Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifa...Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifacts. First, the projection of the even and odd lines along phase-encoding direction in hybrid-space was used to estimate the phase difference between odd and even echoes. Secondly, we fit the phase difference and used it to correct the phase of even or odd echoes. Finally, the corrected image was obtained by performing the inverse Fourier transform along phase-encoding direction in hybrid-space. The experimental results show that linear and nonlinear differences can be corrected and the intensity of ghost artifacts is significantly reduced. The effectiveness of the proposed method is demonstrated in ghost artifact removal.展开更多
Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases. Multi-modality imaging approach is usually the more useful in diagnosis colorectal liver m...Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases. Multi-modality imaging approach is usually the more useful in diagnosis colorectal liver metastases. It is well established that hepatic resection improves the long-term prognosis of many patients with liver metastases. However, incomplete resection does not prolong survival, so knowledge of the exact extent of intra-hepatic disease is crucially important in determining patient management and outcome. The diagnosis of liver metastases relies first and totally on imaging to decide which patients may be surgical candidates. This review will discuss the imaging options and their appropriate indications. Imaging and evaluating of colorectal liver metastases （CRLM） have been performed with contrast-enhanced ultrasound, multidetector computed tomography, magnetic resonance imaging （MRI） with extra-cellular contrast media and liver-specific contrast media MRI, and positron emission tomography/computed tomography. This review展开更多
OBJECTIVES: To investigate the findings of magnetic resonance (MR) imaging and histopathology in early postoperative normal brain, and to define the correlation between MR images and histopathology. METHODS: Thirty-si...OBJECTIVES: To investigate the findings of magnetic resonance (MR) imaging and histopathology in early postoperative normal brain, and to define the correlation between MR images and histopathology. METHODS: Thirty-six New Zealand rabbits weighing 2.0 to 3.0 kg were divided into 10 groups according to different postoperative days: 1 to 10 days. A partial resection of the parietooccipital region was performed under usual aseptic conditions after the animals were anesthetized intravenously with 3% pentobarbital (30 mg/kg). MR imaging procedures consisted of pre- and postcontrast scanning and were carried out on postoperative days 1 to 10. Brain tissue samples were prepared for examination immediately after MR scanning. Histopathological examination was done under light both and electron microscopes. The findings of MR imaging were compared with histopathologic findings. RESULTS: Surgical margin contrast enhancement on MR images could be seen 24 hours after surgery. The degree of contrast enhancement increased gradually up to 5 days postoperation, and no remarkable changes were present from days 5 to 10. Disruption of the blood brain barrier (BBB) was the main cause of contrast enhancement during the first 3 postoperative days. After that period, the mechanism responsible for contrast enhancement was the formation of neovascularity and a broken BBB. An increase in the amount of neovascularity played a predominant role in contrast enhancement in normal postoperative brain tissue. CONCLUSIONS: The features of enhanced MR images present at the surgical margin followed a typical time course during the early postoperative period. The role of neovascularity and BBB disruption in the formation of contrast enhancement at the surgical margin varies with time. Knowledge of the features of contrast enhancement in postoperative MR images of normal brain can help in differentiating benign changes from residual malignant glioma.展开更多
文摘Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifacts. First, the projection of the even and odd lines along phase-encoding direction in hybrid-space was used to estimate the phase difference between odd and even echoes. Secondly, we fit the phase difference and used it to correct the phase of even or odd echoes. Finally, the corrected image was obtained by performing the inverse Fourier transform along phase-encoding direction in hybrid-space. The experimental results show that linear and nonlinear differences can be corrected and the intensity of ghost artifacts is significantly reduced. The effectiveness of the proposed method is demonstrated in ghost artifact removal.
文摘Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases. Multi-modality imaging approach is usually the more useful in diagnosis colorectal liver metastases. It is well established that hepatic resection improves the long-term prognosis of many patients with liver metastases. However, incomplete resection does not prolong survival, so knowledge of the exact extent of intra-hepatic disease is crucially important in determining patient management and outcome. The diagnosis of liver metastases relies first and totally on imaging to decide which patients may be surgical candidates. This review will discuss the imaging options and their appropriate indications. Imaging and evaluating of colorectal liver metastases （CRLM） have been performed with contrast-enhanced ultrasound, multidetector computed tomography, magnetic resonance imaging （MRI） with extra-cellular contrast media and liver-specific contrast media MRI, and positron emission tomography/computed tomography. This review
文摘OBJECTIVES: To investigate the findings of magnetic resonance (MR) imaging and histopathology in early postoperative normal brain, and to define the correlation between MR images and histopathology. METHODS: Thirty-six New Zealand rabbits weighing 2.0 to 3.0 kg were divided into 10 groups according to different postoperative days: 1 to 10 days. A partial resection of the parietooccipital region was performed under usual aseptic conditions after the animals were anesthetized intravenously with 3% pentobarbital (30 mg/kg). MR imaging procedures consisted of pre- and postcontrast scanning and were carried out on postoperative days 1 to 10. Brain tissue samples were prepared for examination immediately after MR scanning. Histopathological examination was done under light both and electron microscopes. The findings of MR imaging were compared with histopathologic findings. RESULTS: Surgical margin contrast enhancement on MR images could be seen 24 hours after surgery. The degree of contrast enhancement increased gradually up to 5 days postoperation, and no remarkable changes were present from days 5 to 10. Disruption of the blood brain barrier (BBB) was the main cause of contrast enhancement during the first 3 postoperative days. After that period, the mechanism responsible for contrast enhancement was the formation of neovascularity and a broken BBB. An increase in the amount of neovascularity played a predominant role in contrast enhancement in normal postoperative brain tissue. CONCLUSIONS: The features of enhanced MR images present at the surgical margin followed a typical time course during the early postoperative period. The role of neovascularity and BBB disruption in the formation of contrast enhancement at the surgical margin varies with time. Knowledge of the features of contrast enhancement in postoperative MR images of normal brain can help in differentiating benign changes from residual malignant glioma.
