Surgical radioguidance with beta-emitting radionuclides; challenges and possibilities: A position paper by the EANM.

Radioguidance that makes use of ß-emitting radionuclides is gaining in popularity and could have potential to strengthen the range of existing radioguidance techniques. While there is a strong tendency to develop new PET radiotracers, due to favorable imaging characteristics and the success of theranostics research, there are practical challenges that need to be overcome when considering use of ß-emitters for surgical radioguidance. In this position paper, the EANM identifies the possibilities and challenges that relate to the successful implementation of ß-emitters in surgical guidance, covering aspects related to instrumentation, radiation protection, and modes of implementation.

Peptide receptor radionuclide therapy for neuroendocrine tumors in Germany: first results of a multi-institutional cancer registry.

Peptide receptor radionuclide therapy is an effective treatment option for patients with well-differentiated somatostatin receptor-expressing neuroendocrine tumors. However, published data result mainly from retrospective monocentric studies. We initiated a multi-institutional, prospective, board-reviewed registry for patients treated with peptide receptor radionuclide therapy in Germany in 2009. In five centers, 297 patients were registered. Primary tumors were mainly derived from pancreas (117/297) and small intestine (80/297), whereas 56 were of unknown primary. Most tumors were well differentiated with median Ki67 proliferation rate of 5% (range 0.9-70%). Peptide receptor radionuclide therapy was performed using mainly yttrium-90 and/or lutetium-177 as radionuclides in 1-8 cycles. Mean overall survival was estimated at 213 months with follow-up between 1 and 230 months after initial diagnosis, and 87 months with follow-up between 1 and 92 months after start of peptide receptor radionuclide therapy. Median overall survival was not yet reached. Subgroup analysis demonstrated that best results were obtained in neuroendocrine tumors with proliferation rate below 20%. Our results indicate that peptide receptor radionuclide therapy is an effective treatment for well- and moderately differentiated neuroendocrine tumors irrespective of previous therapies and should be regarded as one of the primary treatment options for patients with somatostatin receptor-expressing neuroendocrine tumors.

Positron emission tomography has a high negative predictive value for progression or early relapse for patients with residual disease after first-line chemotherapy in advanced-stage Hodgkin lymphoma.

In the HD15 trial of the German Hodgkin Study Group, the negative predictive value (NPV) of positron emission tomography (PET) using [(18)F]-fluorodeoxyglucose in advanced-stage Hodgkin lymphoma (HL) was evaluated. A total of 817 patients were enrolled and randomly assigned to receive BEACOPP-based chemotherapy. After completion of chemotherapy, residual disease measuring more than or equal to 2.5 cm in diameter was assessed by PET in 311 patients. The NPV of PET was defined as the proportion of PET(-) patients without progression, relapse, or irradiation within 12 months after PET review panel. The progression-free survival was 96% for PET(-) patients (95% confidence interval [CI], 94%-99%) and 86% for PET(+) patients (95% CI, 78%-95%, P = .011). The NPV for PET in this analysis was 94% (95% CI, 91%-97%). Thus, consolidation radiotherapy can be omitted in PET(-) patients with residual disease without increasing the risk for progression or early relapse compared with patients in complete remission. The impact of this finding on the overall survival at 5 years must be awaited. Until then, response adapted therapy guided by PET for HL patients seems to be a promising approach that should be further evaluated in clinical trials. This trial is registered at http://isrctn.org study as #ISRCTN32443041.

In vitro experimental (211)At-anti-CD33 antibody therapy of leukaemia cells overcomes cellular resistance seen in vivo against gemtuzumab ozogamicin.

PURPOSE: Monoclonal anti-CD33 antibodies conjugated with toxic calicheamicin derivative (gemtuzumab ozogamicin, GO) are a novel therapy option for acute myeloid leukaemia (AML). Key prognostic factors for patients with AML are high CD33 expression on the leukaemic cells and the ability to overcome mechanisms of resistance to cytotoxic chemotherapies, including drug efflux or other mechanisms decreasing apoptosis. Alpha particle-emitting radionuclides overwhelm such anti-apoptotic mechanisms by producing numerous DNA double-stranded breaks (DSBs) accompanied by decreased DNA repair. METHODS: We labelled anti-CD33 antibodies with the alpha-emitter (211)At and compared survival of leukaemic HL-60 and K-562 cells treated with the (211)At-labelled antibodies, GO or unlabelled antibodies as controls. We also measured caspase-3/7 activity, DNA fragmentation and necrosis in HL-60 cells after treatment with the different antibodies or with free (211)At. RESULTS: The mean labelling ratio of (211)At-labelled antibodies was 1:1,090 +/- 364 (range: 1:738-1:1,722) in comparison to 2-3:1 for GO. Tumour cell binding of (211)At-anti-CD33 was high in the presence of abundant CD33 expression and could be specifically blocked by unlabelled anti-CD33. (211)At-anti-CD33 decreased survival significantly more than did GO at comparable dilution (1:1,000). No significant differences in induction of apoptosis or necrosis or DNA DSB or in decreased survival were observed after (211)At-anti-CD33 (1:1,090) versus GO (1:1) treatment. CONCLUSION: Our results suggest that (211)At is a promising, highly cytotoxic radioimmunotherapy in CD33-positive leukaemia and kills tumour cells more efficiently than does calicheamicin-conjugated antibody. Labelling techniques leading to higher chemical yield and specific activities must be developed to increase (211)At-anti-CD33 therapeutic effects.

Lesion dose in differentiated thyroid carcinoma metastases after rhTSH or thyroid hormone withdrawal: 124I PET/CT dosimetric comparisons.

PURPOSE: Renal radioiodine excretion is ~50% faster during euthyroidism versus hypothyroidism. We therefore sought to assess lesion dose/GBq of administered 131I activity (LDpA) in iodine-avid metastases (IAM) of differentiated thyroid carcinoma (DTC) in athyreotic patients after recombinant human thyroid-stimulating hormone (rhTSH) versus after thyroid hormone withdrawal (THW). METHODS: We retrospectively compared mean LDpA between groups of consecutive patients (N=63) receiving 124I positron emission tomography/computed tomography (124I PET/CT) aided by rhTSH (n=27) or THW (n=36); we prospectively compared LDpA after these stimulation methods within another individual. Data derived from serial PET scans and one CT scan performed 2-96 h post-124I ingestion. A mixed model analysis of covariance (ANCOVA) calculated the treatment groups' mean LDpAs adjusting for statistically significant baseline intergroup differences: non-IAM were more prevalent, median IAM count/patient lower in cervical lymph nodes and higher in distant sites, median stimulated thyroglobulin higher, mean cumulative radioiodine activity greater and prior diagnostic scintigraphy more frequent in the rhTSH patients. RESULTS: Mean LDpAs were: rhTSH group (n=71 IAM), 30.6 Gy/GBq; THW group (n=66 IAM), 51.8 Gy/GBq. The difference in group means (rhTSH less THW), -21.2 Gy/GBq, was statistically non-significant (p=0.1667). However, the 95% confidence interval of that difference (-51.4 to +9 Gy/GBq) suggested a trend favouring THW. The within-patient comparison found 2.9- to 10-fold higher LDpAs under THW. CONCLUSION: We found some suggestions, but no statistically significant evidence, that rhTSH administration results in a lower radiation dose to DTC metastases than does THW. A large, well-controlled, prospective within-patient study should resolve this issue.

Estimation of glomerular filtration rate in liver-transplanted children: comparison of simplified procedures using 51Cr-EDTA and endogenous markers with Sapirstein's method as a reference standard.

This study evaluated simple procedures for GFR determination in 48 liver-transplanted children. After injection of (51)Cr-EDTA, blood samples were obtained up to four h, and activity retention in the body was measured for 60 min with scintillation probes. As a reference, GFR was calculated according to Sapirstein. Simplified calculations were performed according to Brochner-Mortensen, Russel, Devaux and Oberhausen. Additionally, GFR was determined using plasma creatinine and cystatin C according to Schwartz and Filler, respectively. The reference revealed mildly reduced GFR (62 +/- 20 mL/min/1.73 m(2)). Russel's method provided the highest degree of correlation (r(2) = 0.95), the smallest bias in GFR determination (-2%), and only one false exclusion plus one false diagnosis of chronic kidney disease. Oberhausen's method with blood sampling at one h post-injection performed slightly worse (r(2) = 0.67, bias: 3%). All other methods resulted in significantly different GFR estimates compared to the reference. Nevertheless, notably, the second narrowest 95% limits of agreement (-31% to 45%) was observed using cystatin C. In conclusion, this data implies to prefer Russel's method as a simplified procedure, and if patients cannot be available long enough (four h) for measurements, Oberhausen's method instead. If radiotracer methods are not available at all or for screening GFR, cystatin C appears to be the procedure of choice.

The first scintigraphic detection of tumor necrosis factor-alpha in patients with complex regional pain syndrome type 1.

Tumor necrosis factor (TNF)-alpha has been identified as a pathogenic factor in many immunologically based diseases and complex regional pain syndrome (CRPS). In this case series, we used radiolabeled technetium anti-TNF-alpha antibody to scintigraphically image TNF-alpha in 3 patients with type 1 CRPS. The results show that TNF-alpha was localized only in affected hands of patients with early-stage CRPS. No uptake was seen in clinically unaffected hands and late-stage CRPS. Our findings support the growing evidence for neuroimmune disturbance in patients with CRPS and may have important further implications for specific anticytokine treatment in patients with CRPS.

Modified calcium accumulation after controlled cortical impact under cyclosporin A treatment: a 45Ca autoradiographic study.

OBJECTIVE: As a neuroprotective drug, cyclosporin A (CsA) has been subject of multiple experimental works in traumatic brain injury (TBI) research. It is well known that CsA inhibits calcium (Ca2+) induced mitochondrial permeability transition (mPT). The aim of this study was to investigate the influence of CsA on the alteration of Ca2+ homeostasis after experimental brain injury. METHODS: Sprague-Dawley male rats (n = 36) with a mean weight of 330 g (280-350 g) were general anesthetized with isofluran through gas mask. The anesthetized animals (n = 24) were subjected to a controlled cortical impact (CCI) over the left parietotemporal cortex using round-tip impounder with a 5 mm diameter at a velocity of approximately 3.7 m/s and a penetration depth of 2 mm. The sham group (n = 12) underwent anesthesia and craniotomy without CCI. In the CCI groups, CsA (n = 12) or vehicle (n = 12) was administered 15 minutes post-injury with a subsequent i.p. injection after 24 hours. Thirty-three hours after injury or sham craniotomy, 45calcium (45Ca) suspended in physiologic saline solution was injected in the left femoral vein. Five hours after isotope administration, animals were killed and the brain was quickly removed and placed in powdered dry ice. Coronal plane sections (20 microm thick) taken every 400 microm from the frontal cortex through the occipital cortex, were exposed to cyclotron films for 14 days at -18 degrees C. Relative optical density was utilized to provide a relative measure of 45Ca accumulation within seven different structures. RESULTS: The difference of 45Ca accumulation (measured by relative optical density) in the CsA group was greater by 30-70% in the following structures compared to vehicle treated traumatized animals: temporal cortex, CA1, anteromedial and posteromedial thalamus (p < 0.05). CONCLUSION: Post-traumatic 45Ca accumulation is modified under CsA. The crucial neuroprotective effect of CsA might be unrelated to a reduction of post-traumatic Ca2+ accumulation, especially with regard to the importance of Ca2+ as an intracellular messenger governing a large number of cellular functions.

Correlates of local cerebral blood flow (CBF) in normal pressure hydrocephalus patients before and after shunting--A retrospective analysis of [(15)O]H(2)O PET-CBF studies in 65 patients.

OBJECTIVES: Findings in local cerebral blood flow (rCBF) in Normal pressure hydrocephalus (NPH) have always been challenged by the variable and inconsistent relation to clinical symptoms before and after shunt treatment. [(15)O]H(2)O PET data from a consecutive cohort of 65 idiopathic NPH patients were retrospectively analyzed questioning whether the functional status before and after shunt treatment might correlate with local blood flow. PATIENTS AND METHODS: Using statistical parametric mapping (SPM99, Wellcome Department of Cognitive Neurology, London), the [(15)O]H(2)O uptake was correlated with the preoperative clinical scores, graded according to a modified Stein and Langfitt score. Furthermore, differences in the uptake in the pre-and post-shunt treatment study after seven to 10 days in patients with and without clinical improvement were studied. RESULTS: A higher clinical score significantly correlated with a reduced tracer uptake in mesial frontal (k=1,239 voxel, Z=4.41) and anterior temporal (k=469, Z=4.07) areas. In the mesial frontal areas, tracer uptake showed significant reciprocal changes in the clinically improved vs. the unimproved patients. CONCLUSION: Matched with the existing literature, the regional blood flow alterations are suggested relevant to the NPH syndrome and to post-treatment functional changes. The present rCBF findings warrant prospective studies on the accuracy of neuroimaging studies as they may provide a more specific insight into disease mechanisms.

Effective cancer therapy with the alpha-particle emitter [211At]astatine in a mouse model of genetically modified sodium/iodide symporter-expressing tumors.

PURPOSE: The sodium/iodide symporter (NIS) gene is currently explored in several trials to eradicate experimental cancer with radiodine ((131)I) by its beta-emission. We recently characterized NIS-specific cellular uptake of an alternative halide, radioastatine ((211)At), which emits high-energy alpha-particles. The aim of this study was to investigate in vivo effects of the high linear energy transfer (LET) emitter (211)At on tumor growth and outcome in nude mice. EXPERIMENTAL DESIGN: We administered radioastatide in a fractionated therapy scheme to NMRI nude mice harboring rapidly growing solid tumors established from a papillary thyroid carcinoma cell line genetically modified to express NIS (K1-NIS). Animals were observed over 1 year. Tumor growth, body weight, blood counts, survival, and side effects were measured compared with control groups without therapy and/or lack of NIS expression. RESULTS: Within 3 months, radioastatide caused complete primary tumor eradication in all cases of K1-NIS tumor-bearing nude mice (n = 25) with no tumor recurrence during 1 year follow-up. Survival rates of the K1-NIS/(211)At group were 96% after 6 months and 60% after 1 year, in contrast to those of control groups (maximum survival 40 days). CONCLUSION: Our study indicates that (211)At represents a promising substrate for NIS-mediated therapy of various cancers either with endogenous or gene transfer-mediated NIS expression.

Preparation and evaluation of 211At labelled antineoplastic antibodies.

PURPOSE: The objective of this study was to determine and verify the stability of 211At-labelled antibodies under physiological conditions and their specific cell-binding capacity for selected epitopes, in order to evaluate the potential of 211At for alpha-radioimmunotherapy. METHODS: 211At was produced at the department's cyclotron and was linked via the intermediate 3-211At-succinimidyl-benzoate (SAB) to the antineoplastic antibodies rituximab, gemtuzumab and gemtuzumab ozogamicin. The stability of the labelled antibodies was determined in serum for 21 h. Cell-binding experiments on HL-60 and CI-1 cells included kinetic, saturation and competitive binding studies. For comparison the binding to antigen-negative cells was determined. The binding specificity and affinity and the IC50-values were evaluated. RESULTS: A consistent yield of 30% and a specific activity of 3 MBq/nmol was obtained. The stability of 211At-antibodies in murine serum exceeded 85% at 37 degrees C. Cell-binding to antigen-positive cells was >25%, while binding to antigen-negative cells did not exceed the unspecific binding and was smaller than 1%. IC50 values ranged between 2 and 11 nmol/L. CONCLUSIONS: A routine preparation of 211At-labelled antibodies was established and the stability of the 211At-labelled antibodies under physiologic conditions was verified. Apparently, labelling of antibodies with 211At by the method described does not compromise the affinity and specificity to the respective epitopes.

Monitoring of bone marrow cell homing into the infarcted human myocardium.

BACKGROUND: Intracoronary transfer of autologous bone marrow cells (BMCs) promotes recovery of left ventricular systolic function in patients with acute myocardial infarction. Although the mechanisms of this effect remain to be established, homing of BMCs into the infarcted myocardium is probably a critical early event. METHODS AND RESULTS: We determined BMC biodistribution after therapeutic application in patients with a first ST-segment-elevation myocardial infarction who had undergone stenting of the infarct-related artery. Unselected BMCs were radiolabeled with 100 MBq 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) and infused into the infarct-related coronary artery (intracoronary; n=3 patients) or injected via an antecubital vein (intravenous; n=3 patients). In 3 additional patients, CD34-positive (CD34+) cells were immunomagnetically enriched from unselected BMCs, labeled with 18F-FDG, and infused intracoronarily. Cell transfer was performed 5 to 10 days after stenting. More than 99% of the infused total radioactivity was cell bound. Nucleated cell viability, comparable in all preparations, ranged from 92% to 96%. Fifty to 75 minutes after cell transfer, all patients underwent 3D PET imaging. After intracoronary transfer, 1.3% to 2.6% of 18F-FDG-labeled unselected BMCs were detected in the infarcted myocardium; the remaining activity was found primarily in liver and spleen. After intravenous transfer, only background activity was detected in the infarcted myocardium. After intracoronary transfer of 18F-FDG-labeled CD34-enriched cells, 14% to 39% of the total activity was detected in the infarcted myocardium. Unselected BMCs engrafted in the infarct center and border zone; homing of CD34-enriched cells was more pronounced in the border zone. CONCLUSIONS: 18F-FDG labeling and 3D PET imaging can be used to monitor myocardial homing and biodistribution of BMCs after therapeutic application in patients.

Feasibility of central cannabinoid CB1 receptor imaging with [124I]AM281 PET demonstrated in a schizophrenic patient.

We studied central cannabinoid CB1 receptors in a schizophrenic patient using the pyrazole derivative AM281 labelled with the positron-emitting nuclide iodine-124. A dynamic positron emission tomography (PET) acquisition with simultaneous blood sampling was performed up to 1.5 h post-injection. The classical Logan plot analysis was applied to generate a three-dimensional map of distribution volume (DV). The map was spatially normalised into the Montreal Neurological Institute stereotactic space. Using a volume of interest (VOI) template, mean values of DV were extracted from multiple grey matter regions and white matter (as a reference). As a measure of regional receptor availability, ratios of DV in grey matter to DV in white matter minus one (DVR-1) were calculated. The highest receptor binding was observed in the striatum and the pallidum (DVR-1: 0.35-0.37). Binding in basal ganglia regions was lower on the left than the right side. Moderately high binding was seen in the frontal cortex (0.22), the temporal cortex (0.18) and the cerebellum (0.15). In conclusion, 124I-AM281 PET can be used to reveal areas with prominent CB1 receptor binding. Nevertheless, limited image contrast and relatively high radiation exposure (physical half-life of 124I: 4 days) have to be taken into account. Asymmetric receptor binding may possibly reflect pathologic changes in schizophrenia.

Engineering of a vascularized scaffold for artificial tissue and organ generation.

Tissue engineering is an emerging field in regenerative medicine to overcome the problem of end-stage organ failure. However, complex tissues and organs need a vascular supply to guaranty graft survival and render bioartificial organ function. Here we developed methods to decellularize porcine small bowl segments and repopulate the remaining venous and arterial tubular structures within these matrices with allogeneic porcine endothelial progenitor cells. Cellular adherence and vitality was characterized by quantitative 2-[18F]-fluoro-2'-desoxy-glucose (FDG) positron emission tomography (PET) and subsequent immunohistological work up. The generated matrices showed insulin-dependent FDG uptake predominantly in the region of the former vascular structures. Stain for vitality and the specific endothelial markers CD31, VE-Cadherin and Flk-1 matched this functional finding. Providing evidence for vitality up to 3 weeks post reconstitution and typical endothelial differentiation, these results indicate that our generated matrix allows the generation of complex bioartificial tissues and organs for experimental and future clinical application.

Serotonin transporter binding in Tourette Syndrome.

Recent studies provided evidence for an involvement of the dopaminergic system in the pathophysiology of Tourette Syndrome (TS). However, little is known about possible impairment of other neurotransmitter systems. In obsessive-compulsive disorder (OCD), a common comorbidity in TS, it is suggested that the serotonergic system plays a major role in the pathogenesis. We, therefore, used [I-123]2[beta]-carbomethoxy-3[beta]-(4-iodophenyl)tropane ([123I]beta-CIT) and single photon emission computed tomography (SPECT) to investigate serotonin transporter (SERT) binding capacity in 12 patients with TS with various degrees of associated obsessive compulsive behaviour (OCB) and 16 age-matched healthy controls. Binding ratios in TS patients not receiving serotonin reuptake inhibitors (SSRI) (n=8) were significantly reduced compared to age-adjusted ratios from normal controls (2.8 versus 3.2, p=0.003). Treatment with SSRI resulted in a significant reduction of SERT availability. Performing linear regression analysis for this small group, SSRI-free patients indicated trends for a negative correlation between [123I]beta-CIT binding on SERT and OCB (r=-0.78, p=0.023) as well as complex motor tics (r=-0.68, p=0.064). In healthy controls, but not in the TS group, we found an age-related decline in SERT binding capacity (0.28% decrease per year, p=0.038). Our data are in agreement with previous results suggesting an impairment of the serotonergic system in TS. It can be speculated that the reduction in SERT binding capacity is associated with the degree of comorbid OCB.

Use of recovery coefficients as a test of system linearity of response in positron emission tomography (PET).

Quantitative determination of activity concentration has always been regarded as a goal of PET scanner design. Therefore, a linear response with respect to activity concentration is essential. To prove system linearity of response a test is proposed based on the determination of recovery coefficients (RC) for different object geometries. If all degrading effects, especially scatter and attenuation, are corrected to a sufficient degree of accuracy, the system behaves linearly resulting in a theoretical relationship between hot (HSRC) and cold spot recovery coefficients (CSRC). Therefore this relationship, applied to appropriate phantom data containing hot or cold spheres, combined with the constraints on asymptotic behaviour of RC can be used as a test of system linearity of response. After applying the system's standard corrections RC were determined using both 2D and 3D data acquisition modes. For both 2D and 3D data, HSRC directly measured showed an excellent agreement with the HSRC calculated from the CSRC. The analysis was extended to radionuclides of different positron ranges, to the effect of data smoothing, and to that of iterative reconstruction. The agreement between the RC determined under varying border conditions demonstrates the effectiveness of the corrections used in constituting system linearity. Therefore, the method proposed is used as a test of system linearity of response.