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      Importance of Defect Detectability in Positron Emission Tomography Imaging of Abdominal Lesions

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          Abstract

          Objective(s):

          This study was designed to assess defect detectability in positron emission tomography (PET) imaging of abdominal lesions.

          Methods:

          A National Electrical Manufactures Association International Electrotechnical Commission phantom was used. The simulated abdominal lesion was scanned for 10 min using dynamic list-mode acquisition method. Images, acquired with scan duration of 1-10 min, were reconstructed using VUE point HD and a 4.7 mm full-width at half-maximum (FWHM) Gaussian filter. Iteration-subset combinations of 2-16 and 2-32 were used. Visual and physical analyses were performed using the acquired images. To sequentially evaluate defect detectability in clinical settings, we examined two middle-aged male subjects. One had a liver cyst (approximately 10 mm in diameter) and the other suffered from pancreatic cancer with an inner defect region (approximately 9 mm in diameter).

          Results:

          In the phantom study, at least 6 and 3 min acquisition durations were required to visualize 10 and 13 mm defect spheres, respectively. On the other hand, spheres with diameters ≥17 mm could be detected even if the acquisition duration was only 1 min. The visual scores were significantly correlated with background (BG) variability. In clinical settings, the liver cyst could be slightly visualized with an acquisition duration of 6 min, although image quality was suboptimal. For pancreatic cancer, the acquisition duration of 3 min was insufficient to clearly describe the defect region.

          Conclusion:

          The improvement of BG variability is the most important factor for enhancing lesion detection. Our clinical scan duration (3 min/bed) may not be suitable for the detection of small lesions or accurate tumor delineation since an acquisition duration of at least 6 min is required to visualize 10 mm lesions, regardless of reconstruction parameters. Improvements in defect detectability are important for radiation treatment planning and accurate PET-based diagnosis.

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          Most cited references 24

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          Solid splenic masses: evaluation with 18F-FDG PET/CT.

          Our objective was to assess the role of (18)F-FDG PET/CT in the evaluation of solid splenic masses in patients with a known malignancy and in incidentally found lesions in patients without known malignancy. Two groups of patients were assessed: (a) 68 patients with known malignancy and a focal lesion on PET or a solid mass on CT portions of the PET/CT study; and (b) 20 patients with solid splenic masses on conventional imaging without known malignancy. The standard of reference was histology (n = 16) or imaging and clinical follow-up (n = 72). The lesion size, the presence of a single versus multiple splenic lesions, and the intensity of (18)F-FDG uptake expressed as a standardized uptake value (SUV) were recorded. The ratio of the SUV in the splenic lesion to the background normal splenic uptake was also calculated. These parameters were compared between benign and malignant lesions within each of the 2 groups of patients and between the 2 groups. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of (18)F-FDG PET/CT in differentiating benign from malignant solid splenic lesions in patients with and without malignant disease were 100%, 100%, 100%, and 100% versus 100%, 83%, 80%, and 100%, respectively. In patients with known malignant disease, an SUV threshold of 2.3 correctly differentiated benign from malignant lesions with the sensitivity, specificity, PPV, and NPV of 100%, 100%, 100%, and 100%, respectively. In patients without known malignant disease, false-positive results were due to granulomatous diseases (n = 2). (18)F-FDG PET can reliably discriminate between benign and malignant solid splenic masses in patients with known (18)F-FDG-avid malignancy. It also appears to have a high NPV in patients with solid splenic masses, without known malignant disease. (18)F-FDG-avid splenic masses in patients without a known malignancy should be further evaluated as, in our series, 80% of them were malignant.
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            Japanese guideline for the oncology FDG-PET/CT data acquisition protocol: synopsis of Version 2.0

            This synopsis outlines the Japanese guideline Version 2.0 for the data acquisition protocol of oncology FDG-PET/CT scans that was created by a joint task force of the Japanese Society of Nuclear Medicine Technology, the Japanese Society of Nuclear Medicine and the Japanese Council of PET Imaging, and was published in Kakuigaku-Gijutsu 2013; 33:377–420 in Japanese. The guideline aims at standardizing the PET image quality among PET centers and different PET camera models by providing criteria for the IEC body phantom image quality as well as for the patient PET image quality based on the noise equivalent count (NEC), NEC density and liver signal-to-noise ratio, so that the appropriate scanning parameters can be determined for each PET camera. This Version 2.0 covers issues that were not focused on in Version 1.0, including the accuracy of the standardized uptake value (SUV), effect of body size together with adjustment of scanning duration, and time-of-flight (TOF) reconstruction technique. Version 2.0 also presents data acquired with new PET camera models that were not tested in Version 1.0. Reference values for physical indicators of phantom image quality have been updated as well.
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              Imaging of adrenal tumors using FDG PET: comparison of benign and malignant lesions.

               B Alfano,  S Maurea,  M Panico (1999)
              The aim of this study was to differentiate benign from malignant adrenal tumors using positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in patients with unilateral adrenal masses originally detected by CT or MR imaging. PET imaging with FDG can metabolically characterize adrenal masses. Abnormally increased FDG uptake in adrenal malignancies allows one to differentiate these abnormalities from benign lesions. Whole-body PET can also reveal extraadrenal tumor sites in patients with malignant tumors, using a single imaging technique for accurate disease staging.
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                Author and article information

                Journal
                Asia Ocean J Nucl Med Biol
                Asia Ocean J Nucl Med Biol
                AOJNMB
                Asia Oceania Journal of Nuclear Medicine and Biology
                Asia Oceania Journal of Nuclear Medicine & Biology (Iran )
                2322-5718
                2322-5726
                Summer 2015
                : 3
                : 2
                : 83-90
                Affiliations
                [1 ]Division of Radiology, Public Central Hospital of Matto Ishikawa, Hakusan, Japan
                [2 ]Department of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
                [3 ]PET Imaging Center, Public Central Hospital of Matto Ishikawa, Hakusan, Japan
                [4 ]Department of Nuclear Medicine, Kanazawa University Hospital, Kanazawa, Japan
                Author notes
                * Corresponding author: Masahisa Onoguchi, Department of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan. Tel: +81-76-265-2526; Email: onoguchi@ 123456staff.kanazawa-u.ac.jp
                Article
                AOJNMB-3-83
                4937645
                27408887
                Copyright: © mums.ac.ir

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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