ABSTRACT
Objective:To compare the effects of two methods of marking surface landmarks on the patient’s positional stability when using a multifunctional body board in combination with thermoplastics to fix the abdominal and pelvic areas for radiotherapy patients.Methods:50 subjects who underwent positional fixation using a multifunctional body board in combination with thermoplastics from August 2022 to January 2023. The subjects were divided into two groups, A and B, with 25 cases each, according to the different methods of body surface marking. In group A, landmarks were marked on the body surface on the top edge of the thermoplastics. In group B, three sets of surface landmarks were marked on the patient’s body according to the laser line on the projection of the patient’s body surface when the thermoplastics were completed. Manual registration is performed using L3 to L5 as the main registration targets. The pre-treatment CBCT image is used to analyze the first-time positioning pass rate, setup errors in the x-, y-, and z-axis directions, and the distribution of positive and negative setup errors in both groups of patients. Results:The pass rates of the first-time positioning of patients in Groups A and B were 76.9% and 86.1%, respectively, which met the clinical requirements. Group B had a better first-time positioning pass rate than group A, and the difference between the two groups was statistically significant ( P < 0.05). The pendulum errors of group B were smaller than those of group A in both the x-axis and y-axis (all P < 0.05), and the difference between the two groups in terms of the pendulum errors in the z-axis direction was not statistically significant (all P > 0.05). The difference in the frequency distribution of the pendulum error in the positive and negative directions of the x- and z-axis between the two groups was not statistically significant (all P > 0.05). The difference in the frequency of distribution of the pendulum error in the positive and negative directions of the y-axis between the two groups was statistically significant ( P < 0.05). Conclusions:The proposed two methods of surface landmark marking are generally in line with the positioning requirements for conventional fractionation radiotherapy for abdominal and pelvic patients. Using a laser line on the projection of the patient’s body surface for three sets of surface landmark markings produces smaller setup errors and is better than using the top edge of the thermoplastics for surface landmark markings, improving the positional stability of abdominal and pelvic patients.
ABSTRACT
Objective To analyze the precision and stability of optical surface imaging system for patients who received radiotherapy with active breath control. Methods Eighteen radiotherapy patients with lung metastasis were managed by active breath control (ABC).The difference error detected by optical surface imaging system and CBCT were defined as the precision of optical surface imaging system. The variation among the error of optical surface imaging positioning the value of correction of treatment position and the error detected by optical surface imaging again were defined as the stability of optical surface imaging system. Intrafractional errors were analyzed by optical surface imaging system through whole treatment process (including breath hold and free breath). Results The optical surface imaging system had precision (systematic (Σ) and random errors (σ)) of 1.78/3.42 mm 2.54/6.57 mm and 2.79/3.22 mm respectively and stability of2.12/2.54 mm 3. 09/4.02 mm and 1.37/3.55 mm respectively in lateral-medial superior-inferior and anterior-posterior directions. The intrafractional errors (Σ and σ) were 0.42/0.85 mm 0.41/1.47 mm and 0.41/1.47 mm respectively for breath hold duration and 4.76/4.16 mm 6.54/7.78 mm and 3.13/5.92 mm for free breath duration in lateral-medial superior-inferior and anterior-posterior directions. Conclusions As an effective method for validate breath hold;Optical surface imaging system can improve the precision and safety of active breath control. However,the factors that affect the accuracy and stability of the optical surface imaging system in patients undergoing radiotherapy with ABC are not clear;it cannot replace the CBCT for positioning verification.
ABSTRACT
Independent check is one of the key measures of quality control (QC) in radiotherapy and is essential for the assurance of radiotherapy accuracy.In recent years,with the application of computer-aided system,the automaticity of independent check,as well as its accuracy and efficiency,increases.Meanwhile,QC has evolved from a device-centered to a process-centered program.Therefore,independent check has been increasingly systematic and specific.This review gives a brief summary of the implementation and development of independent check.
ABSTRACT
Objective To investigate the difference of lung and target volume and dosimetry characteristics features of deep inhalation breathing holding-active breathing control (ABC) and the four dimensional CT (4D-CT) free breathing in stereotactic body radiation therapy (SBRT) technology for patients with lung cancer.Methods 10 patients with pulmonary malignant tumor who were proposed SBRT treatment were selected,and received CT under free breath (FB-CT),4D-CT scan under quiet respiration (4D-CT) and active breathing control CT scan (ABC-CT),respectively.With SBRT technology under the same condition designed four corresponding plans,FB-CT,ABC-CT,4D-CT and 4D-CT0 which was the end inspiratory phase of 4D-CT respectively.The lung volume(V),PTV,V5,V20,mean lung dose(MLD) and normal tissue complication probability(NTCP) of four treatment programs were counted and compared.Results Compared with FB-CT,V,PTV,V5,V20,MLD and NTCP of ABC-CT were 51.48％,-65.34％,-42.64％,-56.62％,-40.22％ and-98.53％ (t=-7.14 to6.16,P＜0.05);PTV,V5,V20,MLD and NTCP of 4D-CT were-40.14％,-16.90％,-37.16％,-17.85％ and-90.96％ (t =0.54 to 3.22,P＜0.05);PTV,V5,V20,MLD and NTCP of 4D-CT0 were-68.98％,-30.21％,-48.49％,-37.45％ and-95.82％ (t=1.32 to 5.46,P＜0.05),respectively.Compared with FB-CT,the lung volume of 4D-CT and 4D-CT0 had no statistical difference (P ＞ 0.05).Conclusions ABC-CT methods have ideal clinical characteristics,with larger double lung volume,smaller artifacts of image,and higher target matching precision.ABC-CT methods reduce the dose of normal lung tissues significantly.