Association between retinal thickness and β-amyloid brain accumulation in individuals with subjective cognitive decline: Fundació ACE Healthy Brain Initiative

Background

Optical coherence tomography (OCT) of the retina is a fast and easily accessible tool for the quantification of retinal structural measurements. Multiple studies show that patients with Alzheimer’s disease (AD) exhibit thinning in several retinal layers compared to age-matched controls. Subjective cognitive decline (SCD) has been proposed as a risk factor for progression to AD. There is little data about retinal changes in preclinical AD and their correlation with amyloid-β (Aβ) uptake.

Aims

We investigated the association of retinal thickness quantified by OCT with Aβ accumulation and conversion to mild cognitive impairment (MCI) over 24 months in individuals with SCD.

Methods

One hundred twenty-nine individuals with SCD enrolled in Fundació ACE Healthy Brain Initiative underwent comprehensive neuropsychological testing, OCT scan of the retina and florbetaben (FBB) positron emission tomography (PET) at baseline (v0) and after 24 months (v2). We assessed the association of sixteen retinal thickness measurements at baseline with FBB-PET status (+/−) and global standardize uptake value ratio (SUVR) as a continuous measure at v0 and v2 and their predictive value on clinical status change (conversion to mild cognitive impairment (MCI)) at v2.

Results

Mean age of the sample was 64.72 ± 7.27 years; 62.8% were females. Fifteen participants were classified as FBB-PET+ at baseline and 22 at v2. Every 1 μm of increased thickness in the inner nasal macular region conferred 8% and 6% higher probability of presenting a FBB-PET+ status at v0 (OR = 1.08, 95% CI = 1.02–1.14, p = 0.007) and v2 (OR = 1.06, 95% CI = 1.02–1.11, p = 0.004), respectively. Inner nasal macular thickness also positively correlated with global SUVR (at v0: β = 0.23, p = 0.004; at v2: β = 0.26, p = 0.001). No retinal measurements were associated to conversion to MCI over 24 months.

Conclusions

Subtle retinal thickness changes in the macular region are already present in SCD and correlate with Aβ uptake.

Clinical applicability of diagnostic biomarkers in early-onset cognitive impairment

BACKGROUND AND PURPOSE

Several diagnostic biomarkers are currently available for clinical use in early-onset cognitive impairment. The decision on which biomarker is used in each patient depends on several factors such as its predictive value or tolerability.

METHODS

There were a total of 40 subjects with early-onset cognitive complaints (<65 years of age): 26 with Alzheimer's disease (AD), five with frontotemporal dementia and nine with diagnostic suspicion of non-neurodegenerative disorder. Clinical and neuropsychological evaluation, lumbar puncture for cerebrospinal fluid (CSF) AD core biochemical marker determination, medial temporal atrophy evaluation on magnetic resonance imaging, amyloid-positron emission tomography (PET) and ¹⁸ F-fluorodeoxyglucose-PET were performed. Neurologists provided pre- and post-biomarker diagnosis, together with diagnostic confidence and clinical/therapeutic management. Patients scored the tolerability of each procedure.

RESULTS

Cerebrospinal fluid biomarkers and amyloid-PET increased diagnostic confidence in AD (77.4%-86.2% after CSF, 92.4% after amyloid-PET, P < 0.01) and non-neurodegenerative conditions (53.6%-75% after CSF, 95% after amyloid-PET, P < 0.05). Biomarker results led to diagnostic (32.5%) and treatment (32.5%) changes. All tests were well tolerated.

CONCLUSIONS

Biomarker procedures are well tolerated and have an important diagnostic/therapeutic impact on early-onset cognitive impairment.

Centiloid cut-off values for optimal agreement between PET and CSF core AD biomarkers

BACKGROUND

The Centiloid scale has been developed to standardize measurements of amyloid PET imaging. Reference cut-off values of this continuous measurement enable the consistent operationalization of decision-making for multicentre research studies and clinical trials. In this study, we aimed at deriving reference Centiloid thresholds that maximize the agreement against core Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers in two large independent cohorts.

METHODS

A total of 516 participants of the ALFA+ Study (N = 205) and ADNI (N = 311) underwent amyloid PET imaging ([18F]flutemetamol and [18F]florbetapir, respectively) and core AD CSF biomarker determination using Elecsys® tests. Tracer uptake was quantified in Centiloid units (CL). Optimal Centiloid cut-offs were sought that maximize the agreement between PET and dichotomous determinations based on CSF levels of Aβ42, tTau, pTau, and their ratios, using pre-established reference cut-off values. To this end, a receiver operating characteristic analysis (ROC) was conducted, and Centiloid cut-offs were calculated as those that maximized the Youden's J Index or the overall percentage agreement recorded.

RESULTS

All Centiloid cut-offs fell within the range of 25-35, except for CSF Aβ42 that rendered an optimal cut-off value of 12 CL. As expected, the agreement of tau/Aβ42 ratios was higher than that of CSF Aβ42. Centiloid cut-off robustness was confirmed even when established in an independent cohort and against variations of CSF cut-offs.

CONCLUSIONS

A cut-off of 12 CL matches previously reported values derived against postmortem measures of AD neuropathology. Together with these previous findings, our results flag two relevant inflection points that would serve as boundary of different stages of amyloid pathology: one around 12 CL that marks the transition from the absence of pathology to subtle pathology and another one around 30 CL indicating the presence of established pathology. The derivation of robust and generalizable cut-offs for core AD biomarkers requires cohorts with adequate representation of intermediate levels.

TRIAL REGISTRATION

ALFA+ Study, NCT02485730 ALFA PET Sub-study, NCT02685969.

Correlations between plasma and PET beta-amyloid levels in individuals with subjective cognitive decline: the Fundació ACE Healthy Brain Initiative (FACEHBI)

BACKGROUND

Peripheral biomarkers that identify individuals at risk of developing Alzheimer's disease (AD) or predicting high amyloid beta (Aβ) brain burden would be highly valuable. To facilitate clinical trials of disease-modifying therapies, plasma concentrations of Aβ species are good candidates for peripheral AD biomarkers, but studies to date have generated conflicting results.

METHODS

The Fundació ACE Healthy Brain Initiative (FACEHBI) study uses a convenience sample of 200 individuals diagnosed with subjective cognitive decline (SCD) at the Fundació ACE (Barcelona, Spain) who underwent amyloid florbetaben(18F) (FBB) positron emission tomography (PET) brain imaging. Baseline plasma samples from FACEHBI subjects (aged 65.9 ± 7.2 years) were analyzed using the ABtest (Araclon Biotech). This test directly determines the free plasma (FP) and total plasma (TP) levels of Aβ40 and Aβ42 peptides. The association between Aβ40 and Aβ42 plasma levels and FBB-PET global standardized uptake value ratio (SUVR) was determined using correlations and linear regression-based methods. The effect of the APOE genotype on plasma Aβ levels and FBB-PET was also assessed. Finally, various models including different combinations of demographics, genetics, and Aβ plasma levels were constructed using logistic regression and area under the receiver operating characteristic curve (AUROC) analyses to evaluate their ability for discriminating which subjects presented brain amyloidosis.

RESULTS

FBB-PET global SUVR correlated weakly but significantly with Aβ42/40 plasma ratios. For TP42/40, this observation persisted after controlling for age and APOE ε4 allele carrier status (R2 = 0.193, p = 1.01E-09). The ROC curve demonstrated that plasma Aβ measurements are not superior to APOE and age in combination in predicting brain amyloidosis. It is noteworthy that using a simple preselection tool (the TP42/40 ratio with an empirical cut-off value of 0.08) optimizes the sensitivity and reduces the number of individuals subjected to Aβ FBB-PET scanners to 52.8%. No significant dependency was observed between APOE genotype and plasma Aβ measurements (p value for interaction = 0.105).

CONCLUSION

Brain and plasma Aβ levels are partially correlated in individuals diagnosed with SCD. Aβ plasma measurements, particularly the TP42/40 ratio, could generate a new recruitment strategy independent of the APOE genotype that would improve identification of SCD subjects with brain amyloidosis and reduce the rate of screening failures in preclinical AD studies. Independent replication of these findings is warranted.

FACEHBI: A Prospective Study of Risk Factors, Biomarkers and Cognition in a Cohort of Individuals with Subjective Cognitive Decline. Study Rationale and Research Protocols

BACKGROUND

Long-term longitudinal studies with multimodal biomarkers are needed to delve into the knowledge of preclinical AD. Subjective cognitive decline has been proposed as a risk factor for the development of cognitive impairment. Thus, including individuals with SCD in observational studies may be a cost-effective strategy to increase the prevalence of preclinical AD in the sample.

OBJECTIVES

To describe the rationale, research protocols and baseline characteristics of participants in the Fundació ACE Healthy Brain Initiative (FACEHBI).

DESIGN

FACEHBI is a clinical trial (EudraCT: 2014-000798-38) embedded within a long-term observational study of individuals with SCD.

SETTING

Participants have been recruited at the memory clinic of Fundació ACE (Barcelona) from two different sources: patients referred by a general practitioner and individuals from an Open House Initiative.

PARTICIPANTS

200 individuals diagnosed with SCD with a strictly normal performance in a comprehensive neuropsychological battery.

MEASUREMENTS

Individuals will undergo an extensive neuropsychological protocol, risk factor assessment and a set of multimodal biomarkers including florbetaben PET, structural and functional MRI, diffusion tensor imaging, determination of amyloid species in plasma and neurophthalmologic assessment with optical coherence tomography.

RESULTS

Two hundred individuals have been recruited in 15 months. Mean age was 65.9 years; mean MMSE was 29.2 with a mean of 14.8 years of education.

CONCLUSIONS

FACEHBI is a long-term study of cognition, biomarkers and lifestyle that has been designed upon an innovative symptom-based approach using SCD as target population. It will shed light on the pathophysiology of preclinical AD and the role of SCD as a risk marker for the development of cognitive impairment.

PISCOM: a new procedure for epilepsy combining ictal SPECT and interictal PET

PURPOSE

We present a modified version of the SISCOM procedure that uses interictal PET instead of interictal SPECT for seizure onset zone localization. We called this new nuclear imaging processing technique PISCOM (PET interictal subtracted ictal SPECT coregistered with MRI).

METHODS

We retrospectively studied 23 patients (age range 4-61 years) with medically refractory epilepsy who had undergone MRI, ictal SPECT, interictal SPECT and interictal FDG PET and who had been seizure-free for at least 2 years after surgical treatment. FDG PET images were reprocessed (rFDG PET) to assimilate SPECT features for image subtraction. Interictal SPECT and rFDG PET were compared using statistical parametric mapping (SPM). PISCOM and SISCOM images were evaluated visually and using an automated volume of interest-based analysis. The results of the two studies were compared with each other and with the known surgical resection site.

RESULTS

SPM showed no significant differences in cortical activity between SPECT and rFDG PET images. PISCOM and SISCOM showed equivalent results in 17 of 23 patients (74%). The seizure onset zone was successfully identified in 19 patients (83%) by PISCOM and in 17 (74%) by SISCOM: in 15 patients (65%) the two techniques showed concordant successful results. The volume of interest-based analysis showed no significant differences between PISCOM and SISCOM in identifying the extension of the seizure onset zone. However, PISCOM showed a lower amount of indeterminate activity due to propagation, background or artefacts.

CONCLUSION

Preliminary findings of this initial proof-of-concept study suggest that perfusion and glucose metabolism in the cerebral cortex can be correlated and that PISCOM may be a valid technique for identification of the seizure onset zone. However, further studies are needed to validate these results.

Optimization of the reconstruction parameters in [123I]FP-CIT SPECT

The aim of this work was to obtain a set of parameters to be applied in [¹²³I]FP-CIT SPECT reconstruction in order to minimize the error between standardized and true values of the specific uptake ratio (SUR) in dopaminergic neurotransmission SPECT studies. To this end, Monte Carlo simulation was used to generate a database of 1380 projection data-sets from 23 subjects, including normal cases and a variety of pathologies. Studies were reconstructed using filtered back projection (FBP) with attenuation correction and ordered subset expectation maximization (OSEM) with correction for different degradations (attenuation, scatter and PSF). Reconstruction parameters to be optimized were the cut-off frequency of a 2D Butterworth pre-filter in FBP, and the number of iterations and the full width at Half maximum of a 3D Gaussian post-filter in OSEM. Reconstructed images were quantified using regions of interest (ROIs) derived from Magnetic Resonance scans and from the Automated Anatomical Labeling map. Results were standardized by applying a simple linear regression line obtained from the entire patient dataset. Our findings show that we can obtain a set of optimal parameters for each reconstruction strategy. The accuracy of the standardized SUR increases when the reconstruction method includes more corrections. The use of generic ROIs instead of subject-specific ROIs adds significant inaccuracies. Thus, after reconstruction with OSEM and correction for all degradations, subject-specific ROIs led to errors between standardized and true SUR values in the range [-0.5, +0.5] in 87% and 92% of the cases for caudate and putamen, respectively. These percentages dropped to 75% and 88% when the generic ROIs were used.

Dopamine transporter imaging deficit predicts early transition to synucleinopathy in idiopathic rapid eye movement sleep behavior disorder

OBJECTIVE

To determine the usefulness of dopamine transporter (DAT) imaging to identify idiopathic rapid eye movement sleep behavior disorder (IRBD) patients at risk for short-term development of clinically defined synucleinopathy.

METHODS

Eighty-seven patients with polysomnography-confirmed IRBD underwent ¹²³ I-FP-CIT DAT-SPECT. Results were compared to 20 matched controls without RBD who underwent DAT-SPECT. In patients, FP-CIT uptake was considered abnormal when values were two standard deviations below controls' mean uptake. After DAT-SPECT, patients were followed up during 5.7 ± 2.2 (range, 2.6-9.9) years.

RESULTS

Baseline DAT deficit was found in 51 (58.6%) patients. During follow-up, 25 (28.7%) subjects developed clinically defined synucleinopathy (Parkinson's disease in 11, dementia with Lewy bodies in 13, and multiple system atrophy in 1) with mean latency of 3.2 ± 1.9 years from imaging. Kaplan-Meier survival analysis showed increased risk of incident synucleinopathy in patients with abnormal DAT-SPECT than with normal DAT-SPECT (20% vs 6% at 3 years, 33% vs 18% at 5 years; log rank test, p = 0.006). Receiver operating characteristics curve revealed that reduction of FP-CIT uptake in putamen greater than 25% discriminated patients with DAT deficit who developed synucleinopathy from patients with DAT deficit that remained disease free after 3 years of follow-up. At 5-year follow-up, DAT-SPECT had 75% sensitivity, 51% specificity, 44% positive predictive value, 80% negative predictive value, and likelihood ratio 1.54 to predict synucleinopathy.

INTERPRETATION

DAT-SPECT identifies IRBD patients at short-term risk for synucleinopathy. Decreased FP-CIT putamen uptake greater than 25% predicts synucleinopathy after 3 years' follow-up. These observations may be useful to select candidates for disease modification trials in IRBD. Ann Neurol 2017;82:419-428.

Correlation of 18F-FDG uptake on PET/CT with Ki67 immunohistochemistry in pre-treatment epithelial ovarian cancer

OBJECTIVE

Standardised uptake value (SUV) and volumetric parameters such as metabolic tumour volume (MTV) and total lesion glycolysis (TLG) from ¹⁸F-FDG PET/CT are useful criteria for disease prognosis in pre-operative and post-treatment epithelial ovarian cancer (EOC). Ki67 is another prognostic biomarker in EOC, associated with tumour aggressiveness. The aim of this study is to evaluate the association between ¹⁸F-FDG PET/CT measurements and Ki67 in pre-treatment EOC to determine if PET/CT parameters could non-invasively predict tumour aggressiveness.

MATERIAL AND METHODS

A pre-treatment PET/CT was performed on 18 patients with suspected or newly diagnosed EOC. Maximum SUV (SUVmax), mean SUV (SUVmean), whole-body MTV (wbMTV), and whole-body TLG (wbTLG) with a threshold of 30% and 40% of the SUVmax were obtained. Furthermore, Ki67 index (mean and hotspot) was estimated in tumour tissue specimens. Immunohistochemical findings were correlated with PET parameters.

RESULTS

The mean age was 57.0 years old (standard deviation 13.6 years). A moderate correlation was observed between mean Ki67 index and SUVmax (r=0.392), SUVmean 30% (r=0.437), and SUVmean 40% (r=0.443), and also between hotspot Ki67 index and SUVmax (r=0.360), SUVmean 30% (r=0.362) and SUVmean 40% (r=0.319). There was a weaker correlation, which was inversely negative, between mean and hotspot Ki67 and volumetric PET parameters. However, no statistical significant differences were found for any correlations.

CONCLUSIONS

SUVmax and SUVmean were moderately correlated with Ki67 index, whereas volumetric PET parameters overall, showed a weaker correlation. Thus, SUVmax and SUVmean could be used to assess tumour aggressiveness in pre-treatment EOC.

Characterization of patients with longstanding idiopathic REM sleep behavior disorder

OBJECTIVE

To evaluate the presence of prodromal markers of Parkinson disease (PD) in patients with longstanding idiopathic REM sleep behavior disorder (IRBD), a small subgroup of individuals with IRBD with long-term follow-up thought not to be at risk of developing PD.

METHODS

Demographic, clinical, and neuroimaging markers of PD were evaluated in 20 patients with polysomnographic-confirmed longstanding IRBD and in 32 matched controls.

RESULTS

Patients were 16 men and 4 women with mean age of 72.9 ± 8.6 years and mean follow-up from IRBD diagnosis of 12.1 ± 2.6 years. Patients more often had objective smell loss (35% vs 3.4%, p = 0.003), constipation (50% vs 15.6%, p = 0.008), and mild parkinsonian signs (45% vs 18.8%, p = 0.042) than controls. Unified Parkinson's Disease Rating Scale motor score was higher in patients than in controls (5.6 ± 3.5 vs 2.0 ± 2.1, p < 0.0001). Dopamine transporter imaging showed decreased striatal uptake in 82.4% of the patients and transcranial sonography found substantia nigra hyperechogenicity in 35.3%. α-Synuclein aggregates were found in 3 of 6 patients who underwent colon or submandibular gland biopsies. All 20 patients showed clinical, neuroimaging, or histologic markers of PD. Probability of prodromal PD (according to recent Movement Disorders Society research criteria) was higher in patients than in controls (<0.0001), and 45% of patients surpassed 80% probability.

CONCLUSIONS

Prodromal PD markers are common in individuals with longstanding IRBD, suggesting that they are affected by an underlying neurodegenerative process. This observation may be useful for the design of disease-modifying trials to prevent PD onset in IRBD.

The prodromal phase of leucine-rich repeat kinase 2-associated Parkinson disease: Clinical and imaging Studies

BACKGROUND

Asymptomatic, nonmanifesting carriers of leucine-rich repeat kinase 2 mutations are at increased risk of developing PD. Clinical and neuroimaging features may be associated with gene carriage and/or may demarcate individuals at greater risk for phenoconversion to PD.

OBJECTIVES

To investigate clinical and dopamine transporter single-photon emission computed tomography imaging characteristics of leucine-rich repeat kinase 2 asymptomatic carriers.

METHODS

A total of 342 carriers' and 259 noncarriers' relatives of G2019S leucine-rich repeat kinase 2/PD patients and 39 carriers' and 31 noncarriers' relatives of R1441G leucine-rich repeat kinase 2/PD patients were evaluated. Motor and nonmotor symptoms were assessed using specific scales and questionnaires. Neuroimaging quantitative data were obtained in 81 carriers and compared with 41 noncarriers.

RESULTS

G2019S carriers scored higher in motor scores and had lower radioligand uptake compared to noncarriers, but no differences in nonmotor symptoms scores were observed. R1441G carriers scored higher in motor scores, had lower radioligand uptake, and had higher scores in depression, dysautonomia, and Rapid Eye Movements Sleep Behavior Disorder Screening Questionnaire scores, but had better cognition scores than noncarriers. Among G2019S carriers, a group with "mild motor signs" was identified, and was significantly older, with worse olfaction and lower radioligand uptake.

CONCLUSIONS

G2019S and R1441G carriers differ from their noncarriers' relatives in higher motor scores and slightly lower radioligand uptake. Nonmotor symptoms were mild, and different nonmotor profiles were observed in G2019S carriers compared to R1441G carriers. A group of G2019S carriers with known prodromal features was identified. Longitudinal studies are required to determine whether such individuals are at short-term risk of developing overt parkinsonism. © 2017 International Parkinson and Movement Disorder Society.

18F-FDG PET/CT and sentinel lymph node biopsy in the staging of patients with cervical and endometrial cancer. Role of dual-time-point imaging

OBJECTIVE

Definitive staging for cervical (CC) and endometrial cancer (EC) takes place once surgery is performed. The aim of this study was to evaluate the role of PET/CT in detecting lymphatic metastasis in patients with CC and EC using dual-time-point imaging (DPI), taking the histopathological results of sentinel lymph node (SLN) and lymphadenectomy as the reference.

MATERIAL AND METHODS

A prospective study was conducted on 17 patients with early CC, and 13 patients with high-risk EC. The patients had a pre-operative PET/CT, MRI, SLN detection, and lymphadenectomy, when indicated. PET/CT findings were compared with histopathological results.

RESULTS

In the pathology study, 4 patients with CC and 4 patients with EC had lymphatic metastasis. PET/CT showed hypermetabolic nodes in 1 patient with CC, and 5 with EC. Four of these had metastasis, one detected in the SLN biopsy. Four patients who had negative PET/CT had micrometastasis in the SLN biopsy, 1 patient with additional lymph nodes involvement. The overall patient-based sensitivity, specificity, positive and negative predictive values, and accuracy of PET/CT to detect lymphatic metastasis was 20.0%, 100.0%, 100.0%, 87.9%, and 88.2%, respectively, in CC, and 57.1%, 88.9%, 66.7%, 84.2% and 80.0%, respectively, in EC. DPI showed higher retention index in malignant than in inflammatory nodes, although no statistically significant differences were found.

CONCLUSIONS

PET/CT has low sensitivity in lymph node staging of CC and EC, owing to the lack of detection of micrometastasis. Thus, PET/CT cannot replace SLN biopsy. Although no statistically significant differences were found, DPI may help to differentiate between inflammatory and malignant nodes.

Assessment of α-synuclein in submandibular glands of patients with idiopathic rapid-eye-movement sleep behaviour disorder: a case-control study

BACKGROUND

The histological feature of Parkinson's disease is the presence of intraneuronal aggregates of phosphorylated α-synuclein (αSyn). In patients with Parkinson's disease, deposits of αSyn are found in the autonomic nerve fibres of the submandibular gland. Since patients with idiopathic rapid-eye-movement sleep behaviour disorder (IRBD) can develop Parkinson's disease and other synucleinopathies, we investigated whether αSyn deposits could also be detected in their submandibular gland nerve fibres.

METHODS

We did a case-control study at the Hospital Clinic de Barcelona (Barcelona, Spain) in patients with polysomnographic-confirmed IRBD, patients with clinically diagnosed Parkinson's disease, and controls matched by age with the IRBD group. The controls were either healthy, had had elective neck surgery in the clinic, or were patients who had died in the clinic and had an autopsy. We did a transcutaneous core needle biopsy of the submandibular gland with ultrasound guidance in patients with IRBD or Parkinson's disease, and healthy controls, and without ultrasound guidance in the other controls. We assessed the presence of αSyn with immunohistochemistry using 129-phosphorylated antiserine monoclonal antibody, and analysed quantitative variables with Kruskall-Wallis tests and qualitative variables with Fisher's exact tests.

FINDINGS

We did our study between July 16, 2014, and May 16, 2015, and recruited 21 patients with IRBD, 24 patients with Parkinson's disease, and 26 controls (seven healthy, 11 patients undergoing neck surgery, and eight autopsies). We obtained submandibular biopsy material containing glandular parenchyma in nine (43%) of 21 patients with IRBD, 12 (50%) of 24 patients with Parkinson's disease, and all (100%) of the 26 controls. αSyn aggregates were detected in nerve fibres of the glandular parenchyma in eight (89%) of nine patients with IRBD and eight (67%) of 12 with Parkinson's disease, but none of the controls. Of the individuals whose biopsy samples did not contain glandular parenchyma, deposits of αSyn were found in extraglandular tissues in an additional three (25%) of 12 patients with IRBD and five (42%) of 12 patients with Parkinson's disease. None of the controls showed αSyn immunoreactivity in extraglandular tissues. Of the 52 participants who had ultrasonography-guided biopsy, 11 (21%) reported mild-to-moderate local pain, and nine (17%) developed a subcutaneous haematoma; however, these adverse events were transient and did not need treatment.

INTERPRETATION

Our findings suggest that, in patients with IRBD, submandibular gland biopsy is a safe procedure for the detection of αSyn aggregates. αSyn detection could be useful for histological confirmation in individuals clinically diagnosed with Parkinson's disease.

FUNDING

Centre for Networked Biomedical Research in Neurodegenerative Disorders (CIBERNED), Barcelona, Spain.

Dual time-point (18)F-FDG PET/CT to assess response to radiofrequency ablation of lung metastases

AIM

To establish the usefulness of dual time-point PET/CT imaging in determining the response to radiofrequency ablation (RFA) of solitary lung metastases from gastrointestinal cancer.

MATERIALS AND METHODS

This prospective study included 18 cases (3 female, 15 male, mean age 71±15 yrs) with solitary lung metastases from malignant digestive tract tumors candidates for RFA. PET/CT images 1h after injection of 4.07MBq/kg of (18)F-FDG (standard images) were performed at baseline, 1 month, and 3 months after RFA. PET/CT images 2h after injection centered in the thorax at 1 month after RFA were also performed (delayed images). A retention index (RI) of dual time-point images was calculated as follows: RI=(SUVmax delayed image-SUVmax standard image/SUVmax standard image)*100. Pathological confirmation of residual tumor by histology of the treated lesion was considered as local recurrence. A negative imaging follow-up was considered as complete response.

RESULTS

Local recurrence was found in 6/18 lesions, and complete response in the remaining 12. The mean percentage change in SUVmax at 1 month and at 3 months showed a sensitivity and specificity for PET/CT of 50% and 33%, and 67% and 92%, respectively. The RI at 1 month after RFA showed a sensitivity and specificity of 83% and 92%, respectively.

CONCLUSIONS

Dual time point PET/CT can predict the outcome at one month after RFA in lung metastases from digestive tract cancers. The RI can be used to indicate the need for further procedures to rule out persistent tumor due to incomplete RFA.

Prognostic value of (18)F-FDG PET/CT volumetric parameters in recurrent epithelial ovarian cancer

OBJECTIVE

Metabolic tumour volume (MTV) and total lesion glycolysis (TLG) from (18)F-FDG PET/CT are emerging prognostic biomarkers in various solid neoplasms. These volumetric parameters and the SUVmax have shown to be useful criteria for disease prognostication in preoperative and post-treatment epithelial ovarian cancer (EOC) patients. The purpose of this study was to evaluate the utility of (18)F-FDG PET/CT measurements to predict survival in patients with recurrent EOC.

MATERIAL AND METHODS

Twenty-six patients with EOC who underwent a total of 31 (18)F-FDG PET/CT studies for suspected recurrence were retrospectively included. SUVmax and volumetric parameters whole-body MTV (wbMTV) and whole-body TLG (wbTLG) with a threshold of 40% and 50% of the SUVmax were obtained. Correlation between PET parameters and progression-free survival (PFS) and the survival analysis of prognostic factors were calculated.

RESULTS

Serous cancer was the most common histological subtype (76.9%). The median PFS was 12.5 months (range 10.7-20.6 months). Volumetric parameters showed moderate inverse correlation with PFS but there was no significant correlation in the case of SUVmax. The correlation was stronger for first recurrences. By Kaplan-Meier analysis and log-rank test, wbMTV 40%, wbMTV 50% and wbTLG 50% correlated with PFS. However, SUVmax and wbTLG 40% were not statistically significant predictors for PFS.

CONCLUSION

Volumetric parameters wbMTV and wbTLG 50% measured by (18)F-FDG PET/CT appear to be useful prognostic predictors of outcome and may provide valuable information to individualize treatment strategies in patients with recurrent EOC.

11C-Choline PET/CT in the primary diagnosis of prostate cancer: impact on treatment planning

AIM

Aim of the present study was to evaluate the usefulness of 11C-choline PET/CT for detecting lymphatic or haematogenous spread and for planning radiotherapy in patients with medium-to-high risk prostate cancer.

METHODS

We have included 61 consecutive patients recently diagnosed with cancer prostate by biopsy. All patients were classified as medium-to-high risk: Gleason: 7-9; PSA: 6.3-30.4 ng/mL; stage T2c (N.=20) or stage T3 (N.=41). Image acquisition began 5 min after intravenous injection of 11C-choline (656+119 MBq), starting at the pelvis and continuing craniocaudally. Images were interpreted visually to evaluate uptake by the prostate gland. Lymph nodes with 11C-choline uptake were considered invaded, regardless of their size. Bone lesions were considered positive when they showed greater focal uptake than the surrounding bone. In patients with evidence of lymph-node invasion or bone metastases (15 patients), disease was classified as locoregional, oligometastatic, or multimetastatic.

RESULTS

All patients had prostate gland uptake (20 focal, 8 bifocal, and 33 multifocal). Extraprostatic disease was present in 15 patients (24.6%), as follows: 9 (60%) in a single location: in an infradiaphragmatic lymph node (N.=6), in a supradiaphragmatic lymph node (N.=1), and in bone (M1) (N.=2). Six (40%) as multifocal invasion: with both infra- and supradiaphragmatic lymph node involvement (N.=2); with infradiaphragmatic lymph node involvement and M1 bone metastases (N.=3); and infra- and supradiaphragmatic lymph node involvement plus M1 bone metastases (N.=1). Disease was classified as locoregional (N.=6), oligometastatic (N.=5), and multimetastatic (N.=4). The 11 (73.3%) patients with locoregional and oligometastatic disease were selected to undergo intensity-modulated radiation therapy with dose escalation based on the PET findings.

CONCLUSION

Our results suggest that 11C-choline PET/CT is a useful one-stop diagnostic procedure for evaluating patients with medium/high risk prostate cancer scheduled for radical treatment. 11C-choline PET/CT can reliably rule out lymph node involvement and remote metastases, allowing to select candidates for radiotherapy and to plan their treatment.

Clinical and imaging markers in premotor LRRK2 G2019S mutation carriers

BACKGROUND

Substantia nigra hyperechogenicity (SN+) has been proposed as a risk marker of Parkinson's disease (PD). Asymptomatic LRRK2 mutation carriers (aLRRK2+), at high risk for developing PD, provide an opportunity for the study of preclinical biomarkers.

OBJECTIVE

To assess SN echogenicity and other echographic features in LRRK2 G2019S carriers and their clinical and imaging correlates.

METHODS

Transcranial sonography was performed in 26 LRRK2 G2019S PD patients, 50 first-degree relatives, 31 idiopathic PD (IPD) patients and 26 controls. SN echogenicity and other echographic features were assessed in all study subjects. Dopamine transporter imaging (DAT-SPECT) was performed in 29 first-degree relatives.

RESULTS

75% of the LRRK2-PD and 87.5% of the IPD showed SN+ (p = 0.087). aLRRK2+ had a higher frequency of SN+ than non carriers (58.3% vs. 25%, p = 0.039) and controls (58.3% vs. 12.5%; p = 0.002) and had a larger area of SN echogenicity than non carriers (p = 0.030) and controls (p < 0.001). The width of the third ventricle was significantly lower in LRRK2-PD than in IPD (1.9 mm [1.38; 2.75] vs. 3.0 mm [2.3; 5.3]; p = 0.003). Four out of 5 (80%) of the aLRRK2+ with an abnormal DAT-SPECT and four of the 5 (80%) of those with REM sleep behaviour disorder (RBD) had SN+.

CONCLUSIONS

SN+ is very frequent in LRRK2-PD and aLRRK2+. Most aLRRK2 with possible surrogate markers of PD such as abnormal DAT-SPECT or RBD, also had SN+, which supports that this echofeature might be a marker of PD in these asymptomatic population.

Dual-phase 11C-choline PET/computed tomography in the early evaluation of prostate cancer recurrence

PURPOSE

The aim of this study was to assess dual-phase 11C-choline PET/computed tomography (CT) for differentiating benign from malignant lesions in patients with biochemical recurrence of prostate cancer.

MATERIALS AND METHODS

We prospectively studied 56 patients with prostate cancer treated by surgery (n=22) or radiotherapy (n=34) who had hypermetabolic foci on 11C-choline PET/CT determined for biochemical recurrence (prostate-specific antigen 1.23-9.9 ng/ml). We used the dual-phase technique, calculating the standardized uptake value (SUV) for early (SUVearly) and late (SUVdelay) acquisitions and the difference between the two (SUVvariation) to determine whether tracer uptake remained stable or increased (accumulative pattern) or decreased (washout pattern). We used t-tests to compare mean and receiver operating characteristic curve analysis (SUVearly/SUVdelay/SUVvariation vs. benign/malignant).

RESULTS

We identified 106 hypermetabolic foci (34 local, 10 inguinal, 34 infradiaphragmatic, 14 supradiaphragmatic, and 14 in bone). We identified 34 local foci (eight after prostatectomy and 26 after radiotherapy). The eight postsurgical foci had an accumulative pattern and recurrence was confirmed (three histology, five follow-up). Of the 26 postradiotherapy foci, three had a washout pattern and follow-up ruled out recurrence; 23 had an accumulative pattern and recurrence was confirmed (14 histology, nine follow-up). The 10 inguinal foci had a washout pattern and were reactive (three histology, seven follow-up). The 34 infradiaphragmatic foci had an accumulative pattern and were malignant (34 follow-up). Of the 14 supradiaphragmatic foci, the three with a washout pattern were benign (three histology) and the 11 with an accumulative pattern were malignant (11 histology). Of the 14 foci in bone, two had a washout pattern and corresponded with signs of spondyloarthropathy. On the receiver operating characteristic curve analysis, SUVvariation best discriminated benign from malignant lesions [area under the curve (AUC)=0.993], followed by SUVdelay (AUC=0.933) and finally SUVearly (AUC=0.665).

CONCLUSION

Dual-phase PET/CT with 11C-choline is technically feasible despite this tracer's short physical half-life and is useful for discriminating benign from malignant lesions. SUVvariation accurately discriminated between benign and malignant lesions.

Validation of semi-quantitative methods for DAT SPECT: influence of anatomical variability and partial volume effect

The aim of this work was to evaluate the influence of anatomical variability between subjects and of the partial volume effect (PVE) on the standardized Specific Uptake Ratio (SUR) in [(123)I]FP-bib SPECT studies. To this end, magnetic resonance (MR) images of 23 subjects with differences in the striatal volume of up to 44% were segmented and used to generate a database of 138 Monte Carlo simulated SPECT studies. Data included normal uptakes and pathological cases. Studies were reconstructed by filtered back projection (FBP) and the ordered-subset expectation-maximization algorithm. Quantification was carried out by applying a reference method based on regions of interest (ROIs) derived from the MR images and ROIs derived from the Automated Anatomical Labelling map. Our results showed that, regardless of anatomical variability, the relationship between calculated and true SUR values for caudate and putamen could be described by a multiple linear model which took into account the spill-over phenomenon caused by PVE (R² ≥ 0.963 for caudate and ≥0.980 for putamen) and also by a simple linear model (R(2) ≥ 0.952 for caudate and ≥0.973 for putamen). Calculated values were standardized by inverting both linear systems. Differences between standardized and true values showed that, although the multiple linear model was the best approach in terms of variability (X² ≥ 11.79 for caudate and ≤7.36 for putamen), standardization based on a simple linear model was also suitable (X² ≥ 12.44 for caudate and ≤12.57 for putamen).

Dopamine transporter imaging in the aged rat: a [¹²³I]FP-CIT SPECT study

INTRODUCTION

Rodent models are extensively used to assess the biochemical and physiological changes associated with aging. They play a major role in the development of therapies for age-related pathologies such as Parkinson's disease. To validate the usefulness of these animal models in aging or age-related disease research, the consistency of cerebral aging processes across species must be evaluated. The dopaminergic system seems particularly susceptible to the aging process. One of the results of this susceptibility is a decline in striatal dopamine transporter (DAT) availability.

METHODS

We sought to ascertain whether similar age changes could be detected in-vivo in rats, using molecular imaging techniques such as single photon emission computed tomography (SPECT) with [(123)I]FP-CIT.

RESULTS

A significant decrease of 17.21% in the striatal specific uptake ratio was observed in the aged rats with respect to the young control group.

CONCLUSIONS

Our findings suggest that age-related degeneration in the nigrostriatal track is similar in humans and rats, which supports the use of this animal in models to evaluate the effect of aging on the dopaminergic system.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Our findings indicate that age-related degeneration in the nigrostriatal track is similar in humans and rats and that these changes can be monitored in vivo using small animal SPECT with [(123)I]FP-CIT, which could facilitate the translational research in rat models of age related disorders of dopaminergic system.

In vivo evaluation of the dopaminergic neurotransmission system using [123I]FP-CIT SPECT in 6-OHDA lesioned rats

The 6-hydroxydopamine (6-OHDA) rodent model of Parkinson's disease (PD) has been used to evaluate the nigrostriatal pathway. The aim of this work was to explore the relationship between the degree of 6-OHDA-induced dopaminergic degeneration and [(123)I]FP-CIT binding using single photon emission computed tomography (SPECT). Fourteen rats received a 6-OHDA injection (4 or 8 µg) into the left medial forebrain bundle. After 3 weeks, magnetic resonance imaging and scans with a small-animal SPECT system were performed. Finally, the nigrostriatal lesion was assessed by immunohistochemical analysis. Immunohistochemical analysis confirmed two levels of dopaminergic degeneration. Lesions induced by 6-OHDA diminished the ipsilateral [(123)I]FP-CIT binding by 61 and 76%, respectively. The decrease in tracer uptake between control and lesioned animals was statistically significant, as was the difference between the two 6-OHDA lesioned groups. Results concluded that [(123)I]FP-CIT SPECT is a useful technique to discriminate the degree of dopaminergic degeneration in a rat model of PD.

[Functional neuroimaging in the diagnosis of patients with Parkinsonism: Update and recommendations for clinical use]

Functional Neuroimaging has been traditionally used in research for patients with different Parkinsonian syndromes. However, the emergence of commercial radiotracers together with the availability of single photon emission computed tomography (SPECT) and, more recently, positron emission tomography (PET) have made them available for clinical practice. Particularly, the development of clinical evidence achieved by functional neuroimaging techniques over the past two decades have motivated a progressive inclusion of several biomarkers in the clinical diagnostic criteria for neurodegenerative diseases that occur with Parkinsonism. However, the wide range of radiotracers designed to assess the involvement of different pathways in the neurodegenerative process underlying Parkinsonian syndromes (dopaminergic nigrostriatal pathway integrity, basal ganglia and cortical neuronal activity, myocardial sympathetic innervation), and the different neuroimaging techniques currently available (scintigraphy, SPECT and PET), have generated some controversy concerning the best neuroimaging test that should be indicated for the differential diagnosis of Parkinsonism. In this article, a panel of nuclear medicine and neurology experts has evaluated the functional neuroimaging techniques emphazising practical considerations related to the diagnosis of patients with uncertain origin parkinsonism and the assessment Parkinson's disease progression.

[PET and SPECT in epilepsy]

Epilepsy is one of the most frequent chronic neurological disorders, affecting 1-2% of the population. Patients with complex partial drug resistant episodes may benefit from a surgical treatment consisting in the excision of the epileptogenic area. Localization of the epileptogenic area was classically performed with video-EEG and magnetic resonance (MR). Recently, functional neuroimaging studies of Nuclear Medicine, positron emission tomography (PET) and single photon emission tomography (SPECT) have demonstrated their utility in the localization of the epileptogenic area prior to surgery. Ictal SPECT with brain perfusion tracers show an increase in blood flow in the initial ictal focus, while PET with (18)FDG demonstrates a decrease of glucose metabolism in the interictal functional deficit zone. In this review, the basic principles and methodological characteristics of the SPECT and PET in epilepsy are described. The ictal SPECT injection mechanism, different patterns of perfusion based on the time of ictal, postictal or interictal injection are detailed and the different diagnostic sensitivities of each one of these SPECT are reviewed. Different methods of analysis of the images with substraction and fusion systems with the MR are described. Similarly, the injection methodology, quantification and evaluation of the images of the PET in epilepsy are described. Finally, the main clinical indications of SPECT and PET in temporal and extratemporal epilepsy are detailed.