ABSTRACT
Objective To evaluate the volume of left ventricle (LV) based on PET-CT in left-sided breast cancer patients treated with adjuvant radiotherapy. To assess the impact of dose and volume in interrelations for heart and cardiac sub-structures using dose-volume histograms. Methods From October 2008 to February 2009, 14 patients with post-operatively confirmed left-sided breast cancer were enrolled in this study. Patients were scanned using contrast enhanced CT for simulation and FDG PET-CT have been applied to display the structure of left ventricle in each patient before radiotherapy (RT). The LV has been delineated based on PET-CT. Other critical sub-structures, such as left anterior descending coronary artery (LAD) have been contoured in each patient. The six-field simple intensity modulated radiotherapy (slMRT)technique has been created in all patients. Results The mean volumes of left ventricle based on PET-CT (LV-PET) were 112. 931 cm3. The volume of LV receiving ≥50% prescription dose highly correlated with the volume of heart receiving ≥50% prescription dose (R = 0. 869, P = 0. 000). There was less correlation between the volume of LAD and the volume of heart receiving ≥ 50% prescription dose ( R = 0. 220, P =0. 440). Conclusions The left ventricle could be delineated efficiently based on imaging of PET-CT. The volume of LV receiving higher dose in RT has high correlation with the volume of heart using sIMRT technique. It may pave the way for further exploring radiation induced cardiac injury in patients with breast cancer.
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Objective To investigate whether the change of beam set-up methods will influence the dosimetric quality of intensity modulated radiation therapy (IMRT) for non-small cell lung cancer (NSCLC).Methods Twenty-one stage Ⅰ-Ⅲ NSCLC patients were selected for this study.The technique of step and shoot was used and three different beam set-up methods were chosen for IMRT planning,including IMRT-7 with nine equal-spaced beams angled 0°,51°,102°,153°,204°,255°and 306°; IMRT-5 with five equal-spaced beams angled 0°,72°,144°,216°and 288°; and IMRT-5m which was created from IMRT-7 but excluded 2 fields (51°and 102° were omitted if there was lesion in the right lung,while 255°and 306° were excluded if there was lesion in the left lung).The dose constrains ofnormal lungs for IMRT were set according to V5-V60 of normal lungs obtained from the same patient's actually treated 3D-CRT dose volume histogram.The prescription dose for IMRT started from 65 Gy,and then escalated or decreased step by step by 2 Gy once a time until the best plan was obtained.Results For normal lung dose,IMRT-5m had lower V5-V25 than the other two groups; but there was no significant difference in V30-V40.IMRT-5 was the worst for V45-V60; and mean lung dose was lowest in IMRT-5m.Dose parameters of esophagus and spinal cord,target conformity index,and total monitor units were all similar among difference plans.IMRT-5m had lowest heart V40 compared to the other two groups.For target heterogeneity index,IMRT-5 was higher than IMRT-7,but there were no significant differences among IMRT-5m,IMRT-5 and IMRT-7.Compared to 3D-CRT,the prescription dose could be increased by (5.1 ±4.6) Gy for IMRT-7,(3.1 ±5.3) Gy for IMRT-5,and (5.5 ±4.8)Gy for IMRT-5m.Conclusion Fewer beams and modified beam angles could result in similar,even better plan quality.
ABSTRACT
SCLC can spare more volume of the normal lungs and e-sophagus, and has the ability of dose escalation.
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Purpose:To investigate the possibilities of three-dimensional conformal radiotherapy (3DCRT) in treating the patients with recurrent nasopharyngeal carcinoma;and planning optimization,dosimetry analysis for recurrent disease in different sites.Methods:Three patients with recurrent disease in posterior area of styloid process、cavernous sinus and with maximum volume were analysed. Comparison was made for optimized 3DCRT treatment planning with different number of beams and angles of incidences.Results:It is possible to significantly improve the dose coverage to target volume and the dose to critical organ was under the tolerance dose.Conclusions:3DCRT may be a suitable alternative to conventional therapy in patients with recurrent nasopharyngeal carcinoma.