COVID-19 Stroke Apical Lung Examination Study 2: a national prospective CTA biomarker study of the lung apices, in patients presenting with suspected acute stroke (COVID SALES 2)

BACKGROUND

Apical ground-glass opacification (GGO) identified on CT angiography (CTA) performed for suspected acute stroke was developed in 2020 as a coronavirus-disease-2019 (COVID-19) diagnostic and prognostic biomarker in a retrospective study during the first wave of COVID-19.

OBJECTIVE

To prospectively validate whether GGO on CTA performed for suspected acute stroke is a reliable COVID-19 diagnostic and prognostic biomarker and whether it is reliable for COVID-19 vaccinated patients.

METHODS

In this prospective, pragmatic, national, multi-center validation study performed at 13 sites, we captured study data consecutively in patients undergoing CTA for suspected acute stroke from January-March 2021. Demographic and clinical features associated with stroke and COVID-19 were incorporated. The primary outcome was the likelihood of reverse-transcriptase-polymerase-chain-reaction swab-test-confirmed COVID-19 using the GGO biomarker. Secondary outcomes investigated were functional status at discharge and survival analyses at 30 and 90 days. Univariate and multivariable statistical analyses were employed.

RESULTS

CTAs from 1,111 patients were analyzed, with apical GGO identified in 8.5 % during a period of high COVID-19 prevalence. GGO showed good inter-rater reliability (Fleiss κ = 0.77); and high COVID-19 specificity (93.7 %, 91.8-95.2) and negative predictive value (NPV; 97.8 %, 96.5-98.6). In subgroup analysis of vaccinated patients, GGO remained a good diagnostic biomarker (specificity 93.1 %, 89.8-95.5; NPV 99.7 %, 98.3-100.0). Patients with COVID-19 were more likely to have higher stroke score (NIHSS (mean +/- SD) 6.9 +/- 6.9, COVID-19 negative, 9.7 +/- 9.0, COVID-19 positive; p = 0.01), carotid occlusions (6.2 % negative, 14.9 % positive; p = 0.02), and larger infarcts on presentation CT (ASPECTS 9.4 +/- 1.5, COVID-19 negative, 8.6 +/- 2.4, COVID-19 positive; p = 0.00). After multivariable logistic regression, GGO (odds ratio 15.7, 6.2-40.1), myalgia (8.9, 2.1-38.2) and higher core body temperature (1.9, 1.1-3.2) were independent COVID-19 predictors. GGO was associated with worse functional outcome on discharge and worse survival after univariate analysis. However, after adjustment for factors including stroke severity, GGO was not independently predictive of functional outcome or mortality.

CONCLUSION

Apical GGO on CTA performed for patients with suspected acute stroke is a reliable diagnostic biomarker for COVID-19, which in combination with clinical features may be useful in COVID-19 triage.

Bayesian penalized likelihood PET reconstruction impact on quantitative metrics in diffuse large B-cell lymphoma

Evaluate the quantitative, subjective (Deauville score [DS]) and reader agreement differences between standard ordered subset expectation maximization (OSEM) and Bayesian penalized likelihood (BPL) positron emission tomography (PET) reconstruction methods. A retrospective review of 104 F-18 fluorodeoxyglucose PET/computed tomography (CT) exams among 52 patients with diffuse large B-cell lymphoma. An unblinded radiologist moderator reviewed both BPL and OSEM PET/CT exams. Four blinded radiologists then reviewed the annotated cases to provide a visual DS for each annotated lesion. Significant (P < .001) differences in BPL and OSEM PET methods were identified with greater standard uptake value (SUV) maximum and SUV mean for BPL. The DS was altered in 25% of cases when BPL and OSEM were reviewed by the same radiologist. Interobserver DS agreement was higher for OSEM (>1 cm lesion = 0.89 and ≤1 cm lesion = 0.84) compared to BPL (>1 cm lesion = 0.85 and ≤1 cm lesion = 0.81). Among the 4 readers, average intraobserver visual DS agreement between OSEM and BPL was 0.67 for lesions >1cm and 0.4 for lesions ≤1 cm. F-18 Fluorodeoxyglucose PET/CT of diffuse large B-cell lymphoma reconstructed with BPL has higher SUV values, altered DSs and reader agreement when compared to OSEM. This report finds volumetric PET measurements such as metabolic tumor volume to be similar between BPL and OSEM PET reconstructions. Efforts such as adoption of European Association Research Ltd accreditation should be made to harmonize PET data with an aim at balancing the need for harmonization and sensitivity for lesion detection.

Comparison of 11C-Pittsburgh Compound B and 18F-Flutemetamol White Matter Binding in PET

PET imaging with β-amyloid ligands is emerging as a molecular imaging technique targeting white matter integrity and demyelination. β-amyloid PET ligands such as 11C-Pittsburgh compound B (11C-PiB) have been considered for quantitative measurement of myelin content changes in multiple sclerosis, but 11C-PiB is not commercially available given its short half-life. A 18F PET ligand such as flutemetamol with a longer half-life may be an alternative, but its ability to differentiate white matter hyperintensities (WMH) from normal-appearing white matter (NAWM) and its relationship with age remains to be investigated. Methods: Cognitively unimpaired (CU) older and younger adults (n = 61) were recruited from the community responding to a study advertisement for β-amyloid PET. Participants prospectively underwent MRI, 11C-PiB, and 18F-flutemetamol PET scans. MRI fluid-attenuated inversion recovery images were segmented into WMH and NAWM and registered to the T1-weighted MRI. 11C-PiB and 18F-flutemetamol PET images were also registered to the T1-weighted MRI. 11C-PiB and 18F-flutemetamol SUV ratios (SUVrs) from the WMH and NAWM were calculated using cerebellar crus uptake as a reference for both 11C-PiB and 18F-flutemetamol. Results: The median age was 38 y (range, 30-48 y) in younger adults and 67 y (range, 61-83 y) in older adults. WMH and NAWM SUVrs were higher with 18F-flutemetamol than with 11C-PiB in both older (P < 0.001) and younger (P < 0.001) CU adults. 11C-PiB and 18F-flutemetamol SUVrs were higher in older than in younger CU adults in both WMH (P < 0.001) and NAWM (P < 0.001). 11C-PiB and 18F-flutemetamol SUVrs were higher in NAWM than WMH in both older (P < 0.001) and younger (P < 0.001) CU adults. There was no apparent difference between 11C-PiB and 18F-flutemetamol SUVrs in differentiating WMH from NAWM in older and in younger adults. Conclusion:11C-PiB and 18F-flutemetamol show a similar topographic pattern of uptake in white matter with a similar association with age in WMH and NAWM. 11C-PiB and 18F-flutemetamol can also effectively distinguish between WMH and NAWM. However, given its longer half-life, commercial availability, and higher binding potential, 18F-flutemetamol can be an alternative to 11C-PiB in molecular imaging studies specifically targeting multiple sclerosis to evaluate white matter integrity.

Perceptions of an eHealth family-based cardiovascular disease risk reduction intervention: a mixed methods study

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): Department for the Economy, Northern Ireland

Introduction

Controllable cardiovascular disease (CVD) risk factors are often initiated in the family home, yet risk reduction is seldom targeted toward families. Participatory design of eHealth interventions with end-users has potential to increase acceptability and adherence of such interventions. Despite their shared risk of developing CVD, few eHealth interventions target both parents and children at CVD risk. Therein lies an evidence gap; the need for coproduction of a family-based eHealth intervention aimed at early CVD prevention.

Purpose

The aim of this study was to identify the perceptions of families towards the design, functionality and acceptability of an eHealth, family-based, CVD prevention intervention.

Methods

Thee online focus groups comprising six families were conducted between April and May 2021. Families consisted of at least one parent who met CVD risk factor criteria, and at least one child aged five to 17 years. Content analysis and narrative synthesis were used to identify categories and subcategories regarding development of and engagement with the proposed intervention. Additionally, quantitative, and demographic measures were used to determine psychosocial and health profiles.

Results

Three categories were identified from the focus groups:

1) previous experiences of using health-related apps or devices

2) expectations of a newly developed eHealth family-based CVD prevention intervention

3) motivators for engagement with the intervention

Goal setting, rewards, accountability, adaptability, recording achievements and competition were considered crucial motivators for engagement for both parents and children. Participants welcomed the intervention, and advised they would prefer a free, personalised, easy-to-use, non-time-consuming intervention, with multiple content formats, and additional information available should they seek to access it. Parents conveyed satisfactory general self-efficacy and quality of life, low anxiety and depression and high perceived social support.

Conclusions

Overall, families were constructive and forthcoming towards the idea of an eHealth, family-based CVD prevention intervention. These findings informed a prototype of a family-based eHealth intervention aimed at early CVD prevention. The prototype is currently being developed with plans for piloting via a randomised controlled trial in the home environment, by families as an early intervention for the prevention of CVD.

PSMA as a Theranostic Target in Hepatocellular Carcinoma: Immunohistochemistry and 68 Ga-PSMA-11 PET Using Cyclotron-Produced 68 Ga

Prostate-specific membrane antigen (PSMA) is a validated target for molecular diagnostics and targeted radionuclide therapy. Our purpose was to evaluate PSMA expression in hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), and hepatic adenoma (HCA); investigate the genetic pathways in HCC associated with PSMA expression; and evaluate HCC detection rate with 68 Ga-PSMA-11 positron emission tomography (PET). In phase 1, PSMA immunohistochemistry (IHC) on HCC (n = 148), CCA (n = 111), and HCA (n = 78) was scored. In a subset (n = 30), messenger RNA (mRNA) data from the Cancer Genome Atlas HCC RNA sequencing were correlated with PSMA expression. In phase 2, 68 Ga-PSMA-11 PET was prospectively performed in patients with treatment-naïve HCC on a digital PET scanner using cyclotron-produced 68 Ga. Uptake was graded qualitatively and semi-quantitatively using standard metrics. On IHC, PSMA expression was significantly higher in HCC compared with CCA and HCA (P < 0.0001); 91% of HCCs (n = 134) expressed PSMA, which principally localized to tumor-associated neovasculature. Higher tumor grade was associated with PSMA expression (P = 0.012) but there was no association with tumor size (P = 0.14), fibrosis (P = 0.35), cirrhosis (P = 0.74), hepatitis B virus (P = 0.31), or hepatitis C virus (P = 0.15). Overall survival tended to be longer in patients without versus with PSMA expression (median overall survival: 4.2 vs. 1.9 years; P = 0.273). FGF14 (fibroblast growth factor 14) mRNA expression correlated positively (rho = 0.70; P = 1.70 × 10-5 ) and MAD1L1 (Mitotic spindle assembly checkpoint protein MAD1) correlated negatively with PSMA expression (rho = -0.753; P = 1.58 × 10-6 ). Of the 190 patients who met the eligibility criteria, 31 patients with 39 HCC lesions completed PET; 64% (n = 25) lesions had pronounced 68 Ga-PSMA-11 standardized uptake value: SUVmax (median [range] 9.2 [4.9-28.4]), SUVmean 4.7 (2.4-12.7), and tumor-to-liver background ratio 2 (1.1-11). Conclusion: Ex vivo expression of PSMA in neovasculature of HCC translates to marked tumor avidity on 68 Ga-PSMA-11 PET, which suggests that PSMA has the potential as a theranostic target in patients with HCC.

Prediction of MGMT Status for Glioblastoma Patients Using Radiomics Feature Extraction From 18F-DOPA-PET Imaging

PURPOSE

Methylation of the O⁶-methylguanine methyltransferase (MGMT) gene promoter is associated with improved treatment response and survival in patients with glioblastoma (GB), but the necessary pathologic specimen can be nondiagnostic. In this study, we assessed whether radiomics features from pretreatment ¹⁸F-DOPA positron emission tomography (PET) imaging could be used to predict pathologic MGMT status.

METHODS AND MATERIALS

This study included 86 patients with newly diagnosed GB, split into 3 groups (training, validating, and predicting). We performed a radiomics analysis on ¹⁸F-DOPA PET images by extracting features from 2 tumor-based contours: a "Gold" contour of all abnormal uptake per expert nuclear medicine physician and a high-grade glioma (HGG) contour based on a tumor-to-normal hemispheric ratio >2.0, representing the most aggressive components. Feature selection was performed by comparing the weighted feature importance and filtering with bivariate analysis. Optimization of model parameters was explored using grid search with selected features. The stability of the model with increasing input features was also investigated for model robustness. The model predictions were then applied by comparing the overall survival probability of the patients with GB and unknown MGMT status versus those with known MGMT status.

RESULTS

A radiomics signature was constructed to predict MGMT methylation status. Using features extracted from HGG contour alone with a random forest model, we achieved 80% ± 10% accuracy for 95% confidence level in predicting MGMT status. The prediction accuracy was not improved with the addition of the Gold contour or with more input features. The model was applied to the patients with unknown MGMT methylation status. The prediction results are consistent with what is expected using overall survival as a surrogate.

CONCLUSIONS

This study suggests that 3 features from radiomics modeling of ¹⁸F-DOPA PET imaging can predict MGMT methylation status with reasonable accuracy. These results could provide valuable therapeutic guidance for patients in whom MGMT testing is inconclusive or nondiagnostic.

Myocardial Energetics in Heart Failure With Preserved Ejection Fraction

BACKGROUND

The role of coronary microvascular disease and its impact on functional and energetic reserve in heart failure with preserved ejection fraction (HFpEF) remains unclear. We hypothesized that in response to submaximal pharmacologic stress (dobutamine), patients with HFpEF have impairment in left ventricular (LV) myocardial mechanical (external work [EW]), energetic (myocardial O₂ consumption [MVO₂]), and myocardial blood flow (MBF) reserve. We further assessed whether coupling of MBF to EW is impaired in HFpEF and associated with compensatory increases or pathological decreases in myocardial O₂ extraction. Lastly, we assessed whether coupling of MVO₂ to EW (mechanical efficiency) was impaired in HFpEF.

METHODS AND RESULTS

In prospectively enrolled patients with HFpEF (n=19) and age/sex-matched healthy controls (n=19), we performed ¹¹C-acetate positron emission tomography assessing MVO₂ and MBF at rest and during dobutamine infusion. EW was calculated as stroke volume (echo)×end-systolic pressure×heart rate. At rest, compared with controls, patients with HFpEF had higher LV EW, MVO₂, and MBF. With dobutamine, LV EW, MVO₂, and MBF increased in both HFpEF and controls; however, the magnitude of increases was significantly smaller in HFpEF. In both groups, MBF increased in relation to EW, but in HFpEF, the slope of the relationship was significantly smaller than in controls. Myocardial O₂ extraction was increased in HFpEF. Mechanical efficiency was similar in HFpEF and controls. In a post hoc analysis, HFpEF patients with LV hypertrophy (n=10) had significant reductions in LV mechanical efficiency relative to controls.

CONCLUSIONS

In HFpEF during submaximal dobutamine stress, there is myocardial mechanical-, energetic- and flow-reserve dysfunction with impaired coupling of blood flow to demand and slight increases in myocardial O₂ extraction. These findings provide evidence that coronary microvascular dysfunction is present in HFpEF, limits O₂ supply relative to demand, and is associated with reserve dysfunction.

Comparison of [18F] FDG-PET/MRI and Clinical Findings for Assessment of Suspected Lumbar Facet Joint Pain: A Prospective Study to Characterize Candidate Nonanatomic Imaging Biomarkers and Potential Impact on Management

BACKGROUND AND PURPOSE

Prior retrospective studies have suggested that both T2 hyperintensity and gadolinium enhancement on fat-suppressed MR imaging are associated with lumbar facet joint pain, but prospective evaluation of FDG-PET/MR imaging with a standardized protocol and correlation to clinical findings are lacking. The primary aim was to prospectively assess a standardized FDG-PET/MRI protocol in patients with suspected facetogenic low back pain, with determination of the concordance of imaging and clinical findings.

MATERIALS AND METHODS

Ten patients with clinically suspected facetogenic low back pain were prospectively recruited with a designation of specific facet joints implicated clinically. Subsequently, patients underwent an FDG-PET/MR imaging examination with gadolinium. Each facet joint was graded for perifacet signal change on MR imaging and FDG activity. The frequency and correlation of MR imaging, FDG-PET, and clinical findings were determined.

RESULTS

FDG activity showed high concordance with high overall MR imaging scores (concordance correlation coefficient = 0.79). There was concordance of the clinical side of pain with the side of high overall MR imaging scores and increased FDG activity on 12/20 (60%) sides. Both a high overall MR imaging score (concordance correlation coefficient = 0.12) and FDG-PET findings positive for increased activity (concordance correlation coefficient = 0.10) had low concordance with the specific clinically implicated facet joints. Increased FDG activity or high MR imaging scores or both were present in only 10/29 (34%) facet joints that had been clinically selected for percutaneous intervention. Eleven (11%) facet joints that had not been selected for treatment demonstrated these imaging findings.

CONCLUSIONS

There was low concordance of perifacet signal change and FDG activity with clinically implicated facet joints. This could indicate either the potential to change patient management or a lack of biomarker accuracy. Therefore, additional larger randomized studies with the use of comparative medial branch blocks would be useful to further investigate the clinical utility of these findings.

Subcutaneous adipose tissue free fatty acid uptake measured using positron emission tomography and adipose biopsies in humans

Positron emission tomography (PET) radiopharmaceuticals can noninvasively measure free fatty acid (FFA) uptake into adipose tissue. We studied 29 volunteers to test whether abdominal and femoral subcutaneous adipose tissue FFA uptake measured using [1-¹¹C]palmitate PET agrees with FFA storage rates measured using an intravenous bolus of [1-¹⁴C]palmitate and adipose biopsies. The dynamic left ventricular cavity PET images combined with blood sample radioactivity corrected for the ¹¹CO₂ content were used to create the blood time activity curve (TAC), and the constant (K_i) was determined using Patlak analysis of the TACs generated for regions of interest in abdominal subcutaneous fat. These data were used to calculate palmitate uptake rates in abdominal subcutaneous adipose tissue (µmol·kg^-1·min^-1). Immediately after the dynamic imaging, a static image of the thigh was taken to measure the standardized uptake value (SUV) in thigh adipose tissue, which was scaled to each participant's abdominal adipose tissue SUV to calculate thigh adipose palmitate uptake rates. Abdominal adipose palmitate uptake using PET [1-¹¹C]palmitate was correlated with, but significantly (P < 0.001) greater than, FFA storage measured using [1-¹⁴C]palmitate and adipose biopsy. Thigh adipose palmitate measured using PET calculation was positively correlated (R² = 0.44, P < 0.0001) with and not different from the biopsy approach. The relative differences between PET measured abdominal subcutaneous adipose tissue palmitate uptake and biopsy-measured palmitate storage were positively correlated (P = 0.03) with abdominal subcutaneous fat. We conclude that abdominal adipose tissue FFA uptake measured using PET does not equate to adipose FFA storage measured using biopsy techniques.

Free fatty acid flux measured using [1-11C]palmitate positron emission tomography and [U-13C]palmitate in humans

PET radiopharmaceuticals can noninvasively measure free fatty acid (FFA) tissue uptake. Investigators often use PET scan-derived data to calculate FFA flux. We tested whether the [1-¹¹C]palmitate PET measures of palmitate flux provide results equivalent to a continuous infusion of [U-¹³C]palmitate. Nine volunteers participated in study 1 to evaluate whether a rapidly (10-20 s) given bolus of [1-¹¹C]palmitate affects calculated flux results. Thirty volunteers participated in study 2, which was identical to study 1 except that the [1-¹¹C]palmitate bolus was given over 1 min. Volunteers in both studies also received a continuous intravenous infusion of [U-¹³C]palmitate. Plasma palmitate concentrations and enrichment were measured by liquid chromatography-mass spectrometry. The PET/CT images were analyzed on a workstation running PMOD. Palmitate flux was estimated using PET time-activity curve (TAC) data from regions of interest in the left ventricle (LV) and aorta both with and without hybrid TACs that employed the ¹¹CO₂-corrected data for the first 5 min and the ¹¹CO₂-corrected blood radioactivity for the remainder of the PET scan. Palmitate flux in study 1 measured with PET [1-¹¹C]palmitate and [U-¹³C]palmitate were not correlated, and the PET [1-¹¹C]palmitate flux was significantly less than the [U-¹³C]palmitate measured flux. In study 2, the palmitate flux using PET [1-¹¹C]palmitate hybrid LV models provided closer mean estimates of [U-¹³C]palmitate measured flux. The best PET calculation approaches predicted 64% of the interindividual variance in [U-¹³C]palmitate measured flux. Palmitate kinetics measured using [1-¹¹C]palmitate/PET do not provide the same palmitate kinetic results as the continuous infusion [U-¹³C]palmitate approach.

Prospective trial evaluating the sensitivity and specificity of 3,4-dihydroxy-6-[18F]-fluoro-L-phenylalanine (18F-DOPA) PET and MRI in patients with recurrent gliomas

Treatment-related changes can be difficult to differentiate from progressive glioma using MRI with contrast (CE). The purpose of this study is to compare the sensitivity and specificity of 18F-DOPA-PET and MRI in patients with recurrent glioma. Thirteen patients with MRI findings suspicious for recurrent glioma were prospectively enrolled and underwent 18F-DOPA-PET and MRI for neurosurgical planning. Stereotactic biopsies were obtained from regions of concordant and discordant PET and MRI CE, all within regions of T2/FLAIR signal hyperintensity. The sensitivity and specificity of 18F-DOPA-PET and CE were calculated based on histopathologic analysis. Receiver operating characteristic curve analysis revealed optimal tumor to normal (T/N) and SUVmax thresholds. In the 37 specimens obtained, 51% exhibited MRI contrast enhancement (M+) and 78% demonstrated 18F-DOPA-PET avidity (P+). Imaging characteristics included M-P- in 16%, M-P+ in 32%, M+P+ in 46% and M+P- in 5%. Histopathologic review of biopsies revealed grade II components in 16%, grade III in 43%, grade IV in 30% and no tumor in 11%. MRI CE sensitivity for recurrent tumor was 52% and specificity was 50%. PET sensitivity for tumor was 82% and specificity was 50%. A T/N threshold > 2.0 altered sensitivity to 76% and specificity to 100% and SUVmax > 1.36 improved sensitivity and specificity to 94 and 75%, respectively. 18F-DOPA-PET can provide increased sensitivity and specificity compared with MRI CE for visualizing the spatial distribution of recurrent gliomas. Future studies will incorporate 18F-DOPA-PET into re-irradiation target volume delineation for RT planning.

Safety, pharmacokinetics, metabolism and radiation dosimetry of 18F-tetrafluoroborate (18F-TFB) in healthy human subjects

BACKGROUND

18F-Tetrafluoroborate (18F-TFB) is a promising iodide analog for PET imaging of thyroid cancer and sodium/iodide symporter (NIS) reporter activity in viral therapy applications. The aim of this study was to evaluate the safety, pharmacokinetics, biodistribution, and radiation dosimetry of high-specific activity 18F-TFB in healthy human subjects.

METHODS

18F-TFB was synthesized with specific activity of 3.2 ± 1.3 GBq/μmol (at the end of synthesis). Dynamic and whole-body static PET/CT scans over 4 h were performed after intravenous administration of 18F-TFB (333-407 MBq) in four female and four male healthy volunteers (35 ± 11 years old). Samples of venous blood and urine were collected over the imaging period and analyzed by ion-chromatography HPLC to determine tracer stability. Vital signs and clinical laboratory safety assays were measured to evaluate safety.

RESULTS

18F-TFB administration was well tolerated with no significant findings on vital signs and no clinically meaningful changes in clinical laboratory assays. Left-ventricular blood pool time-activity curves showed a multi-phasic blood clearance of 18F-radioactivity with the two rapid clearance phases over the first 20 min, followed by a slower clearance phase. HPLC analysis showed insignificant 18F-labeled metabolites in the blood and urine over the length of the study (4 h). High uptakes were seen in the thyroid, stomach, salivary glands, and bladder. Urinary clearance of 18F-TFB was prominent. Metabolic stability was evidenced by low accumulation of 18F-radioactivity in the bone. Effective doses were 0.036 mSv/MBq in males and 0.064 mSv/MBq in females (p = 0.08, not significant).

CONCLUSIONS

This initial study in healthy human subjects showed 18F-TFB was safe and distributed in the human body similar to other iodide analogs. These data support further translational studies with 18F-TFB as NIS gene reporter and imaging biomarker for thyroid cancer and other disease processes that import iodide.

Comparison of [18F]Flutemetamol and [11C]Pittsburgh Compound-B in cognitively normal young, cognitively normal elderly, and Alzheimer's disease dementia individuals

Background

Understanding the variation in uptake between different amyloid PET tracers is important to appropriately interpret data using different amyloid tracers. Therefore, we compared the uptake differences in [¹⁸F]Flutemetamol (FMT) and [¹¹C]PiB (PiB) PET in the same people.

Methods

Structural MRI, FMT PET and PiB PET were each performed in 30 young cognitively normal (yCN), 31 elderly cognitively normal (eCN) and 21 Alzheimer's disease dementia (AD) participants. PiB and FMT images for each participant were compared quantitatively using voxel- and region-based analyses. Region of interest (ROI) analyses included comparisons of grey matter (GM) regions as well as white matter (WM) regions. Regional comparisons of each tracer between different groups and comparisons of the two modalities within the different groups were performed. To compare mean SUVr between modalities, and between diagnostic groups, we used paired t-tests and Student's t-test, respectively. We also compared the ability of the two tracers to discriminate between diagnostic groups using AUROC estimates. The effect of using different normalization regions on SUVr values was also evaluated.

Results

Both FMT and PiB showed greater uptake throughout GM structures in AD vs. eCN or yCN. In all dual-modality group comparisons (FMT vs. PiB in yCN, eCN, and AD), greater WM uptake was seen with FMT vs. PiB. In yCN and eCN greater diffuse GM uptake was seen with FMT vs. PiB. When comparing yCN to eCN within each tracer, greater WM uptake was seen in eCN vs yCN.

Conclusions

Flutemetamol and PiB show similar topographical GM uptake in AD and CN participants and the tracers show comparable group discrimination. Greater WM accumulation with FMT suggests that quantitative differences vs. PiB will be apparent when using WM or GM as a reference region. Both imaging tracers demonstrate increased WM uptake in older people. These findings suggest that using different amyloid tracers or different methods of analyses in serial brain imaging in an individual may result in artifactual amyloid change measurements. Clinical use of several amyloid tracers in the same patient will have challenges that need to be carefully considered.

•

White matter uptake is quantitatively elevated in elderly vs. younger control subjects in both FMT and PiB PET scans.

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Quantitatively greater white matter uptake is seen in FMT vs. PiB in Alzheimer’s disease dementia and control subjects.

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Variations between FMT and PiB may create the false appearance of changing brain amyloid levels on serial imaging.

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FMT and PiB have comparable ability to categorize Alzheimer’s disease dementia and control subjects cross-sectionally.

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Methods to cross-calibrate different amyloid PET tracers will need to be validated in serial imaging paradigms.

Tau-PET uptake: Regional variation in average SUVR and impact of amyloid deposition

Introduction

Tau-positron emission tomography (PET) imaging with AV1451 is sensitive to Alzheimer disease (AD)–related tau deposition in the brain. We (1) examined regional variation of average tau-PET standardized uptake value ratios (SUVRs) in a young normal population (30–49 years) and corrected for the regional variability and (2) tested if the standardized values (z-scores) scaled appropriately to capture regional Alzheimer-specific (i.e., amyloid sensitive) tau-PET changes in individuals aged 50+ years.

Methods

We identified 490 individuals (70 between 30–49 years as a reference group and 420 cognitively normal between 50–95 years of age) with tau-PET and amyloid PET scans from the Mayo Clinic Study of Aging.

Results

There was intrinsic regional variability in average tau-PET SUVR with uptakes higher in some regions than others, even in the younger individuals who would have minimal or no neurofibrillary tangles. We corrected for this using region of interest–specific z-scores based on the reference group. Amyloid and tau-PET uptake were associated throughout the brain after adjusting for age, with the highest correlations in the medial temporal regions.

Discussion

Regions with high-average SUVR are not necessarily those with the greatest tau pathology. Standardization is therefore recommended. Standardization of the data “realigns” the data such that the regional tau z-scores are informative of the disease process, that is, regions with high z-scores now coincide with regions correlated with amyloid deposition. Medial temporal structures, specifically entorhinal cortex–tau, may be useful as an AD-specific tau-PET signature due to its sensitivity to amyloid.

First PET Imaging Studies With 63Zn-Zinc Citrate in Healthy Human Participants and Patients With Alzheimer Disease

Abnormalities in zinc homeostasis are indicated in many human diseases, including Alzheimer disease (AD). ⁶³Zn-zinc citrate was developed as a positron emission tomography (PET) imaging probe of zinc transport and used in a first-in-human study in 6 healthy elderly individuals and 6 patients with clinically confirmed AD. Dynamic PET imaging of the brain was performed for 30 minutes following intravenous administration of ⁶³Zn-zinc citrate (∼330 MBq). Subsequently, body PET images were acquired. Urine and venous blood were analyzed to give information on urinary excretion and pharmacokinetics. Regional cerebral ⁶³Zn clearances were compared with ¹¹C-Pittsburgh Compound B (¹¹C-PiB) and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) imaging data. ⁶³Zn-zinc citrate was well tolerated in human participants with no adverse events monitored. Tissues of highest uptake were liver, pancreas, and kidney, with moderate uptake being seen in intestines, prostate (in males), thyroid, spleen, stomach, pituitary, and salivary glands. Moderate brain uptake was observed, and regional dependencies were observed in ⁶³Zn clearance kinetics in relationship with regions of high amyloid-β plaque burden (¹¹C-PiB) and ¹⁸F-FDG hypometabolism. In conclusion, zinc transport was successfully imaged in human participants using the PET probe ⁶³Zn-zinc citrate. Primary sites of uptake in the digestive system accent the role of zinc in gastrointestinal function. Preliminary information on zinc kinetics in patients with AD evidenced regional differences in clearance rates in correspondence with regional amyloid-β pathology, warranting further imaging studies of zinc homeostasis in patients with AD.

Optimizing PiB-PET SUVR change-over-time measurement by a large-scale analysis of longitudinal reliability, plausibility, separability, and correlation with MMSE

Quantitative measurements of change in β-amyloid load from Positron Emission Tomography (PET) images play a critical role in clinical trials and longitudinal observational studies of Alzheimer's disease. These measurements are strongly affected by methodological differences between implementations, including choice of reference region and use of partial volume correction, but there is a lack of consensus for an optimal method. Previous works have examined some relevant variables under varying criteria, but interactions between them prevent choosing a method via combined meta-analysis. In this work, we present a thorough comparison of methods to measure change in β-amyloid over time using Pittsburgh Compound B (PiB) PET imaging.

METHODS

We compare 1,024 different automated software pipeline implementations with varying methodological choices according to four quality metrics calculated over three-timepoint longitudinal trajectories of 129 subjects: reliability (straightness/variance); plausibility (lack of negative slopes); ability to predict accumulator/non-accumulator status from baseline value; and correlation between change in β-amyloid and change in Mini Mental State Exam (MMSE) scores.

RESULTS AND CONCLUSION

From this analysis, we show that an optimal longitudinal measure of β-amyloid from PiB should use a reference region that includes a combination of voxels in the supratentorial white matter and those in the whole cerebellum, measured using two-class partial volume correction in the voxel space of each subject's corresponding anatomical MR image.

Feasibility and diagnostic accuracy of exercise treadmill nitrogen-13 ammonia PET myocardial perfusion imaging of obese patients

BACKGROUND

Treadmill exercise nitrogen-13 ((13)N)-ammonia positron emission tomography (PET) has logistical challenges and limited literature. We aimed to assess its feasibility, image quality, and diagnostic accuracy in obese and nonobese patients.

METHODS AND RESULTS

Between 2009 and 2012, 10,804 patients were referred for myocardial perfusion imaging, including 300 for treadmill PET, of whom 265 were included in this study. Treadmill testing and PET were performed using standard procedures. Image quality, perfusion, and summed stress score (SSS) were assessed. Invasive coronary angiography was performed within 90 days of PET in 43 patients. Mean ± SD body mass index (BMI) was 35.7 ± 7.7 kg/m(2) (range 19.5-63.5 kg/m(2)). Feasibility of treadmill (13)N-ammonia PET was 100%. Exercise duration was less for obese patients than nonobese patients (P < .001). Image quality was rated good for 96.9% of obese and 100% of nonobese patients. For all patients, sensitivity was 86.4% and specificity was 74.4%. Diagnostic accuracy did not change significantly with increasing BMI. SSS remained significant in predicting angiographic coronary artery disease after adjustment for age, sex, and Duke treadmill score.

CONCLUSIONS

Treadmill (13)N-ammonia PET is highly feasible, yields good image quality, and has moderately high diagnostic accuracy in a small subset of obese and nonobese patients who are deemed able to perform treadmill exercise.

Future of thoracic PET scanning

The advances in PET scanning for thoracic diseases that are deemed most likely to have clinical impact in the near-term future are highlighted in this article. We predict that the current practice of medicine will continue to embrace the power of molecular imaging and specifically PET scanning. 18F-fluorodeoxyglucose-PET scanning will continue to evolve and will expand into imaging of inflammatory disorders. New clinically available PET scan radiotracers, such as PET scan versions of octreotide and amyloid imaging agents, will expand PET imaging into different disease processes. Major improvements in thoracic PET/CT imaging technology will become available, including fully digital silicone photomultipliers and Bayesian penalized likelihood image reconstruction. These will result in significant improvements in image quality, improving the evaluation of smaller lung nodules and metastases and allowing better prediction of prognosis. The birth of clinical PET/MRI scan will add new imaging opportunities, such as better PET imaging of pleural diseases currently obscured by complex patient motion.

Free fatty acid uptake in humans with CD36 deficiency

Animal models have demonstrated that CD36 facilitates cell membrane free fatty acid (FFA) transport, but its role in human metabolism is not well understood. We measured heart, liver, adipose (three depots), and muscle (truncal postural and thigh locomotive) FFA uptake using [(11)C]palmitate positron emission tomography (PET) scans in a family of five carrying the Pro90Ser CD36 mutation (2 homozygotes had no CD36) and matched control volunteers. PET scans were done under conditions of suppressed and slightly increased palmitate concentrations. During suppressed palmitate conditions, muscle and adipose palmitate uptake were markedly reduced in homozygotes but not heterozygotes for the Pro90Ser CD36 mutation, whereas when palmitate concentration was slightly increased, uptake in muscle and adipose did not differ between control subjects and homozygous family members. Hepatic FFA uptake was similar in all participants regardless of palmitate concentrations, whereas myocardial FFA uptake was diminished in the Pro90Ser homozygotes during both suppressed and increased palmitate conditions. We conclude that CD36 1) facilitates FFA transport into muscle and adipose tissue in humans when extracellular concentrations are reduced but not when they are modestly elevated, 2) is not rate limiting for hepatic FFA uptake, and 3) is needed for normal cardiac FFA uptake over a range of FFA concentrations from low to slightly elevated.

Micro-computed tomography and nuclear magnetic resonance imaging for noninvasive, live-mouse cholangiography

The cholangiopathies are a diverse group of biliary tract disorders, many of which lack effective treatment. Murine models are an important tool for studying their pathogenesis, but existing noninvasive methods for assessing biliary disease in vivo are not optimal. Here we report our experience with using micro-computed tomography (microCT) and nuclear magnetic resonance (MR) imaging to develop a technique for live-mouse cholangiography. Using mdr2 knockout (mdr2KO, a model for primary sclerosing cholangitis (PSC)), bile duct-ligated (BDL), and normal mice, we performed in vivo: (1) microCT on a Siemens Inveon PET/CT scanner and (2) MR on a Bruker Avance 16.4 T spectrometer, using Turbo Rapid Acquisition with Relaxation Enhancement, IntraGate Fast Low Angle Shot, and Half-Fourier Acquisition Single-shot Turbo Spin Echo methods. Anesthesia was with 1.5-2.5% isoflurane. Scans were performed with and without contrast agents (iodipamide meglumine (microCT), gadoxetate disodium (MR)). Dissection and liver histology were performed for validation. With microCT, only the gallbladder and extrahepatic bile ducts were visualized despite attempts to optimize timing, route, and dose of contrast. With MR, the gallbladder, extra-, and intrahepatic bile ducts were well-visualized in mdr2KO mice; the cholangiographic appearance was similar to that of PSC (eg, multifocal strictures) and could be improved with contrast administration. In BDL mice, MR revealed cholangiographically distinct progressive dilation of the biliary tree without ductal irregularity. In normal mice, MR allowed visualization of the gallbladder and extrahepatic ducts, but only marginal visualization of the diminutive intrahepatic ducts. One mouse died during microCT and MR imaging, respectively. Both microCT and MR scans could be obtained in ≤20 min. We, therefore, demonstrate that MR cholangiography can be a useful tool for longitudinal studies of the biliary tree in live mice, whereas microCT yields suboptimal duct visualization despite requiring contrast administration. These findings support further development and application of MR cholangiography to the study of mouse models of PSC and other cholangiopathies.

Effects of age on the glucose metabolic changes in mild cognitive impairment

BACKGROUND AND PURPOSE

Decreased glucose metabolism in the temporal and parietal lobes on FDG-PET is recognized as an early imaging marker for the AD pathology. Our objective was to investigate the effects of age on FDG-PET findings in aMCI.

MATERIALS AND METHODS

Twenty-five patients with aMCI at 55-86 years of age (median = 73 years) and 25 age- and sex-matched CN subjects underwent FDG-PET. SPM5 was used to compare the FDG uptake in patients in aMCI-old (>73 years) and aMCI-young (<or=73 years) groups with CN subjects. The findings in the aMCI-old patients were independently validated in a separate cohort of 10 aMCI and 13 CN subjects older than 73 years of age.

RESULTS

The pattern of decreased glucose metabolism and gray matter atrophy in the medial temporal, posterior cingulate, precuneus, lateral parietal, and temporal lobes in aMCI-young subjects was consistent with the typical pattern observed in AD. The pattern of glucose metabolic changes in aMCI-old subjects was different, predominantly involving the frontal lobes and the left parietal lobe. Gray matter atrophy in aMCI-old subjects was less pronounced than that in the aMCI-young subjects, involving the hippocampus and the basal forebrain in both hemispheres

CONCLUSIONS

Pathologic heterogeneity may be underlying the absence of AD-like glucose metabolic changes in older compared with younger patients with aMCI. This may be an important consideration for the clinical use of temporoparietal hypometabolism on FDG-PET as a marker for early diagnosis of AD in aMCI.

Comparison of 18F-FDG and PiB PET in cognitive impairment

The purpose of this study was to compare the diagnostic accuracy of glucose metabolism and amyloid deposition as demonstrated by (18)F-FDG and Pittsburg Compound B (PiB) PET to evaluate subjects with cognitive impairment.

METHODS

Subjects were selected from existing participants in the Mayo Alzheimer's Disease Research Center or Alzheimer's Disease Patient Registry programs. A total of 20 healthy controls and 17 amnestic mild cognitive impairment (aMCI), 6 nonamnestic mild cognitive impairment (naMCI), and 13 Alzheimer disease (AD) subjects were imaged with both PiB and (18)F-FDG PET between March 2006 and August 2007. Global measures for PiB and (18)F-FDG PET uptake, normalized to cerebellum for PiB and pons for (18)F-FDG, were compared. Partial-volume correction, standardized uptake value (SUV), and cortical ratio methods of image analysis were also evaluated in an attempt to optimize the analysis for each test.

RESULTS

Significant discrimination (P < 0.05) between controls and AD, naMCI and aMCI, naMCI and AD, and aMCI and AD by PiB PET measurements was observed. The paired groupwise comparisons of the global measures demonstrated that PiB PET versus (18)F-FDG PET showed similar significant group separation, with only PiB showing significant separation of naMCI and aMCI subjects.

CONCLUSION

PiB PET and (18)F-FDG PET have similar diagnostic accuracy in early cognitive impairment. However, significantly better group discrimination in naMCI and aMCI subjects by PiB, compared with (18)F-FDG, was seen and may suggest early amyloid deposition before cerebral metabolic disruption in this group.

Serial PIB and MRI in normal, mild cognitive impairment and Alzheimer's disease: implications for sequence of pathological events in Alzheimer's disease

The purpose of this study was to use serial imaging to gain insight into the sequence of pathologic events in Alzheimer's disease, and the clinical features associated with this sequence. We measured change in amyloid deposition over time using serial ¹¹C Pittsburgh compound B (PIB) positron emission tomography and progression of neurodegeneration using serial structural magnetic resonance imaging. We studied 21 healthy cognitively normal subjects, 32 with amnestic mild cognitive impairment and 8 with Alzheimer's disease. Subjects were drawn from two sources—ongoing longitudinal registries at Mayo Clinic, and the Alzheimer's disease Neuroimaging Initiative (ADNI). All subjects underwent clinical assessments, MRI and PIB studies at two time points, approximately one year apart. PIB retention was quantified in global cortical to cerebellar ratio units and brain atrophy in units of cm³ by measuring ventricular expansion. The annual change in global PIB retention did not differ by clinical group (P = 0.90), and although small (median 0.042 ratio units/year overall) was greater than zero among all subjects (P < 0.001). Ventricular expansion rates differed by clinical group (P < 0.001) and increased in the following order: cognitively normal (1.3 cm³/year) <  amnestic mild cognitive impairment (2.5 cm³/year) <  Alzheimer's disease (7.7 cm³/year). Among all subjects there was no correlation between PIB change and concurrent change on CDR-SB (r = −0.01, P = 0.97) but some evidence of a weak correlation with MMSE (r =−0.22, P = 0.09). In contrast, greater rates of ventricular expansion were clearly correlated with worsening concurrent change on CDR-SB (r = 0.42, P < 0.01) and MMSE (r =−0.52, P < 0.01). Our data are consistent with a model of typical late onset Alzheimer's disease that has two main features: (i) dissociation between the rate of amyloid deposition and the rate of neurodegeneration late in life, with amyloid deposition proceeding at a constant slow rate while neurodegeneration accelerates and (ii) clinical symptoms are coupled to neurodegeneration not amyloid deposition. Significant plaque deposition occurs prior to clinical decline. The presence of brain amyloidosis alone is not sufficient to produce cognitive decline, rather, the neurodegenerative component of Alzheimer's disease pathology is the direct substrate of cognitive impairment and the rate of cognitive decline is driven by the rate of neurodegeneration. Neurodegeneration (atrophy on MRI) both precedes and parallels cognitive decline. This model implies a complimentary role for MRI and PIB imaging in Alzheimer's disease, with each reflecting one of the major pathologies, amyloid dysmetabolism and neurodegeneration.

3D registration of micro-PET-CT for measurable correlates of dyspeptic symptoms in mice

Patients with chronic calorie insufficiency commonly suffer from upper gastrointestinal dysfunction and consequent dyspeptic symptoms, which may interfere with their nutritional rehabilitation. To investigate the relationship between gastric dysfunction and feeding behavior, we exposed mice to chronic caloric restriction and demonstrated gastric motor abnormalities in them. Gastric dysmotility is typically associated with dyspeptic symptoms but sensations cannot be directly assessed in animal models. Therefore, as an initial step toward establishing measurable correlates of postprandial symptoms in small animals, we have attempted to characterize central responses to food intake by positron emission tomography-computerized microtomography (PET-CT) in normal and calorically restricted mice. Animals consumed a standard test meal after an overnight fast before receiving 2-deoxy-2[¹⁸F]fluoro-D-glucose tracer. The same mice were also scanned in the fasting state on a separate day. We were able to bring the fed and fasting PET volume images into spatial registration with each other and with an MR-derived atlas of the mouse brain, so that the differences in uptake between the two states could be mapped quantitatively against the neuroanatomic regions of the atlas. Our approach is suitable for studying the effects of gastric dysmotilities on central responses to feeding.

11C PiB and structural MRI provide complementary information in imaging of Alzheimer's disease and amnestic mild cognitive impairment

To date, most diagnostic imaging comparisons between amyloid labelling ligands and other imaging modalities have been between the use of amyloid labelling ligand (11)C Pittsburgh Compound B (PiB) and FDG-PET. Our objectives were to compare cognitive performance and diagnostic group-wise discrimination between cognitively normal, amnestic mild cognitive impairment (MCI) and Alzheimer's disease subjects with MRI-based measures of hippocampal volume and PiB retention, and secondly to evaluate the topographic distribution of PiB retention and grey matter loss using 3D voxel-wise methods. Twenty cognitively normal, 17 amnestic MCI and 8 probable Alzheimer's disease subjects were imaged with both MRI and PiB. PiB retention was quantified as the ratio of uptake in cortical to cerebellar regions of interest (ROIs) 40-60 min post-injection. A global cortical PiB retention summary measure was derived from six cortical ROIs. Statistical parametric mapping (SPM) and voxel-based morphometry (VBM) were used to evaluate PiB retention and grey matter loss on a 3D voxel-wise basis. Alzheimer's disease subjects had high global cortical PiB retention and low hippocampal volume; most cognitively normal subjects had low PiB retention and high hippocampal volume; and on average amnestic MCI subjects were intermediate on both PiB and hippocampal volume. A target-to-cerebellar ratio of 1.5 was used to designate subjects with high or low PiB cortical retention. All Alzheimer's disease subjects fell above this ratio, as did 6 out of 20 cognitively normal subjects and 9 out of 17 MCI subjects, indicating bi-modal PiB retention in the latter two groups. Interestingly, we found no consistent differences in learning and memory performance between high versus low PiB cognitively normal or amnestic MCI subjects. The SPM/VBM voxel-wise comparisons of Alzheimer's disease versus cognitively normal subjects provided complementary information in that clear and meaningful similarities and differences in topographical distribution of amyloid deposition and grey matter loss were shown. The frontal lobes had high PiB retention with little grey matter loss, anteromedial temporal areas had low PiB retention with significant grey matter loss, whereas lateral temporoparietal association cortex displayed both significant PiB retention and grey matter loss. A voxel-wise SPM conjunction analysis revealed that subjects with high PiB retention shared a common PiB retention topographical pattern regardless of clinical category, and this matched that of amyloid plaque distribution from autopsy studies of Alzheimer's disease. Both global cortical PiB retention and hippocampal volumes demonstrated significant correlation in the expected direction with cognitive testing performance; however, correlations were stronger with MRI than PiB. Pair-wise inter-group diagnostic separation was significant for all group-wise pairs for both PiB and hippocampal volume with the exception of the comparison of cognitively normal versus amnestic MCI, which was not significant for PiB. PiB and MRI provided complementary information such that clinical diagnostic classification using both methods was superior to using either in isolation.

The relationships among serum lipid levels, adiposity, and depressive symptomatology in persons aging with spinal cord injury

BACKGROUND

Cardiovascular disease (CVD) appears to occur prematurely in persons with spinal cord injury (SCI). Stress may play a significant role in the development of CVD. Depression is the most common form of stress complicating the care of persons with SCI.

METHODS

In 188 persons with SCI, 46% with tetraplegia and 54% with paraplegia, the relationship between depression and the serum lipid profile was studied. Depression was measured by the Older Adult Health and Mood Questionnaire (OAHMQ) for persons with disability. Total cholesterol, high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol and triglycerides were measured; body mass index (BMI) was computed and percent body fat was determined by dual-energy x-ray absorptiometry (DXA).

RESULTS

Depression and level of SCI were found to have significant interactive effects on serum lipid levels. Serum total and LDL cholesterol, as well as triglycerides, were all higher among persons with paraplegia who were depressed compared to those who were not depressed. This was not found in persons with tetraplegia. Inverse relationships were evident between serum triglycerides and HDL cholesterol levels. Persons with paraplegia who were depressed had significantly more adiposity than those not depressed. BMI correlated directly with serum triglycerides and indirectly with serum HDL cholesterol.

CONCLUSION

Depression appears to be a strong determinant of adverse lipid profiles in patients with paraplegia. association between depression and adiposity in these patients compounds the risk for cardiovascular disease.

In vivo quantitation of intratumoral radioisotope uptake using micro-single photon emission computed tomography/computed tomography

PURPOSE

This study was undertaken to determine the ability of micro-single photon emission computed tomography (micro-SPECT)/computed tomography (CT) to accurately quantitate intratumoral radioisotope uptake in vivo and to compare these measurements with planar imaging and micro-SPECT imaging alone.

PROCEDURES

Human pancreatic cancer xenografts were established in 10 mice. Intratumoral radioisotope uptake was achieved via intratumoral injection of an attenuated measles virus vector expressing the NIS gene (MV-NIS). On various days after MV-NIS injection, (123)I planar and micro-SPECT/CT imaging was performed. Tumor activity was determined by dose calibrator measurements and region-of-interest (ROI) image analysis. Agreement and reproducibility of tumor activity measurements were assessed by Bland-Altman plots and Lin's concordance correlation coefficient (CCC).

RESULTS

Intratumoral radioisotope uptake was detected in all mice. Scatterplots demonstrate strong agreement (CCC = 0.93) between micro-SPECT/CT ROI image analysis and dose calibrator tumor activity measurements. The differences between dose calibrator activity measurements and those obtained with ROI image analysis of micro-SPECT alone and planar imaging are less accurate and more variable (CCC = 0.84 and 0.78, respectively).

CONCLUSIONS

Micro-SPECT/CT can be used to accurately quantify intratumoral radioisotope uptake in vivo and is more reliable than planar or micro-SPECT imaging alone.

Quality of life while aging with a disability

Being able to develop or maintain a positive, or high, quality of life (QOL) after a disability is one of the most important outcomes from rehabilitation. Negative, or low, QOL may also occur, especially when people return to the community. Furthermore, as people with disability age, many experience changes in their health and functioning that challenge their hard-won QOL. This article describes research on QOL among persons who are aging with a disability. Both positive and negative dimensions of QOL were studied. Being able to maintain community activities was significantly related to QOL. Current age and age at onset of disability played a nonsignificant role on negative QOL but were significantly related to positive QOL. Assistive technology can play a significant role in helping individuals who are aging with a disability to maintain valued activities and experiences.

Metabolic and endocrine changes in persons aging with spinal cord injury

Persons with spinal cord injury (SCI) have secondary medical disabilities that impair their ability to function. With paralysis, dramatic deleterious changes in body composition occur acutely with further adverse changes ensuing with increasing duration of injury. Lean mass, composed of skeletal muscle and bone, is lost and adiposity is relatively increased. The body composition changes may be further exacerbated by associated reductions in anabolic hormones, testosterone, and growth hormone. Individuals with SCI also have decreased levels of activity. These body composition and activity changes are associated with insulin resistance, disorders in carbohydrate and lipid metabolism, and may be associated with premature cardiovascular disease. Although limited information is available, upper body exercise and cycle ergometry of the lower extremities by functional electrical stimulation (FES) have been reported to have a salutary effect on these body composition and metabolic sequelae of paralysis. Perhaps other innovative, externally mediated forms of active exercise of the paralyzed extremities will result in an increased functional capacity, metabolic improvement, and reduction of atherosclerotic vascular disease.

Scatter and attenuation correction for brain SPECT using attenuation distributions inferred from a head atlas

Sequential transmission scanning (TS)/SPECT is impractical for neurologically impaired patients who are unable to keep their heads motionless for the extended duration of the combined scans. To provide an alternative to TS, we have developed a method of inferring-attenuation distributions (IADs), from SPECT data, using a head atlas and a registration program. The validity of replacing TS with IAD was tested in 10 patients with mild dementia.

METHODS

TS was conducted with each patient using a collimated 99mTc line source and fanbeam collimator; this was followed by hexamethyl propyleneamine oxime-SPECT. IAD was derived by deformably registering the brain component of a digital head atlas to a preliminary SPECT reconstruction and then applying the resulting spatial transformation to the full head atlas. SPECT data were reconstructed with scatter and attenuation correction. Relative regional cerebral blood flow was quantified in 12 threshold-guided anatomic regions of interest, with cerebellar normalization. SPECT reconstructions using IAD were compared with those using TS (which is the "gold standard") in terms of these regions of interest.

RESULTS

When we compared all regions of interest across the population, the correlation between IAD-guided and TS-guided SPECT scans was 0.92 (P < 0.0001), whereas the mean absolute difference between the scans was 7.5%. On average, IAD resulted in slight underestimation of relative regional cerebral blood flow; however, this underestimation was statistically significant for only the left frontal and left central sulcus regions (P = 0.001 and 0.002, respectively). Error analysis indicated that approximately 10.0% of the total error was caused by IAD scatter correction, 36.6% was caused by IAD attenuation correction, 27.0% was caused by discrepancies in region-of-interest demarcation from quantitative errors in IAD-guided reconstructions, and 26.5% was caused by patient motion throughout the imaging procedure.

CONCLUSION

SPECT reconstructions guided by IAD are sufficiently accurate to identify regional cerebral blood flow deficits of 10%, which are typical in moderate and advanced dementia.

Quality of life in assisted living homes: a multidimensional analysis

This study examined the impact of four domains upon the quality of life (QOL) of senior residents living in assisted living homes: (a) demographic characteristics and health status, (b) social involvement, (c) facility characteristics, and (d) the social climate. Participants were 201 residents with functional impairments living in 55 different assisted living facilities in California. QOL was measured with three scales of depression, life satisfaction, and facility satisfaction. Bivariate correlations and ANOVAs found significant relations between at least one of the QOL measures and age, health status, social and family involvement measures, facility characteristics, and social climate measures. Social climate measures of cohesion, conflict, and independence had the strongest zero-order correlations. Regression analyses for the three QOL measures found cohesion to be the strongest predictor in all three regressions. Other QOL predictors in the regression analyses were fewer health conditions, participation in social activities, monthly family contact, and an environment low in conflict. Findings suggest that assisted living homes can improve resident QOL by creating a cohesive social environment, and encouraging social participation and family involvement.

Is immobilization associated with an abnormal lipoprotein profile? Observations from a diverse cohort

OBJECTIVE

The potential effects of ethnicity, gender, and adiposity on the serum lipid profile in persons with spinal cord injury (SCI) were determined.

SUBJECTS

Subjects with SCI were recruited during their annual physical examination from Rancho Los Amigos Medical Center, Downey, California. Sedentary able-bodied controls were Bridge and Tunnel Officers of the Triboro Bridge and Tunnel Authority of the New York City metropolitan area.

METHODS

Serum lipid profiles were investigated in 320 subjects with SCI and compared to those obtained from 303 relatively sedentary able-bodied controls. Serum lipid studies were obtained in the fasting state. Data were collected between 1993 and 1996. All lipid determinations were performed by the same commercial laboratory.

MAIN OUTCOME MEASURES

The dependent variables were the values from the lipid profile analysis. The independent variables consisted of study group, gender, ethnic group, age, duration of injury, and anthropometric measurements.

RESULTS

The serum high-density lipoprotein cholesterol (HDL-c) level was reduced in the SCI compared with the control group (mean+/-SEM) (42+/-0.79 vs 47+/-0.67 mg/dl, P<0.0005). The serum HDL-c level was significantly lower in males with SCI than males in the control group (39+/-0.83 vs 45+/-0.70 mg/dl, P<0.0001), but not for females (51+/-1.54 vs 54 1.52 mg/dl, n.s.). Within the subgroups for whites and Latinos, HDL-c values were also lower in subjects with SCI than in controls (whites: 41+/-1.02 vs 46+/-0.86 mg/dl, P<0.0001; Latinos: 37+/-1.53 vs 42+/-1.59 mg/dl, P<0.05), but not for African Americans (49+/-1.56 vs 51+/-1.27 mg/dl, n.s.). African Americans had higher HDL-c values than whites or Latinos (SCI: 49+/-1.56 vs 41+/-1.02 or 37+/-1.53 mg/dl, P< 0.0001; controls: 51+/-1.27 vs 46+/-0.86 mg/dl, P<0.01 or 42+/-1.59 mg/dl, P<0.0005). In persons with SCI, the serum HDL-c values were inversely related to body mass index and estimated per cent body fat (r=0.27, P<0.0001).

CONCLUSION

In white and Latino males, but not in females or African Americans, immobilization from SCI appears to be associated with lower HDL-c values than in controls.

Depression and life satisfaction among people ageing with post-polio and spinal cord injury

PURPOSE AND BACKGROUND

Attention has recently begun to focus on the ageing of individuals with disability, not only as a long-term follow-up issue but as a unique developmental issue itself. The majority of individuals with an onset of disability before age 30 can now expect to live into their 60s, 70s and beyond. Most of the secondary medical conditions that foreshortened life expectancy have been controlled and improved rehabilitation techniques have evolved over the last 50 years. The average age of persons with post-polio in the United States is over 50 and the average age of persons with spinal cord injury is in the late 40s. New medical, functional and psychosocial problems have been discovered among persons ageing with these and other disabilities. Most of these problems lack sufficient scientific explanation, and therefore, clinical interventions. Quality of life (QOL) issues become involved as these changes occur. From a psychological perspective, QOL can be either positive, as reflected in high life satisfaction, or negative, as reflected in distress and depression.

METHODS

This study reports on life satisfaction and depression in 360 persons, 121 with post-polio, 177 with SCI and 62 non-disabled age-matched comparisons. The Geriatric Depression Scale and the Older Adult Health and Mood Questionnaire assess depressive symptomatology and a 10-item life satisfaction scale with four-point ratings on each item used.

RESULTS

Life satisfaction varied by the group, with the non-disabled group higher than one or both of the other two groups on all scales and the post-polio group higher than the SCI group on six scales. Satisfaction with health, finances, work and overall life were most different. 22% of the post-polio group, 41% of the SCI group and 15% of the non-disabled group had at least significant repressive symptomatology.

CONCLUSION

The results for each group are discussed in terms of their relation to other coping variables that were assessed, particularly social support and coping methods.

The relative contributions of scatter and attenuation corrections toward improved brain SPECT quantification

Mounting evidence indicates that scatter and attenuation are major confounds to objective diagnosis of brain disease by quantitative SPECT. There is considerable debate, however, as to the relative importance of scatter correction (SC) and attenuation correction (AC), and how they should be implemented. The efficacy of SC and AC for 99mTc brain SPECT was evaluated using a two-compartment fully tissue-equivalent anthropomorphic head phantom. Four correction schemes were implemented: uniform broad-beam AC, non-uniform broad-beam AC, uniform SC + AC, and non-uniform SC + AC. SC was based on non-stationary deconvolution scatter subtraction, modified to incorporate a priori knowledge of either the head contour (uniform SC) or transmission map (non-uniform SC). The quantitative accuracy of the correction schemes was evaluated in terms of contrast recovery, relative quantification (cortical:cerebellar activity), uniformity ((coefficient of variation of 230 macro-voxels) x 100%), and bias (relative to a calibration scan). Our results were: uniform broad-beam (mu = 0.12 cm(-1)) AC (the most popular correction): 71% contrast recovery, 112% relative quantification, 7.0% uniformity, +23% bias. Non-uniform broad-beam (soft tissue mu = 0.12 cm(-1)) AC: 73%, 114%, 6.0%, +21%, respectively. Uniform SC + AC: 90%, 99%, 4.9%, +12%, respectively. Non-uniform SC + AC: 93%, 101%, 4.0%, +10%, respectively. SC and AC achieved the best quantification; however, non-uniform corrections produce only small improvements over their uniform counterparts. SC + AC was found to be superior to AC; this advantage is distinct and consistent across all four quantification indices.

Importance of bone attenuation in brain SPECT quantification

The purpose of this study was to determine the effects of nonuniform attenuation on relative quantification in brain SPECT and to compare the ability of the Chang and Sorenson uniform attenuation corrections (UACs) to achieve volumetric relative quantification.

METHODS

Three head phantoms (dry human skull, Rando and Radiology Support Devices (RSD) phantoms) were compared with a human head using a gamma camera transmission CT (gammaTCT) SPECT system and x-ray CT. Subsequently, the RSD phantom's brain reservoir was filled with a uniform water solution of 99mTc, and SPECT and gammaTCT data were acquired using fanbeam collimation. The attenuating effects of bone, scalp and head-holder in individual projections were determined by an analytical projection technique using the SPECT and gammaTCT reconstructions. The Chang UAC used brain and head contours that were segmented from the gammaTCT reconstruction to demarcate its attenuation map, whereas the Sorenson UAC fit slice-specific ellipses to the SPECT projection data. For each UAC, volumetric relative quantification was measured with varying attenuation coefficients (mus) of the attenuation map.

RESULTS

Gamma camera transmission CT and x-ray CT scans showed that the dry skull and Rando phantoms suffered from a dried trabecular bone compartment. The RSD phantom most closely reproduced the attenuation coefficients of the human gammaTCT and x-ray CT scans. The analytical projections showed that the attenuating effects of bone, scalp and head-holder were nonuniform across the projections and accounted for 18%-37% of the total count loss. Volumetric relative quantification was best achieved with the Chang (zero iterations) attenuation correction using the head contour and mu = 0.075 cm(-1); however, cortical activity was found to be 10% higher than cerebellar activity. For all UACs, the optimal choices of mu were experimentally found to be lower than the recommended 0.12 cm(-1) for brain tissue. This result is theoretically supported here.

CONCLUSION

The magnitude of errors resulting from uniform attenuation corrections can be greater than the magnitudes of regional cerebral blood flow deficits in patients with dementia, as compared with normal controls. This suggests that nonuniform attenuation correction in brain SPECT imaging must be applied to accurately estimate regional cerebral blood flow.

The effect of residual neurological deficit on serum lipoproteins in individuals with chronic spinal cord injury

Subjects with spinal cord injury (SCI) have been shown to have an adverse lipid profile. Prior studies performed with smaller numbers of subjects have not been able to demonstrate any relationship between the level and degree of the neurological deficit and plasma lipid levels. Over a 2 year period we investigated the lipid profiles in 541 subjects from Rancho Los Amigos Medical Center, Downey, California. Subjects were grouped by tetraplegia (Tetra; n = 247) or paraplegia (Para; n = 294) and by subgroup for degree of neurological deficit: complete Tetra (n = 156), incomplete Tetra (n = 91), complete Para (n = 206) and incomplete Para (n = 88). The serum high-density lipoprotein (HDL) cholesterol level was lower in the Tetra than in the Para group (38 +/- 0.7 vs 45 +/- 0.8, P < 0.01). The group with Tetra had a higher percentage of subjects with serum HDL cholesterol values < 35 mg/dL [an independent risk factor for coronary heart disease (CHD)] than those with Para (38% vs 21%, P < 0.0001). A significant inverse relationship was found for degree of neurological deficit and mean serum HDL cholesterol level (r = 0.19, P < 0.001), with the greater the deficit, the lower the serum HDL cholesterol level. Serum total cholesterol levels were higher in the Para group than in the Tetra group (198 +/- 2.6 vs 184 +/- 2.6, P < 0.01). However, the ratio of total cholesterol to HDL cholesterol (a discriminator of risk for CHD) was significantly lower in the Para group than the Tetra group (4.8 vs 5.2%, P < 0.01). Thus, in persons with SCI a spectrum of depressed serum HDL cholesterol levels and increased cardiovascular risk occur, with the most adverse lipid changes correlating with the severity of neurological deficit.

Multicenter trial validation of a camera-based method to measure Tc-99m mercaptoacetyltriglycine, or Tc-99m MAG3, clearance

PURPOSE

To evaluate an improved camera-based method for calculating the clearance of technetium-99m mercaptoacetyltriglycine (MAG3) in a multicenter trial.

MATERIALS AND METHODS

Tc-99m MAG3 scintigraphy was performed in 49 patients at three sites in the United States and Canada. The percentage of the injected dose of Tc-99m MAG3 in the kidney at 1-2, 1.0-2.5, and 2-3 minutes after injection was correlated with the plasma-based Tc-99m MAG3 clearances. The data were combined with the results obtained in 20 additional patients in a previously published pilot study.

RESULTS

Regression models correlating the plasma-based Tc-99m MAG3 clearance with the percentage uptake in the kidney for each time interval were developed; there was no statistically significant difference among sites in the regression equations. Correction for body surface area statistically significantly (P < .005) improved the correlation coefficient for each time interval. For the 1.0-2.5-minute interval, the body surface area-corrected correlation coefficient for the four combined sites was .87, and it improved to .93 when one outlier was omitted from the analysis. Similar results were obtained with the other time intervals. Independent processing by two observers showed no clinically important differences in the percentage dose in the kidney or in relative function.

CONCLUSION

An improved camera-based method to calculate the clearance of Tc-99m MAG3 was validated in a multicenter trial.

Depression and life satisfaction in aging polio survivors versus age-matched controls: relation to postpolio syndrome, family functioning, and attitude toward disability

OBJECTIVE

To compare depressive symptoms and life satisfaction in aging polio survivors with age-matched controls and to relate these outcomes to scores to psychosocial and disability-related variables.

DESIGN

A planned medical, functional, and psychosocial study with multivariate analyses.

SETTING

A large, urban rehabilitation center.

PARTICIPANTS

A volunteer sample of 121 polio survivors and an age-matched control group of 60 people with similar sociodemographic backgrounds.

MAIN OUTCOMES

Depression as measured by the Geriatric Depression Scale and an 11-item life satisfaction scale.

RESULTS

The prevalence of depressive disorders was not significantly different in the two groups, although the postpolio group tended to have more symptomatology and an overall depressive disorder prevalence of 28%. Some life satisfaction scale scores were significantly lower in the postpolio group, especially those concerned with health. People with postpolio syndrome scored significantly higher on depression scales and lower on some life satisfaction scales than people with a history of polio but without postpolio syndrome. Several psychosocial variables, most notably family functioning and attitude toward disability, helped to mediate this effect. Among people with significant depression, there was little, evidence of adequate treatment in the community.

CONCLUSIONS

Postpolio by itself does not relate to higher depression scores or lower life satisfaction. Postpolio syndrome has some relation to depression, but family functioning and attitude toward disability are more important. There is a need for better community-based psychological services.

The Older Adult Health and Mood Questionnaire: a measure of geriatric depressive disorder

Depressive disorders are a common problem in late life, requiring consistent and reliable screening by clinicians. Such screening should be based upon the most recent criteria available to facilitate diagnostic and nosologic agreement. This study presents a new screening instrument for geriatric depressive disorders based upon DSM-III-R criteria and the known differences in the display of depression that occur among older persons. The Older Adult Health and Mood Questionnaire (OAHMQ) is a 22-item questionnaire with sound psychometric properties and high validity. Its validation included comparisons with diagnostic assessments by geriatrically-trained psychiatrists and psychologists, and factor analysis. Using a three-part division of "normal," "clinically significant depressive symptoms," and "probable major depression," its sensitivity is .80 and its specificity is .87 for major depression, and .92 and .87, respectively, for any depressive disorder. Separate scoring of affective symptoms versus other symptoms of depression (i.e., physiologic, cognitive, or behavioral) can be useful for diagnostic and research purposes.

The geometric modulation transfer function of a transmission imaging system that uses a SPECT scintillation camera and parallel hole collimation

An analytic expression has been derived to calculate the geometric modulation transfer function of a transmission imaging system that uses parallel hole collimation for both the source and the SPECT camera. This expression describes the resolution of the transmission imaging system and replaces the need to use computer intensive Monte Carlo simulations for the system design. The geometric modulation transfer function, denoted as MTFg(rho) = [A2sc(Ssc rho)**A2cc(Scc rho)]D(rho), where ** denotes two-dimensional convolution; Asc(rho) and Acc(rho) are the Fourier transforms (FT) of the aperture functions for the parallel hole source collimator (SC) and the camera collimator (CC) holes, respectively; D(rho) is the FT of the camera response; and ssc and scc are scaling constants that depend on the respective collimator dimensions, the system dimensions, the object distance above camera collimator and whether MTFg(rho) is calculated for the object or image plane. The theoretical MTFg(rho) was verified with Monte Carlo simulations and experimental results. The formalism shows that the system resolution is characterized by the camera resolution and a combination of the resolutions of the source and camera collimators. This expression can be used to optimize the design of transmission imaging systems to be used in nuclear medicine.