Neck contour changes and relevant factors in nasopharyngeal carcinoma patients treated with helical tomotherapy / 中华放射肿瘤学杂志

Objective:To study the change pattern of neck diameter and relevant factors in nasopharyngeal carcinoma (NPC) patients treated with helical tomotherapy, aiming to provide reference for clinical practice.Methods:Fifteen NPC patients treated with helical tomotherapy at Sun Yat-Sen University Cancer Center from November 2020 to February 2021 were enrolled in this study. The transverse diameters of NPC patients' neck contours and body weight of all patients during radiotherapy were recorded weekly. We used descriptive statistics to explore the distribution of transverse diameters of NPC patients' neck contours during radiotherapy. And Spearman correlation analysis was used to assess the association between weight loss and changes in neck contour transverse diameter.Results:During radiotherapy, the distribution of transverse diameters of NPC patients' neck contours was completely different from the initial values. Specifically, the transverse diameters were significantly reduced at the 4th week of the radiotherapy. Moreover, the reduction of transverse diameter of neck contour was highly correlated with the weight loss ( r=0.803, P<0.05), and moderately correlated with gender ( r=0.523, P<0.05). However, there was no statistical correlation between the alteration of neck diameter and age, TNM stage, and the mean dose of GTV nd-L, GTV nd-R, PTV nd-L and PTV nd-R (all P>0.05). Conclusions:The neck contours of NPC patients are altered regularly during helical tomotherapy, which are narrowed the most obviously in the 4th week. Extensive attention should be paid to the changes of neck contour during radiotherapy in clinical practice.

Results of radiotherapy in squamous cell laryngeal cancer: A tomotherapy center experience

Background: Laryngeal cancer is a common type of head and neck cancer (HNC). Radiotherapy (RT) is a mainstay for curative treatment. Intensity-modulated RT (IMRT) is a standard technique today, as it provides of higher survival and local control and lower normal tissue toxicity. One of IMRT devices is helical tomotherapy (HT). The HT treatment results of HNC patients have been reported in few studies. We aimed to investigate the results of squamous cell laryngeal carcinoma patients treated with helical tomotherapy. Methods: Forty-five laryngeal cancer patients were selected according to the inclusion criteria. Radiotherapy (RT) plans were set in the Hi-Art HT planning system. Image-gated RT (IGRT) technique was used. Appropriate patients received simultaneous cisplatin. Treatment response rates were evaluated at the post-RT third and sixth months. Survival times were calculated with the Kaplan–Meier method. The factors affecting the treatment results were evaluated using Log-rank and Cox regression tests. A P value of less than 0.05 was accepted as statistically significant. Results: The median age was 65 (28–84) years. The median symptom duration was 6 (1–60) months. The RT dose for the early and the locally advanced disease was median 63 Gy (60.75–66) and 66 Gy (60–70), respectively. The RT interruption was median two (0-20) days. The patients were followed up to 25 (1–45) months. Grade 2 xerostomia and dysphagia rates were 55% and 7%, respectively. The 3-year estimates of overall survival (OS), disease-free survival (DFS), metastasis-free survival (DMFS), and locoregional recurrence-free survival (RRFS) were 71.7%, 60.4%, 84.9%, and 68.5%, respectively. In univariate analysis, the presence of N2 disease was a negative prognostic for DFS (P = 0.05) and DMFS (P = 0.003). RT interruption >2 days was a negative prognostic for OS (P = 0.005), DFS (P = 0.02), and RRFS (P = 0.023). In the multivariate analysis, symptom duration >6 months was found to be the only significant factor for DFS (P < 0.05). Conclusion: Intensity-modulated radiation with HT achieved comparable clinical outcomes with acceptable toxicity in laryngeal carcinoma.

Application of helical tomotherapy in the treatment of synchronous bilateral breast cancer / 中华放射医学与防护杂志

Objective:To study the differences in the dosimetry and delivery time between helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) in postoperative radiotherapy of synchronous bilateral breast cancer (SBBC) and to explore the feasibility of clinical application of the HT technology.Methods:A retrospective analysis was conducted for nine SBBC patients who underwent modified radical postoperative radiotherapy in the Fourth Affiliated Hospital of Guangxi Medical University from February 2017 to May 2022. For each patient, the Precision planning system was used to formulate the HT plan, and the RayStation planning system was employed to develop the VMAT plan. All plans obtained were divided into HT group and VMAT group according to plan type. The paired sample t-test was used to compare the dosimetric parameters of the target volume and organ at risk (OAR) and delivery time between the two radiotherapy technologies. Results:The plans of both groups could meet the clinical treatment requirements. The coverage ( D95% and V100%), conformity index (CI), average dose ( Dmean), and median dose ( D50%) of the target volumes in the HT group were better than those in the VMAT group, and the differences were statistically significant ( t=-3.21, -3.39, -5.03, 3.76, 4.97, P < 0.05). The differences in the maximum dose ( D2%), minimum dose ( D98%), high dose volumes ( V107% and V110%), and homogeneity index (HI) of the target volumes between the two groups were not statistically significant ( P > 0.05). Regarding the OAR, the V20 and Dmean of both lungs in the HT group were significantly lower than those in the VMAT group, but the irradiation volume V5 of both lungs in the HT group was significantly higher than that in the VMAT group ( t=-3.01, 3.83, -2.81, P < 0.05). Moreover, V20, V30, V40, and Dmean of heart and the V20 and Dmean of liver in the HT group were significantly lower than those in the VMAT group, with statistically significant differences ( t=3.76, -2.83, -2.74, 5.93, 4.57, 4.48, P < 0.05). There was no significant difference in the radiation doses to other OARs (spinal cord, thyroid gland, and humerus head, P > 0.05). The delivery time of the HT group was significantly higher than that of the VMAT group ( t = 11.32, P < 0.05). Conclusions:Compared with VMAT, HT has greater dosimetric advantages, and can provide higher target coverage, conformability and average dose, and significantly reduce the overall radiation doses to both lungs, heart, and liver in OARs. However, the irradiation volume V5 at low-dose areas of both lungs and the delivery time in the HT group are higher than those in the VMAT group, but still meet the clinical treatment requirements. Therefore, it is feasible to apply the HT technology to the modified radical postoperative radiotherapy of SBBC.

Application of deformable image registration in radiotherapy dose accumulation of helical tomotherapy combined with brachytherapy for cervical cancer / 中华放射肿瘤学杂志

Objective:To assess the feasibility of deformable image registration (DIR) in evaluating cumulative dose distribution of bladder and rectum of cervical cancer patients during helical tomotherapy (HT)-based intensity-modulated radiotherapy (IMRT) and high-dose-rate(HDR) brachytherapy.Methods:Clinical data of 18 patients were retrospectively analyzed. Cumulative bladder/rectum D 2cm 3 and high-risk clinical target volume (HR-CTV) D 90% parameters were calculated and compared to two direct parameter-adding methods with two registration-adding methods. Equivalent uniform dose (EUD group) and overlapping high dose (OHD group) methods were employed as parameter-adding methods. The registration-adding methods including rigid image registration (RIR group) and deformable image registration (DIR group) were adopted based on a commercial image registration software (MIM Maestro ?). The dice similarity coefficient (DSC) and mean distance to agreement (MDA) were measured to assess the accuracy of RIR and DIR. Results:In the EUD, OHD, RIR and DIR groups, the cumulative doses of bladder/rectum D 2cm 3 and HR-CTV D 90% were (80.11±3.59) Gy (EQD 2Gy), (82.23±3.46) Gy (EQD 2Gy), (80.99±6.01) Gy (EQD 2Gy) and (81.19±3.11) Gy (EQD 2Gy)( P=0.516); (72.90±3.58) Gy (EQD 2Gy), (73.83±4.28) Gy (EQD 2Gy), (72.45±6.05) Gy (EQD 2Gy) and (71.98±2.89) Gy (EQD 2Gy)( P=0.625), and (85.51±2.91) Gy (EQD 2Gy), (87.65±3.46) Gy (EQD 2Gy), (81.53±3.63) Gy (EQD 2Gy) and (85.81±3.30) Gy (EQD 2Gy)( P<0.001), respectively. The mean DSC of the bladder, rectum and HR-CTV were 0.69, 0.65 and 0.63 with RIR; and 0.85, 0.81 and 0.78 with DIR ( P<0.001), respectively. In DIR, the average MDA of bladder, rectum, and HR-CTV were 2.88, 2.48 and 2.66 mm, respectively. Conclusions:The cumulative DVH parameters among 4 groups show no significant difference in the bladder/rectum D 2cm 3/D 0.2cm 3. Since the DIR group achieves satisfactory volume matching of greater than 0.8 with DSC analysis, it can yield acceptable results for clinical application between HT IMRT and HDR BT for cervical cancer.

Research progress on total skin irradiation using helical tomotherapy / 中华放射肿瘤学杂志

Cutaneous T-cell lymphomas are a relatively rare group of mature T-cell lymphomas mainly manifesting in the skin, and its common subtype is mycosis fungoides. Total skin electron irradiation is one of the important conventional treatment methods, but there are many disadvantages, such as uneven dose distribution, poor position repetition, and long treatment time, which affect the clinical efficacy and patient prognosis. With the emergence and gradual popularization of helical tomotherapy in recent years, more and more medical institutions are gradually expanding their applications in total skin irradiation due to their ability to treat ultra-long targets and achieve dose-sculpted distribution, aiming to further explore its good or bad, and confirm whether it can replace the traditional total skin electron irradiation. In this article, research progress on total skin irradiation using helical tomotherapy was reviewed, the development of treatment technology, clinical efficacy and current concerns and controversies were illustrated.

Dosimetric study of helical tomotherapy and volumetric modulated arc therapy simultaneous integrated boost for patients receiving breast-conserving surgery of left breast / 国际肿瘤学杂志

Objective:To compare the dosimetric characteristics of helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) after left breast conserving surgery.Methods:Twenty-four patients with left breast cancer after breast-conserving surgery who were admitted to the Department of Radiation Oncology of Tumor Hospital of Yunnan Province from May 2016 to May 2019 were selected. The HT plan and the VMAT plan were designed for the same patient. The target dose and the dose volume parameters of organs at risk were compared and analyzed in the two radiotherapy plans.Results:There were significant differences in the D 2% [(59.68±0.46) Gy vs. (60.06±0.20) Gy, t=-4.229, P<0.001], D 98% [(57.46±0.44) Gy vs. (57.20±0.07) Gy, t=2.912, P<0.001], conformity index (CI) (0.80±0.05 vs. 0.76±0.04, t=4.079, P<0.001) and homogeneity index (HI) (0.04±0.01 vs. 0.05±0.00, t=-5.505, P<0.001) of the planning gross tumor volume (PGTV) between the HT and VMAT plans. However, there was no significant difference in the D 50% [(58.77±0.46) Gy vs. (58.75±0.11) Gy, t=0.179, P=0.859]. There were significant differences in the D 50% [(51.99±0.39) Gy vs. (52.39±0.36) Gy, t=-5.278, P<0.001], D 98% [(49.46±0.29) Gy vs. (48.35±0.46) Gy, t=9.538, P<0.001] and HI (0.19±0.01 vs. 0.21±0.01, t=-7.538, P<0.001) of the planned target volume (PTV) between the two plans. However, there were no significant differences in the D 2% [(59.13±0.64) Gy vs. (59.09±0.46) Gy, t=0.511, P=0.614] and CI (0.83±0.04 vs. 0.82±0.04, t=1.637, P=0.115). In terms of organs at risk, there were significant differences in the V 5 [(57.90±1.42)% vs. (52.40±5.74)%, t=4.812, P<0.001], V 20 [(22.40±2.17)% vs. (18.40±3.16)%, t=5.573, P<0.001] and D mean [(12.71±0.55) Gy vs. (11.46±1.26) Gy, t=4.963, P<0.001] of left lung, D mean of right lung [(3.42±0.27) Gy vs. (2.49±0.24) Gy, t=13.310, P<0.001], D mean of right breast [(4.41±0.50) Gy vs. (3.12±0.65) Gy, t=10.326, P<0.001], V 30 [(0.55±0.37)% vs. (1.24±1.11)%, t=-4.020, P=0.001] and D mean of heart [(4.68±0.62) Gy vs. (3.83±0.88) Gy, t=7.335, P<0.001], D mean of left atrium [(2.53±0.31) Gy vs. (2.16±0.28) Gy, t=5.488, P<0.001], D mean of right atrium [(2.77±0.43) Gy vs. (2.20±0.30) Gy, t=7.103, P<0.001], D mean of right ventricle [(5.10±0.72) Gy vs. (3.72±0.94) Gy, t=9.802, P<0.001] and D 2% of spinal cord [(14.79±2.73) Gy vs. (5.42±2.23) Gy, t=14.788, P<0.001] between HT and VMAT plans. There was no significant difference in the D mean of left ventricle [(5.10±1.19) Gy vs. (4.80±1.54) Gy, t=1.250, P=0.224]. Conclusion:Both the HT plan and the VMAT plan can meet the treatment requirements. The HT plan can provide better target area conformity and dose uniformity. The VMAT plan has more advantages in terms of organs at risk. The HT plan shows an advantage only in exposure to high-dose area.

Study on setup errors for different body carcinoma radiotherapy with image guidance in TOMO-HD / 中国辐射卫生

Objective The literature study the setup errors of head and neck, thoracic, abdominal and pelvic tumors by megavoltage fan-beam CT based image guidance in TOMO-HD to provide the margin enlarging from clinic target volume (CTV) to planning target volume (PTV) in treatment planning system of TOMO-HD. Methods 103 patients with head and neck (30 patients), thoracic (42 patients), abdominal and pelvic (31 patients) carcinoma were enrolled. Megavoltage fan-beam CT based image guidance in tomotherapy-HD was used to acquire CT scan before every treatment. The left-right (X), superior-inferior (Y), anterior-posterior (Z) and rotation (Fy) setup errors of patients can be obtained from the tomography image automatically restructured by the system. Calculating the systematic error and the random error in the three dimensions and check whether the setup data accord with the normal distribution or not, then acquire the data expand in the three directions. Results According to 2593 fan-beam CT scans, the shift errors (µ ± s) in X, Y, Z and Fy (rotation) of three study group were [(−0.31 ± 2.16) mm、(1.09 ± 3.56) mm、(2.36 ± 2.27) mm, (0.29 ± 0.96)°] (head and neck tumor), [(−0.98 ± 2.95) mm、(0.45 ± 6.86) mm、(3.79 ± 2.47) mm, (0.18 ± 0.60)°] (thoracic cancer) and [(−0.86 ± 2.85) mm、(−1.59 ± 6.91) mm、(5.77 ± 2.40) mm, (0.20 ± 0.68)°](abdominal and pelvic carcinoma). The systematic errors (∑) and random errors (σ) in X, Y, Z dimensions of patients with head and neck, thoracic, abdominal and pelvic tumors were (1.06 mm and 1.84 mm), (1.93 mm and 3.43 mm), (2.41 mm and 2.71 mm), (1.10 mm and 2.56 mm), (3.79 mm and 5.46 mm), (1.38 mm and 1.99 mm) and (1.39 mm and 0.87 mm), (4.98 mm and 5.69 mm), (1.19 mm and 2.05 mm), respectively. Conclusion It is recommended as a reference for image guidance in TOMO-HD according to the frequency distribution of setup errors, for patients with head and neck, chest and abdominal and pelvic tumors, the maximum range of motion in three dimensions are (5.00, 5.00, 5.00) mm, (6.63, 17.25, 16.00) mm and (6.49, 16.24, 13.60) mm.

Preliminary observation of new immobilization for total skin irradiation with helical tomotherapy / 中华放射肿瘤学杂志

Objective:To preliminarily observe the feasibility of different immobilization techniques for total skin irradiation (TSI) using helical tomotherapy.Methods:Three eczema scrophuloderma patients treated with TSI in Sun Yat-sen University Cancer Center were immobilized with low-temperature thermoplastic in a prone position, diving suit combined with negative pressure vacuum bag in a supine position, low-temperature thermoplastic combined with vacuum bag in a supine position, respectively. Different immobilization effects were observed. The conformity index (CI) of the target area, heterogeneity index (HI) of the target area, and the mean dose (D mean) of the target area were calculated. Results:Three immobilization methods could achieve satisfactory immobilization effects, and all the dosimetric parameters of radiation treatment plans met the clinical requirements. The average set-up errors in the left and right, head and foot, and abdomen and back directions of three patients were (0.26±3.40) mm, (-2.63±4.63) mm and (6.13±4.86) mm, respectively. The CI, HI andD mean were0.56±0.09, 1.186±0.059 and (2586.56±63.28) cGy. Conclusions:Low-temperature thermoplastic or diving suits can be combined with vacuum bags for immobilization in TSI. The epidermal dose can be increased with bolus through the dose-building effect, which can provide a safe and reliable method for TSI in helical tomotherapy.

Dosimetric comparison between TomoDirect and Helical Tomotherapy in total body irradiation / 中华放射医学与防护杂志

Objective@#To investigate the dosimetric differences between TomoDirect (TD) and Helical Tomotherapy (HT) in total body irradiation (TBI), as well to evaluate the plan quality and delivery efficiency of TD.@*Methods@#Eight patients with acute leukemia at an average height of about 120 cm who had undergone TBI in the first affiliated hospital of Zhengzhou university were retrospectively reviewed and replanned with the TD and HT techniques for dosimetric comparison. Identical planning parameters were configured for both techniques except that TD plans were designed with 2-12 equally spaced odd number fields and with an initial angle of 180 or 0 degree. Dosimetric differences in mean dose of plan target volume (PTVDmean), homogeneity index (HI), dose of organs at risk (OARs), as well as delivery time were compared between the TD and HT plans.@*Results@#The TD plans with 9 fields or more had similar PTVDmeanand HI compared with HT plans, while TD plans with less than 9 fields had a significant different PTVDmean(t=-3.12, -5.41, -20.33, -4.56, -7.22, -11.27, P<0.05) and HI (t=-2.94, -5.18, -15.66, -4.31, -5.51, - 9.13, P<0.05) compared with those of HT. In terms of OARs, the TD plans with 7 fields or more had no significant dosimetric differences in the mean dose of left and right lung compared with the HT plans. The TD plans with 3 fields had significant different maximum dose in the left lens plan risk volume(PRV) (2.14±0.60) Gy and the right lens PRV (3.05±0.10) Gy (t=0.77, 0.63, P<0.05) compared with the HT plans. No significant difference in delivery time was observed. The initial angle of the TD plans had no effects on PTVDmean, HI, OAR dosimetry and delivery time.@*Conclusions@#The TD plans with 9 fields or more can achieve similar plan quality in terms of target coverage, OAR sparing and delivery time, but have an advantage in the maximum dose to lens PRV compared with the HT plans.

Study of clinical application of a novel immobilization system in total marrow irradiation / 中华放射肿瘤学杂志

Objective To evaluate the clinical application value of a novel immobilization system in total marrow irradiation ( TMI) with MVCT image. Methods From 2016 to 2017, a retrospective analysis of the setup errors of 22 patients receiving TMI in two groups ( twelve patients were immobilized with the novel immobilization system in group 1, ten patients were immobilized with the combinatorial immobilization devices in group 2) was performed in this study on Zhongnan Hospital of Wuhan University. Two-sample t-test was used to analyze the differences of setup errors and the consistency of setup between two groups. Results In group 1, the setup errors on left-right, superior-inferior, anterior-posterior and rotation directions were ( 1.06±0.79) , ( 1.34±0.66) , ( 2.45±1.48) mm and ( 0.63°±0.65°) for the head and neck position, ( 1.58±1.13) , ( 2.38±1.99) , ( 2.05± 1.68) mm and ( 0.31°± 0.32°) for the chest position, ( 1.67± 1.24) , ( 3.88±2.20) , ( 1.96± 1.32) mm and ( 0.48°± 0.53°) for the pelvis position, and ( 0.95± 0.73) , ( 1.99± 1.35) , ( 3.66±2.13) mm and ( 0.24°±0.31°) for the lower limb, respectively. In group 2, the setup errors were ( 2.59±2.58) , ( 3.28±1.85) , ( 3.71±2.43) mm and ( 1.15°±1.18°) for the head and neck position, ( 4.38±3.69) , ( 5.64±3.78) , ( 2.72± 1.91) mm and ( 1.55°± 0.86°) for the chest position, ( 4.14± 2.97) , ( 6.97±3.68) , ( 2.21±2.26) mm and ( 1.23°±0.74°) for the pelvis position, ( 2.28± 1.15) , ( 5.97± 3.00) , ( 3.44±1.93) mm and ( 1.09°±0.94°) for the lower limb, respectively. The setup errors significantly differed between two groups on the left-right, superior-inferior and rotation directions for all positions ( all P<0.05) . The setup consistency significantly differed between two groups on the left-right, superior-inferior and rotation directions for the chest and pelvis positions ( all P<0.05) . Conclusion The novel immobilization system can significantly improve the setup accuracy and setup consistency, and enhance the precision of treatment for patients.

Comparison of acute adverse reactions between helical tomotherapy and intensity-modulated radiation therapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective To comparatively analyze the acute adverse reactions of helical tomotherapy ( HT) and intensity-modulated radiation therapy ( IMRT) for nasopharyngeal carcinoma ( NPC) . Methods A total of 100 NPC patients treated with radiotherapy were selected and divided into the HT group ( n=50) and IMRT group ( n=50) . All patients were treated with concurrent chemoradiotherapy. The prescription dose of radiotherapy was DT 68.2-73.8 Gy/30-34F. The severity of acute adverse reactions of skin, oral mucosa, salivary glands and esophagus was evaluated with the established RTOG criteria. The differences between two groups were evaluated by paired t-test. Results The dose of organs at risk ( OARs) in the HT group was significantly lower than that in the IMRT group ( P<0.05) , whereas the dose of target area of PTVnx, PTVnd ( left) and PTVnd ( right) did not significantly differ between two groups ( all P>0.05) . In the HT group, the incidence rate of grade 0-3 acute adverse reactions in the skin, oral mucosa, salivary glands and esophagus were ( 14%, 68%, 18%, 0%) , ( 10%, 54%, 36%, 0%) , ( 0%, 74%, 26%, 0%) and ( 10%, 60%, 28%, 2%) , respectively. In the IMRT group, the corresponding results were ( 0%, 52%, 48%, 0%) , ( 0%, 58%, 42%, 0%) , ( 0%, 28%, 72%, 0%) and ( 0, 40%, 60%, 0%) , respectively. The severity of acute adverse reactions of skin, salivary glands and esophagus in the HT group was slighter than those in the IMRT group ( all P<0.05) , the acute adverse reactions in the oral mucosa were similar between two groups ( P>0.05) . In the HT group, the onset time of acute adverse reactions in the skin was later than that in the IMRT group ( P<0.05) , and the onset time of other adverse reactions was similar between two groups ( all P>0.05) . Conclusions Both HT and IMRT can meet the requirements of the dose distribution in the target area for NPC, whereas HT is superior to IMRT in terms of the protection of OARs protection, the severity and onset time of acute adverse reactions.

Dosimetric comparison between TomoDirect and Helical Tomotherapy in total body irradiation / 中华放射医学与防护杂志

Objective To investigate the dosimetric differences between TomoDirect ( TD) and Helical Tomotherapy ( HT ) in total body irradiation ( TBI ) , as well to evaluate the plan quality and delivery efficiency of TD. Methods Eight patients with acute leukemia at an average height of about 120 cm who had undergone TBI in the first affiliated hospital of Zhengzhou university were retrospectively reviewed and replanned with the TD and HT techniques for dosimetric comparison. Identical planning parameters were configured for both techniques except that TD plans were designed with 2-12 equally spaced odd number fields and with an initial angle of 180 or 0 degree. Dosimetric differences in mean dose of plan target volume ( PTVDmean ) , homogeneity index ( HI) , dose of organs at risk ( OARs) , as well as delivery time were compared between the TD and HT plans. Results The TD plans with 9 fields or more had similar PTVDmean and HI compared with HT plans, while TD plans with less than 9 fields had a significant different PTVDmean(t=-3. 12, -5. 41, -20. 33, -4. 56, -7. 22, -11. 27, P<0. 05) and HI ( t=-2. 94, -5. 18,-15. 66,-4. 31,-5. 51,- 9. 13, P<0. 05) compared with those of HT. In terms of OARs, the TD plans with 7 fields or more had no significant dosimetric differences in the mean dose of left and right lung compared with the HT plans. The TD plans with 3 fields had significant different maximum dose in the left lens plan risk volume(PRV) (2.14±0.60) Gy and the right lens PRV (3.05±0.10) Gy (t=0.77, 0.63, P<0.05) compared with the HT plans. No significant difference in delivery time was observed. The initial angle of the TD plans had no effects on PTVDmean , HI, OAR dosimetry and delivery time. Conclusions The TD plans with 9 fields or more can achieve similar plan quality in terms of target coverage, OAR sparing and delivery time, but have an advantage in the maximum dose to lens PRV compared with the HT plans.

Analysis of failure of helical tomotherapy multi-leaf collimator system / 中华放射肿瘤学杂志

Objective To analyze the failure and processing methods of helical tomotherapy multileaf collimator (MLC) and summarize relevant maintenance experience,aiming to accurately identify the faulty parts,shorten the downtime and enhance the work time.Methods The failure data of the helical tomotherapy MLC system in the past 48 months were analyzed to identify the common faulty parts,causes and processing methods.Results During the previous 48 months,the MLC failure occurred for 20 times,11 times for air compressor failure,4 times for position verification board failure,twice for leaf driver failure,twice for cushion valve failure and once for the slip of leaf position verification rod.The MLC failure was significantly correlated with the humidity of high-pressure gas.The work time of machine exerted significant effect upon the service time of MLC parts.Conclusions The structure of the helical tomotherapy MLC system is complex.The high-intensity work increases the failure rate.The humidity of high-pressure gas affects the normal operation of the MLC equipment.The faulty parts can be identified,the downtime can be reduced and the work time can be enhanced by summarizing the experience of MLC maintenance.

Commissioning of dynamic jaw delivery in tomotherapy / 中华放射肿瘤学杂志

Objective To evaluate the dosimetric penumbra and delivery accuracy of dynamic jaw delivery in tomotberapy.Methods The jaw positioning hardware and the beam model were updated.Mechanical alignments were verified after the upgrade of the jaw positioning hardware.PDDs and beam profiles were measured by a two-dimensional water tank and compared with the new beam model.Dose penumbras in the longitudinal direction were compared between the dynamic and fixed jaw plans for different field width.Delivery accuracy was evaluated by point dose measurements with A1SL chamber and gamma analysis on the dose distribution measured by ArcCheck detector array.Results Mechanical alignments were in tolerance and beam characteristics were tuned to match the dynamic jaw beam model.Differences in the field width between the measured results and reference data were ＜ 0.3％ for both symmetric and asymmetric profiles in the longitudinal direction.The dose penumbra in dynamic jaw delivery was reduced from 17.92 mm to 7.51 mm for 2.5 cm jaw,and from 33.73 mm to 6.97 mm for 5.0 cm jaw,close to the penumbra of the traditional 1.0 cm jaw.IMRT verification of clinical cases was performed by A1SL ion chamber and ArcCheck detector array.The mean point dose difference was 0.33％ ± 0.73％ between the calculated and meassured data.Gamma analysis of dose distributions revealed that approximately 99.8％ of the points satisfied the gamma criteria of 3％ dose difference and 3 mm distance-to-agreement and the mean passing rates remained 97.9％ even with tightest criteria of 2％/2 mm,and 100.0％ with the criteria of 4％/4 mm,respectively.Conclusions Dosimetric penumbra in the longitudinal direction is significantly improved by the dynamic jaw delivery.Both the mechanical alignment and treatment delivery are qualified,suggesting that this new treatment is accurate and reliable.

Characteristics and clinical application of the TomoDose diode array for quality control of Tomotherapy / 中华放射肿瘤学杂志

Objective To evaluate the dosimetric characteristics of the TomoDose diode and its application in detecting the couch velocity and assessing the beam Profile stability for convenient and efficient quality control of Tomotherapy.Methods Fundamental properties of the TomoDose detector,such as dose linearity,dose per pulse dependence,directional dependence and field size dependence were tested by the water-equivalent phantom and the results were statistically compared with those measured by the ion-chamber (0.057 cm3,A 1SL).Five different couch velocities with a time interval of 0.0005 s were designed to test the sensitivity of TomoDose for detecting the couch velocity,and then the clinical data of 7 patients with different couch velocities were selected to verify the test accuracy.The beam profile of three different jaws of 1.0,2.5 and 5.0 cm were measured using TomoDose with water-equivalent phantom in the x and y directions under the same conditions as water tank with an underwater depth of 15,50,100,150 and 200 mm,respectively.The Profile data obtained by water tank and TomoDose were evaluated using the Gamma (γ) evaluation method with the 2％/1 mm criterion.Results The dose linearity of the TomoDose and ion chamber was in a linear pattern within the beam-on-time ≤ 30 s.The difference between the TomoDose and ion chamber was less than 2％ for the dose per pulse dependence,and the response trends of them were consistent.TomoDose showed angular response dependence with a maximum difference of 2.53％ for the gantry angle of ±60°.For the field size dependence,the response difference between the TomoDose and ion chamber was increased with the decreasing field size when the Jaw was 5.0 cm,and the maximum deviation was 0.78％ when the field size was 5.0 cm×2.5 cm.TomoDose could detect the couch distance error of 0.5 mm,and determine the couch velocity deviation of＜ 0.6％.For the Profile stability testing:In the x direction,there was always γ＜1 at the underwater depth of 15 mm for all values of Jaw;when the underwater depth was not 15 mm,there was always γ＜ 1 in the main beam region (off-axis distance＜ 200 mm),whereas in the penumbra region (off-axis distance＞ 200 mm),the value of γ was larger and even with γ＞ l.In the y direction,all comparison results of Profile under three field width demonstrated that γ index was larger on the edge of beam,whereas γ＜1 was found in all cases.Conclusions TomoDose is suitable f or the quality control of Tomotherapy,which can accurately measure the couch velocity,precisely monitor the stability of beam Profile of Tomotherapy and complete the quality control process in a convenient and efficient manner.

Application of dynamic jaw technique in helical tomotherapy for mid-esophageal carcinoma / 中华放射医学与防护杂志

Objective To evaluate the feasibility of replacing the fixed jaw 2.5 cm mode with dynamic jaw 5.0 cm for mid-esophageal cancer after the upgrade of helical tomotherapy (TOMO).Methods A total of 10 patients with locally advanced esophageal cancer were planned with radical intent using 2.5 cm fixed jaw (FJ2.5),2.5 cm dynamic jaw (DJ2.5) and 5.0 cm dynamic jaw (DJ 5.0) modes respectively on TOMO.Dose conformity index (CI),dose homogeneity index (HI) and dose to OARs were analyzed to evaluate the plan quality.Treatment time and monitor units were used to assess efficiency.Results CI and HI met clinical requirement for all plans.D J5.0 plans showed significant improvement over FJ2.5 plans in terms of V5 and mean dose to lungs,the V5,V10 and mean dose to normal tissues (t =9.751,4.163,11.840,10.321,3.745,P＜0.05).DJ2.5 plans were superior to DJ5.0 plans in the aspects of the V30,V40 and mean dose to heart,the V20 and mean dose to normal tissues (-2.454,-3.275,-4.192,-6.435,-4.139,-6.431,P＜0.05).Compared with DJ2.5 plans,the V5,V20,V30 and mean dose to lungs,the V4 0and mean dose to heart,maximum dose to cord and cord PRV,the V5,V10,V20 and mean dose to normal tissues of FJ2.5 plans were worse (t=8.289,6.142,3.137,8.895,3.597,4.565,3.782,5.429,16.421,12.496,8.286,11.933,P＜0.05).The beam-on time of DJ5.0 plans was significantly reduced by 43.9％ and 42.8％ compared with FJ2.5 and DJ2.5 plans respectively,and the machine monitor unit was reduced by 42.8％ and 43.8％ respectively.Conclusions The dynamic jaw of 5.0 cm technique is recommended for treatment of mid-esophageal cancer for sake of plan quality and efficiency.It does not only shorten the treatment time and improve radiation efficiency compared with fixed and dynamic jaw of 2.5 cm technique,but also provides a dosimetric advantage in terms of lung and normal tissue sparing in comparison with fixed jaw of 2.5 cm.When only improving plan quality is concerned,the dynamic jaw of 2.5 cm technique is more recommendable.

Effect of body thickness on helical and direct treatment delivery modes: a phantom study / Journal of Rural Medicine

Objective: Chemoradiation therapy is among the standard treatments for cancer, which often causes a decrease in appetite and subsequent weight loss. When weight loss occurs during treatment, the external body contour changes from that indicated during initial planning, causing changes in dose distribution to the target tumor regions and organs at risk (OARs). This study aimed to examine the dose changes to both the target regions and OARs, based on the dose-volume histogram (DVH).Methods: We established a 60 mm-diameter planning target volume (PTV) and a 30 mm-diameter rectum region of interest (OAR), using a phantom; this was followed by a 50 Gy/25 fraction irradiation to the target region that was measured using a two-dimensional-array ion chamber device. The measurement was conducted by varying the bolus thickness from 0 to −25 mm, in 5 mm decrements. In addition, the maximum dose for both PTV and OAR were evaluated based on the DVH, created using the Adaptive software.Results: The gamma analysis showed that the pass rate was less than 95% when the bolus thickness was altered by −25 mm for the helical delivery mode and by −10 mm for the direct delivery mode, resulting in a dose error greater than 3%. Results of the DVH evaluation revealed that the maximum dose of PTV increased by 5.18% when the bolus thickness was −25 mm for helical delivery, whereas a 9.95% increase was noted for the direct delivery mode compared with the dose at the reference level of 0 mm bolus thickness.Discussion: Our results suggest that it is necessary to formulate a new treatment plan owing to increased dose error, if the body thickness decreases by more than 20 mm and 10 mm for the helical and direct delivery modes, respectively. The results also demonstrate that helical delivery is less affected by changes in body thickness than direct delivery.

Repair of clinac and helical tomotherapy "GAS"interlock fault / 中华放射肿瘤学杂志

In this paper, an effective method was proposed for rapid positioning and repair of medical Clinac and helical tomotherapy "GAS" interlock fault. The infrared refrigerant leakage detector was combined with soap bubbles for leakuseage detection. The sandpaper and file were utilized to gently grind the leakage point and the surrounding 5 mm-wide waveguide surface,and then the high-power electric soldering iron of 150 W was adopted to make up for the leakage. The leakage point was detected by rapid positioning, and no leakage was found in the waveguide after 12 years of use. This approach can significantly reduce the difficulty in the repair of the Clinac and helical tomotherapy"GAS" interlock fault.

Effect of helical tomotherapy megavoltage CT under different acquisition pitch and registration conditions on the accuracy of radiotherapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

Objective To evaluate the effect of helical tomotherapy (HT) megavoltage CT (MVCT) under different acquisition pitch and registration conditions upon the accuracy of radiotherapy for used nasopharyngeal carcinoma,aiming to provide reference for image-guided radiotherapy (IGRT) for nasopharyngeal carcinoma.Methods MVCT scans were performed on an anthropomorphic head& neck phantom which was simulated the positioning errors in the x,y and z direction.The obtained images were registered with the planning CT images.Acquisition pitch was set as the coarse,normal and fine modes.Registration conditions were set as bone registration,bone and soft tissue registration and full-image registration.Registration accuracy was determined by comparing the measured value with the preset value.The accuracy of radiotherapy under different acquisition pitch and registration conditions was statistically compared.Results The 3D errors of bone,bone and soft tissue and full-image registration under different acquisition pitch (coarse,normal and fine) were (1.51±0.47,1.54±0.35,1.81±0.53) mm and (1.41± 0.37,1.53±0.36,1.56±0.39) mm and (1.51±0.27,1.57±0.32,1.73±0.33) mm,respectively.The bone registration yielded the highest accuracy (P＜0.05).When the registration condition was set as bone registration,the accuracy of three acquisition pitch did not significantly differ (all P＞0.05).The fine mode of acquisition pitch possessed the highest stability,whereas required the longest time.Conclusion The acquisition pitch and registration conditions should be selected during HT MVCT based on the clinical requirement of each patient with nasopharyngeal carcinoma.

Clinical study of total marrow and lymphatic irradiation in children using helical tomotherapy / 中华放射肿瘤学杂志

Objective To evaluate the feasibility of total marrow and lymphatic irradiation (TMLI)with helical tomotherapy as a conditioning regimen before hematopoietic stem cell transplantation (HSCT).Methods Seven children with acute lymphoblastic leukemia and aplastic anemia were recruited as study subjects.The median age was 7 years old.The prescribed dose was 12 Gy/6 fractions twice daily.The exposure dose of the target and the organs at risk between helical helical tomotherapy-based TMLI regimen and total body irradiation (TBI) regimen were statistically compared,and acute toxicity grading was performed for all patients.Results Compared with the TBI regimen,the average exposure dose reduction for organs at risk after the TMLI regimen was ranged from 4.2％ to 40.6％.The average exposure dose reduction for the kidney was the largest among all organs.The acute toxicities experienced by all patients were graded and recorded including 2 cases of nausea,5 cases of vomiting,1 case of anorexia,1 case of eryhema,3 cases of diarrhea,and 1 case of oral mucositis.Only grade 1-2 toxicities were observed,and no grade 3-4 toxicities occurred.Conclusions The findings in this study confirm the feasibility of helical helical tomotherapy-based TMLI regimen.Compared with the TBI regimen,the mean duration of treatment for the TMLI regimen with an equivalent dose is not increased.The exposure dose experienced by organs at risk is reduced and the predicted incidence rate is decreased when the TMLI regimen is employed,which provides a myeloablative pretreatment strategy.However,the long-term toxicity of TMLI regime remains to be evaluated by clinical trials.