Purpose Preclinical, or asymptomatic, Alzheimer's disease (AD) refers to the presence of positive AD biomarkers in the absence of cognitive deficits. This research concept is being applied to define target populations for clinical drug development. In a prospective community-recruited cohort of cognitively intact older adults, we compared two amyloid imaging markers within subjects: F-18-flutemetamol and C-11-Pittsburgh compound B (PIB). Methods In 32 community-recruited cognitively intact older adults aged between 65 and 80 years, we determined the concordance between binary classification based on F-18-flutemetamol versus C-11-PIB according to semiquantitative assessment (standardized uptake value ratio in composite cortical volume, SUVRcomp) and, alternatively, according to visual reads. We also determined the correlation between F-18-flutemetamol and C-11-PIB SUVR and evaluated how this was affected by the reference region chosen (cerebellar grey matter versus pons) and the use of partial volume correction (PVC) in this population. Results Binary classification based on semiquantitative assessment was concordant between F-18-flutemetamol and C-11-PIB in 94 % of cases. Concordance of blinded binary visual reads between tracers was 84 %. The Spearman correlation between F-18-flutemetamol and C-11-PIB SUVRcomp with cerebellar grey matter as reference region was 0.84, with a slope of 0.98. Correlations in neocortical regions were significantly lower with the pons as reference region. PVC improved the correlation in striatum and medial temporal cortex. Conclusion For the definition of preclinical AD based on F-18-flutemetamol, concordance with C-11-PIB was highest using semiquantitative assessment with cerebellar grey matter as reference region.

Affibody molecules constitute a class of small (7 kDa) scaffold proteins that can be engineered to have excellent tumor targeting properties. High reabsorption in kidneys complicates development of affibody molecules for radionuclide therapy. In this study, we evaluated the influence of the composition of cysteine-containing C-terminal peptide-based chelators on the biodistribution and renal retention of 188Re-labeled anti-HER2 affibody molecules. Biodistribution of affibody molecules containing GGXC or GXGC peptide chelators (where X is G, S, E or K) was compared with biodistribution of a parental affibody molecule ZHER2:2395 having a KVDC peptide chelator. All constructs retained low picomolar affinity to HER2-expressing cells after labeling. The biodistribution of all 188Re-labeled affibody molecules was in general comparable, with the main observed difference found in the uptake and retention of radioactivity in excretory organs. The 188Re-ZHER2:V2 affibody molecule with a GGGC chelator provided the lowest uptake in all organs and tissues. The renal retention of 188Re-ZHER2:V2 (3.1±0.5 %ID/g at 4 h after injection) was 55-fold lower than retention of the parental 188Re-ZHER2:2395 (172±32 %ID/g). We show that engineering of cysteine-containing peptide-based chelators can be used for significant improvement of biodistribution of 188Re-labeled scaffold proteins, particularly reduction of their uptake in excretory organs.

Aim/Introduction: The urinary bladder wall is a radiosensitive organ that can receive a high absorbed dose from radiopharmaceuticals used even in diagnostic nuclear medicine. The commonly used method to calculate the absorbed dose to the urinary bladder wall is to apply absorbed fractions or S-values derived for a static volume of the content e.g. 200 mL for adult males. However, there are some dynamic models to estimate the photon and electron absorbed dose contributions to the inner surface or the mean absorbed dose to the bladder wall. These models have only been applied on adults and use descriptive biokinetic models for the transfer of radionuclides. The aim of this work is to estimate the absorbed dose, based on Monte Carlo-simulated dynamic urinary bladders and the ICRP compartmental biokinetic models of iodide and pertechnetate. The calculations include sex specific absorbeddose and estimations for preadults of 15- 10- 5- 1-year and newborn.

Materials and Methods: S-values were calculated for different volumes of the content with a fix mass of the wall. As an approximation a spherical shape was assumed. Calculations were based on anatomical and physiological data of the reference sets of values given in ICRP Publication 89. The reference values were given for both male and female subjects of six different ages: newborn, 1-, 5-, 10-, 15-years, and adult. The elemental compositions of the urinary bladder wall and content were taken from the ICRP Publication 110.

Results: For adult male assuming a urinary flow rate of 1600 ml/day, an initial urine volume of 100 ml, a voiding volume at 300 ml and a residual volume of 30 ml, the cumulated activity will for intravenously administered activity of Tc-99m pertechnetate be 30 % lower than assuming a 3.5 hour voiding interwall. The absorbed dose to the urinary bladder wall will be 64% lower also applying the dynamic S-values on the dynamic case. Using the same biological parameters for intravenous intake of I-131 iodide, the cumulated activity will be 60 % higher for the dynamic case and the mean absorbed dose to the urinary bladder wall 30 % lower.

Conclusion: This project aims to perform more realistic calculation of absorbed dose to the urinary bladder calculations. This is done by tracking the activity in the urinary content at each time on compartment models and applying the time dependent activity to urinary flow and Monte Carlo simulated S-values.

Purpose To assess correlations between the degree of dopaminergic depletion measured using single-photon emission computed tomography (SPECT) and different clinical parameters of disease progression in Parkinson's disease (PD). Methods This retrospective study included 970 consecutive patients undergoing I-123-ioflupane SPECT scans in our institution between 2003 and 2013, from which we selected a study population of 411 patients according to their clinical diagnosis: 301 patients with PD (69.4 +/- 11.0 years, of age, 163 men) and 110 patients with nondegenerative conditions included as controls (72.7 +/- 8.0 years of age, 55 men). Comprehensive and operator-independent data analysis included spatial normalization into standard space, estimation of the mean uptake values in the striatum (caudate nucleus + putamen) and voxel-wise correlation between SPECT signal intensity and disease stage as well as disease duration in order to investigate the spatiotemporal pattern of the dopaminergic nigrostriatal degeneration. To compensate for potential interactions between disease stage and disease duration, one parameter was used as nonexplanatory coregressor for the other. Results Increasing disease stage was associated with an exponential decrease in I-123-ioflupane uptake (R (2) = 0.1501) particularly in the head of the ipsilateral caudate nucleus (p < 0.0001), whereas increasing disease duration was associated with a linear decrease in I-123-ioflupane uptake (p < 0.0001; R (2) = 0.1532) particularly in the contralateral anterior putamen (p < 0.0001). Conclusion We observed two distinct spatiotemporal patterns of posterior to anterior dopaminergic depletion associated with disease stage and disease duration in patients with PD. The developed operator-independent reference database of 411 I-123-ioflupane SPECT scans can be used for clinical and research applications.

Nuclear medicine has a central role in the diagnosis, staging, response assessment and long-term follow-up of neuroblastoma, the most common solid extracranial tumour in children. These EANM guidelines include updated information on I-123-mIBG, the most common study in nuclear medicine for the evaluation of neuroblastoma, and on PET/CT imaging with F-18-FDG, F-18-DOPA and Ga-68-DOTA peptides. These PET/CT studies are increasingly employed in clinical practice. Indications, advantages and limitations are presented along with recommendations on study protocols, interpretation of findings and reporting results.

Purpose

Molecular radiotherapy is a treatment modality that is highly suitable for targeting micrometastases and [¹⁷⁷Lu]Lu-DOTATATE is currently being explored as a potential novel treatment option for high-risk neuroblastoma. p53 is a key player in the proapoptotic signalling in response to radiation-induced DNA damage and is therefore a potential target for radiosensitisation.

Methods

This study investigated the use of the p53 stabilising peptide VIP116 and [¹⁷⁷Lu]Lu-DOTATATE, either alone or in combination, for treatment of neuroblastoma tumour xenografts in mice. Initially, the uptake of [¹⁷⁷Lu]Lu-DOTATATE in the tumours was confirmed, and the efficacy of VIP116 as a monotherapy was evaluated. Subsequently, mice with neuroblastoma tumour xenografts were treated with placebo, VIP116, [¹⁷⁷Lu]Lu-DOTATATE or a combination of both agents.

Results

The results demonstrated that monotherapy with either VIP116 or [¹⁷⁷Lu]Lu-DOTATATE significantly prolonged median survival compared to the placebo group (90 and 96.5 days vs. 50.5 days, respectively). Notably, the combination treatment further improved median survival to over 120 days. Furthermore, the combination group exhibited the highest percentage of complete remission, corresponding to a twofold increase compared to the placebo group. Importantly, none of the treatments induced significant nephrotoxicity. Additionally, the therapies affected various molecular targets involved in critical processes such as apoptosis, hypoxia and angiogenesis.

Conclusion

In conclusion, the combination of VIP116 and [¹⁷⁷Lu]Lu-DOTATATE presents a promising novel treatment approach for neuroblastoma. These findings hold potential to advance research efforts towards a potential cure for this vulnerable patient population.

OBJECTIVES: This study aimed to evaluate the level of evidence of expert recommendations and guidelines for clinical indications and procedurals in hybrid nuclear cardiovascular imaging.

METHODS: From inception to August 2023, a PubMed literature analysis of the latest version of guidelines for clinical hybrid cardiovascular imaging techniques including SPECT(/CT), PET(/CT), and PET(/MRI) was performed in two categories: (1) for clinical indications for all-in primary diagnosis; subgroup in prognosis and therapy evaluation; and for (2) imaging procedurals. We surveyed to what degree these followed a standard methodology to collect the data and provide levels of evidence, and for which topic systematic review evidence was executed.

RESULTS: A total of 76 guidelines, published between 2013 and 2023, were included. The evidence of guidelines was based on systematic reviews in 7.9% of cases, non-systematic reviews in 47.4% of cases, a mix of systematic and non-systematic reviews in 19.7%, and 25% of guidelines did not report any evidence. Search strategy was reported in 36.8% of cases. Strengths of recommendation were clearly reported in 25% of guidelines. The notion of external review was explicitly reported in 23.7% of cases. Finally, the support of a methodologist was reported in 11.8% of the included guidelines.

CONCLUSION: The use of evidence procedures for developing for evidence-based cardiovascular hybrid imaging recommendations and guidelines is currently suboptimal, highlighting the need for more standardized methodological procedures.

Purpose & Methods Neuroendocrine neoplasms are a heterogenous group of tumours, for which nuclear medicine plays an important role in the diagnostic work-up as well as in the targeted therapeutic options. This guideline is aimed to assist nuclear medicine physicians in recommending, performing, reporting and interpreting the results of somatostatin receptor (SSTR) PET/CT imaging using Ga-68-DOTA-conjugated peptides, as well as F-18-DOPA imaging for various neuroendocrine neoplasms. Results & Conclusion The previous procedural guideline by EANM regarding the use PET/CT tumour imaging with Ga-68-conjugated peptides has been revised and updated with the relevant and recent literature in the field with contribution of distinguished experts.

Aim: The F+10 method in supine position, which has been implemented at our Nuclear Medicine department since 2015, involves a 30- minute long dynamic acquisition. The diuretic is only administered when necessary and decision is taken by the radiographers in a semi-automated fashion without consulting a physician, by calculating the remaining activity in the kidneys seven minutes post 99mTc-MAG3 injection and comparing the value with an arbitrary threshold of 75 %. If needed, the diuretic is injected three minutes later. The aim of this study was to correlate our method with the established previously used F+20 protocol in adults. Is the currently used threshold of 75% of activity left in any kidney at seven minutes the optimal cut-off value for diuretic administration?

Material and Methods: This is an ongoing retrospective study which include 320 F+20 examinations of adult patients performed during 2013-2015. They were all re-evaluated according to the currently used F+10 method, categorized as requiring diuretic or not and correlated to the original F+20 examination. A ROC-curve was drawn to delineate the best cut-off value for remaining renal activity. Sensitivity, specificity and accuracy were calculated.

Results: Preliminary results indicate that the F+10 re-evaluations with the currently used cut-off value of 75% did not correlate with the original F+20 examinations. In 80% (255 examinations) of the F+10 re-evaluations diuretic would have been considered necessary while only 52% (167 examinations) received diuretics in the original F+20 renographies (sensitivity 1.0, specificity 0.42). However, all the patients who required furosemide in the original F+20 renographies would have received diuretic if they had been imaged with the F+10 protocol. Furthermore, examination time is considerably reduced. After an evaluation of the ROC-curve the optimal cut-off value was 94% (sensitivity 0.92, specificity 0.84, accuracy 0.88). However, by implementing this value, 13 patients (4%) would have been falsely categorized as not requiring diuretic.

Conclusions: The 99mTc-MAG3 renography with the F+10 protocol in supine position is a feasible and acceptable method in clinical practice.

Hybrid imaging consists of a combination of two or more imaging modalities, which equally contribute to image information. To date, hybrid cardiovascular imaging can be performed by either merging images acquired on different scanners, or with truly hybrid PET/CT and PET/MR scanners. The European Association of Nuclear Medicine (EANM), and the European Association of Cardiovascular Imaging (EACVI) of the European Society of Cardiology (ESC) aim to review clinical situations that may benefit from the use of hybrid cardiac imaging and provide advice on acquisition protocols providing the most relevant information to reach diagnosis in various clinical situations.

Purpose: The purpose of this study was to identify combinations of dose rate and exposure time that have the potential to provide curative treatment with targeted radionuclide therapy applying low dose rate beta irradiation.

Methods: Five tumour cell lines, U-373MG and U-118MG gliomas, HT-29 colon carcinoma, A-431 cervical squamous carcinoma and SKBR-3 breast cancer, were used. An experimental model with 10(5) tumour cells in each sample was irradiated with low dose rate beta particles. The criterion for successful treatment was absence of recovery of cells during a follow-up period of 3 months. The initial dose rates were in the range 0.1-0.8 Gy/h, and the cells were continuously exposed for 1, 3 or 7 days. These combinations covered dose rates and doses achievable in targeted radionuclide therapy.

Results: Continuous irradiation with dose rates of 0.2-0.3 and 0.4-0.6 Gy/h for 7 and 3 days, respectively, could kill all cells in each tumour cell sample. These treatments gave total radiation doses of 30-40 Gy. However, when exposed for just 24 h with about 0.8 Gy/h, only the SKBR-3 cells were successfully treated; all the other cell types recovered. There were large cell type-dependent variations in the growth delay patterns for the cultures that recovered. The U-118MG cells were most resistant and the U-373MG and SKBR-3 cells most sensitive to the treatments. The HT-29 and A-431 cells were intermediate.

Conclusion: The results serve as a guideline for the combinations of dose rate and exposure time necessary to kill tumour cells when applying low dose rate beta irradiation. The shift from recovery to "cure" fell within a narrow range of dose rate and exposure time combinations.

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

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

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

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

Purpose The aim of this study was to explore the cerebral distribution of the tau-specific PET tracer [F-18]THK5317 (also known as (S)-[F-18]THK5117) retention in different stages of Alzheimer's disease; and study any associations with markers of hypometabolism and amyloid-beta deposition. Methods Thirty-three individuals were enrolled, including nine patients with Alzheimer's disease dementia, thirteen with mild cognitive impairment (MCI), two with non-Alzheimer's disease dementia, and nine healthy controls (five young and four elderly). In a multi-tracer PET design [F-18]THK5317, [C-11] Pittsburgh compound B ([C-11]PIB), and [F-18]FDG were used to assess tau pathology, amyloid-beta deposition and cerebral glucose metabolism, respectively. The MCI patients were further divided into MCI [C-11]PIB-positive (n=11) and MCI [C-11]PIB-negative (n=2) groups. Results Test-retest variability for [F-18]THK5317-PET was very low (1.17-3.81 %), as shown by retesting five patients. The patients with prodromal (MCI [C-11]PIB-positive) and dementia-stage Alzheimer's disease had significantly higher [F-18]THK5317 retention than healthy controls (p=0.002 and p=0.001, respectively) in areas exceeding limbic regions, and their discrimination from this control group (using the area under the curve) was >98 %. Focal negative correlations between [F-18]THK5317 retention and [F-18]FDG uptake were observed mainly in the frontal cortex, and focal positive correlations were found between [F-18]THK5317 and [C-11] PIB retentions isocortically. One patient with corticobasal degeneration syndrome and one with progressive supranuclear palsy showed no [C-11]PIB but high [F-18]THK5317 retentions with a different regional distribution from that in Alzheimer's disease patients. Conclusions The tau-specific PET tracer [F-18]THK5317 images in vivo the expected regional distribution of tau pathology. This distribution contrasts with the different patterns of hypometabolism and amyloid-beta deposition.

Several tau PET tracers have been developed, but it remains unclear whether they bind to the same molecular target on the heterogeneous tau pathology. In this study we evaluated the binding of two chemically different tau-specific PET tracers (C-11-THK5351 and C-11-PBB3) in a head-to-head, in vivo, multimodal design. Nine patients with a diagnosis of mild cognitive impairment or probable Alzheimer's disease and cerebrospinal fluid biomarker evidence supportive of the presence of Alzheimer's disease brain pathology were recruited after thorough clinical assessment. All patients underwent imaging with the tau-specific PET tracers C-11-THK5351 and C-11-PBB3 on the same day, as well as imaging with the amyloid-beta-specific tracer C-11-AZD2184, a T1-MRI sequence, and neuropsychological assessment. The load and regional distribution of binding differed between C-11-THK5351 and C-11-PBB3 with no statistically significant regional correlations observed between the tracers. The binding pattern of C-11-PBB3, but not that of C-11-THK5351, in the temporal lobe resembled that of C-11-AZD2184, with strong correlations detected between C-11-PBB3 and C-11-AZD2184 in the temporal and occipital lobes. Global cognition correlated more closely with C-11-THK5351 than with C-11-PBB3 binding. Similarly, cerebrospinal fluid tau measures and entorhinal cortex thickness were more closely correlated with C-11-THK5351 than with C-11-PBB3 binding. This research suggests different molecular targets for these tracers; while C-11-PBB3 appeared to preferentially bind to tau deposits with a close spatial relationship to amyloid-beta, the binding pattern of C-11-THK5351 fitted the expected distribution of tau pathology in Alzheimer's disease better and was more closely related to downstream disease markers.

Purpose The PET radioligand [C-11]PBR28 binds to the translocator protein (TSPO), a marker of brain immune activation. We examined the reproducibility of [C-11]PBR28 binding in healthy subjects with quantification on a regional and voxel-by-voxel basis. In addition, we performed a preliminary analysis of diurnal changes in TSPO availability. Methods Twelve subjects were examined using a high-resolution research tomograph and [C-11]PBR28, six in the morning and afternoon of the same day, and six in the morning on two separate days. Regional volumes of distribution (V-T) were derived using a region-of-interest based two-tissue compartmental analysis (2TCM), as well as a parametric approach. Metabolite-corrected arterial plasma was used as input function. Results For the whole sample, the mean absolute variability in V (T) in the grey matter (GM) was 18.3 +/- 12.7 %. Intraclass correlation coefficients in GM regions ranged from 0.90 to 0.94. Reducing the time of analysis from 91 to 63 min yielded a variability of 16.9 +/- 14.9 %. There was a strong correlation between the parametric and 2TCM-derived GM values (r=0.99). A significant increase in GM V-T was observed between the morning and afternoon examinations when using secondary methods of quantification (p=0.028). In the subjects examined at the same time of the day, the absolute variability was 15.9 +/- 12.2 % for the 91-min 2TCM data. Conclusion V-T of [C-11]PBR28 binding showed medium reproducibility and high reliability in GM regions. Our findings support the use of parametric approaches for determining [C-11]PBR28 V-T values, and indicate that the acquisition time could be shortened. Diurnal changes in TSPO binding in the brain may be a potential confounder in clinical studies and should be investigated further.