Metal artifact reduction and image quality evaluation of lumbar spine CT images using metal sinogram segmentation.

Metal artifacts often appear in the images of computed tomography (CT) imaging. In the case of lumbar spine CT images, artifacts disturb the images of critical organs. These artifacts can affect the diagnosis, treatment, and follow up care of the patient. One approach to metal artifact reduction is the sinogram completion method. A mixed-variable thresholding (MixVT) technique to identify the suitable metal sinogram is proposed. This technique consists of four steps: 1) identify the metal objects in the image by using k-mean clustering with the soft cluster assignment, 2) transform the image by separating it into two sinograms, one of which is the sinogram of the metal object, with the surrounding tissue shown in the second sinogram. The boundary of the metal sinogram is then found by the MixVT technique, 3) estimate the new value of the missing data in the metal sinogram by linear interpolation from the surrounding tissue sinogram, 4) reconstruct a modified sinogram by using filtered back-projection and complete the image by adding back the image of the metal object into the reconstructed image to form the complete image. The quantitative and clinical image quality evaluation of our proposed technique demonstrated a significant improvement in image clarity and detail, which enhances the effectiveness of diagnosis and treatment.

Diagnostic performance of perfusion MRI in differentiating low-grade and high-grade gliomas: advanced MRI in glioma, A Siriraj project.

BACKGROUND: To determine the usefulness of the perfusion MRI technique at Siriraj Hospital for differentiating between high- and low-grade gliomas by using pathological results as the gold standard. MATERIAL AND METHOD: The authors prospectively investigated 64 consecutive patients who were suspected as cerebral glioma from prior conventional imaging. Cerebral perfusion study was achieved during the first pass of a bolus of gadolinium-based contrast agent. All post-processing MRI images were interpreted by two board-certified neuroradiologists (more than 10-year-experience), one radiology resident and one well-trained technician, who separately performed and blinded from the pathological results. RESULTS: Forty-four patients diagnosed as glioma were included in this study. There were 26 cases of high-grade and 18 cases of low-grade gliomas. The cerebral blood volume and flow and its ratios had a strong association with the grade of glioma. The areas under the ROC curve for CB K CBVratio (rCBV), CBF and CBF ratio (rCBF) are 0.778, 0.769, 0.769, and 0.772, respectively. On the basis of equal misclassification rates, a cutoff value of 6.15 for CBV (sensitivity, 81.5%; specificity, 64.7%), a cutoff value of 2.38 for the rCBV (sensitivity, 88.9%; specificity, 64.7%), a cutoff value of 0.66 for CBF (sensitivity 81.5%; specificity 70.6%), and a cutoff value of 2.6 for the rCBF (sensitivity, 85.2%; specificity, 70.60%) best discriminated the high and low-grade gliomas. CONCLUSION: Preoperative radiologic grading of gliomas based on conventional MR imaging is sometimes unreliable. The cerebral perfusion measurements can significantly improve the sensitivity and predictive values of radiologic glioma grading. The rCBV measurement is the best parameter for tumor grading due to the highest sensitivity.

Vertebral body compression fracture: discriminating benign from malignant causes by diffusion-weighted MR imaging and apparent diffusion coefficient value.

OBJECTIVE: To evaluate the diagnostic performance of apparent diffusion coefficient (ADC) value in discriminating benign from malignant vertebral compression fracture. MATERIAL AND METHOD: 22 symptomatic patients with compression fracture of vertebra referred for conventional MRI spines during January 2009-March 2010 underwent additional diffusion weighted MR techniques. Evaluation of diffusion weighted MR imaging and quantified ADC value from reconstructed ADC map were performed. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value of apparent diffusion coefficient (ADC) value were calculated. RESULTS: A total of 39 vertebral fractures; 7 malignant compression fractures and 32 benign compression fractures were evaluated. The difference between ADC values of malignant, benign compression fracture and normal vertebrae were statistically significant (p < 0.0001). The accuracy, sensitivity and specificity were 89.7%, 85.7% and 90.6% respectively with the ADC threshold of 0.89 to discriminate malignancy. CONCLUSION: The ADC promises to be an effective implement for characterization of vertebral body compression fracture in differentiating benign and malignant compression fractures.

Predictive value of magnetic resonance imaging in cervical spondylotic myelopathy in prognostic surgical outcome.

OBJECTIVE: Establish the predictive value of magnetic resonance imaging (MRI) for cervical spondylotic myelopathy as being a good operative outcome. MATERIAL AND METHOD: A retrospective study of the 52 consecutive patients with cervical spondylotic myelopathy underwent both magnetic resonance imaging (MRI) cervical spines examination at Siriraj Hospital between January 2005 and June 2007. Surgery was divided into two groups: "Good" operative outcome (35 patients) and "No improvement group" (17 patients). Two neuroradiologists independently identified the MR images data that showed the maximum stenosis on sagittal and axial sections and recorded predictive MRL parameters: T2-weighted signal change of the spinal cord, cross-sectional area of the spinal cord, anteroposterior (AP) diameter of the spinal canal and the spinal cord and AP-compression ratio (AP diameter/transverse diameter of the spinal cord). RESULTS: There were no statistically significant differences between both groups in all parameters. CONCLUSION: The AP-diameter of the spinal canal and spinal cord, AP-compression ratio and signal change of the spinal cord are not useful in predicting prognosis outcome in patients with cervical spondylotic myelopathy. In addition, cross-sectional area of the spinal cord cannot confidentially be used as predictive factor in CSM patients due to many influent factors of surgical outcome. A further prospective study without patient selective bias may offer more definite results to confirm these findings.

Optic-spinal inflammatory demyelinating disease: (OS-IDD) patients in Siriraj Hospital.

OBJECTIVE: To study the demographic data of optico-spinal inflammatory demyelinating disease (OS-IDD) patients at Siriraj Hospital between January 1997 and October 2006. DESIGN: Retrospective study of OS-IDD patients. RESULTS: There were 84 OS-IDD patients. Cerebrospinal fluid analysis revealed higher white blood cell count and neutrophilia in neuromyelitis optica (NMO) patients than those of multiple sclerosis (MS) patients. NMO had an average length of 4.1 segments of the cervical and 6.5 segments of thoracic cord involvement. CONCLUSION: Among Thai OS-IDD patients, on the basis of clinical features, NMO was hardly differentiated from MS.