Browsing by Author "Liang, Yun"

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    Evaluation of a Hybrid Iterative Reconstruction technique "iDose" for CT Dose Reduction and Image Quality
    (Office of the Vice Chancellor for Research, 2014-04-11) Liang, Yun
    Purpose: To investigate the use of a commercial designed hybrid iterative reconstruction technique iDose (by Philips Medical Systems) for CT radiation dose reduction and its effect on image quality. Methods: A catphan®504 phantom was scanned using a 64-slice CT (Ingenuity, Philips Medical Systems) with two different tube voltages (100 kVp, and 120 kVp) at three different doses, a reference dose (CTDIvol) of 42 mGy and two reduced doses of about 50% and 75% of the reference. Images were reconstructed with standard filtered-back-projection (FBP) and with iDose algorithms. Six different iDose levels were employed. Quantitative evaluation of spatial resolution, image noise, noise power spectrum (NPS), and low-contrast detectability were carried out. Results: For any given dose level, there was a static noise reduction with increased iDose level over the FBP. To match the “standard” noise resulted from the FBP at the “reference dose”, a minimum iDose level of 4 and 6 was required for 50% and 75% dose reduction respectively. NPS showed moderate shift towards the lower frequency as the iDose level increased. The NPS shift was consistent with the observed subtle change of noise texture. This shift also correlated with the change in low-contrast detectability among images with the same noise level, the higher the iDose level that was used in image reconstruction, the lower the low-contrast detectability. Conclusions: The iDose algorithm clearly demonstrates effectiveness in noise suppression over the FBP. The low-contrast detectability depends on noise but also on NPS, which is shifted by iDose algorithm. At very low-dose levels, greater iDose levels would be needed to reduce the image noise but may not improve the low-contrast detectability. This findings indicate that for any given specific clinical task, the lowest dose limit achievable is determined by an “optimal” iDose level ascertaining the noise reduction as well as maintaining desired low-contrast detectability.
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    Evaluation of a pig femoral head osteonecrosis model
    (BMC, 2010-03-06) Zhang, Ping; Liang, Yun; Kim, Harry; Yokota, Hiroki; Biomedical Engineering, School of Engineering and Technology
    Background A major cause of osteonecrosis of the femoral head is interruption of a blood supply to the proximal femur. In order to evaluate blood circulation and pathogenetic alterations, a pig femoral head osteonecrosis model was examined to address whether ligature of the femoral neck (vasculature deprivation) induces a reduction of blood circulation in the femoral head, and whether transphyseal vessels exist for communications between the epiphysis and the metaphysis. We also tested the hypothesis that the vessels surrounding the femoral neck and the ligamentum teres represent the primary source of blood flow to the femoral head. Methods Avascular osteonecrosis of the femoral head was induced in Yorkshire pigs by transecting the ligamentum teres and placing two ligatures around the femoral neck. After heparinized saline infusion and microfil perfusion via the abdominal aorta, blood circulation in the femoral head was evaluated by optical and CT imaging. Results An angiogram of the microfil casted sample allowed identification of the major blood vessels to the proximal femur including the iliac, common femoral, superficial femoral, deep femoral and circumflex arteries. Optical imaging in the femoral neck showed that a microfil stained vessel network was visible in control sections but less noticeable in necrotic sections. CT images showed a lack of microfil staining in the epiphysis. Furthermore, no transphyseal vessels were observed to link the epiphysis to the metaphysis. Conclusion Optical and CT imaging analyses revealed that in this present pig model the ligatures around the femoral neck were the primary cause of induction of avascular osteonecrosis. Since the vessels surrounding the femoral neck are comprised of the branches of the medial and the lateral femoral circumflex vessels, together with the extracapsular arterial ring and the lateral epiphyseal arteries, augmentation of blood circulation in those arteries will improve pathogenetic alterations in the necrotic femoral head. Our pig model can be used for further femoral head osteonecrosis studies.
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    Performance evaluation of two interventional fluoroscope suites for cardiovascular imaging
    (Wiley, 2022) Anthony, Gregory; Liang, Yun; Zhao, Xuandong; Radiology and Imaging Sciences, School of Medicine
    Interventional cardiology involves catheter-based treatment of heart disease, generally through fluoroscopically guided interventional procedures. Patients can be subject to considerable radiation dose due to prolonged fluoroscopy time and radiographic exposure, and therefore efforts to minimize patient dose should always be undertaken. Developing standardized, effective quality control programs for these systems is a difficult task owing to cross-vendor differences and automated control of imaging protocols. Furthermore, analyses of radiation dose should be performed in the context of its associated effects on image quality. The aim of the study is to investigate radiation dose and image quality in two fluoroscopic systems used for interventional cardiology procedures. Image quality was assessed in terms of spatial resolution and modulation transfer function, signal-to-noise and contrast-to-noise ratios, and spatial-temporal resolution of fluoroscopy and cineradiography images with phantoms simulating various patient thicknesses under routine cardiology protocols. The entrance air kerma (or air kerma rate) was measured and used to estimate entrance surface dose (or dose rate) in the phantoms.
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    Radiographic imaging, densitometry and disease severity in Autosomal dominant osteopetrosis type 2
    (Springer, 2021) Ladd, Lauren M.; Imel, Erik A.; Niziolek, Paul J.; Liu, Ziyue; Warden, Stuart J.; Liang, Yun; Econs, Michael J.; Radiology and Imaging Sciences, School of Medicine
    Objective: To characterize relationships between quantitative computed tomography bone mineral density measurements and other qualitative and quantitative imaging measures, as well as clinical metrics, in patients with autosomal dominant osteopetrosis type 2 (ADO2). Materials and methods: Clinical and radiologic parameters of 9 adults and 3 children with autosomal dominant osteopetrosis type 2 were assessed including lumbar spine quantitative computed tomography (QCT), radiographic skeletal survey (skull base thickening; Erlenmeyer flask deformity; endobone pattern; and spine density pattern (endplate sclerosis, "anvil" appearance, or diffuse sclerosis)), dual-energy x-ray absorptiometry (DXA), tibial peripheral quantitative computed tomography (pQCT) volumetric bone mineral density (vBMD), bone turnover markers, and bone marrow failure or visual impairment. Results: The skeletal parameter most divergent from normal was lumbar spine QCT Z-score (+ 3.6 to + 38.7). Lumbar QCT Z-score correlated positively with pQCT tibial diaphysis vBMD (Pearson correlation r = 0.73, p = 0.02) and pQCT tibial metaphysis vBMD (r = 0.87, p < 0.01). A trend towards positive lumbar QCT Z-score correlation with serum P1NP/CTX ratio (r = 0.54, p = 0.10) and lumbar DXA Z-score (r = 0.55, p = 0.10) were observed. Bone marrow failure and vision impairment occurred in those with most severe quantitative and qualitative measures, while those with less severe radiographic features had the lowest QCT Z-scores. Conclusion: Lumbar spine QCT provided the most extreme skeletal assessment in ADO2, which correlated positively with other radiologic and clinical markers of disease severity. Given the quantification of trabecular bone and greater variation from normal with wider range of values, lumbar QCT Z-scores may be useful to determine or detect impact of future treatments.