| 1. |
- Bergqvist, Lennart, et al.
(författare)
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Particle sizing and biokinetics of interstitiallymphoscintigraphic agents
- 1983
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Ingår i: Seminars in Nuclear Medicine. - 0001-2998. ; 13:1, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- The biokinetics of inert lymphoscintigraphic agentsstrongly depends on their particle size. Different techniques for characterization of colloids are discussed. Experiments have been performed on eight different colloids. The particle size has been investigated with scanning electron microscopy. Activity distributions have been obtained with ultrafiltration and gel-column scanning technique. The colloids suggested for lymphoscintigraphy were found to have a median size of about 40-50 nm except one minimicro-aggregated human serum albumin colloid which has a median particle size around 10 nm. The biokinetics were studied with a scintillation camera in rabbits after a subcutaneous injection. Timeactivity curves were generated. After 5 hr the rabbits were dissected and the activity content in different tissues measured. A compartment model for the biokinetics was designed and rate constants evaluated. The total and specific activity uptake in parasternal lymph nodes was highest for the small-particle colloids. The compartment model showed a good fitting to the experimental data.
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| 2. |
- Bajc, Marika, et al.
(författare)
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Methodology for ventilation/perfusion SPECT.
- 2010
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Ingår i: Seminars in Nuclear Medicine. - : Elsevier BV. - 0001-2998. ; 40:6, s. 415-425
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Tidskriftsartikel (refereegranskat)abstract
- Ventilation/perfusion single-photon emission computed tomography (V/Q SPECT) is the scintigraphic technique of choice for the diagnosis of pulmonary embolism and many other disorders that affect lung function. Data from recent ventilation studies show that the theoretic advantages of Technegas over radiolabeled liquid aerosols are not restricted to the presence of obstructive lung disease. Radiolabeled macroaggregated human albumin is the imaging agent of choice for perfusion scintigraphy. An optimal combination of nuclide activities and acquisition times for ventilation and perfusion, collimators, and imaging matrix yields an adequate V/Q SPECT study in approximately 20 minutes of imaging time. The recommended protocol based on the patient remaining in an unchanged position during the initial ventilation study and the perfusion study allows presentation of matching ventilation and perfusion slices in all projections as well as in rotating volume images based upon maximum intensity projections. Probabilistic interpretation of V/Q SPECT should be replaced by a holistic interpretation strategy on the basis of all relevant information about the patient and all ventilation/perfusion patterns. PE is diagnosed when there is more than one subsegment showing a V/Q mismatch representing an anatomic lung unit. Apart from pulmonary embolism, other pathologies should be identified and reported, for example, obstructive disease, heart failure, and pneumonia. Pitfalls exist both with respect to imaging technique and scan interpretation.
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| 3. |
- Evans Axelsson, Susan, et al.
(författare)
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Radioimmunotherapy for Prostate Cancer-Current Status and Future Possibilities.
- 2016
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Ingår i: Seminars in Nuclear Medicine. - : Elsevier BV. - 0001-2998. ; 46:2, s. 165-179
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Forskningsöversikt (refereegranskat)abstract
- Prostate cancer (PCa) is one of the most common cancers in men and is the second leading cause of cancer-related deaths in the USA. In the United States, it is the second most frequently diagnosed cancer after skin cancer, and in Europe it is number one. According to the American Cancer Society, approximately 221,000 men in the United States would be diagnosed with PCa during 2015, and approximately 28,000 would die of the disease. According to the International Agency for Research on Cancer, approximately 345,000 men were diagnosed with PCa in Europe during 2012, and despite more emphasis placed on early detection through routine screening, 72,000 men died of the disease. Hence, the need for improved therapy modalities is of utmost importance. And targeted therapies based on radiolabeled specific antibodies or peptides are a very interesting and promising alternative to increase the therapeutic efficacy and overall chance of survival of these patients. There are currently several preclinical and some clinical studies that have been conducted, or are ongoing, to investigate the therapeutic efficacy and toxicity of radioimmunotherapy (RIT) against PCa. One thing that is lacking in a lot of these published studies is the dosimetry data, which are needed to compare results between the studies and the study locations. Given the complicated tumor microenvironment and overall complexity of RIT to PCa, old and new targets and targeting strategies like combination RIT and pretargeting RIT are being improved and assessed along with various therapeutic radionuclides candidates. Given alone or in combination with other therapies, these new and improved strategies and RIT tools further enhance the clinical response to RIT drugs in PCa, making RIT for PCa an increasingly practical clinical tool.
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| 4. |
- Frey, Eric C., et al.
(författare)
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Accuracy and Precision of Radioactivity Quantification in Nuclear Medicine Images
- 2012
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Ingår i: Seminars in Nuclear Medicine. - : Elsevier BV. - 0001-2998. ; 42:3, s. 208-218
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Forskningsöversikt (refereegranskat)abstract
- The ability to reliably quantify activity in nuclear medicine has a number of increasingly important applications. Dosimetry for targeted therapy treatment planning or for approval of new imaging agents requires accurate estimation of the activity in organs, tumors, or voxels at several imaging time points. Another important application is the use of quantitative metrics derived from images, such as the standard uptake value commonly used in positron emission tomography (PET), to diagnose and follow treatment of tumors. These measures require quantification of organ or tumor activities in nuclear medicine images. However, there are a number of physical, patient, and technical factors that limit the quantitative reliability of nuclear medicine images. There have been a large number of improvements in instrumentation, including the development of hybrid single-photon emission computed tomography/computed tomography and PET/computed tomography systems, and reconstruction methods, including the use of statistical iterative reconstruction methods, which have substantially improved the ability to obtain reliable quantitative information from planar, single-photon emission computed tomography, and PET images. Semin Nucl Med 42:208-218 (C) 2012 Elsevier Inc. All rights reserved.
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| 5. |
- Harms, Hendrik J, et al.
(författare)
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First-Pass Techniques Applied to Standard Dynamic Cardiac PET : A reappraisal of Old Invasive Techniques to Assess Cardiac Function
- 2020
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Ingår i: Seminars in nuclear medicine. - : Elsevier BV. - 0001-2998 .- 1558-4623. ; 50:4, s. 349-356
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Forskningsöversikt (refereegranskat)abstract
- Cardiac PET is increasingly performed with dynamic imaging to measure tracer pharmacokinetics in the myocardium. If the early time frames of the PET protocol are sufficiently short and the total amount of injected radioactivity is correctly measured the indicator dilution principle can be applied to PET with most tracers in clinical use, similar to invasive and other noninvasive techniques. The first-pass of the tracer through the heart and lungs can be used to quantify some highly important aspects of cardiovascular function, such as forward cardiac output, transit times, and partial volumes in the central compartments. Additionally, ECG-gated first pass images provide direct access to cardiac volumes and ejection fractions, even for tracers with poor trapping in the myocardial wall, for instance 15O-water. This review summarizes the basic approaches of the indicator dilution principle in clinical use with invasive techniques, and how these techniques can be integrated into a cardiac PET scan.
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| 6. |
- Johnson, Geoffrey B., et al.
(författare)
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PET Imaging of Tumor Perfusion : A Potential Cancer Biomarker?
- 2020
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Ingår i: Seminars in nuclear medicine. - : Elsevier BV. - 0001-2998 .- 1558-4623. ; 50:6, s. 549-561
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Forskningsöversikt (refereegranskat)abstract
- Perfusion, as measured by imaging, is considered a standard of care biomarker for the evaluation of many tumors. Measurements of tumor perfusion may be used in a number of ways, including improving the visual detection of lesions, differentiating malignant from benign findings, assessing aggressiveness of tumors, identifying ischemia and by extension hypoxia within tumors, and assessing treatment response. While most clinical perfusion imaging is currently performed with CT or MR, a number of methods for PET imaging of tumor perfusion have been described. The inert PET radiotracer 15O-water PET represents the recognized gold standard for absolute quantification of tissue perfusion in both normal tissue and a variety of pathological conditions including cancer. Other cancer PET perfusion imaging strategies include the use of radiotracers with high first-pass uptake, analogous to those used in cardiac perfusion PET. This strategy produces more visually pleasing high-contrast images that provide relative rather than absolute perfusion quantification. Lastly, multiple timepoint imaging of PET tracers such as 18F-FDG, are not specifically optimized for perfusion, but have advantages related to availability, convenience, and reimbursement. Multiple obstacles have thus far blocked the routine use of PET imaging for tumor perfusion, including tracer production and distribution, image processing, patient body coverage, clinical validation, regulatory approval and reimbursement, and finally feasible clinical workflows. Fortunately, these obstacles are being overcome, especially within larger imaging centers, opening the door for PET imaging of tumor perfusion to become standard clinical practice. In the foreseeable future, it is possible that whole-body PET perfusion imaging with 15O-water will be able to be performed in a single imaging session concurrent with standard PET imaging techniques such as 18F-FDG-PET. This approach could establish an efficient clinical workflow. The resultant ability to measure absolute tumor blood flow in combination with glycolysis will provide important complementary information to inform prognosis and clinical decisions.
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| 7. |
- Lindgren Belal, Sarah, et al.
(författare)
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Applications of Artificial Intelligence in PSMA PET/CT for Prostate Cancer Imaging
- 2024
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Ingår i: Seminars in Nuclear Medicine. - 1558-4623 .- 0001-2998. ; 54:1, s. 141-149
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Forskningsöversikt (refereegranskat)abstract
- Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) has emerged as an important imaging technique for prostate cancer. The use of PSMA PET/CT is rapidly increasing, while the number of nuclear medicine physicians and radiologists to interpret these scans is limited. Additionally, there is variability in interpretation among readers. Artificial intelligence techniques, including traditional machine learning and deep learning algorithms, are being used to address these challenges and provide additional insights from the images. The aim of this scoping review was to summarize the available research on the development and applications of AI in PSMA PET/CT for prostate cancer imaging. A systematic literature search was performed in PubMed, Embase and Cinahl according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 26 publications were included in the synthesis. The included studies focus on different aspects of artificial intelligence in PSMA PET/CT, including detection of primary tumor, local recurrence and metastatic lesions, lesion classification, tumor quantification and prediction/prognostication. Several studies show similar performances of artificial intelligence algorithms compared to human interpretation. Few artificial intelligence tools are approved for use in clinical practice. Major limitations include the lack of external validation and prospective design. Demonstrating the clinical impact and utility of artificial intelligence tools is crucial for their adoption in healthcare settings. To take the next step towards a clinically valuable artificial intelligence tool that provides quantitative data, independent validation studies are needed across institutions and equipment to ensure robustness.
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| 8. |
- Ljungberg, Michael
(författare)
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Absolute Quantitation of SPECT Studies
- 2018
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Ingår i: Seminars in Nuclear Medicine. - : Elsevier BV. - 0001-2998. ; 48:4, s. 348-358
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Tidskriftsartikel (refereegranskat)abstract
- Methods for absolute quantitation of SPECT images provide an estimate of the activity uptakes in various organs and tissues in units of (M)Bq or (m)Ci. However, because tomographic SPECT images generally are hampered by several physical and camera-specific effects, accurate and precise compensation methods are required. The most important effects are (1) photon attenuation in the patient resulting in a reduction of expected acquired count; (2) the contribution of events from photons, scattered in the phantom and the collimator but accepted by the energy window because of a poor energy resolution of the NaI(Tl) crystal; and (3) the effect of the collimator response function that degrades the image quality because of the relatively poor spatial resolution. In addition, camera-specific effects, such as dead time and pulse pile-up, are discussed. These effects can reduce the accuracy and precision in the activity estimate. In addition to these compensation methods, a careful and consistent calibration is needed to translate count in the image that corresponds to a location of the patent to activity (or activity concentration). This review summarizes the required compensation methods and the means by which they are implemented in an iterative reconstruction approach and discusses some applications and areas where quantitative SPECT might be important for the future.
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| 10. |
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