Frontiers in nuclear medicine (Lausanne, Switzerland)最新文献

Introduction: The aim of this study was to investigate the impact of the use of varying input parameters on resulting bone plasma clearance (K_i ) and other kinetic modelling parameters in a group of patients with chronic kidney disease-mineral and bone disorder (CKD-MBD).

Methods: Raw PET/CT data and blood data were systematically analyzed using five different VOIs for the input functions in the left ventricle and in the thoracic aorta. Standardized VOIs were placed in four thoracic vertebrae and the results pooled and averaged. The basic image-derived input functions (IDIFs) were corrected for partial volume effect and spill-over and modified by substitution of the terminal image exponential with the corresponding plasma-exponentials derived from blood samples. K_i was then calculated using both a non-linear regression (NLR) analysis and a graphical Patlak analysis and compared.

Results: Our original results were reproducible with an inter-observer difference of approximately 6%. The correction factors varied with the VOI volumes from 0.73 ± 0.17 for the largest LV-VOI (48.7 ± 25.3 cm³) to 0.99 ± 0.10 for the AO-VOI (3.4 ± 1.2 cm³). The mean NLR-K_i results varied between 0.0378 ± 0.0112 and 0.0432 ± 0.0095 ml/min ml^-1 with a fixed vB and 0.0408 ± 0.0111 and 0.045 ± 0.0102 ml/min ml^-1 with a free-fitted vB. The corresponding Patl-K_i -results varied between 0.0302 ± 0.0071 and 0.0325 ± 0.0070 ml/min ml^-1, having lesser differences and variances. The input functions with least variance and mean differences compared with NLR results were derived from the left ventricle with a VOI volume of 19.2 ± 11.3 cm³ corrected for PVE and Bg with a mean K_i -difference: 0.0097 ± 0.0370 ml/min ml^-1 and 95% confidence limits (-0.023 to 0.004).

Conclusions: Our results indicated that a VOI with a volume of approximately 20 cm³ with a correction factor of 0.83 ± 0.13 results in Patlak results with the least variance and difference compared with the NLR results. The use of free-fitted vB in the NLR analysis showed the most robust results in all input series. The Patlak results were in comparison generally lower than the NLR results (-17.3% to -23.4%) but very robust across the various input series and with results comparable to previously published data and are therefore recommended for future analysis.

Gallium-68 fibroblast activation protein inhibitor [(⁶⁸Ga)Ga-FAPI] is a new radiopharmaceutical positioning itself as the preferred agent in patients with malignant tumours, competing with 2-Deoxy-2-[18F]fluoro-d-glucose [2-(¹⁸F)FDG] using positron emission tomography (PET). While imaging oncology patients with [⁶⁸Ga]Ga-FAPI PET, incidental uptake of [⁶⁸Ga]Ga-FAPI has been detected in the myocardium. This review summarises original research studies associating the visualisation of FAPI-based tracers in the myocardium with underlying active cardiovascular disease.

Personalised dosimetry based on molecular imaging is a field that has grown exponentially in the last decade due to the increasing success of Radioligand Therapy (RLT). Despite advances in imaging-based 3D dose estimation, the administered dose of a therapeutic radiopharmaceutical for RLT is often non-personalised, with standardised dose regimens administered every 4-6 weeks. Biodosimetry markers, such as chromosomal aberrations, could be used alongside image-based dosimetry as a tool for individualised dose estimation to further understand normal tissue toxicity and refine the administered dose. In this review we give an overview of biodosimetry markers that are used for blood dose estimation, followed by an overview of their current results when applied in RLT patients. Finally, an in-depth discussion will provide a perspective on the potential for the use of biodosimetry in the nuclear medicine clinic.

Interest and research into radiopharmaceutical extravasation concepts has risen with the increase in use of radiopharmaceutical therapies, growing access to novel molecular imaging agents, and recent regulatory controversies. This mini-review will examine the literature of the last twenty years to summarize the history of radiopharmaceutical extravasations, determine key trends in imaging and therapies, and highlight critical gaps in research that currently exist. The intent of this work is to provide a summary of this complex topic that helps build awareness and promotes new innovations in this interesting aspect of theranostic radiopharmaceuticals.

Fibroblast activation protein (FAP) is a type-II membrane bound glycoprotein specifically expressed by activated fibroblasts almost exclusively in pathological conditions including arthritis, fibrosis and cancer. FAP is overexpressed in cancer-associated fibroblasts (CAFs) located in tumor stroma, and is known to be involved in a variety of tumor-promoting activities such as angiogenesis, proliferation, resistance to chemotherapy, extracellular matrix remodeling and immunosuppression. In most cancer types, higher FAP expression is associated with worse clinical outcomes, leading to the hypothesis that FAP activity is involved in cancer development, cancer cell migration, and cancer spread. Recently, various high selectivity FAP inhibitors (FAPIs) have been developed and subsequently used for positron emission tomography (PET) imaging of different pathologies. Considering the paucity of widely available and especially mainstream reliable radioligands in brain cancer PET imaging, and the poor survival rates of patients with certain types of brain cancer such as glioblastoma, FAPI-PET represents a major development in enabling the detection of small primary or metastatic lesions in the brain due to its biological characteristics and low background accumulation. In this work, we aim to summarize the potential avenues for use of FAPI-PET, from the basic biological processes to oncologic imaging and with a main focus on brain imaging.

Nuclear Medicine is witnessing a revolution across a large spectrum of patient care applications, hardware, software and novel radiopharmaceuticals. We propose to offer a framework of the nuclear medicine practice of the future that incorporates multiple novelties and coined as the NEW (nu) Clear medicine. All these new developments offer a significant clarity and real clinical impact, and we need a concerted effort from all stakeholders in the field for bedside implementation and success.

There is a growing use of radionuclide therapy for the medical care of oncology patients, where radioactive pharmaceuticals are used to target and treat various cancer types. This paper provides a brief overview illustrating the spectrum of ongoing and recently completed radionuclide therapy clinical trials in oncology. The trials selected highlight the potential of radionuclide therapies to provide a promising treatment option across a spectrum of cancer patients, while also discussing the importance of patient selection and monitoring, as well as potential side effects and safety concerns. Ultimately, the results of these trials will be crucial in determining the future use of radionuclide therapies in cancer treatment.

Introduction: To investigate and optimize the SPECTRE (Single Photon Emission Computed Theranostic REconstruction) reconstruction approach, using the hybrid kernelised expectation maximization (HKEM) algorithm implemented in the software for tomographic image reconstruction (STIR) software library, and to demonstrate the feasibility of performing algorithm exploration and optimization in 2D. Optimal SPECTRE parameters were investigated for the purpose of improving SPECT-based radionuclide therapy (RNT) dosimetry estimates.

Materials and methods: Using the NEMA IEC body phantom as the test object, SPECT data were simulated to model an early and late imaging time point following a typical therapeutic dose of 8 GBq of ¹⁷⁷Lu. A theranostic ⁶⁸Ga PET-prior was simulated for the SPECTRE reconstructions. The HKEM algorithm parameter space was investigated for SPECT-unique and PET-SPECT mutual features to characterize optimal SPECTRE parameters for the simulated data. Mean and maximum bias, coefficient of variation (COV %), recovery, SNR and root-mean-square error (RMSE) were used to facilitate comparisons between SPECTRE reconstructions and OSEM reconstructions with resolution modelling (OSEM_RM). 2D reconstructions were compared to those performed in 3D in order to evaluate the utility of accelerated algorithm optimization in 2D. Segmentation accuracy was evaluated using a 42% fixed threshold (FT) on the 3D reconstructed data.

Results: SPECTRE parameters that demonstrated improved image quality and quantitative accuracy were determined through investigation of the HKEM algorithm parameter space. OSEM_RM and SPECTRE reconstructions performed in 2D and 3D were qualitatively and quantitatively similar, with SPECTRE showing an average reduction in background COV % by a factor of 2.7 and 3.3 for the 2D case and 3D case respectively. The 42% FT analysis produced an average % volume difference from ground truth of 158% and 26%, for the OSEM_RM and SPECTRE reconstructions, respectively.

Conclusions: The SPECTRE reconstruction approach demonstrates significant potential for improved SPECT image quality, leading to more accurate RNT dosimetry estimates when conventional segmentation methods are used. Exploration and optimization of SPECTRE benefited from both fast reconstruction times afforded by first considering the 2D case. This is the first in-depth exploration of the SPECTRE reconstruction approach, and as such, it reveals several insights for reconstructing SPECT data using PET side information.

Purpose: The aim of this retrospective analysis was to assess the diagnostic accuracy of the latest-generation digital positron emission tomography/computed tomography (PET/CT) scanner in the detection of cervical lymph node metastasis in patients undergoing staging work-up for head and neck cancer.

Materials and methods: A total of 55 consecutive patients with head and neck cancer at our institution who had a PET/CT after installation of the latest-generation PET/CT (Siemens Biograph Vision) who subsequently underwent surgical neck dissection were included. The nodal station location and number of reported PET/CT-positive metastatic lymph nodes were compared to a gold standard of final surgical pathology after neck dissection.

Results: In total, 188 neck levels and 1,373 lymph nodes were resected; 56 neck levels (118 nodes) in 31 (56%) patients contained nodal metastases on surgical pathology. On a nodal level-by-level analysis, the overall sensitivity for the detection of lymph node metastases on the latest-generation PET/CT scanner was 96.4% and the specificity was 86.4%. The sensitivity and specificity for the neck side analysis were 94.0% and 63.7%, and for the individual patient analysis were 100% and 71%, respectively.

Conclusions: In this single-institution study, latest-generation PET/CT had a high sensitivity and moderate to high specificity for detecting cervical node metastasis in head and neck cancer. Compared to data from older PET/CT scanners, the sensitivity of the latest-generation PET/CT was slightly higher, while the specificity was similar or slightly lower. Physicians involved in the management of head and neck cancer should be aware of possible changes in the overall diagnostic accuracy when changing to a latest-generation PET/CT scanner.