Browsing by Subject "Radionuclide Imaging"

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    ItemOpen Access
    Automated quality control in nuclear medicine using the structured noise index.
    (Journal of applied clinical medical physics, 2020-04) Nelson, Jeffrey S; Samei, Ehsan

    Purpose

    Daily flood-field uniformity evaluation serves as the central element of nuclear medicine (NM) quality control (QC) programs. Uniformity images are traditionally analyzed using pixel value-based metrics, that is, integral uniformity (IU), which often fail to capture subtle structure and patterns caused by changes in gamma camera performance, requiring visual inspections which are subjective and time demanding. The goal of this project was to implement an advanced QC metrology for NM to effectively identify nonuniformity issues, and report issues in a timely manner for efficient correction prior to clinical use. The project involved the implementation of the program over a 2-year period at a multisite major medical institution.

    Methods

    Using a previously developed quantitative uniformity analysis metric, the structured noise index (SNI) [Nelson et al. (2014), \textit{J Nucl Med.}, \textbf{55}:169-174], an automated QC process was developed to analyze, archive, and report on daily NM QC uniformity images. Clinical implementation of the newly developed program ran in parallel with the manufacturer's reported IU-based QC program. The effectiveness of the SNI program was evaluated over a 21-month period using sensitivity and coefficient of variation statistics.

    Results

    A total of 7365 uniformity QC images were analyzed. Lower level SNI alerts were generated in 12.5% of images and upper level alerts in 1.7%. Intervention due to image quality issues occurred on 26 instances; the SNI metric identified 24, while the IU metric identified eight. The SNI metric reported five upper level alerts where no clinical engineering intervention was deemed necessary.

    Conclusion

    An SNI-based QC program provides a robust quantification of the performance of gamma camera uniformity. It operates seamlessly across a fleet of multiple camera models and, additionally, provides effective workflow among the clinical staff. The reliability of this process could eliminate the need for visual inspection of each image, saving valuable time, while enabling quantitative analysis of inter- and intrasystem performance.
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    ItemOpen Access
    Dual-energy micro-CT functional imaging of primary lung cancer in mice using gold and iodine nanoparticle contrast agents: a validation study.
    (PLoS One, 2014) Ashton, Jeffrey R; Clark, Darin P; Moding, Everett J; Ghaghada, Ketan; Kirsch, David G; West, Jennifer L; Badea, Cristian T
    PURPOSE: To provide additional functional information for tumor characterization, we investigated the use of dual-energy computed tomography for imaging murine lung tumors. Tumor blood volume and vascular permeability were quantified using gold and iodine nanoparticles. This approach was compared with a single contrast agent/single-energy CT method. Ex vivo validation studies were performed to demonstrate the accuracy of in vivo contrast agent quantification by CT. METHODS: Primary lung tumors were generated in LSL-Kras(G12D); p53(FL/FL) mice. Gold nanoparticles were injected, followed by iodine nanoparticles two days later. The gold accumulated in tumors, while the iodine provided intravascular contrast. Three dual-energy CT scans were performed-two for the single contrast agent method and one for the dual contrast agent method. Gold and iodine concentrations in each scan were calculated using a dual-energy decomposition. For each method, the tumor fractional blood volume was calculated based on iodine concentration, and tumor vascular permeability was estimated based on accumulated gold concentration. For validation, the CT-derived measurements were compared with histology and inductively-coupled plasma optical emission spectroscopy measurements of gold concentrations in tissues. RESULTS: Dual-energy CT enabled in vivo separation of gold and iodine contrast agents and showed uptake of gold nanoparticles in the spleen, liver, and tumors. The tumor fractional blood volume measurements determined from the two imaging methods were in agreement, and a high correlation (R(2) = 0.81) was found between measured fractional blood volume and histology-derived microvascular density. Vascular permeability measurements obtained from the two imaging methods agreed well with ex vivo measurements. CONCLUSIONS: Dual-energy CT using two types of nanoparticles is equivalent to the single nanoparticle method, but allows for measurement of fractional blood volume and permeability with a single scan. As confirmed by ex vivo methods, CT-derived nanoparticle concentrations are accurate. This method could play an important role in lung tumor characterization by CT.
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    ItemOpen Access
    The imaging viewpoint: how imaging affects determination of progression-free survival.
    (Clin Cancer Res, 2013-05-15) Sullivan, Daniel Carl; Schwartz, Lawrence H; Zhao, Binsheng
    Tumor measurements on computed tomgoraphic or MRI scans and/or the appearance of new lesions on any of a variety of imaging studies including positron emission tomographic scans are key determinants for assessing progression-free survival as an endpoint in many clinical trials of therapies for solid tumors. Test-retest tumor measurement reproducibility may vary considerably across serial scans on the same patient unless rigorous attention is paid to standardization of image acquisition parameters and unless measurements are made by trained, experienced observers using validated objective methods. Target lesion selection also must be done with care to choose lesions that are or will be reproducibly measurable. Likewise, new lesions will be missed or misinterpreted on follow-up imaging studies unless those imaging studies are obtained using techniques suitable for detecting early, small lesions. Reader variability is clearly a major component of the problem. The increasing availability of semiautomatic image processing algorithms will help ameliorate that issue. In addition, an array of internationally accepted guidelines, standards, and accreditation programs now exist to help address these problems.