Altered biodistribution of [68Ga]Ga-DOTA-TOC during somatostatin analogue treatment

PURPOSE

The need for an interval between the administration of long-acting Somatostatin Receptor Analogues (SSA) and the [68Ga]Ga-DOTA-TATE PET has been questioned based on recent literature in the new EANM guidelines. Here an earlier studies showed that SSA injection immediately before SSTR PET had minimal effect on normal organ and tumor uptake (1). However, data are scarce and there are (small) differences between [68Ga]Ga-DOTA-TATE and [68Ga]Ga-DOTA-TOC binding affinity, and it remains unknown whether these findings can be directly translated to scans with [68Ga]Ga-DOTA-TOC as well. The purpose of this study was to assess the effect of SSA use on the biodistribution in a subsequent [68Ga]Ga-DOTA-TOC PET/CT and compare this intra-individually across several cycles of SSA treatments.

METHODS

Retrospectively, 35 patients with NENs were included. [68Ga]Ga-DOTA-TOC PET at staging and after the 1st and 2nd cycle of SSA were included. SUVmean and SUVmax of blood, visceral organs, primary tumor and two metastases were determined. Also, the interval between SSA therapy and the PET scan was registered.

RESULTS

Treatment with SSA resulted in a significantly higher bloodpool activity and lower visceral tracer uptake. This effect was maintained after a 2nd cycle of SSA therapy. Furthermore, there was an inverse relationship between bloodpool tracer availability and visceral tracer binding and a positive correlation between bloodpool tracer availability and primary tumor tracer uptake. With an interval of up to 5 days, there was a significantly higher bloodpool activity than at longer intervals.

CONCLUSION

Absolute comparison of the SUV on [68Ga]Ga-DOTA-TOC PET should be done with caution as the altered biodistribution of the tracer after SSA treatment should be taken into account. We recommend not to perform a scan within the first 5 days after the injection of lanreotide.

Radiomics for precision medicine: Current challenges, future prospects, and the proposal of a new framework

The advancement of artificial intelligence concurrent with the development of medical imaging techniques provided a unique opportunity to turn medical imaging from mostly qualitative, to further quantitative and mineable data that can be explored for the development of clinical decision support systems (cDSS). Radiomics, a method for the high throughput extraction of hand-crafted features from medical images, and deep learning -the data driven modeling techniques based on the principles of simplified brain neuron interactions, are the most researched quantitative imaging techniques. Many studies reported on the potential of such techniques in the context of cDSS. Such techniques could be highly appealing due to the reuse of existing data, automation of clinical workflows, minimal invasiveness, three-dimensional volumetric characterization, and the promise of high accuracy and reproducibility of results and cost-effectiveness. Nevertheless, there are several challenges that quantitative imaging techniques face, and need to be addressed before the translation to clinical use. These challenges include, but are not limited to, the explainability of the models, the reproducibility of the quantitative imaging features, and their sensitivity to variations in image acquisition and reconstruction parameters. In this narrative review, we report on the status of quantitative medical image analysis using radiomics and deep learning, the challenges the field is facing, propose a framework for robust radiomics analysis, and discuss future prospects.

[Lutetium-177-PSMA radioligand therapy : Consensus within the framework of GKV-funded care between the university hospitals in Aachen, Bonn, Düsseldorf, Essen, and Cologne and the MDK Nordrhein]

In the last 3 years, Lutetium-177 prostate-specific membrane antigen radioligand therapy (Lu-177-PSMA-RLT) has received increasing attention in nuclear medicine as a new form of treatment for castration-resistant metastatic prostate cancer. This therapy combines the radionuclide Lutetium-177, which has been therapeutically used in nuclear medicine for many years, with a molecular target of the transmembrane prostate-specific membrane antigen expressed by prostate cancer cells. Since there are no prospective randomized studies on Lu-177-PSMA-RLT and the question of reimbursement has repeatedly been the subject of review by the MDK Nordrhein (Medischenische Dienst der Krankenversicherung), there was a desire because of the increasing number of patients being treated to clarify under which circumstances Lu-177-PSMA-RLT can be reimbursed by German statutory health insurance. The goals of this article are to help treating physicians understand how this new therapy option works, to integrate it in the overall therapy concept for castration-resistant metastatic prostate cancer, and, above all, to use Lu-177-PSMA-RLT-based on the current data-at the right place in the therapy sequence of castration-resistant metastatic prostate cancer.

Comparison of PET and fMRI activation patterns during declarative memory processes

Aim: In this study neuronal correlates of encoding and retrieval in paired association learning were compared using two different neuroimaging methods: positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Methods: 6 right-handed normal male volunteers took part in the study. Each subject underwent six 0-15-butanol PET scans and an fMRI study comprising four single epochs on a different day. The subjects had to learn and retrieve 12 word pairs which were visually presented (highly imaginable words, not semantically related). Results: Mean recall accuracy was 93% in the PET as well as in the fMRI experiment. During encoding and retrieval we found anterior cingulate cortex activation, and bilateral prefrontal cortex activation in both imaging modalities. Furthermore, we demonstrate the importance of the precuneus in episodic memory. With PET the results demonstrate frontopolar activations whereas fMRI fails to show activations in this area probably due to susceptibility artifacts. In fMRI we found additionally parahippocampal activation and due to the whole-brain coverage cerebellar activation during encoding. The distance between the center-of-mass activations in both modalities was 7.2 ± 6.5 mm. Conclusion: There is a preponderance of commonalities in the activation patterns yielded with fMRI and PET. However, there are also important differences. The decision to choose one or the other neuroimaging modality should among other aspects depend on the study design (single subject vs. group study) and the task of interest.

Internal radionuclide therapy

Aim: Accurate dosimetry must be performed for each patient before therapy with unsealed radionuclides. Recently, the software tool ULMDOS was developed to facilitate planar dosimetric calculations and to support traceability and documentation as a prerequisite for good clinical practice. Here, the extended version of ULMDOS for processing of tomographic data is presented. Methods: ULMDOS is developed in IDL 6.1 (Interactive Data Language) under Windows XP/2000. Serial tomographic data can be loaded in an ECAT7 or DICOM format, and presented as maximum intensity projection. The definition of volumes of interest is supported by various tools (e.g., freehand, isocontour, polygon), region growing, and cluster analysis. Residence times are calculated from fits of the time activity data to exponential functions. Results, discussion: Quantitative 3-dimensional data allow performing a more individualized dosimetry, as problems due to organ overlay, insufficient attenuation and scatter correction in the planar approach can be avoided. For traceability, documentation, retrospective examination and later processing all data can be saved in binary or ASCII format. Dosimetric calculations can be conducted within a single environment, thus it spares the time-consuming transfer of data between different software tools.

Neurocognition and PET

Aim: In cognitive neuroscience regional cerebral blood flow (rCBF) imaging with positron-emission-tomography (PET) is a powerful tool to characterize different aspects of cognitive processes by using different data analysis approaches. By use of an n-back verbal working memory task (varied from 0- to 3-back) we present cognitive subtraction analysis as basic strategy as well as parametric and covariance analyses and discuss the results. Methods: Correlation analyses were performed using the individual performance rate as an external covariate, computing inter-regional correlations, and as network analysis applying structural equation modelling to evaluate the effective connectivity between the involved brain regions. Results: Subtraction analyses revealed a fronto-parietal neuronal network also including the anterior cingulate cortex and the cerebellum. With higher memory load the parametric analysis evidenced linear rCBF increases in prefrontal, pre-motor and inferior parietal areas including the precuneus as well as in the anterior cingulate cortex. The rCBF correlation with the individual performance as external covariate depicted negative correlations in bilateral prefrontal and inferior parietal regions, in the precuneus and the anterior cingulate cortex. The network analysis demonstrated mainly occipito-frontally directed interactions which were predominantly left-hemispheric. Additionally, strong linkages were found between extrastriate and parietal regions as well as within the parietal cortex. Conclusion: The data analysis approaches presented here contribute to an extended and more elaborated understanding of cognitive processes and their different sub-aspects.

Radiation dosimetry and biodistribution of the beta-amyloid plaque imaging tracer 11C-BTA-1 in humans

Aim: [N-methyl-11C]2-(4'-(methylaminophenyl)-benzothiazole (11C-BTA-1) is a thioflavin-T derivative that has been one of the promising PET tracers for imaging of amyloid plaque distribution in the Alzheimer patients brain in vivo. The biodistribution and dosimetry of this tracer in humans is presented and compared to the results of a previous dosimetry and biodistribution study of another thioflavin-T derivative [N-methyl-11C]2-hydroxy-(4'-(methylaminophenyl)- benzothiazole (11C-OH-BTA-1) in baboons. Methods: Five subjects underwent 2D dynamic PET imaging. Source organs were segmented using a semiautomatic algorithm based on clustering. Residence times for each source organ were determined by analytical integration of an exponential fit of the time activity curves. Finally organ doses were estimated using the software OLINDA/EXM. Results: The administration of 286 ± 93 MBq 11C-BTA-1 was well tolerated by all subjects. Effective radiation dose was 4.3 μSv/MBq, range 3.6–5.0 μSv/MBq. In four of the five subjects the liver, in one of the subjects the gallbladder was the critical organ. Conclusion: The radiation burden of a single dose of 300 MBq 11C-BTA-1 is within the accepted limits for research purpose. In contrast to the previous non-human primate study revealing the gallbladder as the critical organ for 11C-6-OH-BTA-1, we found the liver as the critical organ in humans using 11C-BTA-1. Possible explanations may be (1) a reduced bile concentration of 11C-BTA-1 due to the absent OH-group or (2) a different hepatic metabolism of thioflavin derivatives in human and baboon.

Patients with in-stent restenoses

Aims: We compared the intracoronary β-brachytherapy using a liquid rhenium-188 filled balloon with the slow-release, polymer-based, paclitaxel-eluting Taxus-Express stent for treatment of in-stent restenoses. Patients, methods: During the same study period, patients with restenoses in bare-metal stents were either treated with Taxus- Express stents (n = 50) or β-brachytherapy after successful angioplasty (n = 51). For brachytherapy 30 Gy in 0.5 mm tissue depth were administered. The irradiated segment exceeded the traumatized segment 7.5 mm on both sides. Primary endpoint was the minimal lumen diameter (MLD) at the target lesion at six months follow-up. Angiographic follow-up was available in 78% (n = 79/101) and clinical follow-up in all patients. Results: Baseline parameters did not differ statistically. The Taxus-Express stent resulted in a significantly larger MLD and a significantly lower percent diameter stenosis post intervention compared to β-brachytherapy, which both maintained until angiographic follow-up (primary endpoint 2.44 ± 0.74 mm versus 1.73 ± 0.74 mm, p <0.0001). Therefore, Taxus- Express stents were associated with a lower angiographic restenosis rate compared with β-brachytherapy, both for the target lesion (6.1% versus 17.4%) and the total segment (9.1% versus 23.9%). Moreover, use of Taxus-stent was associated with a clinical benefit based on a significantly lower MACE rate compared with β-brachytherapy (p <0.05). Conclusions: Paclitaxel-eluting Taxus- Express stents resulted in superior clinical and angiographic outcomes compared to intracoronary β-brachytherapy with a liquid 188Re filled balloon for treatment of restenosis within a bare-metal stent.

Brain metastasis in lung cancer

FDG-PET/CT is increasingly used in staging of lung cancer as single „one stop shop” method. Aim, patients, methods: We prospectively included 104 neurological asymptomatic patients (65 years, 26% women) with primary diagnosis of lung cancer. In all patients PET/CT including cerebral imaging and cerebral MRI were performed. Results: Diagnosis of brain metastases (BM) was made by PET/CT in 8 patients only (7.7%), by MRI in 22 (21.2%). In 80 patients both PET/CT and MRI showed no BM. In 6 patients (5.8%) BM were detectable on PET/CT as well as on MRI. Exclusive diagnosis of BM by MRI with negative finding on PET/CT was present in 16 patients (15.4%). 2 patients (1.9%) had findings typical for BM on PET/CT but were negative on MRI. With MRI overall 100 BM were detected, with PET/CT only 17 BM (p < 0.01). For the diagnosis of BM PET/CT showed a sensitivity of 27.3%, specificity of 97.6%, positive predictive value of 75% and negative predictive value of 83.3%. BM diameter on PET/CT and MRI were consistent in 43%, in 57% BM were measured larger on MRI. Discussion: Compared to the gold standard of MRI for cerebral staging a considerable number of patients are falsely diagnosed as free from BM by PET/CT. MRI is more accurate than PET/CT for detecting multiple and smaller BM. Conclusion: In patients with a curative option MRI should be performed additionally to PET/CT for definitive exclusion of brain metastases.

Pretherapeutic dosimetry before 131I therapy of benign thyroid disease

Aim: To compare uptake measurements and different methods for the pretherapeutic determination of the effective thyroidal 131I half life (Teff) to the results of posttherapeutic dosimetric measurements. Patients, methods: Retrospective study of 1538 patients who received their first RIT in our department for autonomous thyroid nodules (ATN), autonomous multinodular goiter (AMG) or Graves' disease (GD) between November 1999 and January 2011. Pretherapeutic measurements were performed at any combination of 24 h, 48 h and 6 days after 131I administration. Post-therapy dosimetric measurements were performed in 12 h intervals until discharge. Teff was determined through monoexponential curve fitting. Results: Pretherapeutic Teff values based on measurements at 24 h and 48 h, 24 h and 6 d, 48 h and 6 d as well as on day 24 h, 48 h and 6 d yielded implausible (< 2 d or > 8 d) values for Teff, in 60.4%, 25.7%, 29.1 and 21.4% of available calculations, respectively. The plausible results showed significant, clinically relevant and sometimes considerable overestimations of Teff. Using empirically determined fixed disease specific Teff values resulted in a better congruence between the pre- and posttherapeutic dosimetry results. 24 h measurements were marginally more accurate than 48 h ones in AMG and GD whereas 48 h measurements were marginally more accurate in ATN; these differences are however not clinically relevant. 6 d measurements are clearly less accurate than those after 24 h or 48 h. Conclusion: In ATN, AMG and GD, pretherapeutic dosimetry can be performed by a single uptake measurement at 24 h or 48 h using a fixed, disease specific value for Teff. Additional later measurements do not yield a further clinically relevant contribution to accuracy of pretherapeutic dosimetry.

Quantitative performance evaluation of 124I PET/MRI lesion dosimetry in differentiated thyroid cancer

The aim was to investigate the quantitative performance of ¹²⁴I PET/MRI for pre-therapy lesion dosimetry in differentiated thyroid cancer (DTC). Phantom measurements were performed on a PET/MRI system (Biograph mMR, Siemens Healthcare) using ¹²⁴I and ¹⁸F. The PET calibration factor and the influence of radiofrequency coil attenuation were determined using a cylindrical phantom homogeneously filled with radioactivity. The calibration factor was 1.00  ±  0.02 for ¹⁸F and 0.88  ±  0.02 for ¹²⁴I. Near the radiofrequency surface coil an underestimation of less than 5% in radioactivity concentration was observed. Soft-tissue sphere recovery coefficients were determined using the NEMA IEC body phantom. Recovery coefficients were systematically higher for ¹⁸F than for ¹²⁴I. In addition, the six spheres of the phantom were segmented using a PET-based iterative segmentation algorithm. For all ¹²⁴I measurements, the deviations in segmented lesion volume and mean radioactivity concentration relative to the actual values were smaller than 15% and 25%, respectively. The effect of MR-based attenuation correction (three- and four-segment µ-maps) on bone lesion quantification was assessed using radioactive spheres filled with a K₂HPO₄ solution mimicking bone lesions. The four-segment µ-map resulted in an underestimation of the imaged radioactivity concentration of up to 15%, whereas the three-segment µ-map resulted in an overestimation of up to 10%. For twenty lesions identified in six patients, a comparison of ¹²⁴I PET/MRI to PET/CT was performed with respect to segmented lesion volume and radioactivity concentration. The interclass correlation coefficients showed excellent agreement in segmented lesion volume and radioactivity concentration (0.999 and 0.95, respectively). In conclusion, it is feasible that accurate quantitative ¹²⁴I PET/MRI could be used to perform radioiodine pre-therapy lesion dosimetry in DTC.

Timing of post 131I ablation diagnostic whole body scan in differentiated thyroid cancer patients

Ziel: Beantwortung der Frage, ob drei Monate nach 131I-Ablation als zu früh für eine diagnostische Radioiod-Ganzkörperszintigraphie (dxWBS) bei Patienten mit einem differenzierten Schilddrüsenkarzinom (DTC) anzusehen sind. Patienten, Material, Methode: Daten von 462 DTC-Patienten, die in unserem Klinikum behandelt worden waren, wurden analysiert. Alle Patienten wurden thyreoid ektomiert. Von 129 Patienten waren folgende Daten verfügbar a) eine dxWBS mit gleichzeitiger TSH-stimulierter Thyreoglobulin-Messung, die innerhalb von vier Monaten (max. 120 Tage) nach 131I-Ablation durchgeführt wurde ohne weitere therapeutische Maßnahmen zwischen Ablation und dxWBS, b) eine zweite dxWBS oder 131I-Therapie (rxWBS), die innerhalb von 1,5 Jahren nach Ablation durchgeführt wurde. Ergebnisse: Bei 25/129 Patienten stimmten die Ergebnisse der initialen und weiteren Scans nicht überein: Bei 15 von 54 Patienten (27%) mit einem positiven initialen dxWBS widersprachen diese Ergebnisse dem zweiten dxWBS oder rxWBS. Neue Läsionen wurden bei 10/74 (14%) Patienten mit einem initial negativen dxWBS entdeckt. Eine Diskordanz zwischen dem ersten und weiteren in der Nachsorge gemessenen stimulierten Tg-Werten wurde in 5/129 (4%) der Patienten gefunden: Bei 2/90 (2%) Patienten mit einer negativen ersten stimulierten Tg-Bestimmung wurde nachfolgend ein positives Ergebnis gefunden. Bei 3/29 (10%) Patienten mit einer positiven ersten Bestimmung wurde bei der zweiten Untersuchung ein negatives Ergebnis festgestellt. Schlussfolgerung: Weniger als vier Monate nach 131I-Ablation ist zu früh für eine diagnostische Radioiod-Ganzkörperszintigraphie mit zeitgleich TSH-stimulierter Tg-Messung. Die Ermittlung des richtigen späteren Zeitpunkts erfordert weitere Untersuchungen.

Das Zeitintervall zwischen 131I Ablation und diagnostischer Ganzkörperszintigraphie bei Patienten mit differenziertem Schilddrüsenkarzinom Weniger als vier Monate nach Ablation dürfte zu früh sein

Added value of dedicated axillary hybrid 18F-FDG PET/MRI for improved axillary nodal staging in clinically node-positive breast cancer patients: a feasibility study

Purpose

To investigate the feasibility and potential added value of dedicated axillary 18F-FDG hybrid PET/MRI, compared to standard imaging modalities (i.e. ultrasound [US], MRI and PET/CT), for axillary nodal staging in clinically node-positive breast cancer.

Methods

Twelve patients with clinically node-positive breast cancer underwent axillary US and dedicated axillary hybrid 18F-FDG PET/MRI. Nine of the 12 patients also underwent whole-body PET/CT. Maximum standardized uptake values (SUVmax) were measured for the primary breast tumor and the most FDG-avid axillary lymph node. A positive axillary lymph node on dedicated axillary hybrid PET/MRI was defined as a moderate to very intense FDG-avid lymph node. The diagnostic performance of dedicated axillary hybrid PET/MRI was calculated by comparing quantitative and its qualitative measurements to results of axillary US, MRI and PET/CT. The number of suspicious axillary lymph nodes was subdivided as follows: N0 (0 nodes), N1 (1–3 nodes), N2 (4–9 nodes) and N3 (≥ 10 nodes).

Results

According to dedicated axillary hybrid PET/MRI findings, seven patients were diagnosed with N1, four with N2 and one with N3. With regard to mean SUVmax, there was no significant difference in the primary tumor (9.0 [±5.0] vs. 8.6 [±5.7], p = 0.678) or the most FDG-avid axillary lymph node (7.8 [±5.3] vs. 7.7 [±4.3], p = 0.767) between dedicated axillary PET/MRI and PET/CT. Compared to standard imaging modalities, dedicated axillary hybrid PET/MRI resulted in changes in nodal status as follows: 40% compared to US, 75% compared to T2-weighted MRI, 40% compared to contrast-enhanced MRI, and 22% compared to PET/CT.

Conclusions

Adding dedicated axillary 18F-FDG hybrid PET/MRI to diagnostic work-up may improve the diagnostic performance of axillary nodal staging in clinically node-positive breast cancer patients.

Pharmacokinetic modeling of a novel hypoxia PET tracer [18F]HX4 in patients with non-small cell lung cancer

Background

[¹⁸F]HX4 is a promising new PET tracer developed to identify hypoxic areas in tumor tissue. This study analyzes [¹⁸F]HX4 kinetics and assesses the performance of simplified methods for quantification of [¹⁸F]HX4 uptake.

To this end, eight patients with non-small cell lung cancer received dynamic PET scans at three different time points (0, 120, and 240 min) after injection of 426 ± 72 MBq [¹⁸F]HX4, each lasting 30 min. Several compartment models were fitted to time activity curves (TAC) derived from various areas within tumor tissue using image-derived input functions.

Results

Best fits were obtained using the reversible two-tissue compartment model with blood volume parameter (2T4k+V_B). Simplified measures correlated well with V_T estimates (tumor-to-blood ratio (TBr) R² = 0.96, tumor-to-muscle ratio R² = 0.94, standardized uptake value R² = 0.89).

Conclusions

[¹⁸F]HX4 shows reversible kinetics in tumor tissue: 2T4k+V_B. TBr based on static imaging at 2 or 4 h can be used for quantification of [¹⁸F]HX4 uptake.

Electronic supplementary material

The online version of this article (doi:10.1186/s40658-016-0167-y) contains supplementary material, which is available to authorized users.

Patients with high-risk differentiated thyroid cancer have a lower I-131 ablation success rate than low-risk ones in spite of a high ablation activity

OBJECTIVE

To examine success rates in strictly defined high-risk differentiated thyroid cancer (DTC) patients who received a high-activity (≥5550 MBq) adjuvant postoperative I-131 therapy and compare these to the rates found in highest risk and low-risk patients.

DESIGN

Retrospective database study.

PATIENTS

We examined 377 patients with DTC who received I-131 ablation. Patients with distant metastases were classified as very high risk. Patients with primary tumours >4 cm, extensive extrathyroidal invasion (pT4a or pT4b in accordance with the 7th edition of the TNM system), and patients with ≥5 lymph node metastases or any lateral compartment lymph node metastases were considered high risk. All other patients were considered low risk.

MEASUREMENTS

Ablation success rate at first TSH-stimulated follow-up.

RESULTS

The ablation success rate was 72·6% in low-risk patients, 51·7% in high-risk patients and 13·8% in highest risk patients (all differences P < 0·001). In none of the groups, a significant difference in the initial I-131 activity was found between patients with successful and unsuccessful ablation (low risk: P = 0·16, high risk: P = 0·91 and highest risk: P = 0·48). Furthermore, there was no difference in ablation success between patients who received <5550 MBq and those who received ≥5550 Mbq (low risk: P = 0·31, high risk: P = 0·69 and highest risk: P = 0·22).

CONCLUSIONS

Patients with high-risk DTC have a significantly reduced I-131 ablation success rate compared to low-risk ones in spite of high initial I-131 activities. As successful ablation is prognostically important, efforts should be made to improve outcome in these patients.

The EANM practice guidelines for bone scintigraphy

PURPOSE

The radionuclide bone scan is the cornerstone of skeletal nuclear medicine imaging. Bone scintigraphy is a highly sensitive diagnostic nuclear medicine imaging technique that uses a radiotracer to evaluate the distribution of active bone formation in the skeleton related to malignant and benign disease, as well as physiological processes.

METHODS

The European Association of Nuclear Medicine (EANM) has written and approved these guidelines to promote the use of nuclear medicine procedures of high quality.

CONCLUSION

The present guidelines offer assistance to nuclear medicine practitioners in optimizing the diagnostic procedure and interpreting bone scintigraphy. These guidelines describe the protocols that are currently accepted and used routinely, but do not include all existing procedures. They should therefore not be taken as exclusive of other nuclear medicine modalities that can be used to obtain comparable results. It is important to remember that the resources and facilities available for patient care may vary.

Comparison of diagnostic accuracy of (111)In-pentetreotide SPECT and (68)Ga-DOTATOC PET/CT: A lesion-by-lesion analysis in patients with metastatic neuroendocrine tumours

OBJECTIVES

To compare the diagnostic accuracy of (111)In-pentetreotide-scintigraphy with (68)Ga-DOTATOC-positron emission tomography (PET)/computed tomography (CT) in patients with metastatic-neuroendocrine tumour (NET) scheduled for peptide receptor radionuclide therapy (PRRT). Incremental lesions (ILs) were defined as lesions observed on only one modality.

METHODS

Fifty-three metastatic-NET-patients underwent (111)In-pentetreotide-scintigraphy (24 h post-injection; planar+single-photon emission CT (SPECT) abdomen) and whole-body (68)Ga-DOTATOC-PET/CT. SPECT and PET were compared in a lesion-by-lesion and organ-by-organ analysis, determining the total lesions and ILs for both modalities.

RESULTS

Significantly more lesions were detected on (68)Ga-DOTATOC-PET/CT versus (111)In-pentetreotide-scintigraphy. More specifically, we observed 1,098 lesions on PET/CT (range: 1-105; median: 15) versus 660 on SPECT (range: 0-73, median: 9) (p<0.0001), with 439 PET-ILs (42/53 patients) and one SPECT-IL (1/53 patients). The sensitivity for PET/CT was 99.9 % (95 % CI, 99.3-100.0), for SPECT 60.0 % (95 % CI, 48.5-70.2). The organ-by-organ analysis showed that the PET-ILs were most frequently visualized in liver and skeleton.

CONCLUSION

Ga-DOTATOC-PET/CT is superior for the detection of NET-metastases compared to (111)In-pentetreotide SPECT.

KEY POINTS

Somatostatin receptor PET is superior to SPECT in detecting NET metastases. PET is the scintigraphic method for accurate depiction of NET tumour burden. The sensitivity of PET is twofold higher than the sensitivity of SPECT.

Bone graft scintigraphy. A new diagnostic tool to assess perfusion during surgery

AIM

To evaluate a scintigraphic tool for intraoperative assessment of vascularized bone graft perfusion before and after transplantation.

PATIENTS, METHODS

This pilot study included three patients scheduled for surgical segmental mandibulectomy followed by reconstruction with a vascularized iliac bone graft. A continuous (99m)Tc-pertechnetate infusion was applied selectively arterial into the blood vessel supplying the respective graft before osteotomy as well as after transplantation. Perfusion was analysed by scintigrams acquired using the intraoperative camera systems declipseSPECT and Sentinella. Results were compared qualitatively.

RESULTS

Before harvesting the graft, intraoperative scintigraphy revealed a clearly delineated area of the iliac crest with a relatively homogenous pertechnetate distribution representing good perfusion. After osteotomy, transplantation to the mandibula and re-anastomosis of the nutrient vessels, scintigraphy in all patients showed a moderately inhomogenous distribution pattern of the pertechnetate indicating an adequate perfusion of the bone transplant through the arterial anastomosis.

CONCLUSION

Intraoperative assessment of bone graft perfusion is possible with the imaging systems Sentinella as well as with declipseSPECT using a continuous intra-arterial infusion of 99mTc-pertechnetate.

[Nuclear medicine in Europe: education]

The technical developments that have taken place in the preceding years (PET, hybrid imaging) have changed nuclear medicine. The future cooperation with radiologists will be challenging as well as positioning nuclear medicine in an European context. It can also be expected that education in nuclear medicine will undergo a harmonization process in the states of the European Union. In this paper, we describe how nuclear medicine education is organized in several European countries. We aim to stimulate constructive discussions on the future development of the specialization in nuclear medicine in Germany.

Hard beta and gamma emissions of 124I. Impact on occupational dose in PET/CT

AIM

The hard beta and gamma radiation of 124I can cause high doses to PET/CT workers. In this study we tried to quantify this occupational exposure and to optimize radioprotection.

METHODS

Thin MCP-Ns thermoluminescent dosimeters suitable for measuring beta and gamma radiation were used for extremity dosimetry, active personal dosimeters for whole-body dosimetry. Extremity doses were determined during dispensing of 124I and oral administration of the activity to the patient, the body dose during all phases of the PET/CT procedure. In addition, dose rates of vials and syringes as used in clinical practice were measured. The procedure for dispensing 124I was optimized using newly developed shielding.

RESULTS

Skin dose rates up to 100 mSv/min were measured when in contact with the manufacturer's vial containing 370 MBq of 124I. For an unshielded 5 ml syringe the positron skin dose was about seven times the gamma dose. Before optimization of the preparation of 124I, using an already reasonably safe technique, the highest mean skin dose caused by handling 370 MBq was 1.9 mSv (max. 4.4 mSv). After optimization the skin dose was below 0.2 mSv.

CONCLUSION

The highly energetic positrons emitted by 124I can cause high skin doses if radioprotection is poor. Under optimized conditions occupational doses are acceptable. Education of workers is of paramount importance.

A novel presenilin1 mutation (Q223R) associated with early onset Alzheimer's disease, dysarthria and spastic paraparesis and decreased Abeta levels in CSF

BACKGROUND AND PURPOSE

A novel presenilin1 (PSEN1) mutation associated with dementia and spastic paraplegia in a family with five affected individuals is described. The index patient was a 35-year-old man presenting with cognitive decline, behavioural symptoms, dysarthria, and gait disorder due to spasticity.

METHODS AND RESULTS

Genetic analysis revealed a missense mutation Gln223Arg in exon 7. Initial CSF analysis revealed drastically decreased Abeta42 level despite marginally decreased FDG metabolism.

CONCLUSION

Cerebrospinal fluid biomarker analysis might point towards genetic analysis of PSEN1 in patients with positive family history and age of onset below 60 years.

Association of increase in thymidine uptake relative to tumor cell proliferation in indolent NHLs and DNA repair

11116

Background: Uptake of radiolabeled thymidine (tdR) or its analogs is frequently used to assess tumor cell proliferation as well as tumor DNA repair synthesis after inhibition of tumor cell proliferation with certain drugs. We determined whether the relationship between thymidine (td) uptake and tumor cell proliferation may be different between indolent and aggressive NHLs. Methods: Twenty-four patients with histologically confirmed aggressive (n=16; all DLC) or indolent NHLs (n=8; 7 FL gr I-II, 1 MZL) underwent pretherapy imaging with the td analog 18F-fluorothymidine (FLT) and biopsy to determine the proliferative cell fraction by the Ki-67 index. Tumoral FLT uptake was determined by the maximum standardized uptake values (SUVmax) and correlated with the Ki-67 index. The FLT-SUV to Ki-67 ratio was also compared between indolent and aggressive NHLs. Results: Disproportional increase in FLT-SUVmax relative to tumor cell proliferation was found in indolent NHLs: median %Ki-67 was 5% in indolent vs. 80% in aggressive NHL whereas median FLT-SUVmax was 3.6 vs. 9.4, respectively. The disproportional increase in FLT-SUV in indolent NHLs could not be explained by nonspecific FLT uptake in tumor extracellular space estimated to account for <0.2 SUV unit. Difference in the ratio of FLT-SUVmax to Ki-67 index between indolent and aggressive NHLs was highly significant (1.21 ± 0.77 vs. 0.18± 0.20; P=0.006). These data are in line with a previous study using tdR where the ratios of median tdR (in cpm) to median %-Ki-67 or %-S phase cells in indolent were ∼1.5x those in aggressive NHLs which was associated with relatively increased expression of DNA repair proteins (PCNA) in indolent NHLs (Holte et. al. Acta Oncologica, 1999) Conclusions: Disproportional increase in td uptake relative to %proliferating tumor cells in indolent NHLs likely reflects enhanced DNA repair in quiescent cells or, less likely, constitutively increased Tk1 expression. Studies are underway to determine expression of proteins that, unlike Ki-67, are associated with both DNA repair and replication (e.g., RFA, PCNA). If enhanced DNA repair is confirmed in indolent NHLs this could have major implications with respect to understanding their natural course and treatment options.

No significant financial relationships to disclose.

Molecular imaging of prostate cancer

Prostate carcinoma is the most common non-cutaneous malignancy in males. Imaging of prostatic lesions is of great importance and aids in oncologic management and monitoring of therapy response. Particularly molecular imaging based on positron emission tomography (PET) and single photon emission computerized tomography (SPECT) has great potential. Using radio-labelled molecular probes, these approaches are highly sensitive and can provide key molecular and functional information on tumours. The identification of suitable targets based on unique genetic and biochemical features of cancer lesions is one of the core activities driving progress in molecular imaging of pathological processes. Nowadays, mainly metabolic probes are being used routinely for detection and staging of prostate cancer. The development of new specific receptor ligands and targeted probes and antibodies holds great promise to further enhance the performance of molecular imaging and to further improve the diagnosis and monitoring of prostate cancer.

Integrated FDG PET-CT imaging improves staging in malignant pleural mesothelioma

AIM of this study was to investigate, how often TNM staging is changed in patients with malignant pleural mesothelioma (MPM) by the application of integrated PET-CT compared to computed tomography alone and how often these changes are clinically relevant.

PATIENTS, METHODS

We studied 17 patients (68 +/- 6 years, 8 women) with MPM. Integrated PET-CT scan and histological confirmation were performed in all patients.

RESULTS

Final histological diagnosis confirmed 9 epithelial type, 2 sarcomatoid type and 6 biphasic type MPM. Mean standardized uptake value (SUV) was 5.9 +/- 1.9 in epithelial MPM and 15.1 +/- 10.2 in sarcomatoid MPM. CT and PET-CT revealed discordances in 8/17 (47%) patients in TNM classification with 4/8 (50%) being clinically relevant. PET-CT led to downstaging in 5 (29%) and upstaging in 3 (18%) patients. Mean survival time tended to be higher in the subgroup of patients with lower mean SUV.

CONCLUSIONS

PET-CT seems to be a valuable tool in staging of MPM and leads to discordant findings in almost every second patient compared to CT alone. In many cases these differences are clinically relevant and have therapeutic consequences.

fMRT vor Motorkortexstimulation beim Phantomschmerz

This study deals with the diagnostic value of functional magnetic resonance imaging (fMRI) in a patient with phantom limb pain following traumatic amputation of the right arm. After failure with medication, resection of stump neurinoma, and spinal cord stimulation, fMRI with evidence of cortical reorganization was performed. Tactile stimulation of the perioral region and motor imagery with cranial, tactile stimulation of the stump led to a caudal shift in fMRI activity. Subsequent motor cortex stimulation brought relief from the pain. By detecting cortical reorganization, fMRI contributes to the indication for motor cortex stimulation for phantom pain and aids in electrode positioning.

Does caffeine modulate verbal working memory processes? An fMRI study

To assess the effect of caffeine on the functional MRI signal during a 2-back verbal working memory task, we examined blood oxygenation level-dependent regional brain activity in 15 healthy right-handed males. The subjects, all moderate caffeine consumers, underwent two scanning sessions on a 1.5-T MR-Scanner separated by a 24- to 48-h interval. Each participant received either placebo or 100 mg caffeine 20 min prior to the performance of the working memory task in blinded crossover fashion. The study was implemented as a blocked-design. Analysis was performed using SPM2. In both conditions, the characteristic working memory network of frontoparietal cortical activation including the precuneus and the anterior cingulate could be shown. In comparison to placebo, caffeine caused an increased response in the bilateral medial frontopolar cortex (BA 10), extending to the right anterior cingulate cortex (BA 32). These results suggest that caffeine modulates neuronal activity as evidenced by fMRI signal changes in a network of brain areas associated with executive and attentional functions during working memory processes.

[Systemic therapy approaches in patients with bone metastases of urogenital malignancies]

Bone metastases develop commonly in patients with a variety of urogenital malignancies and are a major cause of morbidity and diminished quality of life in a significant proportion of urogenital carcinoma patients. For example, bone metastases occur in approximately 80% of patients with hormone-refractory prostate cancer and in approximately 25% of patients with renal cell carcinoma. A sufficient and early therapy is crucial since adequate therapy can lead to significant improvements in pain control and function and maintain skeletal integrity. The effective treatment of bone metastases requires multidisciplinary cooperation between urologists, oncologists, surgeons, nuclear medicine physicians and radiation oncologists. Analgesic measures, bisphosphonates, radionuclides, radiation therapy as well as surgical procedures are available. This review will focus mainly on the role of analgetics, bisphosphonates, radionuclides and radiolabelled bisphosphonates in the treatment of bone metastases.

Patients with in-stent restenoses: comparison of intracoronary beta-brachytherapy using a rhenium-188 filled balloon catheter with the polymer-based paclitaxel-eluting taxus-express stent

AIMS

We compared the intracoronary beta-brachytherapy using a liquid rhenium-188 filled balloon with the slow-release, polymer-based, paclitaxel-eluting Taxus-Express stent for treatment of in-stent restenoses.

PATIENTS, METHODS

During the same study period, patients with restenoses in bare-metal stents were either treated with Taxus-Express stents (n = 50) or beta-brachytherapy after successful angioplasty (n = 51). For brachytherapy 30 Gy in 0.5 mm tissue depth were administered. The irradiated segment exceeded the traumatized segment 7.5 mm on both sides. Primary endpoint was the minimal lumen diameter (MLD) at the target lesion at six months follow-up. Angiographic follow-up was available in 78% (n = 79/101) and clinical follow-up in all patients.

RESULTS

Baseline parameters did not differ statistically. The Taxus-Express stent resulted in a significantly larger MLD and a significantly lower percent diameter stenosis post intervention compared to beta-brachytherapy, which both maintained until angiographic follow-up (primary endpoint 2.44 +/- 0.74 mm versus 1.73 +/- 0.74 mm, p < 0.0001). Therefore, Taxus-Express stents were associated with a lower angiographic restenosis rate compared with beta-brachytherapy, both for the target lesion (6.1% versus 17.4%) and the total segment (9.1% versus 23.9%). Moreover, use of Taxus-stent was associated with a clinical benefit based on a significantly lower MACE rate compared with beta-brachytherapy (p < 0.05).

CONCLUSIONS

Paclitaxel-eluting Taxus-Express stents resulted in superior clinical and angiographic outcomes compared to intracoronary beta-brachytherapy with a liquid (188)Re filled balloon for treatment of restenosis within a bare-metal stent.

Radiation dosimetry and biodistribution of the beta-amyloid plaque imaging tracer 11C-BTA-1 in humans

AIM

[N-methyl-(11)C]2-(4'-(methylaminophenyl)-benzothiazole ((11)C-BTA-1) is a thioflavin-T derivative that has been one of the promising PET tracers for imaging of amyloid plaque distribution in the Alzheimer patients brain in vivo. The biodistribution and dosimetry of this tracer in humans is presented and compared to the results of a previous dosimetry and biodistribution study of another thioflavin-T derivative [N-methyl-(11)C]2-hydroxy-(4'-(methylaminophenyl)-benzothiazole ((11)C-OH-BTA-1) in baboons.

METHODS

Five subjects underwent 2D dynamic PET imaging. Source organs were segmented using a semiautomatic algorithm based on clustering. Residence times for each source organ were determined by analytical integration of an exponential fit of the time activity curves. Finally organ doses were estimated using the software OLINDA/EXM.

RESULTS

The administration of 286 +/- 93 MBq (11)C-BTA-1 was well tolerated by all subjects. Effective radiation dose was 4.3 microSv/MBq, range 3.6-5.0 microSv/MBq. In four of the five subjects the liver, in one of the subjects the gallbladder was the critical organ.

CONCLUSION

The radiation burden of a single dose of 300 MBq (11)C-BTA-1 is within the accepted limits for research purpose. In contrast to the previous non-human primate study revealing the gallbladder as the critical organ for (11)C-6-OH-BTA-1, we found the liver as the critical organ in humans using (11)C-BTA-1. Possible explanations may be (1) a reduced bile concentration of (11)C-BTA-1 due to the absent OH-group or (2) a different hepatic metabolism of thioflavin derivatives in human and baboon.

Radiosynthesis and evaluation of [11C]BTA-1 and [11C]3'-Me-BTA-1 as potential radiotracers for in vivo imaging of beta-amyloid plaques

AIM

To evaluate the in vitro and in vivo characteristics of [N-methyl-(11)C]2-(4'-(methylaminophenyl)-benzothiazole ([(11)C]BTA-1) as well as [N-methyl-(11)C]2-(3'-methyl-4'-(methylamino)phenyl)-benzothiazole ([(11)C]3'-Me-BTA-1) as diagnostic markers of amyloid-beta (Abeta) in Alzheimer's disease (AD).

MATERIAL, METHODS

Brain uptake and clearance was determined in wild-type mice. Binding affinities (K(i)) of [(11)C]BTA-1 and [(11)C]3'-Me-BTA-1 for aggregated Abeta(1-40) fibrils were assessed. Autoradiography was performed on brain sections of AD patients. To demonstrate binding specificity in vivo BTA-1 was injected i.p. in transgenic mice (Tg2576). Brain sections were analysed consecutively. Additionally, a [(11)C]BTA-1 PET study of an AD patient and a healthy control was performed.

RESULTS

In mice brain uptake and clearance of [(11)C]BTA-1 is compatible with the half life of (11)C (2 min: 12.7 % ID/g; 30 min: 4.6% ID/g). In contrast clearance rate of [(11)C]3'-Me-BTA-1 is too slow (2 min 4% ID/g; 30 min 12% ID/g) to achieve sufficient clearance of free and non specifically bound radioactivity. K(i) of [(11)C]BTA-1 is 11 nmol/l and that of [(11)C]3'-Me-BTA-1 27 nmol/l. Both radioligands label Abeta selectively and specifically in AD patients and transgenic mice in vitro. The in vivo stained brain sections show a labelling of Abeta plaques. The AD patient has a higher prefrontal, parietal and striatal [(11)C]BTA-1 accumulation than the healthy control. Metabolite analysis revealed approximately 75% intact [(11)C]BTA-1 after 30min in plasma.[(11)C]BTA-1 is favourable for in vivo imaging of Abeta due to its rapid brain entry, sufficient clearance and good binding affinity for Abeta.

CONCLUSION

The ability to label Abeta plaques in vivo in human subjects supports the suitability of [(11)C]BTA-1 as a plaque imaging agent.

Improved non-invasive T-Staging in non-small cell lung cancer by integrated 18F-FDG PET/CT

AIM

In this prospective study, reliability of integrated (18)F-FDG PET/CT for staging of NSCLC was evaluated and compared to MDCT or PET alone.

PATIENTS, METHODS

240 patients (pts) with suspected NSCLC were examined using PET/CT. Of those patients 112 underwent surgery comprising 80 patients with NSCLC (T1 n = 26, T2 n = 37, T3 n = 11, T4 n = 6). Imaging modalities were evaluated independently.

RESULTS

MDCT, PET and PET/CT diagnosed the correct T-stage in 40/80 pts (50%; CI: 0.39-0.61), 40/80 pts (50%; CI: 0.39-0.61) and 51/80 pts (64%; CI: 0.52-0.74), respectively, whereas equivocal T-stage was found in 15/80 pts (19%; CI: 0.11-0.19), 12/80 pts (15%; CI: 0.08-0.25) and 4/80 pts (5%; CI: 0.01-0.12), respectively. With PET/CT, T-stage was more frequently correct compared to MDCT (p = 0.003) or PET (p = 0.019). Pooling stages T1/T2, T-stage was correctly diagnosed with MDCT, PET and PET/CT in 54/80 pts (68%; CI: 0.56-0.78), 56/80 pts (70%; CI: 0.59-0.80) and 65/80 pts (81%; CI: 0.71-0.89). T3 stage was most difficult to diagnose. T3 tumors were correctly diagnosed with MDCT in 2/11 pts (18%; CI: 0.02-0.52) versus 0/11 pts (0%; CI: 0.00-0.28) with PET and 5/11 pts (45%; CI: 0.17-0.77) with PET/CT. In all imaging modalities, there were no equivocal findings for T4 tumors. Of these, MDCT found the correct tumor stage in 4/6 pts (67%; CI: 0.22-0.95), PET in 3/6 pts (50%; CI: 0.12-0.88) and PET/CT in 5/6 pts (83%; CI: 0.36-0.99).

CONCLUSION

Integrated PET/CT was significantly more accurate for T-staging of NSCLC compared to MDCT or PET alone. The advantages of PET/CT are especially pronounced combining T1- and T2-stage as well as in advanced tumors.