Biomedical subjects

T H Lim

Publications and source records attributed to T H Lim.

At least 19 recordsLinked to original sources

PubMed2000

Application of breath-hold T2-weighted, first-pass perfusion and gadolinium-enhanced T1-weighted MR imaging for assessment of myocardial viability in a pig model.

The purpose of this study was to correlate the abnormal signal area on various magnetic resonance (MR) images to the infarct area on pathologic examination and to assess the myocardial viability on the basis of MR images. T2-weighted, first-pass perfusion, and delayed gadolinium-enhanced T1-weighted images were used as "one-stop examinations" in a pig model of reperfused myocardial infarction. The results of each MR image were compared with those of 2,3, 5-triphenyltetrazolium chloride (TTC) staining. The abnormal signal areas on T2-weighted and Gd-enhanced T1-weighted images were larger than the infarct areas on TTC staining (34.7% and 32.3% vs. 28.3%; P< 0.05), whereas the nonperfused areas on perfusion images were correlated (25.6% vs, 28.3%; P = 0.139). Electron microscopic examination showed severely distorted ultrastructures in the infarct areas and mildly damaged ultrastructures in the peri-infarct areas. Perfusion images probably reflected the infarct areas, whereas T2-weighted and Gd-enhanced T1-weighted images seemed to include peri-infarct as well as infarct areas.

Animals↗

PubMed2000

Subjective visual experience during phacoemulsification and intraocular lens implantation under topical anesthesia.

OBJECTIVE: The aim of this study was to investigate the subjective visual experience of patients during phacoemulsification and intraocular lens (IOL) implantation under topical anesthesia. DESIGN: Postoperative questionnaire survey. PARTICIPANTS: The study cohort consisted of 52 patients with cataracts. There were 18 male (34.6%) and 34 female (65.4%) patients. Their mean (+/- SD) age was 67.5 (+/-10.8) years. INTERVENTION: The patients underwent routine phacoemulsification and IOL implantation under topical anesthesia. MAIN OUTCOME MEASURES: The patients were interviewed on the same day after their operation regarding their visual experience in the operated eye during surgery. RESULTS: All patients (100%) reported that they could see at least some light during the surgery. Some patients reported they could also see one or more colors (50 patients, 96.2%), movements (32 patients, 61.5%), flashes (24 patients, 46.2%), the surgeon's fingers/hands (13 patients, 25%), instruments (12 patients, 23.1%), and/or the surgeon (4 patients, 7.7%). The colors seen included red (24 patients, 46.2%), yellow (23 patients, 44.2%), blue (12 patients, 23.1%), green (7 patients, 13.5%), and orange (6 patients, 11.5%). Eight patients (15.4%) saw the spectrum of colors similar to that of the rainbow. Twenty-four patients (46.2%) reported that the brightness of light changed during the course of the operation. Eight patients (15.4%) found their visual experience frightening. There was no statistically significant association between those who found the visual experience frightening and the sex or age of the patient, a history of cataract operation in the fellow eye, the type of visual sensation experienced, or the presence of coexisting ocular pathology. CONCLUSION: All patients undergoing phacoemulsification under topical anesthesia experience a variety of visual sensations that may be frightening in a small proportion of patients.

Aged↗

PubMed2000

Subjective visual experience during phacoemulsification and intraocular lens implantation using retrobulbar anesthesia.

PURPOSE: To investigate the subjective visual experience of patients during phacoemulsification and intraocular lens (IOL) implantation using retrobulbar anesthesia. SETTING: Department of Ophthalmology, Tan Tock Seng Hospital, Singapore. METHODS: Seventy cataract patients who had routine phacoemulsification and posterior chamber IOL implantation under retrobulbar anesthesia were interviewed on the day of their surgery regarding their visual experience in the operated eye during surgery. Thirty-nine men (55.7%) and 31 women (44.3%) were included in the study. Their mean age was 65.1 years (range 37 to 87 years). Preoperative best corrected visual acuity ranged from 6/12 to counting fingers. Sixty eyes (85.7%) had no ocular pathology other than cataract. Eleven patients (15.7%) reported no light perception during the surgery. The rest reported they could see light (59 patients, 84.3%), 1 or more colors (39 patients, 55.7%), flashes (35 patients, 50.0%), movements (34 patients, 48.6%), instruments (12 patients, 17.1%), and the surgeon's fingers or hands (11 patients, 15.7%). The colors seen included red (23 patients, 32.9%), blue (17 patients, 24.3%), yellow (12 patients, 17.1%), green (7 patients, 10. 0%), and orange (1 patient, 1.4%). Eight patients (11.4%) saw a spectrum of colors similar to a rainbow. Thirty-one patients (44.3%) reported that the brightness of light changed during surgery. Five patients (7.1%) found their visual experience frightening. Patients who reported seeing colors (P =.048, Fisher exact test) and flashes of light (P =.027, Fisher exact test) were more likely to find the experience frightening. There was no statistically significant correlation between those who found the experience frightening and patient sex or age, length of surgery, or history of cataract surgery in the fellow eye. CONCLUSIONS: Many patients having phacoemulsification and IOL implantation under retrobulbar anesthesia experienced a variety of visual sensations that were frightening in a small proportion of cases.

Adult↗

PubMed2000

Central serous retinopathy complicating systemic lupus erythematosus: a case series.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder with widespread manifestations including the eye. Central serous retinopathy (CSR) has been associated as a complicating event in SLE, although it is uncommon. We present a case series of four female Chinese SLE patients who developed CSR during the course of their systemic disease. All four presented clinically with typical CSR. Angiographic findings did not show evidence of choroidal ischaemia or delayed choroidal filling. Resolution of the serous retinal detachment occurred in all four patients. Recovery of vision was seen in three patients. The clinical outcome was similar to that occurring in the usual male population. Central serous retinopathy as a manifestation of SLE may be caused by various factors. These include SLE-associated choroidopathy, systemic hypertension, renal disease, retinal pigment epithelial dysfunction and glucocorticoid therapy.

Adult↗

PubMed2000

Biomechanical effect of anterior grafting devices on the rotational stability of spinal constructs.

In the thoracolumbar spine, frequently strut grafting is used to restore the anterior and middle column defects. Biomechanical stability of the surgical construct may be altered significantly depending on the type of anterior grafting devices. In this study, a biomechanical flexibility test was conducted to compare the stabilizing role of various types of anterior grafting devices, such as a polymethylmethacrylate block, tricortical iliac crest bone graft, one large Harms cage, and two small Harms cages using a calf lumbar corpectomy model. The Harms cage, especially one large cage, improved the axial rotational stability significantly in both anterior and posterior fixation groups as compared with the iliac bone or polymethylmethacrylate. No significant difference in the stabilizing role was found among different grafting devices in lateral bending, flexion, and extension. These results suggest that a more rigid spinal construct can be obtained by using a metal cage with improved friction at the cage-bone interface.

Animals↗

PubMed2000

Presumed rhegmatogenous retinal detachment in patients with retinoblastoma.

PURPOSE: To review the characteristics, treatment, and outcome of presumed rhegmatogenous retinal detachment (RD) in patients with retinoblastoma. METHODS: Descriptive consecutive case series study from 1970 to 1996. RESULTS: Of 45 eyes with retinoblastoma that received various modalities of eye-sparing treatment and adequate follow-up, five developed presumed rhegmatogenous RD after treatment. All five eyes had previous treatment with external beam radiation, four of which also had been treated with cryotherapy. To minimize the potential spread of the malignancy intraoperatively, long disease-free intervals were ensured before scleral buckling surgeries were performed, and special care was taken during subretinal fluid drainage. The RDs were totally reattached in three eyes and partially reattached in the other two. CONCLUSION: Presumed rhegmatogenous RD may occur after external beam radiation or cryotherapy for retinoblastoma. It poses special challenges in management.

Adolescent↗

PubMed2000

Irreversibly damaged myocardium at MR imaging with a necrotic tissue-specific contrast agent in a cat model.

PURPOSE: To investigate the capability of a necrosis-avid magnetic resonance (MR) contrast agent, bis-gadolinium mesoporphyrins, for assessment of irreversibly damaged myocardium and to evaluate the time course of signal enhancement in the reperfused myocardium. MATERIALS AND METHODS: Nine cats were subjected to 90 minutes of occlusion of the left anterior descending coronary artery followed by 90 minutes of reperfusion. Contrast material-enhanced T1-weighted spin-echo images were obtained for 12 hours in five cats and 6 hours in four cats. Pathologic examinations of the resected specimens were performed with 2'3'5-triphenyl tetrazolium chloride (TTC) histochemical staining and electron microscopy. The size of enhanced area on MR images was compared with that of irreversibly damaged myocardium with TTC staining. The time course of signal enhancement was evaluated. RESULTS: The size of enhanced area on MR images was well correlated with that of irreversibly damaged myocardium with TTC staining. Maximum enhancement occurred 1-3 hours after administration of the contrast material, with mean enhancement of 171% that of normal myocardium. Electron microscopic examinations showed severe myocardial damage in the irreversibly damaged myocardium but only mild edematous changes in the reversibly damaged myocardium. CONCLUSION: MR images enhanced with bis-gadolinium mesoporphyrins provide accurate sizing of irreversibly damaged myocardium with a strong and persistent signal enhancement in the reperfused myocardium.

Animals↗

PubMed2000

Flexibility of lumbar spinal motion segments correlated to type of tears in the annulus fibrosus.

OBJECT: The authors conducted a study in which their objective was to measure the effect of tears in the annulus fibrosus on the motions of lumbar spinal motion segments. METHODS: Lumbar spinal motion segments were harvested from human cadavers and studied using a 1.5-tesla magnetic resonance imager. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Displacements and rotations were measured using a kinematic system. The segments were sectioned on a cryomicrotome to verify the presence of tears in the annulus fibrosus. CONCLUSIONS: Tears in the annulus fibrosus increase the amount of motion that results from a torque applied to the motion segment. Radial and transverse tears of the annulus fibrosus have a greater effect on motions produced by an axial rotatory torque than on those produced by flexion, extension, or lateral bending torques. The difference between normal discs and discs with annular tears is more marked during moments of axial rotational than during those of flexion, extension, or lateral bending.

Aged↗

PubMed2000

Giant cell arteritis causing bilateral sequential anterior ischaemic optic neuropathy--a case report.

Giant cell arteritis is a chronic granulomatous inflammation of unknown aetiology involving large and medium size arteries in the elderly. It causes acute visual loss from ischaemia to the optic nerves or central retinal artery occlusion. This is a rare cause of anterior ischaemic optic neuropathy in our local population. We present a patient who had bilateral loss of vision from sequential arteritic ischaemic optic neuropathy. She was treated with intravenous steroids immediately. Diagnosis was based on histopathological studies of temporal artery biopsies.

Aged↗

PubMed1999

Different remodeling of descending thoracic aorta after acute event in aortic intramural hemorrhage versus aortic dissection.

The natural healing process of medically treated aortic dissection (AD) and aortic intramural hemorrhage (AIH) developed in the descending thoracic aorta was compared to test the hypothesis that absence of intimal tear and flow communication in AIH may have different impact on the remodeling of the affected aorta after the acute event. In 25 patients with AD and 20 with AIH involving distal descending thoracic aorta stabilized with medical treatment, follow-up (mean 9 months) transesophageal echocardiography was performed to measure the maximal dimensions of aorta, true lumen, false lumen in AD, and abnormal wall thickening in AIH. The sex ratio, prevalence of hypertension, baseline maximal dimension, and longitudinal extent of the affected aorta did not show any significant difference in both groups. Patients with AIH were older than those with AD (63 +/- 10 vs 50 +/- 9, p <0.01). Disappearance of abnormal wall thickening with complete restoration of the aorta occurred in 70% (14 of 20) patients with AIH, which was significantly more frequent than in AD (8%, p <0.01). In AD, progressive dilatation of the aorta with continuous flow communication in the false lumen resulted in larger dimension of the aorta than in AIH (44 +/- 13 vs 35 +/- 7 mm, p <0.01). Absence of persistent flow communication resulted in a favorable remodeling process in AIH affecting distal descending aorta. This finding, along with different mean age in AIH and AD, may suggest that AIH is not just a precursor of overt AD but a distinct disease entity with different pathophysiology.

Acute Disease↗

PubMed1999

MRI of myocardial infarction.

With the advances in magnetic resonance imaging (MRI) technology that have occurred in recent years, it is possible to examine the myocardial status with high spatial and temporal resolutions in the evaluation of ischemic heart disease. The purpose of this article is to review the current status and the role of MRI for the evaluation of myocardial infarction. We discuss the pathophysiology of myocardial infarction, MRI techniques for the evaluation of myocardial status, and the pathophysiological significance of MR signal changes observed in various MRI techniques. We conclude that, with further development of MR techniques and contrast agents, MRI will play an increasing role in the diagnosis of ischemic heart disease. J. Magn. Reson. Imaging 1999;10:686-693.

Animals↗

PubMed1999

Exogenous lipoid pneumonia: high-resolution CT findings.

The aim of this study was to assess high-resolution computed tomography (HRCT) findings of exogenous lipoid pneumonia. High-resolution computed tomography was obtained in 25 patients with proven exogenous lipoid pneumonia resulting from aspiration of squalene (derived from shark liver oil). Diagnosis was based on biopsy (n = 9), bronchoalveolar lavage (n = 8), or sputum cytology and clinical findings (n = 8). The clinical history of taking squalene was confirmed in all patients. The CT findings were classified into three patterns: diffuse ground-glass opacity, consolidation, and interstitial abnormalities. Distribution of the abnormalities, duration of taking squalene, predisposing factors for aspiration, and route of administration were analyzed. Ten patients showed diffuse ground-glass opacity pattern. Seven of 10 patients had predisposing conditions such as unconsciousness, pharyngeal dysmotility, or motor disturbances, and 6 patients had a recent history of taking large amount of squalene through nasal route. Seven patients who had consolidation pattern had a history of taking squalene for several months and did not have any predisposing factor. All of the 5 patients who had a pattern of interstitial abnormalities had a history of taking squalene longer than 1 year and showed segmental distribution of interstitial thickening with interposing ground-glass opacities. Three patients simultaneously had two different patterns at different lobes of the lung. The HRCT findings of lipoid pneumonia are ground-glass opacities, consolidation, and interstitial abnormalities. These HRCT findings with appropriate inquiries could be useful for diagnosis of exogenous lipoid pneumonia.

Adult↗

PubMed1999

Enrichment of fetal trophoblasts and nucleated erythrocytes from maternal blood by an immunomagnetic colloid system.

The aim of this study was to isolate fetal trophoblasts and nucleated erythrocytes from maternal blood using the immunomagnetic colloid system. About 25 ml of maternal blood was collected from pregnant women between of 14 and 20 weeks gestation. Nucleated erythrocytes (NRBCs) were isolated from 5 ml of maternal blood and a nested polymerase chain reaction for the Y chromosome was used to determine fetal origin. The sensitivity of the fetal gender diagnosis was 80% and the specificity was 86%. Both fetal trophoblasts and NRBCs were isolated from the remaining 20 ml of maternal blood. The fetal gender of the trophoblast-enriched fraction was determined using fluorescence in situ hybridisation (FISH) with dual-colour XY-specific DNA probes. XY-specific signals were observed in 0.38% of cells sorted from all pregnant women carrying male fetuses (n = 10). Simultaneous immunophenotyping for the fetal haemoglobin and FISH using XY probes were used to evaluate the fetal origin of cells enriched with anti-CD71. The mean percentage of male fetal erythroblasts was 0.24% and the number of fetal erythroblasts was estimated to be about 672 in 20 ml of maternal blood. The number of fetal erythroblasts detected in our study was greater than that detected by most other separation techniques. Our study shows that it would be feasible to use the immunomagnetic colloid system for the isolation of both trophoblasts and NRBCs from the same maternal blood sample with relatively good efficiency.

Amniocentesis↗

PubMed1999

Cerebral metabolic abnormalities in congestive heart failure detected by proton magnetic resonance spectroscopy.

OBJECTIVES: Using proton magnetic resonance spectroscopy, we investigated cerebral metabolism and its determinants in congestive heart failure (CHF), and the effects of cardiac transplantation on these measurements. BACKGROUND: Few data are available about cerebral metabolism in CHF. METHODS: Fifty patients with CHF (ejection fraction < or = 35%) and 20 healthy volunteers were included for this study. Of the patients, 10 patients underwent heart transplantation. All subjects performed symptom-limited bicycle exercise test. Proton magnetic resonance spectroscopy (1H MRS) was obtained from localized regions (8 to 10 ml) of occipital gray matter (OGM) and parietal white matter (PWM). Absolute levels of the metabolites (N-acetylaspartate, creatine, choline, myo-inositol) were calculated. RESULTS: In PWM only creatine level was significantly lower in CHF than in control subjects, but in OGM all four metabolite levels were decreased in CHF. The creatine level was independently correlated with half-recovery time and duration of heart failure symptoms in PWM (r = -0.56, p < 0.05), and with peak oxygen consumption and serum sodium concentration in OGM (r = 0.58, p < 0.05). Cerebral metabolic abnormalities were improved after successful cardiac transplantation. CONCLUSIONS: This study shows that cerebral metabolism is abnormally deranged in advanced CHF and it may serve as a potential marker of the disease severity.

Adult↗

PubMed1999

Proton magnetic resonance spectroscopy (1H-MRS) findings for the brain in patients with liver cirrhosis reflect the hepatic functional reserve.

OBJECTIVE: Proton magnetic resonance spectroscopy (1H-MRS) has been used to assess the metabolic changes in the brain in patients with liver cirrhosis. Decreased myo-inositol and increased glutamine levels were noted to be the most sensitive spectroscopic markers for cirrhotic patients with hepatic encephalopathy (HE). The purpose of this study was to assess how the abnormalities seen on the 1H-MRS of the brain in patients with liver cirrhosis are related to clinical and laboratory parameters. METHODS: In a prospective study, localized 1H-MRS was performed in the basal ganglia and parietal white matter regions in liver cirrhosis patients with (n = 48) and without (n = 52) HE and chronic hepatitis (CH) (n = 15), and in normal controls (n = 20). RESULTS: Among cirrhotic patients, the myo-inositol levels were significantly lower (p < 0.01) and the glutamine levels were higher (p < 0.05) for patients with HE than for those without HE. The myo-inositol and glutamine levels, respectively, were inversely (r = -0.50; p < 0.001) and linearly (r = 0.50; p < 0.001) related to the Child-Pugh score. However, by subgroup analysis of Child-Pugh class C patients, there were no significant differences in the myo-inositol and glutamine levels between cirrhotic patients with (n = 40) and without HE (n = 24). A follow-up study of eight cirrhotic patients with HE showed no significant differences in the myo-inositol and glutamine levels after clinical improvement of HE. CONCLUSIONS: The abnormalities seen on the 1H-MRS of the brain of patients with liver cirrhosis are not likely to reflect the severity of HE or acute alteration in the level of consciousness. Rather, we believe they represent the chronic metabolic derangement of the brain associated with hepatic functional reserve.

Adult↗

PubMed1999

Location of the primary motor cortex in schizencephaly.

BACKGROUND AND PURPOSE: Functional reorganization of the brain can result from congenital brain disorders as well as from brain infarction. The purpose of our study was to use functional MR imaging to determine whether reorganization of brain function occurs in patients with schizencephaly. METHODS: Four patients with schizencephaly (three right-handed, one ambidextrous) presented with seizures. Associated lesions included agenesis of the corpus callosum (n = 1) and absence of the septum pellucidum (n = 1). Functional MR imaging was performed in each patient using a single-section fast low-angle shot (FLASH) blood oxygen level-dependent (BOLD) technique at 1.5 T in a standard head coil. The motor cortex was initially identified on an axial T1-weighted anatomic image. Thirty consecutive images were obtained during a motor task consisting of repetitive finger-to-thumb opposition. The percentage of change in increased signal intensity was calculated for the primary motor area. An ipsilateral activation index was used to compare the affected with the unaffected hemisphere. RESULTS: The percentage of change in increased signal intensity in the area of activation ranged from 4.8% +/- 0.9 to 9.2% +/- 1.2 (mean, 5.6% +/- 1.5). The ipsilateral activation index in the affected hemisphere was 0.00 to 0.38, whereas that in the unaffected hemisphere was 15.4 to infinity. The difference in the ipsilateral activation index between each hemisphere was considered significant. CONCLUSION: Our results showed increased activation in the unaffected hemisphere in patients with schizencephaly, which may reflect functional reorganization of the motor area in patients with this congenital disorder.

Adolescent↗

PubMed1998

The stiffness of lumbar spinal motion segments with a high-intensity zone in the anulus fibrosus.

STUDY DESIGN: Biomechanical and anatomic study of human cadaveric spinal motion segments. OBJECTIVES: To measure the stiffness of spinal motion segments by disc type and by load type (flexion, extension, axial rotation, or lateral bending). To compare stiffness in motion segments with and without a high-intensity zone or radial tear in the anulus fibrosus. SUMMARY OF BACKGROUND DATA: The high-intensity zone, that is a linear zone of high-intensity on T2-weighted magnetic resonance images corresponding to a radial tear in the anulus fibrosus, is a marker for a painful disc at discography. The high-intensity zone is hypothetically associated with diminished stiffness of the motion segment. METHODS: Human cadaveric lumbar spinal motion segments with normal disc morphology or a high-intensity zone of the anulus fibrosus were selected on the basis of magnetic resonance imaging. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Rotation was measured with a kinematic system. Torque-rotation curves and stiffness were calculated for each motion segment and for each torque. The motion segments were sectioned on a cryomicrotome to verify the disc morphology as normal or as that of a radial tear. RESULTS: In four motion segments with normal discs, stiffness was greater in axial rotation (8.4 Nm/degree) than in lateral bending (2.3 Nm/degree), flexion (1.8 Nm/degree), or extension (2.6 Nm/degree). In 16 motion segments with a high-intensity zone, stiffness was 2.4 Nm/degree in axial rotation, and less severely reduced in lateral bending, flexion, and extension. Stiffness in motion segments with a high-intensity zone was significantly less with smaller than with larger axial rotation loads. CONCLUSIONS: The presence of a high-intensity zone in the intervertebral disc is associated with reduced stiffness of motion segments. The reduction is greater in axial rotation than in other torques. The reduction is more in smaller than in larger axial torques.

Aged↗

PubMed1998

Clinical and echocardiographic outcomes of aortic intramural hemorrhage compared with acute aortic dissection.

Aortic intramural hemorrhage (IMH), which presents clinical manifestations identical to those of acute aortic dissection, is different from aortic dissection in terms of the absence of intimal tear and communication of blood flow between the true and false lumen. This study was conducted for the purpose of diagnosing IMH by transesophageal echocardiography (TEE) prospectively and comparing the clinical and echocardiographic outcome of IMH with aortic dissection. Between August 1991 and November 1996, 27 IMHs and 73 acute aortic dissections were diagnosed using TEE in 202 consecutive patients with suspected aortic dissections. The TEE diagnoses of IMH and aortic dissection were initially compared with computed tomography and magnetic resonance imaging and later confirmed by operative findings (n = 37) or follow-up changes (n = 12). In the 49 patients whose diagnosis was confirmed by operation or follow-up changes, the sensitivity and specificity of TEE for the diagnosis of IMH were 27 of 27 (100%) and 20 of 22 (91%), respectively. There were 11 deaths in 73 patients (15%) from acute aortic dissection and 1 death in 27 patients (4%) from IMH during a follow-up of 1.7+/-1.5 years (p = NS). Stanford classification and types of treatment were not related to death in both groups. Complications developed less often in patients with IMH (3 of 27) than in those with acute aortic dissection (24 of 73), and no death occurred in patients with uncomplicated IMH who were medically treated. A follow-up imaging study of 12 IMH patients showed complete resolution in 8, regression in 3, and progression in 1 patient. TEE is accurate in the diagnosis of IMH and IMH has a lower incidence of complications than aortic dissection because of the absence of intimal tear and communication of blood flow in the false lumen.

Acute Disease↗