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Biomedical subjects

W J Shih

Publications and source records attributed to W J Shih.

At least 91 records · Page 5Linked to original sources
PubMed1996

Massive pulmonary embolism without symptoms demonstrated by radionuclide imaging with thromboemboli in both main pulmonary arteries.

Massive pulmonary embolism is defined as an anatomic obstruction of 50% or more of the pulmonary artery. A reduction of at least 50% of the cross-sectional area of the pulmonary artery causes significant hemodynamic instability and marked hypoxia exhibiting syncope, apprehension, hypotension, diaphoresis, chest pain, altered mental status, and shortness of breath. A patient, who had no definite clinical signs and symptoms, was demonstrated to have massive pulmonary embolism by extensive mismatched ventilation-perfusion defects scintigraphically and confirmed as thromboemboli in the main pulmonary arteries on a standard CT of the thorax. The lack of clinical manifestations of massive pulmonary embolism might be related to the insidious onset and progressive formation of thromboembolism. The patient gradually adapted to and/or compensated for hemodynamic changes.

Humans↗
PubMed1996

A quadriplegic patient's cholescintigraphic findings: delayed gallbladder visualization and common bile duct dilation.

A Tc-99m DISIDA cholescintigraphic study of a 37-year-old patient with a 20-year history of quadriplegia demonstrated dilation of the common bile duct and delayed gallbladder visualization. A concurrent sonographic study showed an enlarged gallbladder with stones and dilation of the common bile duct. These findings were proved by autopsy. Quadriplegia secondary to a high level of spinal cord injury may result in gallbladder dysfunction.

Adult↗
PubMed1996

Assessing reproducibility by the within-subject coefficient of variation with random effects models.

In this paper we consider the use of within-subject coefficient of variation (WCV) for assessing the reproducibility or reliability of a measurement. Application to assessing reproducibility of biochemical markers for measuring bone turnover is described and the comparison with intraclass correlation is discussed. Both maximum likelihood and moment confidence intervals of WCV are obtained through their corresponding asymptotic distributions. Normal and log-normal cases are considered. In general, WCV is preferred when the measurement scale bears intrinsic meaning and is not subject to arbitrary shifting. The intraclass correlation may be preferred when a fixed population of subjects can be well identified.

Aged↗
PubMed1996

Discordant technetium-99m-MIBI and technetium-99m-HMPAO uptake of recurrent occipital meningioma on brain SPECT images.

Technetium-99m-HMPAO and 99mTc-MIBI brain SPECT, MRI, CT and cerebral angiogram were studied in a patient with recurrent occipital meningioma. MRI and CT of the head showed right cerebral hemispheric tumor masses involving parasagittal, temporal and parietoccipital areas. The angiograms showed an intense vascular tumor blush in recurrent mass lesions supplied by the following arteries: the meningeal branch of the right external carotid artery, the right middle cerebral artery, the right anterior cerebral artery and the right posterior cerebral artery. Although demonstrable 99mTc-MIBI lesions mass exactly corresponded to CT and MRI (T-1) findings, mass lesions exhibited a mismatch between 99mTc-MIBI (increased uptake) and 99mTc-HMPAO (absent uptake) brain SPECT images. Technetium-99m-MIBI images, rather than 99mTc-HMPAO brain SPECT, resulted in the correct pathological diagnosis of recurrent meningioma.

Aged↗
PubMed1996

Persistent lung uptake in the redistribution phase of Tl-201 chloride myocardial SPECTs--a sign of severe pulmonary edema: a case report.

Assessment of thallium (Tl)-201 chloride myocardial stress and rest single photon emission computed tomography (SPECT) includes left ventricular defects, left ventricular dilation, and pulmonary uptake. Lung uptake is associated with severe coronary artery disease or reflects transient left ventricular dysfunction and provides poor long-term prognosis. On redistribution imaging, lung activity should be absent or decreased relative to the myocardial activity. A patient with persistent Tl-201 uptake upon redistribution imaging due to lung edema secondary to congestive heart failure is reported. One should be aware that pulmonary edema/congestive heart failure can cause an increase in pulmonary uptake which persists in redistribution imaging.

Aged↗
PubMed1995

Re-evaluating design specifications of longitudinal clinical trials without unblinding when the key response is rate of change.

The design of clinical trials often requires knowledge of quantities such as between- and within subject variances about which only imprecise information exists. To provide assurance that the study has the desired power to detect a minimum clinically meaningful difference between treatment groups. Gould, Gould and Shih, and Shih have recommended obtaining relevant information from the trial at an interim stage without unblinding. Wittes and Brittain provided a similar recommendation, but viewed the portion up to the interim stage as an (internal) pilot study and required unblinding. This paper considers the problem of re-evaluating the design specifications in longitudinal clinical trials when the key response is the rate of change (slope). The proposed method aims to re-evaluate the sample size and study duration in a way that maintains the trial's blinding, using an EM algorithm. Simulation results show that the effect on type I error rate in negligible, but the potential gain in power can be substantial. The procedure is simple to use in practice, as it does not unblind patients' treatment identifications, and, since it does not unveil the relative efficacy of treatments, it fulfils the requirement of a valid 'administrative' (interim) analysis.

Algorithms↗
PubMed1995

Morphine-augmented cholescintigraphy enhances duodenogastric reflux.

Morphine intervention in cholescintigraphy decreases imaging time to diagnose acute cholecystitis. Not infrequently we observe duodenogastric reflux during scintigraphy with and without morphine intervention. To evaluate occurrence of duodenogastric reflux related to morphine, we reviewed 55 patients who underwent cholescintigraphy with (32) and without (23) morphine intervention. Morphine was injected when there was bowel activity with non-visualization of the gallbladder at 60 min. Duodenogastric reflux was identified by the appearance of activity in the area just below or immediately adjacent to the tip of the left hepatic lobe laterally. Among 32 patients with morphine intervention, 19 had acute cholecystitis and 13 chronic cholecystitis. Eleven of 19 (58%) with acute cholecystitis had duodenogastric reflux and 6 of 13 (46%) had duodenogastric reflux in chronic cholecystitis. The total of duodenogastric reflux in the group with morphine injection was 53%. Two patients' duodenogastric reflux occurred before morphine injection and was more apparent after morphine was given. In the without morphine group, 3 had acute cholecystitis and 20 had chronic cholecystitis; 2 (one acute and one chronic cholecystitis) of these 23 (9%) had duodenogastric reflux. Our results indicate: (1) occurrence of DG reflux in morphine augmented cholescintigraphy is not significantly different in cholecystitis from that in chronic cholecystitis; (2) duodenogastric reflux in morphine augmentation occurs significantly more often than without morphine intervention (p < 0.001). We conclude that cholescintigraphy with morphine enhances duodenogastric reflux. The degree of duodenogastric reflux in the acute cholecystitis patients has been more severe than in the chronic cholecystitis patients.

Acute Disease↗
PubMed1995

Tc-99m MAA lung perfusion scintigraphy performed before and after pulmonary embolectomy for saddle-type pulmonary embolism.

A 58-year-old man had shortness of breath, hypotension, and decreased partial pressure of oxygen (PO2) on the eighteenth day after undergoing craniotomy for a meningioma. Tc-99m MAA pulmonary perfusion scintigraphy showed little perfusion to the right lung and left lower lung and multiple perfusion defects in the left upper lung. Although the results of concurrent chest radiography were negative for pulmonary infiltrates, pulmonary angiography demonstrated a saddle-type embolism. The patient underwent emergency pulmonary artery embolectomy to remove blood clots and organized thromboemboli from the main pulmonary artery and the right and left pulmonary arteries. The patient's postoperative course was uneventful, and a second Tc-99m MAA lung perfusion scan demonstrated marked improvement in lung perfusion.

Embolectomy↗
PubMed1995

Diminished Tc-99m HMPAO pulmonary uptake in ex-smokers.

Normally, there is no localization of Tc-99m HMPAO in the lungs. Tc-99m uptake in smokers' lungs has been reportedly higher than in nonsmokers. Thus, the lung uptake may be used as a barometer of cigarette smoking. To assess whether there is a decrease in pulmonary uptake of Tc-99m HMPAO after cessation of smoking, the authors investigated the lung uptake of 31 male ex-smokers in comparison to smokers and nonsmokers. Anterior and posterior images were taken 10 minutes after intravenous injection of 20-25 mCi of Tc-99m HMPAO. Regions-of-interest over the liver and lungs in the anterior view were calculated. Duration of abstinence from smoking ranged from 5 months to 50 years. The mean lung/liver uptake in ex-smokers was 0.489 +/- 0.019 (sem). In a previous report, the mean lung/liver ratio for smokers (N = 30) was 0.805 +/- 0.040 (sem) and 0.408 +/- 0.019 (sem) for nonsmokers (N = 25). Compared with smokers, the lung/liver uptake ratio of ex-smokers was significantly lower (P < 7 x 10(-9)). The lung/liver uptake ratio of ex-smokers was significantly higher than that of nonsmokers (P < 0.005). The authors conclude that pulmonary Tc-99m HMPAO uptake of smokers is significantly diminished after quitting smoking. However, the lung uptake of ex-smokers is higher than that of non-smokers. The uptake in the lung induced by smoking appears to be partially reversible after the cessation of smoking.

Aged↗