Prevention of activated brown adipose tissue on 18F-FDG-PET scans of young lymphoma patients: results of an ancillary study within the EuroNet-PHL-C2 trial

Activated brown fat (aBAT) is known to affect the evaluation of 18F-FDG PET scans, especially in young patients. The aim of this study was to determine factors influencing the occurrence of aBAT, and to investigate the effectiveness of the two preventive measures, warming and beta-blocker (propranolol) administration. Five-hundred-twenty-eight 18F-FDG-PET scans of 241 EuroNet-PHL-C2 trial patients from 41 nuclear medicine departments in Germany and Czech Republic were screened for aBAT. The occurrence of aBAT was analyzed with patient characteristics (age, sex, body mass index, predisposition to aBAT), weather data at the day of 18F-FDG PET scanning as well as the preventive measures taken. Potentially important factors from univariate analyses were included into a logistic regression model. Warming as a preventive measure was used in 243 18F-FDG-PET scans, propranolol was administered in 36, warming and propranolol were combined in 84, and no preventive measures were taken in 165 scans. Whereas age, sex and body mass index had no clear impact, there was an individual predisposition to aBAT. Logistic regression model revealed that the frequency of aBAT mainly depends on the outside temperature (p = 0.005) and can be effectively reduced by warming (p = 0.004), the administration of unselective beta-blocker or the combination of both. Warming is a simple, cheap and non-invasive method to reduce the frequency of aBAT. However, the effect of warming decreases with increasing outside temperatures. Administration of propranolol seems to be equally effective and provides advantages whenever the positive effect of warming is compromised. The combination of both preventive measures could have an additive effect.

Interplay of tau and functional network connectivity in progressive supranuclear palsy: a [18F]PI-2620 PET/MRI study

PURPOSE

Progressive supranuclear palsy (PSP) is primary 4-repeat tauopathy. Evidence spanning from imaging studies indicate aberrant connectivity in PSPs. Our goal was to assess functional connectivity network alterations in PSP patients and the potential link between regional tau-burden and network-level functional connectivity using the next-generation tau PET tracer [¹⁸F]PI-2620 and resting-state functional MRI (fMRI).

MATERIAL AND METHODS

Twenty-four probable PSP patients (70.9 ± 6.9 years, 13 female), including 14 Richardson syndrome (RS) and 10 non-RS phenotypes, underwent [¹⁸F]PI-2620 PET/MRI imaging. Distribution volume ratios (DVRs) were estimated using non-invasive pharmacokinetic modeling. Resting-state fMRI was also acquired in these patients as well as in thirteen older non-AD MCI reference group (64 ± 9 years, 4 female). The functional network was constructed using 141 by 141 region-to-region functional connectivity metrics (RRC) and network-based statistic was carried out (connection threshold p < 0.001, cluster threshold pFDR < 0.05).

RESULTS

In total, 9870 functional connections were analyzed. PSPs compared to aged non-AD MCI reference group expressed aberrant connectivity evidenced by the significant NBS network consisting of 89 ROIs and 118 connections among them (NBS mass 4226, pFDR < 0.05). Tau load in the right globus pallidus externus (GPe) and left dentate nucleus (DN) showed significant effects on functional network connectivity. The network linked with increased tau load in the right GPe was associated with hyperconnectivity of low-range intra-opercular connections (NBS mass 356, pFDR < 0.05), while the network linked with increased tau load in the left cerebellar DN was associated with cerebellar hyperconnectivity and cortico-cerebellar hypoconnectivity (NBS mass 517, pFDR < 0.05).

CONCLUSIONS

PSP patients show altered functional connectivity. Network incorporating deep gray matter structures demonstrate hypoconnectivity, cerebellum hyperconnectivity, while cortico-cortical connections show variable changes. Tau load in the right GPe and left DN is associated with functional networks which strengthen low-scale intra-opercular and intra-cerebellar connections and weaken opercular-cerebellar connections. These findings support the concept of tau load-dependent functional network changes in PSP, by that providing evidence for downstream effects of neuropathology on brain functionality in this primary tauopathy.

Use of PET-CT in diagnostic workup of periprosthetic infection of hip and knee joints: significance in detecting additional infectious focus

Introduction

The diagnosis and management of periprosthetic knee and hip infections as well as the identification and management of possible additional infectious foci is of great importance for successful therapy. This study analyses the importance of ¹⁸F deoxyglucose PET-CT (PET-CT) in the identification of additional infectious focus and subsequent impact on management of periprosthetic infection (PPI).

Material and methods

A retrospective analysis of the clinical data and findings in the period from January 2008 to December 2018 was carried out. One hundred and four patients with in-hospital treatment due to PPI of a hip or knee joint were identified and included in this study. All patients underwent a standardized clinical examination and further surgical and antibiotic therapy. The reevaluation of performed PET-CTs was specifically carried out with regard to the local PPI or detection of secondary foci.

Results

PET-CT successfully verified the PPI in 84.2% of the patients. A total of 78 possible additional foci were detected in PET-CT in 56 (53.8%) of the examined patients. Predilection sites for possible secondary foci were joints (42.3%), pulmonary (15.4%), ear-nose-throat (15.4%), spine (11.5%), and the musculocutaneous tissues (11.5%). Fifty-four positive PET-CT findings were confirmed clinically with need of additional adequate treatment.

Conclusion

PET-CT is a valuable diagnostic tool to confirm periprosthetic joint infection. At the same time, the whole-body PET/CT may detect additional foci of infection with impact on subsequent treatment strategy. PET was of special value in detecting infections at distant locations far from the primary infected joint in significant number. These distant infection locations can be potential cause of a re-infection. This clearly reflects the need of their diagnosis.

Whole-body [18F]-FDG-PET/MRI for staging of pediatric non-Hodgkin lymphoma: first results from a single-center evaluation

Aim

In 2015, the revised International Pediatric Non-Hodgkin Lymphoma Staging System was published. It mentions [¹⁸F]-FDG-PET/MRI as the latest method to perform whole-body imaging. However, supporting data are pending. Our aim was to investigate the performance of whole-body [¹⁸F]-FDG-PET/MRI in pediatric non-Hodgkin lymphoma patients by using a limited number of MRI sequences.

Materials and methods

Ten pediatric patients with histologically proven non-Hodgkin lymphoma underwent whole-body [¹⁸F]-FDG-PET/MRI at staging. The retrospective analysis included three steps: First, [¹⁸F]-FDG-PET and MR scans were evaluated separately by a nuclear medicine physician and a pediatric radiologist. Nineteen nodal and two extranodal regions as well as six organs were checked for involvement. Second, discrepant findings were reviewed together in order to reach consensus. Third, [¹⁸F]-FDG-PET/MRI findings were correlated with the results of other clinical investigations.

Results

Of the 190 lymph node regions evaluated, four were rated controversial. Consensus was reached by considering metabolic, functional and morphologic information combined. Concordantly, [¹⁸F]-FDG-PET and MRI detected Waldeyer’s ring involvement in two patients whose Waldeyer’s ring was negative on clinical assessment. In four patients MRI showed pleural effusion. However, in only two of them an increased glucose metabolism as a reliable sign of pleural involvement was detectable. In six patients [¹⁸F]-FDG-PET and MRI detected skeletal lesions although bone marrow biopsy was positive in only one of them.

Conclusion

Despite the small number of cases evaluated, whole-body [¹⁸F]-FDG-PET turned out to be a valuable tool for staging of pediatric non-Hodgkin lymphoma.

Posterior wall acetabular fracture fixation: A mechanical analysis of fixation methods

Stable, anatomical fixation of acetabular fractures gives the best chance of successful outcome, while penetration of the acetabular articular surface with screws is associated with poor outcomes. Spring plates are an alternative to interfragmentary lag screws when penetration is a concern. A mechanical study comparing fracture stability and construct stiffness of three fixation methods for posterior wall acetabular fractures with transverse comminutions was performed. The three fixation methods tested were a posterior wall rim plate, a posterior wall buttress plate with separate lag screws and a posterior wall plate with two spring plates. Nine samples were tested, three for each fixation method. Two-dimensional motion analysis was used to measure fracture fragment displacement and construct stiffness. After two 6000 cycle-loading protocols, to a maximum 1.5 kN, the mean fracture displacement was 0.154 mm for the rim plate model, 0.326 mm for the buttress plate and 0.254 mm for the spring plate model. Mean maximum displacement was significantly less for the rim plate fixation than the buttress plate (p = 0.015) and spring plate fixation (p = 0.02). The rim plate was the stiffest construct 10,962 N/mm, followed by the spring plate model 5637 N/mm and the buttress plate model 4882 N/mm. Based on data obtained in this study, where possible a rim plate with interfragmentary lag screws should be used for isolated posterior wall fractures as this is the stiffest and most stable construct. When this method is not possible, spring plate fixation is a safe and a superior alternative to a posterior buttress plate method.

Only strongly enhanced residual FDG uptake in early response PET (Deauville 5 or qPET ≥ 2) is prognostic in pediatric Hodgkin lymphoma: Results of the GPOH-HD2002 trial

PURPOSE

In 2014, we published the qPET method to quantify fluorodeoxyglucose positron emission tomography (FDG-PET) responses. Analysis of the distribution of the quantified signals suggested that a clearly abnormal FDG-PET response corresponds to a visual Deauville score (vDS) of 5 and high qPET values ≥ 2. Evaluation in long-term outcome data is still pending. Therefore, we analyzed progression-free survival (PFS) by early FDG-PET response in a subset of the GPOH-HD2002 trial for pediatric Hodgkin lymphoma (PHL).

PATIENTS/METHODS

Pairwise FDG-PET scans for initial staging and early response assessment after two cycles of chemotherapy were available in 93 PHL patients. vDS and qPET measurement were performed and related to PFS.

RESULTS

Patients with a qPET value ≥ 2.0 or vDS of 5 had 5-year PFS rates of 44%, respectively 50%. Those with qPET values < 2.0 or vDS 1 to 4 had 5-year PFS rates of 90%, respectively 80%. The positive predictive value of FDG-PET response assessment increased from 18% (9%; 33%) using a qPET threshold of 0.95 (vDS ≤ 3) to 30% (13%; 54%) for a qPET threshold of 1.3 (vDS ≤ 4) and to 56% (23%; 85%) when the qPET threshold was ≥ 2.0 (vDS 5). The negative predictive values remained stable at ≥92% (CI: 82%; 98%).

CONCLUSION

Only strongly enhanced residual FDG uptake in early response PET (vDS 5 or qPET ≥ 2, respectively) seems to be markedly prognostic in PHL when treatment according to the GPOH-HD-2002 protocol is given.

MRI-Based Individual 3D Region-of-Interest Atlases of the Human Brain

Objectives: Introduction of a new atlas-based method for analyzing functional data which takes into account the variability of individual human brains and the partial volume effects of functional emission computed tomography images in complex anatomical 3D regions, as well as describing the underlying multi-modal image processing principles.

Methods: 3D atlas extraction is done directly by automated segmentation of individual magnetic resonance images of the patient’s head. This is done in two steps: voxel-based classification of T1-weighted images for tissue differentiation (low-level processing) is followed by knowledge-based analysis of the classified images for extraction of 3D anatomical regions (high-level processing). For atlas-based quantification of co-registered functional images, 3D anatomical regions can be convoluted with an idealized point spread function of the emission computed tomography system, after which a partial volume-dependent threshold can be determined.

Results: Quantitative evaluation studies, based on 50 realistic software head phantoms and 24 image data sets obtained from healthy subjects and patients, show low misclassification rates and stable results for the neural network-based classification approach (mean ± SD 3.587 ± 0.466%, range 2.726-4.927%) as well as for the adjustable parameters of the knowledge-based approach. Computation time is <5 min for classification, <1 min for most of the extraction algorithms. The influence of the partial volume-dependent threshold is shown for an activation study.

Conclusions: This new method allows 3D atlas generation without the need to warp individual image data to an anatomical or statistical brain atlas. Going beyond the purely tissue-oriented approach, partial volume effects of emission computed tomography images can be analyzed in complex anatomical 3D regions.

Einfluß morphologischer Veränderungen auf Durchblutung und Stoffwechsel bei zerebraler Mikroangiopathie

51 Patienten mit zerebraler Mikroangiopathie wurden mittels Kernspintomographie, 18FDG-PET und 99mTc-HMPAO-SPECT untersucht. Die genaue Zuordnung funktioneller zu den morphologischen Befunden wurde durch ein spezielles Kopf-halterungssystem für PET, SPECT- und KST-Untersuchungen hergestellt. Patienten mit weniger als vier lakunären Infarkten (LI) und ohne bis geringfügigen Deep White Matter Lesions (DWML) im KST wiesen keine signifikant veränderten Werte für rMRGIu und rCBF in grauer oder weißer Substanz auf im Vergleich zu Patienten mit vier oder mehr LI und ausgedehnten DWML. Eine semiquantitative Einteilung der Atrophie (A: keine bis geringfügige; B: mäßige bis schwere) erbrachte für B) im Vergleich zu A) signifikant erniedrigte rCBF- und rMRGIu-Werte in grauer und weißer Substanz. Somit sind bei Patienten mit ZMA nur die Hirnatrophie, jedoch nicht die charakteristischen LI und DWML mit einer meßbaren Erniedrigung von rCBF und rMRGIu korreliert.

A Method of Correlating and Merging Cerebral Morphology and Function by a Special Head Holder

Ein spezielles Kopfhalterungssystem wird als Voraussetzung zur Erzeugung und korrelativen Verarbeitung topographisch identischer morphologischer und funktioneller Bilddaten vorgestellt. Es ist an die verschiedenen Modalitäten (MRI, PET, SPECT) adaptierbar und basiert auf einer kommerziellen thermoplastischen Kopfmaske. Eine erwärmte flexible Form dieses Thermoplasts wird dazu verwendet, eine individuelle Kopfmaske für alle Modalitäten zu formen. Damit wird eine Fixierung des Patienten während der Messungen gewährleistet. Diese Methode garantiert auch eine exakte Repositionierung und damit gleiche Schnittorientierung der rekonstruierten Bilder. Durch Fusion der Hirnaußenkonturen oder der korrespondierenden Tomogramme MRI vs. PET oder MRI vs. SPECT wurde die Genauigkeit getestet: Sie betrug transaxial: <2,0 mm und axial: <3,0 mm bei Patientenstudien mit MRI-Schichtdicke von 6,0 mm.

KST und Onkoszintigraphie mit 99mTc-MIBI in der Nachsorge des Schilddrüsenkarzinoms

Mit der KST und der MIBI-Onkoszintigraphie stehen zwei neue Methoden für die Nachsorge des differenzierten Schilddrüsenkarzinoms zur Verfügung. In der vorliegenden Studie wurde ihre klinische Eignung bei 21 Patienten mit und 34 Patienten ohne Rezidivverdacht im Vergleich zu Sonographie, Radiojodszintigraphie und hTg-Bestimmung geprüft. Es zeigte sich, daß die KST zwar die höchste Sensitivität für lokoregionäre Metastasen besitzt (100%), ein diagnostischer Zugewinn jedoch nur bei mediastinalen Herden erzielt werden konnte. Die MIBI-Onkoszintigraphie hatte eine geringere Trefferquote (67%), doch erlaubte sie aufgrund ihrer hohen Spezifität (93,5%) eine sichere Differenzierung zwischen reaktiv vergrößerten und metastatisch befallenen Lymphknoten; sie bietet sich daher bei fraglichen Befunden als einfache Alternative zur aufwendigeren, mit einem Absetzen der TSH-suppressiven Hormonmedikation verbundenen Radiojodszintigraphie an. Als Screening zur Erkennung von Tumorrezidiven bewährte sich die hTg-Bestimmung unter Zugrundelegung einer oberen Normgrenze von 3 ng/ml (Richtigkeit: 100%).

Bestimmung von Einflußgrößen für den Therapieerfolg der Radioiodtherapie bei Patienten mit Morbus Basedow

Ziel der Studie war es, zu prüfen, inwieweit der Erfolg einer Radioiodtherapie (RIT) des Morbus Basedow (MB) von verschiedenen Parametern (Schilddrüsenvolumen [SDVol], Funktion, TRAK, Thyreostase, Therapiedosis, 131l-Uptake, effektive Halbwertszeit) abhängt. Methode: Bei 78 Patienten mit gesichertem MB wurden 626 ± 251 MBq 131 lod oral zur Ablation der Schilddrüse appliziert. 3 Monate nach RIT wurden 60 Patienten kontrolliert. Ergebnisse: Bei Patienten mit einer Hyperthyreose oder TRAK <11 U/l zu Beginn der RIT wurden eine signifikant niedrigere Therapiedosis bzw. Halbwertszeit gefunden als bei nichthyperthyreoten Patienten bzw. Patienten mit TRAK ≤11 U/l. Patienten mit einem SDVol ≤25 ml zeigten signifikant niedrigere 131l-Uptakewerte unter Therapie, jedoch signifikant höhere Relativuptakewerte (131l- Uptake/SDVol) als solche mit SDVol <25 ml. Alle Therapieversager wurden während der RIT thyreostatisch behandelt, sie wiesen im Mittel signifikant niedrigere Therapiedosen und Relativuptakewerte sowie signifikant höhere SdVol als Therapieerfolge auf. Durch die RIT reduzierte sich das SDVol der Patienten um 44%, wobei Versager eine signifikant geringere Volumenreduktion aufwiesen. Patienten mit einer Therapiedosis ≤250 Gy zeigten signifikant schlechtere Therapieresultate als solche mit <250 Gy, nur ein Versager erreichte mehr als 250 Gy, während immerhin 50% der Versager <200 Gy (aber >250 Gy) erreichten. Die Anwendung multivariater Analysen (MANOVA und Faktorenanalysen) ergab die Thyreostase als den entscheidenden Negativfaktor für den Erfolg einer RIT. Schlußfolgerung: Aufgrund der gehäuften Therapieversager bei Patienten mit Thyreostase empfehlen wir daher für diese Patienten eine Erhöhung der Zieldosis auf 250 Gy.

Untersuchungen zum Einfluß von »Ecstasy« auf den zerebralen Glukosemetabolismus: eine 18-FDG-PET-Studie

Ziel: In der vorliegenden Studie sollte die Akutwirkung des »Ecstasy«- Analogons MDE (3,4-Methylendioxyethamphetamin) auf den zerebralen Glukosemetabolismus (rMRGIu) gesunder Probanden untersucht werden. Methode: In einer randomisierten Doppelblindstudie wurden 16 gesunde Probanden ohne Drogenanamnese mittels 18-FDG-PET 110-120 min nach oraler Verabreichung von 2 mg/kg KG MDE (n = 8) oder Plazebo (n = 8) untersucht. Zwei Minuten vor Injektion des Radio- pharmazeutikums startend erfolgte über insgesamt 32 min eine konstante kognitive Stimulation über ein Wortrepetitionsparadigma, um konstante und vergleichbare mentale Bedingungen während der zerebralen 18-FDG-Aufnahme zu gewährleisten. Die Darstellung der Indivi- dualanatomie erfolgte anhand T1-gewichteter 3D-flash MRT mit anschließender manueller Regionalisierung in 108 Regions-of-Interest und PET/MRT Overlay. Absolute Quantifizierung der rMRGIu sowie Normierung auf den Globalmetabolismus mit anschließendem Vergleich MDE versus Plazebo mittels U-Test nach Mann und Whitney. Ergebnisse: Gegenüber der Plazebo-Gruppe fand sich unter MIDE keine signifikante Änderung der globalen MRGIu (MDE: 41,8± 11,1 μmol/min/100 g, Placebo: 50,1 ± 18,1 μmol/min/100 g, p = 0,298). Die normierten metabolischen Daten zeigten eine signifikante Minderung der rMRGIu im beidseitigen Frontalkortex: links frontal posterior (-7,1%, p <0,05) und rechts präfrontal superior (-4,6 %, p <0,05). Signifikante Steigerungen der rMIRGIu fanden sich dagegen im beidseitigen Zerebellum (rechts: + 10,1%, p <0,01; links: +7,6 %, p <0,05) sowie im rechten Putamen (+6,2%, p <0,05). Schlußfolgerung: In der vorliegenden Studie konnten unter dem Akuteinfluß des »Ecstasy«-Analogons MDE neuro- metabolische Veränderungen im Sinne einer fronto-striato-cerebellären Dysbalance nachgewiesen werden, die Parallelen zu sowohl anderen psychotropen Substanzen als auch verschiedenen endogenen Psychosen aufweisen.

Altered Relationships Between rCBF in Different Brain Regions of Never-Treated Schizophrenics

Aim of this study was to investigate the relations between regiona cerebral blood flow (rCBF) of different brain regions in acute schizophrenia and following neuroleptic treatment.

Methods: Twenty-two never-treated, acute schizophrenic patients were examined with HMPAO brain SPECT and assessed psychopathological-ly, and reexamined following neuroleptic treatment (over 96.8 days) and psychopathological remission. rCBF was determined by region/cerebel-lar count quotients obtained from 98 irregular regions of interest (ROIs), summed up to 11 ROIs on each hemisphere. In acute schizophrenics, interregional rCBF correlations of each ROI to every other ROI were compared to the interregional correlations following neuroleptic treatment and to those of controls.

Results: All significant correlations of rCBF ratios of different brain regions were exclusively positive in controls and patients. In controls, all ROIs of one hemisphere except the mesial temporal ROI correlated significantly to its contralateral ROI. Each hemisphere showed significant frontal-temporal correlations, as well as cortical-subcortical and some cortico-limbic. In contrast, in acute schizophrenics nearly every ROI correlated significantly with every other ROI, without a grouping or relation of the rCBF of certain ROIs as in controls. After neuroleptic treatment and clinical improvement, this diffuse pattern of correlations remained.

Conclusions: These results indicate differences in the neuronal interplay between regions in schizophrenic and healthy subjects. In never-treated schizophrenics, diffuse interregional rCBF correlations can be seen as a sign of change and dysfunction of the systems regulating specificity and diversity of the neuronal functions. Neuroleptic therapy and psychopathologic remission showed no normalizing effect on interregional correlations.

One-year Follow-up of Neuropsychology, MRI, rCBF and Glucose Metabolism (rMRGlu) in Cerebral Microangiopathy

Background: MRI shows lacunar infarctions (LI), deep white matter lesions (DWML) and atrophy in cerebral microangiopathy, which is said to lead to vascular dementia. In a first trial series on 57 patients with confirmed pure cerebral microangiopathy (without concomitant macroangiopathy), neuropsychological impairment and (where present) brain atrophy correlated with decreased rCBF and rMRGlu. LI and DWML did not correlate with either neuropsychological impairment or decreased rCBF/rMRGIu. This study was done one year later to detect changes in any of the study parameters. Methods: 26 patients were re-examined for rCBF, rMRGlu, LI, DWML, atrophy and neuropsychological performance (7 cognitive, 3 mnestic, 4 attentiveness tests). Using a special head holder for exact repositioning, rCBF (SPECT) and rMRGlu (PET) were measured and imaged slice by slice. White matter/cortex were quantified using MRI-defined ROIs. Results: After one year the patients did not show significant decreases in rCBF or rMRGlu either in cortex or in white matter (p >0.05), nor did any patient show LI, DWML or atrophy changes on MRI. There were no significant neuropsychological decreases (p >0.05). Conclusions: Cerebral microangiopathy ought to show progressive neuropsychological, functional (rCBF, rMRGlu) and morphological deterioration over periods >1 year. It is unlikely that direct cortical damage (e.g., incomplete infarction) is responsible for neuropsychological impairment since one-year follow-up of our patients revealed no progression of brain atrophy or any other cortical damage.

Rolle der Positronen-Emissions-Tomographie (PET) und Single-Photon-Emissions-Tomographie (SPECT) bei der sogenannten »Multiple Chemical Sensitivity« (MCS)

Die funktionell bildgebenden Verfahren SPECT und PET werden zunehmend genutzt, um die Existenz eines Syndroms der erworbenen Chemikalienüberempfindlichkeit »Multiple Chemical Sensitivity« (MCS) nachzuweisen. In der Folge spielen SPECT und PET-Befunde auch im Rahmen von Gutachten bei Berufskrankheiten-Anzeigen als Beweismittel eine große Rolle. In der vorliegenden Arbeit wird die zu diesem Thema existierende Literatur einer kritischen Betrachtung unterzogen. Die Autoren kommen zu dem Schluß, daß die gegenwärtig verfügbaren Daten nicht ausreichen, um die Existenz eines solchen Syndroms nachzuweisen. Die niedrige Spezifität der beschriebenen Veränderungen macht es sehr schwierig, einen kausalen Zusammenhang zu der toxischen Exposition herzustellen, und schränkt den Wert von PET und vor allem SPECT bei gutachterlichen Fragestellungen in diesem Zusammenhang ein.

F-18-FDG Positron Imaging in Oncological Patients: Gamma Camera Coincidence Detection versus Dedicated PET

Aim of the present study was to investigate the feasibility of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) imaging in oncological patients with a dual head gamma camera modified for coincidence detection (MCD). Methods: Phantom studies were done to determine lesion detection at various lesion-to-background ratios, system sensitivity and spatial resolution. Thirty-two patients with suspected or known malignant disease were first studied with a dedicated full-ring PET system (DPET) applying measured attenuation correction and subsequently with an MCD system without attenuation correction. MCD images were first interpreted without knowledge of the DPET findings. In a second reading, MCD and DPET were evaluated simultaneously. Results: The phantom studies revealed a comparable spatial resolution for DPET and MCD (5.9 × 6.3 × 4.2 mm vs. 5.9 × 6.5 × 6.0 mm). System sensitivity of MCD was less compared to DPET (91 cps/Bq/ml/cmF0V vs. 231 cps/ Bq/ml/cmFOv). At a lesion-to-background ratio of 4:1, DPET depicted a minimal phantom lesion of 1.0 cm in diameter, MCD a minimal lesion of 1.6 cm. With DPET, a total of 91 lesions in 27 patients were classified as malignant. MCD without knowledge of DPET results revealed increased FDG uptake in all patients with positive DPET findings. MCD detected 72 out of 91 DPET lesions (79.1 %). With knowledge of the DPET findings, 11 additional lesions were detected (+12%). MCD missed lesions in six patients with relevance for staging in two patients. All lesions with a diameter above 18 mm were detected. Conclusion: MCD FDG imaging yielded results comparable to dedicated PET in most patients. However, a considerable number of small lesions clearly detectable with DPET were not detected by MCD alone. Therefore, MCD cannot yet replace dedicated PET in all oncological FDG studies. Further technical refinement of this new method is needed to improve image quality (e.g. attenuation correction).

Comparison of Different Methods for Attenuation Correction in Brain PET: Influence on the Calculation of the Metabolic Glucose Rate

Ziel: Für die Korrektur des Effektes der im Körpergewebe gestreuten oder absorbierten Photonen (Schwächungskorrektur) existieren bei der Positronen-Emissionstomographie (PET) verschiedene methodische Ansätze. Die vorliegende Arbeit untersucht den Einfluß der kalten (KT), heißen (PIT), segmentierten Transmission (ST) sowie eines rechnerischen Verfahrens (RV) auf die Schwächungskorrektur anhand der absoluten Bestimmung des regionalen zerebralen Glukosemetabolismus (rMRGIu). Methodik: 6 Patienten mit unterschiedlichen zerebralen Erkrankungen wurden mit einem ECAT Exact 922/47 unter Ruhebedingungen untersucht. Die durch die KT, PIT, RV und ST schwächungskorrigierten Daten wurden dann zur Beurteilung des regionalen Glukosemetabolismus in 16 ROIs (regions of interest) absolut quantifiziert. Ergebnisse: Bis auf drei Regionen (temporookzipital links und rechts sowie parietookzipital rechts) konnte kein signifikanter Unterschied des mit Hilfe der absoluten Quantifizierung in 16 ROIs ermittelten Glukosemetabolismus zwischen der KT und dem RV festgestellt werden. Im Gegensatz zum RV wurde sowohl bei der PIT als auch bei der ST in allen 16 ROIs ein signifikant niedrigerer Wert der regionalen zerebralen Glukoseutilisation gegenüber der KT nachgewiesen. Aufgrund dieser Resultate ergibt sich sowohl in der linken als auch in der rechten Hirnhälfte eine kontinuierliche Abnahme der metabolischen Werte (rMRGIu) in der Reihenfolge KT, RV, PIT und ST. Der globale, zerebrale Glukosemetabolismus zeigte keinen signifikanten Unterschied zwischen der KT und dem RV (p = 0,2489), während mit PIT (p = 0,03) und ST (p = 0,03) ein signifikant erniedrigter Glukosemetabolismus gegenüber der-KT nachzuweisen war. Schlußfolgerung: Bei den für die zerebralen PET-Studien am Patienten durchgeführten Schwächungskorrekturverfahren läßt sich bis auf drei Regionen quantitativ kein signifikanter Unterschied zwischen KT und RV nachweisen. Die rMRGIu der durch PIT und ST schwächungskorrigierten Bilder sind signifikant niedriger als in KT korrigierten Aufnahmen. Um eine zerebrale PET-Akquisition zu verkürzen, erscheint für die klinische Routine das RV als Alternative zur KT am besten geeignet.

Clinical applications of single photon emission tomography in neuromedicine

This article gives in his second part a critical review of the clinical applications of SPECT with perfusion markers and receptor ligands in dementing disorders and psychosis. In addition this review discusses clinical applications of SPECT investigations with perfusion markers in inflammatory diseases of the central nervous system and in brain trauma.

Clinical applications of single photon emission tomography in neuromedicine

Single photon emission tomography is, because of its availability and the relatively low costs, the functional imaging modality currently most widely used for clinical applications in the brain. Beside the application of radiopharmaceuticals for the assessment of regional cerebral blood flow there is an increasing clinical use of more selective SPECT-radiopharmaceuticals, like amino acid analogs or receptor ligands. This article gives in his first part a critical review of the clinical applications of SPECT in neuro-oncology, epilepsy, basal ganglia disorders and cerebrovascular disease.

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Optimizing ventilation-perfusion lung scintigraphy: Parting with planar imaging

Aim of the study was to introduce and verify a ventilation-perfusion (V/Q) acquisition protocol that incorporates new developments in scintigraphy in order to allow for a more balanced comparison with other diagnostic procedures. Methods: In 103 patients suspect of having pulmonary embolism, V/Q scans were acquired exclusively with SPECT technique. Ventilation was done with ultrafine aerosol. Planar images in eight directions were reconstructed through addition of three consecutive SPECT projections. Three referees examined the scans in regard to type, localization, and extent of V/Q defects. Results: Using this protocol, significantly more defects, especially of subsegmental size, were detected (p <0.Q1). Sensitivity, and diagnostic accuracy were also significantly improved (p <0.01) to 0.96, and 0.99, respectively. Furthermore, kappa values were increased up to 0.82 - a relevant enhancement in the ability to precisely localize V/Q defects. Conclusion: In conclusion this protocol provides high-resolution tomographic scans as well as high-quality planar images within a short acquisition time. Due to the significant increase in lesion detection, sensitivity, diagnostic accuracy, and anatomical localization of defects, it is a substantial improvement in the diagnosis of pulmonary embolism that will put V/Q scintigraphy on a par with other tomographic methods.

Characterization of radioiodine therapy failures in Graves’ disease

Aim of this study was a characterization of radioiodine therapy (RIT) failures in Graves’ disease without simultaneous Carbimazole. Method: 226 patients with a confirmed diagnosis of Graves’ disease received 686.8 ± 376.4 MBq of iodine-131 orally for thyroid ablation. Target dose was 250 Gy. All patients were followed up for 6 months. Therapy failures were compared with successes regarding possible influencing variables initial thyroid volume, thyroid function, immune activity (TRAb), 1-131 uptake, effective half-life, absorbed energy dose, age and gender. Results: 212 of 226 patients (93.8%) were treated successfully, 14 (6.2%) showed a hyperthyroidism relapse within 6 months which required a second radioiodine therapy. A success rate of 92.5% (62/67) could also be achieved with 67 patients who were hyperthyroid at the time of RIT. Compared to the therapy successes, the 14 failures achieved significantly lower absorbed doses (223.8 ±76.6 Gyvs. 285.2 ±82.1 Gy, ρ <0.005), but with no significant differences regarding age, thyroid volume, function or TRAb (all ρ >0.2). Of the 14 failures, η = 8 reached an absorbed dose <200 Gy and η = 1 a dose <250 Gy, although 5 of the failures reached an absorbed dose of >250 Gy. Stepwise logistic regression revealed only absorbed energy dose as a variable significantly influencing therapy success (p <0.005), but no influence of initial thyroid volume, function, TRAb value, age (all ρ >0.2) or gender (p = 0.13). Two-tailed Fisher’s exact test showed no significant influence of gender on success rates (failures/successes: male 1 /36, female 13/176, ρ = 0.48). Conclusions: Except for the absorbed energy dose, no other significant variable influencing the outcome of radioiodine therapy in Graves’ disease without simultaneous Carbimazole could be found. It should be noted, though, that 5 therapy failures (2.2%) reached an absorbed energy dose of >250 Gy.

FDG-PET in Hodgkin lymphoma

The high negative predictive value of FDG-PET in therapy control of Hodgkin lymphoma is proven by the data acquired up to now. Thus, the analysis of the HD15 trial has shown that consolidation radiotherapy might be omitted in PET negative patients after effective chemotherapy. Further response adapted therapy guided by PET seems to be a promising approach in reducing the toxicity for patients undergoing chemotherapy. The criteria used for the PET interpretation have been standardized by the German study groups for Hodgkin lymphoma patients and will be reevaluated in the current studies.

Comparison of volumetric and functional parameters in simultaneous cardiac PET/MR: feasibility of volumetric assessment with residual activity from prior PET/CT

OBJECTIVE

To compare cardiac left ventricular (LV) parameters in simultaneously acquired hybrid fluorine-18-fluorodeoxyglucose ([18F] FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) in patients with residual tracer activity of upstream PET/CT.

METHODS

Twenty-nine patients (23 men, age 58±17 years) underwent cardiac PET/MRI either directly after a non-cardiac PET/CT with homogenous cardiac [18F] FDG uptake (n=20) or for viability assessment (n=9). Gated cardiac [18F] FDG PET and cine MR sequences were acquired simultaneously and evaluated blinded to the cross-imaging results. Image quality (IQ), end-diastolic (LVEDV), end-systolic volume (LVESV), ejection fraction (LVEF) and myocardial mass (LVMM) were measured. Pearson correlation and intraclass correlation coefficient (ICC), regression and a Bland-Altman analysis were assessed.

RESULTS

Except LVMM, volumetric and functional LV parameters demonstrated high correlations (LVESV: r=0.97, LVEDV: r=0.95, LVEF: r=0.91, LVMM: r=0.87, each p<0.05), but wide limits of agreement (LOA) for LVEDV (-25.3-82.5ml); LVESV (-33.1-72.7ml); LVEF (-18.9-14.8%) and LVMM (-78.2-43.2g). Intra- and interobserver reliability were very high (ICC≥0.95) for all parameters, except for MR-LVEF (ICC=0.87). PET-IQ (0-3) was high (mean: 2.2±0.9) with significant influence on LVMM calculations only.

CONCLUSION

In simultaneously acquired cardiac PET/MRI data, LVEDV, LVESV and LVEF show good agreement. However, the agreement seems to be limited if cardiac PET/MRI follows PET/CT and only the residual activity is used.

KEY POINTS

• [ 18 F] FDG PET-MRI is feasible with residual [ 18 F] FDG activity in patients with homogenous cardiac uptake. • Cardiac volumes and function assessed by PET/MRI show good agreement. • LVEDV and LVESV are underestimated; PET overestimates LVMM and LVEF. • Cardiac PET and MRI data correlate better when acquired simultaneously than sequentially. • PET and MRI should not assess LV parameters interchangeably.

Maternal immune activation results in complex microglial transcriptome signature in the adult offspring that is reversed by minocycline treatment

Maternal immune activation (MIA) during pregnancy has been linked to an increased risk of developing psychiatric pathologies in later life. This link may be bridged by a defective microglial phenotype in the offspring induced by MIA, as microglia have key roles in the development and maintenance of neuronal signaling in the central nervous system. The beneficial effects of the immunomodulatory treatment with minocycline on schizophrenic patients are consistent with this hypothesis. Using the MIA mouse model, we found an altered microglial transcriptome and phagocytic function in the adult offspring accompanied by behavioral abnormalities. The changes in microglial phagocytosis on a functional and transcriptional level were similar to those observed in a mouse model of Alzheimer's disease hinting to a related microglial phenotype in neurodegenerative and psychiatric disorders. Minocycline treatment of adult MIA offspring reverted completely the transcriptional, functional and behavioral deficits, highlighting the potential benefits of therapeutic targeting of microglia in psychiatric disorders.

[Amyloid positron-emission-tomography with [18 F]-florbetaben in the diagnostic workup of dementia patients]

BACKGROUND

To this day the definite diagnosis of Alzheimer's disease still relies on post-mortem histopathological detection of neurofibrillary tangles and beta-amyloid deposits. Amyloid positron emission tomography (PET) is a new diagnostic tool that enables the in vivo quantification of pathological beta-amyloid deposits. The aim of the current study was to evaluate to what extent ¹⁸F-florbetaben-PET (FBB-PET) influences the diagnosis of patients with dementia.

MATERIAL AND METHODS

Imaging with FBB-PET was performed on 33 patients from our outpatient department for cognitive neurology. Beforehand all patients underwent a comprehensive clinical, neuropsychiatric and laboratory examination as well as imaging by means of magnetic resonance imaging (MRI) and fluorodeoxyglucose-PET. The working diagnoses before and after FBB-PET imaging were compared.

RESULTS

17 out of 33 patients were scored as FBB-PET positive. In four cases the initial diagnosis had to be changed to Alzheimer's disease (three cases) and cerebral amyloid angiopathy (one case) due to the positive FBB-PET scan. 16 patients showed a negative FBB-PET scan. In three patients the initial diagnosis of Alzheimer's disease could be ruled out due to the negative FBB-PET scan. Overall, in 7 out of 33 examined patients the initial diagnosis had to be changed because of the findings of the FBB-PET scan. In 24 patients the initial diagnosis was confirmed by the results of the FBB-PET scan.

CONCLUSION

Amyloid-PET is currently no standard procedure in the diagnosis of dementia; however, it can be a helpful additional diagnostic tool when used according to the "Appropriate Use Criteria" and the S3 guidelines on dementia in cases of unclear clinical presentation, atypically early age of onset as well as in patients with persistent or progressive unexplained mild cognitive impairment. By facilitating early diagnosis amyloid-PET imaging allows patient selection for therapeutic drug trials.

Emotional eating and in vivo norepinephrine transporter availability in obesity: A [11 C]MRB PET pilot study

OBJECTIVE

Emotional eating (EE) has been linked to norepinephrine dysfunction. Therefore, we aimed to investigate the relationship between EE and norepinephrine transporter (NET) availability.

METHOD

Ten severely obese individuals (body mass index (BMI) 42.4 ± 3.7 kg/m² ) and ten non-obese, healthy controls (BMI 23.9 ± 2.5 kg/m² ) matched for age and sex were studied using (S,S)-[¹¹ C]-O-methylreboxetine ([¹¹ C]MRB) positron emission tomography (PET). Kinetic modeling of regional tissue time activity curves was performed using multilinear reference tissue model 2 (MRTM2, with the occipital cortex as a reference region) to estimate binding potential based on individual PET-MR coregistration. To test for associations of EE and NET availability, participants completed the EE subscale of the Dutch Eating Behavior Questionnaire before scanning.

RESULTS

Obese individuals and non-obese, healthy controls did not significantly differ regarding EE scores and regional NET availability. For obese individuals only, correlative data analyses pointed to a sinoidal distribution pattern as a higher degree of EE related to lower NET availability in the locus coeruleus and to higher NET availability in the left thalamus.

DISCUSSION

These results indicate that central in vivo NET availability is altered in EE of individuals with obesity. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2017; 50:152-156).

Imaging of cerebral α4β2* nicotinic acetylcholine receptors with (-)-[(18)F]Flubatine PET: Implementation of bolus plus constant infusion and sensitivity to acetylcholine in human brain

The positron emission tomography (PET) radioligand (-)-[(18)F]flubatine is specific to α4β2(⁎) nicotinic acetylcholine receptors (nAChRs) and has promise for future investigation of the acetylcholine system in neuropathologies such as Alzheimer's disease, schizophrenia, and substance use disorders. The two goals of this work were to develop a simplified method for α4β2(⁎) nAChR quantification with bolus plus constant infusion (B/I) (-)-[(18)F]flubatine administration, and to assess the radioligand's sensitivity to acetylcholine fluctuations in humans. Healthy human subjects were imaged following either bolus injection (n=8) or B/I (n=4) administration of (-)-[(18)F]flubatine. The metabolite-corrected input function in arterial blood was measured. Free-fraction corrected distribution volumes (VT/fP) were estimated with modeling and graphical analysis techniques. Next, sensitivity to acetylcholine was assessed in two ways: 1. A bolus injection paradigm with two scans (n=6), baseline (scan 1) and physostigmine challenge (scan 2; 1.5mg over 60min beginning 5min prior to radiotracer injection); 2. A single scan B/I paradigm (n=7) lasting up to 240min with 1.5mg physostigmine administered over 60min beginning at 125min of radiotracer infusion. Changes in VT/fP were measured. Baseline VT/fP values were 33.8±3.3mL/cm(3) in thalamus, 12.9±1.6mL/cm(3) in cerebellum, and ranged from 9.8 to 12.5mL/cm(3) in other gray matter regions. The B/I paradigm with equilibrium analysis at 120min yielded comparable VT/fP values with compartment modeling analysis of bolus data in extrathalamic gray matter regions (regional means <4% different). Changes in VT/fP following physostigmine administration were small and most pronounced in cortical regions, ranging from 0.8 to 4.6% in the two-scan paradigm and 2.8 to 6.5% with the B/I paradigm. These results demonstrate the use of B/I administration for accurate quantification of (-)-[(18)F]flubatine VT/fP in 120min, and suggest possible sensitivity of (-)-[(18)F]flubatine binding to physostigmine-induced changes in acetylcholine levels.

Impact of attenuation correction on clinical [(18)F]FDG brain PET in combined PET/MRI

Background

In PET/MRI, linear photon attenuation coefficients for attenuation correction (AC) cannot be directly derived, and cortical bone is, so far, usually not considered. This results in an underestimation of the average PET signal in PET/MRI. Recently introduced MR-AC methods predicting bone information from anatomic MRI or proton density-weighted zero-time imaging may solve this problem in the future. However, there is an ongoing debate if the current error is acceptable for clinical use and/or research.

Methods

We examined this feature for [¹⁸F] fluorodeoxyglucose (FDG) brain PET in 13 patients with clinical signs of dementia or movement disorders who subsequently underwent PET/CT and PET/MRI on the same day. Multiple MR-AC approaches including a CT-derived AC were applied.

Results

The resulting PET data was compared to the CT-derived standard regarding the quantification error and its clinical impact. On a quantitative level, −11.9 to +2 % deviations from the CT-AC standard were found. These deviations, however, did not translate into a systematic diagnostic error. This, as overall patterns of hypometabolism (which are decisive for clinical diagnostics), remained largely unchanged.

Conclusions

Despite a quantitative error by the omission of bone in MR-AC, clinical quality of brain [¹⁸F]FDG is not relevantly affected. Thus, brain [¹⁸F]FDG PET can already, even now with suboptimal MR-AC, be utilized for clinical routine purposes, even though the MR-AC warrants improvement.

Sex differences in serotonin-hypothalamic connections underpin a diminished sense of emotional well-being with increasing body weight

BACKGROUND/OBJECTIVES

The neurobiological mechanisms linking obesity to emotional distress related to weight remain largely unknown.

PARTICIPANTS/METHODS

Here we combined positron emission tomography, using the serotonin transporter (5-HTT) radiotracer [(11)C]-3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile, with functional connectivity magnetic resonance imaging, the Beck Depression Inventory (BDI-II) and the Impact of Weight on Quality of Life-Lite questionnaire (IWQOL-Lite) to investigate the role of central serotonin in the severity of depression (BDI-II), as well as in the loss of emotional well-being with body weight (IWQOL-Lite).

RESULTS

In a group of lean to morbidly obese individuals (n=28), we found sex differences in the 5-HTT availability-related connectivity of the hypothalamus. Males (n=11) presented a strengthened connectivity to the lateral orbitofrontal cortex, whereas in females (n=17) we found strengethened projections to the ventral striatum. Both regions are known as reward regions involved in mediating the emotional response to food. Their resting-state activity correlated positively to the body mass index (BMI) and IWQOL-Lite scores, suggesting that each region in both sexes also underpins a diminished sense of emotional well-being with body weight. Contrarily to males, we found that in females also the BDI-II positively correlated with the BMI and by trend with the activity in ventral striatum, suggesting that in females an increased body weight may convey to other mood dimensions than those weight-related ones included in the IWQOL-Lite.

CONCLUSIONS

This study suggests sex differences in serotonin-hypothalamic connections to brain regions of the reward circuitry underpinning a diminished sense of emotional well-being with an increasing body weight.

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tübingen, Germany

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".

Simultaneous [18F]FDG-PET/MRI: Correlation of Apparent Diffusion Coefficient (ADC) and Standardized Uptake Value (SUV) in Primary and Recurrent Cervical Cancer

Objectives

Previous non–simultaneous PET/MR studies have shown heterogeneous results about the correlation between standardized uptake values (SUVs) and apparent diffusion coefficients (ADCs). The aim of this study was to investigate correlations in patients with primary and recurrent tumors using a simultaneous PET/MRI system which could lead to a better understanding of tumor biology and might play a role in early response assessment.

Methods

We included 31 patients with histologically confirmed primary (n = 14) or recurrent cervical cancer (n = 17) who underwent simultaneous whole-body ¹⁸F-FDG-PET/MRI comprising DWI. Image analysis was performed by a radiologist and a nuclear physician who identified tumor margins and quantified ADC and SUV. Pearson correlations were calculated to investigate the association between ADC and SUV.

Results

92 lesions were detected. We found a significant inverse correlation between SUV_max and ADC_min (r = -0.532, p = 0.05) in primary tumors as well as in primary metastases (r = -0.362, p = 0.05) and between SUV_mean and ADC_min (r = -0.403, p = 0.03). In recurrent local tumors we found correlations for SUV_max and ADC_min (r = -0.747, p = 0.002) and SUV_mean and ADC_min (r = -0.773, p = 0.001). Associations for recurrent metastases were not significant (p>0.05).

Conclusions

Our study demonstrates the feasibility of fast and reliable measurement of SUV and ADC with simultaneous PET/MRI. In patients with cervical cancer we found significant inverse correlations for SUV and ADC which could play a major role for further tumor characterization and therapy decisions.

The central nervous norepinephrine network links a diminished sense of emotional well-being to an increased body weight

OBJECTIVES

The neurobiological mechanisms linking obesity to emotional distress remain largely undiscovered.

METHODS

In this pilot study, we combined positron emission tomography, using the norepinephrine transporter (NET) tracer [(11)C]-O-methylreboxetine, with functional connectivity magnetic resonance imaging, the Beck depression inventory (BDI), and the impact of weight on quality of life-Lite questionnaire (IWQOL-Lite), to investigate the role of norepinephrine in the severity of depression (BDI), as well as in the loss of emotional well-being with body weight (IWQOL-Lite).

RESULTS

In a small group of lean-to-morbidly obese individuals (n=20), we show that an increased body mass index (BMI) is related to a lowered NET availability within the hypothalamus, known as the brain's homeostatic control site. The hypothalamus displayed a strengthened connectivity in relation to the individual hypothalamic NET availability to the anterior insula/frontal operculum, as well as the medial orbitofrontal cortex, assumed to host the primary and secondary gustatory cortex, respectively (n=19). The resting-state activity in these two regions was correlated positively to the BMI and IWQOL-Lite scores, but not to the BDI, suggesting that the higher the resting-state activity in these regions, and hence the higher the BMI, the stronger the negative impact of the body weight on the individual's emotional well-being was.

CONCLUSIONS

This pilot study suggests that the loss in emotional well-being with weight is embedded within the central norepinephrine network.

Combined PET/MRI: Multi-modality Multi-parametric Imaging Is Here: Summary Report of the 4th International Workshop on PET/MR Imaging; February 23-27, 2015, Tübingen, Germany

This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from February 23 to 27, 2015. Specifically, we summarise the three days of invited presentations from active researchers in this and associated fields augmented by round table discussions and dialogue boards with specific topics. These include the use of PET/MRI in cardiovascular disease, paediatrics, oncology, neurology and multi-parametric imaging, the latter of which was suggested as a key promoting factor for the wider adoption of integrated PET/MRI. Discussions throughout the workshop and a poll taken on the final day demonstrated that attendees felt more strongly that PET/MRI has further advanced in both technical versatility and acceptance by clinical and research-driven users from the status quo of last year. Still, with only minimal evidence of progress made in exploiting the true complementary nature of the PET and MRI-based information, PET/MRI is still yet to achieve its potential. In that regard, the conclusion of last year's meeting "the real work has just started" still holds true.

Current status and future role of brain PET/MRI in clinical and research settings

Hybrid PET/MRI systematically offers a complementary combination of two modalities that has often proven itself superior to the single modality approach in the diagnostic work-up of many neurological and psychiatric diseases. Emerging PET tracers, technical advances in multiparametric MRI and obvious workflow advantages may lead to a significant improvement in the diagnosis of dementia disorders, neurooncological diseases, epilepsy and neurovascular diseases using PET/MRI. Moreover, simultaneous PET/MRI is well suited to complex studies of brain function in which fast fluctuations of brain signals (e.g. related to task processing or in response to pharmacological interventions) need to be monitored on multiple levels. Initial simultaneous studies have already demonstrated that these complementary measures of brain function can provide new insights into the functional and structural organization of the brain.

Interaction of thyroid hormone with brown adipose tissue

Brown adipose tissue (BAT) plays an important role in regulating core-body temperature in various species including man. [18F]FDGPET/ CT imaging first revealed the presence of metabolically active BAT depots and that decreased BAT function is associated with various metabolic conditions. Thyroid hormone (TH) in concert with sympathetic nervous system signalling (SNS) stimulates BAT thermogenesis and thyroid disorders result in dysfunctional BAT. Currently, research is focussing not only on BAT regulation but also on browning of white adipose tissue (WAT) to BAT beige adipose tissue (BeAT) in order to develop novel treatments for human obesity and related conditions. While [18F]FDG-PET/ CT imaging is continuing to provide valuable insights into BAT and BeAT function in health and disease, there is a pressing need to develop alternative radiotracers that reliably track their activity in vivo. As a result it is expected that preclinical micro PET/CT investigations of BAT and BeAT will gain in prominence.

The aim of this short review is to i) describe fundamentals in BAT biology, ii) highlight some of the clinical and preclinical studies performed on humans and rodents with a focus on TH, BAT and PET/CT, and iii) bridge these data with our own studies within the DFG thyroid transact priority program.

Interaction of thyroid hormone with brown adipose tissue. Lessons learned from PET-CT

Brown adipose tissue (BAT) plays an important role in regulating core-body temperature in various species including man. [18F]FDG-PET/CT imaging first revealed the presence of metabolically active BAT depots and that decreased BAT function is associated with various metabolic conditions. Thyroid hormone (TH) in concert with sympathetic nervous system signalling (SNS) stimulates BAT thermogenesis and thyroid disorders result in dysfunctional BAT. Currently, research is focussing not only on BAT regulation but also on browning of white adipose tissue (WAT) to BAT beige adipose tissue (BeAT) in order to develop novel treatments for human obesity and related conditions. While [18F]FDG-PET/CT imaging is continuing to provide valuable insights into BAT and BeAT function in health and disease, there is a pressing need to develop alternative radiotracers that reliably track their activity in vivo. As a result it is expected that preclinical micro PET/CT investigations of BAT and BeAT will gain in prominence. The aim of this short review is to i) describe fundamentals in BAT biology, ii) highlight some of the clinical and preclinical studies performed on humans and rodents with a focus on TH, BAT and PET/CT, and iii) bridge these data with our own studies within the DFG thyroid transact priority program.

Radioligand imaging of α4β2* nicotinic acetylcholine receptors in Alzheimer's disease and Parkinson's disease

The α4β2* nicotinic acetylcholine receptors (α4β2*-nAChR) are highly abundant in the human brain. As neuromodulators they play an important role in cognitive functions such as memory, learning and attention as well as mood and motor function. Post mortem studies suggest that abnormalities of α4β2*-nAChRs are closely linked to histopathological hallmarks of Alzheimer's disease (AD), such as amyloid aggregates/oligomers and tangle pathology and of Parkinson's disease (PD) such as Lewy body pathology and the nigrostriatal dopaminergic deficit. In this review we summarize and discuss nicotinic receptor imaging findings of 2-[18F]FA-85380 PET, [11C]nicotine PET and 5-[123I]IA-85380 SPECT studies investigating α4β2*-nAChR binding in vivo and their relationship to mental dysfunction in the brain of patients with AD and patients out of the spectrum of Lewy body disorders such as PD and Lewy body dementia (DLB). Furthermore, recent developments of novel α4β2*-nAChR-specific PET radioligands, such as (-)[18F]Flubatine or [18F]AZAN are summarized. We conclude that α4β2*-nAChR-specific PET might become a biomarker for early diagnostics and drug developments in patients with AD, DLB and PD, even at early or prodromal stages.