Objective:To explore the feasibility and advantages of applying visualized thermosensitive color-changing bolus in postmastectomy radiotherapy (PMRT) for breast cancer.Methods:Forty patients with breast cancer treated with PMRT in the Second Affiliated Hospital of Soochow University from June 2023 to June 2024 were prospectively selected. They were randomly divided into test and control groups (also referred to as groups A and B, respectively), with 20 patients in each group. Group A, underwent two CT scans: the first scan without bolus (image A1) and the second scan with visualized thermosensitive color-changing bolus (image A2). They were treated with visualized thermosensitive color-changing bolus. Group B also underwent two CT scans: the first scan without bolus (image B1) and the second scan with conventional commercial bolus (image B2), and then were treated with conventional commercial bolus. In the radiotherapy planning, images A1 and A2 were designed as A1-Plan and A2-Plan, and A3-Plan was created by transferring the A1-Plan onto image A2. Images B1 and B2 were designed as B1-Plan and B2-Plan, and B3-Plan was created by transferring the B1-Plan onto image B2. The radiation fields and target optimization functions were identical. The dosimetric differences and skin toxicity reactions between different plans were compared.Results:In Group A, A1-Plan and A2-Plan manifested no statistically significant differences ( P > 0.05) in the doses to organs at risk (OARs), including the ipsilateral lung ( V5 Gy, V10 Gy, V20 Gy), heart ( Dmean), contralateral breast ( Dmean), and skin ( Dmax and Dmean), target homogeneity index (HI), conformity index (CI), prescription dose volume ( V50 Gy), depth of maximum dose ( Dmax), and monitor unit (MU). In Group B, B3-Plan compared to B1-Plan showed reduced V50 Gy (89.9% vs. 95%), HI (0.153 vs. 0.136), and CI (0.817 vs. 0.810), while the two plans displayed no statistically significant differences in doses to OARs. In contrast, A3-Plan and B3-Plan exhibited statistically significant differences ( t = 2.78, 2.29, -0.47, 0.51, 3.13, P < 0.05) in V50 Gy (94.05% vs. 89.90%), Dmax (5 665.4 cGy vs. 5 632.7 cGy), HI (0.148 vs. 0.163), CI (0.83 vs. 0.82), and skin Dmean (5 153.6 cGy vs. 5 048.2 cGy). Compared to the conventional commercial bolus of the same thickness, the visualized thermosensitive color-changing bolus yielded a significantly reduced air cavity volume (3 833 mm 3vs. 21 498 mm 3,t = -9.65, P < 0.05). Both groups experienced only grade I skin toxicity reactions. Conclusions:Compared to the conventional commercial bolus of the same thickness, the visualized thermosensitive color-changing bolus shows a more effective dosimetric distribution in terms of target coverage, HI, and CI, a higher fit to the skin, highly visualized air cavity, and higher positional repeatability in fractionated radiotherapy, demonstrating high practicality and safety.

Objective:To explore the feasibility and advantages of applying visualized thermosensitive color-changing bolus in postmastectomy radiotherapy (PMRT) for breast cancer.Methods:Forty patients with breast cancer treated with PMRT in the Second Affiliated Hospital of Soochow University from June 2023 to June 2024 were prospectively selected. They were randomly divided into test and control groups (also referred to as groups A and B, respectively), with 20 patients in each group. Group A, underwent two CT scans: the first scan without bolus (image A1) and the second scan with visualized thermosensitive color-changing bolus (image A2). They were treated with visualized thermosensitive color-changing bolus. Group B also underwent two CT scans: the first scan without bolus (image B1) and the second scan with conventional commercial bolus (image B2), and then were treated with conventional commercial bolus. In the radiotherapy planning, images A1 and A2 were designed as A1-Plan and A2-Plan, and A3-Plan was created by transferring the A1-Plan onto image A2. Images B1 and B2 were designed as B1-Plan and B2-Plan, and B3-Plan was created by transferring the B1-Plan onto image B2. The radiation fields and target optimization functions were identical. The dosimetric differences and skin toxicity reactions between different plans were compared.Results:In Group A, A1-Plan and A2-Plan manifested no statistically significant differences ( P > 0.05) in the doses to organs at risk (OARs), including the ipsilateral lung ( V5 Gy, V10 Gy, V20 Gy), heart ( Dmean), contralateral breast ( Dmean), and skin ( Dmax and Dmean), target homogeneity index (HI), conformity index (CI), prescription dose volume ( V50 Gy), depth of maximum dose ( Dmax), and monitor unit (MU). In Group B, B3-Plan compared to B1-Plan showed reduced V50 Gy (89.9% vs. 95%), HI (0.153 vs. 0.136), and CI (0.817 vs. 0.810), while the two plans displayed no statistically significant differences in doses to OARs. In contrast, A3-Plan and B3-Plan exhibited statistically significant differences ( t = 2.78, 2.29, -0.47, 0.51, 3.13, P < 0.05) in V50 Gy (94.05% vs. 89.90%), Dmax (5 665.4 cGy vs. 5 632.7 cGy), HI (0.148 vs. 0.163), CI (0.83 vs. 0.82), and skin Dmean (5 153.6 cGy vs. 5 048.2 cGy). Compared to the conventional commercial bolus of the same thickness, the visualized thermosensitive color-changing bolus yielded a significantly reduced air cavity volume (3 833 mm 3vs. 21 498 mm 3,t = -9.65, P < 0.05). Both groups experienced only grade I skin toxicity reactions. Conclusions:Compared to the conventional commercial bolus of the same thickness, the visualized thermosensitive color-changing bolus shows a more effective dosimetric distribution in terms of target coverage, HI, and CI, a higher fit to the skin, highly visualized air cavity, and higher positional repeatability in fractionated radiotherapy, demonstrating high practicality and safety.

Objective:To evaluate the dose calculation accuracy of cone-beam CT (CBCT) image by actual measurement method.Methods:CBCT images of 60 patients in the Second Affiliated Hospital of Soochow University from September, 2021 to May, 2022 were retrospectively analyzed. CBCT images of full-fan and half-fan scanning of the head, half-fan scanning of the chest and pelvis were obtained by the Varian OBI system. Hounsfield unit - electron density (HU-ED) curves corresponding to the scanning conditions were established with CIRS electron density phantom. The radiotherapy plans were designed on the CBCT images, and the dose calculation results of the detection point were compared with the ionization chamber measurement results to analyze the dose error. Then, three-dimensional dose verification system was adopted to detect the accuracy of the CBCT image radiotherapy plans implementation process in 60 patients, and the accuracy of dose calculation was verified according to the D 99%, D mean, D 1% of target volume, D mean and D 1% of organs at risk (OAR), and the γ pass rate. Results:In point dose detection in phantom, the dose calculation errors of CBCT images in the above four scanning patterns were -1.06%±0.87%、-1.67%±0.86%, 0.91%±0.73%, -1.54%±0.90%, respectively. In dosimetric verification based on patients' CBCT image treatment plan, the mean difference of D mean, D 99%, and D 1% of planning target volume (PTV) in all scanning modes were not higher than 2%, and the D mean and D 1% differences of other OAR were not higher than 3%, except for the lens of patients in the head. The average γ values of target volume and OAR were less than 0.5 under the criteria of 3%/2 mm. Conclusions:Under the condition of correctly establishing HU-ED curves, intensity-modulated radiation therapy (IMRT) / volumetric-modulated arc therapy (VMAT) planning based on CBCT images can be employed to estimate and monitor the actual dose to target volume and OAR in adaptive radiotherapy. Full-fan scanning patterns can further improve the accuracy of dose calculation for the head of patients.

Objective:To understand the normative status of physical dose description in domestic radiobiology studies through literature study.Methods:According to the scoring system recommended by the National Cancer Institute (NCI) and Desrosiers et al, evaluate (full Score: 10 points) the normalization of physical dosimetry description in the radiobiology-related articles published in two important journals, Chinese Journal of Radiation Oncology and Chinese Journal of Radiological Medicine and Protection, in past 5 years.Results:A total of 222 relevant articles from these two journals were included, and a median score of 5.0 was evaluated. Among them, 72.1% of the literatures scored 4.0-7.0 points, 68.0% of the literatures scored ≤5.5 points, and 18.5% scored ≤3.0 points. 90.1% and 97.7% of the literatures described " the type of ray" and " absorbed dose" , with the highest average score (0.90 and 0.98 points) respectively. The lowest average score of " dosimetry calibration" was 0 point.Conclusions:Although the most of literatures described " the type of ray" and " absorbed dose" , most other details of dosimetric parameters were not reported. Therefore, there is a deficiency in the standardized description of physical dosimetry in domestic radiobiology literatures, which may affect the reproducibility and interpretability of research result.

Objective: To evaluate and predict the pelvic dose by analyzing two pelvic contour definitions and identify the influencing factors of the pelvic dose in postoperative IMRT for cervical cancer, aiming to provide reference for postoperative pelvis-sparing IMRT for cervical cancer. Methods: Sixty cervical cancer patients receiving postoperative IMRT with unrestricted pelvic dose were selected. Two sets of pelvic contours (pelvic anatomy and pelvic Mell) were delineated as per the anatomical and Mell methods. The dose relationship between two methods was analyzed after redesigning the treatment plan by limiting dose of pelvic anatomy. The correlation analysis was performed by Pearson’s correlation method. The factors affecting the pelvic anatomy dose were identified by Logistic multivariate regression analysis and a dose prediction model was subsequently established. Results: The volumes of pelvic anatomy and pelvic Mell were 925.82 cm³ and 1141.20 cm³(P=0.000). There was a significant correlation between them (r>0.622, P=0.000). The dose of pelvic anatomy was significantly higher than that of pelvic Mell. The relationship of V₁₀, V₂₀ and V₃₀ between them was y=-8+ 1.01x, y=-13+ 1.05x and y=-4+ 0.9x, respectively. The dose limits of pelvic Mell recommended by literatures(V₁₀<90%, V₂₀<75%, V₃₀<60%) were translated into V₁₀<97%, V₂₀<83% and V₃₀<70%, respectively. The pelvic anatomy dose was significantly reduced after dose limiting. The V₁₀, V₂₀, V₃₀ and D_mean were significantly decreased by 3.64%, 12.69%, 12.02% and 6.93%(P=0.000, 0.000, 0.000), respectively. Multivariate analysis showed that the overlapping volume of pelvic anatomy within PTV was an independent influencing factor of pelvic anatomy dose (P<0.05). Patients with a relative overlapping volume of less than 18% could easily meet the dose limiting requirement. Conclusions Both two pelvic contour definitions can be applied in postoperative pelvis-sparing IMRT for cervical cancer. Use of pelvic dose limiting can significantly reduce the IMRT dose. The overlapping volume of the pelvis within PTV is an independent influencing factor of pelvic dose. Patients whose overlapping volume within the PTV relative to pelvis is less than 18% can easily meet the dose limiting requirement.

Objective To reduce the risk of radiation-induced cardiac injury in patients with left breast cancer after breast-conserving surgery by multileaf collimator (MLC) shielding technique.Methods A total of 18 patients with left breast cancer after breast conserving surgery were selected to obtain 3DCT and 4DCT images at free breathing state.The target area was identified on the 3DCT image by registration with 4DCT images and to develop a hybrid intensity-modulated treatment plan (H_IMRT) and a heart sparing hybrid intensity-modulated treatment plan (HSH_IMRT) to introduce MLC shielding technology to reduce the cardiac exposure dose,and to perform dosimetry verification of the treatment plan by using the Compass verification system.The prescription dose was 50 Gy in 25 fractions.The dosimetry parameters of the target area and the organs at risk were compared between the two treatment plans and the dose verification result.Results The result of the treatment plan showed that compared with H_IMRT,the dose uniformity of the target area of HSH_IMRT was better,and the difference of conformability was not statistically significant (P＞0.05).The mean dose of the whole heart decreased by 23.67％ (t =13.693,P＜0.05) compared with the former.Dmax and D of other substructures of the heart were lower than the former.The result of dose verification showed that there was no statistically significant difference in uniformity and conformity between the two planned target doses (P＞ 0.05).The mean dose of the whole heart of HSH_IMRT was 24.88％ (t =13.782,P＜0.05) lower than that of H_IMRT,and except for the left ventricle and right ventricle,the Dmax of other heart substructures and D of all heart substructures decreased.Both the planned and the dose verification result showed that the V20 and the D of the affected lung were lower in HSH_IMRT.Conclusions Reasonable introduction of MLC shielding technology in H_IMRT can reduce the exposure dose of cardiac and further reduce the risk of radiation damage in heart.

Objective To assess the protective effect of low melting point lead and field margin on the opposite testicular in testicular seminoma patients during postoperative radiation.Methods A patient with stage Ⅰ seminoma was selected and his phantom measurement was carried out.The PTW 0.6 cm3 type ionization chamber was used to measure the absorbed dose under the conditions of no lead and low melting point lead with thickness of 3,5,7,10 and 15 mm at different distances from the field edge,respectively.Results Under different lead thickness conditions,the measurement result and the distance between the measured points and the boundary of the field were exponentially attenuated.The relative target dose dropped from 8.41％ at 1 cm to 0.61％ at 25 cm without lead blocking,and dropped from 4.55％,3.98％ and 3.47％ at 1 cm to0.27％,0.21％ and0.17％ at 25 cm with 3,5,7 cmlead,respectively.With 10 mm lead,it dropped from 2.55％ at 1.5 cm to0.15％ at25 cm,and 1.86％ at2 cm to0.13％ at 25 cm with 15 mm lead.The lead shield of 3,7 and 15 mm thickness can be used to reduce the scatter dose of testis to below 0.5 Gy during radiotherapy for seminoma.Conclusions An appropriate thickness of low melting point lead might reduce the dose of testis conveniently and effectively,which would be beneficial to protect the fertility of the patients with testicular seminoma.

Objective To compare the dose volume and normal tissue complication probability (NTCP) of small intestine between intensity-modulated radiotherapy (IMRT) with dose constraints to the peritoneal space (PS) and the bowel loop (BL) in the treatment of rectal cancer,and to investigate the feasibility of placing a dose constraint to the PS instead of the BL in protection of the small intestine.Methods A total of 24 patients with rectal cancer undergoing postoperative adjuvant radiotherapy were enrolled as subjects.In the 24 patients,12 were treated in supine position an.d 12 in prone position.The weekly computed tomography (CT) scans from pre-treatment to weeks 1-4 of treatment were defined as Plan,1 W,2 W,3 W,and 4 W.Contours of PS and BL were delineated on all CT images.Based on the Plan CT images,two IMRT plans,PPS and PBL,were designed with dose constraints to the PS and BL,respectively.The method was applied to 1-4 W CT images.For each CT scan,the dose volume and NTCP of the small intestine were evaluated in PPs and PBL.Results A total of 109 sets of CT images were acquired from 24 patients,and 218 plans were designed and copied.The median volume of the PS and BL was 1339.28 and 250.27 cm3,respectively.For the Plan CT scans,V15 values of the PS in PPs plan and the BL in PBL plan were 918.96 and 199.57 em3,respectively.For all CT scans,the dose volume of the small intestine in PPs,in most cases,was lower than that in PBL,while V15 values in Ps and PBL were 170.07 and 178.58 cm3 (P=0.000).The dose volume of the small intestine was correlated with V15 (P=0.000).PPs had significantly lower NTCP of chronic and acute adverse reactions than PBL(2.80％ vs.3.00％,P=0.018;57.32％ vs.58.64％,P=0.000).In patients with prone and supine treatment positions,most of the dose volume and NTCP of the small intestine in Ps were significantly lower than those in PBL(P＜0.05 for V10,V15,V30,and NTCP of acute adverse reactions).Conclusions It is feasible to place a dose constraint to the PS instead of the BL for protection of the small intestine during IMRT for rectal cancer.V15＜830 cm3 can be referred to as the objective function of dose restraint.

Objective To investigate the impact of actual gantry angle on the accuracy of intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods A total of 27 patients with NPC were enrolled in this study. IMRT plans were designed with Pinnacle treatment planning system (TPS),and 8 beams with an interval of 30°(within 0°-360°) were selected for each plan. These plans were divided into plan A and plan B according to the beam parameters. In plan A,the minimum sub-field area was 5 cm2 ,the minimum number of sub-field monitor unit ( MU) was 5,and the maximum sub-field number was 80;in plan B,the minimum sub-field area was 8 cm2 ,the minimum number of sub-field MUs was 8,and the maximum sub-field number was 60.The gamma passing rate using the criteria of 3%/3 mm and 2%/2 mm at actual and zero degree gantry angles were calculated using Mapcheck 2 device for dose verification,and were compared with the paired t-test. The relationship between the above differences (Δ value) and the beam angle or the beam parameters was also analyzed. Results In plan A with the criteria of 3%/3 mm, the beams were significantly different (P=0000-0007) except for at angles of 270°,300°,and 300°,and the mean Δ value was 090%;under the criteria of 2%/2 mm,all beams were significantly different ( P=0000-0019) except for at an angle of 300°,and the meanΔvalue was 272%.In plan B with the criteria of 3%/3 mm,the beams showed no significant difference ( P=0052-0639) except for at an angle of 300 ° ,and the mean Δ value was 040%;under the criteria of 2%/2 mm,all beams showed no significant difference ( P>005) except for at angles of 210°,240°,270°,and 300°,and the meanΔvalue was 152%.When the plan B parameters were used, the Δ value was reduced;the results of two verification methods were more consistent,so the accuracy was also improved. Conclusions Compared with the validation method at zero degree gantry angle,the validation method at an actual gantry angle is associated with reduced gamma passing rate because of some factors such as gravity,which is not significantly related to the beam angle,but the beam parameters. In the design of IMRT plans for NPC,the total number of sub-fields should be decreased as far as possible,and the minimum sub-field area and the minimum number of MU should be increased, so as to improve the accuracy of treatment plans.

Objective To evaluate the uncertainty of the small bowel dose?volume and the normal tissue complication probability (NTCP) during intensity?modulated radiotherapy (IMRT) for rectal cancer, and to provide a reference for the dose limit and protection of the small bowel during IMRT for rectal cancer. Methods A total of 20 patients with rectal cancer who received postoperative adjuvant radiotherapy from March 2014 to August 2015 were enrolled in this study, including 10 patients receiving CT scan in the supine position and 10 patients in the prone position. All patients received computed tomography ( CT) scan before the treatment and at weeks 1, 2, 3, and 4 of treatment, and they were defined as Plan, 1W, 2W, 3W, and 4W CT groups, respectively. The small bowel loop ( BL ) and peritoneal space ( PS ) were delineated on the images. The IMRT plan based on the Plan CT was copied to the 1W, 2W, 3W, and 4W CT groups, and then the small bowel dose?volume and NTCP were assessed for all CT groups. The paired t?test was used for comparison between groups. The Pearson method was used to analyze the correlation between NTCPC(chronic NTCP) and dose?volume. Results A total of 89 CT images of 20 patients were obtained. In all the patients, the volumes of BL and PS were 25121 cm3 and 132416 cm3 , respectively, and the shift% was 2315% and 1134%, respectively. The V15 of BL and PS was 18486 cm3 and 79245 cm3 , respectively, and the shift% was 3169% and 370%, respectively. The V30 of BL and PS was 8801 cm3 and 64573 cm3 , respectively, and the shift% was 3766% and 1049%, respectively. The V15 of BL in 35% of patients and V15 of PS in 20% of patients, the Dmax of BL in 50% of patients, and the NTCP of 15% of patients in the course of treatment exceeded the safety limits. The 1?4W CT groups had a significantly higher NTCPC than the Plan CT group (402% vs. 320%, P=0104), and their SD% was 4168%. There was a significant correlation between NTCPC and V30?V50 of BL (R>0400, P=0000). The NTCPA ( acute NTCP ) and NTCP C in the supine position were significantly higher than those in the prone position ( 6230% vs. 5674%, P=0061;488% vs. 322%, P=0145 ) . Conclusions Small bowel motility leads to an uncertainty of the adverse event assessment during IMRT for rectal cancer. The change in BL is significantly larger than that in PS and the change in BL and PS in the supine position is significantly larger than that in the prone position. Using the prone position and minimizing V15 and V30 when designing the treatment plan can reduce the NTCP A and NTCP C in the small bowel.