Safety and Efficacy of Para-Aminohippurate Coinfusion for Renal Protection During Peptide Receptor Radiotherapy in Patients with Neuroendocrine Tumors

Para-aminohippurate, also known as p-aminohippuric acid (PAH), is used clinically to measure effective renal plasma flow. Preclinically, it was shown to reduce 177Lu-DOTATOC uptake in the kidneys while improving bioavailability compared with amino acid (AA) coinfusion. We report the safety and efficacy of PAH coinfusion during peptide receptor radiotherapy in patients with neuroendocrine tumors. Methods: Twelve patients with metastatic or unresectable gastroenteropancreatic neuroendocrine tumors received 177Lu-DOTATOC in 33 treatment cycles. Either 8 g of PAH or a mixture of 25 g of arginine and 25 g of lysine were coinfused. Safety was assessed by monitoring laboratory data, including hematologic and renal data, as well as electrolytes obtained before and 24 h after treatment. For radiation dosimetry, whole-body scans were performed at 1, 24, and 48 h and a SPECT/CT scan was performed at 48 h, along with blood sampling at 5 min and 0.5, 2, 4, 24, and 48 h after administration. Absorbed dose estimations for the kidneys and bone marrow were performed according to the MIRD concept. Results: In 15 treatment cycles, PAH was coinfused. No changes in mean creatinine level, glomerular filtration rate, and serum electrolytes were observed before or 24 h after treatment when using PAH protection (P ≥ 0.20), whereas serum chloride and serum phosphate increased significantly under AA (both P < 0.01). Kidney-absorbed dose coefficients were 0.60 ± 0.14 Gy/GBq with PAH and 0.53 ± 0.16 Gy/GBq with AA. Based on extrapolated cumulative kidney-absorbed doses for 4 cycles, 1 patient with PAH protection and 1 patient with AA protection in our patient group would exceed the 23-Gy conservative threshold. The bone marrow-absorbed dose coefficient was 0.012 ± 0.004 Gy/GBq with PAH and 0.012 ± 0.003 Gy/GBq with AA. Conclusion: PAH is a promising alternative to AA for renal protection during peptide receptor radiotherapy. Further research is required to systematically investigate the safety profile and radiation dosimetry at varying PAH plasma concentrations.

Fibroblast Activation Protein α-Directed Imaging and Therapy of Solitary Fibrous Tumor

Fibroblast activation protein α (FAPα) is expressed at high levels in several types of tumors. Here, we report the expression pattern of FAPα in solitary fibrous tumor (SFT) and its potential use as a radiotheranostic target. Methods: We analyzed FAPα messenger RNA and protein expression in biopsy samples from SFT patients using immunohistochemistry and multiplexed immunofluorescence. Tracer uptake and detection efficacy were assessed in patients undergoing clinical 68Ga-FAPα inhibitor (FAPI)-46 PET,18F-FDG PET, and contrast-enhanced CT. 90Y-FAPI-46 radioligand therapy was offered to eligible patients with progressive SFT. Results: Among 813 patients and 126 tumor entities analyzed from the prospective observational MASTER program of the German Cancer Consortium, SFT (n = 34) had the highest median FAPα messenger RNA expression. Protein expression was confirmed in tumor biopsies from 29 of 38 SFT patients (76%) in an independent cohort. Most cases showed intermediate to high FAPα expression by immunohistochemistry (24/38 samples, 63%), which was located primarily on the tumor cell surface. Nineteen patients who underwent 68Ga-FAPI-46 PET imaging demonstrated significantly increased tumor uptake, with an SUVmax of 13.2 (interquartile range [IQR], 10.2), and an improved mean detection efficacy of 94.5% (SEM, 4.2%), as compared with 18F-FDG PET (SUVmax, 3.2 [IQR, 3.1]; detection efficacy, 77.3% [SEM, 5.5%]). Eleven patients received a total of 34 cycles (median, 3 cycles [IQR, 2 cycles]) of 90Y-FAPI-46 radioligand therapy, which resulted in disease control in 9 patients (82%). Median progression-free survival was 227 d (IQR, 220 d). Conclusion: FAPα is highly expressed by SFT and may serve as a target for imaging and therapy. Further studies are warranted to define the role of FAPα-directed theranostics in the care of SFT patients.

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

Radioguidance that makes use of β-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 β-emitters for surgical radioguidance. In this position paper, the EANM identifies the possibilities and challenges that relate to the successful implementation of β-emitters in surgical guidance, covering aspects related to instrumentation, radiation protection, and modes of implementation.

Biodistribution and radiation dosimetry of 124I-mIBG in adult patients with neural crest tumours and extrapolation to paediatric models

AIM

Positron emission tomography (PET) using 124I-mIBG has been established for imaging and pretherapeutic dosimetry. Here, we report the first systematic analysis of the biodistribution and radiation dosimetry of 124I-mIBG in patients with neural crest tumours and project the results to paediatric patient models.

METHODS

Adult patients with neural crest tumours who underwent sequential 124I-mIBG PET were included in this retrospective single-center analysis. PET data were acquired 4, 24, 48, and/or 120 h after administration of a mean of 43 MBq 124I-mIBG. Whole-body counting and blood sampling were performed at 2, 4, 24, 48 and 120 h after administration. Absorbed organ dose and effective dose coefficients were estimated in OLINDA/EXM 2.2 according to the MIRD formalism. Extrapolation to paediatric models was performed based on mass-fraction scaling of the organ-specific residence times. Biodistribution data for adults were also projected to 123I-mIBG and 131I-mIBG.

RESULTS

Twenty-one patients (11 females, 10 males) were evaluated. For adults, the organs exposed to the highest dose per unit administered activity were urinary bladder (1.54 ± 0.40 mGy/MBq), salivary glands (0.77 ± 0.28 mGy/MBq) and liver (0.65 ± 0.22 mGy/MBq). Mean effective dose coefficient for adults was 0.25 ± 0.04 mSv/MBq (male: 0.24 ± 0.03 mSv/MBq, female: 0.26 ± 0.06 mSv/MBq), and increased gradually to 0.29, 0.44, 0.69, 1.21, and 2.94 mSv/MBq for the 15-, 10-, 5-, 1-years-old, and newborn paediatric reference patients. Projected mean effective dose coefficients for 123I-mIBG and 131I-mIBG for adults were 0.014 ± 0.002 mSv/MBq and 0.18 ± 0.04 mSv/MBq, respectively.

CONCLUSION

PET-based derived radiation dosimetry data for 124I-mIBG from this study agreed well with historical projected data from ICRP 53. The effective dose coefficients presented here may aid in guidance for establishing weight-based activity administration protocols.

Quantification performance of silicon photomultiplier-based PET for small 18F-, 68Ga- and 124I-avid lesions in the context of radionuclide therapy planning

PURPOSE

The aim of this study was to investigate conditions for reliable quantification of sub-centimeter lesions with low18F,68Ga, and124I uptake using a silicon photomultiplier-based PET/CT system.

METHODS

A small tumor phantom was investigated under challenging but clinically realistic conditions resembling prostate and thyroid cancer lymph node metastases (6 spheres with 3.7-9.7 mm in diameter, 9 different activity concentrations ranging from about 0.25-25 kBq/mL, and a signal-to-background ratio of 20). Radionuclides with different positron branching ratios and prompt gamma coincidence contributions were investigated. Maximum-, contour-, and oversize-based partial volume effect (PVE) correction approaches were applied. Detection and quantification performance were estimated, considering a ±30 % deviation between imaged-derived and true activity concentrations as acceptable. A standard and a prolonged acquisition time and two image reconstruction algorithms (time-of-flight with/without point spread function modelling) were analyzed. Clinical data were evaluated to assess agreement of PVE-correction approaches indicating lesion quantification validity.

RESULTS

The smallest 3.7-mm sphere was not visible. If the lesions were clearly observed, quantification was, except for a few cases, acceptable using contour- or oversized-based PVE-corrections. Quantification accuracy did not substantially differ between 18F, 68Ga, and 124I. No systematic differences between the analyzed reconstruction algorithms or shorter and larger acquisition times were observed. In the clinical evaluation of 20 lesions, an excellent statistical agreement between oversize- and contour-based PVE-corrections was observed.

CONCLUSIONS

At the lower end of size (<10 mm) and activity concentration ranges of lymph-node metastases, quantification with reasonable accuracy is possible for 18F, 68Ga, and 124I, possibly allowing pre-therapeutic lesion dosimetry and individualized radionuclide therapy planning.

Intraoperative Molecular Positron Emission Tomography Imaging for Intraoperative Assessment of Radical Prostatectomy Specimens

In this prospective two-center feasibility study, we evaluate the diagnostic value of intraoperative ex vivo specimenPET/CT imaging of radical prostatectomy (RP) and lymphadenectomy specimens. Ten patients with high-risk prostate cancer underwent clinical prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) preoperatively on the day of surgery. Six patients received ⁶⁸Ga-PSMA-11 and four ¹⁸F-PSMA-1007. Radioactivity of the resected specimen was measured again using a novel specimenPET/CT device (AURA10; XEOS Medical, Gent, Belgium) developed for intraoperative margin assessment. All index lesions of staging multiparametric magnetic resonance imaging could be visualized. Overall, specimenPET/CT correlated well with conventional PET/CT regarding detection of suspicious tracer foci (Pearson coefficient 0.935). In addition, specimenPET/CT demonstrated all lymph node metastases detected on conventional PET/CT (n = 3), as well as three previously undetected lymph node metastases. Importantly, all positive or close (<1 mm) surgical margins could be visualized in agreement with histopathology. In conclusion, specimenPET/CT enables detection of PSMA-avid lesions and warrants further investigation to tailor RP, based on a good correlation with final pathology. Future trials will prospectively compare ex vivo specimenPET/CT with a frozen section analysis for the detection of positive surgical margins and assessment of biochemical recurrence-free survival.

Patient summary

In this report, we examined prostatectomy and lymphadenectomy specimens for suspicious positron emission tomography (PET) signals after preoperative tracer injection. It was found that in all cases, a good signal could be visualized, with a promising correlation of surface assessment compared with histopathology. We conclude that specimenPET imaging is feasible and may help improve oncological outcomes in the future.

Reduction of emission time for [68Ga]Ga-PSMA PET/CT using the digital biograph vision: a phantom study

BACKGROUND

The aim of this phantom study was to optimize the [⁶⁸Ga]Ga-PSMA PET/CT examination in terms of scan time duration and image reconstruction parameters, in combination with PSF and TOF modelling, in a digital Biograph Vision PET/CT scanner.

METHODS

Three types of phantoms were used: 1) soft-tissue tumor phantom consisting of six spheres mounted in a torso phantom; 2) bone-lung tumor phantom; 3) resolution phantom. Phantom inserts were filled with activity concentrations (ACs) that were derived from clinical data. Phantom data were acquired in list-mode at one bed position. Images with emission data ranging from 30 to 210 s in 30-s increments were reconstructed from a reference image acquired with 3.5-min emission. Iterative image reconstruction (OSEM), point-spread-function (PSF) and time-of-flight (TOF) options were applied using different iterations, Gaussian filters, and voxel sizes. The criteria for image quality was lesion detectability and lesion quantification, evaluated as contrast-to-noise ratio (CNR) and maximum AC (peak AC), respectively. A threshold value of CNR above 6 and percentage maximum AC (peak AC) deviation range of ±20% of the reference image were considered acceptable. The proposed single-bed scan time reduction was projected to a whole-body examination (patient validation scan) using the continuous-bed-motion mode.

RESULTS

Sphere and background ACs of 20 kBq/mL and 1 kBq/mL were selected, respectively. The optimized single-bed scan time was approximately 60 s using OSEM-TOF or OSEM-TOF+PSF (four iterations, 4.0-mm Gaussian filter and almost isotropic voxel size of 3.0-mm side length), resulting in a PET spatial resolution of 6.3 mm for OSEM-TOF and 5.5 mm for OSEM-TOF+PSF. In the patient validation, the maximum percentage difference in lesion quantification between standard and optimized protocol (whole-body scan time of 15 vs. 5 min) was below 19%.

CONCLUSIONS

A reduction of single-bed and whole-body scan time for [⁶⁸Ga]Ga-PSMA PET/CT compared to current recommended clinical acquisition protocols is postulated. Clinical studies are warranted to validate the applicability of this protocol.

Quantitative 99mTc-DPD-SPECT/CT assessment of cardiac amyloidosis

INTRODUCTION

Transthyretin (ATTR) amyloidosis is responsible for the majority of cardiac amyloidosis (CA) cases and can be reliably diagnosed with bone scintigraphy and the visual Perugini score. We aimed to implement a quantification method of cardiac amyloid deposits in patients with suspected cardiac amyloidosis and to compare performance to visual scoring.

METHODS AND MATERIALS

136 patients received 99mTc-DPD-bone scintigraphy including SPECT/CT of the thorax in case of suspicion of cardiac amyloidosis. Imaging phantom studies were performed to determine the scaling factor for standardized uptake value (SUV) quantification from SPECT/CT. Myocardial tracer uptake was quantified in a whole heart volume of interest.

RESULTS

Forty-five patients were diagnosed with CA. A strong relationship between cardiac SUVmax and Perugini score was found (Spearman r 0.75, p < 0.0001). Additionally, tracer uptake in bone decreased with increasing cardiac SUVmax and Perugini score (p < 0.0001). ROC analysis revealed good performance of the SUVmax for the detection of ATTR-CA with AUC of 0.96 ± 0.02 (p < 0.0001) with sensitivity 98.7% and specificity 87.2%.

CONCLUSION

We demonstrate an accessible and accurate quantitative SPECT approach in CA. Quantitative assessment of the cardiac tracer uptake may improve diagnostic accuracy and risk classification. This method may enable monitoring and assessment of therapy response in patients with ATTR amyloidosis.

Lesion Quantification Accuracy of Digital 90Y PET Imaging in the Context of Dosimetry in Systemic Fibroblast Activation Protein Inhibitor Radionuclide Therapy

Therapy with ⁹⁰Y-labeled fibroblast activation protein inhibitors (⁹⁰Y-FAPIs) was recently introduced as a novel treatment concept for patients with solid tumors. Lesion and organ-at-risk dosimetry is part of assessing treatment efficacy and safety and requires reliable quantification of tissue uptake. As ⁹⁰Y quantification is limited by the low internal positron-electron pair conversion rate, the increased effective sensitivity of digital silicon photomultiplier-based PET/CT systems might increase quantification accuracy and, consequently, allow for dosimetry in ⁹⁰Y-FAPI therapy. The aim of this study was to explore the conditions for reliable lesion image quantification in ⁹⁰Y-FAPI radionuclide therapy using a digital PET/CT system. Methods: Two tumor phantoms were filled with ⁹⁰Y solution using different sphere activity concentrations and a constant signal-to-background ratio of 40. The minimum detectable activity concentration was determined, and its dependence on acquisition time (15 vs. 30 min per bed position) and smoothing levels (all-pass vs. 5-mm gaussian filter) was investigated. Quantification accuracy was evaluated at various activity concentrations to estimate the minimum quantifiable activity concentration using contour-based and oversized volume-of-interest-based quantification approaches. A ±20% deviation range between image-derived and true activity concentrations was regarded as acceptable. Tumor dosimetry for 3 patients treated with ⁹⁰Y-FAPI is presented to project the phantom results to clinical scenarios. Results: For a lesion size of 40 mm and a clinical acquisition time of 15 min, both minimum detectable and minimum quantifiable activity concentrations were 0.12 MBq/mL. For lesion sizes of greater than or equal to 30 mm, accurate quantification was feasible for detectable lesions. Only for the smallest 10-mm sphere, the minimum detectable and minimum quantifiable activity concentrations differ substantially (0.43 vs. 1.97 MBq/mL). No notable differences between the 2 quantification approaches were observed. For the investigated tumors, absorbed dose estimates with reliable accuracy were achievable. Conclusion: For lesion sizes and activity concentrations that are expected to be observed in patients treated with ⁹⁰Y-FAPI, quantification with reasonable accuracy is possible. Further dosimetry studies are needed to thoroughly investigate the efficacy and safety of ⁹⁰Y-FAPI therapy.

Joint EANM/SNMMI guideline on radiomics in nuclear medicine : Jointly supported by the EANM Physics Committee and the SNMMI Physics, Instrumentation and Data Sciences Council

PURPOSE

The purpose of this guideline is to provide comprehensive information on best practices for robust radiomics analyses for both hand-crafted and deep learning-based approaches.

METHODS

In a cooperative effort between the EANM and SNMMI, we agreed upon current best practices and recommendations for relevant aspects of radiomics analyses, including study design, quality assurance, data collection, impact of acquisition and reconstruction, detection and segmentation, feature standardization and implementation, as well as appropriate modelling schemes, model evaluation, and interpretation. We also offer an outlook for future perspectives.

CONCLUSION

Radiomics is a very quickly evolving field of research. The present guideline focused on established findings as well as recommendations based on the state of the art. Though this guideline recognizes both hand-crafted and deep learning-based radiomics approaches, it primarily focuses on the former as this field is more mature. This guideline will be updated once more studies and results have contributed to improved consensus regarding the application of deep learning methods for radiomics. Although methodological recommendations in the present document are valid for most medical image modalities, we focus here on nuclear medicine, and specific recommendations when necessary are made for PET/CT, PET/MR, and quantitative SPECT.

F18-PSMA Cerenkov luminescence and flexible autoradiography Imaging in a prostate cancer mouse model and first results of a radical prostatectomy feasibility study in men

Intraoperative identification of positive resection margins (PRMs) in high-risk prostate cancer (PC) needs improvement. Cerenkov luminescence imaging (CLI) with ⁶⁸Ga-PSMA-11 is promising, although limited by low residual activity and artificial signals. Here, we aimed to assess the value of CLI and flexible autoradiography (FAR) with ¹⁸F-PSMA-1007. Methods: Mice bearing subcutaneous PSMA-avid RM1-PGLS tumors were administered ¹⁸F-PSMA-1007, and PET/CT was performed. After the animals had been killed, organs were excised and measured signals in CLI and FAR CLI were correlated with tracer activity concentrations (ACs) obtained from PET/CT. For clinical assessment, 7 high-risk PC patients underwent radical prostatectomy immediately after preoperative ¹⁸F-PSMA PET/CT. Contrast-to-noise ratios (CNRs) were calculated for both imaging modalities in intact specimens and after incision above the index lesion. Results: In the heterotopic in vivo mouse model (n = 5), CLI did not detect any lesion. FAR CLI detected a distinct signal in all mice, with a lowest AC of 7.25 kBq/mL (CNR, 5.48). After incision above the index lesion of the prostate specimen, no increased signal was observed at the cancer area in CLI. In contrast, using FAR CLI, a signal was detectable in 6 of 7 patients. The AC in the missed index lesion was 1.85 kBq/mL, resulting in a detection limit of at least 2.06 kBq/mL. Histopathology demonstrated 2 PRMs, neither of which was predicted by CLI or FAR CLI. Conclusion: ¹⁸F-PSMA FAR CLI was superior to CLI in tracer-related signal detectability. PC was could be visualized in radical prostatectomy down to 2.06 kBq/mL. However, the detection of PRMs was limited. Direct anatomic correlation of FAR CLI is challenging because of the scintillator overlay.

Safety and Efficacy of 90Y-FAPI-46 Radioligand Therapy in Patients with Advanced Sarcoma and Other Cancer Entities

PURPOSE

We report efficacy and safety of 90Y-labeled FAPI-46 (90Y-FAPI-46-RLT) in patients with advanced sarcoma, pancreatic cancer, and other cancer entities.

EXPERIMENTAL DESIGN

Up to four cycles of radioligand therapy (RLT) were offered to patients with (i) progressive metastatic malignancy, (ii) exhaustion of approved therapies, and (iii) high fibroblast activation protein (FAP) expression, defined as SUVmax ≥ 10 in more than 50% of tumor. Primary endpoint was RECIST response after RLT. Secondary endpoints included PET response (PERCIST), overall survival (OS), dosimetry, and safety of FAP-RLT.

RESULTS

Among 119 screened patients, 21 (18%) were found eligible [n = 16/3/1/1 sarcoma/pancreatic cancer/prostate/gastric cancer; 38% Eastern Cooperative Oncology Group (ECOG) ≥ 2] and received 47 90Y-FAPI-46-RLT cycles; 16 of 21 (76%) patients underwent repeat RLT. By RECIST, disease control was confirmed in 8 of 21 patients [38%; 8/16 (50%) of evaluable patients). There was one partial response (PR) and seven stable diseases after RLT. Disease control was associated with prolonged OS (P = 0.013). PERCIST response was noted in 8 of 21 patients [38%; 8/15 (53%) of evaluable patients]. Dosimetry was acquired in 19 (90%) patients. Mean absorbed dose was 0.53 Gy/GBq in kidney, 0.04 Gy/GBq in bone marrow, and <0.14 Gy/GBq in liver and lung. Treatment-related grade 3 or 4 adverse events were observed in 8 (38%) patients with thrombocytopenia (n = 6) and anemia (n = 6) being most prevalent.

CONCLUSIONS

90Y-FAPI-46-RLT was safe and led to RECIST PR in one case as well as stable disease in about one third of patients with initially progressive sarcomas, pancreatic cancer, and other cancers. Discontinuation after the first cycle and a low rate of PR requires future improvement of FAP-RLT.

Radiation Protection and Occupational Exposure on 68Ga-PSMA-11-Based Cerenkov Luminescence Imaging Procedures in Robot-Assisted Prostatectomy

Cerenkov luminescence imaging (CLI) was successfully implemented in the intraoperative context as a form of radioguided cancer surgery, showing promise in the detection of surgical margins during robot-assisted radical prostatectomy. The present study was designed to provide a quantitative description of the occupational radiation exposure of surgery and histopathology personnel from CLI-guided robot-assisted radical prostatectomy after the injection of ⁶⁸Ga-PSMA-11 in a single-injection PET/CT CLI protocol. Methods: Ten patients with preoperative ⁶⁸Ga-PSMA-11 administration and intraoperative CLI were included. Patient dose rate was measured before PET/CT (n = 10) and after PET/CT (n = 5) at a 1-m distance for 4 patient regions (head [A], right side [B], left side [C], and feet [D]). Electronic personal dosimetry (EPD) was used for intraoperative occupational exposure (n = 10). Measurements included the first surgical assistant and scrub nurse at the operating table and the CLI imager/surgeon at the robotic console and encompassed the whole duration of surgery and CLI image acquisition. An estimation of the exposure of histopathology personnel was performed by measuring prostate specimens (n = 8) with a germanium detector. Results: The measured dose rate value before PET/CT was 5.3 ± 0.9 (average ± SD) μSv/h. This value corresponds to a patient-specific dose rate constant for positions B and C of 0.047 μSv/h⋅MBq. The average dose rate value after PET/CT was 1.04 ± 1.00 μSv/h. The patient-specific dose rate constant values corresponding to regions A to D were 0.011, 0.026, 0.024, and 0.003 μSv/h⋅MBq, respectively. EPD readings revealed average personal equivalent doses of 9.0 ± 7.1, 3.3 ± 3.9, and 0.7 ± 0.7 μSv for the first surgical assistant, scrub nurse, and CLI imager/surgeon, respectively. The median germanium detector-measured activity of the prostate specimen was 2.96 kBq (interquartile range, 2.23-7.65 kBq). Conclusion: Single-injection ⁶⁸Ga-PSMA-11 PET/CT CLI procedures are associated with a reasonable occupational exposure level, if kept under 110 procedures per year. Excised prostate specimen radionuclide content was below the exemption level for ⁶⁸Ga. Dose rate-based calculations provide a robust estimation for EPD measurements.

Administration Routes for SSTR-/PSMA- and FAP-Directed Theranostic Radioligands in Mice

The NETTER-1, VISION, and TheraP trials proved the efficacy of repeat intravenous application of small radioligands. Application by subcutaneous, intraperitoneal, or oral routes is an important alternative and may yield comparable or favorable organ and tumor radioligand uptake. Here, we assessed organ and tumor biodistribution for various radioligand application routes in healthy mice and models of cancer expressing somatostatin receptor (SSTR), prostate-specific membrane antigen (PSMA), and fibroblast activation protein (FAP). Methods: Healthy and tumor-bearing male C57BL/6 or NOD SCID γ-mice, respectively, were administered a mean of 6.0 ± 0.5 MBq of ⁶⁸Ga-DOTATOC (RM1-SSTR allograft), 5.3 ± 0.3 MBq of ⁶⁸Ga-PSMA11 (RM1-PSMA allograft), or 4.8 ± 0.2 MBq of ⁶⁸Ga-FAPI46 (HT1080-FAP xenograft) by intravenous, intraperitoneal, subcutaneous, or oral routes. In vivo PET images and ex vivo biodistribution in tumor, organs, and the injection site were assessed up to 5 h after injection. Healthy mice were monitored for up to 7 d after the last scan for signs of stress or adverse reactions. Results: After intravenous, intraperitoneal, and subcutaneous radioligand administration, average residual activity at the injection site was less than 17 percentage injected activity per gram (%IA/g) at 1 h after injection, less than 10 %IA/g at 2 h after injection, and no more than 4 %IA/g at 4 h after injection for all radioligands. After oral administration, at least 50 %IA/g remained within the intestines until 4 h after injection. Biodistribution in organs of healthy mice was nearly equivalent after intravenous, intraperitoneal, and subcutaneous application at 1 h after injection and all subsequent time points (≤1 %IA/g for liver, blood, and bone marrow; 11.2 ± 1.4 %IA/g for kidneys). In models for SSTR-, PSMA- and FAP-expressing cancer, tumor uptake was increased or equivalent for intraperitoneal/subcutaneous versus intravenous injection at 5 h after injection (ex vivo): SSTR, 7.2 ± 1.0 %IA/g (P = 0.0197)/6.5 ± 1.3 %IA/g (P = 0.0827) versus 2.9 ± 0.3 %IA/g, respectively; PSMA, 3.4 ± 0.8 %IA/g (P = 0.9954)/3.9 ± 0.8 %IA/g (P = 0.8343) versus 3.3 ± 0.7% IA/g, respectively; FAP, 1.1 ± 0.1 %IA/g (P = 0.9805)/1.1 ± 0.1 %IA/g (P = 0.7446) versus 1.0 ± 0.2 %IA/g, respectively. Conclusion: In healthy mice, biodistribution of small theranostic ligands after intraperitoneal/subcutaneous application is nearly equivalent to that after intravenous injection. Subcutaneous administration resulted in the highest absolute SSTR tumor and tumor-to-organ uptake as compared with the intravenous route, warranting further clinical assessment.

Phantom-based acquisition time and image reconstruction parameter optimisation for oncologic FDG PET/CT examinations using a digital system

Background

New-generation silicon-photomultiplier (SiPM)-based PET/CT systems exhibit an improved lesion detectability and image quality due to a higher detector sensitivity. Consequently, the acquisition time can be reduced while maintaining diagnostic quality. The aim of this study was to determine the lowest ¹⁸F-FDG PET acquisition time without loss of diagnostic information and to optimise image reconstruction parameters (image reconstruction algorithm, number of iterations, voxel size, Gaussian filter) by phantom imaging. Moreover, patient data are evaluated to confirm the phantom results.

Methods

Three phantoms were used: a soft-tissue tumour phantom, a bone-lung tumour phantom, and a resolution phantom. Phantom conditions (lesion sizes from 6.5 mm to 28.8 mm in diameter, lesion activity concentration of 15 kBq/mL, and signal-to-background ratio of 5:1) were derived from patient data. PET data were acquired on an SiPM-based Biograph Vision PET/CT system for 10 min in list-mode format and resampled into time frames from 30 to 300 s in 30-s increments to simulate different acquisition times. Different image reconstructions with varying iterations, voxel sizes, and Gaussian filters were probed. Contrast-to-noise-ratio (CNR), maximum, and peak signal were evaluated using the 10-min acquisition time image as reference. A threshold CNR value ≥ 5 and a maximum (peak) deviation of ± 20% were considered acceptable. 20 patient data sets were evaluated regarding lesion quantification as well as agreement and correlation between reduced and full acquisition time standard uptake values (assessed by Pearson correlation coefficient, intraclass correlation coefficient, Bland–Altman analyses, and Krippendorff’s alpha).

Results

An acquisition time of 60 s per bed position yielded acceptable detectability and quantification results for clinically relevant phantom lesions ≥ 9.7 mm in diameter using OSEM-TOF or OSEM-TOF+PSF image reconstruction, a 4-mm Gaussian filter, and a 1.65 × 1.65 x 2.00-mm³ or 3.30 × 3.30 x 3.00-mm³ voxel size. Correlation and agreement of patient lesion quantification between full and reduced acquisition times were excellent.

Conclusion

A threefold reduction in acquisition time is possible. Patients might benefit from more comfortable examinations or reduced radiation exposure, if instead of the acquisition time the applied activity is reduced.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09993-4.

Radiation doses from low-dose CT scans in SPECT/CT and PET/CT examinations: A survey in Germany

AIM

Recently, dose reference levels (DRLs) have been defined in Germany for auxiliary low-dose CT scans in hybrid SPECT/CT and PET/CT examinations, based on data from 2016/17. Here, another survey from 2020 was evaluated and compared with the new DRLs as well as with similar surveys from foreign countries.

METHODS

The survey, which had already been conducted in the Nordic countries, queried for various examinations including the following values: patient weight and height, volume CT dose index (CTDI_vol), dose length product (DLP). For each examination, statistical parameters such as the third quartile (Q3) were determined from all submitted CTDI_vol and DLP values. Additionally, for examinations comprising datasets from at least 10 systems, the third quartile (Q3-Med) of the respective median values of each system was calculated. Q3 and Q3-Med were compared with the newly published DRLs from Germany and values from similar studies from other countries.

RESULTS

Data from 15 SPECT/CT and 13 PET/CT systems from 15 nuclear medicine departments were collected. For the following examinations datasets from more than 10 systems were submitted: SPECT lung VQ, SPECT bone, SPECT&PET cardiac, PET brain, PET oncology. Especially for examinations of the thorax and heart, the new DRLs are very strict compared to this study. The CTDI_vol values for examinations of the head were lower in this study than the DRLs prescribe now.

CONCLUSIONS

For certain examination types, there is a need for dose optimization at some clinics and devices in order to take into account the new DRLs in Germany in the future.

Prostate specific membrane antigen-radio guided surgery using Cerenkov luminescence imaging-utilization of a short-pass filter to reduce technical pitfalls

Background

Intraoperative Cerenkov luminescence imaging (CLI) is a novel technique to assess surgical margins in patients undergoing nerve sparing radical prostatectomy (RP). Here, we analyze the efficacy of a 550-nm optical short-pass filter (OF) to improve its performance.

Methods

In this prospective single-center feasibility study ten patients with prostate cancer (PC) were included between December 2019 and April 2020, including three patients without tracer injection as a control group. After preoperative injection of 68-Ga-prostate-specific membrane antigen (PSMA)-11 followed by RP, CLI of the excised prostate and the incised index lesion was performed to visualize the primary tumor lesion. We compared the findings on intraoperative CLI to postoperative histopathology. Furthermore, CLI-intensities determined as tumor to background ratio (TBR) and contrast to noise ratio (CNR) were measured.

Results

Histopathology proved positive surgical margins (PSM) in 3 patients with corresponding findings in CLI. After magnetic resonance imaging (MRI)-informed incision above the index lesion 2 out of 3 prostates demonstrated elevated CLI signals with histopathological confirmation of PC cells. The use of the OF enabled a significant reduction of the area of the regions of interest from a median of 1.80 to 0.15 cm² (reduction by 85%, P=0.005) leading to increased specificity. Signals due to PSMs were not suppressed by the 550-nm OF. The median TBR was reduced from 3.33 to 2.10. In all three patients of the control group elevated CLI intensities were detected at locations with diathermal energy deposition during surgery. After application of the 550-nm OF these were almost totally suppressed with a TBR of 1.10. Measurements of Cerenkov luminescence intensity with the 550-nm OF showed a significant Pearson's correlation of 0.82 between PSM and the elevated TBR (P=0.003) and a significant Pearson's correlation of 0.66 between PSM and elevated CNR (P=0.04). Measurements without the OF did not correlate significantly.

Conclusions

Intraoperative 68-Ga-PSMA CLI in PC is a tool that warrants further investigation to visualize PSM especially in intermediate and high-risk PC. Intraoperative CLI benefits from usage of a 550-nm OF to reduce false-positive signals.

Silicon-photomultiplier-based PET/CT reduces the minimum detectable activity of iodine-124

The radioiodine isotope pair 124I/131I is used in a theranostic approach for patient-specific treatment of differentiated thyroid cancer. Lesion detectability is notably higher for 124I PET (positron emission tomography) than for 131I gamma camera imaging but can be limited for small and low uptake lesions. The recently introduced silicon-photomultiplier-based (SiPM-based) PET/CT (computed tomography) systems outperform previous-generation systems in detector sensitivity, coincidence time resolution, and spatial resolution. Hence, SiPM-based PET/CT shows an improved detectability, particularly for small lesions. In this study, we compare the size-dependant minimum detectable 124I activity (MDA) between the SiPM-based Biograph Vision and the previous-generation Biograph mCT PET/CT systems and we attempt to predict the response to 131I radioiodine therapy of lesions additionally identified on the SiPM-based system. A tumour phantom mimicking challenging conditions (derived from published patient data) was used; i.e., 6 small spheres (diameter of 3.7-9.7 mm), 9 low activity concentrations (0.25-25 kBq/mL), and a very low signal-to-background ratio (20:1). List-mode emission data (single-bed position) were divided into frames of 4, 8, 16, and 30 min. Images were reconstructed with ordinary Poisson ordered-subsets expectation maximization (OSEM), additional time-of-flight (OSEM-TOF) or TOF and point spread function modelling (OSEM-TOF+PSF). The signal-to-noise ratio and the MDA were determined. Absorbed dose estimations were performed to assess possible treatment response to high-activity 131I radioiodine therapy. The signal-to-noise ratio and the MDA were improved from the mCT to the Vision, from OSEM to OSEM-TOF and from OSEM-TOF to OSEM-TOF+PSF reconstructed images, and from shorter to longer emission times. The overall mean MDA ratio of the Vision to the mCT was 0.52 ± 0.18. The absorbed dose estimations indicate that lesions ≥ 6.5 mm with expected response to radioiodine therapy would be detectable on both systems at 4-min emission time. Additional smaller lesions of therapeutic relevance could be detected when using a SiPM-based PET system at clinically reasonable emission times. This study demonstrates that additional lesions with predicted response to 131I radioiodine therapy can be detected. Further clinical evaluation is warranted to evaluate if negative 124I PET scans on a SiPM-based system can be sufficient to preclude patients from blind radioiodine therapy.

68Ga-PSMA-11 PET/CT Improves Tumor Detection and Impacts Management in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the third most frequent cause of cancer-related death. A growing number of local and systemic therapies are available, and accurate staging is critical for management decisions. We assessed the impact of neovasculature imaging by ⁶⁸Ga-PSMA-11 PET/CT on disease staging, prognostic groups, and management of patients with HCC compared with staging with CT. Methods: Forty patients who received imaging with ⁶⁸Ga-PSMA-11 PET/CT for HCC staging between September 2018 and September 2019 were retrospectively included. Management before and after PET scanning was assessed by standardized surveys. The presence of HCC was evaluated by 3 masked readers on a per-patient and per-region basis for PET/CT (PET criteria) and multiphase contrast-enhanced CT (CT criteria) in separate sessions. Lesions were validated by follow-up imaging or histopathology, and progression-free survival was recorded. Endpoints were detection rate and positive predictive value for ⁶⁸Ga-PSMA-11 PET versus CT, interreader reproducibility, and changes in stage, prognostic groups, and management plans. Results: Median age was 65 y (range, 37-81 y), and median Child-Pugh score was 5 (range, 5-9). Most patients were treatment-naïve (27/40, 67.5%). The sensitivity of PET versus CT to identify liver lesions for patients with lesion validation was 31 of 32 (97%) for both modalities, whereas it was 6 of 6 (100%) versus 4 of 6 (67%), respectively, for extrahepatic lesions. PET and CT each had a positive predictive value of 100% at the liver level. PET versus CT stage was congruent in 30 of 40 (75%) patients; upstaging was seen in 8 of 40 patients (20%), whereas 2 of 40 (5%) had downstaging by PET. Intended management changed in 19 of 40 patients (47.5%); 9 of 19 of these patients were found to have detectable distant metastases (47.4%) and assigned stage 4 disease, most of whom were shifted to systemic therapy (8/9, 89%). Two patients underwent ¹⁷⁷Lu-PSMA-617 radioligand therapy. Median progression-free survival was 5.2 mo for the entire cohort; 5.3 mo for PET M0, and 4.7 mo for PET M1 patients, respectively. Conclusion: ⁶⁸Ga-PSMA-11 PET demonstrated higher accuracy than CT in the detection of HCC metastases and was associated with a management change in about half the patient cohort.

Initial clinical experience with 90Y-FAPI-46 radioligand therapy for advanced stage solid tumors: a case series of nine patients

Fibroblast activation protein (FAP) is overexpressed in several solid tumors and therefore represents an attractive target for radiotheranostic applications. Recent investigations demonstrated rapid and high uptake of small-molecule inhibitors of FAP (⁶⁸Ga-FAPI-46) for PET imaging. Here, we report our initial experience of the feasibility and safety of ⁹⁰Y-FAPI-46 for radioligand therapy of extensively pretreated patients with solid tumors. Methods: Patients were considered for ⁹⁰Y-FAPI-46 therapy if they showed both an exhaustion of all approved therapies based on multidisciplinary tumor board decision, and high FAP expression, defined as SUV_max greater than or equal to 10 in more than 50% of all lesions. If tolerated, ⁹⁰Y-FAPI-46 bremsstrahlung scintigraphy was performed after therapy to confirm systemic distribution and focal tumor uptake, and ⁹⁰Y-FAPI-46 PET scans were performed at multiple time points to determine absorbed dose. Blood-based dosimetry was used to determine bone marrow absorbed dose. Adverse events were graded using Common Terminology Criteria for Adverse Events (version 5.0). Results: Nine patients either with metastatic soft-tissue or bone sarcoma (n = 6) or with pancreatic cancer (n = 3) were treated between June 2020 and March 2021. Patients received a median of 3.8 GBq (interquartile range [IQR], 3.25–5.40 GBq) for the first cycle, and 3 patients received subsequent cycles with a median of 7.4 GBq (IQR, 7.3–7.5 GBq). Posttreatment ⁹⁰Y-FAPI-46 bremsstrahlung scintigraphy demonstrated sufficient ⁹⁰Y-FAPI-46 uptake in tumor lesions in 7 of 9 patients (78%). Mean absorbed dose was 0.52 Gy/GBq (IQR, 0.41–0.65 Gy/GBq) in the kidney, 0.04 Gy/GBq (IQR, 0.03–0.06 Gy/GBq) in bone marrow, and less than 0.26 Gy/GBq in the lung and liver. Measured tumor lesions received up to 2.28 Gy/GBq (median, 1.28 Gy/GBq). New laboratory G3 or G4 toxicities were noted in 4 patients (44%, n = 2 patients with thrombocytopenia only, n = 2 patients with new onset of thrombocytopenia and anemia). Other G3 or G4 laboratory-based adverse events occurred in 2 patients or fewer. No acute toxicities attributed to ⁹⁰Y-FAPI-46 were noted. Radiographic disease control was noted in 4 patients (50%). Conclusion: FAP-targeted radioligand therapy with ⁹⁰Y-FAPI-46 was well tolerated, with a low rate of attributable adverse events. Low radiation doses to at-risk organs suggest feasibility of repeat cycles of ⁹⁰Y-FAPI-46. We observed signs of tumor response, but further studies are warranted to determine efficacy and the toxicity profile in a larger cohort.

Estimating the modulating effect of lung tissue in particle therapy using a clinical CT voxel histogram analysis

To treat lung tumours with particle therapy, different additional tasks and challenges in treatment planning and application have to be addressed thoroughly. One of these tasks is the quantification and consideration of the Bragg peak degradation due to lung tissue: As lung is an heterogeneous tissue, the Bragg peak is broadened when particles traverse the microscopic alveoli. These are not fully resolved in clinical CT images and thus, the effect is not considered in the dose calculation. In this work, a correlation between the CT histograms of heterogeneous material and the impact on the Bragg peak curve is presented. Different inorganic materials were scanned with a conventional CT scanner and additionally, the Bragg peak degradation was measured in a proton beam and was then quantified. A model is proposed that allows an estimation of the modulation power by performing a histogram analysis on the CT scan. To validate the model for organic samples, a second measurement series was performed with frozen porcine lunge samples. This allows to investigate the possible limits of the proposed model in a set-up closer to clinical conditions. For lung substitutes, the agreement between model and measurement is within ±0.05 mm and for the organic lung samples, within ±0.15 mm. This work presents a novel, simple and efficient method to estimate if and how much a material or a distinct region (within the lung) is degrading the Bragg peak on the basis of a common clinical CT image. Up until now, only a direct in-beam measurement of the region or material of interest could answer this question.

Beta radioguided surgery: towards routine implementation?

INTRODUCTION

In locally or locally advanced solid tumors, surgery still remains a fundamental treatment method. However, conservative resection is associated with high collateral damage and functional limitations of the patient. Furthermore, the presence of residual tumor tissue following conservative surgical treatment is currently a common cause of locally recurrent cancer or of distant metastases. Reliable intraoperative detection of small cancerous tissue would allow surgeons to selectively resect malignant areas: this task can be achieved by means of image-guided surgery, such as beta radioguided surgery (RGS).

EVIDENCE ACQUISITION

In this paper, a comprehensive review of beta RGS is given, starting from the physical principles that differentiate beta from gamma radiation, that has already its place in nuclear medicine current practice. Also, the recent clinical feasibility of using Cerenkov radiation is discussed.

EVIDENCE SYNTHESIS

Despite being first proposed several decades ago, only in the last years a remarkable interest in beta RGS has been observed, probably driven by the diffusion of PET radio tracers. Today several different approaches are being pursued to assess the effectiveness of such a technique, including both beta+ and beta- emitting radiopharmaceuticals.

CONCLUSIONS

Beta RGS shows some peculiarities that can present it as a very promising complementary technique to standard procedures. Good results are being obtained in several tests, both ex vivo and in vivo. This might however be the time to initiate the trials to demonstrate the real clinical value of these technologies with seemingly clear potential.

Increased longevity due to sexual activity in mole-rats is associated with transcriptional changes in the HPA stress axis

Sexual activity and/or reproduction are associated with a doubling of life expectancy in the long-lived rodent genus Fukomys. To investigate the molecular mechanisms underlying this phenomenon, we analyzed 636 RNA-seq samples across 15 tissues. This analysis suggests that changes in the regulation of the hypothalamic–pituitary–adrenal stress axis play a key role regarding the extended life expectancy of reproductive vs. non-reproductive mole-rats. This is substantiated by a corpus of independent evidence. In accordance with previous studies, the up-regulation of the proteasome and so-called ‘anti-aging molecules’, for example, dehydroepiandrosterone, is linked with enhanced lifespan. On the other hand, several of our results are not consistent with knowledge about aging of short-lived model organisms. For example, we found the up-regulation of the insulin-like growth factor 1/growth hormone axis and several other anabolic processes to be compatible with a considerable lifespan prolongation. These contradictions question the extent to which findings from short-lived species can be transferred to longer-lived ones.

Evaluation of [68Ga]Ga-PSMA PET/CT images acquired with a reduced scan time duration in prostate cancer patients using the digital biograph vision

Aim

[⁶⁸Ga]Ga-PSMA-11 PET/CT allows for a superior detection of prostate cancer tissue, especially in the context of a low tumor burden. Digital PET/CT bears the potential of reducing scan time duration/administered tracer activity due to, for instance, its higher sensitivity and improved time coincidence resolution. It might thereby expand [⁶⁸Ga]Ga-PSMA-11 PET/CT that is currently limited by ⁶⁸Ge/⁶⁸Ga-generator yield. Our aim was to clinically evaluate the influence of a reduced scan time duration in combination with different image reconstruction algorithms on the diagnostic performance.

Methods

Twenty prostate cancer patients (11 for biochemical recurrence, 5 for initial staging, 4 for metastatic disease) sequentially underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT on a digital Siemens Biograph Vision. PET data were collected in continuous-bed-motion mode with a mean scan time duration of 16.7 min (reference acquisition protocol) and 4.6 min (reduced acquisition protocol). Four iterative reconstruction algorithms were applied using a time-of-flight (TOF) approach alone or combined with point-spread-function (PSF) correction, each with 2 or 4 iterations. To evaluate the diagnostic performance, the following metrics were chosen: (a) per-region detectability, (b) the tumor maximum and peak standardized uptake values (SUVmax and SUVpeak), and (c) image noise using the liver’s activity distribution.

Results

Overall, 98% of regions (91% of affected regions) were correctly classified in the reduced acquisition protocol independent of the image reconstruction algorithm. Two nodal lesions (each ≤ 4 mm) were not identified (leading to downstaging in 1/20 cases). Mean absolute percentage deviation of SUVmax (SUVpeak) was approximately 9% (6%) for each reconstruction algorithm. The mean image noise increased from 13 to 21% (4 iterations) and from 10 to 15% (2 iterations) for PSF + TOF and TOF images.

Conclusions

High agreement at 3.5-fold reduction of scan time in terms of per-region detection (98% of regions) and image quantification (mean deviation ≤ 10%) was demonstrated; however, small lesions can be missed in about 10% of patients leading to downstaging (T1N0M0 instead of T1N1M0) in 5% of patients. Our results suggest that a reduction of scan time duration or administered [⁶⁸Ga]Ga-PSMA-11 activities can be considered in metastatic patients, where missing small lesions would not impact patient management. Limitations include the small and heterogeneous sample size and the lack of follow-up.

Comparing lesion detection efficacy and image quality across different PET system generations to optimize the iodine-124 PET protocol for recurrent thyroid cancer

Background

In recurrent differentiated thyroid cancer patients, detectability in ¹²⁴I PET is limited for lesions with low radioiodine uptake. We assess the improvements in lesion detectability and image quality between three generations of PET scanners with different detector technologies. The results are used to suggest an optimized protocol.

Methods

Datasets of 10 patients with low increasing thyroglobulin or thyroglobulin antibody levels after total thyroidectomy and radioiodine therapies were included. PET data were acquired and reconstructed on a Biograph mCT PET/CT (whole-body, 4-min acquisition time per bed position; OSEM, OSEM-TOF, OSEM-TOF+PSF), a non-TOF Biograph mMR PET/MR (neck region, 4 min and 20 min; OSEM), and a new generation Biograph Vision PET/CT (whole-body, 4 min; OSEM, OSEM-TOF, OSEM-TOF+PSF). The 20-min image on the mMR was used as reference to calculate the detection efficacy in the neck region. Image quality was rated on a 5-point scale.

Results

All detected lesions were in the neck region. Detection efficacy was 8/9 (Vision OSEM-TOF and OSEM-TOF+PSF), 4/9 (Vision OSEM), 3/9 (mMR OSEM and mCT OSEM-TOF+PSF), and 2/9 (mCT OSEM and OSEM-TOF). Median image quality was 4 (Vision OSEM-TOF and OSEM-TOF+PSF), 3 (Vision OSEM, mCT OSEM-TOF+PSF, and mMR OSEM 20-min), 2 (mCT OSEM-TOF), 1.5 (mCT OSEM), and 1 (mMR OSEM 4 min).

Conclusion

At a clinical standard acquisition time of 4 min per bed position, the new generation Biograph Vision using a TOF-based image reconstruction demonstrated the highest detectability and image quality and should, if available, be preferably used for imaging of low-uptake lesions. A prolonged acquisition time for the mostly affected neck region can be useful.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00361-y.

Evaluation of 18F-FDG PET/CT images acquired with a reduced scan time duration in lymphoma patients using the digital biograph vision

BACKGROUND

The superior accuracy and sensitivity of 18F-FDG-PET/CT in comparison to morphological imaging alone leads to an upstaging in up to 30% of lymphoma patients. Novel digital PET/CT scanners might enable to reduce administered tracer activity or scan time duration while maintaining diagnostic performance; this might allow for a higher patient throughput or a reduced radiation exposure, respectively. In particular, the radiation exposure reduction is of interest due to the often young age and high remission rate of lymphoma patients.

METHODS

Twenty patients with (suspected) lymphoma (6 for initial staging, 12 after systemic treatment, 2 in suspicion of recurrence) sequentially underwent 18F-FDG-PET/CT examinations on a digital PET/CT (Siemens Biograph Vision) with a total scan time duration of 15 min (reference acquisition protocol) and 5 min (reduced acquisition protocol) using continuous-bed-motion. Both data sets were reconstructed using either standalone time of flight (TOF) or in combination with point spread function (PSF), each with 2 and 4 iterations. Lesion detectability by blinded assessment (separately for supra- and infradiaphragmal nodal lesions and for extranodal lesions), lesion image quantification, and image noise were used as metrics to assess diagnostic performance. Additionally, Deauville Score was compared for all patients after systemic treatment.

RESULTS

All defined regions were correctly classified in the images acquired with reduced emission time, and therefore, no changes in staging were observed. Lesion quantification was acceptable, that is, mean absolute percentage deviation of maximum and peak standardized uptake values were 6.8 and 6.4% (derived from 30 lesions). A threefold reduction of scan time duration led to an increase in image noise from 7.1 to 11.0% (images reconstructed with 4 iterations) and from 4.7 to 7.2% (images reconstructed with 2 iterations). No deviations in Deauville Score were observed.

CONCLUSION

These results suggest that scan time duration or administered tracer activity can be reduced threefold without compromising diagnostic performance. Especially a reduction of administered activity might allow for a lower radiation exposure and better health economics. Larger trials are warranted to confirm our results.

DYNLT1 gene expression is downregulated in whole blood of patients at different Huntington's disease stages

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG nucleotide expansion, which encodes the amino acid glutamine, in the huntingtin gene. HD is characterized by motor, cognitive, and psychiatric dysfunctions. In a previous study, we showed by qPCR that some genes altered in an HD mouse model were also altered in blood of HD patients. These alterations were mainly with respect to the dynein family. Therefore, this study aimed to investigate whether dynein light chain Tctex type 1 (DYNLT1) is altered in HD patients and if there is a correlation between DYNLT1 gene expression changes and disease progression. We assessed the DYNLT1 gene expression in the blood of 19 HD patients and 20 healthy age-matched controls. Also, in 6 of these patients, we analyzed the DYNLT1 expression at two time points, 3 years apart. The DYNLT1 gene expression in the whole blood of HD patients was significantly downregulated and this difference was widened in later stages. These data suggest that DYNLT1 could emerge as a peripheral prognostic indicator in HD and, also, might be a target for potential intervention in the future.

Circulating microRNAs associated with liver fibrosis in chronic hepatitis C patients

A major challenge in hepatitis C research is the detection of early potential for progressive liver disease. MicroRNAs (miRNAs) are small RNAs that regulate gene expression and can be biomarkers of pathological processes. In this study, we compared circulating miRNAs identified in hepatitis C virus (HCV)-infected patients presenting two extremes of liver disease: mild/moderate fibrosis and cirrhosis. The patients in the cirrhosis group subsequently developed hepatocellular carcinoma (HCC). We identified 163 mature miRNAs in the mild/moderate fibrosis group and 171 in the cirrhosis group, with 144 in common to both groups. Differential expression analysis revealed 5 upregulated miRNAs and 2 downregulated miRNAs in the cirrhosis group relative to the mild/moderate fibrosis group. Functional analyses of regulatory networks (target gene and miRNA) identified gene categories involved in cell cycle biological processes and metabolic pathways related to cell cycle, cancer, and apoptosis. These results suggest that the differentially expressed circulating miRNAs observed in this work (miR-215-5p, miR-483-5p, miR-193b-3p, miR-34a-5p, miR-885-5p, miR-26b-5p and miR -197-3p) may be candidates for biomarkers in the prognosis of liver disease.

•

Circulating miRNome was performed in patients infected with HCV-1a or 1b.

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Mature miRNAs were identified in patients with mild/moderate fibrosis and cirrhosis.

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Five upregulated and two downregulated miRNAs were observed in the cirrhosis group.

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Regulatory networks identified gene categories involved in cell cycle.

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A routine baseline circulating biomarkers detection can have a prognostic value.

In vivo biodistribution of calcium phosphate nanoparticles after intravascular, intramuscular, intratumoral, and soft tissue administration in mice investigated by small animal PET/CT

Calcium phosphate nanoparticles were covalently surface-functionalized with the ligand DOTA and loaded with the radioisotope ⁶⁸Ga. The biodistribution of such ⁶⁸Ga-labelled nanoparticles was followed in vivo in mice by positron emission tomography in combination with computer tomography (PET-CT). The biodistribution of ⁶⁸Ga-labelled nanoparticles was compared for different application routes: intravenous, intramuscular, intratumoral, and into soft tissue. The particle distribution was measured in vivo by PET-CT after 5 min, 15 min, 30 min, 1 h, 2 h, and 4 h, and ex vivo after 5 h. After intravenous injection (tail vein), the nanoparticles rapidly entered the lungs with later redistribution into liver and spleen. The nanoparticles remained mostly at the injection site following intramuscular, intratumoral, or soft tissue application, with less than 10 percent being mobilized into the blood stream. STATEMENT OF SIGNIFICANCE: The in vivo biodistribution of DOTA-terminated calcium phosphate nanoparticles was followed by PET/CT. To our knowledge, this is the first study of this kind. Four different application routes of clinical relevance were pursued: Intravascular, intramuscular, intratumoral, and into soft tissue. Given the high importance of calcium phosphate as biomaterial and for nanoparticular drug delivery and immunization, this is most important to assess the biofate of calcium phosphate nanoparticles for therapeutic application and also judge biodistribution of nanoscopic calcium phosphate ceramics, including debris from endoprostheses and related implants.

Intraoperative 68Ga-PSMA Cerenkov Luminescence Imaging for Surgical Margins in Radical Prostatectomy: A Feasibility Study

Our objective was to assess the feasibility and accuracy of Cerenkov luminescence imaging (CLI) for assessment of surgical margins intraoperatively during radical prostatectomy. Methods: A single-center feasibility study included 10 patients with high-risk primary prostate cancer (PC). ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT scans were performed followed by radical prostatectomy and intraoperative CLI of the excised prostate. In addition to imaging the intact prostate, in the first 2 patients the prostate gland was incised and imaged with CLI to visualize the primary tumor. We compared the tumor margin status on CLI to postoperative histopathology. Measured CLI intensities were determined as tumor-to-background ratio. Results: Tumor cells were successfully detected on the incised prostate CLI images as confirmed by histopathology. Three of 10 men had histopathologically positive surgical margins (PSMs), and 2 of 3 PSMs were accurately detected on CLI. Overall, 25 (72%) of 35 regions of interest proved to visualize a tumor signal according to standard histopathology. The median tumor radiance in these areas was 11,301 photons/s/cm²/sr (range, 3,328-25,428 photons/s/cm²/sr), and median tumor-to-background ratio was 4.2 (range, 2.1-11.6). False-positive signals were seen mainly at the prostate base, with PC cells overlaid by benign tissue. PSMA immunohistochemistry revealed strong PSMA staining of benign gland tissue, which impacts measured activities. Conclusion: This feasibility showed that ⁶⁸Ga-PSMA CLI is a new intraoperative imaging technique capable of imaging the entire specimen's surface to detect PC tissue at the resection margin. Further optimization of the CLI protocol, or the use of lower-energy imaging tracers such as ¹⁸F-PSMA, is required to reduce false-positives. A larger study will be performed to assess diagnostic performance.

Post-radiosynovectomy imaging utilizing Erbium-169 citrate

Currently, there is no imaging procedure for radionuclide therapy utilizing Erbium-169 (Er-169). We have recently published the first post-radiosynovectomy imaging of Er-169 citrate in a case report (Farahati et al., 2017). In this study, we performed in-vitro and in-vivo studies to evaluate the feasibility to assess the distribution of Er-169 citrate after radiosynovectomy in fourteen patients with seventeen affected joints treated for refractory chronic synovitis. Post-radiosynovectomy imaging revealed the feasibility of post-radiosynovectomy detection and distribution utilizing Er-169 citrate in all cases. However, additional in-vitro studies including in-vitro imaging, gamma spectrometry and analysis of half-life indicated that emitted gamma-rays of the Ytterbium-169 in the radiopharmaceutical together with bremsstrahlung induced by Er-169 are the imaging source of emitted counts. Post-radiosynovectomy imaging utilizing Er-169 citrate is feasible and should be implemented in the guidelines for theranostics for quality control, patient safety and therapy monitoring.

Technologist Approach to Global Dose Optimization

Nuclear medicine technologists are specialized health professionals who cover a wide range of tasks from clinical routine (including image acquisition and processing, radiopharmaceutical dispensing and administration, patient care, and radioprotection tasks) to leading clinical research in the field of nuclear medicine. As a fundamental concern in all radiation sciences applied to medicine, protection of individuals against the harmful effects of ionizing radiation must be constantly revised and applied by the professionals involved in medical exposures. The acknowledgment that nuclear medicine technologists play a prominent role in patient management and several procedural steps, both in diagnostic and in therapeutic nuclear medicine applications, carries the duty to be trained and knowledgeable on the topic of radiation protection and dose optimization. An overview on selected topics related to dose optimization is presented in this article, reflecting the similarities and particularities of dose reduction-related principles, initiatives, and practicalities from a global perspective.

The effects of press and pulse disturbance by long and short-term pollution on the fish community in the Sinos River, RS, Brazil

The fish fauna of the Sinos River has been subjected to severe pollution since the 1970´s. Continuous discharges of industrial and municipal sewage cause hypoxia and often even fish kills. The objectives of the present study are to assess long-term effects of pollution on the fish community over a time scale of approximately ten years and to investigate recuperation of the fish fauna after a massive fish kill in 2006. To assess the long-term impacts, seasonal sampling was conducted from September 2007 to March 2009 in four sites which were investigated in 1998/99 with the same methodology. The effects of the fish kill were investigated by comparing the present fauna in the affected river stretch with the fauna of an unaffected adjacent river stretch. The collective community properties richness and Shannon diversity changed during the ten year interval in a consistent pattern. Richness and Shannon diversity increased significantly in all sites, abundance values, however, did not. Analysis of species constancy and cluster analysis showed that the differences between the 1998/99 and 2007/09 studies were relatively small. The comparison of the reaches affected by the 2006 fish kills showed a rapid recovery within one year. Probably the Sinos fish fauna suffered the most severe impacts in the 70s of the last century, which could not be documented by this study. After an initial decline, the community displays relatively stable patterns with a tendency of recovery. After a severe fish kill, faunal recovery was rapid, probably favoured by the proximity of unpolluted source areas and physical habitat integrity of the Sinos River.

Potential bird dispersers of Psychotria in a area of Atlantic forest on Ilha Grande, RJ, Southeastern Brazil: a biochemical analysis of the fruits

The present study assessed the fruiting pattern, bird foraging behavior, and sugar content of ripe fruits of two sympatric species of Rubiaceae (Psychotria brasiliensis and P. nuda). This study was carried out in an Atlantic forest area on Ilha Grande, RJ, between August 1998 and July 1999. Fruit production occurred year round, with a peak of mature P. brasiliensis fruits in December 1998 and another of P. nuda in February of 1999. Lipaugus lanioides (Cotingidae), Baryphtengus ruficapillus (Momotidae) and Saltator similis (Emberizidae) made the most frequent foraging visits to fruiting P. brasiliensis, so that L. lanioides and B. ruficapillus removed the fruits with sallying maneuvers while S. similis gleaned the fruits. Lipaugus lanioides was by far the most important consumer, and potentially the main disperser of P. brasiliensis. Birds of this genus are heavy frugivores in the tropical forests and are widely assumed to be important seed dispersers. The fruits were analyzed quantitatively and qualitatively in relation to the amounts of sucrose and starch. Psychotria brasiliensis (the visited species) showed the smallest quantity of sucrose and the highest amount of starch. These findings suggest that what may influence the birds' choice of fruit is the proportion of starch in the Psychotria species studied here rather than the carbohydrate composition.

Sodium channel currents in maturing acutely isolated rat hippocampal CA1 neurones

Sodium channel currents were recorded in excised inside-out patches from immature (P(4-10)) and older (P(20-46)) rat CA1 neurones. Channel conductance was 16.6+/-0.013 pS (P(20-46)) and 19.0+/-0.031 pS (P(4-10)). Opening patterns varied with step voltage and with age. In some patches bursting was apparent at voltages positive to -30 mV. Non-bursting behaviour was more dominant in patches from younger animals. In older animals mean open time (m.o.t.) was best described by two exponentials especially in the older cells; in the immature, there were fewer cases with two exponentials. The time constant of inactivation (tau(h)) estimated in ensemble averages was best described by two exponentials (tau(hf) and tau(hs)) in most patches from older cells. tau(hf) decreased with depolarization; tau(hs) increased in the range -30 to 0 mV. The voltage dependence of tau(hf) in the older cells is identical to that of the single tau(h) found in the younger; the results indicate a dominance of tau(hf) in the younger. Patches from younger cells more often showed one apparent active channel; in such cases, m.o.t. was described by a single exponential. However, in two cases, channels showed bursting behaviour with one of these channels showing a shift between bursting and non-bursting modes. Our findings are consistent with a heterogeneous channel population and with changes in the population in the course of maturation.

Kinetic parameters of calcium currents in maturing acutely isolated CA1 cells

Calcium currents were recorded in CA1 hippocampal cells from immature (P(4-10)) and older (P(22-55)) rats, using whole-cell voltage clamp techniques. Parameters defining the voltage-dependence of activation (tau(m)) and inactivation (tau(h)), steady-state inactivation and activation were determined at both stages of maturation. Current density increased with maturation. A transient low voltage activated (l.v.a.) current was found in P(4-10) cells, but not in the older cells. At voltages less negative than -30 mV, current inactivation was best described by two exponentials (tau(hf), tau(hs)); the ratio of the amplitudes of the two components changed with maturation, with a dominance of the faster component (tau(hf)) in the younger cells. The voltage dependence of tau(hf) followed a simple dependence model, decreased with increasing depolarization, in all cells at both stages of maturation. In P(4-10) cells, tau(hs) was voltage insensitive (range -25 to +30 mV); in P(22-55) cells, the voltage dependence of tau(hs) was found to be complex. Two current components were identified from the voltage dependence of the conductance in both groups. The first, more hyperpolarized component, the l.v.a. current found in P(4-10) cells; this was absent in the older cells, in which we found a component with a different voltage dependence. The voltage dependence of the conductance of the second, more depolarized component did not differ in younger and older cells. In the course of maturation, the steady-state inactivation of the second component underwent a hyperpolarizing shift and a decrease in voltage sensitivity.

Sustained potassium currents in maturing CA1 hippocampal neurones

Whole-cell voltage clamp techniques were used to characterize sustained outward currents in maturing (P4 to P48) acutely isolated rat CA1 hippocampal neurones. Sodium removal and signal subtraction were used to isolate a sodium dependent sustained potassium current (IKNa). Calcium blockade (Co2+), sensitivity to a low TEA dose (0.5 mM) and sensitivity to Charibdotoxin (CTX 25 nM) and Iberiotoxin (IbTX 25 nM), in conjunction with signal subtraction, were used to isolate a sustained current with the characteristics of IC (IKCa). IKNa was found in both immature (P4-5) and older (P > 21) cells; this corresponded, respectively, to 56 +/- 5% and 36 +/- 6% of the outward current in younger and older cells. In the course of maturation, the voltage dependence of activation of IKNa shifted to more hyperpolarized values by approximately 20 mV. In the younger cells (P5-18) there was no evidence for sensitivity to CTX or IbTX. In 55 out of 77 older cells we found a component sensitive to CTX, IbTX, 0.5 mM TEA and Co2+.

The kinetic parameters of sodium currents in maturing acutely isolated rat hippocampal CA1 neurones

Whole-cell voltage clamp techniques were used to characterize the kinetics of INa in immature (P3-5) and older (P > 25) acutely isolated rat CA1 hippocampal neurones. Fast-rising and fast-inactivating currents were recorded at all stages of maturation, evocable from Vm values of -55 to -50 mV. Currents were sensitive to TTX (1 microM) and to sodium removal from the perfusate. Current density and maximum slope conductance increased with maturation. Current decay was described by two exponentials, the faster component dominating at -35 mV or more depolarized Vm values; the ratio fast/slow inactivating component decreased with maturation. The voltage-dependence of conductance was taken as an approximation of m infinity. In younger cells, V1/2 values of the steady-state inactivation (h infinity) and activation curves (m infinity) were depolarized. Shifts of h infinity and m infinity curves were accompanied by shifts in the corresponding tau h and tau m voltage-dependence curves. In younger cells, activation curves had comparatively higher slope factors (Vs), which is an indication of a lower voltage sensitivity of activation. m infinity, tau m, h infinity, and tau h parameters were used to calculate the forward and backward activation and inactivation rate constants (alpha m, beta m, alpha h and beta h). P3-5 cells had relatively higher beta m values accounting for the lower voltage sensitivity of activation. The findings are an indication of a dominant channel variety in the younger cells with a closed state higher probability. The results are consistent with lower depolarization rates previously reported in CA1 cells at early stages of maturation. Faster inactivation due to poor expression of the slower inactivating component may compensate for poorer repolarization mechanisms due to the immaturity of outward currents previously reported at early stages of maturation.

[Applications of problem-based learning in the basic medical curriculum]

This article describes a project, which took place between 1992 and 1994, on the application of problem-based learning to three disciplines of the basic medical curriculum: Biochemistry (1st year) Physiology (2nd year) and physiopathology (3rd year). The main objectives of the project were to bring teaching closer to the future professional reality, to stimulate critical thinking and to facilitate independent learning. Despite differences in content and in teaching materials, the trigger event for learning was information given within a clinical context which was further analyzed in small-group tutorial sessions. The project also included the training of the tutors and the development of audiovisual materials. Although no statistically significant differences were found in the final scores between students taught during this period and before, the first group reported a considerable increase in the motivation to learn which, in the case of Biochemistry, was important to change the passive attitude of most students on entering university. The project also helped to create the appropriate atmosphere for the establishment of an office for medical education in the medical school to support other innovations in the field. With this project we wished to contribute, with a concrete experience, to the reform of medical education in Portugal, by demonstrating that problem-based learning can be used in single disciplines without major changes in the basic curriculum.

Potassium currents in acutely isolated maturing rat hippocampal CA1 neurones

Whole-cell voltage clamp techniques were used to characterize the postnatal development of current amplitude and inactivation and activation kinetics of two potassium currents in acutely isolated CA1 cells from rats P4 to P52: the A-current (IA) and a slow-rising, slow inactivating current (IK). In the course of maturation, changes in the relative proportion of IA and IK currents were observed, the latter becoming a dominant current in older cells. The half-maximal point (Vh) of steady-state inactivation and activation of IA and IK shifted in the course of the first and second postnatal weeks. The shifts were hyperpolarizing in the case of IK, whereas IA shifted to less negative values. The shifts in steady-state inactivation Vh were accompanied by a change in the slope factor (Vs), which is an indication of a modification in the voltage sensitivity of the steady-state inactivation. The kinetics of IK evolve after birth in a fashion that matches the changes in action potential parameters previously reported.

Slow and medium afterhyperpolarizations in maturing rat hippocampal CA1 neurones

The postnatal evolution of the signals underlying the afterhyperpolarization (slow-AHP and medium-AHP) was studied in rat CA1 hippocampal neurones (P10-16, P17-23 and P greater than 26) using in vitro slices. Noradrenaline (NA) and signal subtraction were used to decompose the AHP (m-AHP and s-AHP). The amplitude of the s-AHP was found significant between P10-16 and P17-23 cells; the m-AHP showed no significant change. The time to peak of the s-AHP of the P greater than 26 cells was found to be significantly different from the remaining groups; the m-AHP showed no significant change. The changes in waveform and amplitude of the AHP at this stage were found to be mainly due to the modifications of the slow-AHP.

Afterpotential characteristics and firing patterns in maturing rat hippocampal CA1 neurones in in vitro slices

The postnatal evolution of depolarizing after-potentials (DAPs) and after-hyperpolarizations (AHPs) was studied in rat CA1 hippocampal neurones (5-68 days of age) using in vitro slices. Results were pooled into 4 age groups: P5-9, P10-16, P17-24 and P26-68. In P5-9 cells, DAPs were seen as passive signals, with a time constant similar to the time constant of the membrane. The evolution of the DAP was characterized by a decrease in amplitude, an increase in duration and a change in contour. In P10-16 and P17-24 cells, the DAPs often had a plateau or a hump-like shape which increased the probability of firing and the occurrence of spike doublets. The firing pattern and bursting behaviour of P10-16 CA1 neurones differed from the pattern typical of the adult. P5-9 and P10-16 cells had post-burst AHPs with a smaller amplitude and a more prolonged early phase than at late stages of development.

Determination of ionic permeability coefficients of the plasma membrane of Xenopus laevis oocytes under voltage clamp

1. A method of estimating absolute ionic permeability coefficients which does not depend on the use of impermeant substitutes is reported. 2. The method is based on a pump leak model of the Xenopus laevis oocyte membrane. The procedure consists of measuring, in the same experiment, the pump current and the currents generated under voltage clamp by the partial substitution of one or two ions at a time. For each experimental condition, the measured currents are substituted in a Goldman-Hodgkin-Katz type equation with two unknowns (the permeability coefficients). The set of equations thus generated enables the computation of all the ionic permeability coefficients. 3. The Xenopus oocyte membrane (stages IV and V, Dumont, 1972) has been found to be permeable to conventional ion substitutes such as N-methyl-D-glucamine (NMG), sulphate, isethionate and gluconate. 4. The values for sodium, potassium and chloride permeability coefficients obtained from sixty-eight pooled experiments were, respectively, 5.44, 17.41 and 1.49 x 10(-8) cm s-1. 5. The diffusional currents for sodium, potassium and chloride computed from the experiments referred to above were, respectively, -1.16, 0.69 and -0.038 microA cm-2. 6. A stoichiometry of the Na+-K+ pump exchange of 3/1.8 was computed. 7. The intracellular concentrations of sodium, potassium and chloride ions, as determined by ion-selective microelectrodes, were, respectively, 10.1 +/- 0.66 mM (n = 12), 109.5 +/- 3.3 mM (n = 13) and 37.7 +/- 1.18 mM (n = 19), corresponding to equilibrium potentials of 61, -95 and -28 mV. 8. Since chloride is not at equilibrium across the membrane, we propose that there is an inward uphill Cl- transport.

[The therapeutic approach to drug addicts]

Difficulties of biological, psychological, social and legal nature may be seen involved in the treatment of drug-addict persons. In this study, the major models used in the treatment are analysed, so as so one may arrived at a new model which will better integrate the various factors involved. The major models may be brought down to three: the medical psychiatric model which emphasizes the biological dependency on drugs and which equates drug addiction and "mental illness"; the behavioristic model which utilizes directive conditioning and desensitizing techniques, as well as educational and suggestional means, in order to determine new kinds of behavior; the relational model which takes origin from psychoanalysis and the systemic approach and sponsors a non-directive treatment of the drug-addict through the exploration and work on his personal and social unconscious conflicts, drive and desires, as well as his self-destructive tendencies. To assure the drug-addict a way to assume responsibility for his own behavior and to be free by respecting other people's rights, it is necessary to elaborate an integrative model of treatment which will consider also the anthropological specificity of the problems, referring also to the Brazilian society.