Objective To investigate the impact of immobilization devices and treatment couches on the planned dose in stereotactic body radiation therapy(SBRT).Methods A retrospective study was conducted involving 23 SBRT patients,all of whom underwent CT simulation with foam padding or vacuum bag immobilization.For each patient,two sets of contours were outlined on CT images:one encompassing only the patient's skin(Body),and the other including the skin plus immobilization devices(BodyF).Initially,a reference plan(noFC)meeting clinical requirements was generated based on the Body contour.Without altering the plan(noFC)parameters and field setups,plan calculations were performed separately based on three different contours:BodyF(with immobi-lization devices only),Body+C(with treatment couch only),and BodyF+C(with both immobilization devices and treatment couch),yielding plan(F),plan(C),and plan(FC),respectively.By comparing the target and skin dose parameters across these four plans,the effects of immobilization devices and treatment couches on the planned dose were evaluated.Results Compared to plans based solely on the patient's skin contour,plans incorporating immobilization devices showed reduced high-dose,prescription dose coverage,and average dose in the target volume.Notably,the difference in the percentage of the planning target volume(PTV)receiving 105%of the prescribed dose(PTV/V105%p(%))between plan(FC)and plan(noFC)could reach 61.86%.Conversely,plans with immobilization devices increased both the maximum and average skin doses.Specifically,the dose to 10 cc of skin within 2 mm of the surface(body 2 mm/D 10 cc(Gy))showed a 21.36%difference between plan(FC)and plan(noFC).For all target and skin parameters,no statistically significant differences were observed between plan(C)and plan(noFC).Among plans with immobilization devices,the minimum distance from the target to the skin correlated inversely with skin dose,indicating greater impact on skin dose with closer proximity.Conclusions Immobilization devices in SBRT lead to beam attenuation and altered build-up effects,significantly reducing target dose parameters while increasing skin dose.The closer the target is to the skin,the greater the impact of immobiliza-tion devices on skin dose.It is recommended to incorporate immobilization devices into the contour design during radiotherapy planning.

Objective To conduct a comprehensive review on application status and future development prospects of proton therapy for pediatric medulloblastoma.Methods A total of 218 literatures were retrieved from PubMed and CNKI database using the search terms"pediatric medulloblastoma,proton therapy,radiotherapy"(English)and"儿童髓母细胞瘤,质子治疗,放射治疗"(Chinese),with a publication timeframe from January 1,2004,to June 1,2025.Inclusion criteria were as follow:(1)proton therapy for pediatric medulloblastoma;(2)radiotherapy for pediatric medulloblastoma;(3)proton therapy for pediatric brain tumors;(4)development and applications of proton therapy.Exclusion criteria were as follow:(1)outdated literatures;(2)redundant or highly similar studies.After screening,89 literatures met the inclusion criteria.Results Compared with conventional treatments such as surgery,photon therapy,and chemotherapy,proton therapy for pediatric medulloblastoma significantly reduced acute toxicity and long-term side effects including cognitive dysfunction,endocrine disorders,and hearing loss.Additionally,proton therapy exhibited favorable cost-effectiveness.In the future,the therapeutic outcomes would be further enhanced through the optimization of proton therapy techniques,treatment planning,and equipment.Conclusion With ongoing technological advancements and growing clinical experience,proton therapy is expected to become one of the standard treatment modalities for pediatric medulloblastoma.

Objective To investigate the impact of immobilization devices and treatment couches on the planned dose in stereotactic body radiation therapy(SBRT).Methods A retrospective study was conducted involving 23 SBRT patients,all of whom underwent CT simulation with foam padding or vacuum bag immobilization.For each patient,two sets of contours were outlined on CT images:one encompassing only the patient's skin(Body),and the other including the skin plus immobilization devices(BodyF).Initially,a reference plan(noFC)meeting clinical requirements was generated based on the Body contour.Without altering the plan(noFC)parameters and field setups,plan calculations were performed separately based on three different contours:BodyF(with immobi-lization devices only),Body+C(with treatment couch only),and BodyF+C(with both immobilization devices and treatment couch),yielding plan(F),plan(C),and plan(FC),respectively.By comparing the target and skin dose parameters across these four plans,the effects of immobilization devices and treatment couches on the planned dose were evaluated.Results Compared to plans based solely on the patient's skin contour,plans incorporating immobilization devices showed reduced high-dose,prescription dose coverage,and average dose in the target volume.Notably,the difference in the percentage of the planning target volume(PTV)receiving 105%of the prescribed dose(PTV/V105%p(%))between plan(FC)and plan(noFC)could reach 61.86%.Conversely,plans with immobilization devices increased both the maximum and average skin doses.Specifically,the dose to 10 cc of skin within 2 mm of the surface(body 2 mm/D 10 cc(Gy))showed a 21.36%difference between plan(FC)and plan(noFC).For all target and skin parameters,no statistically significant differences were observed between plan(C)and plan(noFC).Among plans with immobilization devices,the minimum distance from the target to the skin correlated inversely with skin dose,indicating greater impact on skin dose with closer proximity.Conclusions Immobilization devices in SBRT lead to beam attenuation and altered build-up effects,significantly reducing target dose parameters while increasing skin dose.The closer the target is to the skin,the greater the impact of immobiliza-tion devices on skin dose.It is recommended to incorporate immobilization devices into the contour design during radiotherapy planning.

Objective To conduct a comprehensive review on application status and future development prospects of proton therapy for pediatric medulloblastoma.Methods A total of 218 literatures were retrieved from PubMed and CNKI database using the search terms"pediatric medulloblastoma,proton therapy,radiotherapy"(English)and"儿童髓母细胞瘤,质子治疗,放射治疗"(Chinese),with a publication timeframe from January 1,2004,to June 1,2025.Inclusion criteria were as follow:(1)proton therapy for pediatric medulloblastoma;(2)radiotherapy for pediatric medulloblastoma;(3)proton therapy for pediatric brain tumors;(4)development and applications of proton therapy.Exclusion criteria were as follow:(1)outdated literatures;(2)redundant or highly similar studies.After screening,89 literatures met the inclusion criteria.Results Compared with conventional treatments such as surgery,photon therapy,and chemotherapy,proton therapy for pediatric medulloblastoma significantly reduced acute toxicity and long-term side effects including cognitive dysfunction,endocrine disorders,and hearing loss.Additionally,proton therapy exhibited favorable cost-effectiveness.In the future,the therapeutic outcomes would be further enhanced through the optimization of proton therapy techniques,treatment planning,and equipment.Conclusion With ongoing technological advancements and growing clinical experience,proton therapy is expected to become one of the standard treatment modalities for pediatric medulloblastoma.

Objective:To effectively quantify and evaluate the quality of different deformation registration algorithms, in order to enhance the possibility of implementing deformation registration in clinical practice.Methods:The Jacobian determinant mean (JDM) is proposed based on the Jacobian determinant (JD) of displacement vector field (DVF), and the Jacobian determinant error (DJDE) is introduced by incorporating the JD of the inverse DVF. The optical flow method (OF-DIR) and fast demons method with elastic regularization (FD-DIR) were tested on nasopharyngeal and lung cancer datasets. Finally, JDM and DJDE with the Jacobian determinant negative percentage (JDNP), inverse consistency error (ICE) and normalized mean square error (NMSE) were used to evaluate the registration algorithms and compare the differences evaluation indicators in different tumor images and different algorithms, and the receiver operating curve (ROC) was analyzed in evaluation.Results:In lung cancer, OF-DIR outperformed FD-DIR in terms of JDM, NMSE, DJDE and ICE, and the difference was statistically significant( z = -2.24, -4.84, t = 4.01, 6.54, P<0.05). In nasopharyngeal carcinoma, DJDE, ICE and NMSE of OF-DIR were superior to FD-DIR, and the difference was statistically significant ( t = 4.46, -7.49, z = -2.22, P<0.05), but there was no significant difference in JDM ( P>0.05). In lung cancer and nasopharyngeal carcinoma, JDNP of OF-DIR was worse than that of FD-DIR, and the difference was statistically significant ( z = -4.29, -4.02, P<0.01). In addition, DJDE is more specific and sensitive on ROC curve (AUC=0.77), and has different performance result for tumor images at different sites. Conclusions:The JDM and DJDE evaluation metrics proposed are effective for deformation registration algorithms. OF-DIR is suitable for both lung cancer and nasopharyngeal carcinoma, while the influence of organ motion on the registration effect should be considered when using FD-DIR.

Objective:To investigate the necessity of adaptive re-planning during radiotherapy for nasopharyngeal carcinoma (NPC) and its impact on dose improvement.Methods:Clinical data of 89 NPC patients admitted to Sun Yat-sen University Cancer Center from July 2014 to December 2017 were retrospectively analyzed. All patients received 25+7 rounds of adaptive re-planning during radiotherapy. Plan-A was defined as the initial CT scan-based 25-fraction radiotherapy plan, while plan-B was defined as the re-planned 7-fraction radiotherapy plan based on a subsequent CT scan. The changes in the target and parotid gland volumes were compared between plan-A and plan-B. Plan-I was a one-time simulation of plan-A extended to 32 fraction radiotherapy plan, and plan-II was generated through registration and fusion of the plan-A and plan-B for adaptive re-planning. The differences in dose metrics, homogeneity index (HI), conformity index (CI), and dose to organs at risk (OAR) were compared between plan-I and plan-II. Statistical analysis was performed by using paired t-test. Results:Compared with plan-A, the gross tumor volume of massive bleeding lesions (GTV nx) and parotid gland volume of plan-B were decreased by 13.14% and 11.12%, respectively (both P<0.001). While planning clinical target volume of metastatic lymph nodes (PCTV nd) of plan-B was increased by 7.75%( P<0.001). There were significant changes in the lymph nodes of plan-A and plan-B. The D mean, D 5%, D 95% of massive bleeding lesions planning target volume (PTV nx) and D 5% of high risk planning target volume (PTV1) in plan-II were all significantly higher than those in plan-I (all P<0.05). The CI of PTV nx and PTV1 in plan-II was closer to 1 than that in plan-I. In all assessed OAR, the D mean, D 50%, and D max of plan-II were significantly lower than those of plan-I (all P<0.05). Conclusions:During radiotherapy, NPC patients may experience varying degrees of primary tumor shrinkage, parotid gland atrophy, and lymph node changes. It is necessary to deliver re-planning and significantly improve the dose of target areas and OAR.

Objective:To analyze the clinically acceptable and reproducible bladder and rectum volumes of prostate cancer patients during radiotherapy under bladder and bowel preparation, aiming to provide quantitative indicators for bowel and bladder preparation before and after radiotherapy.Methods:Clinical data of 275 prostate cancer patients with strict bladder and bowel preparation and completion of whole course radical radiotherapy at Sun Yat-sen University Cancer Center from April 2015 to December 2020 were retrospectively analyzed. Patients were scanned with cone beam CT (CBCT) before each treatment and the setup error was recorded. Sixty-six patients were selected by simple random sampling and the bladder and rectum on daily CBCT was outlined using MIM software. The relationship between the ratio of daily bladder or rectum volume to the planned bladder or rectum volume (relative value of volume) and setup error was analyzed. Quantitative data were expressed as mean±SD. Normally distributed data were analyzed by paired t-test while non-normally distributed data were assessed by Kruskal-Wallis test.Results:The bladder and rectum volume on planning CT were (370.87±110.04) ml and (59.94±25.07) ml of 275 patients. The bladder and rectum volumes on planning CT were (357.51±107.38) ml and (65.28±35.37) ml respectively of the 66 selected patients with 1611 sets of CBCT images. And the bladder and rectum volumes on daily CBCT were (258.96±120.23) ml and (59.95 ± 30.40) ml. The bladder volume of patients was decreased by 3.59 ml per day on average during the treatment and 0.37 ml for the rectum volume. According to the bladder volume on planning CT, all patients were divided into three groups: <250 ml, 250-450 ml and >450 ml groups. The relative value of volume in the 250-450 ml group during the course of radiotherapy was the smallest. And the setup error in the superior and inferior (SI) direction was (0.28±0.24) cm and (0.19±0.17) cm in the left and right (LR) direction, significantly lower than those in the other two groups (both P≤0.027). According to the rectum volume on planning CT, all patients were divided into four groups: <50 ml, 50-<80 ml, 80-120 ml and >120 ml groups. The <50 ml group had the smallest relative value of volume during radiotherapy, and the setup error in the SI direction was (0.26±0.22) cm and (0.24±0.22) cm in the anterior and posterior (AP) direction, significantly smaller than those in the other groups (both P≤0.003). The setup errors in the SI, LR, AP directions of the enrolled 66 patients were (0.30±0.25) cm, (0.20±0.18) cm and (0.28±0.27) cm, respectively. Among them, the relative value of bladder volume in the AP direction was (0.73±0.37) in the setup error <0.3 cm group, which was statistically different from those in the setup error 0.3-0.5 cm and >0.5 cm groups (both P<0.05). Conclusion:Under the bladder and bowel preparation before planning CT, the appropriate bladder and rectum volumes are in the range of 250-450 ml and <50 ml, which yields higher reproducibility and smaller setup error.

OBJECTIVE: To identify the problems in clinical radiotherapy planning for cervical cancer through quantitative evaluation of the radiotherapy plans to improve the quality of the plans and the radiotherapy process. METHODS: We selected the clinically approved and administered radiotherapy plans for 227 cervical cancer patients undergoing external radiotherapy at Sun Yat-sen University Cancer Center from May, 2019 to January, 2022. These plans were transferred from the treatment planning system to the Plan IQ^TM workstation. The plan quality metrics were determined based on the guidelines of ICRU83 report, the GEC-ESTRO Working Group, and the clinical requirements of our center and were approved by a senior clinician. The problems in the radiotherapy plans were summarized and documented, and those with low scores were re-planned and the differences were analyzed. RESULTS: We identified several problems in the 277 plans by quantitative evaluation. Inappropriate target volume selection (with scores < 60) in terms of GTV, PGTV (CI) and PGTV (V_{66 Gy}) was found in 10.6%, 65.2%, and 1% of the plans, respectively; and the PGTV (CI), GTV, and PCTV (D_98%, HI) had a score of 0 in 0.4%, 10.1%, 0.4%, 0.4% of the plans, respectively. The problems in the organs at risk (OARs) involved mainly the intestines (the rectum, small intestine, and colon), found in 20.7% of the plans, and in occasional cases, the rectum, small intestine, colon, kidney, and the femoral head had a score of 0. Senior planners showed significantly better performance than junior planners in PGTV (V_{60 Gy}, D_98%), PCTV (CI), and CTV (D_98%) (P≤0.046) especially in terms of spinal cord and small intestine protection (P≤0.034). The bowel (the rectum, small intestine and colon) dose was significantly lower in the prone plans than supine plans (P < 0.05), and targets coverage all met clinical requirements. Twenty radiotherapy plans with low scores were selected for re-planning. The re-planned plans had significantly higher GTV (D_min) and PTV (V_{45 Gy}, D_98%) (P < 0.05) with significantly reduced doses of the small intestines (V_{40 Gy} vs V_{30 Gy}), the colon (V_{40 Gy} vs V_{30 Gy}), and the bladder (D_35%) (P < 0.05). CONCLUSION Quantitative evaluation of the radiotherapy plans can not only improve the quality of radiotherapy plan, but also facilitate risk management of the radiotherapy process.
Humans ; Female ; Uterine Cervical Neoplasms/radiotherapy* ; Rectum ; Colon ; Kidney ; Organs at Risk

Objective:To analyze the dosimetric differences of volumetric modulated arc therapy (VMAT) plans for lung cancer caused by different dose calculation algorithms and radiation field settings and thus to provide a reference for designing clinical VMAT plans for lung cancer.Methods:This study randomly selected 20 patients with lung cancer and divided them into four groups of VMAT plans, namely, a group adopting two fields and two arcs based on the AAA algorithm (2F2A_AAA), a group employing two fields and two arcs based on the AXB algorithm (2F2A_AXB), a group using two fields and two arcs based on the MC algorithm (2F2A_MC), and a group adopting one field and two arcs based on the MC algorithm (1F2A_MC). Then, this study evaluated the target coverage, high-dose control, dose homogeneity index (HI), conformity index (CI), and organs at risk (OARs) of the plans using different algorithms and radiation field settings.Results:The planning target volume (PTV) results of two fields combined with two arcs (2F2A) of three groups using different algorithms are as follows. 2F2A_MC achieved better results in both D1% and V 95% (the relative volume of the target volume surrounded by 95% of the prescribed dose) of planning gross target volume (PGTV) than 2F2A_AAA (D1%: t=-2.44, P=0.03; V95%:z=-2.04, P=0.04) and 2F2A_AXB (D1%: t=2.34, P=0.03; z=-3.21, P < 0.01). 2F2A_AXB outperformed 2F2A_AAA ( z=-3.66, P < 0.01) and was comparable to 2F2A_MC in terms of the CI of PGTV. Regarding OARs, 2F2A_AXB and 2F2A_MC decreased the V5 Gy of the whole lung by 0.68% ( z=-2.69, P=0.01) and 3.05% ( z=-3.52, P < 0.01), respectively compared to 2F2A_AAA. 2F2A_AXB achieved a whole-lung Dmean of 1776.44 cGy, which was superior to that of 2F2A_MC ( t=2.67, P=0.02) and 2F2A_AAA ( t=8.62, P < 0.01). Compared to 2F2A_AAA and 2F2A_MC, 2F2A_AXB decreased the V20 Gy of Body_5 mm by 1.45% ( z=-3.88, P < 0.01) and 2.01% ( z=-3.66, P < 0.01), respectively. The results of the two groups with different field settings showed that 1F2A_MC was superior to 2F2A_MC in both the CI of PTV1 and the HI of PTV2 (CI: t=2.61, P=0.02; HI: z=-2.20, P=0.03). Moreover, 1F2A_MC increased the Dmean of the whole lung by 26.29 cGy compared to 2F2A_MC ( t=2.28, P=0.04). Conclusions:Regarding the design of VMAT plans for lung cancer, the MC algorithm is suitable for the target priority and the AXB algorithm is suitable for the OAR priority. When only the MC algorithm is available, it is recommended to choose 1F2A in the case of target priority and select 2F2A in the case of OAR priority.

Objective:To provide evidence for the selection of fixation devices and CTV to PTV margins (M ptv) in precision radiotherapy for pelvic tumors by analyzing three fixation devices in precision radiotherapy for prostate cancer. Methods:From April 2015 to December 2020, 133 prostate cancer patients treated with pelvic drainage area irradiation in our center were retrospectively analyzed. The patients were fixed with 1.2m vacuum bag (n=39), 1.8m vacuum bag (n=44) and personalized prone plate by our center (n=50). Each patient was asked to complete our bowel and bladder preparation process before positioning and radiotherapy. The registration of CBCT to planned CT before each treatment adopted the same registration box and algorithm. Setup errors in the SI, LR and AP directions under qualified bowel and bladder conditions were recorded. Setup errors in three directions under three fixation devices and corresponding M ptv values were analyzed. The correlation between setup errors with age and body mass index (BMI) was analyzed. Results:Analysis of 3333 setup errors data showed: in the SI and LR directions, the mean setup errors of 1.2m vacuum bag (3.26mm, 2.34mm) were greater than those of 1.8m vacuum bag (2.51mm, P<0.001; 1.90mm, P<0.001), and personalized prone plate (3.07mm, P=0.066; 2.10 mm, P=0.009). In the AP direction, the mean setup errors of 1.2m vacuum bag (supine)(2.20mm) were smaller than those of 1.8m vacuum bag (3.33mm, P<0.001) and personalized prone plate (3.61mm, P<0.001). The setup errors of 1.8m vacuum bag in all directions were smaller than those of personalized prone plate (P≤0.028). According to Van Herk's expansion formula, the M ptv of 1.2m vacuum bag in three directions was approximately 4 mm. The M ptv of 1.8m vacuum bag and personalized prone plate in the SI and LR directions was approximately 3 mm, and more than 5 mm in the AP direction. The setup errors were not correlated with age or BMI. Conclusions:From the setup errors results of three devices, 1.8m vacuum bag is the best, followed by personalized prone plate. And supine position is better than prone position in the AP direction.