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1.
Am J Crit Care ; 30(2): 113-120, 2021 03 01.
Article in English | MEDLINE | ID: mdl-33644798

ABSTRACT

BACKGROUND: As the role of a health care system's influence on nurse burnout becomes better understood, an under-standing of the impact of a nurses' work environment on burnout and well-being is also imperative. OBJECTIVE: To identify the key elements of a healthy work environment associated with burnout, secondary trauma, and compassion satisfaction, as well as the effect of burnout and the work environment on nurse turnover. METHODS: A total of 779 nurses in 24 critical care units at 13 hospitals completed a survey measuring burnout and quality of the work environment. Actual unit-level data for nurse turnover during a 5-month period were queried and compared with the survey results. RESULTS: Among nurses in the sample, 61% experience moderate burnout. In models controlling for key nurse characteristics including age, level of education, and professional recognition, 3 key elements of the work environment emerged as significant predictors of burnout: staffing, meaningful recognition, and effective decision-making. The latter 2 elements also predicted more compassion satisfaction among critical care nurses. In line with previous research, these findings affirm that younger age is associated with more burnout and less compassion satisfaction. CONCLUSIONS: Efforts are recommended on these 3 elements of the work environment (staffing, meaningful recognition, effective decision-making) as part of a holistic, systems-based approach to addressing burnout and well-being. Such efforts, in addition to supporting personal resilience-building activities, should be undertaken especially with younger members of the workforce in order to begin to address the crisis of burnout in health care.


Subject(s)
Burnout, Professional , Compassion Fatigue , Job Satisfaction , Nursing Staff, Hospital , Critical Care , Cross-Sectional Studies , Empathy , Humans , Surveys and Questionnaires
2.
J Nucl Cardiol ; 28(2): 624-637, 2021 04.
Article in English | MEDLINE | ID: mdl-31077073

ABSTRACT

BACKGROUND: In the ongoing efforts to reduce cardiac perfusion dose (injected radioactivity) for conventional SPECT/CT systems, we performed a human observer study to confirm our clinical model observer findings that iterative reconstruction employing OSEM (ordered-subset expectation-maximization) at 25% of the full dose (quarter-dose) has a similar performance for detection of hybrid cardiac perfusion defects as FBP at full dose. METHODS: One hundred and sixty-six patients, who underwent routine rest-stress Tc-99m sestamibi cardiac perfusion SPECT/CT imaging and clinically read as normally perfused, were included in the study. Ground truth was established by the normal read and the insertion of hybrid defects. In addition to the reconstruction of the 25% of full-dose data using OSEM with attenuation (AC), scatter (SC), and spatial resolution correction (RC), FBP and OSEM (with AC, SC, and RC) both at full dose (100%) were done. Both human observer and clinical model observer confidence scores were obtained to generate receiver operating characteristics (ROC) curves in a task-based image quality assessment. RESULTS: Average human observer AUC (area under the ROC curve) values of 0.725, 0.876, and 0.890 were obtained for FBP at full dose, OSEM at 25% of full dose, and OSEM at full dose, respectively. Both OSEM strategies were significantly better than FBP with P values of 0.003 and 0.01 respectively, while no significant difference was recorded between OSEM methods (P = 0.48). The clinical model observer results were 0.791, 0.822, and 0.879, respectively, for the same patient cases and processing strategies used in the human observer study. CONCLUSIONS: Cardiac perfusion SPECT/CT using OSEM reconstruction at 25% of full dose has AUCs larger than FBP and closer to those of full-dose OSEM when read by human observers, potentially replacing the higher dose studies during clinical reading.


Subject(s)
Myocardial Perfusion Imaging/methods , Radiopharmaceuticals , Single Photon Emission Computed Tomography Computed Tomography/methods , Technetium Tc 99m Sestamibi , Adult , Aged , Aged, 80 and over , Dose Fractionation, Radiation , Female , Humans , Male , Middle Aged , ROC Curve , Retrospective Studies , Young Adult
3.
J Hazard Mater ; 402: 123433, 2021 01 15.
Article in English | MEDLINE | ID: mdl-32683153

ABSTRACT

Pb contamination of soils is a global problem. This paper discusses the ability of an Fe-rich waste, water treatment residual (WTR), to adsorb Pb(II). This was investigated using batch sorption experiments, X-ray diffraction, electron microprobe microanalysis, PHREEQC modeling and Extended X-ray Absorption Fine Structure (EXAFS) analysis. The WTR is composed of approximately 23 wt. % natural organic matter (NOM), 70 wt. % ferrihydrite and <10 wt. % silicate material. Pb(II) sorption to WTR was dependent on initial Pb(II) load, particle size, time and pH, but not on ionic strength. EXAFS analysis at the Pb LIII-edge confirmed that Pb(II) sorbed to WTR by co-existing bidentate edge-sharing and monodentate or corner-sharing complexes, with 2 O at ∼2.31-2.34 Å, 1 Fe at ∼3.32-3.34 Å, 2 Fe at ∼3.97-3.99 Å and 1 Pb at ∼3.82-3.85 Å. Linear combination showed that the Pb(II)-sorbed spectra were best fit with a ∼0.9 ± 0.1 and 0.1 ± 0.1 contribution from Pb(II)-sorbed ferrihydrite and Pb(II)-sorbed humic acid end members, respectively. Overall, we show that Pb(II) sorbs via strong inner-sphere complexation of Pb(II) to the ferrihydrite component of the WTR, which itself is stable over a wide pH range. Therefore, we suggest that Fe-rich WTR wastes could be used as effective adsorbents in Pb(II)-contaminated soils to help ensure sustainable terrestrial ecosystems.

4.
Nurs Adm Q ; 44(4): 357-364, 2020.
Article in English | MEDLINE | ID: mdl-32881807

ABSTRACT

Nursing Peer Review is a foundational and essential element of professional nursing practice. It is a systematic methodology to improve nurse and patient outcomes. The process can be labor-intensive and cumbersome in managing data from diverse data sources, especially if the process is manual. Directors of Professional Practice in a health care system partnered with an external vendor to create an interactive software platform where technology was leveraged to streamline the review process including review of aggregate data and trend analyses and generate reports using an electronic database. This resulted in a 75% reduction in the number of steps and subsequently the time required to complete the review process from initial screening to referral and closure. The generation of actionable data facilitated active engagement of clinical nurses in addressing identified clinical issues using process improvement and evidence-based practice methods. A critical feature of the software platform is that it provides actionable data that can be used to improve patient safety and fosters accountability for clinical nurses to promote self-regulation of nursing practice.


Subject(s)
Inventions/trends , Nursing/instrumentation , Peer Review/standards , Delivery of Health Care/methods , Humans , Nursing/methods , Peer Review/methods
5.
Ther Innov Regul Sci ; 54(6): 1489-1500, 2020 11.
Article in English | MEDLINE | ID: mdl-32617912

ABSTRACT

Incorporating patient perspectives into clinical studies is recognized as important to the development of high-quality, safe, and effective fit-for-patient medicines. However, no widely accepted methodology to help design more patient-centered studies has been established systematically. TransCelerate Biopharma Inc., a non-profit organization promoting collaboration across biopharmaceutical companies, organized a Patient Experience (PE) Initiative to create tools to intentionally include the patient perspective into the design and implementation of clinical studies. The resulting tools include the Patient Protocol Engagement Toolkit (P-PET), to engage patients early in protocol development, and the Study Participant Feedback Questionnaire (SPFQ), to assess patient experiences during clinical studies. To develop these toolkits, TransCelerate conducted a literature review and identified aspects of clinical studies that patients find either valuable or burdensome, or that affect participation, adherence, and engagement in a clinical study. The concepts identified were refined through elicitation of feedback from patient advisors, clinical study site advisors, and subject matter experts from member companies (MCs) of TransCelerate. This feedback was considered in identifying gaps, defining scientific methodology to understand how to evaluate patients' needs, and developing and refining the P-PET and the SPFQ. As part of the development process, descriptions/drafts of the tools were shared with patients, clinical site advisory groups, MCs, and the US Food and Drug Administration, and then revised. MCs simulated use of the tools, and feedback was incorporated into the final versions of the P-PET and SPFQ prior to public release. The P-PET and SPFQ are available free on the TransCelerate website.


Subject(s)
Patient Participation , Humans , Patient-Centered Care , Research Design , Surveys and Questionnaires , United States , United States Food and Drug Administration
6.
IEEE Trans Med Imaging ; 39(9): 2893-2903, 2020 09.
Article in English | MEDLINE | ID: mdl-32167887

ABSTRACT

Lowering the administered dose in SPECT myocardial perfusion imaging (MPI) has become an important clinical problem. In this study we investigate the potential benefit of applying a deep learning (DL) approach for suppressing the elevated imaging noise in low-dose SPECT-MPI studies. We adopt a supervised learning approach to train a neural network by using image pairs obtained from full-dose (target) and low-dose (input) acquisitions of the same patients. In the experiments, we made use of acquisitions from 1,052 subjects and demonstrated the approach for two commonly used reconstruction methods in clinical SPECT-MPI: 1) filtered backprojection (FBP), and 2) ordered-subsets expectation-maximization (OSEM) with corrections for attenuation, scatter and resolution. We evaluated the DL output for the clinical task of perfusion-defect detection at a number of successively reduced dose levels (1/2, 1/4, 1/8, 1/16 of full dose). The results indicate that the proposed DL approach can achieve substantial noise reduction and lead to improvement in the diagnostic accuracy of low-dose data. In particular, at 1/2 dose, DL yielded an area-under-the-ROC-curve (AUC) of 0.799, which is nearly identical to the AUC = 0.801 obtained by OSEM at full-dose ( p -value = 0.73); similar results were also obtained for FBP reconstruction. Moreover, even at 1/8 dose, DL achieved AUC = 0.770 for OSEM, which is above the AUC = 0.755 obtained at full-dose by FBP. These results indicate that, compared to conventional reconstruction filtering, DL denoising can allow for additional dose reduction without sacrificing the diagnostic accuracy in SPECT-MPI.


Subject(s)
Myocardial Perfusion Imaging , Algorithms , Humans , Image Processing, Computer-Assisted , Phantoms, Imaging , ROC Curve , Tomography, Emission-Computed, Single-Photon
7.
J Nucl Cardiol ; 27(2): 562-572, 2020 04.
Article in English | MEDLINE | ID: mdl-30406608

ABSTRACT

BACKGROUND: We previously optimized several reconstruction strategies in SPECT myocardial perfusion imaging (MPI) with low dose for perfusion-defect detection. Here we investigate whether reducing the administered activity can also maintain the diagnostic accuracy in evaluating cardiac function. METHODS: We quantified the myocardial motion in cardiac-gated stress 99m-Tc-sestamibi SPECT studies from 163 subjects acquired with full dose (29.8 ± 3.6 mCi), and evaluated the agreement of the obtained motion/thickening and ejection fraction (EF) measures at various reduced dose levels (uniform reduction or personalized dose) with that at full dose. We also quantified the detectability of abnormal motion via a receiver-operating characteristics (ROC) study. For reconstruction we considered both filtered backprojection (FBP) without correction for degradations, and iterative ordered-subsets expectation-maximization (OS-EM) with resolution, attenuation and scatter corrections. RESULTS: With dose level lowered to 25% of full dose, the obtained results on motion/thickening, EF and abnormal motion detection were statistically comparable to full dose in both reconstruction strategies, with Pearson's r > 0.9 for global motion measures between low dose and full dose. CONCLUSIONS: The administered activity could be reduced to 25% of full dose without degrading the function assessment performance. Low dose reconstruction optimized for perfusion-defect detection can be reasonable for function assessment in gated SPECT.


Subject(s)
Heart/diagnostic imaging , Myocardial Perfusion Imaging/methods , Technetium Tc 99m Sestamibi , Tomography, Emission-Computed, Single-Photon/methods , Aged , Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography/methods , Coronary Artery Disease/diagnostic imaging , Female , Heart Ventricles/diagnostic imaging , Humans , Male , Middle Aged , Motion , Perfusion , ROC Curve , Reproducibility of Results , Scattering, Radiation , Tomography, X-Ray Computed
8.
J Nucl Cardiol ; 27(1): 80-95, 2020 02.
Article in English | MEDLINE | ID: mdl-28432671

ABSTRACT

BACKGROUND: Respiratory motion can deteriorate image fidelity in cardiac perfusion SPECT. We determined the extent of respiratory motion, assessed its impact on image fidelity, and investigated the existence of gender differences, thereby examining the influence of respiratory motion in a large population of patients. METHODS: One thousand one hundred and three SPECT/CT patients underwent visual tracking of markers on their anterior surface during stress acquisition to track respiratory motion. The extent of motion was estimated by registration. Visual indicators of changes in cardiac slices with motion correction, and the correlation between the extent of motion with changes in segmental-counts were assessed. RESULTS: Respiratory motion in the head-to-feet direction was the largest component of motion, varying between 1.1 and 37.4 mm, and was statistically significantly higher (p = 0.002) for males than females. In 33.0% of the patients, motion estimates were larger than 10 mm. Patients progressively show more distinct visual changes with an increase in the extent of motion. The increase in segmental-count differences in the anterior, antero-lateral, and inferior segments correlated with the extent of motion. CONCLUSIONS: Respiratory motion correction diminished the artefactual reduction in anterior and inferior wall counts associated with respiratory motion. The extent of improvement was strongly related to the magnitude of motion.


Subject(s)
Artifacts , Heart Diseases/diagnostic imaging , Myocardial Perfusion Imaging , Respiratory Mechanics/physiology , Tomography, Emission-Computed, Single-Photon , Adult , Aged , Aged, 80 and over , Female , Heart Diseases/physiopathology , Humans , Male , Middle Aged , Motion , Radiopharmaceuticals , Sex Factors , Technetium Tc 99m Sestamibi , Young Adult
9.
J Nucl Cardiol ; 26(5): 1526-1538, 2019 Oct.
Article in English | MEDLINE | ID: mdl-30062470

ABSTRACT

BACKGROUND: In cardiac SPECT perfusion imaging, respiratory motion can cause non-uniform blurring in the reconstructed myocardium. We investigate the potential benefit of respiratory correction with respiratory-binned acquisitions, both at standard dose and at reduced dose, for defect detection and for left ventricular (LV) wall resolution. METHODS: We applied two reconstruction methods for respiratory motion correction: post-reconstruction motion correction (PMC) and motion-compensated reconstruction (MCR), and compared with reconstruction without motion correction (Non-MC). We quantified the presence of perfusion defects in reconstructed images by using the total perfusion deficit (TPD) scores and conducted receiver-operating-characteristic (ROC) studies using TPD. We quantified the LV spatial resolution by using the FWHM of its cross-sectional intensity profile. RESULTS: The values in the area-under-the-ROC-curve (AUC) achieved by MCR, PMC, and Non-MC at standard dose were 0.835, 0.830, and 0.798, respectively. Similar AUC improvements were also obtained by MCR and PMC over Non-MC at 50%, 25%, and 12.5% of full dose. Improvements in LV resolution were also observed with motion correction. CONCLUSIONS: Respiratory-binned acquisitions can improve perfusion-defect detection accuracy over traditional reconstruction both at standard dose and at reduced dose. Motion correction may contribute to achieving further dose reduction while maintaining the diagnostic accuracy of traditional acquisitions.


Subject(s)
Heart Ventricles/diagnostic imaging , Heart/diagnostic imaging , Movement , Tomography, Emission-Computed, Single-Photon , Adult , Aged , Area Under Curve , Female , Humans , Image Processing, Computer-Assisted , Male , Middle Aged , Myocardium/pathology , Perfusion , Phantoms, Imaging , ROC Curve , Radiation Dosage , Reproducibility of Results , Respiration
10.
IEEE Trans Med Imaging ; 38(6): 1466-1476, 2019 06.
Article in English | MEDLINE | ID: mdl-30530358

ABSTRACT

We propose a patient-specific ("personalized") approach for tailoring the injected activities to individual patients in order to achieve dose reduction in SPECT-myocardial perfusion imaging (MPI). First, we develop a strategy to determine the minimum dose levels required for each patient in a large set of clinical acquisitions (857 subjects) such that the reconstructed images are sufficiently similar to that obtained at conventional clinical dose. We then apply machine learning models to predict the required dose levels on an individual basis based on a set of patient attributes which include body measurements and various clinical variables. We demonstrate the personalized dose models for two commonly used reconstruction methods in clinical SPECT-MPI: 1) conventional filtered backprojection (FBP) with post-filtering and 2) ordered-subsets expectation-maximization (OS-EM) with corrections for attenuation, scatter and resolution, and evaluate their performance in perfusion-defect detection by using the clinical Quantitative Perfusion SPECT software package. The results indicate that the achieved dose reduction can vary greatly among individuals from their conventional clinical dose and that the personalized dose models can achieve further reduction on average compared with a global (non-patient specific) dose reduction approach. In particular, the average personalized dose level can be reduced to 58% and 54% of the full clinical dose, respectively, for FBP and OS-EM reconstruction, while without deteriorating the accuracy in perfusion-defect detection. Furthermore, with the average personalized dose further reduced to only 16% of full dose, OS-EM can still achieve a detection accuracy level comparable to that of FBP with full dose.


Subject(s)
Machine Learning , Myocardial Perfusion Imaging/methods , Precision Medicine/methods , Tomography, Emission-Computed, Single-Photon/methods , Aged , Female , Humans , Male , Middle Aged , ROC Curve , Radioisotopes/administration & dosage , Radiometry
12.
Water Res ; 140: 181-190, 2018 09 01.
Article in English | MEDLINE | ID: mdl-29715642

ABSTRACT

Dissolved Mn(III) has been identified at all stages throughout a Water Treatment Works (WTW) receiving inflow from a peaty upland catchment in NE England. Ninety percent of the influent total manganese into the WTW is particulate Mn, in the form of Mn oxide (>0.2 µm). Approximately 9% (mean value, n = 22, range of 0-100%) of the dissolved (<0.2 µm) influent Mn is present as dissolved Mn(III). Mn(III) concentrations are highest (mean of 49% of total dissolved Mn; n = 26, range of 17-89%) within the WTW where water comes into contact with the organic-rich sludges which are produced as waste products in the WTW. These Mn(III)-containing wastewaters are recirculated to the head of the works and constitute a large input of Mn(III) into the WTW. This is the first report of Mn(III) being identified in a WTW. The ability of Mn(III) to act as both an oxidant and a reductant is of interest to the water industry. Understanding the formation and removal of Mn(III) within may help reduce Mn oxide deposits in pipe networks. Further understanding how the ratio of Mn(III) to Mn(II) can be used to optimise dissolved Mn removal would save the water industry significant money in reducing discoloration 'events' at the customers' tap.


Subject(s)
Manganese/analysis , Water Pollutants, Chemical/analysis , Water Purification/methods , England , Prevalence , Wastewater/analysis
13.
Am J Crit Care ; 27(2): 89-96, 2018 03.
Article in English | MEDLINE | ID: mdl-29496764

ABSTRACT

BACKGROUND: Patients who receive prolonged endotracheal intubation (> 48 hours) are at risk for dysphagia. Nurses should conduct swallowing assessments after extubation because of the high likelihood of aspiration pneumonia developing. No valid and reliable postextubation dysphagia screening tools are available. OBJECTIVES: To establish content validity, analyze interrater reliability, and determine sensitivity and specificity of an evidence-based postextubation dysphagia screening tool developed by a multidisciplinary team. METHODS: A prospective nonexperimental study was conducted in 4 medical-surgical intensive care units in 4 hospitals. The study was conducted in 3 phases: (1) establishing content validity with clinical experts who participated in a Delphi survey, (2) establishing inter-rater reliability by agreement with nurses who simultaneously and independently completed the tool, and (3) establishing sensitivity and specificity with speech language pathologists and nurses who independently and blindly completed the tool for eligible patients. RESULTS: Individual item scores were > 0.82 and the overall content validity index was 0.93, indicating content validity. Interrater reliability was established (Cohen κ = 0.92). In 66 eligible patients, the prevalence of postextubation dysphagia was 56%, sensitivity of the postextubation dysphagia screening tool was 81%, and specificity was 69%. CONCLUSION: The reliability and validity of a postextubation dysphagia screening tool that can help nurses determine an extubated patient's ability to swallow after prolonged endotracheal intubation were established.


Subject(s)
Airway Extubation/nursing , Deglutition Disorders/diagnosis , Deglutition Disorders/etiology , Intubation, Intratracheal/adverse effects , Adult , Aged , Aged, 80 and over , Deglutition Disorders/nursing , Delphi Technique , Female , Humans , Intensive Care Units , Male , Middle Aged , Observer Variation , Prospective Studies , Reproducibility of Results , Sensitivity and Specificity , Time Factors
14.
J Hazard Mater ; 342: 724-731, 2018 Jan 15.
Article in English | MEDLINE | ID: mdl-28918290

ABSTRACT

The ability of a Fe-Mn binary oxide waste to adsorb arsenic (As) in a historically contaminated soil was investigated. Initial laboratory sorption experiments indicated that arsenite [As(III)] was oxidized to arsenate [As(V)] by the Mn oxide component, with concurrent As(V) sorption to the Fe oxide. The binary oxide waste had As(III) and As(V) adsorption capacities of 70mgg-1 and 32mgg-1 respectively. X-ray Absorption Near-Edge Structure and Extended X-ray Absorption Fine Structure at the As K-edge confirmed that all binary oxide waste surface complexes were As(V) sorbed by mononuclear bidentate corner-sharing, with 2 Fe at ∼3.27Ǻ. The ability of the waste to perform this coupled oxidation-sorption reaction in real soils was investigated with a 10% by weight addition of the waste to an industrially As contaminated soil. Electron probe microanalysis showed As accumulation onto the Fe oxide component of the binary oxide waste, which had no As innately. The bioaccessibility of As was also significantly reduced by 7.80% (p<0.01) with binary oxide waste addition. The results indicate that Fe-Mn binary oxide wastes could provide a potential in situ remediation strategy for As and Pb immobilization in contaminated soils.

15.
J Nucl Cardiol ; 25(6): 2117-2128, 2018 12.
Article in English | MEDLINE | ID: mdl-28537039

ABSTRACT

BACKGROUND: We investigated the extent to which the administered dose (activity) level can be reduced without sacrificing diagnostic accuracy for three reconstruction strategies for SPECT-myocardial perfusion imaging (MPI). METHODS: We optimized the parameters of the three reconstruction strategies for perfusion-defect detection over a range of simulated administered dose levels using a set of hybrid studies (derived from 190 subjects) consisting of clinical SPECT-MPI data modified to contain realistic simulated lesions. The optimized strategies we considered are filtered backprojection (FBP) with no correction for degradations, ordered-subsets expectation-maximization (OS-EM) with attenuation correction (AC), scatter correction (SC), and resolution correction (RC), and OS-EM with scatter and resolution correction only. Each study was evaluated using a total perfusion deficit (TPD) score computed by the Quantitative Perfusion SPECT (QPS) software package. We conducted a receiver operating characteristics (ROC) study based on the TPD scores for each dose level and reconstruction strategy. RESULTS: For FBP, the achieved optimum values of the area under the ROC curve (AUC) at 100%, 50%, 25%, and 12.5% of standard dose were 0.75, 0.74, 0.72, and 0.70, respectively, compared to 0.81, 0.79, 0.76, and 0.74 for OS-EM with AC-SC-RC and 0.78, 0.77, 0.74, 0.72 for OS-EM with SC-RC. CONCLUSIONS: Our results suggest that studies reconstructed by OS-EM with AC-SC-RC could possibly be reduced, on average, to 25% of the originally administered dose without causing diagnostic accuracy (AUC) to decrease below that of FBP.


Subject(s)
Image Processing, Computer-Assisted/methods , Myocardial Perfusion Imaging/methods , Tomography, Emission-Computed, Single-Photon/methods , Adult , Aged , Female , Humans , Male , Middle Aged , Radiation Dosage
16.
J Nurs Adm ; 47(9): 421-425, 2017 Sep.
Article in English | MEDLINE | ID: mdl-28834803

ABSTRACT

Professional practice models (PPMs) are an integral part of any organization on the Magnet® journey, whether initial designation or redesignation. Through the journey, the PPM should become embedded within the nursing culture. Leadership at multiple levels is crucial to ensure successful adoption and implementation.


Subject(s)
Nurse Administrators/organization & administration , Nurse Clinicians/organization & administration , Professional Practice/organization & administration , Staff Development/organization & administration , Humans , Leadership , Models, Organizational , Nurse Administrators/standards , Nurse Clinicians/standards , Organizational Culture , Professional Practice/standards , Staff Development/methods , Staff Development/standards
17.
Med Phys ; 44(2): 437-450, 2017 Feb.
Article in English | MEDLINE | ID: mdl-28032913

ABSTRACT

PURPOSE: Amplitude-based respiratory gating is known to capture the extent of respiratory motion (RM) accurately but results in residual motion in the presence of respiratory hysteresis. In our previous study, we proposed and developed a novel approach to account for respiratory hysteresis by applying the Bouc-Wen (BW) model of hysteresis to external surrogate signals of anterior/posterior motion of the abdomen and chest with respiration. In this work, using simulated and clinical SPECT myocardial perfusion imaging (MPI) studies, we investigate the effects of respiratory hysteresis and evaluate the benefit of correcting it using the proposed BW model in comparison with the abdomen signal typically employed clinically. METHODS: The MRI navigator data acquired in free-breathing human volunteers were used in the specially modified 4D NCAT phantoms to allow simulating three types of respiratory patterns: monotonic, mild hysteresis, and strong hysteresis with normal myocardial uptake, and perfusion defects in the anterior, lateral, inferior, and septal locations of the mid-ventricular wall. Clinical scans were performed using a Tc-99m sestamibi MPI protocol while recording respiratory signals from thoracic and abdomen regions using a visual tracking system (VTS). The performance of the correction using the respiratory signals was assessed through polar map analysis in phantom and 10 clinical studies selected on the basis of having substantial RM. RESULTS: In phantom studies, simulations illustrating normal myocardial uptake showed significant differences (P < 0.001) in the uniformity of the polar maps between the RM uncorrected and corrected. No significant differences were seen in the polar map uniformity across the RM corrections. Studies simulating perfusion defects showed significantly decreased errors (P < 0.001) in defect severity and extent for the RM corrected compared to the uncorrected. Only for the strong hysteretic pattern, there was a significant difference (P < 0.001) among the RM corrections. The errors in defect severity and extent for the RM correction using abdomen signal were significantly higher compared to that of the BW (severity = -4.0%, P < 0.001; extent = -65.4%, P < 0.01) and chest (severity = -4.1%, P < 0.001; extent = -52.5%, P < 0.01) signals. In clinical studies, the quantitative analysis of the polar maps demonstrated qualitative and quantitative but not statistically significant differences (P = 0.73) between the correction methods that used the BW signal and the abdominal signal. CONCLUSIONS: This study shows that hysteresis in respiration affects the extent of residual motion left in the RM-binned data, which can impact wall uniformity and the visualization of defects. Thus, there appears to be the potential for improved accuracy in reconstruction in the presence of hysteretic RM with the BW model method providing a possible step in the direction of improvement.


Subject(s)
Movement , Myocardial Perfusion Imaging/methods , Respiration , Tomography, Emission-Computed, Single-Photon/methods , Abdomen/diagnostic imaging , Artifacts , Cardiac-Gated Imaging Techniques/methods , Computer Simulation , Heart/diagnostic imaging , Humans , Magnetic Resonance Imaging , Models, Biological , Motion , Myocardial Perfusion Imaging/instrumentation , Phantoms, Imaging , Radiopharmaceuticals , Technetium Tc 99m Sestamibi , Tomography, Emission-Computed, Single-Photon/instrumentation
20.
IEEE Trans Nucl Sci ; 63(3): 1419-1425, 2016 Jun.
Article in English | MEDLINE | ID: mdl-28042170

ABSTRACT

We have recently been successful in the development and testing of rigid-body motion tracking, estimation and compensation for cardiac perfusion SPECT based on a visual tracking system (VTS). The goal of this study was to evaluate in patients the effectiveness of our rigid-body motion compensation strategy. Sixty-four patient volunteers were asked to remain motionless or execute some predefined body motion during an additional second stress perfusion acquisition. Acquisitions were performed using the standard clinical protocol with 64 projections acquired through 180 degrees. All data were reconstructed with an ordered-subsets expectation-maximization (OSEM) algorithm using 4 projections per subset and 5 iterations. All physical degradation factors were addressed (attenuation, scatter, and distance dependent resolution), while a 3-dimensional Gaussian rotator was used during reconstruction to correct for six-degree-of-freedom (6-DOF) rigid-body motion estimated by the VTS. Polar map quantification was employed to evaluate compensation techniques. In 54.7% of the uncorrected second stress studies there was a statistically significant difference in the polar maps, and in 45.3% this made a difference in the interpretation of segmental perfusion. Motion correction reduced the impact of motion such that with it 32.8 % of the polar maps were statistically significantly different, and in 14.1% this difference changed the interpretation of segmental perfusion. The improvement shown in polar map quantitation translated to visually improved uniformity of the SPECT slices.

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