Clinical evaluation of PET image reconstruction using a spatial resolution model

Purpose

PET image resolution is variable across the measured field-of-view and described by the point spread function (PSF). When accounting for the PSF during PET image reconstruction image resolution is improved and partial volume effects are reduced. Here, we evaluate the effect of PSF-based reconstruction on lesion quantification in routine clinical whole-body (WB) PET/CT imaging.

Materials and methods

41 oncology patients were referred for a WB-PET/CT examination (Biograph 40 TruePoint). Emission data were acquired at 2.5 min/bed at 1 h pi of 400 MBq [18F]-FDG. Attenuation-corrected PET images were reconstructed on 336 × 336-matrices using: (R1) standard AW-OSEM (4 iter, 8 subsets, 4 mm Gaussian) and (R2) AW-OSEM with PSF (3 iter, 21 subsets, 2 mm). Blinded and randomised reading of R1- and R2-PET images was performed. Individual lesions were located and counted independently on both sets of images. The relative change in PET quantification (SUV_max, SUV_mean, volume) of lesions seen on R1 and R2 is reported as (R2 − R1)/R1. Furthermore, SUV_max and SUV_mean was measured for a 3 cm spherical norm region in the right lobe of the healthy liver for R1 and R2.

Results

Clinical reading revealed 91 and 103 positive lesions for R1 and R2, respectively. For all lesions SUV_max (R2) was higher than SUV_max (R1). Regression analysis indicated that the relative increase in SUV_max (and SUV_mean) decreased with lesion size, whilst it increased with increasing radial distance from the centre of the field of view (FOV). There was no significant difference in SUV_mean in homogenous liver tissue between R1 and R2.

Conclusion

In whole-body FDG-PET/CT using routine clinical protocols, PSF-based PET reconstruction increases lesion detection and affects SUV_max measurements compared to standard AW-OSEM PET reconstruction.     

Intraindividual variability in neurocognitive performance is associated with time-based prospective memory in older adults

Introduction: Older adults demonstrate poorer prospective memory (PM) performance than younger adults, particularly for time-based cues and other strategically demanding PM tasks. Intraindividual variability (IIV) in neurocognitive test performance is an index of cognitive control that may be related to the execution of strategically demanding PM tasks. Method: Participants included 194 older Australian adults (age 50 to 88 years) who completed the Memory for Intentions Screening Test (MIST), the Prospective and Retrospective Memory Questionnaire (PRMQ), and clinical measures of executive functions. A measure of naturalistic time-based PM was also administered, in which participants were asked to call the examiner 24 hours after their appointment to report how many hours they slept. IIV was calculated as the mean-adjusted coefficient of variation (CoV) across subtests of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Results: IIV was significantly associated with time-based PM in the laboratory, independent of demographics. Additionally, IIV significantly predicted performance on a naturalistic time-based PM trial, independent of demographics and chronic medical conditions. IIV was not related to event-based laboratory PM or self-reported PM symptoms in daily life. Clinical measures of executive functions were similarly associated with time-based PM and the naturalistic PM task, but not with event-based PM or subjective PM symptoms.Conclusions: These results indicate that cognitive control, as indexed by IIV in neurocognitive performance, may play a role in naturalistic PM, as well as in highly strategic, but not automatic, laboratory-based PM among older adults.     

Optimal management strategies for placenta accreta

Objective  To determine which interventions for managing placenta accreta were associated with reduced maternal morbidity.
Design  Retrospective cohort study.
Setting  Two tertiary care teaching hospitals in Utah.
Population  All identified cases of placenta accreta from 1996 to 2008.
Methods  Cases of placenta accreta were identified using standard ICD-9 codes for placenta accreta, placenta praevia, and caesarean hysterectomy. Medical records were then abstracted for maternal medical history, hospital course, and maternal and neonatal outcomes. Maternal and neonatal complications were compared according to antenatal suspicion of accreta, indications for delivery, preoperative preparation, attempts at placental removal before hysterectomy, and hypogastric artery ligation.
Main outcome measures  Early morbidity (prolonged maternal intensive care unit admission, large volume of blood transfusion, coagulopathy, ureteral injury, or early re-operation) and late morbidity (intra-abdominal infection, hospital re-admission, or need for delayed re-operation).
Results  Seventy-six cases of placenta accreta were identified. When accreta was suspected, scheduled caesarean hysterectomy without attempting placental removal was associated with a significantly reduced rate of early morbidity compared with cases in which placental removal was attempted (67 versus 36%, P = 0.038). Women with preoperative bilateral ureteric stents had a lower incidence of early morbidity compared with women without stents (18 versus 55%, P = 0.018). Hypogastric artery ligation did not reduce maternal morbidity.
Conclusions  Scheduled caesarean hysterectomy with preoperative ureteric stent placement and avoiding attempted placental removal are associated with reduced maternal morbidity in women with suspected placenta accreta.     

Truncated NF2 proteins are not detected in meningiomas and schwannomas

Neurofibromatosis type 2 is caused by mutations in the NF2 tumor suppressor gene. The NF2 gene encodes a 595‐aminoacid protein, presumably functioning as a membrane‐organizing element. Theoretically, the majority of mutations found in the NF2 gene should lead to a truncated protein product. Using immunoprecipitation with an antibody raised to N‐terminal sequences of the NF2 protein, the authors sought to demonstrate the presence of truncated NF2 proteins in tumors. From 17 of 19 tumors (14 meningiomas and five schwannomas), 12 of which have previously been shown to harbor truncating NF2 mutations, wild‐type NF2 protein was immunopreci‐pitated. From two tumors no protein was precipitated. Truncated NF2 proteins were not observed. The authors conclude that mutant NF2 proteins are unstable and undergo accelerated degradation.     

Improvement in behavioural symptoms in patients with moderate to severe Alzheimer's disease by memantine: a pooled data analysis

INTRODUCTION: Behavioural disturbances are a common and distressing aspect of Alzheimer's disease (AD). This pooled analysis evaluated the specific benefits of memantine on behavioural disturbances in patients with moderate to severe AD. METHODS: Data were pooled from six 24/28-week, randomised, placebo-controlled, double-blind studies. Of the 2,311 patients included in these studies, 1,826 patients with moderate to severe AD (MMSE <20) were included in this analysis, corresponding to the extended indication for memantine in Europe. In this subgroup, 959 patients received memantine 20 mg/day and 867 received placebo. Behavioural symptoms were rated using the Neuropsychiatric Inventory (NPI) total and single-item scores at weeks 12 and 24/28. RESULTS: At weeks 12 and 24/28, ITT analysis demonstrated that memantine treatment produced statistically significant benefits over placebo treatment in NPI total score (p=0.001 and p=0.008), and in NPI single items: delusions (p=0.007 week 12, p=0.001 week 24/28), hallucinations (p=0.037 week 12), agitation/aggression (p=0.001 week 12, p=0.001 week 24/28), and irritability/lability (p=0.005 week 24/28), LOCF population. Analysis of the patients without symptoms at baseline indicated reduced emergence of agitation/aggression (p=0.002), delusions (p=0.047), and disinhibition (p=0.011), at week 12, and of agitation/aggression (p=0.002), irritability/lability (p=0.004), and night-time behaviour (p=0.050) at week 24/28 in those receiving memantine. OC analyses yielded similar results. CONCLUSIONS: The data suggest that memantine is effective in treating and preventing the behavioural symptoms of moderate to severe AD. Specific persistent benefits were observed on the symptoms of delusions and agitation/aggression, which are known to be associated with rapid disease progression, increased caregiver burden, early institutionalisation, and increased costs of care.     

Intriguing issues of EGFR targeting in head and neck cancer

We have read the recent comprehensive review by Cruz et al.[1] regarding the targeting of receptor tyrosine kinases andtheir therapeutic perspectives in head and neck squamous cellcarcinomas (HNSCC). The major focus of this report was epidermalgrowth factor receptor (EGFR) biology and targeting. However,we feel