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Purpose: Expression of the translocator protein (TSPO) is upregulated in activated macrophages/microglia and is considered to be a marker of neuroinflammation. We investigated the novel TSPO ligand [18F]GE-180 in patients with relapsing-remitting multiple sclerosis (RRMS) to determine the feasibility of [18F]GE-180 PET imaging in RRMS patients and to assess its ability to detect active inflammatory lesions in comparison with the current gold standard, contrast-enhanced magnetic resonance imaging (MRI).Methods: Nineteen RRMS patients were prospectively included in this study. All patients underwent TSPO genotyping and were classified as high-affinity, medium-affinity or low-affinity binders (HAB/MAB/LAB). PET scans were performed after administration of 189 ± 12 MBq [18F]GE-180, and 60-90 min summation images were used for visual analysis and assessment of standardized uptake values (SUV). The frontal nonaffected cortex served as a pseudoreference region (PRR) for evaluation of SUV ratios (SUVR). PET data were correlated with MRI signal abnormalities, i.e. T2 hyperintensity or contrast enhancement (CE). When available, previous MRI data were used to follow the temporal evolution of individual lesions.Results: Focal lesions were identified as hot spots by visual inspection. Such lesions were detected in 17 of the 19 patients and overall 89 [18F]GE-180-positive lesions were found. TSPO genotyping revealed 11 patients with HAB status, 5 with MAB status and 3 with LAB status. There were no associations between underlying binding status (HAB, MAB and LAB) and the signal intensity in either lesions (SUVR 1.87 ± 0.43, 1.95 ± 0.48 and 1.86 ± 0.80, respectively; p = 0.280) or the PRR (SUV 0.36 ± 0.03, 0.40 ± 0.06 and 0.37 ± 0.03, respectively; p = 0.990). Of the 89 [18F]GE-180-positive lesions, 70 showed CE on MRI, while the remainder presented as T2 lesions without CE. SUVR were significantly higher in lesions with CE than in those without (2.00 ± 0.53 vs. 1.60 ± 0.15; p = 0.001). Notably, of 19 [18F]GE-180-positive lesions without CE, 8 previously showed CE, indicating that [18F]GE-180 imaging may be able to detect lesional activity that is sustained beyond the blood-brain barrier breakdown.Conclusion: [18F]GE-180 PET can detect areas of focal macrophage/microglia activation in patients with RRMS in lesions with and without CE on MRI. Therefore, [18F]GE-180 PET imaging is a sensitive and quantitative approach to the detection of active MS lesions. It may provide information beyond contrast-enhanced MRI and is readily applicable to all patients. [18F]GE-180 PET imaging is therefore a promising new tool for the assessment of focal inflammatory activity in MS. [ABSTRACT FROM AUTHOR]

Background Frequent computed tomography (CT) follow-ups involve significant radiation related risks for patients with low-grade neuroendocrine tumors (NETs). Contrast agent (CA) application is essential for diagnostic evidence and has additional risks especially in patients with limited renal function. Purpose To investigate if a combination of dose and contrast agent (CA) reduction affects image quality and diagnostic evidence in neuroendocrine tumor (NET) patients. Material and Methods A total of 51 NET patients were enrolled in the study and 153 CT scans were analyzed. Patients underwent a baseline CT scan (A = 120 kVp, filtered back projection [FBP]) and two follow-up CTs (B = 120 kVp, adaptive statistical iterative reconstruction [ASIR] 40%; C1 = 100 kVp, ASIR 40%; C2 = 100 kVp, ASIR 60%; the latter two protocols were applied with a 30% reduction in CA volume). We evaluated image quality and applied dose. Results In C1/2, the combination of low kV (100 kVp) with ASIR 40%/60% reduced the mean applied dose significantly by 28% compared to B and by 57% compared to A. Signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) of tumor to liver/muscle were significantly increased by using C1/2 compared to B and A. With respect to subjective image quality, a slight loss of diagnostic confidence in C1 could be counterbalanced by the higher ASIR blending in C2. Conclusion Combined dose reduction techniques can be used to reduce radiation dose and CA volume without sacrificing image quality and diagnostic confidence in staging CT of NET patients. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) shows reduced binding of the dopamine D(2/3) antagonist [(11) C]raclopride in striatum of withdrawn psychostimulant abusers, but not consistently in patients with alcohol dependence (AD). We make first use of the high affinity ligand [(18) F]fallypride to obtain serial measures of D(2/3) receptor availability in striatal and extrastriatal regions of AD patients undergoing detoxification. Seventeen patients (mean age 44 ± 5y) with AD and 14 age-matched healthy volunteers participated. Each patient underwent [(18) F]fallypride PET upon hospital admission, and again 1-2 weeks later; two patients achieving abstinence, and two with substantial harm reduction had additional PET follow-up at 1 year. Dynamic 180-minute PET recordings were used for volume of interest (VOI)-based and voxel-wise analysis of [(18) F]fallypride binding potential (BP(ND) ). Mean baseline BP(ND) in striatum of the AD patients (15.7 ± 3.6) was unaltered during short-term follow-up, and did not differ from that in healthy controls (16.8 ± 3.0); however, BP(ND) was 10-20% lower in thalamus, hippocampus, and insular and temporal cortex of the AD patients (P < 0.05). Age-dependent declines in BP(ND) were very small in controls, but more pronounced and widespread in the AD group. Striatal and thalamic BP(ND) increased by 30% in four patients with long-term abstinence or reduced alcohol consumption. VOI-based [(18) F]fallypride PET analyses revealed group differences in D(2/3) receptor availability primarily in extra-striatal regions. Age-related loss of dopamine D(2/3) receptors was more pronounced in AD patients. Receptor availability was unaltered by acute withdrawal, but increased in the subgroup of patients with long-term follow-up, suggesting reversibility of receptor changes. [ABSTRACT FROM AUTHOR]

Background: Rest thallium-201/stress technetium 99m sestamibi protocol is widely used in the clinical setting. Although attenuation correction (AC) represents an important recent development in cardiac single photon emission computed tomography (SPECT) imaging, adjacent extracardiac activity can affect the myocardial count density distribution on AC images, particularly with 201Tl. The aims of this study were to compare normal distribution between AC rest 201Tl and stress 99mTc-sestamibi SPECT images as well as to evaluate the effect of extracardiac activity on AC SPECT images with 99mTc and 201Tl.Methods and Results: A phantom measurement and a study of 21 patients with low likelihood of coronary artery disease were performed with a triple-head SPECT system equipped with a americium 241 line source. In the phantom study, the presence of extracardiac activity increased the inferior-to-anterior ratios, particularly with 201Tl (1.01 to 1.32). In the clinical data, reduced count density with 201Tl compared to 99mTc-sestamibi was observed in most of the noninferior segments. On an individual segment basis, 37 (20%) of 189 segments from 11 (52%) of 21 subjects showed reduced count density on the 201Tl image compared to 99mTc-sestamibi by >10% of peak activity.Conclusions: There is a significant difference in myocardial count density distribution between 99mTc-sestamibi and 201Tl on AC SPECT images, indicating that a careful image interpretation that considers the different normal count density distribution between the tracers and/or a tracer specific normal database is necessary, especially when defect reversibility is of concern. Further work should aim for the incorporation of scatter correction combined with attenuation correction. [ABSTRACT FROM AUTHOR]

Background: NETTER-1 trial demonstrated high efficacy and low toxicity of four cycles of Peptide Receptor Radionuclide Therapy (PRRT) in patients with metastasized NET. The present study evaluates the outcome of further PRRT cycles in the so called salvage setting in patients after initial response to four therapy cycles and later progression.Methods: Thirty five patients (pat.) (25 male, 10 female, 63 ± 9 years) with progressive, metastasized NET (23 small intestinal, 5 lung, 4 CUP, 1 rectal, 1 gastric and 1 paraganglioma) were included. All patients previously received 4 PRRT cycles with 177Lu-DOTATATE and showed initial response. SPECT based dosimetry was applied to determine kidney and tumor doses. Therapy response was evaluated using 68Ga-DOTATATE PET/CT (with high dose CT), CT alone or MRI (RECIST 1.1), toxicity was defined using CTCAE 5.0 criteria. 99mTc99-MAG3 scintigraphy was used to assess potential renal tubular damage. Progression free survival (PFS) and Overall survival (OS) analysis was performed with the Kaplan-Meier-method.Results: The median PFS after initial PRRT was 33 months (95% CI: 30-36). The mean cumulative dose for including salvage PRRT was 44 GBq (range 33.5-47). One pat. (2.9%) showed grade 3 hematotoxicity. Kidney dosimetry revealed a mean cumulative kidney dose after a median of 6 PRRT cycles of 23.8 Gy. No grade 3 / 4 nephrotoxicity or relevant decrease in renal function was observed. Follow-up imaging was available in 32 patients after salvage therapy. Best response according to RECIST 1.1. was PR in one patient (3.1%), SD in 26 patients (81.3%) and PD in 5 patients (15.6%). PFS after salvage therapy was 6 months (95% CI: 0-16; 8 patients censored). Mean OS after initial PRRT was 105 months (95% CI: 92-119) and 51 months (95% CI: 41-61) after start of salvage therapy. Median OS was not reached within a follow-up of 71 months after initial PRRT and 25 months after start of salvage PRRT, respectively.Conclusions: Salvage therapy with 177Lu-DOTATATE is safe and effective even in patients with extensive previous multimodal therapies during disease progression and represents a feasible and valuable therapy option for progressive NET. [ABSTRACT FROM AUTHOR]

Background: The heart-to-mediastinum ratio (H/M-Ratio) of 123 iodo-metaiodobenzylguanidine ( 123 I-MIBG) represents state-of-the-art assessment for sympathetic dysfunction in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). This study aims to evaluate quantitative reconstruction of 123 I-MIBG uptake and to demonstrate its correlation with echocardiographic parameters., Methods: Cardiac innervation was assessed in 23 patients diagnosed with definite ARVC or borderline ARVC and 12 patients with other cardiac disease presenting arrhythmia, using quantitative 123 I-MIBG Single Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) imaging. Tracer uptake was evaluated in the left (LV) and right ventricle (RV) based on a CT scan after quantitative image reconstruction. The relationship between tracer uptake and echocardiographic parameter data was examined., Results: Absolute quantification of 123 I-MIBG uptake in the LV and RV is feasible and correlates accurately with the gold standard H/M Ratio. When comparing sensitivity and specificity, the area under the curve (AUC) favors standardized uptake value (SUV) of the RV over the right-ventricle-to-mediastinum-ratio (RV/M-Ratio) for diagnosing ARVC. A reduced RV-SUV in patients with definite ARVC is associated with reduced RV function. RV polar maps revealed globally reduced 123 I-MIBG uptake without segment-specific reduction in the RV., Conclusions: Quantitative 123 I-MIBG SPECT in ARCV patients offers robust potential for clinical reporting and demonstrates a significant correlation with RV function. Segmental RV analysis needs to be evaluated in larger samples. In summary, cardiac 123 I-MIBG imaging using SUV could facilitate image-guided therapy in patients diagnosed with ARVC., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: Transjugular intrahepatic portosystemic shunt (TIPS) is a catheter-based, minimally invasive procedure to reduce portal hypertension. The aim of the study was to investigate dysfunction and mortality after TIPS and to identify factors associated with these events., Methods: A retrospective analysis of 834 patients undergoing TIPS implantation in a single center from 1993-2018 was performed. Cumulative incidence curves were estimated, and frailty models were used to assess associations between potentially influential variables and time to dysfunction or death., Results: 1-, 2-, and 5-year mortality rates were 20.9% (confidence interval (CI) 17.7-24.1), 22.5% (CI 19.1-25.8), and 25.0% (CI: 21.1-28.8), 1-year, 2-year, and 5-year dysfunction rates were 28.4% (CI 24.6-32.3), 38.9% (CI 34.5-43.3), and 52.4% (CI 47.2-57.6). The use of covered stents is a protective factor regarding TIPS dysfunction (hazard ratio (HR) 0.47, CI 0.33-0.68) but does not play a major role in survival (HR 0.95, CI 0.58-1.56). Risk factors for mortality are rather TIPS in an emergency setting (HR 2.78, CI 1.19-6.50), a previous TIPS dysfunction (HR 2.43, CI 1.28-4.62), and an increased Freiburg score (HR 1.45, CI 0.93-2.28)., Conclusion: The use of covered stents is an important protective factor regarding TIPS dysfunction. Whereas previous TIPS dysfunction, emergency TIPS implantation, and an elevated Freiburg score are associated with increased mortality. Awareness of risk factors could contribute to a better selection of patients who may benefit from a TIPS procedure and improve clinical follow-up with regard to early detection of thrombosis/stenosis., Critical Relevance Statement: The use of covered stents reduces the risk of dysfunction after transjugular intrahepatic portosystemic shunt (TIPS). TIPS dysfunction, emergency TIPS placement, and a high Freiburg score are linked to higher mortality rates in TIPS patients., Key Points: The risk of dysfunction is higher for uncovered stents compared to covered stents. Transjugular intrahepatic portosystemic shunt dysfunction increases the risk of instantaneous death after the intervention. A higher Freiburg score increases the rate of death after the intervention. Transjugular intrahepatic portosystemic shunt implantations in emergency settings reduce survival rates., (© 2024. The Author(s).)

Internal dosimetry supports safe and effective patient management during radionuclide therapy. Yet, it is associated with high clinical workload, costs, and patient burden, as patient scans at multiple time points (MTPs) must be acquired. Dosimetry based on imaging at a single time point (STP) has continuously gained popularity. However, MTP protocols, used as a reference to judge the validity of STP dosimetry, differ depending on local requirements and deviate from the unknown patient-specific ground truth pharmacokinetics. The aim of this study was to compare the error and optimum time point for different STP approaches using different reference MTP protocols. Methods: Whole-body SPECT/CT scans of 7 patients (7.4-8.9 GBq of [ 177 Lu]Lu-PSMA-I&T) were scheduled at 24, 48, 72, and 168 h after injection. Sixty lesions, 14 kidneys, and 10 submandibular glands were delineated in the SPECT/CT data. Two curve models, that is, a mono- and a biexponential model, were fitted to the MTP data, in accordance with goodness-of-fit analysis (coefficients of variation, sum of squared errors). Three population-based STP approaches were compared: one method published by Hänscheid et al., one by Jackson et al., and one using population-based effective half-lives in the mono- or biexponential curve models. Percentage differences between STP and MTP dosimetry were evaluated. Results: Goodness-of-fit parameters show that a monoexponential function and a biexponential function with shared population-based parameters and physical tail are reasonable reference models. When comparing both reference models, we observed maximum differences of -44%, -19%, and -28% in the estimated absorbed doses for lesions, kidneys, and salivary glands, respectively. STP dosimetry with an average deviation of less than 10% from MTP dosimetry may be feasible; however, this deviation and the optimum imaging time point showed a dependence on the chosen reference protocol. Conclusion: STP dosimetry for [ 177 Lu]Lu-PSMA therapy is promising to boost the integration of dosimetry into clinical routine. According to our patient cohort, 48 h after injection may be regarded as a compromise for STP dosimetry for lesions and at-risk organs. The results from this analysis show that a common gold standard for dosimetry is desirable to allow for reliable and comparable STP dosimetry., (© 2024 by the Society of Nuclear Medicine and Molecular Imaging.)

This CIRSE Standards of Practice document is aimed at interventional radiologists and provides best practices for performing liver regeneration therapies prior to major hepatectomies, including portal vein embolization, double vein embolization and liver venous deprivation. It has been developed by an expert writing group under the guidance of the CIRSE Standards of Practice Committee. It encompasses all clinical and technical details required to perform liver regeneration therapies, revising the indications, contra-indications, outcome measures assessed, technique and expected outcomes., (© 2024. The Author(s).)

Metal artifacts notoriously pose significant challenge in computed tomography (CT), leading to inaccuracies in image formation and interpretation. Artifact reduction tools have been designed to improve cone beam computed tomography (CBCT) image quality by reducing artifacts caused by certain high-density materials. Metal artifact reduction (MAR) tools are specific algorithms that are applied during image reconstruction to minimize or eliminate artifacts degrading CBCT images. The purpose of the study is to evaluate the effect of a MAR algorithm on image quality in CBCT performed for evaluating patients before transarterial radioembolization (TARE). We retrospectively included 40 consecutive patients (aged 65 ± 13 years; 23 males) who underwent 45 CBCT examinations (Allura FD 20, XperCT Roll protocol, Philips Healthcare, Best, The Netherlands) in the setting of evaluation for TARE between January 2017 and December 2018. Artifacts caused by coils, catheters, and surgical clips were scored subjectively by four readers on a 5-point scale (1 = artifacts affecting diagnostic information to 5 = no artifacts) using a side-by-side display of uncorrected and MAR-corrected images. In addition, readers scored tumor visibility and vessel discrimination. MAR-corrected images were assigned higher scores, indicating better image quality. The differences between the measurements with and without MAR were most impressive for coils with a mean improvement of 1.6 points (95%CI [1.5 1.8]) on the 5-point likert scale, followed by catheters 1.4 points (95%CI [1.3 1.5]) and clips 0.7 points (95%CI [0.3 1.1]). Improvements for other artifact sources were consistent but relatively small (below 0.25 points on average). Interrater agreement was good to perfect (Kendall's W coefficient = 0.68-0.95) and was higher for MAR-corrected images, indicating that MAR improves diagnostic accuracy. A metal artifact reduction algorithm can improve diagnostic and interventional accuracy of cone beam CT in patients undergoing radioembolization by reducing artifacts caused by diagnostic catheters and coils, lowering interference of metal artifacts with adjacent major structures, and improving tumor visibility., (© 2024. The Author(s).)

Purpose: To assess the efficacy and safety of computed tomography (CT)-guided high-dose-rate HDR) brachytherapy in treating recurrent hepatocellular carcinoma (HCC) not amenable to repeated resection or radiofrequency ablation., Materials and Methods: From January 2010 to January 2022, 38 patients (mean age, 70.1 years; SD ± 9.0 years) with 79 nodular and four diffuse intrahepatic HCC recurrences not amenable to repeated resection or radiofrequency ablation underwent CT-guided HDR brachytheapy in our department. Tumor response was evaluated by cross-sectional imaging 6 weeks after CT-guided HDR brachytherapy and every 3 months thereafter. Local tumor control (LTC), progression-free survival (PFS) and overall survival (OS) were assessed using Kaplan-Meier curves (KPCs). Severity of procedure-related complications (PRCs) was classified as recommended by the Society of Interventional Radiology (SIR)., Results: Patients were available for MRI evaluation for a mean follow-up of 33.1 months (SD, ±21.6 mm, range 4-86 months; median 29 months). Patients had a mean of 2.3 (SD, ±1.4) intrahepatic tumors. Mean tumor diameter was 43.2 mm (SD, ±19.6 mm). 13 of 38 (34.2%) patients showed local tumor progression after CT-guided HDR brachytherapy. Mean LTC was 29.3 months (SD, ±22.1). Distant tumor progression was seen in 12 patients (31.6%). The mean PFS was 20.8 months (SD, ±22.1). Estimated 1-, 3-, and 5-year PFS rates were 65.1%, 35.1% and 22.5%, respectively. 13 patients died during the follow-up period. Mean OS was 35.4 months (SD, ±21.7). Estimated 1-, 3-, and 5-year OS rates were 91.5%, 77.4% and 58.0%, respectively. SIR grade 1 complications were recorded in 8.6% (5/38) and SIR grade 2 complications in 3.4% (2/58) of interventions., Conclusion: CT-guided HDR brachytherapy is a safe and efficient therapeutic option for managing large or critically located HCC recurrences in the remaining liver after prior hepatic resection., Competing Interests: Declaration of competing Interest None., (© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Purpose: Although 221 Fr and 213 Bi have sufficient gamma emission probabilities, quantitative SPECT after [ 225 Ac]Ac-PSMA-I&T therapy remains challenging due to low therapeutic activities. Furthermore, 221 Fr and 213 Bi may underlie a different pharmacokinetics due to alpha recoil. We conducted a quantitative SPECT study and a urine analysis to investigate the pharmacokinetics of 221 Fr and 213 Bi and the impact on image-based lesion and kidney dosimetry., Methods: Five patients (7.7 ± 0.2 MBq [ 225 Ac]Ac-PSMA-I&T) underwent an abdominal SPECT/CT (1 h) at 24 and 48 h (Siemens Symbia T2, high-energy collimator, 440 keV/218 keV (width 20%), 78 keV (width 50%)). Quantitative SPECT was reconstructed using MAP-EM with attenuation and transmission-dependent scatter corrections and resolution modelling. Time-activity curves for kidneys (CT-based) and lesions (80% isocontour 24 h) were fitted mono-exponentially. Urine samples collected along with each SPECT/CT were measured in a gamma counter until secular equilibrium was reached., Results: Mean kidney and lesion effective half-lives were as follows: 213 Bi, 27 ± 6/38 ± 10 h; 221 Fr, 24 ± 6/38 ± 11 h; 78 keV, 23 ± 7/39 ± 13 h. The 213 Bi-to- 221 Fr kidney SUV ratio increased by an average of 9% from 24 to 48 h. Urine analysis revealed an increasing 213 Bi-to- 225 Ac ratio (24 h, 0.98 ± 0.15; 48 h, 1.08 ± 0.09). Mean kidney and lesion absorbed doses were 0.17 ± 0.06 and 0.36 ± 0.1 Sv RBE = 5 /MBq using 221 Fr and 213 Bi SPECT images, compared to 0.16 ± 0.05/0.18 ± 0.06 and 0.36 ± 0.1/0.38 ± 0.1 Sv RBE = 5 /MBq considering either the 221 Fr or 213 Bi SPECT., Conclusion: SPECT/CT imaging and urine analysis showed minor differences of up to 10% in the daughter-specific pharmacokinetics. These variances had a minimal impact on the lesion and kidney dosimetry which remained within 8%., (© 2024. The Author(s).)