Does posterior cingulate hypometabolism result from disconnection or local pathology across preclinical and clinical stages of Alzheimer’s disease?

Purpose

Posterior cingulate cortex (PCC) hypometabolism as measured by FDG PET is an indicator of Alzheimer’s disease (AD) in prodromal stages, such as in mild cognitive impairment (MCI), and has been found to be closely associated with hippocampus atrophy in AD dementia. We studied the effects of local and remote atrophy and of local amyloid load on the PCC metabolic signal in patients with different preclinical and clinical stages of AD.

Methods

We determined the volume of the hippocampus and PCC grey matter based on volumetric MRI scans, PCC amyloid load based on AV45 PET, and PCC metabolism based on FDG PET in 667 subjects participating in the Alzheimer’s Disease Neuroimaging Initiative spanning the range from cognitively normal ageing through prodromal AD to AD dementia.

Results

In cognitively normal individuals and those with early MCI, PCC hypometabolism was exclusively associated with hippocampus atrophy, whereas in subjects with late MCI it was associated with both local and remote effects of atrophy as well as local amyloid load. In subjects with AD dementia, PCC hypometabolism was exclusively related to local atrophy.

Conclusion

Our findings suggest that the effects of remote pathology on PCC hypometabolism decrease and the effects of local pathology increase from preclinical to clinical stages of AD, consistent with a progressive disconnection of the PCC from downstream cortical and subcortical brain regions.

     

Early identification of MCI converting to AD: a FDG PET study

Purpose

Mild cognitive impairment (MCI) is a transitional pathological stage between normal ageing (NA) and Alzheimer’s disease (AD). Although subjects with MCI show a decline at different rates, some individuals remain stable or even show an improvement in their cognitive level after some years. We assessed the accuracy of FDG PET in discriminating MCI patients who converted to AD from those who did not.

Methods

FDG PET was performed in 42 NA subjects, 27 MCI patients who had not converted to AD at 5 years (nc-MCI; mean follow-up time 7.5 ± 1.5 years), and 95 MCI patients who converted to AD within 5 years (MCI-AD; mean conversion time 1.8 ± 1.1 years). Relative FDG uptake values in 26 meta-volumes of interest were submitted to ANCOVA and support vector machine analyses to evaluate regional differences and discrimination accuracy.

Results

The MCI-AD group showed significantly lower FDG uptake values in the temporoparietal cortex than the other two groups. FDG uptake values in the nc-MCI group were similar to those in the NA group. Support vector machine analysis discriminated nc-MCI from MCI-AD patients with an accuracy of 89% (AUC 0.91), correctly detecting 93% of the nc-MCI patients.

Conclusion

In MCI patients not converting to AD within a minimum follow-up time of 5 years and MCI patients converting within 5 years, baseline FDG PET and volume-based analysis identified those who converted with an accuracy of 89%. However, further analysis is needed in patients with amnestic MCI who convert to a dementia other than AD.

     

Value of FDG-PET scans of non-demented patients in predicting rates of future cognitive and functional decline

Purpose

The aim of this study was to examine the value of fluorodeoxyglucose (FDG) positron emission tomography (PET) in predicting subsequent rates of functional and cognitive decline among subjects considered cognitively normal (CN) or clinically diagnosed with mild cognitive impairment (MCI).

Methods

Analyses of 276 subjects, 92 CN subjects and 184 with MCI, who were enrolled in the Alzheimer’s Disease Neuroimaging Initiative, were conducted. Functional decline was assessed using scores on the Functional Activities Questionnaire (FAQ) obtained over a period of 36 months, while cognitive decline was determined using the Alzheimer’s disease Assessment Scale-Cognitive subscale (ADAS-Cog) and Mini-Mental State Examination (MMSE) scores. PET images were analyzed using clinically routine brain quantification software. A dementia prognosis index (DPI), derived from a ratio of uptake values in regions of interest known to be hypometabolic in Alzheimer’s disease to regions known to be stable, was generated for each baseline FDG-PET scan. The DPI was correlated with change in scores on the neuropsychological examinations to examine the predictive value of baseline FDG-PET.

Results

DPI powerfully predicted rate of functional decline among MCI patients (t = 5.75, p?<?1.0E-8) and pooled N?+?MCI patient groups (t?=?7.02, p?<?1.0E-11). Rate of cognitive decline on MMSE was also predicted by the DPI among MCI (t?=?6.96, p?<?1.0E-10) and pooled N?+?MCI (t?=?8.78, p?<?5.0E-16). Rate of cognitive decline on ADAS-cog was powerfully predicted by the DPI alone among N (p?<?0.001), MCI (t?=?6.46, p?<?1.0E-9) and for pooled N?+?MCI (t?=?8.85, p?=?1.1E-16).

Conclusions

These findings suggest that an index, derivable from automated regional analysis of brain PET scans, can be used to help predict rates of functional and cognitive deterioration in the years following baseline PET.

     

Imaging in-vivo tau pathology in Alzheimer’s disease with THK5317 PET in a multimodal paradigm

Purpose

The aim of this study was to explore the cerebral distribution of the tau-specific PET tracer [¹⁸F]THK5317 (also known as (S)-[¹⁸F]THK5117) retention in different stages of Alzheimer’s disease; and study any associations with markers of hypometabolism and amyloid-beta deposition.

Methods

Thirty-three individuals were enrolled, including nine patients with Alzheimer’s disease dementia, thirteen with mild cognitive impairment (MCI), two with non-Alzheimer’s disease dementia, and nine healthy controls (five young and four elderly). In a multi-tracer PET design [¹⁸F]THK5317, [¹¹C] Pittsburgh compound B ([¹¹C]PIB), and [¹⁸F]FDG were used to assess tau pathology, amyloid-beta deposition and cerebral glucose metabolism, respectively. The MCI patients were further divided into MCI [¹¹C]PIB-positive (n?=?11) and MCI [¹¹C]PIB-negative (n?=?2) groups.

Results

Test-retest variability for [¹⁸F]THK5317-PET was very low (1.17–3.81 %), as shown by retesting five patients. The patients with prodromal (MCI [¹¹C]PIB-positive) and dementia-stage Alzheimer’s disease had significantly higher [¹⁸F]THK5317 retention than healthy controls (p?=?0.002 and p?=?0.001, respectively) in areas exceeding limbic regions, and their discrimination from this control group (using the area under the curve) was >98 %. Focal negative correlations between [¹⁸F]THK5317 retention and [¹⁸F]FDG uptake were observed mainly in the frontal cortex, and focal positive correlations were found between [¹⁸F]THK5317 and [¹¹C]PIB retentions isocortically. One patient with corticobasal degeneration syndrome and one with progressive supranuclear palsy showed no [¹¹C]PIB but high [¹⁸F]THK5317 retentions with a different regional distribution from that in Alzheimer’s disease patients.

Conclusions

The tau-specific PET tracer [¹⁸F]THK5317 images in vivo the expected regional distribution of tau pathology. This distribution contrasts with the different patterns of hypometabolism and amyloid-beta deposition.

     

Head motion evaluation and correction for PET scans with 18F-FDG in the Japanese Alzheimer’s disease neuroimaging initiative (J-ADNI) multi-center study

Objective

Head motion during 30-min (six 5-min frames) brain PET scans starting 30 min post-injection of FDG was evaluated together with the effect of post hoc motion correction between frames in J-ADNI multicenter study carried out in 24 PET centers on a total of 172 subjects consisting of 81 normal subjects, 55 mild cognitive impairment (MCI) and 36 mild Alzheimer’s disease (AD) patients.

Methods

Based on the magnitude of the between-frame co-registration parameters, the scans were classified into six levels (A–F) of motion degree. The effect of motion and its correction was evaluated using between-frame variation of the regional FDG uptake values on ROIs placed over cerebral cortical areas.

Result

Although AD patients tended to present larger motion (motion level E or F in 22 % of the subjects) than MCI (3 %) and normal (4 %) subjects, unignorable motion was observed in a small number of subjects in the latter groups as well. The between-frame coefficient of variation (SD/mean) was 0.5 % in the frontal, 0.6 % in the parietal and 1.8 % in the posterior cingulate ROI for the scans of motion level 1. The respective values were 1.5, 1.4, and 3.6 % for the scans of motion level F, but reduced by the motion correction to 0.5, 0.4 and 0.8 %, respectively. The motion correction changed the ROI value for the posterior cingulate cortex by 11.6 % in the case of severest motion.

Conclusion

Substantial head motion occurs in a fraction of subjects in a multicenter setup which includes PET centers lacking sufficient experience in imaging demented patients. A simple frame-by-frame co-registration technique that can be applied to any PET camera model is effective in correcting for motion and improving quantitative capability.

     

Feasibility and acceptance of simultaneous amyloid PET/MRI

Purpose

Established Alzheimer’s disease (AD) biomarker concepts classify into amyloid pathology and neuronal injury biomarkers, while recent alternative concepts classify into diagnostic and progression AD biomarkers. However, combined amyloid positron emission tomography/magnetic resonance imaging (PET/MRI) offers the chance to obtain both biomarker category read-outs within one imaging session, with increased patient as well as referrer convenience. The aim of this pilot study was to investigate this matter for the first time.

Methods

100 subjects (age 70?±?10 yrs, 46 female), n?=?51 with clinically defined mild cognitive impairment (MCI), n?=?44 with possible/probable AD dementia, and n?=?5 with frontotemporal lobe degeneration, underwent simultaneous [¹⁸F]florbetaben or [¹¹C]PIB PET/MRI (3 Tesla Siemens mMR). Brain amyloid load, mesial temporal lobe atrophy (MTLA) by means of the Scheltens scale, and other morphological brain pathologies were scored by respective experts. The patients/caregivers as well as the referrers were asked to assess on a five-point scale the convenience related to the one-stop-shop PET and MRI approach.

Results

In three subjects, MRI revealed temporal lobe abnormalities other than MTLA. According to the National Institute on Aging-Alzheimer’s Association classification, the combined amyloid-beta PET/MRI evaluation resulted in 31 %, 45 %, and 24 % of the MCI subjects being categorized as “MCI-unlikely due to AD”, “MCI due to AD-intermediate likelihood”, and “MCI due to AD-high likelihood”, respectively. 50 % of the probable AD dementia patients were categorized as “High level of evidence of AD pathophysiological process”, and 56 % of the possible AD dementia patients as “Possible AD dementia - with evidence of AD pathophysiological process”. With regard to the International Working Group 2 classification, 36 subjects had both positive diagnostic and progression biomarkers. The patient/caregiver survey revealed a gain of convenience in 88 % of responders as compared to a theoretically separate PET and MR imaging. In the referrer survey, an influence of the combined amyloid-beta PET/MRI on the final diagnosis was reported by 82 % of responders, with a referrer acceptance score of 3.7?±?1.0 on a 5-point scale.

Conclusion

Simultaneous amyloid PET/MRI is feasible and provides imaging biomarkers of all categories which are able to supplement the clinical diagnosis of MCI due to AD and that of AD dementia. Further, patient and referrer convenience is improved by this one-stop-shop imaging approach.

     

18F–FDG PET diagnostic and prognostic patterns do not overlap in Alzheimer’s disease (AD) patients at the mild cognitive impairment (MCI) stage

Purpose

We aimed to identify the cortical regions where hypometabolism can predict the speed of conversion to dementia in mild cognitive impairment due to Alzheimer’s disease (MCI-AD).

Methods

We selected from the clinical database of our tertiary center memory clinic, eighty-two consecutive MCI-AD that underwent 18F–fluorodeoxyglucose (FDG) PET at baseline during the first diagnostic work-up and were followed up at least until their clinical conversion to AD dementia. The whole group of MCI-AD was compared in SPM8 with a group of age-matched healthy controls (CTR) to verify the presence of AD diagnostic-pattern; then the correlation between conversion time and brain metabolism was assessed to identify the prognostic-pattern. Significance threshold was set at p < 0.05 False-Discovery-Rate (FDR) corrected at peak and at cluster level. Each MCI-AD was then compared with CTR by means of a SPM single-subject analysis and grouped according to presence of AD diagnostic-pattern and prognostic-pattern. Kaplan-Meier-analysis was used to evaluate if diagnostic- and/or prognostic-patterns can predict speed of conversion to dementia.

Results

Diagnostic-pattern corresponded to typical posterior hypometabolism (BA 7, 18, 19, 30, 31 and 40) and did not correlate with time to conversion, which was instead correlated with metabolic levels in right middle and inferior temporal gyri as well as in the fusiform gyrus (prognostic-pattern, BA 20, 21 and 38). At Kaplan-Meier analysis, patients with hypometabolism in the prognostic pattern converted to AD-dementia significantly earlier than patients not showing significant hypometabolism in the right middle and inferior temporal cortex (9 versus 19 months; Log rank p < 0.02, Breslow test: p < 0.003, Tarone-Ware test: p < 0.007).

Conclusion

The present findings support the role of FDG PET as a robust progression biomarker even in a naturalist population of MCI-AD. However, not the AD-typical diagnostic-pattern in posterior regions but the middle and inferior temporal metabolism captures speed of conversion to dementia in MCI-AD since baseline. The highlighted prognostic pattern is a further, independent source of heterogeneity in MCI-AD and affects a primary-endpoint on interventional clinical trials (time of conversion to dementia).

     

Application of Quantitative Indexes of FDG PET to Treatment Response Evaluation in Indolent Lymphoma

Purpose

Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a standard imaging modality for response evaluation in FDG-avid lymphoma, there is a controversy using FDG PET in indolent lymphoma. The purpose of this study was to investigate the effectiveness of quantitative indexes on FDG PET in response evaluation of the indolent lymphoma.

Methods

Fifty-seven indolent lymphoma patients who completed chemotherapy were retrospectively enrolled. FDG PET/computed tomography (CT) scans were performed at baseline, interim, and end of treatment (EOT). Response was determined by Lugano classification, and progression-free survival (PFS) by follow-up data. Maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured in the single hottest lesion (target A) or five hottest lesions (target B). Their efficacies regarding response evaluation and PFS prediction were evaluated.

Results

On EOT PET, SUV_max, and MTV of both targets were well associated with visual analysis. Changes between initial and EOT PET were not significantly different between CR and non-CR groups. On interim PET, SUV_max, and %ΔSUV_max in both targets were significantly different between CR and non-CR groups. For prediction of PFS, most tested indexes were significant on EOT and interim PET, with SUV_max being the most significant prognostic factor.

Conclusion

Quantitative indexes of FDG PET are well associated with Lugano classification in indolent lymphoma. SUV_max measured in the single hottest lesion can be effective in response evaluation and prognosis prediction on interim and EOT PET.

     

Recurrence of Melanoma After Initial Treatment: Diagnostic Performance of FDG PET in Posttreatment Surveillance

Purpose

In malignant melanoma, recurrence is often observed in distant areas from the primary site. While FDG PET is a sensitive imaging for detecting malignant lesions, the role of FDG PET in posttreatment surveillance period has not been investigated sufficiently. The aim of this study was to evaluate the value of PET during posttreatment surveillance in melanoma.

Methods

A total of 76 melanoma patients who underwent FDG PET during surveillance period after completion of the first treatment were retrospectively enrolled. PET scans were grouped according to the purpose and clinical situations, routine surveillance, or evaluating clinical suspicion. Final diagnosis of recurrence was determined by complete clinical evaluation or long-term follow-up. In each situation, the diagnostic role of FDG PET was assessed.

Results

A total of 143 scans of 76 patients were analyzed: 51 for clinical suspicion and 92 for routine surveillance. In the clinical suspicion group, PET correctly diagnosed non-recurrence in 10 cases (20%). In routine surveillance group, 16 cases (17%) presented recurrence, all of which was correctly diagnosed on PET. NPV and PPV were 100% and 76%, respectively. In subgroup analysis, sensitivity and NPV were higher in the low-risk group (stages I–II_A) than in the high-risk group (stages II_B–IV), while specificity and PPV were higher in the high-risk group.

Conclusion

In conclusion, FDG PET is an effective diagnostic tool in posttreatment surveillance of melanoma. Even in cases without clinical suspicion, melanoma recurs in a considerable proportion of patients, which can be sensitively diagnosed on PET.

     

Three days of high-dose glucocorticoid treatment attenuates large-vessel 18F-FDG uptake in large-vessel giant cell arteritis but with a limited impact on diagnostic accuracy

Purpose

To evaluate the in-treatment diagnostic accuracy of FDG PET/CT in large-vessel giant cell arteritis (LV-GCA) by serial scans before and after a short course of high-dose glucocorticoid treatment.

Methods

Twenty-four glucocorticoid-naïve patients with new-onset PET/CT verified LV-GCA (pre-treatment baseline PET) were prospectively included. Excluded were patients with a previous history of GCA or polymyalgia rheumatica, LV-GCA-mimicking conditions and patients on immunosuppressive therapy. All patients were treated with 60 mg of oral prednisolone daily and assigned for in-treatment FDG PET/CT after either 3 (PET3) or 10 days (PET10). Two experienced nuclear medicine physicians, blinded to patients’ clinical data, reviewed the FDG PET/CT images. A visual semi-quantitative approach was used. Segmental and homogenous FDG uptake in the wall of the aorta and/or supra-aortic branches with higher uptake intensity than liver was considered consistent with vasculitis. Inter-reader reliability was evaluated.

Results

Although glucocorticoid treatment attenuated FDG uptake in large vessels, LV-GCA was accurately diagnosed in 10/10 patients after 3 days of treatment, but only in 5/14 patients after 10 days of treatment (p?<?0.001). Interrater reliability was substantial (agreement 87%, Cohen’s weighted kappa 0.70). No correlation between CRP and FDG uptake was found.

Conclusions

Within 3 days of high-dose glucocorticoid treatment, FDG PET/CT can diagnose LV-GCA with high sensitivity. This window of opportunity ensures that prompt glucocorticoid treatment can be initiated to avoid debilitating GCA complications with a limited effect on diagnostic accuracy. After 10 days of treatment, FDG PET/CT sensitivity decreases significantly.

     

Prognostic value of volumetric FDG PET/CT parameters in patients with oral tongue squamous cell carcinoma who were treated by superselective intra-arterial chemoradiotherapy

Purpose

This study aimed to evaluate the predictive and prognostic value of FDG PET/CT-based volumetric parameters in patients with oral tongue squamous cell carcinoma (OTSCC) treated by superselective intra-arterial chemoradiotherapy (IA-CRT).

Methods

We conducted a retrospective study including 33 patients with biopsy-proven OTSCC between May 2007 and February 2016. All of the patients were treated by IA-CRT. Pretreatment SUV_max and metabolic tumor volume (MTV) of the primary tumor were measured. The SUV thresholds of 2.5 and 5.0 were used. Progression-free survival (PFS) and overall survival (OS) were chosen as endpoints to evaluate prognosis. Univariate and multivariate analyses were performed to assess the potential independent effect of FDG PET/CT parameters.

Results

The median follow-up for surviving patients was 40.7 months (range 6.0–107.5 months). In univariate and multivariate analyses, SUV_max and MTV (5.0) were independent prognostic factors for PFS. In univariate analysis, SUV_max failed to predict OS. MTV (5.0) was a significant prognostic factor for OS, but multivariate analysis failed to show statistical independence because it could not exclude the possibility of an artifact due to N stage.

Conclusions

FDG PET/CT-based volumetric parameters may be significant prognostic markers for survival of patients with OTSCC who are treated by IA-CRT.

     

The effect of hippocampal function,volume and connectivity on posterior cingulate cortex functioning during episodic memory fMRI in mild cognitive impairment

Objectives

Diminished function of the posterior cingulate cortex (PCC) is a typical finding in early Alzheimer’s disease (AD). It is hypothesized that in early stage AD, PCC functioning relates to or reflects hippocampal dysfunction or atrophy. The aim of this study was to examine the relationship between hippocampus function, volume and structural connectivity, and PCC activation during an episodic memory task-related fMRI study in mild cognitive impairment (MCI).

Method

MCI patients (n?=?27) underwent episodic memory task-related fMRI, 3D-T1w MRI, 2D T2-FLAIR MRI and diffusion tensor imaging. Stepwise linear regression analysis was performed to examine the relationship between PCC activation and hippocampal activation, hippocampal volume and diffusion measures within the cingulum along the hippocampus.

Results

We found a significant relationship between PCC and hippocampus activation during successful episodic memory encoding and correct recognition in MCI patients. We found no relationship between the PCC and structural hippocampal predictors.

Conclusions

Our results indicate a relationship between PCC and hippocampus activation during episodic memory engagement in MCI. This may suggest that during episodic memory, functional network deterioration is the most important predictor of PCC functioning in MCI.

Key Points

? PCC functioning during episodic memory relates to hippocampal functioning in MCI.? PCC functioning during episodic memory does not relate to hippocampal structure in MCI.? Functional network changes are an important predictor of PCC functioning in MCI.

     

The clinical utility of FDG PET/CT among solid organ transplant recipients suspected of malignancy or infection

Purpose

Solid organ transplant (SOT) recipients are at high risk of developing infections and malignancies. ¹⁸F-FDG PET/CT may enable timely detection of these diseases and help to ensure early intervention. We aimed to describe the clinical utility of FDG PET/CT in consecutive, diagnostic unresolved SOT recipients transplanted from January 2004 to May 2015.

Methods

Recipients with a post-transplant FDG PET/CT performed as part of diagnostic work-up were included. Detailed chart reviews were done to extract relevant clinical information and determine the final diagnosis related to the FDG PET/CT. Based on á priori defined criteria and the final diagnosis, results from each scan were classified as true or false, and diagnostic values determined.

Results

Among the 1,814 recipients in the cohort, 145 had an FDG PET/CT performed; 122 under the indication of diagnostically unresolved symptoms with a suspicion of malignancy or infection. The remaining (N?=?23) had an FDG PET/CT to follow-up on a known disease or to stage a known malignancy. The 122 recipients underwent a total of 133 FDG PET/CT scans performed for a suspected malignancy (66 %) or an infection (34 %). Sensitivity, specificity, and positive and negative predictive values of the FDG PET/CT in diagnosing these conditions were 97, 84, 87, and 96 %, respectively.

Conclusion

FDG PET/CT is an accurate diagnostic tool for the work-up of diagnostic unresolved SOT recipients suspected of malignancy or infection. The high sensitivity and NPV underlines the potential usefulness of PET/CT for excluding malignancy or focal infections in this often complex clinical situation.

     

Whole body MRI with qualitative and quantitative analysis of DWI for assessment of bone marrow involvement in lymphoma

Aim

Our study aimed to investigate the role of qualitative and quantitative whole body MRI with DWI for assessment of bone marrow involvement (BMI) in newly diagnosed lymphoma using FDG PET–CT and bone marrow biopsy (BMB) as reference standard.

Materials and methods

We retrospectively evaluated 56 patients with newly diagnosed lymphoma (21 Hodgkin’s lymphoma and 35 non-Hodgkin’s lymphoma) who underwent random unilateral BMB, FDG PET–CT and Wb-MRI-DWI for initial staging. In a patient-based analysis, results of Wb-MRI-DWI were compared with FDG PET–CT and BMB. For quantitative analysis, mean ADC values of posterior iliac crest were correlated with BMI and bone marrow cellularity.

Results

WB-MR-DWI obtained excellent concordance with FDG PET–CT both in HL (k = 1.000; 95% CI 1.000–1.000) and in DLBCL (k = 1.000; 95% CI 1.000–1.000). In other NHL, WB-MRI-DWI obtained a good correlation with BMB (k = 0.611; 95% CI 0.295–0.927) while FDG PET–CT had poor concordance (k = 0.067; 95% CI 0.372–0.505). WB-MR-DWI has no false negative errors but 4 false positive results consisting in focal lesions consensually reported by FDG PET–CT and resolved after therapy. No significant correlation between ADC mean value and BMI was found (p = 0.0586).

Conclusion

Our data suggest that Wb-MRI-DWI is a valid technique for BMI assessment in lymphoma patients, thanks to its excellent concordance with FDG PET–CT and good concordance with BMB (superior than FDG PET–CT). If further investigations will confirm our results on larger patient groups, it could become a useful tool in the clinical workup.

     

Automated quantification of amyloid positron emission tomography: a comparison of PMOD and MIMneuro

Objective

The aim of this study was to examine and compare two automated quantitative software tools (PMOD and MIMneuro) for the quantification of amyloid positron emission tomography (PET).

Methods

A total of 30 subjects—15 Alzheimer’s disease (AD) patients and 15 cognitively normal age- and sex-matched controls—were enrolled. All subjects underwent structural volumetric magnetic resonance imaging (MRI) and amyloid PET scans with F-18 florbetaben. Regional standardized uptake value ratios (SUVRs) using the cerebellar cortex as a reference region were obtained using PMOD and MIMneuro.

Results

The SUVRs using both PMOD and MIMneuro showed high discriminatory power between the AD patients and cognitively normal controls. While PMOD and MIMneuro yielded significantly different SUVRs in some brain regions, the two methods had good overall agreement.

Conclusion

MIMneuro provides comparable performance to PMOD without the need to acquire brain MRI. Therefore, MIMneuro might be suitable for clinical use to determine amyloid positivity.

     

The role of serial FDG PET for assessing therapeutic response in patients with cardiac sarcoidosis

Background

The purpose of this study was to determine the feasibility of serial quantitative 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET) to monitor the response of cardiac sarcoidosis to treatment.

Methods and Results

A total of 38 PET scan intervals (54 PET scans) were obtained in 16 patients with cardiac sarcoidosis who underwent serial FDG PET during treatment. FDG-avid lesions of the heart were interpreted quantitatively using 4 PET parameters: maximum standardized uptake value (SUVmax), partial volume corrected mean standardized uptake value (SUVmean), partial volume corrected metabolic volume product (MVP), and global metabolic volume product (gMVP). Clinical response to treatment (improved, stable, or progressive disease) was evaluated by clinical symptoms, NYHA class, and EKG in all the patients. SUVmax, SUVmean, MVP, and gMVP had significantly decreased value on repeat PET in patients who were either stable or showed clinical improvement between two serial PET scans, while none of them had significant change on repeat PET in patients who were clinically worse. Correlation analysis between PET findings and clinical assessment revealed that the changes of SUVmax and SUVmean on repeat PET were negatively correlated with patient’s clinical outcome.

Conclusion

Our results indicated that serial FDG PET is feasible to determine the extent of disease activity and to quantitatively assess the response of cardiac sarcoidosis to therapy.

     

RGD-K5 PET/CT in patients with advanced head and neck cancer treated with concurrent chemoradiotherapy: Results from a pilot study

Background/Aim

We prospectively investigated the potential usefulness of PET using a new tracer targeting integrin αvβ3 (termed RGD-K5) in patients with head and neck cancer (HNC) undergoing definitive concurrent chemoradiotherapy (CCRT).

Patients and Methods

Newly diagnosed patients with locally advanced HNC scheduled for definitive CCRT were eligible. RDG-K5 PET and FDG PET scans were performed at three different time points (baseline, 2 weeks, and 3 months post-treatment).

Results

Nine patients completed all of the three scans, whereas two patients withdrew after two scans only. Uptake of both RGD-K5 and FDG generally decreased following CCRT. However, the observed decrease did not differ significantly between complete responders and non-responders. At 3 months post-treatment, the uptake of both RGD-K5 and FDG at the main tumors was significantly lower in those who achieved complete responses than in those with residual tumors.

Conclusion

RGD-K5 PET has the potential to identify patients with incomplete responses to CCRT.

     

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.

     

<Superscript>18</Superscript>F-FDG PET/CT for the Diagnosis of Malignant and Infectious Complications After Solid Organ Transplantation

Purpose

Infection and malignancy represent two common complications after solid organ transplantation, which are often characterized by poorly specific clinical symptomatology. Herein, we have evaluated the role of ¹⁸F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) in this clinical setting.

Methods

Fifty-eight consecutive patients who underwent FDG PET/CT after kidney, lung or heart transplantation were included in this retrospective analysis. Twelve patients underwent FDG PET/CT to strengthen or confirm a diagnostic suspicion of malignancies. The remaining 46 patients presented with unexplained inflammatory syndrome, fever of unknown origin (FUO), CMV or EBV seroconversion during post-transplant follow-up without conclusive conventional imaging. FDG PET/CT results were compared to histology or to the finding obtained during a clinical/imaging follow-up period of at least 6 months after PET/CT study.

Results

Positive FDG PET/CT results were obtained in 18 (31 %) patients. In the remaining 40 (69 %) cases, FDG PET/CT was negative, showing exclusively a physiological radiotracer distribution. On the basis of a patient-based analysis, FDG PET/CT’s sensitivity, specificity, PPV and NPV were respectively 78 %, 90 %, 78 % and 90 %, with a global accuracy of 86 %. FDG PET/CT was true positive in 14 patients with bacterial pneumonias (n?=?4), pulmonary fungal infection (n?=?1), histoplasmosis (n?=?1), cutaneous abscess (n?=?1), inflammatory disorder (sacroiliitis) (n?=?1), lymphoma (n?=?3) and NSCLC (n?=?3). On the other hand, FDG PET/CT failed to detect lung bronchoalveolar adenocarcinoma, septicemia, endocarditis and graft-versus-host disease (GVHD), respectively, in four patients. FDG PET/CT contributed to adjusting the patient therapeutic strategy in 40 % of cases.

Conclusions

FDG PET/CT emerges as a valuable technique to manage complications in the post-transplantation period. FDG PET/CT should be considered in patients with severe unexplained inflammatory syndrome or FUO and inconclusive conventional imaging or to discriminate active from silent lesions previously detected by conventional imaging particularly when malignancy is suspected.

     

Clinical utility of FDG PET/CT in acute complicated pyelonephritis—results from an observational study

Background

Acute complicated pyelonephritis (ACP) is an upper urinary tract infection associated with coexisting urinary tract abnormalities or medical conditions that could predispose to serious outcomes or treatment failures. Although CT and magnetic resonance imaging (MRI) are frequently used in patients with ACP, the clinical value of ¹⁸F–fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) has not been systematically investigated. This single-center retrospective study was designed to evaluate the potential usefulness of FDG PET/CT in patients with ACP.

Methods

Thirty-one adult patients with ACP who underwent FDG PET/CT were examined. FDG PET/CT imaging characteristics, including tracer uptake patterns, kidney volumes, and extrarenal imaging findings, were reviewed in combination with clinical data and conventional imaging results.

Results

Of the 31 patients, 19 (61%) showed focal FDG uptake. The remaining 12 study participants showed a diffuse FDG uptake pattern. After volumetric approximation, the affected kidneys were found to be significantly enlarged. Patients who showed a focal uptake pattern had a higher frequency of abscess formation requiring drainage. ACP patients showing diffuse tracer uptake patterns had a more benign clinical course. Seven patients had suspected extrarenal coinfections, and FDG PET/CT successfully confirmed the clinical suspicion in five cases. FDG PET/CT was as sensitive as CT in identifying the six patients (19%) who developed abscesses. Notably, FDG PET/CT findings caused a modification to the initial antibiotic regimen in nine patients (29%).

Conclusions

FDG PET/CT may be clinically useful in the assessment of patients with ACP who have a progressive disease course.