RESUMEN
Since the application of image-guided radiotherapy in clinical practice, cone-beam CT (CBCT) has become the most widely employed image-guided device. However, some problems remain to be cautioned in the application of CBCT, such as certain errors in the setup errors before and after the correction of CBCT, the failure of CBCT to correct dynamic changes, whether the influence of application frequency of CBCT on patients’ boundary of clinical target volume can be reduced, imaging conditions of CBCT lack of a certain degree of flexibility, and the effect of clinical value and application cost on the practicality of CBCT. Only by fully understanding the problems in CBCT application can CBCT be applied more reasonably and scientifically.
RESUMEN
Objective Image-guided radiation therapy(IGRT)was performed to investigate the intrafractional body motion and identify the relevant influencing factors during hypofractionated radiotherapy for malignant pulmonary tumors. Methods A total of ninety-six patients with malignant pulmonary tumors receiving hypofractionated radiotherapy in Jiangsu Cancer Hospital were enrolled in this clinical trial. The kilo-voltage cone beam CT(kV-CBCT)was acquired prior to each fraction and matched to the planning CT images to correct the set-up errors. CBCT was performed immediately after the end of treatment to evaluate the intrafractional variation in the mediolateral,anteroposterior and craniocaudal dimensions.The relationship between relevant influencing factors and intrafractional variation was analyzed using multivariate linear regression. Results In the anteroposterior and craniocaudal directions,the intrafractional positioning errors were reduced along with the increase of ordinal number of fraction(P= 0.000). In the mediolateral direction, the intrafractional positioning errors were increased along with the longer duration of hypofractionated radiotherapy(P=0.010).The intrafractional positioning errors were decreased over larger body weight(P=0.003).The intrafractional positioning errors were significantly increased when vacuum bag and thermoplastic film were utilized for fixation(P= 0.009). Conclusions Certain intrafractional positioning errors occur during hypofractionated radiotherapy. Relevant influencing factors differ in different directions. Relevant influencing factors should be modified to reduce intrafractional positioning variation and improve the treatment accuracy.
RESUMEN
Stereotactic body radiation therapy (SBRT) adopts different tumor-killing mechanisms from the conventional fractionated radiotherapy.In SBRT,a single high-dose radiation can destroy the membrane of tumor cells and induce the release of tumor-associated antigen,also named in situ tumor vaccine,which stimulates the immune system to kill the residual tumor;a single-fraction radiation with a dose larger than 8-10 Gy can induce rapid apoptosis of vascular endothelial cells via the acid sphingomyelinase pathway at 1-6 hours after radiation,which causes tumor vascular occlusion and secondary tumor-killing effects.In order to understand whether SBRT improves the clinical treatment outcomes via the above mechanisms,this paper reviews the clinical research advances in SBRT for primary liver cancer.
RESUMEN
Response evaluation criteria in solid tumors is widely used for assessing tumor response to radiotherapy in clinical practice.However,it is clearly insufficient.Currently there is no ideal method for early evaluation of tumor radiation response.This paper reviews studies on early evaluation of radiotherapy efficacy by positron emission tomography-computed tomography (CT),magnetic resonance imaging,and CT.This paper also further explores the necessity and feasibility of CT values of megavoltage CT scans in early evaluation of the radiosensitivity of tumor during tomotherapy.