Biomedical subjects

T T Shih

Publications and source records attributed to T T Shih.

25 records · Page 2Linked to original sources

PubMed1992

Multiplanar gradient recalled images of the knee: comparison of different flip angles and echo times.

To determine the most appropriate combination of echo time (TE) and flip angle in gradient echo images of the knee, the authors used different TEs (10, 20 and 30 msec) and flip angles (10, 30, 50, 70, 90, 120 and 150 degrees) to perform a systematic study of MRI on 10 volunteer knees. Contrast-to-noise ratios of cartilage-fat, fluid-cartilage, fluid-fat and fluid-ligament were calculated and compared. Images with a 30-degree flip angle combined with 20 msec of TE were found to have the best contrast-to-noise ratios in both objective data analysis and subjective observation. Hyaline cartilage of the knee was hyperintense and was well delineated on this pulse sequence, appearing distinct in contrast to the intra-articular fluid. It is concluded that this T2-weighted gradient echo pulse sequence is an alternative to conventional spin echo T2-weighted imaging of the knee.

Echo-Planar Imaging↗

PubMed1990

Diagnosis of cardiac metastasis by computed tomography: report of 5 cases.

Five patients with underlying malignancy were detected antemortemly to have cardiac metastasis by post-enhanced CT scanning. The most common presentations were abnormal heart sounds, electrocardiographic changes and inexplicable heart failure; which lead us to suspect cardiac metastasis. One patient had an "engorged azygous knob" on his chest x-ray film, which provided a clue to possible cardiac metastasis. All of these patients had tumor thrombi in their large tributary veins in addition to the primary tumors. Thus, we advanced the CT scan to the cardiac region and cardiac metastases were, therefore, diagnosed. The tumor thrombi in the large tributary veins seemed to be the source for intracardiac spreading. Cardiac angiographies were performed in 3 patients and confirmed the diagnosis. We conclude that post-enhanced CT scanning is useful in the diagnosis of cardiac metastasis and the presence of tumor thrombi in the large tributary vein is an early sign of cardiac involvement.

Adult↗

PubMed1988

Acute stroke: detection of changes in cerebral perfusion with dynamic CT scanning.

Fifteen patients with acute cerebral infarct in the territory of the middle cerebral artery were examined with dynamic computed tomography (CT) to evaluate cerebral perfusion changes. Perfusion changes could be detected in 93% of the patients within a short period after the attack (the earliest instance was within 2 hours) and before any detectable morphologic change. The attenuation coefficient of the area of infarction showed a statistically significant difference in peak amplitude compared with that in the contralateral unaffected brain or with that in the control group (P less than .05). A delay in the time to peak in the affected side versus in the contralateral side was observed in six patients with stroke and ranged from 4.2 to 49.2 seconds with or without a change in peak amplitude. The clinical outcome in the patients correlated well with the initial perfusion change measured with dynamic CT scanning. The greater the difference in peak amplitude, the worse the residual neurologic defect. Patients with a prolonged time to peak (greater than 8 seconds) usually had poor clinical outcome. The whole dynamic study took 10-15 minutes more than a conventional CT study but provided more complete information as a basis for clinical treatment and an indication of clinical outcome.

Acute Disease↗

PubMedDate not supplied

The evaluation of false negative mammography from malignant and benign breast lesions.

Preoperative mammograms from 395 breast cancers and 132 benign breast lesions were enrolled for this study. The false-negative (FN) rate for breast cancers from preoperative reading was 9.6% with 38 breast cancers missed on mammograms. The statistically significant differences occurred between true-positive (TP) and FN cancers for younger age (P<.025), smaller lesion size (P<.001), denser breast (P<.05), deep retroglandular location (P<.001). None of the FN cancers exhibited calcifications. The FN rate for mammography for benign breast lesions from preoperative reading was 18.9% with 25 lesions misdiagnosed. The statistically significant difference between benign TP and FN lesions occurred for central and subareolar location (P<.025). Exploration of possible factors and imaging features in FN mammograms can help reduce the FN rate for mammography.

Adult↗

PubMedDate not supplied

Bilateral elastofibroma dorsi. Two case reports.

Elastofibroma dorsi is a benign fibroproliferative lesion of unknown pathogenesis. It is most commonly found in the periscapular region in elderly women. The majority of patients are asymptomatic. The lesions have a characteristic location and a specific magnetic resonance imaging (MRI) appearance allowing accurate prospective diagnosis. The importance of recognizing the benign nature of this lesion to avoid an unnecessary operation is apparent. We describe two cases of bilateral elastofibroma dorsi with characteristic findings on MRI and typical histological appearances.

Bone Neoplasms↗

PubMedDate not supplied

Early diagnosis of single segment vertebral osteomyelitis--MR pattern and its characteristics.

Nine cases of single segment vertebral osteomyelitis were included based on the single level of vertebral body involvement according to the MR findings. They were 3 cases with tuberculous infection and 6 cases with pyogenic infection. The vertebral body involvement was presented as abnormal signal changes (100%) and heterogenous enhancement (77.7%). They usually caused the cortical disruption in its anterior aspect (100%). It goes along the upward subligamentous spread (100%) most often, then the upper disc involvement (66.6%) and downward subligamentous spread (55.5%). The lower disc involvement is least common (11.1%). By using these criteria, the single segment vertebral osteomyelitis could be earlier diagnosed.

Adult↗

PubMedDate not supplied

Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance.

PURPOSE: To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue. MATERIALS AND METHODS: Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations. RESULTS: Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1-and high signal on T2-weighted images, and low signal on both T1-and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges. CONCLUSION: MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.

Adult↗