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Cancers Dec 2021Developments throughout the history of nuclear medicine have involved improvements in both instrumentation and radionuclides, which have been intertwined.... (Review)
Review
Developments throughout the history of nuclear medicine have involved improvements in both instrumentation and radionuclides, which have been intertwined. Instrumentation developments always occurred during the search to improving devices' sensitivity and included advances in detector technology (with the introduction of cadmium zinc telluride and digital Positron Emission Tomography-PET-devices with silicon photomultipliers), design (total body PET) and configuration (ring-shaped, Single-Photon Emission Computed Tomography (SPECT), Compton camera). In the field of radionuclide development, we observed the continual changing of clinically used radionuclides, which is sometimes influenced by instrumentation technology but also driven by availability, patient safety and clinical questions. Some areas, such as tumour imaging, have faced challenges when changing radionuclides based on availability, when this produced undesirable clinical findings with the introduction of unclear focal uptakes and unspecific uptakes. On the other end of spectrum, further developments of PET technology have seen a resurgence in its use in nuclear cardiology, with rubidium-82 from strontium-82/rubidium-82 generators being the radionuclide of choice, moving away from SPECT nuclides thallium-201 and technetium-99m. These continuing improvements in both instrumentation and radionuclide development have helped the growth of nuclear medicine and its importance in the ever-evolving range of patient care options.
PubMed: 34944803
DOI: 10.3390/cancers13246183 -
Medical Physics Oct 2023Positron probes can accurately localize malignant tumors by directly detecting positrons emitted from positron-emitting radiopharmaceuticals that accumulate in malignant...
BACKGROUND
Positron probes can accurately localize malignant tumors by directly detecting positrons emitted from positron-emitting radiopharmaceuticals that accumulate in malignant tumors. In the conventional method for direct positron detection, multilayer scintillator detection and pulse shape discrimination techniques are used. However, some γ-rays cannot be distinguished by conventional methods. Accordingly, these γ-rays are misidentified as positrons, which may increase the error rate of positron detection.
PURPOSE
To analyze the energy distribution in each scintillator of the multilayer scintillator detector to distinguish true positrons and γ-rays and to improve the positron detection algorithm by discriminating true and false positrons.
METHODS
We used Autoencoder, an unsupervised deep learning architecture, to obtain the energy distribution data in each scintillator of the multilayer scintillator detector. The Autoencoder was trained to separate the combined signals generated from the multilayer scintillator detector into two signals of each scintillator. An energy window was then applied to the energy distribution obtained using the trained Autoencoder to distinguish true positrons from false positrons. Finally, the performance of the proposed method and conventional positron detection algorithm was evaluated in terms of the sensitivity and error rate for positron detection.
RESULTS
The energy distribution map obtained using the trained Autoencoder was proven to be similar to that of the simulated results. Furthermore, the proposed method demonstrated a 29.79% (+0.42%p) increase in positron detection sensitivity compared to the conventional method, both having an equal error rate of 0.48%. However, when both methods were set to have the same sensitivity of 1.83%, the proposed method had an error rate that was 25.0% (-0.16%p) lower than that of the conventional method.
CONCLUSIONS
We proposed and developed an Autoencoder-based positron detection algorithm that can discriminate between true and false positrons with a smaller error rate than conventional methods. We verified that the proposed method could increase the positron detection sensitivity while maintaining a low error rate compared to the conventional method. If the proposed algorithm is implemented in handheld positron detection probes or cameras, diseases such as cancers can be more accurately localized in a shorter time compared with using traditional methods.
Topics: Humans; Positron-Emission Tomography; Deep Learning; Beta Particles; Algorithms; Neoplasms
PubMed: 37469146
DOI: 10.1002/mp.16634 -
Journal of Personalized Medicine Oct 2020Molecular radiotherapy, or targeted radionuclide therapy, uses systemically administered drugs bearing a suitable radioactive isotope, typically a beta emitter. These... (Review)
Review
Molecular radiotherapy, or targeted radionuclide therapy, uses systemically administered drugs bearing a suitable radioactive isotope, typically a beta emitter. These are delivered via metabolic or other physiological pathways to cancer cells in greater concentrations than to normal tissues. The absorbed radiation dose in tumour deposits causes chromosomal damage and cell death. A partner radiopharmaceutical, most commonly the same vector labelled with a different radioactive atom, with emissions suitable for gamma camera or positron emission tomography imaging, is used to select patients for treatment and to assess response. The use of these pairs of radio-labelled drugs, one optimised for therapy, the other for diagnostic purposes, is referred to as . Theragnostics is increasingly moving away from a fixed number of defined activity administrations, to a much more individualised or personalised approach, with the aim of improving treatment outcomes, and minimising toxicity. There is, however, still significant scope for further progress in that direction. The main tools for personalisation are the following: imaging biomarkers for better patient selection; predictive and post-therapy dosimetry to maximise the radiation dose to the tumour while keeping organs at risk within tolerance limits; imaging for assessment of treatment response; individualised decision making and communication about radiation protection, adjustments for toxicity, inpatient and outpatient care.
PubMed: 33081161
DOI: 10.3390/jpm10040174 -
European Radiology Oct 2023Tumor dosimetry with somatostatin receptor-targeted peptide receptor radionuclide therapy (SSTR-targeted PRRT) by Lu-DOTATATE may contribute to improved treatment... (Review)
Review
OBJECTIVES
Tumor dosimetry with somatostatin receptor-targeted peptide receptor radionuclide therapy (SSTR-targeted PRRT) by Lu-DOTATATE may contribute to improved treatment monitoring of refractory meningioma. Accurate dosimetry requires reliable and reproducible pretherapeutic PET tumor segmentation which is not currently available. This study aims to propose semi-automated segmentation methods to determine metabolic tumor volume with pretherapeutic Ga-DOTATOC PET and evaluate SUV-derived values as predictive factors for tumor-absorbed dose.
METHODS
Thirty-nine meningioma lesions from twenty patients were analyzed. The ground truth PET and SPECT volumes (Vol and Vol) were computed from manual segmentations by five experienced nuclear physicians. SUV-related indexes were extracted from Vol and the semi-automated PET volumes providing the best Dice index with Vol (Vol) across several methods: SUV absolute-value (2.3)-threshold, adaptative methods (Jentzen, Otsu, Contrast-based method), advanced gradient-based technique, and multiple relative thresholds (% of tumor SUV, hypophysis SUV, and meninges SUV) with optimal threshold optimized. Tumor-absorbed doses were obtained from the Vol, corrected for partial volume effect, performed on a 360° whole-body CZT-camera at 24, 96, and 168 h after administration of Lu-DOTATATE.
RESULTS
Vol was obtained from 1.7-fold meninges SUV (Dice index 0.85 ± 0.07). SUV and total lesion uptake (SUVxlesion volume) showed better correlations with tumor-absorbed doses than SUV when determined with the Vol (respective Pearson correlation coefficients of 0.78, 0.67, and 0.56) or Vol (0.64, 0.66, and 0.56).
CONCLUSION
Accurate definition of pretherapeutic PET volumes is justified since SUV-derived values provide the best tumor-absorbed dose predictions in refractory meningioma patients treated by Lu-DOTATATE. This study provides a semi-automated segmentation method of pretherapeutic Ga-DOTATOC PET volumes to achieve good reproducibility between physicians.
CLINICAL RELEVANCE STATEMENT
SUV-derived values from pretherapeutic Ga-DOTATOC PET are predictive of tumor-absorbed doses in refractory meningiomas treated by Lu-DOTATATE, justifying to accurately define pretherapeutic PET volumes. This study provides a semi-automated segmentation of Ga-DOTATOC PET images easily applicable in routine.
KEY POINTS
• SUV-derived values from pretherapeutic Ga-DOTATOC PET images provide the best predictive factors of tumor-absorbed doses related to Lu-DOTATATE PRRT in refractory meningioma. • A 1.7-fold meninges SUV segmentation method used to determine metabolic tumor volume on pretherapeutic Ga-DOTATOC PET images of refractory meningioma treated by Lu-DOTATATE is as efficient as the currently routine manual segmentation method and limits inter- and intra-observer variabilities. • This semi-automated method for segmentation of refractory meningioma is easily applicable to routine practice and transferrable across PET centers.
Topics: Humans; Meningioma; Receptors, Somatostatin; Gallium Radioisotopes; Reproducibility of Results; Octreotide; Positron-Emission Tomography; Meningeal Neoplasms; Organometallic Compounds; Neuroendocrine Tumors
PubMed: 37148355
DOI: 10.1007/s00330-023-09697-8 -
Radiological Physics and Technology Mar 2023
Topics: Gamma Cameras; Nuclear Medicine; Radionuclide Imaging; Physics; Positron-Emission Tomography
PubMed: 36534344
DOI: 10.1007/s12194-022-00693-z -
Nuclear Medicine and Biology Jan 2021Rapid imaging acquisition, high spatial resolution and sensitivity, powered by advancements in solid-state detector technology, are significantly changing the... (Review)
Review
Rapid imaging acquisition, high spatial resolution and sensitivity, powered by advancements in solid-state detector technology, are significantly changing the perspective of single photon emission tomography (SPECT). In particular, this evolutionary step is fueling a rediscovery of technetium-99m, a still unique radionuclide within the nuclear medicine scenario because of its ideal nuclear properties and easy preparation of its radiopharmaceuticals that does not require a costly infrastructure and complex procedures. Scope of this review is to show that the arsenal of technetium-99m radiopharmaceuticals is already equipped with imaging agents that may complement and integrate the role played by analogous tracers developed for positron emission tomography (PET). These include, in particular, somatostatin (SST) and prostate-specific membrane antigen (PSMA) receptor targeting agents, and a number of peptide-derived radiopharmaceuticals. Additionally, these recent technological developments, combined with new myocardial perfusion tracers having more favorable biodistribution and pharmacokinetic properties as compared to current commercial agents, may also reinvigorate the prevailing position still hold by technetium-99m radiopharmaceuticals in nuclear cardiology.
Topics: Animals; Humans; Radionuclide Imaging; Radiopharmaceuticals; Technetium
PubMed: 32475681
DOI: 10.1016/j.nucmedbio.2020.05.005 -
Physics in Medicine and Biology May 2021Built on top of the Geant4 toolkit, GATE is collaboratively developed for more than 15 years to design Monte Carlo simulations of nuclear-based imaging systems. It is,... (Review)
Review
Built on top of the Geant4 toolkit, GATE is collaboratively developed for more than 15 years to design Monte Carlo simulations of nuclear-based imaging systems. It is, in particular, used by researchers and industrials to design, optimize, understand and create innovative emission tomography systems. In this paper, we reviewed the recent developments that have been proposed to simulate modern detectors and provide a comprehensive report on imaging systems that have been simulated and evaluated in GATE. Additionally, some methodological developments that are not specific for imaging but that can improve detector modeling and provide computation time gains, such as Variance Reduction Techniques and Artificial Intelligence integration, are described and discussed.
Topics: Artificial Intelligence; Computer Simulation; Monte Carlo Method; Software; Tomography, X-Ray Computed
PubMed: 33770774
DOI: 10.1088/1361-6560/abf276 -
Current Problems in Cancer Oct 2021The concept of personalized medicine has been steadily growing for the past decades. Monoclonal antibodies (mAbs) are undoubtedly playing an important role in the... (Review)
Review
The concept of personalized medicine has been steadily growing for the past decades. Monoclonal antibodies (mAbs) are undoubtedly playing an important role in the transition away from conventional medical practice to a more tailored approach to deliver the best therapy with the highest safety margin to a specific patient. In certain instances, mAbs and antibody drug conjugates (ADCs) may represent the preferred therapeutic option for several types of cancers due to their high specificity and affinity to the antigen. Monoclonal antibodies can be labeled with specific radionuclides well-suited for PET (Positron Emission Tomography) or gamma camera scintigraphy. The use of radiolabeled mAbs allows the interrogation of specific biomarkers and assessment of tumor heterogeneity in vivo by a single diagnostic imaging scan that includes the whole-body in the field-of-view. Moreover, the same mAb can then be radiolabeled with an analogous radionuclide for the delivery of beta-minus radiation or alpha-particles as part of a radioimmunotherapy (RIT) approach. However, the path to develop, validate, and implement mAb-based radiopharmaceuticals from bench-to-bedside is complex due to the extensive pre-clinical experiments and toxicological studies required, and the necessity of labor-intensive clinical trials that often require multi-time-point imaging and blood draws for internal radiation dosimetry and pharmacokinetics. As more mAb-based radiopharmaceuticals have been developed and evaluated, the opportunities and limitations offered by mAbs have become better defined. Our aim with this manuscript is therefore to provide an overview of the recent advances in the development of mAb-based radiopharmaceuticals and their clinical applications in Oncology.
Topics: Antibodies, Monoclonal; Humans; Neoplasms; Positron Emission Tomography Computed Tomography; Precision Medicine; Radioimmunotherapy; Radiopharmaceuticals
PubMed: 34657748
DOI: 10.1016/j.currproblcancer.2021.100796 -
Scientific Reports Feb 2022For radiological diagnosis and radionuclide therapy, X-ray and gamma-ray imaging technologies are essential. Single-photon emission tomography (SPECT) and positron...
For radiological diagnosis and radionuclide therapy, X-ray and gamma-ray imaging technologies are essential. Single-photon emission tomography (SPECT) and positron emission tomography (PET) play essential roles in radiological diagnosis, such as the early detection of tumors. Radionuclide therapy is also rapidly developing with the use of these modalities. Nevertheless, a limited number of radioactive tracers are imaged owing to the limitations of the imaging devices. In a previous study, we developed a hybrid Compton camera that conducts simultaneous Compton and pinhole imaging within a single system. In this study, we developed a system that simultaneously realizes three modalities: Compton, pinhole, and PET imaging in 3D space using multiple hybrid Compton cameras. We achieved the simultaneous imaging of Cs-137 (Compton mode targeting 662 keV), Na-22 (PET mode targeting 511 keV), and Am-241 (pinhole mode targeting 60 keV) within the same field of view. In addition, the imaging of Ga-67 and In-111, which are used in various diagnostic scenarios, was conducted. We also verified that the 3D distribution of the At-211 tracer inside a mouse could be imaged using the pinhole mode.
PubMed: 35169183
DOI: 10.1038/s41598-022-06401-6