-
Seminars in Nuclear Medicine May 2010Noninvasive molecular imaging approaches include nuclear, optical, magnetic resonance imaging, computed tomography, ultrasound, and photoacoustic imaging, which require... (Review)
Review
Noninvasive molecular imaging approaches include nuclear, optical, magnetic resonance imaging, computed tomography, ultrasound, and photoacoustic imaging, which require accumulation of a signal delivered by a probe at the target site. Monoclonal antibodies are high affinity molecules that can be used for specific, high signal delivery to cell surface molecules. However, their long circulation time in blood makes them unsuitable as imaging probes. Efforts to improve antibodies pharmacokinetics without compromising affinity and specificity have been made through protein engineering. Antibody variants that differ in antigen binding sites and size have been generated and evaluated as imaging probes to target tissues of interest. Fast clearing fragments, such as single-chain variable fragment (scFv; 25 kDa), with 1 antigen-binding site (monovalent) demonstrated low accumulation in tumors because of the low exposure time to the target. Using scFv as building block to produce larger, bivalent fragments, such as scFv dimers (diabodies, 50 kDa) and scFv-fusion proteins (80 kDa minibodies and 105 kDa scFv-Fc), resulted in higher tumor accumulation because of their longer residence time in blood. Imaging studies with these fragments after radiolabeling have demonstrated excellent, high-contrast images in gamma cameras and positron emission tomography scanners. Several studies have also investigated antibody fragments conjugated to fluorescence (near infrared dyes), bioluminescence (luciferases), and quantum dots for optical imaging and iron oxides nanoparticles for magnetic resonance imaging. However, these studies indicate that there are several factors that influence successful targeting and imaging. These include stability of the antibody fragment, the labeling chemistry (direct or indirect), whether critical residues are modified, the number of antigen expressed on the cell, and whether the target has a rapid recycling rate or internalizes upon binding. The preclinical data presented are compelling, and it is evident that antibody-based molecular imaging tracers will play an important future role in the diagnosis and management of cancer and other diseases.
Topics: Antibodies, Monoclonal; Humans; Image Enhancement; Isotope Labeling; Molecular Probe Techniques; Radioimmunodetection; Radiopharmaceuticals; Tomography, Emission-Computed
PubMed: 20350626
DOI: 10.1053/j.semnuclmed.2009.12.005 -
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 -
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 -
Ultramicroscopy Jun 2019The cryoEM method Microcrystal Electron Diffraction (MicroED) involves transmission electron microscope (TEM) and electron detector working in synchrony to collect...
The cryoEM method Microcrystal Electron Diffraction (MicroED) involves transmission electron microscope (TEM) and electron detector working in synchrony to collect electron diffraction data by continuous rotation. We previously reported several protein, peptide, and small molecule structures by MicroED using manual control of the microscope and detector to collect data. Here we present a procedure to automate this process using a script developed for the popular open-source software package SerialEM. With this approach, SerialEM coordinates stage rotation, microscope operation, and camera functions for automated continuous-rotation MicroED data collection. Depending on crystal and substrate geometry, more than 300 datasets can be collected overnight in this way, facilitating high-throughput MicroED data collection for large-scale data analyses.
Topics: Cryoelectron Microscopy; Electrons; Microscopy, Electron, Transmission; Peptides; Proteins; Software
PubMed: 30986656
DOI: 10.1016/j.ultramic.2019.03.009 -
Indian Journal of Nuclear Medicine :... Nov 2018Evidence-based historical accounts of critical events, which shaped nuclear medicine in India today, are presented in this article. There was parallel activity happening... (Review)
Review
Evidence-based historical accounts of critical events, which shaped nuclear medicine in India today, are presented in this article. There was parallel activity happening in the northern and western region of India in the early 60s. Radiation Medicine Center (RMC) at Mumbai inaugurated in September 1963 by Dr. Bhabha; and Institute of Nuclear Medicine and Allied Sciences, Delhi dedicated to the nation in February 1964. The isotope division of Bhabha Atomic Research Center endured as the backbone in the supply of indigenously produced medical radioisotopes in research reactors APSARA (1958) and CIRUS (1960). Design and dispatch of economical generators (loaded with low specific activity Mo) with indigenously designed solvent extraction (Methyl Ethyl Ketone) technique had led to rapid growth of nuclear medicine facilities in the country. As per recently released list (July 2018) of the Atomic Energy Regulatory Board, there are 293 nuclear medicine departments in the country. Of which 14% are in the government sector, and the remaining 86% are under private ownership. There are currently 233 functioning gamma cameras (Single-photon emission computed tomography [SPECT]/SPECT-computed tomography [CT]) units in India since 1969 when the first gamma camera was commissioned at RMC. The first medical cyclotron (2002) and first positron emission tomography (PET) (2002) and first PET-CT (2004) in Mumbai had triggered revolution of molecular imaging in India. There are 222 PET-CT, 3 PET-magnetic resonance imaging scanners, and 19 cyclotrons operating currently. India has witnessed relatively slower headways in terms of high dose radionuclide therapy facilities. After first indoor facility at RMC in 1964, only 92 radionuclide therapy (isolation) wards have come up with no more than 200 beds for the entire country in the last 54 years. India started Delhi university approved structured postgraduate diploma in nuclear medicine in 1963 at the Institute of Nuclear Medicine and Allied Sciences (INMAS), first of its kind course in the world at that time. RMC started Mumbai University recognized diploma courses for physicians (Diploma in Radiation Medicine) and technologists (Diploma in Medical Radioisotope Techniques) in 1973. National Board of Examination (Government of India) recognized nuclear medicine as a broad specialty in 1982 and accredited RMC for training for Diplomate of National Board. Doctor of Medicine (MD) started first time in India and Asia at Sanjay Gandhi Postgraduate Institute, Lucknow in 1990. Doctorate of Therapeutic Nuclear Medicine commenced at All India Institute of Medical Sciences Delhi in 2015. There are 18 teaching hospitals currently imparting MD/DNB nuclear medicine residency for physicians with annual intake of 50. Eighteen institutions are offering bachelors and masters programs for nuclear medicine technology with an average annual intake of 110-120 students. Society of Nuclear Medicine, India (SNMI) is the oldest and largest professional body with total life membership of 1425 nuclear medicine professionals. SNMI was established in 1967 and hosted the first Annual Conference at RMC, Mumbai in 1968. Since then, SNMI is organizing its Annual Conferences in various parts of the country with the objective of scientific exchange and popularizing the modality amongst clinicians. Postgraduate Institute of Medical Education Research is hosting the 50 Annual Conference of SNMI (SNMICON-18) as mark of golden jubilee celebration.
PubMed: 30533977
DOI: 10.4103/0972-3919.245053 -
Acta Cardiologica Sinica Mar 2016Radionuclide myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) has been widely used clinically as one of the major functional... (Review)
Review
UNLABELLED
Radionuclide myocardial perfusion imaging (MPI) with single photon emission computed tomography (SPECT) has been widely used clinically as one of the major functional imaging modalities for patients with coronary artery disease (CAD) for decades. Ample evidence has supported the use of MPI as a useful and important tool in the diagnosis, risk stratification and treatment planning for CAD. Although popular in the United States, MPI has become the most frequently used imaging modality among all nuclear medicine tests in Taiwan. However, it should be acknowledged that MPI SPECT does have its limitations. These include false-positive results due to certain artifacts, false-negative due to balanced ischemia, complexity and adverse reaction arising from current pharmacological stressors, time consuming nature of the imaging procedure, no blood flow quantitation and relatively high radiation exposure. The purpose of this article was to review the recent trends in nuclear cardiology, including the utilization of positron emission tomography (PET) for MPI, new stressor, new SPECT camera with higher resolution and higher sensitivity, dynamic SPECT protocol for blood flow quantitation, new software of phase analysis for evaluation of LV dyssynchrony, and measures utilized for reducing radiation exposure of MPI.
KEY WORDS
Coronary artery disease • Myocardial flow reserve • Myocardial perfusion imaging • Phase analysis • PET • SPECT.
PubMed: 27122946
DOI: 10.6515/acs20150803a -
PET Clinics Jul 2018Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras... (Review)
Review
Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras using γ-emitting Tc-sestamibi and breast-specific PET cameras using F-fluorodeoxyglucose. This article focuses on the current role of such approaches in the clinical setting including diagnosis, assessing local extent of disease, monitoring response to therapy, and, for gamma camera imaging, possible supplemental screening in women with dense breasts. Barriers to clinical adoption and technologies and radiotracers under development are also discussed.
Topics: Breast; Breast Neoplasms; Female; Gamma Cameras; Humans; Positron-Emission Tomography; Radionuclide Imaging; Reproducibility of Results
PubMed: 30100076
DOI: 10.1016/j.cpet.2018.02.008 -
The Quarterly Journal of Nuclear... Feb 2010Neuroendocrine tumours (NET) diagnosis has represented a major challenge in the past decades. The introduction of somatostatin receptor scintigraphy in the diagnostic... (Review)
Review
Neuroendocrine tumours (NET) diagnosis has represented a major challenge in the past decades. The introduction of somatostatin receptor scintigraphy in the diagnostic work-up led to a significant improvement of accuracy. However with the advent of positron emission tomography (PET) that presents a higher spatial resolution as compared to the gamma camera and an array of different radiotracers, it is now possible to image NET with an even higher accuracy. In fact, PET imaging of NET is a rapidly evolving field closely connected to the development of novel beta-emitting radiopharmaceuticals. NET can be easily visualized on PET scans using an array of both metabolic and receptor-based tracers. [18F]DOPA and [68Ga]DOTA-peptides (DOTA-TOC, DOTA-NOC, DOTA-TATE) are very promising to image well differentiated NET and were reported to be superior to other imaging modalities (computed tomography [CT], somatostatin receptor scintigraphy). On the contrary, the role of [18F]FDG is limited in well differentiated NET, due to their low glucose metabolism and growth rate, while it still can provide valuable information in less differentiated tumours. On-going studies are investigating the potential role of new imaging agents (bombesin, GLP-1, CCK) that specifically bind to receptors expressed on NET cells.
Topics: Humans; Neuroendocrine Tumors; Positron-Emission Tomography; Radiopharmaceuticals
PubMed: 20168283
DOI: No ID Found -
World Journal of Radiology Jul 2015Colorectal cancer is one of the few malignant tumors in which synchronous or metachronous liver metastases [colorectal liver metastases (CRLMs)] may be treated with... (Review)
Review
Colorectal cancer is one of the few malignant tumors in which synchronous or metachronous liver metastases [colorectal liver metastases (CRLMs)] may be treated with surgery. It has been demonstrated that resection of CRLMs improves the long-term prognosis. On the other hand, patients with un-resectable CRLMs may benefit from chemotherapy alone or in addition to liver-directed therapies. The choice of the most appropriate therapeutic management of CRLMs depends mostly on the diagnostic imaging. Nowadays, multiple non-invasive imaging modalities are available and those have a pivotal role in the workup of patients with CRLMs. Although extensive research has been performed with regards to the diagnostic performance of ultrasonography, computed tomography, positron emission tomography and magnetic resonance for the detection of CRLMs, the optimal imaging strategies for staging and follow up are still to be established. This largely due to the progressive technological and pharmacological advances which are constantly improving the accuracy of each imaging modality. This review describes the non-invasive imaging approaches of CRLMs reporting the technical features, the clinical indications, the advantages and the potential limitations of each modality, as well as including some information on the development of new imaging modalities, the role of new contrast media and the feasibility of using parametric image analysis as diagnostic marker of presence of CRLMs.
PubMed: 26217455
DOI: 10.4329/wjr.v7.i7.157