Biomedical subjects

Woo Sun Jun

Publications and source records attributed to Woo Sun Jun.

3 recordsLinked to original sources

PubMed2003

Osseous metastasis from renal cell carcinoma: "flow-void" sign at MR imaging.

PURPOSE: To characterize the appearance and determine the importance of the "flow-void" sign on magnetic resonance (MR) images of patients with osseous metastasis from renal cell carcinoma. MATERIALS AND METHODS: Three musculoskeletal radiologists retrospectively and independently reviewed the medical records of 16 patients who had undergone MR imaging and in whom 20 osseous metastatic lesions from renal cell carcinoma had been diagnosed on the basis of clinical and radiologic findings. They assessed the MR images for the presence and frequency of the flow-void sign--multiple dot-like or tubular structures with low signal intensity. They then compared these findings on MR images with the corresponding areas on available images obtained with radiography (n = 16), computed tomography (CT) (n = 6), and digital subtraction angiography (n = 3) and with the results of histopathologic analysis for the same patient group. They noted the location, diameter, and appearance of the lesion and the flow-void sign, as well as variations in signal intensity within the lesion and among lesions. Statistical analysis was performed to determine the level of interobserver agreement. RESULTS: Radiographic findings and the level of signal intensity on MR images were nonspecific for diagnosis of osseous metastasis from renal cell carcinoma. The flow-void sign was identified at the lesion core or margin with a mean frequency of 76.7% by the three observers (in 15, 16, and 15 of 20 lesions, by observers 1, 2, and 3, respectively). Most of these areas of low signal intensity were tubular structures of less than 3 mm in diameter; in three lesions, they measured 5-8 mm in diameter. In 14 lesions, these structures corresponded to dilated blood vessels or veins identifiable on CT images (six lesions) or digital subtraction angiographic images (four lesions) or at histopathologic analysis (four lesions). The flow-void sign on MR images corresponded to vessels depicted on the CT scans available for six lesions and on the angiographic images available for four lesions. CONCLUSION: Observation of the flow-void sign in lesions depicted on musculoskeletal MR images may prove helpful for diagnosing osseous metastasis from renal cell carcinoma and for treatment planning, especially in patients with occult or forgotten primary renal tumor.

Aged↗

PubMed2002

A straightforward algorithm for the quantification of power Doppler signals.

RATIONALE AND OBJECTIVES: To document a simple algorithm that quantifies power Doppler signals by computer-based statistical image analysis. METHODS: Personal computer-based software was developed. Color pixels representing power Doppler signals were separated from the background gray pixels in power Doppler images converted in BMP format. To avoid misregistration during this segmentation, a threshold value is required to adequately distinguish between gray and color pixels. Equating the intensity of each color pixel to a Power Value (PV), a histogram of Power Values in power Doppler images was obtained. RESULTS: The software was designed to allow users to adjust two thresholds (Difference Threshold and Intensity Threshold) by observing the segmentation results in real time. The software calculates the following indexes within any region of interest as defined by the operator: mean PV, peak PV, standard deviation of PV, percentage power Doppler area, and integrated PV per unit area. CONCLUSIONS: Power Doppler signals can be objectively quantified using this straightforward algorithm. This simple and practical method can be applied to comparative or longitudinal studies upon vascularity or blood flow.

Algorithms↗

PubMedDate not supplied

Transforaminal epidural steroid injection for lumbosacral radiculopathy: preganglionic versus conventional approach.

OBJECTIVE: The present study was undertaken to evaluate the effectiveness of transforaminal epidural steroid injection (TFESI) with using a preganglionic approach for treating lumbar radiculopathy when the nerve root compression was located at the level of the supra-adjacent intervertebral disc. MATERIALS AND METHODS: The medical records of the patients who received conventional TFESI at our department from June 2003 to May 2004 were retrospectively reviewed. TFESI was performed in a total of 13 cases at the level of the exiting nerve root, in which the nerve root compression was at the level of the supra-adjacent intervertebral disc (the conventional TFESI group). Since June 2004, we have performed TFESI with using a preganglionic approach at the level of the supra-adjacent intervertebral disc (for example, at the neural foramen of L4-5 for the L5 nerve root) if the nerve root compression was at the level of the supra-adjacent intervertebral disc. Using the inclusion criteria described above, 20 of these patients were also consecutively enrolled in our study (the preganglionic TFESI group). The treatment outcome was assessed using a 5-point patient satisfaction scale and by using a VAS (visual assessment scale). A successful outcome required a patient satisfaction scale score of 3 (very good) or 4 (excellent), and a reduction on the VAS score of > 50% two weeks after performing TFESI. Logistic regression analysis was also performed. RESULTS: Of the 13 patients in the conventional TFESI group, nine showed satisfactory improvement two weeks after TFESI (69.2%). However, in the preganglionic TFESI group, 18 of the 20 patients (90%) showed satisfactory improvement. The difference between the two approaches in terms of TFESI effectiveness was of borderline significance (p = 0.056; odds ratio: 10.483). CONCLUSION: We conclude that preganglionic TFESI has the better therapeutic effect on radiculopathy caused by nerve root compression at the level of the supra-adjacent disc than does conventional TFESI, and the difference between the two treatments had borderline statistical significance.

Adolescent↗