ABSTRACT
Intensity-modulated radiotherapy (IMRT) is gradually replacing conventional radiation therapy and has become the mainstream radical treatment for patients with nasopharyngeal carcinoma (NPC). IMRT can conform and increase radiation doses to tu-mor-associated regions as well as decrease exposure doses and volumes on normal organs and tissues to avoid damage on critical or-gans. Aside from system and setup errors, other factors, such as the gradual reduction of the primary NPC lesion and the decrease in vol-ume of involved neck lymph nodes as well as body weight loss and changes in the head and neck shape during IMRT, may cause devia-tions in the radiation doses and volume delivered to the NPC targets and the organs at risk. These factors may affect the accuracy of IMRT. Several researchers have attempted to correct such deviations during IMRT for NPC patients by using adaptive radiotherapy (ART). The results indicate that ART is feasible to a certain degree and can correct the deviations, including decrease in tumor volume, body weight loss, and changes in head and neck shape of NPC patients.
ABSTRACT
ObjectiveTo study the CT values of certain phantoms scanned by various CT scanners with dissimilar parameters.Methods The CT values of tissue equivalent inserts was measured in the TM164 and CIRS-062 phantom scanned by TOSHIBA AQUILIONTM,SIEMENS SOMATOMTMSENSATIONTM 64 and SIEMENS SOMATOMTM SENSATIONTM OPEN with different voltages,currents and slice thicknesses and then the corresponding CT-to-density curves was compared. Results There are no significant differences of CT values with various currents and slice thicknesses and also for low atom number materials scanned by different scanners with various tube voltages.The CT values of high atom number materials have obvious differences scanned with tube voltage,the maximum is about 400 HU.There are also significant differences between CT-density curves of two phantoms in the range from soft tissues to dense bone,the maximum is up to 500 HU.ConclusionsCT-density curves were highly affected by materials of phantoms,scanners and tube voltages.It is necessary to measure the curve with a comfortable phantom and certain scanner to assure the accuracy for dose calculation for treatment planning system.
ABSTRACT
Objective:To study the effect of Ginkgo biloba extract (EGb761) on metabolism of aflatoxin B_1(AFB_1) in Wistar rats. Methods:Seventy one Wistar rats were divided into three groups at random: group A (AFB_1 group), group B (AFB_1+EGb761 group), and group C (control group). The rats in groups A and B were given AFB_1(intraperitoneal injection, 100-200 μg/ kg body weight, 1-3 times/week). The rats in group B were fed the food containing EGb761 while the rats in groups A and C were given normal food. Blood samples were collected and liver biopsy was performed on the 14th, 28th and 42nd week. All the rats were sacrificed at the 64th week. The incidence of hepatoma was observed. The hepatic phase Ⅰ drug-metabolizing enzyme CYP450 and phase Ⅱ enzyme GST were detected by spectrometry. The serum AFB_1-lysine adduct was determined by high performance liquid chromatography (HPLC). The expression of 8-hydroxydeoxyguanosine(8-OHdG) was measured by immunohistochemistry. Results:The incidence of hepatocellular carcinoma (HCC) in group B was significantly lower than that in group A (26.92% vs 76.00%,P<0.001). No hepatocellular carcinoma developed in group C. EGb761 had no effects on the activities of CYP450 and GST in rat liver tissues. The level of AFB_1-lysine adduct reached the peak (4 356.01 pg/mg albumin) at the 14th week in group A. EGb761 significantly inhibited the formation of AFB_1-lysine adducts in serum by 13.07% at the 14th week (P＝0.033), and 73.63% at the 42nd week (P＝0.002). The expression of 8-OHdG protein in rat liver tissues in group B was significantly lower than that in group A at the 28th, 42nd, and 64th week (P<0.05). Conclusion:The main mechanism underlying the effect of EGb761 in blocking hepatogenesis induced by AFB_1 may not be fully related with its influence on the activity of liver phase Ⅰ and phase Ⅱ metabolizing enzymes. EGb761 inhibites the production of AFB_1-lysine addcuts, decreases the expression of 8-OHdG protein, and finally alleviates the DNA oxidative injury, which may be one of the mechanisms for the effects of EGb761 in inhibiting or delaying hepatogenesis induced by AFB_1.
ABSTRACT
Objective To provide a better cell model of closely nature infectious state for further research of hepatitis B virus(HBV). Methods Primary tupaia hepatocytes were isolated by the two-step perfusion method. The hepatocytes were then infected with purified serum from patients with hepatitis B. DNA and RNA isolated from the hepatocytes were detected with Southern blot and Northern blot. HBsAg in supernatant was tested by immunohistochemical method. Results cccDNA, pgRNA and sgRNA could be detected by Southern blot and Northem blot, and strong signals could be seen from day 7 to day 14 post-in-fection. The S/CO value of HBsAg in supernatant decreased from day 1 to day 5 and then increased after 5 day. Conclusion Primary tupaia hepatocytes are competent for infection with HBV. HBV can stably repli-cate and express in HBV-infected tupaia hepatocytes.