Biomedical subjects

T-Y Lee

Publications and source records attributed to T-Y Lee.

10 recordsLinked to original sources

PubMed2006

Identification of penumbra and infarct in acute ischemic stroke using computed tomography perfusion-derived blood flow and blood volume measurements.

BACKGROUND AND PURPOSE: We investigated whether computed tomography (CT) perfusion-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. METHODS: Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF <25 mL x 100 g(-1) x min(-1) that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. RESULTS: For recanalized patients, CBF was significantly lower (P<0.05) for infarct (13.3+/-3.75 mL x 100 g(-1) x min(-1)) than penumbra (25.0+/-3.82 mL x 100 g(-1) x min(-1)). CBV in the penumbra (2.15+/-0.43 mL x 100 g(-1)) was significantly higher than contralateral (1.78+/-0.30 mL x 100 g(-1)) and infarcted tissue (1.12+/-0.37 mL x 100 g(-1)). Logistic regression using an interaction term (CBFxCBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better (P<0.05) fit than CBF or CBV alone, suggesting that the CBV threshold for infarction varies with CBF. For patients without recanalization, CBF and CBV for infarcted regions were 15.1+/-5.67 mL x 100 g(-1) x min(-1) and 1.17+/-0.41 mL x 100 g(-1), respectively. CONCLUSIONS: We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.

Acute Disease↗

PubMed2006

Effects of caponization and different exogenous androgen on the bone characteristics of male chickens.

The effects of caponization and androgen implantation on the bone characteristics of male chickens were evaluated. Healthy Single Comb White Leghorn cockerels were caponized or sham operated (sham) at 12 wk old. Sixteen birds from each group were selected for a 14-wk experiment in trial 1. Sixteen birds from the sham group and 64 from the caponized group (randomly allocated into 4 treatments) were implanted with 10.4 +/- 0.4 mg (1.62-mm i.d., 3.6-mm o.d.) of cholesterol, testosterone (TES), 5alpha-dihydrotestosterone (5alpha-DHT), or 19-nortestosterone (19-NorT) and were assigned to trial 2 for a 14-wk experiment. The results from trial 1 showed that caponization increased BW (P < 0.05) and decreased tibia stress, ash content, and P content with higher blood P concentration (P < 0.05) as compared with the sham group. In trial 2, the cholesterol implantation group showed the lowest tibia breaking strength, bending moment, stress, and ash content (P < 0.05). The 19-NorT implantation group showed decreased (P < 0.05) blood Ca and P concentration but increased tibia ash and P content, reaching the same level as the sham group (P > 0.05). The adverse effects of caponization on bone characteristics could be improved using androgen implantation. Among the implantation groups, the 19-NorT implantation group showed the best improvement in tibia breaking strength and bending moment, followed by the TES and 5alpha-DHT groups. The TES group showed the best improvement in tibia stress, followed by the 19-NorT and 5alpha-DHT groups.

Animals↗

PubMed2006

Dynamic CT perfusion imaging in subarachnoid hemorrhage-related vasospasm.

BACKGROUND AND PURPOSE: Nimodipine is a therapy that reduces morbidity and mortality in patients with subarachnoid hemorrhage (SAH), though the mechanisms by which it does so are not well understood. In a rabbit model of SAH, we studied the effects of nimodipine by using functional CT imaging. We hypothesized that the nimodipine treatment group would have (1) increased mean basilar artery diameter, (2) less diminished cerebral blood flow (CBF) following vasospasm, and (3) better neurologic outcomes. METHODS: SAH was induced in 26 New Zealand White rabbits randomized to 2 groups: treated (nimodipine) or control (no treatment). CT perfusion and CT angiography were used to measure CBF and basilar artery diameter at baseline, 10, 30, and 60 minutes after SAH, and on days 3, 5, 7, 9, and 16. Neurologic assessments were performed on each day of scanning. RESULTS: Basilar artery diameter in the treated group was greater than in the control group post-SAH (P < .05). When vasospasm was >15%, CBF in the nimodipine group was significantly greater than in the control group in the brain stem, cerebellum, parieto-occipital cerebrum, and deep gray matter (P < .05). Neurologic scores in the nimodipine group were significantly better than in the control group on days 5 and 9 (P < .05). CONCLUSION: Animals treated with nimodipine showed (1) increased mean basilar artery diameter, (2) improved neurologic outcome, and (3) increased mean CBF despite no significant difference in the incidence and severity of delayed vasospasm. These data provide a basis for future studies comparing the efficacy of new treatments for SAH to that of nimodipine.

Angiography↗

PubMed2005

Reflex-mediated reduction in human cerebral blood volume.

Adrenergic nerves innervate the human cerebrovasculature, yet the functional role of neurogenic influences on cerebral hemodynamics remains speculative. In the current study, regional cerebrovascular responses to sympathoexcitatory reflexes were evaluated. In eight volunteers, contrast-enhanced computed tomography was performed at baseline, -40 mmHg lower body negative pressure (LBNP), and a cold pressor test (CPT). Cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF) were evaluated in cortical gray matter (GM), white matter (WM), and basal ganglia/thalamus (BGT) regions. Lower body negative pressure resulted in tachycardia and decreased central venous pressure while mean arterial pressure was maintained. Cold pressor test resulted in increased mean arterial pressure concomitant with tachycardia but no change in central venous pressure. Neither reflex altered end-tidal carbon dioxide. Cerebral blood volume was reduced in GM during both LBNP and CPT (P<0.05) but was unchanged in WM and BGT. Mean transit time was reduced in WM and GM during CPT (P<0.05). Cerebral blood flow was only modestly affected with either reflex (P<0.07). The combined reductions in GM CBV (approximately -25%) and MTT, both with and without any change in central venous pressure, with small CBF changes (approximately -11%), suggest that active venoconstriction contributed to the volume changes. These data demonstrate that CBV is reduced during engagement of sympathoexcitatory reflexes and that these cerebrovascular changes are heterogeneously distributed.

Adult↗

PubMed2004

Hand-assisted laparoscopic colectomy vs open colectomy: a prospective randomized study.

BACKGROUND: We compared the perioperative parameters and outcomes achieved with hand-assisted laparoscopic colectomy (HALC) vs open colectomy (OC) for the management of benign and malignant colorectal disease, including cancer patients treated with curative intent. METHODS: Sixty eligible patients were randomized to either HALC (n = 30) or OC (n = 30) treatment groups. We used Pearson's chi-square and two-sample t-tests to compare the differences in demographics and perioperative parameters. RESULTS: There were no significant differences in age, gender distribution, disease pattern, operative procedure, comorbidity, or history of abdominal surgery. The HALC patients had significantly shorter hospital stays and incision lengths, faster recovery of gastrointestinal function, less analgesic use and blood loss, and lower pain scores on postoperative days 1, 3, and 14. There were no significant differences in operative time, complications, or time to return to normal activity. CONCLUSION: Hand-assisted laparoscopic colectomy (HALC) is safe and produces better therapeutic results in terms of perioperative parameters than OC.

Adult↗

PubMed2004

Paracardiac pleural Castleman disease: radiographic and MR findings.

Castleman disease is a rare benign lymphoid tumour of uncertain aetiology that usually appears as a solitary mediastinal mass. We report a rare case of Castleman disease in the right paracardiac pleural space, occurring in a young woman with non-specific chest discomfort. MRI showed a well-defined, oval mass that was slightly hyperintense on T(1) weighted images, inhomogeneously hyperintense on T(2) and enhanced T(1) weighted images. The patient underwent radical tumour resection and has remained well for 8 years.

Adult↗

PubMed2003

Pedunculated malignant peripheral nerve-sheath tumour of the diaphragm presenting as recurrent lung infection: ultrasound diagnosis.

We report a rare case of malignant peripheral nerve-sheath tumour of the diaphragm in a 12-year-old boy with neurofibromatosis presented clinically and radiographically as recurrent lung infection. Ultrasound revealed a pedunculated diaphragmatic tumour invading the posterior chest wall. This case highlights that this unusual tumour may limit diaphragmatic excursion leading to, and even being masked by, superimposed lung infection. In patients with neurofibromatosis, ultrasound is recommended when chest radiography shows a basal lung opacity.

Child↗

PubMed2003

CT imaging of angiogenesis.

Tumor angiogenesis has significant implications in the diagnosis and treatment of various solid tumors. With the advent of fast, multi-slice CT scanners, CT imaging techniques capable of qualitative and quantitative analysis of tumor angiogenesis have been the subject of extensive investigation in the past 2 decades. The fundamental bases for CT imaging of angiogenesis are both the transport by blood flow of intravenously administered iodinated contrast material to tissue and the exchange by diffusion of these contrast molecules between the intravascular space and the extravascular interstitial space. With current fast CT scanners both tissue and vascular enhancement can be measured and traced over time at small time intervals to allow detailed modeling of the distribution of contrast agent in tissue. Both compartmental and distributed parameter models for contrast transport and exchange have been developed to quantify from the CT data the following angiogenesis related parameters: tissue blood flow, blood volume, mean transit time, contrast arrival time, capillary permeability surface area product and hepatic arterial fraction in case of the liver. This review addresses the following aspects of CT imaging of angiogenesis: 1) basic concepts related to the understanding of both compartmental and distributed parameter models; 2) comparison between both types of models; 3) practical issues with respect to the measurement of the arterial input function, which is required for the solution of both types of models; and, 4) illustration of the application of a distributed parameter model, the Johnson and Wilson model, in a number of experimental studies.

Angiography↗

PubMed2002

Small bowel obstruction due to incarcerated sciatic hernia: ultrasound diagnosis.

A 71-year-old woman presented with vomiting, abdominal pain and vague right gluteal discomfort. Abdominal ultrasound showed ascites and dilated small bowel loops with peristaltic movement, while transgluteal ultrasound revealed entrapped ascites beneath gluteal muscles and an oedematous, immobile bowel loop trapped between the sacrum and iliac bone with barely visible colour Doppler flow suggestive of an incarcerated sciatic hernia. CT demonstrated similar findings and subsequent surgery confirmed the diagnosis. To our knowledge, this is the first report of a pre-operative diagnosis of incarcerated sciatic hernia on ultrasound.

Aged↗

PubMedDate not supplied

The use of CT perfusion to monitor the effect of hypocapnia during laser thermal therapy in a rabbit model.

One of the limiting factors in the thermal therapy of tumours is the dissipation of heat by blood flow. The current study investigates the use of hyperventilation (hypocapnia) to decrease tumour blood flow during laser thermal therapy. Rabbits with implanted VX2 thigh tumours were treated using a diode laser (805 nm) as the heating source. One group of rabbits (n = 8) was treated with the new hypocapnia protocol and another group (n = 8) with the conventional (normocapnia) protocol. The mean tumour volume and blood flow were the same for the two groups prior to treatment. The laser power temporal profile (3.0-1.5 W) and the duration of treatment (60 min) were also the same for both treatment protocols. Blood flow maps were calculated from a series of contrast-enhanced CT images. The average change in thermal lesion area at 60 min post-laser thermal therapy from pre-treatment normalized to the pre-treatment tumour area was significantly different between the two treatment protocols: 0.52+/-0.13 (hypocapnia) vs 0.33+/-0.12 (normocapnia) (p < 0.001). Similarly, the average fractional decrease in global tumour blood flow 60 min post-treatment from pre-treatment was also significantly different between the two protocols: 0.64+/-0.10 (hypocapnia) vs 0.41+/-0.14 (normocapnia) (p < 0.001). The hypocapnia protocol produced larger thermal lesion area and greater decrease in tumour blood flow post-treatment than the normocapnia protocol. These results support the further investigation of the use of hypocapnia to increase the therapeutic effect of laser thermal therapy.

Animals↗