Browsing by Subject "Radiographic Image Enhancement"

Now showing 1 - 4 of 4
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    Investigation of sliced body volume (SBV) as respiratory surrogate.
    (Journal of applied clinical medical physics, 2013-01-07) Cai, Jing; Chang, Zheng; O'Daniel, Jennifer; Yoo, Sua; Ge, Hong; Kelsey, Christopher; Yin, Fang-Fang
    The purpose of this study was to evaluate the sliced body volume (SBV) as a respiratory surrogate by comparing with the real-time position management (RPM) in phantom and patient cases. Using the SBV surrogate, breathing signals were extracted from unsorted 4D CT images of a motion phantom and 31 cancer patients (17 lung cancers, 14 abdominal cancers) and were compared to those clinically acquired using the RPM system. Correlation coefficient (R), phase difference (D), and absolute phase difference (D(A)) between the SBV-derived breathing signal and the RPM signal were calculated. 4D CT reconstructed based on the SBV surrogate (4D CT(SBV)) were compared to those clinically generated based on RPM (4D CT(RPM)). Image quality of the 4D CT were scored (S(SBV) and S(RPM), respectively) from 1 to 5 (1 is the best) by experienced evaluators. The comparisons were performed for all patients, and for the lung cancer patients and the abdominal cancer patients separately. RPM box position (P), breathing period (T), amplitude (A), period variability (V(T)), amplitude variability (V(A)), and space-dependent phase shift (F) were determined and correlated to S(SBV). The phantom study showed excellent match between the SBV-derived breathing signal and the RPM signal (R = 0.99, D= -3.0%, D(A) = 4.5%). In the patient study, the mean (± standard deviation (SD)) R, D, D(A), T, V(T), A, V(A), and F were 0.92 (± 0.05), -3.3% (± 7.5%), 11.4% (± 4.6%), 3.6 (± 0.8) s, 0.19 (± 0.10), 6.6 (± 2.8) mm, 0.20 (± 0.08), and 0.40 (± 0.18) s, respectively. Significant differences in R and D(A) (p = 0.04 and 0.001, respectively) were found between the lung cancer patients and the abdominal cancer patients. 4D CT(RPM) slightly outperformed 4D CT(SBV): the mean (± SD) S(RPM) and S(SBV) were 2.6 (± 0.6) and 2.9 (± 0.8), respectively, for all patients, 2.5 (± 0.6) and 3.1 (± 0.8), respectively, for the lung cancer patients, and 2.6 (± 0.7) and 2.8 (± 0.9), respectively, for the abdominal cancer patients. The difference between S(RPM) and S(SBV) was insignificant for the abdominal patients (p = 0.59). F correlated moderately with S(SBV) (r = 0.72). The correlation between SBV-derived breathing signal and RPM signal varied between patients and was significantly better in the abdomen than in the thorax. Space-dependent phase shift is a limiting factor of the accuracy of the SBV surrogate.
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    ItemOpen Access
    Micro-CT imaging of breast tumors in rodents using a liposomal, nanoparticle contrast agent.
    (Int J Nanomedicine, 2009) Samei, Ehsan; Saunders, Robert S; Badea, Cristian T; Ghaghada, Ketan B; Hedlund, Laurence W; Qi, Yi; Yuan, Hong; Bentley, Rex C; Mukundan, Srinivasan
    A long circulating liposomal, nanoscale blood pool agent encapsulating traditional iodinated contrast agent (65 mg I/mL) was used for micro-computed tomography (CT) imaging of rats implanted with R3230AC mammary carcinoma. Three-dimensional vascular architecture of tumors was imaged at 100-micron isotropic resolution. The image data showed good qualitative correlation with pathologic findings. The approach holds promise for studying tumor angiogenesis and for evaluating anti-angiogenesis therapies.
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    Plate-specific gain map correction for the improvement of detective quantum efficiency in computed radiography.
    (2010) Schnell, Erich A.
    The purpose of this work is to improve the NPS, and thus DQE, of CR images by correcting for pixel-to-pixel gain variations specific to each plate. Ten high-exposure open field images were taken with an RQA5 spectrum, with a sixth generation CR plate suspended in air without a cassette. Image values were converted to exposure, the plates registered using fiducial dots on the plate, the ten images averaged, and then high-pass filtered to remove low frequency contributions from field inhomogeneity. A gain-map was then produced by converting all pixel values in the average into fractions with mean of one. The resultant gain-map of the plate was used to normalize subsequent single images to correct for pixel-to-pixel gain fluctuation. The normalized NPS (NNPS) for all images was calculated both with and without the gain-map correction. The NNPS with correction showed improvement over the non-corrected case over the range of frequencies from 0.15 –2.5 mm-1. At high exposure (40 mR), NNPS was 50-90% better with gain-map correction than without. A small further improvement in NNPS was seen from careful registering of the gain-map with subsequent images using small fiducial dots, because of slight misregistration during scanning. CR devices have not traditionally employed gain-map corrections common with DR detectors because of the multiplicity of plates used with each reader. This study demonstrates that a simple gain-map can be used to correct for the fixed-pattern noise and thus improve the DQE of CR imaging. Such a method could easily be implemented by manufacturers because each plate has a unique bar code and the gain-map could be stored for retrieval after plate reading. These experiments indicated that an improvement in NPS (and hence, DQE) is possible, depending on exposure level,over all frequencies with this technique.
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    Spectrotemporal CT data acquisition and reconstruction at low dose.
    (Med Phys, 2015-11) Clark, Darin P; Lee, Chang-Lung; Kirsch, David G; Badea, Cristian T
    PURPOSE: X-ray computed tomography (CT) is widely used, both clinically and preclinically, for fast, high-resolution anatomic imaging; however, compelling opportunities exist to expand its use in functional imaging applications. For instance, spectral information combined with nanoparticle contrast agents enables quantification of tissue perfusion levels, while temporal information details cardiac and respiratory dynamics. The authors propose and demonstrate a projection acquisition and reconstruction strategy for 5D CT (3D+dual energy+time) which recovers spectral and temporal information without substantially increasing radiation dose or sampling time relative to anatomic imaging protocols. METHODS: The authors approach the 5D reconstruction problem within the framework of low-rank and sparse matrix decomposition. Unlike previous work on rank-sparsity constrained CT reconstruction, the authors establish an explicit rank-sparse signal model to describe the spectral and temporal dimensions. The spectral dimension is represented as a well-sampled time and energy averaged image plus regularly undersampled principal components describing the spectral contrast. The temporal dimension is represented as the same time and energy averaged reconstruction plus contiguous, spatially sparse, and irregularly sampled temporal contrast images. Using a nonlinear, image domain filtration approach, the authors refer to as rank-sparse kernel regression, the authors transfer image structure from the well-sampled time and energy averaged reconstruction to the spectral and temporal contrast images. This regularization strategy strictly constrains the reconstruction problem while approximately separating the temporal and spectral dimensions. Separability results in a highly compressed representation for the 5D data in which projections are shared between the temporal and spectral reconstruction subproblems, enabling substantial undersampling. The authors solved the 5D reconstruction problem using the split Bregman method and GPU-based implementations of backprojection, reprojection, and kernel regression. Using a preclinical mouse model, the authors apply the proposed algorithm to study myocardial injury following radiation treatment of breast cancer. RESULTS: Quantitative 5D simulations are performed using the MOBY mouse phantom. Twenty data sets (ten cardiac phases, two energies) are reconstructed with 88 μm, isotropic voxels from 450 total projections acquired over a single 360° rotation. In vivo 5D myocardial injury data sets acquired in two mice injected with gold and iodine nanoparticles are also reconstructed with 20 data sets per mouse using the same acquisition parameters (dose: ∼60 mGy). For both the simulations and the in vivo data, the reconstruction quality is sufficient to perform material decomposition into gold and iodine maps to localize the extent of myocardial injury (gold accumulation) and to measure cardiac functional metrics (vascular iodine). Their 5D CT imaging protocol represents a 95% reduction in radiation dose per cardiac phase and energy and a 40-fold decrease in projection sampling time relative to their standard imaging protocol. CONCLUSIONS: Their 5D CT data acquisition and reconstruction protocol efficiently exploits the rank-sparse nature of spectral and temporal CT data to provide high-fidelity reconstruction results without increased radiation dose or sampling time.