Biomedical subjects

Lizhong Liu

Publications and source records attributed to Lizhong Liu.

9 recordsLinked to original sources

PubMed2006

How many signals impinge on GLUT4 activation by insulin?

GLUT4 is the main glucose transporter activated by insulin in skeletal muscle cells and adipocytes. GLUT4 storage vesicles (GSVs) traffic in endocytic and exocytic compartments. In the basal state, GLUT4 compartments are preferentially sequestered in perinuclear deposits wherein stimuli including insulin and non-insulin factors can increase GLUT4 vesicle formation, its exocytosis, and fusion to plasma membrane. In addition to well-established effectors of insulin signaling pathway, such as PKCzeta and Akt, the cytoskeletal network is implicated in GLUT4 translocation. This review will discuss the mechanisms and activation of GLUT4 trafficking and incorporating to PM from three aspects: known molecules of the insulin signaling pathway; Rho and Rab family proteins and cytoskeletal molecules.

Animals↗

PubMed2006

Adjuvant high dose rate brachytherapy in the management of soft tissue sarcoma: a dose-toxicity analysis.

OBJECTIVES: Although brachytherapy has been used in the management of soft tissue sarcoma for decades, there is little published data regarding dose and toxicity. We performed an interim analysis of our high dose-rate experience to establish dosing guidelines. METHODS: We analyzed our first 12 soft tissue sarcoma patients treated with high dose-rate brachytherapy as tumor bed boost (in conjunction with beam therapy), seeking an association between treatment factors and wound-healing complications. In the process of our analysis, we devised a dosimetric method to retrospectively quantify delivered dose. Our findings were used to formulate dosing guidelines; the first 5 cases treated along these guidelines are also presented. RESULTS: Despite the small number of cases, we were able to demonstrate a correlation (P < 0.01) between wound healing and brachytherapy dose (fractional or total biologically equivalent dose). We found no relationship between wound healing and patient age, diabetes, width of excised skin, cross-sectional area of implant, sequencing of therapy, or surgery-to-brachytherapy interval. CONCLUSION: There appears to be a relationship between dose and disturbed wound healing that should be respected to avoid unnecessary toxicity. An objective technique for defining target volume and quantifying dose is proposed for meaningful analysis of dose/effect relationships.

Brachytherapy↗

PubMed2005

[Compare the differences between automatic analysis and manual analysis of apnea events in polysomnogram].

OBJECTIVE: To investigate whether there are differences on the diagnose of sleep apnea hypopnea syndrome between automatic analysis and manual analysis of respiration events in polysomnogram. METHOD: Sixty snoring human was selected randomly and monitored separately by sleep monitor in seven hour at night, sleep monitor would produce a poly sonogram, firstly polysomnogram was analysis by the software of sleep monitor and then by the manual operation. Finally data were processed by statistical analysis. RESULT: There were significant differences between automatic analysis and manual analysis of polysomnogram on apnea hypopnea index,apnea index, hypopnea index and long apnea. Data of manual analysis were more consistent with clinic symptoms of patients than automatic analysis. CONCLUSION: The result of automatic analysis of polysomnogram had a deviation to the diagnosis of pathogenetic, in order to improve the accuracy of clinic diagnosis, polysomnogram should be analysis by manual operation generally.

Adult↗

PubMed2005

[Pathological and ultrastructural observation on the epithelia of nasal cavity and nasal sinuses in chronic sinusitis and nasal polyps after endoscopic sinus surgery].

OBJECTIVE: To research the restoration characteristics of epithelia in nasal cavity and nasal sinuses with chronic sinusitis and nasal polyps after endoscopic sinus surgery,and to provide basis for improving the treatment after operation. METHOD: Twenty patients with chronic sinusitis and nasal polyps after endoscopic sinus surgery were observed. The "Vesicle tissues" situated ostiomeatal complex (OMC) were observed with light and transmission electron microscopy after operation of 7-14 days. RESULT: (1) The "Vesicle tissues" were off white or buff, some contained liquid, and some were parenchyma under the endoscopy. (2) The epithelia of "Vesicle tissues" were pseudostratified ciliated columnar epithelium (16/20), and some were stratified squamous epithelium (2/20), some were squamous metaplasia in pseudostratified ciliated columnar epithelium (2/20). Lamina propria were edema. Inflammation cells infiltrated epithelial lining and subepithelial lining. We found mucous gland, mixed gland and glandular duct under subepithelial lining,and small vascular ectasia under light microscopy. (3) Transmission electron microscope: epithelia were pseudostratified ciliated columnar epithelium, cilia were in good order, microvilli located between cilia. The cross section of majority cilia were 9 + 2 form microtubule, but in some cilia we could not find microtubule and could only find one central microtubule. Golgi complex were up growth, and endoplasmic reticulum expand, and multi-mitochondrion were coagulation degeneration in epithelial cells. Some mitochondrion were 1-2 degree swelling and the lysosome increased. Inflammation cells infiltrated epithelial lining. Majority were neutrophil and lymphocyte, but we also found eosinophil and plasmacyte. CONCLUSION: "Vesicle tissues" is the manifestation of active epithelia regeneration in nasal cavity and nasal sinuses after endoscopic sinus surgery, it's the earlier period of imbalance regeneration of the epithelization in postoperative cavity. "Vesicle tissues" is similar to the nasal polyp histopathology, and it is phenomena of limited pathological rebuilding in earlier period. Cleaning "Vesicle tissues" can effectively control the nasal polyps relapse and impel the postoperative cavity to epithelization.

Adult↗

PubMed2004

A dwell position verification method for high dose rate brachytherapy.

Misplacement of dwell positions is a potential source of misadministration in high dose rate brachytherapy. In this work we present a dwell position verification method using fluoroscopic images. A mobile C-arm fluoroscopic machine is used to take a snapshot of the treatment machine's check cable as it reaches the most distal dwell position. This fluoroscopic image is displayed side-by-side with a treatment planning image on a dual monitor relay station at the HDR treatment console. Any discrepancy between the check cable's position on the verification image and the intended dwell position on the planning image can be identified immediately, thus avoiding the possibility of treating the wrong target volume.

Brachytherapy↗

PubMed2004

Determination of 137Cs dosimetry parameters according to the AAPM TG-43 formalism.

Traditional treatment planning systems calculate dose distributions around 137Cs intracavitary sources by interpolating stored dose rate tables or by Sievert-type integrals. Some of the recently introduced planning systems, such as the Varian BrachyVision and Eclipse (Varian Medical Systems, Palo Alto, CA), have discontinued the use of tables and have implemented instead the AAPM TG-43 formalism as a brachytherapy dosimetry calculation algorithm. In this work we present the dosimetry parameters for 137Cs intracavitary sources as determined according to the TG-43 formalism. With the availability of the TG-43 parameters, the commissioning of a 137Cs source in any current brachytherapy planning system is a straightforward task for a clinical physicist.

Algorithms↗

PubMed2003

The linear-quadratic model and fractionated stereotactic radiotherapy.

PURPOSE: To determine the dose per fraction that could be used when gamma knife or linear accelerator-based stereotactic treatments are delivered in 2 or more fractions. METHODS AND MATERIALS: The linear-quadratic (LQ) model was used to calculate the dose per fraction for a multiple-fraction regimen which is biologically equivalent to a given single-fraction treatment. The results are summarized in lookup tables. RESULTS AND CONCLUSION: The tables can be used by practicing clinicians as a guide in planning fractionated treatment. For the large doses used in typical stereotactic treatments and for small fraction numbers, the model is not very sensitive to the value of the alpha/beta ratio in the LQ model. A simple rule of thumb is found that for two-fraction and three-fraction treatments the dose per fraction is roughly two-thirds and one-half of the single-fraction treatment dose, respectively.

Linear Models↗

PubMed2003

Evaluation of two water-equivalent phantom materials for output calibration of photon and electron beams.

Two commercially available water-equivalent solid phantom materials were evaluated for output calibration in both photon (6-15 MV) and electron (6-20 MeV) beams. The solid water 457 and virtual water materials have the same chemical composition but differ in manufacturing process and density. A Farmer-type ionization chamber was used for measuring the output of the photon beams at 5- and 10-cm depth and electron beams at maximum buildup depth in the solid phantoms and in natural water. The water-equivalency correction factor for the solid materials is defined as the ratio of the chamber reading in natural water to that in the solid at the same linear depth. For photon beams, the correction factor was found to be independent of depth and was 0.987 and 0.993 for 6- and 15-MV beams, respectively, for solid water. For virtual water, the corresponding correction factors were 0.993 and 0.998 for 6- and 15-MV beams, respectively. For electron beams, the correction factors ranged from 1.013 to 1.007 for energies of 6 to 20 MeV for both solid materials. This indicated that the water-equivalency of these materials is within +/- 1.3%, making them suitable substitutes for natural water in both photon and electron beam output measurements over a wide energy range. These correction factors are slightly larger than the manufacturers' advertised values (+/- 1.0% for solid water and +/- 0.5% for virtual water). We suggest that these corrections are large enough in most cases and should be applied in the calculation of beam outputs.

Electrons↗

PubMed2003

On the use of C-arm fluoroscopy for treatment planning in high dose rate brachytherapy.

Treatment planning for brachytherapy requires the acquisition of geometrical information of the implant applicator and the patient anatomy. This is typically done using a simulator or a computed tomography scanner. In this study, we present a different method by which orthogonal images from a C-arm fluoroscopic machine is used for high dose rate brachytherapy treatment planning. A typical C-arm is not isocentric, and it does not have the mechanical accuracy of a simulator. One solution is to place a reconstruction box with fiducial markers around the patient. However, with the limited clearance of the C-arm this method is very cumbersome to use, and is not suitable for all patients and implant sites. A different approach is adopted in our study. First, the C-arm movements are limited to three directions only between the two orthogonal images: the C-orbital rotation, the vertical column, and the horizontal arm directions. The amounts of the two linear movements and the geometric parameters of the C-arm orbit are used to calculate the location of the crossing point of the two beams and thus the magnification factors of the two images. Second, the fluoroscopic images from the C-arm workstation are transferred in DICOM format to the planning computer through a local area network. Distortions in the fluoroscopic images, with its major component the "pincushion" effect, are numerically removed using a software program developed in house, which employs a seven-parameter polynomial filter. The overall reconstruction accuracy using this method is found to be 2 mm. This filmless process reduces the overall time needed for treatment planning, and greatly improves the workflow for high dose rate brachytherapy procedures. Since its commissioning nearly three years ago, this system has been used extensively at our institution for endobronchial, intracavitary, and interstitial brachytherapy planning with satisfactory results.

Artifacts↗