shorter imaging times or, equivalently, a lower injected dose. Data were acquired with the Society of Nuclear Medicine and Molecular Imaging Clinical Trials Network torso phantom combined with a 20-cm-diameter cylindrical phantom. Spherical lesions were emulated by acquiring sphere-in-air data and combining them with the phantom data to generate combined datasets with embedded lesions of known contrast. Two sphere sizes and uptakes were used: 9.89-mm-diameter spheres with 6:1 (lung) and 3:1 (cylinder) local activity concentration uptakes and 4.95-mm-diameter spheres with 9.6:1 (lung) and 4.5:1 (cylinder) local activity concentration uptakes. Standard image reconstruction was performed: an ordinary Poisson ordered-subsets expectation maximization algorithm with point-spread function and time-of-flight modeling and postreconstruction smoothing with a 5-mm gaussian filter. The Vision images were also generated without any postreconstruction smoothing. Generalized scan statistics methodology was used to estimate the area under the localized receiver-operating-characteristic curve (ALROC). The higher sensitivity and improved time-of-flight performance of the Vision leads to reduced contrast in the background noise nodule distribution. Measured lesion contrast is also higher on the Vision because of its improved spatial resolution. Hence, the ALROC is noticeably higher for the Vision than for the mCT Flow. Improved overall performance of the Vision provides a factor of 4-6 reduction in imaging time (or injected dose) over the mCT Flow when using the ALROC metric for lesions at least 9.89 mm in diameter. Smaller lesions are barely detected in the mCT Flow, leading to even higher ALROC gains with the Vision. The improved spatial resolution of the Vision also leads to a higher measured contrast that is closer to the real uptake, implying improved quantification. Postreconstruction smoothing, however, reduces this improvement in measured contrast, thereby reducing the ALROC for small, high-uptake lesions.
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http://dx.doi.org/10.2967/jnumed.120.242305DOI Listing
November 2020

Costs and factors associated with heart failure following kidney transplantation - a single-center retrospective cohort study.

Transpl Int 2020 04 29;33(4):414-422. Epub 2020 Jan 29.

Department of Surgery, Medical University of South Carolina, Charleston, SC, USA.

The number of adults with heart failure (HF) will increase by ~50% between 2012 and 2030. Among kidney transplant recipients, HF accounts for 16% of all post-transplant admissions. We describe the burden of HF and predictors of healthcare utilization following kidney transplantation. We retrospectively identified adults who underwent kidney transplantation at our institution (01/2007-12/2017). Data were acquired from electronic health records, with healthcare utilization obtained from a statewide database. The HF incidence rate and prevalence were estimated for each year, total charges for HF and non-HF patients were compared, and logistic regression was employed for a 3-year predictive model of healthcare utilization associated with HF. Among 1731 kidney transplant recipients, the post-transplant HF incidence rate ranged from 1.91 (year 3) to 6.80 (year 10) per 100 person-years, while the prevalence increased from 31.7% (year 1) to 48.1% (year 10). Median charges were $75 837 (HF) compared to $42 940 (non-HF) per person-year (P < 0.001). Pretransplant HF [odds ratio (OR) = 3.12] and an eGFR < 45 (OR = 4.73) were the strongest predictors of HF encounters (P < 0.05 for both). We observed a high and increasing prevalence of HF, which was associated with twice the costs. Kidney transplant recipients would benefit from interventions aimed at mitigating HF risk factors.
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http://dx.doi.org/10.1111/tri.13571DOI Listing
April 2020

Theory of cell fate.

Wiley Interdiscip Rev Syst Biol Med 2020 03 12;12(2):e1471. Epub 2019 Dec 12.

Mathematical Sciences, University of Southampton, Southampton, UK.

Cell fate decisions are controlled by complex intracellular molecular regulatory networks. Studies increasingly reveal the scale of this complexity: not only do cell fate regulatory networks contain numerous positive and negative feedback loops, they also involve a range of different kinds of nonlinear protein-protein and protein-DNA interactions. This inherent complexity and nonlinearity makes cell fate decisions hard to understand using experiment and intuition alone. In this primer, we will outline how tools from mathematics can be used to understand cell fate dynamics. We will briefly introduce some notions from dynamical systems theory, and discuss how they offer a framework within which to build a rigorous understanding of what we mean by a cell "fate", and how cells change fate. We will also outline how modern experiments, particularly high-throughput single-cell experiments, are enabling us to test and explore the limits of these ideas, and build a better understanding of cellular identities. This article is categorized under: Models of Systems Properties and Processes > Mechanistic Models Biological Mechanisms > Cell Fates Models of Systems Properties and Processes > Cellular Models.
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http://dx.doi.org/10.1002/wsbm.1471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7027507PMC
March 2020

Assessing Feedback Response With a Wearable Electroencephalography System.

Front Hum Neurosci 2019 25;13:258. Epub 2019 Jul 25.

Thayer School of Engineering, Dartmouth College, Hanover, NH, United States.

Event related potential (ERP) components, such as P3, N2, and FRN, are potential metrics for assessing feedback response as a form of performance monitoring. Most research studies investigate these ERP components using clinical or research-grade electroencephalography (EEG) systems. Wearable EEGs, which are an affordable alternative, have the potential to assess feedback response using ERPs but have not been sufficiently evaluated. Feedback-related ERPs also have not been scientifically evaluated in interactive settings that are similar to daily computer use. In this study, a consumer-grade wearable EEG system was assessed for its feasibility to collect feedback-related ERPs through an interactive software module that provided an environment in which users were permitted to navigate freely within the program to make decisions. The recording hardware, which costs < $1,500 in total, incorporated the OpenBCI Cyton Board with Daisy chain, a consumer-grade EEG system that costs $949 USD. Seventeen participants interacted with an oddball paradigm and an interactive module designed to elicit feedback-related ERPs. The features of interests for the oddball paradigm were the P3 and N2 components. The features of interests for the interactive module were the P3, N2, and FRN components elicited in response to positive, neutral, and two types of negative feedback. The FRN was calculated by subtracting the positive feedback response from the negative feedback responses. The P3 and N2 components of the oddball paradigm indicated statistically significant differences between infrequent targets and frequent targets which is in line with current literature. The P3 and N2 components elicited in the interactive module indicated statistically significant differences between positive, neutral, and negative feedback responses. There were no significant differences between the FRN types and significant interactions with channel group and FRN type. The OpenBCI Cyton, after some modifications, shows potential for eliciting and assessing P3, N2, and FRN components, which are important indicators for performance monitoring, in an interactive setting.
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http://dx.doi.org/10.3389/fnhum.2019.00258DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6669939PMC
July 2019

Data-driven voluntary body motion detection and non-rigid event-by-event correction for static and dynamic PET.

Phys Med Biol 2019 03 8;64(6):065002. Epub 2019 Mar 8.

Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States of America. Author to whom any correspondence should be addressed.

PET has the potential to perform absolute in vivo radiotracer quantitation. This potential can be compromised by voluntary body motion (BM), which degrades image resolution, alters apparent tracer uptakes, introduces CT-based attenuation correction mismatch artifacts and causes inaccurate parameter estimates in dynamic studies. Existing body motion correction (BMC) methods include frame-based image-registration (FIR) approaches and real-time motion tracking using external measurement devices. FIR does not correct for motion occurring within a pre-defined frame and the device-based method is generally not practical in routine clinical use, since it requires attaching a tracking device to the patient and additional device set up time. In this paper, we proposed a data-driven algorithm, centroid of distribution (COD), to detect BM. In this algorithm, the central coordinate of the time-of-flight (TOF) bin, which can be used as a reasonable surrogate for the annihilation point, is calculated for every event, and averaged over a certain time interval to generate a COD trace. We hypothesized that abrupt changes on the COD trace in lateral direction represent BMs. After detection, BM is estimated using non-rigid image registrations and corrected through list-mode reconstruction. The COD-based BMC approach was validated using a monkey study and was evaluated against FIR using four human and one dog studies with multiple tracers. The proposed approach successfully detected BMs and yielded superior correction results over conventional FIR approaches.
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http://dx.doi.org/10.1088/1361-6560/ab02c2DOI Listing
March 2019

Dynamic whole-body PET imaging: principles, potentials and applications.

Eur J Nucl Med Mol Imaging 2019 02 29;46(2):501-518. Epub 2018 Sep 29.

Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.

Purpose: In this article, we discuss dynamic whole-body (DWB) positron emission tomography (PET) as an imaging tool with significant clinical potential, in relation to conventional standard uptake value (SUV) imaging.

Background: DWB PET involves dynamic data acquisition over an extended axial range, capturing tracer kinetic information that is not available with conventional static acquisition protocols. The method can be performed within reasonable clinical imaging times, and enables generation of multiple types of PET images with complementary information in a single imaging session. Importantly, DWB PET can be used to produce multi-parametric images of (i) Patlak slope (influx rate) and (ii) intercept (referred to sometimes as "distribution volume"), while also providing (iii) a conventional 'SUV-equivalent' image for certain protocols.

Results: We provide an overview of ongoing efforts (primarily focused on FDG PET) and discuss potential clinically relevant applications.

Conclusion: Overall, the framework of DWB imaging [applicable to both PET/CT(computed tomography) and PET/MRI (magnetic resonance imaging)] generates quantitative measures that may add significant value to conventional SUV image-derived measures, with limited pitfalls as we also discuss in this work.
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http://dx.doi.org/10.1007/s00259-018-4153-6DOI Listing
February 2019

Improved discrimination between benign and malignant LDCT screening-detected lung nodules with dynamic over static F-FDG PET as a function of injected dose.

Phys Med Biol 2018 09 6;63(17):175015. Epub 2018 Sep 6.

Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States of America. Department of Engineering Physics, Tsinghua University, Beijing, People's Republic of China. Key Laboratory of Particle & Radiation Imaging, Ministry of Education, Tsinghua University, Beijing, People's Republic of China.

Lung cancer mortality rate can be significantly reduced by up to 20% through routine low-dose computed tomography (LDCT) screening, which, however, has high sensitivity but low specificity, resulting in a high rate of false-positive nodules. Combining PET with CT may provide more accurate diagnosis for indeterminate screening-detected nodules. In this work, we investigated low-dose dynamic F-FDG PET in discrimination between benign and malignant nodules using a virtual clinical trial based on patient study with ground truth. Six patients with initial LDCT screening-detected lung nodules received 90 min single-bed PET scans following a 10 mCi FDG injection. Low-dose static and dynamic images were generated from under-sampled list-mode data at various count levels (100%, 50%, 10%, 5%, and 1%). A virtual clinical trial was performed by adding nodule population variability, measurement noise, and static PET acquisition start time variability to the time activity curves (TACs) of the patient data. We used receiver operating characteristic (ROC) analysis to estimate the classification capability of standardized uptake value (SUV) and net uptake constant K from their simulated benign and malignant distributions. Various scan durations and start times (t ) were investigated in dynamic Patlak analysis to optimize simplified acquisition protocols with a population-based input function (PBIF). The area under curve (AUC) of ROC analysis was higher with increased scan duration and earlier t . Highly similar results were obtained using PBIF to those using image-derived input function (IDIF). The AUC value for K using optimized t and scan duration with 10% dose was higher than that for SUV with 100% dose. Our results suggest that dynamic PET with as little as 1 mCi FDG could provide discrimination between benign and malignant lung nodules with higher than 90% sensitivity and specificity for patients similar to the pilot and simulated population in this study, with LDCT screening-detected indeterminate lung nodules.
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http://dx.doi.org/10.1088/1361-6560/aad97fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6158045PMC
September 2018

The effect of time-of-flight and point spread function modeling on Rb myocardial perfusion imaging of obese patients.

J Nucl Cardiol 2018 10 15;25(5):1521-1545. Epub 2018 Jun 15.

Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, 22 South Greene St., Baltimore, MD, 21201, USA.

Background: The effect of time-of-flight (TOF) and point spread function (PSF) modeling in image reconstruction has not been well studied for cardiac PET. This study assesses their separate and combined influence on Rb myocardial perfusion imaging in obese patients.

Methods: Thirty-six obese patients underwent rest-stress Rb cardiac PET. Images were reconstructed with and without TOF and PSF modeling. Perfusion was quantitatively compared using the AHA 17-segment model for patients grouped by BMI, cross-sectional body area in the scanner field of view, gender, and left ventricular myocardial volume. Summed rest scores (SRS), summed stress scores (SSS), and summed difference scores (SDS) were compared.

Results: TOF improved polar map visual uniformity and increased septal wall perfusion by up to 10%. This increase was greater for larger patients, more evident for patients grouped by cross-sectional area than by BMI, and more prominent for females. PSF modeling increased perfusion by about 1.5% in all cardiac segments. TOF modeling generally decreased SRS and SSS with significant decreases between 2.4 and 3.0 (P < .05), which could affect risk stratification; SDS remained about the same. With PSF modeling, SRS, SSS, and SDS were largely unchanged.

Conclusion: TOF and PSF modeling affect regional and global perfusion, SRS, and SSS. Clinicians should consider these effects and gender-dependent differences when interpreting Rb perfusion studies.
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http://dx.doi.org/10.1007/s12350-018-1311-yDOI Listing
October 2018

Respiratory Motion Compensation for PET/CT with Motion Information Derived from Matched Attenuation-Corrected Gated PET Data.

J Nucl Med 2018 09 9;59(9):1480-1486. Epub 2018 Feb 9.

Department of Radiology and Biomedical Imaging, Yale University, New Haven, Connecticut.

Respiratory motion degrades the detection and quantification capabilities of PET/CT imaging. Moreover, mismatch between a fast helical CT image and a time-averaged PET image due to respiratory motion results in additional attenuation correction artifacts and inaccurate localization. Current motion compensation approaches typically have 3 limitations: the mismatch among respiration-gated PET images and the CT attenuation correction (CTAC) map can introduce artifacts in the gated PET reconstructions that can subsequently affect the accuracy of the motion estimation; sinogram-based correction approaches do not correct for intragate motion due to intracycle and intercycle breathing variations; and the mismatch between the PET motion compensation reference gate and the CT image can cause an additional CT-mismatch artifact. In this study, we established a motion correction framework to address these limitations. In the proposed framework, the combined emission-transmission reconstruction algorithm was used for phase-matched gated PET reconstructions to facilitate the motion model building. An event-by-event nonrigid respiratory motion compensation method with correlations between internal organ motion and external respiratory signals was used to correct both intracycle and intercycle breathing variations. The PET reference gate was automatically determined by a newly proposed CT-matching algorithm. We applied the new framework to 13 human datasets with 3 different radiotracers and 323 lesions and compared its performance with CTAC and non-attenuation correction (NAC) approaches. Validation using 4-dimensional CT was performed for one lung cancer dataset. For the 10 F-FDG studies, the proposed method outperformed ( < 0.006) both the CTAC and the NAC methods in terms of region-of-interest-based SUV, SUV, and SUV ratio improvements over no motion correction (SUV: 19.9% vs. 14.0% vs. 13.2%; SUV: 15.5% vs. 10.8% vs. 10.6%; SUV ratio: 24.1% vs. 17.6% vs. 16.2%, for the proposed, CTAC, and NAC methods, respectively). The proposed method increased SUV ratios over no motion correction for 94.4% of lesions, compared with 84.8% and 86.4% using the CTAC and NAC methods, respectively. For the 2 F-fluoropropyl-(+)-dihydrotetrabenazine studies, the proposed method reduced the CT-mismatch artifacts in the lower lung where the CTAC approach failed and maintained the quantification accuracy of bone marrow where the NAC approach failed. For the F-FMISO study, the proposed method outperformed both the CTAC and the NAC methods in terms of motion estimation accuracy at 2 lung lesion locations. The proposed PET/CT respiratory event-by-event motion-correction framework with motion information derived from matched attenuation-corrected PET data provides image quality superior to that of the CTAC and NAC methods for multiple tracers.
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http://dx.doi.org/10.2967/jnumed.117.203000DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6126443PMC
September 2018

Development and Evaluation of mini-EXPLORER: A Long Axial Field-of-View PET Scanner for Nonhuman Primate Imaging.

J Nucl Med 2018 06 1;59(6):993-998. Epub 2018 Feb 1.

Department of Biomedical Engineering, University of California-Davis, Davis, California.

We describe a long axial field-of-view (FOV) PET scanner for high-sensitivity and total-body imaging of nonhuman primates and present the physical performance and first phantom and animal imaging results. The mini-EXPLORER PET scanner was built using the components of a clinical scanner reconfigured with a detector ring diameter of 43.5 cm and an axial length of 45.7 cm. National Electrical Manufacturers Association (NEMA) NU-2 and NU-4 phantoms were used to measure sensitivity and count rate performance. Reconstructed spatial resolution was investigated by imaging a radially stepped point source and a Derenzo phantom. The effect of the wide acceptance angle was investigated by comparing performance with maximum acceptance angles of 14°-46°. Lastly, an initial assessment of the in vivo performance of the mini-EXPLORER was undertaken with a dynamic F-FDG nonhuman primate (rhesus monkey) imaging study. The NU-2 total sensitivity was 5.0%, and the peak noise-equivalent count rate measured with the NU-4 monkey scatter phantom was 1,741 kcps, both obtained using the maximum acceptance angle (46°). The NU-4 scatter fraction was 16.5%, less than 1% higher than with a 14° acceptance angle. The reconstructed spatial resolution was approximately 3.0 mm at the center of the FOV, with a minor loss in axial spatial resolution (0.5 mm) when the acceptance angle increased from 14° to 46°. The rhesus monkey F-FDG study demonstrated the benefit of the high sensitivity of the mini-EXPLORER, including fast imaging (1-s early frames), excellent image quality (30-s and 5-min frames), and late-time-point imaging (18 h after injection), all obtained at a single bed position that captured the major organs of the rhesus monkey. This study demonstrated the physical performance and imaging capabilities of a long axial FOV PET scanner designed for high-sensitivity imaging of nonhuman primates. Further, the results of this study suggest that a wide acceptance angle can be used with a long axial FOV scanner to maximize sensitivity while introducing only minor trade-offs such as a small increase in scatter fraction and slightly degraded axial spatial resolution.
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http://dx.doi.org/10.2967/jnumed.117.200519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004556PMC
June 2018

Analysis of Risk Factors for Kidney Retransplant Outcomes Associated with Common Induction Regimens: A Study of over Twelve-Thousand Cases in the United States.

J Transplant 2017 24;2017:8132672. Epub 2017 Sep 24.

Department of Medicine, Division of Nephrology, Hypertension and Renal Transplantation, University of Florida, Gainesville, FL, USA.

We studied registry data of 12,944 adult kidney retransplant recipients categorized by induction regimen received into antithymocyte globulin (ATG) ( = 9120), alemtuzumab ( = 1687), and basiliximab ( = 2137) cohorts. We analyzed risk factors for 1-year acute rejection (AR) and 5-year death-censored graft loss (DCGL) and patient death. Compared with the reference, basiliximab: (1) one-year AR risk was lower with ATG in retransplant recipients of expanded criteria deceased-donor kidneys (HR = 0.56, 95% CI = 0.35-0.91 and HR = 0.54, 95% CI = 0.27-1.08, resp.), while AR risk was lower with alemtuzumab in retransplant recipients with >3 HLA mismatches before transplant (HR = 0.63, 95% CI = 0.44-0.93 and HR = 0.81, 95% CI = 0.63-1.06, resp.); (2) five-year DCGL risk was lower with alemtuzumab, not ATG, in retransplant recipients of African American race (HR = 0.54, 95% CI = 0.34-0.86 and HR = 0.73, 95% CI = 0.51-1.04, resp.) or with pretransplant glomerulonephritis (HR = 0.65, 95% CI = 0.43-0.98 and HR = 0.82, 95% CI = 0.60-1.12, resp.). Therefore, specific risk factor-induction regimen combinations may predict outcomes and this information may help in individualizing induction in retransplant recipients.
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http://dx.doi.org/10.1155/2017/8132672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632904PMC
September 2017

New-onset diabetes after kidney transplantation: can the risk be modified by choosing immunosuppression regimen based on pretransplant viral serology?

Nephrol Dial Transplant 2018 01;33(1):177-184

Department of Pharmacy Practice, College of Pharmacy, University of Rhode Island, Kingston, RI, USA.

Background: This study aimed to analyze adult kidney transplant recipients (KTRs) for the risk of new-onset diabetes after transplantation (NODAT) associated with viral serologies and immunosuppression regimens [tacrolimus (Tac) + mycophenolate (MPA), cyclosporine (CSA) + MPA, sirolimus (SRL) + MPA, SRL + CSA or SRL +Tac].

Methods: Cox regression models were used to examine the risk of NODAT in the first posttransplant year associated with: (i) CSA + MPA, SRL + MPA, SRL + MPA or SRL + Tac versus reference, Tac + MPA; (ii) pretransplant viral serology [+ or -; hepatitis B core (HBc), hepatitis C (HCV), cytomegalovirus (CMV) or Epstein Barr Virus (EBV)]; and (iii) interactions between immunosuppression regimens and the viral serology found significant in the main analysis.

Results: Adult KTRs (n = 97 644) from January 1995 through September 2015 were studied. HCV+ [hazard ratio (HR) 1.50, 95% confidence interval (CI) 1.31-1.68] or CMV+ (HR 1.12, 95% CI 1.06-1.19) serology was a risk factor and HBc+ (HR 1.04, 95% CI 0.95-1.15) or EBV+ (HR 1.06, 95% CI 0.97-1.15) serology was not a risk factor for NODAT. Regardless of associated HCV or CMV serology, risk of NODAT relative to the reference regimen (Tac + MPA) was lower with CSA + MPA [HCV-: HR 0.74, 95% CI 0.65-0.85; HCV+: HR 0.47, 95% CI 0.28-0.78; CMV-: CSA + MPA HR 0.68, 95% CI 0.54-0.86; CMV+: (CSA + MPA) HR 0.73, 95% CI 0.63-0.85] and similar with SRL + CSA or SRL + MPA. In KTRs with HCV- or CMV+ serology, SRL + Tac was associated with a higher risk of NODAT relative to reference [HCV- (HR 1.43, 95% CI 1.17-1.74) and CMV+ (HR 1.44, 95% CI 1.14-1.81), respectively]. The risk for NODAT-free graft loss was lower with Tac + MPA than the other regimens.

Conclusions: Tailoring immunosuppression regimen based on HCV or CMV serology may modify the risk of developing NODAT in KTRs.
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http://dx.doi.org/10.1093/ndt/gfx281DOI Listing
January 2018

Development of Halo Nevi in a Lung Cancer Patient: A Novel Immune-Related Cutaneous Event from Atezolizumab.

J Drugs Dermatol 2017 Oct;16(10):1047-1049

Immunotherapy-induced vitiligo is an immune-related adverse event (irAE) observed in metastatic melanoma patients treated with immune checkpoint inhibitors that target the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death-1 (PD-1) pathways. To date, the development of leukoderma, poliosis, and halo nevi during immunotherapy has largely been reported in metastatic melanoma patients. We report a case of immunotherapy-induced leukoderma presenting as halo nevi in a patient with non-small cell lung cancer (NSCLC) treated with atezolizumab, a programmed cell death ligand (PD-L1) antibody. Immunotherapy-induced vitiligo in metastatic melanoma patients may be associated with improved survival, but it remains to be determined whether its occurrence in non-melanoma cancers has the same prognostic significance.

J Drugs Dermatol. 2017;16(10):1047-1049.

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October 2017

Experiences with online consultation systems in primary care: case study of one early adopter site.

Br J Gen Pract 2017 Nov 9;67(664):e736-e743. Epub 2017 Oct 9.

Centre for Primary Care and Public Health, Blizard Institute, Queen Mary University of London, London.

Background: There is a strong policy drive towards implementing alternatives to face-to-face consultations in general practice to improve access, efficiency, and cost-effectiveness. These alternatives embrace novel technologies that are assumed to offer potential to improve care.

Aim: To explore the introduction of one online consultation system (Tele-Doc) and how it shapes working practices.

Design And Setting: Mixed methods case study in an inner-city general practice.

Method: The study was conducted through interviews with IT developers, clinicians, and administrative staff, and scrutiny of documents, websites, and demonstrator versions of Tele-Doc, followed by thematic analysis and discourse analysis.

Results: Three interrelated themes were identified: online consultation systems as innovation, managing the 'messiness' of general practice consultations, and redistribution of the work of general practice. These themes raise timely questions about what it means to consult in contemporary general practice. Uptake of Tele-Doc by patients was low. Much of the work of the consultation was redistributed to patients and administrators, sometimes causing misunderstandings. The 'messiness' of consultations was hard to eliminate. In-house training focused on the technical application rather than associated transformations to practice work that were not anticipated. GPs welcomed varied modes of consulting, but the aspiration of improved efficiency was not realised in practice.

Conclusion: Tele-Doc offers a new kind of consultation that is still being worked out in practice. It may offer convenience for patients with discrete, single problems, and a welcome variation to GPs' workload. Tele-Doc's potential for addressing more complex problems and achieving efficiency is less clear, and its adoption may involve unforeseeable consequences.
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http://dx.doi.org/10.3399/bjgp17X693137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5647916PMC
November 2017

Music of the 7Ts: Predicting and Decoding Multivoxel fMRI Responses with Acoustic, Schematic, and Categorical Music Features.

Authors:
Michael A Casey

Front Psychol 2017 14;8:1179. Epub 2017 Jul 14.

Bregman Music and Audio Lab, Computer Science and Music Departments, Dartmouth CollegeHanover, NH, United States.

Underlying the experience of listening to music are parallel streams of auditory, categorical, and schematic qualia, whose representations and cortical organization remain largely unresolved. We collected high-field (7T) fMRI data in a music listening task, and analyzed the data using multivariate decoding and stimulus-encoding models. Twenty subjects participated in the experiment, which measured BOLD responses evoked by naturalistic listening to twenty-five music clips from five genres. Our first analysis applied machine classification to the multivoxel patterns that were evoked in temporal cortex. Results yielded above-chance levels for both stimulus identification and genre classification-cross-validated by holding out data from multiple of the stimuli during model training and then testing decoding performance on the held-out data. Genre model misclassifications were significantly correlated with those in a corresponding behavioral music categorization task, supporting the hypothesis that geometric properties of multivoxel pattern spaces underlie observed musical behavior. A second analysis employed a spherical searchlight regression analysis which predicted multivoxel pattern responses to music features representing melody and harmony across a large area of cortex. The resulting prediction-accuracy maps yielded significant clusters in the temporal, frontal, parietal, and occipital lobes, as well as in the parahippocampal gyrus and the cerebellum. These maps provide evidence in support of our hypothesis that geometric properties of music cognition are neurally encoded as multivoxel representational spaces. The maps also reveal a cortical topography that differentially encodes categorical and absolute-pitch information in distributed and overlapping networks, with smaller specialized regions that encode tonal music information in relative-pitch representations.
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http://dx.doi.org/10.3389/fpsyg.2017.01179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5509941PMC
July 2017

Plane-dependent ML scatter scaling: 3D extension of the 2D simulated single scatter (SSS) estimate.

Phys Med Biol 2017 Jul 24;62(16):6515-6531. Epub 2017 Jul 24.

Nuclear Medicine, KU Leuven, B-3000 Leuven, Belgium.

Scatter correction is typically done using a simulation of the single scatter, which is then scaled to account for multiple scatters and other possible model mismatches. This scaling factor is determined by fitting the simulated scatter sinogram to the measured sinogram, using only counts measured along LORs that do not intersect the patient body, i.e. 'scatter-tails'. Extending previous work, we propose to scale the scatter with a plane dependent factor, which is determined as an additional unknown in the maximum likelihood (ML) reconstructions, using counts in the entire sinogram rather than only the 'scatter-tails'. The ML-scaled scatter estimates are validated using a Monte-Carlo simulation of a NEMA-like phantom, a phantom scan with typical contrast ratios of a Ga-PSMA scan, and 23 whole-body F-FDG patient scans. On average, we observe a 12.2% change in the total amount of tracer activity of the MLEM reconstructions of our whole-body patient database when the proposed ML scatter scales are used. Furthermore, reconstructions using the ML-scaled scatter estimates are found to eliminate the typical 'halo' artifacts that are often observed in the vicinity of high focal uptake regions.
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http://dx.doi.org/10.1088/1361-6560/aa7a8cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5748468PMC
July 2017

Expanding the endoscopic transpterygoid corridor to the petroclival region: anatomical study and volumetric comparative analysis.

J Neurosurg 2018 06 21;128(6):1855-1864. Epub 2017 Jul 21.

Departments of1Neurosurgery and.

OBJECTIVE The endoscopic endonasal transmaxillary transpterygoid (TMTP) approach has been the gateway for lateral skull base exposure. Removal of the cartilaginous eustachian tube (ET) and lateral mobilization of the internal carotid artery (ICA) are technically demanding adjunctive steps that are used to access the petroclival region. The gained expansion of the deep working corridor provided by these maneuvers has yet to be quantified. METHODS The TMTP approach with cartilaginous ET removal and ICA mobilization was performed in 5 adult cadaveric heads (10 sides). Accessible portions of the petrous apex were drilled during the following 3 stages: 1) before ET removal, 2) after ET removal but before ICA mobilization, and 3) after ET removal and ICA repositioning. Resection volumes were calculated using 3D reconstructions generated from thin-slice CT scans obtained before and after each step of the dissection. RESULTS The average petrous temporal bone resection volumes at each stage were 0.21 cm, 0.71 cm, and 1.32 cm (p < 0.05, paired t-test). Without ET removal, inferior and superior access to the petrous apex was limited. Furthermore, without ICA mobilization, drilling was confined to the inferior two-thirds of the petrous apex. After mobilization, the resection was extended superiorly through the upper extent of the petrous apex. CONCLUSIONS The transpterygoid corridor to the petroclival region is maximally expanded by the resection of the cartilaginous ET and mobilization of the paraclival ICA. These added maneuvers expanded the deep window almost 6 times and provided more lateral access to the petroclival region with a maximum volume of 1.5 cm. This may result in the ability to resect small-to-moderate sized intradural petroclival lesions up to that volume. Larger lesions may better be approached through an open transcranial approach.
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http://dx.doi.org/10.3171/2017.1.JNS161788DOI Listing
June 2018

Babesiosis: An unusual cause of sepsis after kidney transplantation and review of the literature.

Transpl Infect Dis 2017 Oct 28;19(5). Epub 2017 Jul 28.

Division of Nephrology, Hypertension, and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, FL, USA.

We report a unique case of babesiosis presenting as sepsis after kidney transplantation. A 70-year-old female kidney transplant recipient presented with fever, hemolytic anemia, and acute kidney injury, and met three of four systemic inflammatory response syndrome criteria. Serology was positive for Babesia microti, confirmed by polymerase chain reaction. The patient was treated with atovaquone and azithromycin and made a full recovery. Reports of babesiosis after solid organ transplantation are rare, with only four prior cases reported in the literature. We report the first case of babesiosis, to our knowledge, presenting as sepsis that was successfully treated after solid organ transplantation.
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http://dx.doi.org/10.1111/tid.12740DOI Listing
October 2017

Third Ventricular Cerebrospinal Fluid Cysts of Thalamic Origin: Review of Embryologic Origin, Presentation, and Management Strategies with a Case Series.

World Neurosurg 2017 Jul 6;103:210-219. Epub 2017 Apr 6.

Department of Neurosurgery, University of Colorado, Denver, Colorado, USA. Electronic address:

Objective: Third ventricular cerebrospinal fluid (CSF) cysts of thalamic origin are rare. The objective of this study is to review their possible pathogenesis, clinical presentation, and management strategies with a case series describing management via an endoscopic approach with fenestration using a single burr-hole technique.

Methods: A systematic literature review of reported cases of thalamic cysts was conducted with further meta-analysis of CSF cysts that involve the third ventricle. The mode of presentation, pathologic analysis, surgical management, and outcomes were analyzed.

Results: Twenty-two studies reported between 1990 and 2013 described 42 cases of thalamic cyst. Of those cases, 13 were consistent with CSF cyst that originated in the thalamus and involved the third ventricle. Eight cases (61.5%) were treated via endoscopic fenestration, 2 cases (15.4%) were surgically drained, 2 cases (15.4%) were stereotactically aspirated, and 1 case (7.69%) was observed. The most common presenting symptoms were gait disturbance (26.3%) and headaches (26.3%) followed by tremors (15.8%) and weakness (15.8%). In our series, a single burr-hole technique was a successful definitive treatment, with an average period of 23 months.

Conclusions: Third ventricular CSF cysts of thalamic origin most commonly present with hydrocephalus. They can be safely definitively treated via endoscopic fenestration to the CSF circulation using a single burr-hole technique. Long-term follow-up shows lasting improvement in symptoms without reaccumulation of the cyst.
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http://dx.doi.org/10.1016/j.wneu.2017.03.138DOI Listing
July 2017

Generalized PSF modeling for optimized quantitation in PET imaging.

Phys Med Biol 2017 Jun 24;62(12):5149-5179. Epub 2017 Mar 24.

Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, United States of America. Department of Radiology and Radiological Sciences, School of Medicine, Johns Hopkins University, Baltimore, MD, United States of America.

Point-spread function (PSF) modeling offers the ability to account for resolution degrading phenomena within the PET image generation framework. PSF modeling improves resolution and enhances contrast, but at the same time significantly alters image noise properties and induces edge overshoot effect. Thus, studying the effect of PSF modeling on quantitation task performance can be very important. Frameworks explored in the past involved a dichotomy of PSF versus no-PSF modeling. By contrast, the present work focuses on quantitative performance evaluation of standard uptake value (SUV) PET images, while incorporating a wide spectrum of PSF models, including those that under- and over-estimate the true PSF, for the potential of enhanced quantitation of SUVs. The developed framework first analytically models the true PSF, considering a range of resolution degradation phenomena (including photon non-collinearity, inter-crystal penetration and scattering) as present in data acquisitions with modern commercial PET systems. In the context of oncologic liver FDG PET imaging, we generated 200 noisy datasets per image-set (with clinically realistic noise levels) using an XCAT anthropomorphic phantom with liver tumours of varying sizes. These were subsequently reconstructed using the OS-EM algorithm with varying PSF modelled kernels. We focused on quantitation of both SUV and SUV, including assessment of contrast recovery coefficients, as well as noise-bias characteristics (including both image roughness and coefficient of-variability), for different tumours/iterations/PSF kernels. It was observed that overestimated PSF yielded more accurate contrast recovery for a range of tumours, and typically improved quantitative performance. For a clinically reasonable number of iterations, edge enhancement due to PSF modeling (especially due to over-estimated PSF) was in fact seen to lower SUV bias in small tumours. Overall, the results indicate that exactly matched PSF modeling does not offer optimized PET quantitation, and that PSF overestimation may provide enhanced SUV quantitation. Furthermore, generalized PSF modeling may provide a valuable approach for quantitative tasks such as treatment-response assessment and prognostication.
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http://dx.doi.org/10.1088/1361-6560/aa6911DOI Listing
June 2017
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